Process Guidelines rev. 1 (1063229), страница 5
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Do not take packing materialinside.•Only clean room paper and notebooks are allowed. No regular labnotebooks!40Basic Photoresist Processing Techniques•Newspapers may not be brought into the clean room.•Clean off equipment, parts, tools, etc. before bringing them into the lab.•No backpacks, canvas bags, etc. are allowed in the lab.•No food and no gum is allowed.•No musical distractions (stereos, walkmans, etc.).7.1.2 Safety Glasses:Safety glasses must be worn in the CNTech Clean Rooms.
Safety glasses may beremoved for brief periods for use of the optical microscope.7.1.3 Clean Room Apparel:We gown in full “bunny suits” with full hoods, boots, and gloves. Put it on asinstructed (there are guidelines in the gowning area) and enter the clean room. Ifyou will be a frequent user, you will be assigned a cubby. If you are an occasionaluser, please use the “Visitor” suits. A variety of sizes are available. When you aredone, exit and de-gown in the reverse order that you gowned in.
Place your gown inyour cubby. They are replaced every week with a clean gown and hood. Forvisitors, please place your used hood in the “Used Hood” cubby.7.2 Personal Chemical Safety:All operations must be undertaken with the safety of both the individual user and otherusers as the primary consideration. While it may be difficult for some to understand,operating safely is more important than getting your project done, or, in fact, than gettinganything done. Ignorance of the rules, lack of common sense, language difficulties,carelessness, and hast are not adequate excuses for unsafe behavior.7.2.1 Safety Philosophy:We wish to keep the laboratory and informal and friendly place to work. The staffwishes neither to make nor enforce rules unnecessarily, nor to “baby sit” users.
We,like you, would rather be doing science. For the most part, rules on chemical useare formulated on the basis of basic chemical knowledge, the properties of individualchemicals, and common sense. In many cases, rules have been created inresponse to specific incidents of chemical misuse by users. In addition, a large41Basic Photoresist Processing Techniquesvolume of state and federal law covers chemical use in the workplace and disposalof waste.
In spite of rules and staff supervision, primary responsibility forsafety rests with the individual user. A responsible, considerate user with anunderstanding of basic chemistry, common sense, and an instinct for selfpreservation will have little trouble with our chemical rules or chemical safety.Those of you with your own laboratories elsewhere on campus may believe ourrules are restrictive and unnecessary.
We have many users doing many differentkinds of projects. The staff can only oversee operations during the normal daytimehours. Under these conditions, a few inconsiderate users can ruin the laboratory forothers. Actually, those of you who have worked in the real world (i.e. a majorsemiconductor facility) will realize that we impose only relatively minor restrictions onyour activities.A majority of problems, violation, and breakages in the laboratory are the result ofhaste. Graduate students are under a lot of pressure. There is only so much timeand everything needs to be done by yesterday. Haste, however, makes waste, asthe old saying goes. Operating under such conditions, you can waste your samples,waste time and money, get crummy results, break things, and endanger yourselfand others by being careless.
If you do not have time to do things correctly andsafely, with adequate time for thought, please stay home.Your safety in the laboratory is determined not only by your actions but by theactions of those around you. Since the staff is in the laboratory only a small fractionof the time the facility is open, the users are often in the best position to observe thebehavior of others. You are encouraged to point out rule violations immediately tothe offenders, as well as to the staff at the first available opportunity.
Inappropriatereactions by individuals to such corrections should also be reported to the staff. Theaccess of everyone to the facility depends on maintaining a safe workingenvironment. A series of thoughtless chemical violations or a single seriouspersonal injury could result in punitive closing of the laboratory for weeks. We hopethat peer pressure will result in conformance to safety standards where direct staffobservation in not possible.7.2.2 Laboratory Hazards:Our main category of hazard at CNTech concerns “ordinary” wet chemicals, i.e.
theacids, bases and solvents commonly used in the lithography and etching. Use ofthese chemicals is in the hands of the individual user. It is precisely because theyare considered “ordinary” by many users that they present a serious hazard. Thechemicals we commonly use can cause severe burns, tissue damage, organdamage, asphyxiation, and genetic damage if improperly used. Thesechemicals can enter the body by inhalation, ingestion, or absorption (either directlythrough the skin or through gloves) and may have either long or short-term healthconsequences. This also will be covered more in a later section.
In addition,42Basic Photoresist Processing Techniquesimproper use of solvents can result in a major fire. “Ordinary” chemicals are thusdefinitely no hazard free. Users are expected to treat all chemicals with appropriaterespect, and to be aware of all possible reactions which may be created, eitherintentionally or by accident.7.2.3 Sources of Chemical Information:The Materials Safety Data Sheet (MSDS) is a convenient, condensed source forinformation on the properties of any chemical. The MSDS is a federally mandateddocument which must be supplied to you by the manufacturer or seller of achemical.
It contains in summary form, the chemical composition, the physical andchemical properties, toxicology data, and instructions for handling, spill control, andwaste disposal. As a matter of good habit, you should read the MSDS for everychemical that you handle. Let us rephrase that, you must read the MSDS for everychemical that you use in the CNTech labs.Safety data sheets for all chemicals approved for use in the lab are available inQuinn Leonard’s office.
Additional safety data sheets can be obtained throughBruce Neumann at the SRC. The MSDS of some commonly used solvents,developers, and resists at CNTech can be found in the Appendix.A new chemical can not be introduced to the lab without an appropriate MSDS.7.3 Terminology:The following terms are often encountered when reading about the properties of chemicalsand the toxicity of chemicals, for example, on the MSDS. Simple definitions are includedhere to help you understand the properties of common chemicals when referring to theMSDS or other references.
This is not intended to be a complete reference on Toxicologyor Chemical Safety.7.3.1 Chemical Properties Terms:Pyrophoric chemicals spontaneously ignite in air. No source of ignition is needed.They react spontaneously when exposed to oxygen. Silane is an example of apyrophoric gas.Flash point is the minimum temperature of a liquid at which it gives off sufficientvapor to form an ignitable mixture with air. Liquids with a flash point near roomtemperature can be ignited very easily during use.Exothermic Reaction is a reaction which produces heat (releases energy).43Basic Photoresist Processing Techniques7.3.2 Types of Exposure:Acute Exposure as used in toxicology refers to a short-term exposure.
It hasnothing to do with either the severity of the exposure or the severity of the effect.The type of exposure occurring during an accidental chemical spill is properlydescribed as an acute exposure.Chronic Exposure as used in toxicology refers to a long-term exposure. Again, ithas nothing to do with the severity of the exposure, the severity of theconsequences, or the duration of the consequences.
Chronic exposures can be theresult of chemicals in the workplace, the home, or the environment. Chronicexposures are usually the result of carelessness, ignorance, or neglect, and not theresult of an accident.Local Exposure refers to exposure limited to a small area of skin or mucousmembrane.Systemic Exposure means exposure of the whole body or system, throughabsorption, ingestion, or inhalation.7.3.3 Types of Effects:Acute Effects refers to the duration of the symptoms. Acute means symptomslasting a few hours or days.
Again, it has nothing to do with the severity of theeffects.Chronic Effects are long term effects, manifested by prolonged duration andcontinuing injury.Local Effects occur in a small area, at the place of contact.Systemic Effects occur throughout the body, or at least away from the point ofcontact.Allergies and Hypersensitivity are reactions by particular individuals to particularchemicals, caused by heredity or prior overexposure. Hypersensitive individualsshould avoid exposure to offending agents.44Basic Photoresist Processing Techniques7.3.4 Exposure Levels:TLV-Threshold Limit Value-This is actually TLV-TWA (time weighted average) butis commonly called just TLV. It is the averaged level to which you can be exposed 8hours a day, 5 days a week forever, without adverse health effects.
These levelsare set by ACGIH (Governmental and industrial hygienists), and adopted into law byOSHA (Occupational Safety and Health Administration). This level is most relevantto chronic (long-term) exposure to chemicals in the work place. Short-termexposures in excess of the TLV are thus not necessarily hazardous.
This value isnot particularly relevant to our laboratory situation. It is sometimes used as aguideline, however, since short term exposure to <TLV should be very safe.IDLH-Immediately Dangerous to Life and Health-This level represents themaximum value for which a 30 minute exposure will result in no irreversible orescape impairing effects, i.e. the maximum level which will not cause you to passout or sustain irreversible organ damage.
It is the value most appropriate to sudden,one time accidental exposures.STEL-Short Term Exposure Limit-Actually TLV-STEL. Maximum concentration towhich you can be exposed for 15 minutes, up to 4 times a day without adverseeffects.PEL-Permissible Exposure Limit-The statutory equivalent of TLV.LD50- The dose at which 50% of those exposed will die. Separate levels apply tovarious modes of exposure (inhalation, dermal, etc.).
Usually expressed in terms ofmg per kg of body weight; often measured for mice and rats, for obvious reasons.All these levels are approximate, with considerable inconsistency between varioussources. It is obvious that one cannot do well controlled experiments on humansubjects. It is thus wise to be conservative in estimates using these numbers.7.3.5 Toxic Effects:Carcinogen-A substance producing or inciting cancerous growth.Mutagen-Capable of inducing mutations.Teratogen-A substance causing damage or death to a fetus.45Basic Photoresist Processing Techniques7.4 Chemical Use:7.4.1 Chemical Authorization:Only specifically authorized chemicals may be used in the laboratory.
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