Center For Microstructures and
Devices
Clean Room Safety Training
Manual
Author: Dr Lorraine Day
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CAMD Home Page.
This monograph has been prepared to describe those hazards which are associated with silicon
wafer preparation and processing as well as other hazards connected with the cleanroom
environment. It is intended as a guide only and not as a replacement for specific training in
cleanroom activities.
The CAMD cleanroom facilities have become user-oriented rather than the mere assembly of
cleanroom facilities. This is an inevitable function of cleanroom facilities and a direct result of the
growth of this facility.
As described above, laboratory worker related accidents account for some 6000 workplace
injuries per annum in the United States. Further, an additional 50,000 deaths have been
attributed to unintentional exposures to hazardous chemicals. Since training is meant to impart
information and information is known to reduce risk, this training session has been set up to
inform you of the hazards associated with cleanroom work.
The cleanroom is a laboratory setting full of potential hazards which include but are not limited to
electrical, radiation, chemical and thermal risks. Since everyone working in the cleanroom is not
equally familiar with all the risks, this training session will seek to ascertain that everyone has
some rudimentary exposure to the common cleanroom hazards.
The processing lab is essentially a chemical laboratory. Chemicals shall be identified as
substances that are potentially hazard- ous. There are many different types of chemicals, each
with there own particular associated hazards. A glossary of terms follows.
This training is undertaken to assure that individuals of differing backgrounds receive a uniform
experience for working in the CAMD cleanroom. Most users of the CAMD cleanroom have had
minimal exposure to a working chemical laboratory setting.
In addition to the special concerns of cleanrooms, this training targets the chemical hazards
associated with processing of silicon wafers as well as thermal, electrical and other hazards of
particular equipment.
As part of the user community, cleanroom workers have already received radiation safety and
general chemical safety training. This session will identify the various chemical hazards and how
to deal with them, what to do in an emergency situation, how to conduct experiments and will
provide some basic guidelines for general chemical use, storage and hazards.
This training serves as an active portion of the CAMD right-to-know communication program.
Right-to-know laws were imple- mented by OSHA and although, universities are strictly exempt
from such laws, it has always been CAMD policy to adhere to these regulations. The right-to-
know gives workers access to information on the hazards to which they can reasonably be
expected to be exposed at CAMD. This information is contained in the MSDS
People are often concerned about rules and regulations. In the picture above, it is clear that
CAMD is not nearly as stringent as many other facilities. Cleanrooms are controlled environments
in which each action is controlled and well thought out.
Toxic chemicals make you sick if you breath, swallow or touch them. Corrosive chemicals burn
or damage human skin, eyes, nose or lungs and dissolve metal. Flammable chemicals burn
easily. These are most frequently typified by organic solvents. Solvents also remove protective
oils or lubricants on the surface of our skin. Oxidizing chemicals produce oxygen when mixed
with organics or solvents which create a fire hazard. Such compounds are known as oxidizers or
oxidants and are irritating to the skin, eyes, nose and lungs. An acid is a chemical which corrodes
metal. Etchants are typically acids. All acids burn the skin, eyes, nose and respiratory tract if you
come into contact with them. An alkali, also known as base is a caustic water-soluble substance
which has the capability to burn the eyes, skin and respiratory tract. It is used to neutralize acids.
An asphyxiant is a gas which may be relatively non-toxic (such as nitrogen) but may cause
fainting or even death if it replaces the available oxygen in the air. BOE stands for buffered
oxide etch which contains ammonium fluoride and hydrofluoric acid.
A carcinogen is a compound which is known to produce cancer. Read MSDS sheets completely
when you receive a new chemical . Under Biological effects, suspect carcinogens and mutagens
will be listed. A caustic is a base (alkali) which will burn the eyes, skin or respiratory tract. Most
bases (alkali) are called caustic. A ceiling standard is a government dictated value which
specifies the maximum exposure limit of a chemical for a given period of time (normally 8 hours).
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Combustible substances are those that will burn above 100 F. Corrosives are materials which
attack metal and will burn human skin. Both acids and bases are corrosive. A Cryogen is a
substance at very low temperature which will freeze your skin if you touch it. Danger is the
highest degree of hazard warning. The Flash Point is the temperature at which a liquid or volatile
will give off enough vapor to start a fire if an ignition source is present. Hazard Communication
is dictated by OSHA (the occupational safety and health administration) which requires workers to
be informed of their workplace hazards. A large part of this is the MSDS (Material Safety Data
Sheet). Hazardous implies that using a particular substance carries with it some risk. IDLH
Concentration (immediately dangerous to life or health) is the maximum chemical concentration
exposure in 30 minutes which does not produce life-threatening effects.
Incompatible describes chemicals which react dangerously when mixed or used together. When
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one reads an MSDS sheet, the mg/m is that concentration of a chemical that is generally used
to determine the concentration of a solid in air. The MSDS is the material safety data sheet which
is supplied by the manufacturer. It supplied information regarding the hazards of a particular
material and is mandated by OSHA as part of the hazard communications program. When a
chemical is ordered for use at CAMD, the MSDS is mandatory. These sheets are kept in the
beige cabinet adjacent to my desk on the experimental hall floor. The information they contain will
also be shortly available on the CAMD home page. Odor Threshold is the smallest concentration
of a chemical detectable by the majority of humans. An oxidizer is a material which either
releases oxygen by itself or when mixed with organics or solvents. This oxygen is combustible
and can present a fire hazard. The PEL is the permissible exposure limit. This is the maximum
legally allowed exposure to a hazardous substance in an 8 hour time limit (normally). Personal
Protective Equipment (PPE) are those items designed to protect individuals working with
hazards. They may include gloves, face shields, safety glasses. respirators, ear plugs and steel-
toed shoes. A poison is a substance which may cause adverse health effects when eaten,
inhaled or absorbed through the skin.
PPM (parts per million) is a unit of measure most frequently associated with the measurement of
chemicals in air and water. The respiratory system includes the mouth, nose throat, lung
passages and lungs, and is the usual target organ for chemicals which are suspended in the air in
which we breathe. A solvent is a liquid which is capable of dissolving another substance.
Common solvents in use at CAMD include acetone, ethanol, ethylene glycol monobutyl ether.
The TLV (Threshold limit value) is the highest recommended amount of human exposure for a
given compound, without experiencing any deleterious effect. A toxic substance is one capable
of causing injury, illness or health effects. A warning is used to describe an intermediate degree
of hazard for a chemical. Warning properties are those properties of a chemical which allow you
to detect its presence such as odor (i.e. ozone), or eye or skin irritation.
This is the glossary of main terms related to chemical safety.
Major classes of chemicals:
Acids commonly used include acetic, hydrochloric, sulfuric, nitric, hydrofluoric and phosphoric. All
acids are corrosive and will burn skin and eyes upon direct contact. Mists of these acids will
irritate the eyes, nose and throat. You must wear eye protection, proper gloves, and leather
shoes when you work with acids. When pouring acids or handling containers or new or waste
acids, you must also wear a face shield and apron. Never, hand carry chemicals - always use
an acid bucket or a cart.
Hydrofluoric acid (HF) and mixture like BOE (Buffered Oxide Etch) present special problems.
They look like water and if they fall on your skin, you may not feel anything, but HF will continue
to burn until it reaches the bone. If you suspect you have spilled HF or other corrosive material,
flush with water for 15 minutes and inform CAMD safety immediately.
Remember not to store acids with solvents or strong bases. Be familiar with all incompatibilities
for the chemical or mixture
you are using. Read the MSDS documentation, so that there are no
surprises. This is available on the CAMD web page: http:/www.camd.lsu.edu.
Organic solvents are used to dissolve oils, fats and grease or to degrease metals. They are also
contained in photoresists and developers. Solvents can evaporate quickly and can represent a fir
or respiratory hazards and can be readily absorbed through the skin. All solvent use should be
restricted to the fume hood and protective solvent proof gloves. Phenol, like HF has a mild
anesthetic-like effect, so you can鈥檛 feel if you have been exposed. Take special precautions. All
flammable solvents must be stored in flammable storage cabinets and be properly labeled.
Oxidizers are materials which decompose or react rapidly and release oxygen. Such materials
can cause fires or explosions. Always wear gloves, eye protection and leather shoes when
working with oxidizers (such as peroxide). If exposed, flush affected area for 15 minutes with
water. Never store oxidizers with flammable materials or solvents.
Cryogenics such as liquid nitrogen and liquid helium can cause explosion, frostbite or the
production of asphixiating gases if improperly handled, Do not flush area with water if exposed -
allow affected area to warm. If spilled on foot, do not walk - call for help. This is why we have a
buddy system. When handling wear insulated gloves, safety glasses and face shield.
Inert gases such as nitrogen and argon can become dangerous in high concentrations in areas
where there is inadequate ventilation. Always make sure that nitrogen to the cleanroom is well
regulated and not left unattended.
Emergency phone numbers are on the second of 4 pages on the television screen. Report all
accidents immediately to CAMD safety: 9 - 388 - 4616. Emergency plans should be posted
outside the cleanrooms and are located at each beamline.
Remember to turn on the fume hood on before you begin any chemical work in the cleanroom.
Work with the sash pulled down at least part way. No chemicals are to be flushed down the sink.
They will be collected and properly disposed of. Never wear open-toed shoes in the cleanroom.
Always use thick gloves when handling acids (usually neoprene). Chemicals should never be
hand carried. Always use the hand carts provided or an acid bucket. Label all containers clearly
and correctly using the NFPA ratings. If unsure about a process or procedure, ask your
supervisor.
Most importantly, think about the consequences of each of your actions. All movement should be
deliberate and well thought out and characterized.
Before beginning a new procedure, always make a dry run first. It is important to identify any
bottlenecks or potential dangers. When using a new chemical, you must read the MSDS frst. i
Supervisors are responsible for providing the appropriate personnel protective equipment.
Stop unsafe practices immediately. Each person should have the right to question a procedure
that he/she considers inherently unsafe. Discuss new procedures with others to make sure you
have not overlooked a potential hazard. Write out the protective equipment list you will need for
each procedure and then ascertain that you have all of the required equipment before
proceeding. CAMD safety can help you make the appropriate choices for a given situation.
If you are pressed for time, do not begin a new procedure. It is better to wait until adequate time
can be devoted to the task. Haste is a prescription for disaster in a chemical laboratory.
Schedule your activities well in advance and make certain to leave a margin of safety for
unforeseen delays. If you are unsure about a process or the making of a particular solution, ask
your supervisor.
Do not use water near electrical power and be aware of thermal hazards in the cleanroom such
as hotplates and ovens.
Always turn on the fume hood before opening a chemical. Make sure the fume hood is clear of
debris and that there are no chemicals stored in the fume hood. Such chemicals must be
removed before beginning your procedures, as other chemicals may not be compatible with your
chemicals. If there are spills in the fume hood, make sure they are picked up before you begin
your task. Use pH paper to check and identify the nature of the spill, then proceed accordingly to
clean up the spill before proceeding.
Remember that wind currents (i.e. other people walking by etc) can adversely affect the flow in a
fume hood. Lower the sash of the hood as low as possible to perform the work. Use an apron and
safety glasses when working with acids as well as heavy neoprene gloves.
Before ordering any personnel protective equipment, check with Shaloma regarding their
applicability for use in a cleanroom. Vendors can often help you decide, if you ask the right
questions. You should ask them to fax in writing that this material is cleanroom compatible.
Remember also that by law, manufacturers must send you the MSDS, so don鈥檛 forget to request it
when ordering. Aldrich is especially difficult in this regard.
The NFPA (National Fire Protection Association) ratings are used at the CAMD facility. This
system was chosen because CAMD must rely on the city of Baton Rouge for fire protection. All
employees, users, students working at CAMD must familiarize themselves with this system as
described above and below.
CAMD is directly connected to the LSU police station via a keltron system. Whenever a fire alarm
is pulled, it immediately sends a taped message to the LSU police who will then inform Baton
Rouge fire protection personnel.
All chemicals in use at CAMD should be tagged with the proper NFPA label. It is also a good idea
to write in both the manufacturer鈥檚 name and date of receipt. This helps to keep track of old or
expired chemicals. Almost all chemicals degrade over time, especially in warm weather.
The blue diamond gives information on personnel safety with a rating system from 0 to 4. 0
means there is no hazard, 1 slight hazard, 2 protective equipment should be worn, 3 do not
- - -
expose any body surface and 4 - any exposure could be life-threatening. These numbers do not
identify whether the hazard is contact or respiratory etc. This information must be obtained from
the MSDS which will also identify the appropriate personnel protective equipment
Most organic substances will burn. Generally flammability is related to the flashpoint of the
material which is in turn related to the vapor pressure of the material. Many solvents will readily
evaporate, such that the concentration in air rapidly rises and will burn, ignite or explode when
exposed to an ignition source.
Once again, a rating of 0 - 4 is used for the red block. Substances such as H2O will not burn and
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have a flammability rating of 0. Those chemicals which have a flashpoint above 200 F. have a
0 0
flammability index of 1. If the flashpoint is >100 F. but less than 200 F., then the chemical is
given a rating of 2. Substances which are volatile or even explosive under most conditions and
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have flashpoints below 100 F. receive a rating of 3. Finally those chemicals whose flashpoints
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are below 74 F. (i.e. room temperature) are given a rating of 4. Such materials must be stored
with extreme caution and care must be used when handling these materials.
In general, it is best to limit the quantity of solvent or other flammable to the smallest amount
possible. Highly flammable solvents should be stored in explosion proof containers (usually metal
cans equipped with spring enclosures). Pouring of solvents into metal drums requires a ground to
prevent static electrical discharge which may act as an ignition source.
Reactivity of compounds can also be classified in an analogous manner. Using a system from 0
to 4, the stability of chemicals may be classified. In particular, changes in pressure or temperature
may have serious implications for many chemicals. This data is reflected in the yellow diamond of
the NFPA symbol.
Compounds such as NaCl are stable and will carry a rating of 0. Those compounds which may
become unstable with elevated temperature or pressure will have a rating of 1. Those substances
which have a slight potential to become unstable even at normal temperature and pressures will
have a rating of 2. Such chemicals can undergo potentially violent reactions. A rating of 3
indicates that the materials potentially explosive. Heat, shock waves or water (if it is incompatible)
may detonate such materials. Persons working with materials with a reactivity level of 4 must
know where such materials are located and must be willing to vacate the premises in which these
materials are stored if there is a significant increase in heat or there is a fire.
Flammability and reactivity data are essential for the proper control of a fire. This information is
contained in the MSDS supplied by the individual manufacturer. The CAMD Safety Office is
available to assist you in the determination of chemical hazards
The final diamond in the NFPA label is white and identifies materials, or other compounds for
which the labeled chemical has an incompatibility. the W with a line through it tells us that this
particular chemical
is incompatible with water. Care must be taken not to wet such a material. This is also important
in fire-fighting where water is the most common extinguishing medium,. Sodium metal is one
compound which is not compatible with water. Other common symbols include OX for strong
oxidizer incompatibility and ACID for this incompatibility.
Since it is difficult to write several compounds or instructions in the white incompatibility block,it is
necessary to make a list of all incompatible materials before working with a new chemical. Once
again this information is contained in the material safety data sheets. Each person working with a
chemical is responsible for reading and understanding the material safety data sheet.
CAMD safety can help you select the proper personnel protective equipment or can discuss your
incompatibility or other chemical problems.
Materials ready for disposal must be properly labeled with the NFPA ratings and the contents of
the container clearly identified. All chemicals must be labeled when used at the CAMD facility.
Labeling of chemicals is always essential. Labels prevent accidents by insuring that proper
conditions are always met and that there are no incompatibilities.
Use only the amount required. Large quantities are cumbersome. This handling difficulty
significantly increases the risk for spills.
Remember that fume hoods are for working with opened chemicals. They are not for storage.
Store all chemicals in the appropriate container. Store acids and caustic separately and
flammable solvents in still another cabinet. Flammable liquids, acid and caustic cabinets are
available just outside of the cleanroom area on the outside perimeter of the experimental hall
floor.
Never hand carry chemicals. Use appropriate bucket carriers and / or carts. Always use face
shields or safety glasses and an apron when working with acids.
Be aware of hot plates and ovens in areas adjacent to where you are working with solvents.
These can be potential fire or explosion hazards.
Always leave your work area clean, pick up spills immediately. Poor housekeeping practices
increase the risk for injury or damage.!
Cryogenic hazards pose several potential risks. Remember that cryogenic liquids are under
pressure. Always wear eye protection and insulated gloves when working with cryogenic liquids.
Full face shields are preferred and are available in the beige safety cabinet on the experimental
hall floor.
Always wear closed, preferably leather shoes when handling cryogens. Sandals are inappropriate
footwear in any laboratory setting. If a cryogenic liquid spills on your floor Do Not Move: flexing a
frozen limb may cause permanent tissue damage. Call for help. This is why we have a buddy
system. The buddy system is based on the observation that we have visual contact between two
persons.
It is probably a good idea to wear a water-proof apron as well, if there is danger of spilling the
cryogenic material.
Remember that all nitrogen supplied to the cleanroom for operation of almost all the equipment is
transported to the cleanroom as a cryogenic liquid first. This is because, this nitrogen is much
purer (i.e. cleaner) than nitrogen from a compressed gas cylinder.
Shorts and sandals are not appropriate for wear when your duties include the use of cryogenic
liquids.
The above foil summarizes compressed gas cylinder handling. Wear gloves and goggles when
handling cryogenic liquids. Never attempt to handle a compressed gas cylinder by hand. Carts
are available for the safe transport of these cylinders. It is most important to ascertain that the
correct regulator is used for the correct gas. Note that these regulators are not interchangeable.
For instance, hydrogen has a back-flow valve to prevent back flow of contaminated gas into the
cylinder. Hydrogen and acetylene have the lowest lower limits for explosion of any gases (4% and
1%, respectively). Do not use a damaged regulator. Tag the regulator immediately and bring it to
the attention of your supervisor.
Use the regulator to control the gas flow by opening the cylinder valve completely. Hang a shut-
off valve tag on the appropriate valve for emergency shut-offs.
Care should be taken with noble gases - such as helium and argon as these are potent
asphyxiants in an enclosed environment. In the cleanroom, nitrogen gas is routinely used and can
also act as an asphyxiant. Therefore, never leave a nitrogen line open, broken or unattended.
Since almost all cleanroom equipment is supplied by nitrogen, there is a very real potential for
this area to become a confined space area, where any gas can displace the available oxygen
When one examines the causes of all compressed gas cylinder accidents at DOE facilities, it is
clear to see that human factors including human error, management and procedural problems
make 2/3 of al the root causes. It is equally clear, that gas cylinders account for a significant
share of the cost of all accidents at DOE facilities. The DOE has recently issued a safety order on
the use of compressed gas cylinders in their facilities.
Up until now, we have focused on chemical hazards.Let us now describe equipment hazards
associated with CAMD cleanroom activities. These fall into two major categories: chemical and
electrical. Cleanrooms contain a lot of high voltage equipment. If you are performing maintenance
on an instrument, make sure that the piece is electrically discharged. Ideally, it should also be
tagged out, so that no one else electrically energizes the instrument when you are for example
gone to lunch or working on a higher priority problem.
Most of the chemical problems have been addressed. Sometimes there are combination
problems. The use of unattended hot plates (especially if not programmable) may cause injury or
burns if not attended. These types of operations are best accomplished in a fume hood if
possible. It is well recognized that fume hood space is a problem and is the main obstacle to the
approval of otherwise worthy research projects at CAMD. Although if have 2500 sq ft, space is
limited.
Also the addition of more people to the cleanroom roster creates potentially more problems.
Peripheral vision is limited and can pose a significant risk in a crowded environment.
As can be observed from the above picture, the cleanroom is a crowded environment. Every
conceivable space has been utilized. Prior to the construction of the second cleanroom, utilities
and other perforations were made to accommodate each specific piece of equipment. This is why
most of the equipment is permanently installed. This makes it difficult for people wishing to work
on the stepper or to use the sputterer as shown in the right hand figure.
These difficulties make it imperative that cleanroom users be aware of economy of space. A
corollary to this is that users must practice good housekeeping, and limit both the quantity and
variety of materials brought into the cleanroom. To this purpose, a list of commonly used
chemicals has been developed. The admission of materials not on this approved list is strictly
regulated.
Use of the spinner requires a full face mask since loss of the vacuum causes the wafer to shatter
into many pieces which could cut the face as well as injure the eyes. Carts are available for the
disposal of used chemicals. No chemical may be placed on this cart without being properly
labeled. As part of the university community, CAMD has a responsibility for each chemical from
"the womb to the tomb". Mis-labeling or lack of labeling o Chemicals used in the cleanroom
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significantly increases the cost of disposal and may lead to the forfeit of cleanroom privileges.
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