INTEL CORPORATION
                  Chandler, Arizona
                     Prepared by
Gary J. Mihlan, Russell K. Smith and Leslie J. Ungers
                Columbus Laboratories
                   505 King Avenue
                Columbus, Ohio  43201
               Report No.  115-lla
                     May 31,  1983
         U.S. Environmental Protection Agency
     Industrial Environmental Research Laboratory
               Cincinnati, Ohio  45268
National Institute for Occupational Safety and Health
    Division of Physical Sciences and Engineering
        Engineering Control Technology Branch
                4676 Columbia Parkway
               Cincinnati, Ohio  45226

PLANT SURVEYED:  Intel Corporation
                 5000 W. Williams Field Rd.
                 Chandler, Arizona  85224

SIC CODE:  3674

SURVEY DATE:  August 12, 1981

SURVEY CONDUCTED BY:  Mr.  Gary J. Mihlan,  Battelle-Columbus Laboratories
                      Dr.  Ralph  I. Mitchell, Battelle-Colur/ous Laboratories
                      Mr.  Russell K.  Smith,  Battelle-Columbus Laboratories
                      Mr.  Leslie J. Ungers,  PEDCo Environmental
                      Mr.  James  H. Jones,  National  Institute for Occupational
                         Safety and Health
                      Mr.  Robert Hartley,  U.S. Environmental Protection Agency
                      Mr.  Eugene Harris, U.S. Environmental Protection Agency


       Mr. Edward  J. Sawicki,  Corporate Safety Manager
       Mr. Ed Boleky, Plant Manager
       Mr. Jerry O'Neal, Senior  Facilities  Engineer
       Mr. Bill Taylor,  Safety Engineer
       Mr. Steve Kopp,  Site Safety/Security Manager


       Mr. Steve Schuster; Safety Committee Chairman

                              TABLE OF CONTENTS


1.0  ABSTRACT	     1

2.0  INTRODUCTION	     3


     3.1.  General	     4
     3.2.  Chemical Storage	     4
     3.3.  Gas Handling System	     4
     3.4.  Monitoring System 	     5



     5.1.  Industrial Hygiene	     9
     5.2.  Education and Training	    11
     5.3.  Respirators and Other Personal Protective Equipment  	    11
     5.4.  Medical	    12
     5.5.  Housekeeping	    12



     7.1.  Chemical Vapor Deposition 	    14

           7.1.1.  Engineering Controls	    16
           7.1.2.  Monitoring	    17
           7.1.3.  Personal Protective Equipment 	    17
           7.1.4.  Work Practices	    17

     7.2.  Thermal Oxidation	    17

           7.2.1.  Engineering Controls	    18
           7.2.2.  Monitoring	    18
           7.2.3.  Personal Protective Equipment 	    13
           7.2.4.  Work Practices	    18

     7.3.  Doping and Hydrogen Alloying	    18

           7.3.1.  Engineering Controls	    21
           7.3.2.  Monitoring:  	    22

                         TABLE OF CONTENTS

      7.3.3.  Personal Protective Equipment	     23
      7.3.4.  Work Practices	     23

7.4.  Wet Chemical Cleaning Processes	     24
           7.4.1.  Engineering Controls 	
           7.4.2.  Monitoring  	     25
           7.4.3.  Personal Protective Equipment	     25
           7.4.4.  Work Practices	     25

     7.5.  Photolithography 	     25

           7.5.1.  Engineering Controls 	     27
           7.5.2.  Monitoring  	     28
           7.5.3.  Personal Protective Equipment	     28
           7.5.4.  Work Practices	     28

     7.6.  Plasma Etching	     28

           7.6.1.  Engineering Controls 	     30
           7.6.2.  Monitoring	     30
           7.6.3.  Personal Protective Equipment	     30
           7.6.4.  Work Practices	     30

     7.7.  DC Sputtering	     30

           7.7.1.  Engineering Controls 	     31
           7.7.2.  Monitoring  	     31
           7.7.3.  Personal Protective Equipnent	     31
           7.7.4.  Work Practices	     32

     7.8.  Electron-Beam Evaporation	     32

           7.8.1.  Engineering Controls 	     32
           7.8.2.  Monitoring  	     32
           7.8,3.  Personal Protective Equipment	     32
           7.8.4.  Work Practices	     32


9.0  REFERENCES	     35

                                1.0  ABSTRACT

          A preliminary control technology survey was conducted at Intel
Corporation, Chandler, Arizona on August 12, 1981 by Battelle's Columbus
Laboratories, Columbus, Ohio.  The survey was conducted as part of a project
under a U.S. Environmental Protection Agency contract funded through an
Interagency Agreement with the National Institute for Occupational Safety and
Health.  Intel Corporation manufacturers n-channel metal oxide semiconductor
(N-MOS) integrated  circuits.  The Chandler facility opened in 1980 and is at
less than half production capacity.
          The process operations in the manufacture of integrated circuits at
Intel are contained within a Class 100 clean room.  Particulate control is
performed by filtration of inlet air through HEPA filters.  Local air filtra-
tion is provided in the clean room by laminar flow benches with HEPA filtra-
tion.  Process equipment is generally located in the laminar flow benches.
          Process operations employed at Intel Corporation in MOS integrated
circuit manufacture include:  1) thermal oxidation of purchased pre-doped
silicon wafers, 2)  chemical vapor deposition of silicon nitride, polycrystal-
line silicon and silicon dioxide, 3) photolithographic processes for defining
circuit patterns, including wafer cleaning, photoresist coating, soft-bake,
projection mask alignment exposure, wafer developing, hard bake, plasma
etching, and photoresist stripping, 4) doping, including diffusion and ion
implantation, 5) hydrogen alloying, and 6) metalization, including electron
beam evaporation and  direct current (DC) sputtering.
          Engineering controls used at the facility vary by process operation.
General engineering controls include gas storage in ventilated cabinets or in
secured covered areas outside of the building, and gas lines of welded stain-
less steel construction or stainless steel in PVC lines.  Local exhaust
ventilation is provided for removing process gases by local exhaust take-offs
located at the source of the emission or by removal of process gases from
enclosed systems employing vacuum pumping systems.  Shielding and electrical
interlocks are used to control X-ray emissions from ion implantation.
          Environmental monitoring of toxic gases in the  clean room area  is
performed by a Miran's SOI multico-.ponent multistation system.  Hydrogen
monitoring is performed by a Bacharacrr" Model CDS50 and by an 1ST* sensor.

Process operations are generally automated and controlled by microprocessors.
The process sequences generally require that workers load and unload wafers
from the equipment.
          Intel Corporation has developed a comprehensive worker training
program.  Worker education and training is required of all new employees.  The
programs cover equipment  operations, safety practices, hazardous properties of
chemical agents and personal  protective equipment.  Plant safety program
personnel have the primary responsibility for worker health and safety.  A
detailed emergency response plan has been developed for the facility-
          Areas which warrant further study include:  1), review of ventilation
system design, testing, and maintenance, 2) review of data from environmental
monitoring systems, 3) documentation of work practices including worker
training programs, and A) evaluation of maintenance activities including
identification of hazards and controls employed during maintenance activities.

                              2.0  INTRODUCTION

          A preliminary survey was conducted as part of the control technology
assessment of the electronic components industry (SIC 3674).  The study was
conducted for U.S. Environmental Protection Agency contract through an Inter-
agency Agreement with the National Institute for Occupational Safety and
Health.  The preliminary survey was conducted to identify and evaluate the
control technology used to control emissions and work exposures.  The informa-
tion obtained from the preliminary survey will be used to select sites for the
detailed control technology assessment.
          The preliminary survey was conducted on August 12, 1981,  at Intel
Corporation, 5000 W. Williams Field Road, Chandler, Arizona.  The survey was
conducted by Battelle Columbus Laboratories with assistance from Mr. James
Jones, NIOSH.  Mr. Bob Hartley and Mr. Gene Harris, U.S. EPA/Industrial
Environmental Research Laboratory, Cincinnati, Ohio, accompanied the research
team as observers.
          The following individuals were contacted at Intel:
          1.  Mr. Edward J. Sawicki, Corporate Safety Manager
          2.  Mr. Ed Boleky, Plant Manager
          3.  Mr. Jerry O'Neal, Senior Facilities Engineer
          4.  Mr. Bill Taylor, Safety Engineer
          5.  Mr. Steve Xopp, Site Safety/Security Manager
          6.  Mr. Steve Schuster, Safety Committee Chairman
          The study protocol was provided to the corporate safety manager
prior to the preliminary survey.  An opening conference was held with plant
representatives.  The study objectives and methods were described.   A detailed
description of the health and safety programs at the plant was provided by the
plant staff.  The plant structural design and layout, process description,
unit operations, monitoring systems, gas handling systems, and chemical
storage facilities were reviewed.
          Following the opening conference a detailed tour of the facility was
conducted.   Production areas, gas and chemical storage areas, air handling
systems, waste management systems, and medical facilities at the plant were
reviewed. A closing conference was held following the survey.  All  information

provided by  the  plant  that  was  considered  confidential  was  identified  by  pla:
                             3.0   PLANT DESCRIPTION

3.1.  General
          The  plant  is  an  integrated  circuit  fabrication facility located in a
two-building  complex.   It  consists  of  a  150,000 sq. ft. building, with a
34,000 sq.  ft.  Class  100 clean  room,  of  tilt-up construction, Type 3N,
(Uniform Building  Code).   The plant was  opened in  1980 and is at less than
half  production capacity.   The  plant  produces N-MOS type integrated circuits.
          Approximately 300 people  are employed on three shifts at the plant
as  follows:   194 first  shift, 84  second  shift, and 22 third shift.

3.2.  Chemical  Storage

          Chemicals  are stored  in a chemical  warehouse and transported to the
facility via  common  carrier.  Chemicals  stored at  the plant are segregated as
acids and solvents (organics).  Storage  roons are  approximately 6 inches below
the surrounding  floor level.  Separate storage rooms are used for acids and
sol'/ents.   Acids are  received as  boxed shipments and stored on wooden pallets.
Chemical spill  kits  are available in  the  storage rooms.
          Solvents are  received as  boxed  shipments or drums.  The solvent
storage room  is mechanically ventilated  with  ventilation take-offs located at
floor level.  A  trench  is  located _in  the  storage room.  Drums are placed on
the grating above  the trench, grounded,  and connected to an automatic pumping

3.3.  Gas Handling System

          Production gases  are  provided  either in  cylinders or as bulk
shipments.   Gas cylinders  are stored  outside  of the facility in a c;--erec
secured area.   Cylinders are segregated  into  four  major categories:

flammable, toxic, pyrophoric, and cxidizer.  Most cylinders have excess flow-
control valves to automatically close the line when gas flow exceeds a preset
flow limit.  A purge gas cylinder is located beside the process gas cylinder.
Control assemblies for gas purging are mounted above the gas cylinders.
          Bulk storage tanks are used for nitrogen and oxygen,  and are located
outside of the building.  Gases supplied by cylinders include arsine,  Freon®,
phosphine, hydrogen chloride, silane, dichlorosilane, boron trifluoride,  and
ammonia.  Hydrogen chloride, hydrogen, and dichlorosilane are stored in
ventilated cabinets located  indoors.  Gas control systems have  excess  flow
valves.   Cabinets have local exhaust ventilation and are located in fenced,
locked enclosures.  Gases are piped to process operations using welded
stainless steel  lines.  Hydrogen is supplied to process operations in  a
double-line  of welded stainless steel tubing enclosed in PVC.  The interstice
contains  nitrogen, which is  purged toward a combustible gas monitor.   Process
gas for ion  implantation is  supplied in lecture bottles located in a ven-
tilated gas  storage cabinet  in the ion implantation unit.
          Natural gas is piped through a seismic protection valve into the
plant.  Cylinder gases are purchased in size K and T bottles and piped into
the building.

3.4.  Monitoring Systems

          Two types of monitors are used for monitoring gases.   Hydrogen  is
monitored by both a Bacharach® Model CD 850 and by an 1ST6 sensor.  The
Bacharach® sensor is used to monitor lines for explosive concentrations.   The
1ST® unit is employed near the ion implantation units.  The alarm from this
system (10 ppci) will identify a toxic gas leak.  This is a combustible mixture
alarm that will activate for combustible compounds, such as hydrogen and
alcohols.  The Bacharach® sensor and the 1ST® sensor have been in use  since
early 1981.
          A second toxic gas monitoring system is the Mi ran® 801.  This system
is a multistation, inulticomponent monitoring system.  The system is used  to
monitor for arsine, phosphine, hydrogen chloride, nitrogen dioxide, hydrogen
fluoride, xylene, n-butyl acetate, and acetic acid.  Isopropanol, water,  and
carbon monoxide are interference co-pounds wnich are also monitored.  Each

line is prepurged before it is sampled so that the gas analyzed is represen-
tative of that present at the sampling location during the period analyzed.
          Local exhaust ventilation is monitored through visual alarms.
Velocity, temperature, humidity, and pressure are measured at key points, such
as ventilation ducts and upstream of the scrubber.  Breathing zone monitoring
of workers for arsenic and organics is also performed.
          Alnor velometers are used to measure ventilation flow rates on a
periodic basis.  The ventilation system power is backed up for full flow-
capability on the emergency power system.
                           4.0  PROCESS DESCRIPTION

          The plant purchases pre-doped p- and n-type silicon wafers.  Photo-
masks used for defining circuit patterns in the wafer are produced for the
plant by another manufacturer.  Process operations performed at the facility
include thermal oxidation, chemical vapor deposition (silicon nitride,  poly-
crystalline silicon, and silicon dioxide), photolithography (wafer cleaning,
photoresist coating, soft-bake, wafer exposure, develop,  hard bake, etching,
and photoresist stripping), doping  (diffusion, ion implantation,  and hydrogen
alloying), and metallization  (electron beam evaporation and DC sputtering).
          Several process operations utilize similar types of equipment for
different process steps.  Thermal oxidation, silicon nitride and  polycrystal-
line silicon deposition, hydrogen alloying, and doping (diffusion) are
performed in direct digital control furnaces.  The processes vary in the types
of source gases used, furnace temperatures, processing tine, and  sequencing of
          Similar process steps may be performed with a variety of process
equipment.  Chemical vapor deposition is performed in a direct digital control
furnace and a continuous vapor phase system.  Plasma etching is performed ir.
both a planar etching system  and a  barrel or tunnel etching system.
          The production area is designed as a Class IOC clean room with
temperature and humidity controlled.  All operations, except electron bear
evaooration of gold, are performed  in the clean room.

          The purcnased wafers are loaded into quartz boats and placed in an
open end tube called an elephant.  The elephant is manually attached to the
direct digital control  (DDC) furnace.  The furance consists of a horizontal
quartz tube heated by electrical resistance.  One end of the tube has a ground
glass joint with a removable cap.
          The direct digital control furnace is operated by a microprocessor,
which controls gas flow, tube temperature, the rate of wafer loading, and
unloading and process time.  Once the elephant is attached to the furnace,  the
boats containing the wafers are automatically inserted into the furnace at  a
programmed rate.  Depending on the process step, the gases introduced into  the
furnace include oxygen  (for thermal dxidation), dichlorosilane and ammonia
(for silicon nitride deposition), silane  (for polycrystalline silicon deposi-
tion), phosphorous oxychloride (for doping or junction formation), and hydro-
gen  (for hydrogen alloying).  The DDC furnace is used to deposit a layer on
the wafer (silicon dioxide, polycrystalline silicon, or silicon nitride),  and
to promote diffusion of dopants into the wafer surface.   Those processes in
which a layer is deposited on the wafer surface by a chemical vapor are known
as chemical vapor deposition or CVD.  These CVD processes include silicon
nitride, polycrystalline silicon, and silicon dioxide deposition.  Silicon
dioxide is deposited in a vapor phase reactor with silane and oxygen.
          Wet chemical  processes are used at various steps in integrated
circuit fabrication.  Sulfuric acid and hydrogen peroxide are used to clean
wafers by iinoersion in  the heated mixture.  The immersion baths are located in
laminar flow hoods in molded plastic benches.  Local exhaust ventilation of
the  baths is provided by slots located at the top of the bath and at the rear
of the bench.  Hydrofluoric acid is used  to remove silicon dioxide.
          The first step in the photolithographic process is wafer prepara-
tion.  The photoresist  layer, consisting  of an organic polymer in a xylene  or
cellosolve acetate solvent, is spun onto  the wafer and soft-baked in an
electrical resistance heated oven.  The soft-baked wafer is loaded into wafer
carriers and transferred to the projection mask aligper for pattern defini-
tion.  The wafer is automatically removed from the carrier and counted against
a photomask.  The circuit pattern is transferred to the wafer by  exposure of
the wafer to ultraviolet light,  The exposed wafer is returned to  the carrier
and the process is repealed for the remaining wafers.  The treated wafer is

then submerged in a wet chemical bach to remove the photoresist.  Depending or.
the type of photoresist used (positive or negative) the layer removed is
either the unexposed or exposed area.  The exposed wafers are treated in a
post- or hard-bake oven.
          A dopant may then be diffused into the wafer surface.   Dopants are
introduced into the substrate by gas diffusion or ion implantation,  or as a
solid dopant, which is then heat treated in a DDC furnace.   Diffusion is
performed in the direct digital control furnaces.   Wafers are inserted,  and
heated, and a gas mixture of nitrogen and phosphorous oxychloride is intro-
duced to the furnace.  Ion implantation uses a focused ion beam.  The ions are
generated by an electrical arc discharge in a vacuum system containing the
doping gas (phosphine, arsine, or boron trifluoride).   The ions  are  targeted
at the individual wafer and implanted into the substrate.  The ion implanta-
tion occurs under high vacuum conditions.
          The exposed underlying layer may then be etched using  plasma etching
systems.  Plasma etching is a dry chemical etching method using  a plasma gas
containing reactive ions which remove material from the wafer surface.  The
operation is performed under high vacuum conditions.   Wafers are loaded  into
the system, which is sealed and pumped to vacuum.   A plasma containing
reactive fluoride ions is created by passing a reactant gas through  a radio
frequency field created inside the sealed chamber.  Planar plasma etching and
barrel or tunnel reactor plasma etching systems are used at Intel.
          An aluminum layer, deposited on the wafer by DC sputtering under
high vacuum conditions, acts as a metallic connect.  Wafers are  loaded onto
platens and placed in a load chamber.  The load c'naaber is pumped to a vacuum
and the platens are automatically transferred to the sputtering  chamber.  The
sputtering chamber consists of a bell jar and DC sputtering source.   The bell
jar is lowered and a high vacuum seal is forced.  The aluminum is contained in
a target material, which is in the bell jar assembly.  The aluminum is
deposited on the wafer surface by removing surface molecules of  the netal from
the source target. ' This deposition is accomplished by the ionizing energy
supplied by a DC power source, which is applied to the target.  A gaseous glow
discharge is established between the anode (containing the wafers) and  the
target (containing the material to be deposited).   The alurinum atorr_3

sputtered  from the  target  to  the  wafer  surface.  After  deposition  of  the
metal,  the  photolithographic  sequence is  repeated  to  define  the  ratal  pattern.
Etching is  used to  remove  the exposed aluminum  and  establish  the contact
           The  last  step  in the fabrication  process  is the  deposition  of a gold
layer  on the wafer  backside.   This  layer  promotes  bonding  of  the integrated
circuit chip during packaging and is deposited  through  electron  beam  evapora-
tion.   The  wafers are  loaded  into the planetary.  The bell jar is  lowered and
the unit is pumped  to  a  high  vacuum.  Gold  is evaporated from a  target source
using  an electron-beam field  applied to the  gold source material.  High vacuum
conditions  (10~- torr) are created  with an  initial  rough pumping of the
bell jar using a mechanical roughing pump.   Lower pressures are obtained using
a  cryogenic or diffusion pump.  The diffusion pumps utilize a low  boiling
hydrocarbon fluid.   Molecules of  the hydrocarbon vapor  are heated  in the pump
bottom and  ejected  downward,  sweeping gas molecules from the  chamber.   A cryo-
genic  trap  is  used  to  remove  water  vapor  present in the chamber air.
           The  above steps  may be  repeated several  times to produce an inte-
grated circuit.   The differences  in electrical  properties of  the layers and
the'arrangement and sequence  of the layers  forms the  transistors,  capacitors,
resistors,  and conductors,  which  constitute  the integrated circuit.
                          5.0   DESCRIPTION OF PROGRAMS
5.1.  Industrial  Hvsiene
          The  plant  employs  a  full-time safety engineer.  An industrial
hygienist employed at  corporate headquarters is also available.  Consultants
are used as necessary  in  the areas of industrial hygiene, health physics,
medicine, and  toxicology.   Corporate staff were involved in the initial desig:
of the plant .
          The  work area is  monitored with personal and  area sampling methods.
A monitoring system  has been developed which samples workroom air iron; 24
remote locations with  analysis at a central location using the Mirar:'1' 801 for


the agents and interference compounds  listed in the discussion of monitoring
systems (Section 3.4).
          The results from area sampling are reported on computer printouts.
Analytical results are reported as 8-'nour, time weighted averages and peak
concentrations by location of sampling stations.  Sampling probes were located
based on results of  smoke tests.  A hydrogen monitoring system is also present
with sampling points  near areas of hydrogen use (e.g., hydrogen alloying
          Personal monitoring has been conducted at the plant for production
and maintenance workers.  Verbal and/or written results of personal monitoring
are provided to employees.  Monitoring records were available, but were not
reviewed during the  survey.  Personal  monitoring has been conducted for
numerous chemical agents, including arsenic.  Plant personnel indicated that
personal breathing zone samples of workers exposed to arsenic have not been
above 1 ug/nH (limit  of detection).  Monitoring of exposures to physical
agents, including X-rays, radio frequency radiation, and ultraviolet
radiation, has been  conducted.
          Local exhaust ventilation is monitored with Alnor® velometers.
In-house systems are  equipped with audible and visual alarums should a ventil-
ation failure occur.  Ventilation systems are backed up with emergency
          Standard operating procedures are defined for normal production and
maintenance operations.  Work practices are listed for all job classifica-
tions.  Chemical transport in-house is limited to individuals specifically
trained in chemical  handling.  Maintenance personnel are trained for specific
pieces  of equipment.  Written maintenance procedures are available.  Material
safety  data sheets are available for chemicals used at the facilility.
Detailed procedures  have been developed for chemical spills, confined area
entry,  chemical handling, earthquakes, electrical maintenance and lockout,
electrical safety, and gas cylinder storage.
          Emergency  response equipment is available at the facility.  A loss
control team has been established to respond to emergencies, to facilitate
plant evacuation, and to safely shut-down building services and utilities as
needed.   Written procedures for emergency response

           The facility has established s. radiation safety program, adrtini-
'stered  by a radiation safety officer.   The program requires controlled access
 to  high radiation areas.   Permissible levels of exposure are adapted from

 5.2.  Education and Training

           All new employees must complete a 20-hour new hire technical
 orientation.   The orientation includes sections on safety practices,  tools,
 equipment, and technology.  General facility safety practices  are  described.
 Personal protective equipment and emergency procedures  are provided.   Poten-
 tial  chemical and physical hazards in the plant,  the effects from  exposure  to
 these agents, and the appropriate first aid treatment are described.   Main-
 tenance procedures for equipment are also outlined.  Gas handling  procedures
 and training in changing cylinders, calibrating cylinders, assembling regula-
 tors, and leak testing cylinders are part of the  training program.   The
 hazards of gases used at the facility are also described.
           Training of employees occurs every 6 months.   All employees are
 continuously monitored for safety.  The safety practices of new employees  are
 carefully monitored for the first 3 months to identify  unsafe  work practices.

 5.3.   Respirators and Other Personal Protective Equipment

           Personal protective equipment required  by the plant  includes safety
 glasses or goggles, bunny suits (coveralls) with  hoods, safety shoes, and
 latex gloves.  Additional protective equipment used during the handling  of
 acids includes aprons with sleevelets and face shields.  Self-contained
 breathing apparatus with a full facepiece operated in a pressure demand  code
 used  when changing lecture bottles for ion implantation.  Self-contained
 breathing apparatus (SCBA) are also accessible for emergencies within the
 plant.   Those performing maintenance requiring any type of respiratory
 protection use a self-contained breathing apparatus described  above.
           The plant respiratory protection program requires employees using
 respirators to undergo a medical examination to determine their ability  to use

this equipment.  The prograa administrator is the employees' supervisor.  Trie
correct respirator is selected by the supervisor, and the employee is trained
in the use, inspection, assembly, disassembly, cleaning, and sanitizing of the
respirators.  Respirators are tested by the employee using a negative pressure
test.  A logbook is provided for each respirator which details its use,
cleaning, and inspection.  Only self-contained breathing apparatuses were used
at the plant.  Engineering controls preclude the need to use other respiratory
          The facility  is equipped with acid suits, disposable acid resistant
coveralls and SCBA with full facepiece operated in a pressure demand mode for

5.4.  Medical Program

          The plant employs a full-time registered nurse during the first and
second shifts, and a physician is available from the corporate headquarters.
Furthermore, security personnel are trained in first aid and cardiopulmonary
resuscitation. Medical  treatment is available at a nearby hospital.
          The medical program requires only a medical history with visual
tests of employees also being performed.  Baseline tests of urinary arsenic
levels are  required of  all employees working with arsenic compounds.   A  pre-
placement medical examination of all new employees began on September 1, 1981
and physical examinations will be required on an annual basis.   This program
includes a  medical history questionnaire, vital signs, routine urir.alysis,
blood tests, and back analysis (Xraus-Weber fitness exam and X-ray).
          Emergency equipment available at the plant includes showers, eye
wash stations, and oxygen supply. --

5.5.  Housekeeping

          As noted, the production area is a Class 100 clean room  (100 parti-
cles per cubic foot).  Dust levels in the rooms are controlled by passing roor.
air through HEPA filters.  Also, as stated earlier, production workers are
required to wear bunny suits with hoods, booties, gloves and safety glasses or
goggles.   Individuals with facial hair are required to wear -asks.  These
controls are designed to limit particulate levels in the fabrication  area.


           Additional engineering controls ha-"e been included in the design of
 the  facility  which eliniinates many housekeeping problems .   These  engineering
 controls  are  defined in detail in Section 7.0 and include  distribution lines
 ior  pumping  process chemicals from a central  storage  area  to the  specific  unit
 operation, and  suction lines  and waste drains for transporting  waste  liquids
 from wet  chemical areas to waste storage  and  treatment  facilities.   Pump oils
 and  filtration  media from roughing pumps  are  replaced by reversing  the  pump
 flow and  pumping wastes into  a container.  The pumping  oil  and  filtration
 media are changed every 1 to  4 months. Written maintenance  procedures  have
 been established for process  equipment.   Equipment  maintenance  operations  were
 not  evaluated during the survey.
           Hazardous wastes generated at the facility  are transported  to a
 Class I hazardous waste landfill for disposal.   Hydrofluoric acid wastes are
 transported  to  an acid treatment facility.  Other acid  wastes are diluted  to
 an acceptable pH level and disposed of in the sewer system for  treatment by
 the  public sewage treatment plant.

           Sample  data  from  previous  plant  surveys and equipment evaluations
conducted  by Intel  staff  have  been  compiled by plant staff but were not
reviewed at the preliminary survey.  Monitoring  data available include results
of the plant area monitoring network,  personal monitoring of worker exposures,
and equipment . evaluations.

                       PROCESS  OPERATIONS  OF INTEREST

          A variety of strategies are  used at Intel to control emissions and
work exposures.   Control strategies  used include local and general exhaust
ventilation, process modification, process substitution, process isolation,
process and environmental monitoring,  personal protective equipment, and work

practices.  The  rollowing  is  a  detailed  description  of  each process operation
and the control  strategies  applied.
7.1.  Chemical Vapor Desositic
          Chemical  vapor  deposition  (CVD)  is  the  formation of a stable com-
pound on  a heated substrate  by  the  thermal  reaction or decomposition of
gaseous compounds.   Examples  of  CVD  observed  at the plant include silicon
nitride deposition,  polycrystalline  silicon deposition, and silicon dioxide
deposition.  The deposition  of  silicon  nitride is performed in a direct digi-
tal control furnace.   Silicon dixoide is deposited in a continuous vapor phase
system.   A general  description  of the direct  digital control furnace is given
below.  The description is applicable to those operations which use the DDC
furnace (silicon nitride  deposition, thermal  oxidation, diffusion, and
hydrogen  alloying).
          The direct:  digital  control furnace  system includes a microprocessor,
which organizes the  overall  furnace  processing using feedback control loops.
The control loops are  used to insert and withdraw wafer carriers at a speci-
fied rate, to raise  or lower  the furnace temperatures at a specified rate, to
adjust the various  gas flows  as  a function  of time, and to monitor the actual
temperature profile  inside the  furnace  as  a function of time (Douglas, 1981).
The microprocessor  can automatically clean  the furnace, perform an automatic
calibration cycle,   and tailor  the dynamic  performance of the furnace to a
given process step.   The  advantage of the  direct digital control furnace is
the high  degree of  process reproducibility  possible with the system.  A dis-
advantage is that all  control is lost if the  computer fails.
          The primary  components of"the system include an electronics
enclosure, jungle cabinet, load  station, furnace modules, and source cabinet.
The source cabinet is used for  the diffusion  furnace bubbler system, source
dopant system, and as  a location where  the  gas systems interfaces with the
furnace tube.
          Wafers are received in fused  silica boats.  The boats are loaded in
queue  onto a carrier and  the  carrier is placed into a silica glass tube.  The
entire task is performed  by a single operator at a laminar flov work bench


close  to  the  furnace.   A glass  plug  is  removed  fron  the  furnace  tube  and  the
elephant  is manually  lifted  into  the furnace  loading  station  and  attached  to
the  furnace.   The  loading station is enclosed with movable  panels, which
allows  access during  loading and  unloading  of the elephant.
           The silica  glass elephant  is  ground at one  end  to promote a  fairly
tight  seal with  the furnace  tube.  A small  round opening  at the opposite end
of the  elephant  receives a silica glass  tube  called a boat  puller.  The boat
puller  is  used to  advance the boats  into the  furnace  at a programmed rate.
The  boat  puller  also  retrieves  the boats upon completion  of the cycle.
           Local  exhaust ventilation  consists  of a local exhaust take-off at
the  furnace tube opening. The  face  velocity  at the ventilation take-off was
reported.to be 600 to 1300 lineal feet  per  minute.
           The chemical vapor deposition  of  silicon nitride is used in  both
bipolar and MOS  technologies.  In the production of bipolar integrated
circuits  the  silicon  nitride deposition  provides for  passivation.  In MOS
integrated circuits it is used  for multilayered insulators.
           Silicon  nitride is formed  on  silicon wafers  in  a direct digital
control furnace.   The  deposition  of  silicon nitride on silicon wafers is
similar to that  described above.   The wafers  are loaded into boats, placed in
a carrier, and inserted into the  elephant.  The elephant  is attached to the
furnace and the  boats  are automatically  loaded into the furnace.  The pro-
cessing sequence is controlled  by the system  microprocessor, as described
above.  The wafers  are heated in  an  atmosphere of dichlorosilane and ammonia.
An amorphous  silicon  nitride film grows  on  the wafer  surface and hydrogen gas
is liberated  during the reaction.
           Silicon  dioxide deposition is  a form of chemical vapor deposition
(CVD) where a stable  Si02 layer is _formed on  a heated  substrate (single
crystal silicon  wafers)  by the  thermal reaction or decomposition of gaseous
compounds. The Si02 layer is deposited by the oxidation of silane with
oxygen.  The  SiO?  glass  deposition system observed at  the Intel plant was a
continuous vapor-phase oxidation  system.  The system  is a low-temperature cold
wall  reactor  operating at atmospheric pressure.  It includes a reaction cham-
ber,  gas control system,  time and  sequence  control system, heat source, and
effluent handling  system.  Time and  sequence  of gas input (SiH^, Oo and
POT)  are computer  controlled.


          Prior  to  loading  wafers  into  the  system,  the wafers  are  cleaned  with
a degreasing  solvent,  followed  by  acid  cleaning  (sulfuric hydroxide -
H2S04 and H202)  and  drying.   The wafers  are manually loaded in  the
Si02 glass deposition  system.   Wafers are automatically  transported through
a nitrogen purge  to  the  preheat zone and into  the reaction chamber.  The
Si02 film is  deposited by  the oxidation  of  silane (SiH4) with  oxygen.
Phosphine is  added  to  the  reaction chamber  gases and is  deposited with the
Si02 as a dopant.   After the  deposition  sequence is completed,  the wafers
are removed and  placed in  wafer carriers.

          7.1.1.  Engineering Controls.  Local exhaust ventilation of the DDC
furnace consists  of  a  takeoff located at the furnace tube opening.  Air flow
is directed from  the source cabinet  through the  furnace  tube to the furnace
opening.  A nitrogen purge  of the  furnace tube opening provides dilution of
the reactant  gases  released from the furnace.
          The furnace  loading station is enclosed by movable panels.  The
elephant containing  the  wafer carriers  is placed in the  loading station and
attached to the  furnace.   The panels are closed  and the  load station is auto-
matically purged  with  nitrogen.  The source cabinet containing  the bubbler
system, source dopant  system, and  gas interface  systems  is enclosed.
          The continuous vapor  phase reactor consists of a preheat zone,  main
Si02 deposition  zone,  and  a post heat zone.  The wafers  are manually fed to
the reactor.  Wafers enter  a  nitrogen purge in the  preheat zone and pass
through a nitrogen  curtain  prior to  the  main deposition  zov.e.   Phosphorus-
doped silicon dioxide  is deposited on the wafer  surface  in the  main zone.  The
system consists of a heater block,  dispersion  tubes, gas controls, and local
exhaust ventilation  of the  reactor".  Wafers with a  deposited silicon dioxide
layer pass through the nitrogen curtain  and nitrogen purge.  Loading and
unloading stations are normally covered  during operations.  The metal covers
are manually removed when  loading  or unloading wafers.
          The reactor  is located in  a protective enclosure.  The gas control
systems for silane, oxygen, nitrogen, and phosphine are  located at the tront
of the process unit.   Wafer loading  and  unloading is from the  side of the
equipment .

          7.1.2.  Monitoring.  The DDC furnace is nicroprocessor controlled.
The microprocessor controls the process cycle directing loading and unloading
of the furnace, gas flow, temperature, calibration, and cleaning.  A specific
"recipe" is programmed for the individual process step.
          Environmental monitoring of the workroom is performed with multi-
station, multicomponent sampling, and central analysis by the Miran® 801.
Sampling ports are located in the clean room area above the gas jungle
cabinets.  Specific details of the gas monitoring system are described in
Section 3.4.

          7.1.3.  Personal Protective Equipment.  Personal protective equip-
ment requirements include normal clean room attire consisting of hoods,
booties, clean suit, latex gloves, chemical safety goggles or safety glasses,
and safety shoes.  Heat protective gloves are used by workers unloading wafers
from the continuous vapor phase reactor.  A heat resistant handle is used to
remove the ground glass cover from the furnace tube

          7.1.4.  Work Practices.  Computer control of the DDC furnace results
in limited contact of the worker with the furnace.  After loading of the
elephant,  the process is completely automated, requiring only that the worker
initiate the program.
          Detailed written maintenance procedures have been established for
the continuous vapor phase reactor.

7.2.  Thermal Oxidation

          The oxidation of silicon to silicon dioxide is an important process
in both bipolar and MOS monolithic, integrated circuit technology.  Thermal
oxides are used in both technologies as barriers to the diffusion of doping
agents.  Oxide areas, which have been defined by photolithography, are used  t
establish the boundaries of the circuit pattern.  Silicon dioxide is also used
in MOS technology as the dielectric gate material.
          Silicon wafers are oxidized by a wet oxidation process.  Deionized
water vapor in a nitrogen carrier gas is introduced into the furnace as  the

oxidant.  Silicon dioxide is formed on the wafer in a direct digital control
furnace.  The furnace design and processing steps are similar to those
described for chemical vapor deposition of silicon nitride.  The wafers are
loaded into boats placed on a carrier, and inserted into the elephant.  The
elephant is attached to the furnace and the boats are automatically inserted
into the furnace.  The processing sequence is controlled by the furnace system

          7.2.1.  Engineering Controls.  Thermal oxidation is performed in DDC
furnaces using a wet oxidation process of deionized water vapor.  Engineering
controls for the DDC furnace are summarized in Section 7.1.1.

          7.2.2.  Monitoring.  General clean room monitoring is performed  with
remote sampling ports and analysis by the Miran® 801.  The monitoring system
is described in Section 3.4.  The process control of the DDC furnace is
described in Section 7.1.

          7.2.3.  Personal Protective Equipment.  Personal protective equip-
ment requirements for thermal oxidation include chemical safety goggles or
safety glasses, safety shoes, and heat protective gloves.  General clean room
attire is also required.

          7.2.4.  Work Practices.  Work practices for operation of the DDC
furnace are described in Section 7.1.4.

7.3.  Doping and Hydrogen Alloying

          Doping is the process of introducing impurities into the substrate
to produce changes in its electrical properties.  These impurities are
referred to as dopants.  Two specific doping methods observed at the plant are
diffusion and ion implantation.  Hydrogen alloying of the substrates is also
performed to remove radiation damage from the metalization process and to
promote good electrical contact between the metal and silicon.


          Gaseous dopants used  at  Intel  include  boron trifluoride, arsine
phosphine.  Doping of substrates with 'gaseous dopants is performed in direct
digital control diffusion furnaces.  These dopants are used for diffusion and
ion implantation.  The dopant gases are  introduced to the diffusion furnace at
atmospheric pressure.  The gas  flow is controlled by the system
          Arsine, phosphine, and boron trifluoride dopant gases are used in a
high vacuum ion implantation system.  Gas flow and other process variables are
controlled by  the system microprocessor.  Ion implantation gases are stored in
ventilated gas storage cabinets located  within the ion implantation unit.
          Diffusion operations  introduce impurities into the substrate to
produce changes in the _electrical  properties of  the substrate.  Dopants used
at the plant include n-type electron donors (POCl^).  Doping of the sub-
strate is performed in a direct digital  control  furnace.
          Prior to doping, a layer of silicon dioxide is deposited on the
substrate.  Photolithographic processes  are used to define the mask pattern.
The wafers with the silicon dioxide mask are loaded onto a carrier and placed
into a silica  glass tube or elephant.  The elephant is placed in the load
station of the furnace and connected to  the furnace with a ground glass seal.
A small round  opening in the opposite end of the elephant receives a silica
glass tube which is used to insert the carrier into the furnace at a pro-
grammed rate.  The doping agents,  introduced into the furnace in nitrogen,
diffuse into areas of the substrate where the mask layer has been removed from
earlier photolithographic processes.
          Diffusion of the dopant  into the substrate is determined by the
temperature, gas flow, time sequence, and type of dopant.  The dopant
(POC13) is contained in a quartz bubbler placed  in the source cabinet of the
furnace.  Nitrogen is bubbled through the liquid.  The resulting gas contains
sufficient POC13 for doping.  The  POC13  reacts with oxygen in the furnace
to produce ?2®5'
          Ion  implantation is used in both bipolar and MOS technologies  to
introduce selected impurities into semiconductor wafers.  This technique
allows greater control over the amount of dopant being introduced and operates
at much lower  temperatures than diffusion processes.

          Ion implantation uses  the  focused  ion  bean  of a source gas  to dope
semiconductor material.  The beam is  generated at  the ion source.  The source
consists of a Freon cooled arc chamber  (anode) surrounding a tungsten filament
source (cathode).  An electrical arc  discharge is  maintained by passing a
source gas (or vaporized liquid) through  the  chamber.  The ion beam is draw-n
from the arc chamber by an extraction electrode  and directed to the analyzing
magnet.  The magnet analyzes, resolves, and  focuses the beam and selects only
the desired species of ions required  for  implantation.
          The,selected ions are  then  targeted through the acceleration tube in
the direction of the wafer target.   The acceleration  tube optimizes both the
focusing and transmission of the selected  ion beam.  The selected beam enters
the lens and scavenger box, where it  is further  focused and deflected toward
the wafer target.  The scanner has  the  capacity  to move the ion bean in a
raster pattern to cover the entire  target  area with the smaller ion beam
diameter.  The focused beam finally  enters the target chamber, where a silicon
wafer has been automatically removed  from  a  standard wafer cassette (boat) and
positioned for impact.  Each target  wafer  enters the  chamber via an input
vacuum lock.  The locks are sealed  and  vented before a wafer enters or leaves
the target chamber.  The ion iraplanter  scans  the beam across the target wafer,
implanting the desired ion species  at a preferred  concentration.
          Three  types of source  gases are  commonly used during ion implant-
ation:  boron trifluoride, BF3;  phosphine  in hydrogen; or arsine in
hydrogen.  The source gases are  supplied  in  lecture bottles located in the
nitrogen purged  gas box.
          The ion implanter maintains three  independent vacuums:  the source,
beam line, and end station (or target).  Typically, each vacuum is produced by
a mechanical roughing pump and a diffusion pump.   The input and output vacuum
locks are serviced independently by  two roughing pumps.  Cryogenic pumps may
be used in the source and end station regions.   The beamline and end station
are isolated from the beam regions  of the  instrument using liquid nitrogen
locks.  Each pumping system is fully  automatic and will shutdown the implanta-
tion process in  event of a vacuum leak.
          The instrument and gas box  are vacuum  vented using dry nitrogen.
The target chamber and wafer handling mechanisms are  ventilated by a v
laminar flow hood at 600 cfra.

          Hydrogen alloying is  the process of heating the substrate in a
hydrogen or hydrogen/nitrogen atmosphere.  It is performed to remove radiation
damage from netalization and to minimize  contact resistance between  aluminum
and silicon.  Hydrogen alloying is performed in direct digital control
furnaces identical to those used  for  chemical -vapor deposition of silicon
          The wafers are loaded into  carriers, placed in an elephant,  and
connected to the furnace.  The  wafers are automatically inserted into  the
furnace.  Wafer loading/unloading, temperature, gas flow, and process  time are
automatically controlled by a microprocessor control unit.  Following  inser-
tion into the furnace, the wafers are heated in a pure hydrogen atmosphere for
a specified time.  The furnace  is purged with nitrogen and the wafers  are
automatically removed.
          The elephant containing the wafers is attached to the furnace at a
loading station that is enclosed  by movable panels for access during loading
and unloading.  The furnace tube  is sealed with a removable quartz cap when
not in production.  A ground glass seal on the tube end provides the connec-
tion for attaching the elephant or cap to the furnace.  The system is  purged
with nitrogen during the alloying process to dilute hydrogen gas escaping from
the seal.
          Local exhaust ventilation is provided at the furnace opening.  A
ventilation take-off is located adjacent  to the furnace tube opening.   Hydro-
gen sensors are located in the  source cabinet, at the load station,  and
exhaust duct, and above the jungle cabinet.  Hydrogen gas is supplied  to the
furnace in a double jacketed stainless steel/?VC line.  This line is purged
with nitrogen from the furnace  back to the storage cabinet.  A hydrogen
monitor is located in the storage Cabinet.

          7.3.1.  Engineering Controls.  As described, diffusion and hydrogen
alloying are performed in a DDC furnace.  Engineering controls for the furnace
are described in Section 7.1.1.   DDC  furnaces used for diffusion require the
use of liquid dopant sources.   Quartz bubblers containing POC13 are mounted
in the enclosed source cabinet.  Air  flow froa the cabinet is directed to the

   rusion furnace-  Lccal exhaust ventilation  of  the DDC furnace  is  located at
the furnace tube opening near the loading  station.
          DDC furnaces used for hydrogen alloying do not require  the quartz
bubbler system.  Hydrogen is supplied  to the furnace from cylinders  stored in
ventilated gas storage cabinets located in the basement.  The hydrogen is
piped to the furnace entering at the source cabinet.  Hydrogen lines are
double jacketed stainless steel in PVC.
          Ion implantation is performed in high vacuum conditions (10~->
torr).  The vacuum is established by a mechanical roughing pump followed by a
cryogenic trap and a diffusion pump.   The  vacuum  creates negative pressure
conditions which limit the release of  the  ions into the workroom air.  Indi-
vidual wafers are loaded into the ion  implantation unit through load locks
which are evacuated with a mechanical  pump.  Prior to loading or unloading
wafers, the lock is purged with nitrogen.   Ion implantation gases (boron
trifluoride, phosphine, and arsine) are stored in a ventilated gas cabinet
located inside the ion implantation unit.
          The~iofi beam source is lead  shield1 ed^t'o" p "rev ent X-ray leakage.  The
ion source is contained within two lead shielded  cabinets.  Access to the
source is through panels which are electrically interlocked to the system.
The cabinets are electrically grounded.

          7.3.2.  Monitoring.  Interlocks  on the  ion implantation vacuum
system will shut down the unit if leaks occur  in  the vacuum system.  Process
monitoring is performed by a microprocessor, which controls wafer cycling and
determines the implanted dose.
          Environmental monitoring of  the  workroom environment is provided by
a sampling port located above the ion  implanter.  The workroom air is sampled
and analyzed by the Mir an® 801 system  described in Section 3.4.
          Hydrogen alloying performed  in the DDC  furnaces is monitored using
combustible gas detectors placed in the load station, source cabinet, and heat
exhaust duct.  A detector is located in the ventilated gas cylinder  cabinet
where the hydrogen cylinder is stored.
          Hydrogen is monitored at the ion implantation unit.  The hydrogen is
used as a carrier for the source gas.  Hydrogen is monitored to determine if  a

-eak condition exists for  the more  toxic  gases.  A hydrogen sensor is located
in the exhaust stack of the  gas  storage cabinet located in the ion icplanter.

          7.3.3.  Personal Protective Equipment.  Personal protection require-
ments for workers operating  the  ion implantation unit, and DDC furnace consist
of standard clean room attire.   This attire includes hood, clean suit,
booties, chemical safety goggles  or safety glasses, latex gloves, and safety
          Individuals responsible for changing gas bottles for the ion
implanter are required to wear pressure demand self-contained breathing
          Workers handling quartz bubblers containing POC13 must wear acid-
resistant gloves, chemical aprons,  and face shields.

          7.3.4.  Work Practices.   Handling of lecture bottles used in ion
implantation is limited to specially trained workers.  Workers are required to
wear positive pressure SCBA  when  handling ion implant lecture bottles.
          Pump oils for the  oil  roughing  pump are changed by reversing the
flow of the pump and pumping out  oils into a container.  The oil is manually
replaced.  Freon for the diffusion  pump is manually charged.
          Phosphorous oxychloride is supplied in sealed quartz bubblers.
Standard operating procedures have  been established for handling the bubblers.
Bubblers are only changed by trained personnel.  The bubblers are received in
metal containers packed in wooden boxes.  The containers are rezcved from the
boxes and transferred to a laboratory hood.  The quartz bubbler containing the
liquid POC13 is removed from the  metal can.  The used bubbler is removed
from the source cabinet, placed  in"a chemical carrier bucket, and transported
to the laboratory hood, where it  is  packed into the metal can, sealed, and
stored for hazardous waste disposal.  The replacement bubbler is transferred
to the furnace in a chemical carrier bucket.  The bubbler is placed in the
source cabinet and attached  to the  furnace.
          Emergency procedures for  corrosive spill cleanup of the bubbler
solution have been established.

7 • 4 •   Wet Chemical Cleaning Processes

          The silicon wafer cleaning process is performed to obtain a clean,
uniform, and stable surface.  The  cleaning operations are performed in Class
100 enclosures using ultrapure, electronic grade chemicals.
          The initial step during  the  cleaning process is the immersion of a
cassette of wafers in a  solution of sulfuric acid and hydrogen peroxide,
commonly referred to as  sulfuric peroxide.  The exact proportions of sulfuric
acid to hydrogen peroxide were not specified at Intel.  However, typical
solutions used in industry contain approximately nine parts concentrated
H2S04 to one part ^02 .  Nitric or hydrochloric acid may be added in
small amounts.  The initial solution is designed to remove organic residue,
which may have accumulated on the  wafers during handling.
          A second wet chemical cleaning process is designed to remove
unwanted silicon dioxide formed during the cleaning processes.  The clean
wafers (in cassettes) are submerged in a solution of one part hydrofluoric
acid to ten parts deionized water.  When oxide etching is completed, the
wafers are rinsed in pure deionized water.
          Following the  deionized ^water rinse, the wafers are removed from the
cassettes and dried by spinning under  a nitrogen blow-off.  This portion of
the process is automated.
          The cleaning baths, oxide etch, rinse baths, and nitrogen blow-off
system are located under laminar flow  ventilation.  Baths or etching tubs used
in the cleaning process  are equipped with take-otf vents around the car..-;
perimeter.  The vents are used to  maintain a constant down draft across the
face of each tub.
          Spent solutions used in  the  cleaning process are aspirated out of
the tubs.  New solutions are manually  added.

          7. A.I.  Engineering Controls^.  Wet chemical benches are of plastic
construction.  The benches are located under laminar flow hoods.  Air is
passed through HEPA filters.  Acid tanks and deionized water  tanks  are
recessed in the wet chemical benches.  The acid tanks are heated by electrical
resistance.  Local exhaust ventilation of the  tank is through slots located


inside the tank around  the  top perimeter.  Local exhaust ventilatio-. of the
entire bench is provided by  slot ventilation with take-offs located at the
rear of the bench.  Air flow for the  bench is directed down from the HEPA
filters across the work bench to the  rear ventilation take-off.
          Waste chemicals are removed from the tanks by aspirators located in
the bench.  Waste acid  lines  are plumbed from the aspirator to a central waste
acid tank located outside of  the building.

          7.4.2.  Monitoring.  Sampling ports for the MI RAN7® 801 monitoring
system described in Section  3.4 were  located at ceiling height (approximately
8 feet).  The sampling  ports  in the wet chemical bench areas were located
based on smoke tests  conducted by  Intel.

          7.4.3.  Personal  Protective Equipment.  Workers are required to wear
normal clean room attire consisting of booties, clean suit, hood, latex
gloves, chemical goggles or  safety glasses, and hard toe shoes.  Workers
replacing chemical solutions  are required to wear face shields and chemical

          7.4.4.  Work  Practices.  Wafers are contained in carriers of plastic
construction.  Plastic  handles are attached to the  carrier and the unit is
dipped into the bath.   Release of  the handle is by  hand squeezing of the grip.
Individuals mixing solutions  for the  wet chemical areas are specially trained
in chemical handling.

7.5.  Photolithography

          Photolithography  includes the following process operations:  1)
photoresist application, 2)  substrate exposure, and 3) a photoresist develop-
ment.  These operations are  outlined  below.
          Microelectronic technology  uses photosensitive organic compounds to
delineate the circuit patterns on  silicon wafers.   Exposure  to  light, in
particular light at ultraviolet (UV)  wavelengths, alters the  chemical resis-
tive characteristics  of these photoresist compounds.  The  photoresists  ar;


grouped into two separate  classes  depending  on  their  reaction  to UV  light
exposure.  Negative photoresists become  insoluble or  resistant  to etching
chemicals on exposure.  Positive photoresists become  soluble or nonresistent
when exposed.  Negative UV sensitive  photoresists are most frequently used
during the production of integrated circuits.
          Intel uses both  positive and  negative photoresists during  integrated
circuit production.  Since negative photoresists were used during the survey,
they will be the model for this process  description.  The application is
actually a series of individual "job  shop" operations presented as one process
for simplicity.
          The first operation  is the  actual  application of photoresist
material to each clean, dehydrated wafer.  A uniform  coat of photoresist is
spun onto the wafer.  The  use  of either  positive or negative photoresist
depends on the requirements  of the circuit pattern.   In either case  the
procedures for application will be the  same.  The photoresist is deposited in
a uniform layer by spinning  at speeds of several thousand rpm's.  Chemical
exposures for this operation are most often  associated with the photoresist
solvent; at Intel the negative photoresist solvent was xylene, the positive
was cellosolve acetate.  During the spin process excess photoresist  will be
expelled from the wafer surface,   Redeposition of the expelled material is
prevented through the maintenance  of  a  downdraft at the wafer perimeter.  In
addition to the local downdraft, laminar flow ventilation is used to establish
a clean area around the application/spinning equipment.
          The photoresist  coated wafers  are  transfered in cassettes  to a pre-
or soft-baking oven.  The  purpose  of  the pre-baks is  to drive off the remain-
ing photoresist solvent prior  to wafer  exposure.  Laminar air flow is provided
at the pre-bake work station.  Intel  used a  nitrogen  atmosphere, resistance
heated oven for the pre-bake.
          Substrates coated  with a soft-baked photoresist layer are  exposed
using a projection mask alignment  system.  Cassettes  containing substrates are
manually loaded into the alignment system.   Single wafers are automatically
removed from the cassette.   The substrate is held in  a vacuum chuck, which is
part of an x-y table with  rotational  adjustment.  A single wafer is  aligned
                    split  field optics,  which permit  simultaneous viewin- of


the wafer and mask.  After alignment  the substrate is clamped  to  the mask,  the
microscope is moved away, and  the substrate  is  exposed  to ultraviolet light.
A mercury vapor lamp is used as  the UV  source.  The alignment  system exposes
the substrate from a 1:1 mask  by successive  sweeps of an exposure slit.
Exposed substrates are automatically  returned to the cassette.
          An operator is seated  at the  alignment system to load and unload
cassettes and to check mask alignment.  The  mask alignment system has internal
environmental controls, which  heat the  air and  filter particulates.
          The development process consists of rinsing away the dissolvable
portions of the exposed photoresist film from the surface of the silicon
wafer.  The dissolvable portion  of negative  photoresist is the area covered by
the mask which has not been exposed to  UV light.  In the case  of positive
photoresist, the portion removed is the exposed film surface.  The rinsing
process usually consists of chemical  dissolution of the soft photoresist and
finish rinsing in deionized water.  The developed photoresist  is finally heat
treated in a post- or hard-bake  oven  to improve its hardness and adhesion
          The photoresist development process at Intel receives the exposed
wafers in a standard cassette  carrier.  The  cassettes are manually submerged
in the dissolution chemical and  deionized water baths.  A mixture of n-butyl
acetate and various mixed isodecanes  are used to remove unexposed negative
photoresist.  Exposed positive photoresist is removed using a  solution of
sodium hydroxide.  Both dissolution baths are followed by rinses in deionized
wa t e r .
          Post- or hard baking at Intel is performed using a resistance heated
batch oven.  Laminar air flow  is present at  the oven and work  station.  No
additional local ventilation was observed.

          7.5.1.  Engineering  Controls.  Wafer  cleaning, heating, application
of photoresist, soft-bake, projection mask alignment, and hard bake are done
under laminar flow hoods with HE?A filtration.  The spin-on  process for
application of photoresist is  automatically  controlled.  Local exhaust or  the
operation directs air downward around the perimeter of  the spinning platform
to a local exhaust take-off located at  the base of the  platform.  Air enters
the enclosure through openings in the rear of the enclosure.

          The mask alignment system contains internal environmental controls.
The wafer exposure area is enclosed to prevent contamination of the cask and
wafer and to limit ultraviolet light emission.  Interlocks of the projection
mask aligner are also designed to prevent ultraviolet light emissions.

          7.5.2.  Monitoring.  Sampling ports for the MIRAN® 801 monitoring
system are located in the photolithography area.  The system is described in
Section 3.4.
          Monitoring of process operations is through automated control of the
process cycle.  The process  cycle for application of the photoresist is
automatically controlled to  provide uniformity.

          7.5.3.  Personal Protective Equipment.  Personal protective
equipment used in the photolithography area consists of the normal clean room
attire of hood, clean suit,  latex gloves, booties, chemical safety goggles or
glasses, and safety shoes.

          7.5.4.  Work Practices.  The handling of individual wafers requires
the use of vacuum wands or tweezers.  Removable handles are used to place the
wafer cassettes in the developing and rinse tanks.  Paper towels vetted with
isopropanol are used by workers for general equipment cleaning.

7.6.  Plasma Etching

          Plasma etching is  a dry chemical etching method used to remove a
specific material or layer from the wafer surface.  It is used in the
fabrication of semiconductor devices where fine line widths are required.  The
wafer to be etched may be a  thermal Si02 layer, aluminum or aluminum alloy
thin films, silicon nitride  or silicon.  A photoresist layer is spun onto the
wafer, baked, and exposed.   The wafer is then developed and hard-baked.  The
wafer at this point contains a baked photoresist layer with areas of the
underlying substrate exposed from the developing process.  The substrate is
then ready for etching.  The gas used in plasma etching is selected based on
the specific substrate material to be etched.

          As noted in Section 4.0, two types of  plasma  etching  systems  are
used  at Intel,  planar plasma etching and barrel  reactor  plasma  etching.   Both
etching processes are located in Class 100 clean rooms  under  laaiinar  flow-
hoods.   The planar plasma etching system consists of a  reaction  chamber  with
parallel electrode plates.  The top electrode acts as a  cathode  to  establish a
radio frequency (RF) field in the chamber, while the lower  electrode  (anode)
holds the wafers.  Wafers are loaded on platens  and inserted  into the reaction
chamber.  The chamber is sealed, purged with nitrogen,  and  evacuated  to
approximately"0.1 to 10 torr.  A plasma is created between  the  plates by
passing a reactant gas through the radio frequency field.   Ultraviolet
radiation generated from the plasma may be released from  the  reaction chamber
through the glass viewing port.
          The plasma consists of a variety of ions and  free radicals.  The
free radicals chemically attack the substrate but do not  appreciably  attack
the protective photoresist.  The reaction products are  removed  from the
chamber by the exhaust system.  A Freon gas is used as  the  reactant gas  for
the planar plasma etching system.  The fluoride  ions produced are reactive
with silicon dioxide.
          The barrel reactor system consists of  a cylindrical chamber.   The
wafers are vertically mounted in a fused silica  carrier.  A plasma  is created
by an RF coil outside the reactor chamber.  A perforated  cylinder surrounds
the substrates which shunts the RF field and confines the plasma between  the
reactor wall and the cylinder (Colclaser, 1930).  The reacting  species pass
through the perforated cylinder and chemically etch the  substrate.  The  chemi-
cally active free radicals in the plasma react with the  wafer surface causing
etching through a reduced-pressure adsorption-reaction-desorption process
(Douglas, 1981).  The sequence of events prior to the etching is similar  to
that described above.  A Freon gas is introduced into the barrel reactor  and a
radio frequency field is established which generates a  plasraa that  is reactive
with silicon nitride, silicon dioxide, and polycrystalline  silicon.   Tie etch
is believed to be the result of atomic fluorine,  which  diffuses  to  the  silicon
surface, forming a volatile Si?4 that diffuses away from the  surface.
          The advantage of the planar plasma etch system over the barrel
reactor plasma etch system is its ability to produce

wnere Che etch is primarily in  one  direction  (generally  perpendicular  to  the
substrate surface).  Wet  chemical etching methods  and  barrel reactor  plasma
etching systems produce isotropic etching profiles where  the etch  rate  is
equal in all directions.  Isotropic etching results  in undercutting of  the
resist layers.

          7.6.1.  Engineering Controls.  Plasma etching  processes  operate
under vacuum conditions.  The vacuum  is  created usin^  a mechanical rou^hin^
                                                     o                 o   o
pump.  The system pressure is negative  to room pressure.  The plasma gases are
exhausted from the pump through local exhaust.  Pump o'ils are continuously
          The plasma etching systems  are located under laminar flow hoods.
They may be considered as substitutes for wet chemical acid etching where
hydrofluoric acid is used to etch the wafers.  Plasma etching uses rreon as a
source of fluoride atoms.  Px.eactive fluoride  ions  are  formed in an RJ field.

          7.6.2.  Monitoring.   No specific environmental monitoring systems
for plasma etching are used.  Process monitoring of  the plasma etching systems
is by automatic control of the  equipment.

          7.6.3.  Personal Protective Equipment.   Personal protective
equipment used at the plasma etching  systems  consist of normal clean room
attire.  Specific equipment used for  the process operation was not identified.

          7.6.4.  Work Practices.   Wafers are mounted on platens or in
carriers and manually placed in the reaction  chamber.  Specific practices used
for the operation of the  equipment  were  not observed.
          Mechanical pump oil is changed by reversing  the pump flow and
pumping the oil into a waste container.  Oil  is manually added from portable

7.7.  DC Sputtering

          Aluminum is deposited on  the  wafer  surface by  removing  surface
molecules of the raet-il from a source  material (target) by bonbard-.ent  with


energetic ions.  The ionizing energy is supplied by a direct  current  (DC)
power supply.  The sputtering process occurs in a vacuum system.  The  system
operates under high vacuum conditions (approximately 30 - 70  x 10"^ torr).
The high vacuum conditions are created in the bell jar by punping first with  a
roughing pump,  then a cryogenic pump.
          The wafers are cleaned and dried prior to loading on the anode,
which is done through a loadlock attached to the sputtering chamber.   The
loadlock is closed and pumped to vacuum.  The wafers are automatically loaded
into the bell jar, where a high vacuum is formed.  Argon is introduced to the
chamber and the DC current is applied.  A gaseous discharge of metal atoms is
sputtered from the target to the wafers, producing a thin film of aluminum on
the wafer.  The chamber is then automatically unloaded and the wafers  are
transferred to the loadlock, where they are ready for photoresist application
and further processing.  The sputtering sequence is automatically controlled.

          7.7. 1.  Engineering Controls.  The DC sputtering system is located
in the general clean room environment.  The process operates  at a pressure
which is negative to that of the room.  The pump exhaust is vented through the
local exhaust ventilation system.  The metalization system employs two
chambers, a loading chamber and a bell jar chamber.  The separate loading
chamber minimizes contamination of the sputtering chamber bell jar.  The
process is automatically controlled.

          7.7.2.  Monitoring.  Specific environmental monitoring systems to
evaluate emissions from the process are not present.  The process is monitored
by automatic control of the process cycle.  Interlock is provided to stop the
cycle if the hood chamber door is obstructed.  A vacuum interlock system will
shut down power if the chamber vacuum is not achieved.

          7.7.3.  Personal Protective Equipment.  Personal protective  equip-
ment consists of normal clean room attire.  Specific equipment used for the
process operation includes gloves used during chamber cleaning with potassium

          7.7.4.  Work Practices.  ±.quipr.er.t maintenance requires removal  of
the bell jar and internal reactor assembly for cleaning.  The bell jar is
cleaned with potassium hydroxide.  Metal sputtering parts are bead-blasted  for

7.8.  Electron—Beam Evaporation

          Gold is deposited on the substrate by heating the gold in a high
vacuum and condensing the vapor on a cooler substrate.  A focused electron
beam provides the heat necessary to vaporize the metal.  The wafers are placed
above the source in a movable fixture called a planetary.  During evaporation
the wafers are rotated to ensure maximum uniformity of the deposited layer.  A
glass bell jar is lowered over the fixture and a high vacuum is pumped.
          The gold deposition process occurs in a basement area separated  from
other fabrication activities but not in a Class 100 clean rocn.  Equipment
ventilation is limited to exhaust for the vacuum pumping system.  The vacuum
system is similar to that previously described.  The vacuum is created by an
initial rough pumping followed by a liquid cold trap and diffusion pump.

          7.8.1.  Engineering Controls.  The system operates under high vacuum
conditions, resulting in a chamber pressure which is negative to that of  the

          7.8.2.  Monitoring.  No specific environmental monitoring systems
are used to evaluate work room emissions from the process.  The process cycle
is monitored through microprocessor control.  The entire vacuum cycle is
automatically controlled.

          7.8.3.  Personal Protective Equipment.  Personal protective
equipment  used during electron beam evaporation was not identified.  The  unit
was not in operation during the preliminary survey-

          7.8.4.  Work Practices.  Work practices specific to the operation
were not identified.

                     8.0  CONCLUSIONS AND RECOMMENDATION'S

          The production of integrated circuits at Intel is performed in an
environment established to control product quality and provide a safe work
environment.   Individual engineering controls are used within this clean room
environment to control product quality and protect the workforce.  Individual
process operations may be located in the clean room within a laminar flow
bench with HEPA filtration.   These process operations have associated
engineering controls.   These process specific engineering controls include
operation at  negative  pressure (vacuum conditions), local exhaust ventilation,
automated process control (microprocessor),  enclosure (other than vacuum
conditions),  shielding, and  interlocks of the operation..
          Work practices, environmental and  process monitoring systems,  and
personal protective equipment are used by Intel to complement engineering
controls.  Intel appears to  have a well-engineered, state-of-the-art facility,
with a comprehensive health  and safety program to ensure protection of the
health and safety of the workforce.
          Areas that warrant further study include:
          1.   Ventilation System Design—It  would be beneficial to document
              how the  overall system is designed, how balance is achieved in
              the system, and how the adequacy of the ventilation system is
              determined.  Procedures and work practices in maintenance  of the
              system should  be evaluated in  more detail.  The general design
              for adding processes and capacity should also be discussed.
          2.   Monitoring Systems—The calibration and testing of the Mi ran®
              801 and  the combustible gas monitoring systems should be
              detailed.  The analy.sis of output data trends should be
              evaluated.  Results of personal monitoring conducted by Intel
              should be evaluated since the  data may be useful in documenting
              the effectiveness of the control technology.
          3,   Work Practices—Intel appears  to excel in establishing safe work
              practices.  Documentation of the overall training philosophy,
              training methods, and cost of  training (administrative burden
              and employee time) would be beneficial.

-Maintenance Activities--The liaintenance activities  of  the
integrated circuit manufacturing processes should be
investigated.  Work practices should be identified.  Methods
used in controlling emissions and worker exposures  during
maintenance activities should be detailed.

                               9.0  REFERENCES

Colclaser,  R.  A.   Microelectronics:   Processing and Device Design.   John Wiley
  and  Sons.   New  York.   1980.

Douglas,  E.  C.    Advanced  Process  Technology for VLSI Circuits.   Solid State
  Technology.   24(5):65-72.   1981.