Cleanroom Training Overview
This page 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.
Why Safety Training?
- 6,000 fatal workplace injuries per year
- 50,000 deaths due to chemical exposures
- 6 million non-fatal injuries
- Injuries alone in excess of $110x109 per year
- Information reduces risk
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 hazardous. There are many different types of chemicals, each with there own particular associated hazards. A glossary of terms follows.
Cleanroom Laboratory Safety Training
- Provides a safety net
- Assures everyone is qualified
- Identifies cleanroom hazards
- Train individuals - status change
- Cleanrooms are moving towards a user facility - standardization needed
- Cleanroom worker certification
- ID all equipment
- ID dangers of all equipment
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 implemented 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.
How to Manipulate Materials
Cleanrooms are controlled environments in which each action is controlled and well thought out.
Toxic chemicals make you sick if you breathe, 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.
For Emergency, dial 911 or campus police
- Secure equipment
- Process and evacuate the cleanroom
- Report all accidents immediately
- Use ph paper to test
- Cleanup: Always use Neoprene gloves, especially in fume hood
- Always rinse well with water
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). Combustible substances are those that will burn above 100F. 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.
Cleanrooms offer special hazards
- Chemical use - processing and etching with strong oxidizers. Always check the MSDS Sheet when using a new chemical.
- Always have a mentor when using a new piece of equipment.
- If unsure about the procedure, STOP, and ask for help from someone who knows.
Incompatible describes chemicals which react dangerously when mixed or used together. When one reads an MSDS sheet, the mg/m3 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.
Reduce Worry: Go the Extra Mile
- Always leave equipment in at least as good condition as you found it.
- The last person out verifies that all machinery is left in a SAFE(off) position, and that all water has been turned off.
- Mentor responsibility: Always show the best example, even if in a hurry.
- Careless activities can result in lowered expectations both for you and others using the cleanroom.
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.
Carelessness in the use of a piece of equipment may carry over to other processes and may endanger personnel and/or equipment
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
- Good housekeeping is integral to a safe environment.
- Cleanroom rules are there for your protection and the safety of the equipment. Disregarding these rules can have long term consequences.
- Carelessness, or blatant disregard of such rules may lead to the suspension of cleanroom access.
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 canít 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 asphyxiating 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.
Chemical use at CAMD
- Must supply the MSDS - If chemical is not restricted to the cleanroom, you must discuss it's use with CAMD Safety. New chemical approval is handled through Lorraine Day and CAMD Safety.
- NFPA Labeling - LAbeling is required for all chemicals before placing them in storage or bringing them into the cleanroom.
- Handling Chemicals - Never hand - carry any chemical. Place them in a bucket or on a cart.
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: 225 - 578 - 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.
Haste makes waste
When working with chemicals, dangerous processes or equipment, ALWAYS TAKE YOUR TIME. The potential for accidents and injury is substantially increased when manipulations are rushed.
When doing a new procedure, always make a dry run first to determine any bottlenecks or potential dangers.
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 first. 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.
Fume Hood Safety
- Turn hood on before you open any chemicals.
- Work with the sash pull down at least part of the way.
- Report any suspected deficiencies.
- Pick up spills immediately, and then rinse thoroughly with H2O.
- Do not store chemicals in the fume hood.
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 donít forget to request it when ordering. Aldrich is especially difficult in this regard.
- 0 = minimal or no hazard
- 1 = slight irritation
- 2 = moderate - protective measures are required
- 3 = serious - don't expose any body surface
- 4 = severe - any exposure could be life-threatening(i.e. HF)
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. The BLUE diamond in the NFPA symbol identifies HEALTH hazards.
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 manufacturerís 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.
- 0 = will not burn
- 1 = flashpoint > 200F - preheat to ignite
- 2 = flashpoint < 200F - moderate heating may ignite
- 3 = flashpoint < 100F - flammable, volatile, or explosive under most normal conditions
- 4 = flashpoint < 74F - very flammable, extreme caution should be used in storing or handling these chemicals.
The RED diamond in the NFPA symbol identifies FLAMMABILITY hazards. 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 have a flammability rating of 0. Those chemicals which have a flashpoint above 200F. have a flammability index of 1. If the flashpoint is >100F. but less than 200F., then the chemical is given a rating of 2. Substances which are volatile or even explosive under most conditions and have flashpoints below 100F. receive a rating of 3. Finally those chemicals whose flashpoints are below 740F. (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.
- 0 = minimal, stable
- 1 = slight - may become unstable at elevated temperatures or pressures
- 2 = moderately unstable - potentially violent reactions at normal or elevated temperatures or pressures
- 3 = serious, explosive - capable of detonation by strong initiating source, such as heat, shock, or water
- 4 = severe - may detonate at normal temperature or pressure. Evacuate if exposed to heat or fire.
The YELLOW diamond in the NFPA symbol identifies REACTIVITY hazards. 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.
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.
Substances with which a particular compound is incompatible, e.g. H2S with strong oxidizing agents.
Shown to the left is the most common symbol - incompatible with water.
Always read the MSDS sheet for non-compatible materials when working with a new chemical
The final diamond in the NFPA symbol 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.
- All Chemicals must be labeled.
- Fume hoods are not for chemical storage.
- Always use the minimum you need.
- Always wipe up spills before proceeding.
- The number one safety rule is: Proper Housekeeping
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.
- CAUTION: INSULATED GLOVES REQUIRED
- DANGER: EYE PROTECTION REQUIRED
- Always wear proper closed shoes when using cryogenic liquids.
- If liquid spills on foot, DO NOT MOVE! Call for help.
- Remember, we have a buddy system in place.
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.
Safe Handling of Compressed Gasses
- For cryogenic liquids, wear goggles, thick gloves, and closed shoes.
- Carry all cylinders in their appropriate cylinder cart.
- Secure cylinders before removing the protective cap.
- Use the correct regulator for the appropriate gas.
- TAG and report and damaged regulators. DO NOT USE!
- Open cylinder valve completely, control flow via the regulator.
- Hang a cylinder shut-off valve sign on the appropriate valve.
- Remember that He/N2/Ar, and O2 are compressed gasses too.
- All processing equipment in the cleanroom is supplied with N2. Breaking a nitrogen line can cause asphyxiation. Never leave the line unattended.
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.
DOE Facility Problems
Two thirds of all the root causes of all compressed gas cylinder accidents at DOE facilities include human error, management and procedural problems. 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.
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.
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". Mislabeling or lack of labeling of Chemicals used in the cleanroom significantly increases the cost of disposal and may lead to the forfeit of cleanroom privileges.
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with any questions you have regarding the Cleanroom and Cleanroom Safety.