Safe Handling ofExcimerLaser Gases

The past decade has seen a pro­ used in the laser industry have pres­ tained and vented, one must qUickly found increase in excimer laser use. sures typically between 300psi and ascertain what went wrong and Processes using excimer laser~gen~ 3(x)()psi. At these pressures, an acci~ what laser gas is escaping into the erated UV wavelengths are now be~ dent causing the cylinder to fall room. Then make sure the ventila~ coming standard in semiconductor could shear an unprotected valve, tion system is on and that all person­ fabrication, materials processing causing the cylinder to simulate the nel are removed from the area. Don't and medical procedures. With the action ofan ungUided missile. A sec­ try to be a hero and stop the leak ofa proliferation of these refillable gas ond hazard also underestimated by toxic gas. lasers, the industry must not side­ laser gas users is found in the seem~ If anyone was exposed to toxic step or ignore a critical issue in their ingly benign gases such as He, Ne gases or shows evidence of suffoca~ successful utilization: that of safely and AI which can act as suffocants tion due to the lack of oxygen, ad­ storing and handling laser gases, It due to the displacementofoxygen. minister fIrst aid (Table I) and call a is in the best interests of the laser The two hazards most often asso­ physician immediately. community to fully understand ciated with the use of excimer gases First aid for inhalation of fluorine, what precautions should be taken to are the corrosivity and tOXicity ofthe hydrogen chloride and even carbon avoid serious accidents involving halogen component. Fluorine and dioxide laser mix, if it was severe the use ofcompressed laser gases. hydrogen chloride gases are by far enough to cause loss of conscious~ Excimer lasers are currently found the most common halogen donors in ness, is nearly identical. If breathing in many universities. corporate re~ excimers. Extreme care should be is labored, give 100% oxygen under search facilities and government lab· taken when handling these prod­ positive inhalation pressure for half­ oratories. The safety record from this ucts. Both gases, ifnot properly used hour periods every hour for six pool of predominantly scientific reo and safely stored, can be devastst­ hours. If the patient is not breathing, searchers has been reasonably good ing. They are irritants of, tlle upper give artificial respiration. The patient " to date. This positive record is more respiratory tract and can caus,e pul­ should be kept warm, not hot, and a function ofluck than safety proto­ monary edema. Exposure to- high stay under the supervision of a phy­ col, however. The typically well edu­ concentrations of either gas, even if sician until the danger has passed. cated users ofthese lasers often neg~ only brief,jis usually fataL Mild, di­ First aid for halogen mixes which leet or disregard the basics in gas cyl­ lute expqsures will result'in cough­ ontact the skin and eyes is to subject inder handling and storage. ing anq"ehoking and burning of the the person immediately to a drench­ Picture this scene when entering a eyes atld nose. Vapor contact with ing shower with all clothing being university laser lab. There is an exci­ the skin will cause tissue irritation removed as rapidly as possible. With mer laser in a small room, cramped and necrosis. Although not usually fluorine exposure, the skin should be in next to an optics bench. Gas cylin­ present in the pure fonn for this ap~ washed with 2~3 % aqueous am· espe~ ders seem to be everywhere, plication, liquid Hel or F2 can cause monia solution and then "flushed cially under foot. Tygon or copper painful bums of the tissue and bone with water again. Compresses that tubing exiting from broken gas regu­ ifthey come in contact with the skin. include saturated solution of Epsom lators to the laser ports look more These effects are real and are not ov~ salts or iced 70% alcohol should be like spaghetti than a gas delivery erstated for effect. applied for at least 30 minutes as system. Sophisticated toxic gas In the event of an accident with well. Check with your specialty gas monitors, otherwise known as grad~ pure HCI or F" follow the emergency supplier for more details. For HCI uate students, let the visitor know steps shown in Table I. In addition, contact, flushing with water only is that there is a hint of fluorine in the special fIrst aid preparations for F2 recommended. BE SURE TO RE­ air (as ifone didn't smell it already!). burns should be used immediately. CEIVE THE ADVICE OF A QUALI­ Ventilation systems, ifthey exist, are These include magnesium oxide & FIED PHYSICIAN QUICKLY. not utilized properly. glycerin paste, as well as a 10% cal­ Make sure the gas has completely Before we make specific safety rec­ cium gluconate solution for injection dissipated before re-entering the lab. ommendations to rectify the situa~ under the skin (after use of local After donning clean neoprene tion in this stereotypical lab, it'vould anesthetic) to halt tissue decay. gloves, coat. boots, and a self-con­ be helpful to discuss the hazards as­ Another problem these halogens tained breathing apparatus, enter sociated with excimer laser gases. pose is the corrosive attack on labo­ the lab and inspect the damage. Iftt A multitude of hazards are asso­ ratory equipment. Of the two gases, was a halogen gas that vented, re­ ciated with handling laser gases, in­ HCI is the more destructive. If an HCI move the cylinder and then system­ cluding high pressure, asphyXiation, mix were to vent accidentally, every atical
y clean away the fIlms of hy­ toxicity. and corrosivity. The gases piece ofelectronic equipment includ­ drofluoriC or hydrochloric acid that typically used vary with laser type ing computers and telecommunica~ will have formed on all the equip­ and manufacturer. However. all exci~ tions eqUipment would be ruined. ment. mer lasers have fIll gases comprised Optical components and other spe­ of halogens including either HCI, F, cialized equipment in a laser lab Preventionofaccidents ; includ~ The two key ingredients qf pre­ or sometimes NF3 rare gases would also be adversely alfected. ing Xe, Kr or Ar: and a buffer gas of venting accidents involVing laser He andlor Ne. Incase ofaccident gases are (I) properly educated and There are hazards common to all If precautions are not heeded, acci~ trained personnel, and (2) suitable ofthe above gases, but the one most dents can and will occur. Ifa rapid or safety equipment. overlooked and underestimated is violent release of any gas occurs The aforementioned hazards can the high pressure itself. All cylinders from a cylinder not secured, con~ be aVOided if one adheres to the fol- Reprintedfrom the 1990Photonics Design and Applications Handbook © Laurin Publishing Co,. Inc, Safe Handling of Excimer Laser Gases Lasers Lasers Safe Handling of Excimer Laser Gases lowing rules for the safe handling of ,--"------.... compressed gases. These rules are speclflcally applicable to the laser lab TABLE l. and include: 5% F, MIX OR 5%HCI MIX • When moving gas cylinders, use EMERGENCY FIRST AID GUIDE TO INJURY a hand truck designed for gas cylin­ CAUSEDBY EXCIMER LASER GASES He ders. Cylinders, especially those in XeOR Kr halogen service, should never be rolled, dragged or dropped. SYMPTOM/CAUSE EMERGENCY FIRST AID STEPS • Cylinders should be secured at all times, and protective caps should be attached over the cylinder valve Suffocation due to when not in lise. lack ofoxygen • Always know what is in the bot­ iii Labored breathing Administer 100% 0, at half-hour intervals for tle; don't ever assume. 6 hours. • Use proper equipment and com­ patible CGA fittings and regulators. Dedicate equipment to a single ser­ • Not breathing Artificial respiration. vice. - • Purge systems shouid be incor­ In both cases keep warm, nol hot. Keep un­ porated into most gas-delivery con­ der qualified physician'scare until danger LASER figurations. The purpose is twofold: has passed. (a) For toxic and corrosive gases, purge gas is to be used as an advance - leak check: Ib) Purge gas is also used to keep the gas system clean and free Halogen contact with This is first aid for a worst case situation... of atrnospheIic contaminants when skin modify as needed. installing the system and during subsequent cylinder changes. • F,gas exposure 1. Drenching shower. Remove all ciothing • When connecting cylinder(s) to a as soon as possible. gas~delivery system. make sure there are no leaks. If there is a leak, tighten the connection oniy after the 2. Wash skin with 2%-3% aqueous purge gas is vented to lessen the ammonia soiution. VACUUM PUMP pressure. • Make sure all construction mate­ 3. Flush skin with water again. rials in your system are compatible with the gases being used - pariicu­ larly important when handling fluor­ 4. Apply compress of saturated solution of TOXIC GAS ENCLOSURE ine. an oxidizer. Epsom salts or iced alcohol for at least eSafety equipment such as toxic 30 minutes. gas monitors, protective clothing and glasses, and breathing appa­ 1. Drenching shower. Remove ali clothing ratus should be readily accessIble. • HCI gas exposure Figure 1. as soon as possible. No other steps are Schematic ofa safe high-puritygas delivery system. and all personnel should know how recommended. to use them. • Forany other assistance or ques­ because it will safely vent any leak, tions. don't hesitate to call your spe­ Halogen contact with Call emergency vehicle. exhaust flow to prevent diffusion of A completeexcimergashandling cialty gas suppliers...they are the ex­ with eyes (Besl medicine = prevention) any leaked gas back into the room. A system minor or catastrophic. This system perts. They can and should supply vented cabinet should be designed to In addition to all the safety reqUire­ incorporates a ventilated safety cabi­ you with Material Safety Data Sheets allow the user to close a cylinder ments listed above, a gas handling net (not shown) to hold two halogen (MSDS). They will also familiarize valve without allOWing any gas to en­ system for excimer laser gases must miXes, helium as a buffer and purge you with what equipment is typi­ BE SURE TO RECEIVE THE ADVICE OF A QUALIFIED PHYSICIAN ter the room. offer fleXibility and ease of use. All gas, as well as Xe and Kr. Made of 3. Replace hoses or tubing to meet these requirements are met by the II-gauge steel, the cabinet comes cally used with certaln gases. Expect AS SOON AS POSSIBLE the best products and information the follOWing recommendations: For three-panel system shown in Figure with locks. automatic door closures. from yoursupplier. F, or HC I ml" (up to 10%), use high­ 1 (designed by Spectra Gases Inc.). s1?rinkler head and cylinder brack­ Since the issues of safety are most finish, clean. stainless steel tubing This dual-halogen system (very often ets. An air flow velocity of 75 fi/min. acute when dealing with halogens (high-pressure copper tubing is ac­ both HC 1 and F, spectral lines are is maintained through the cabinet. Have emergency telephone numbers easily accessible. ceptable for F use, but is not pre­ used in research situations) has the Experience has shown that a used in excimer lasers. we will now 2 give pariicular emphasis to equip­ ferred due to its softness). For inert unique safety feature of isolating the nickel-plated brass, 316 stainless ment for handling excimer gases Ambulance _ Fire Dept. _ gases, use high-pressure copper, halogen panels from each other. The steel. or monel regulator that incor­ safely. To rectify the unsafe lab con­ brass, or stainless steel tUbing. purge hose must be switched man­ porates a positive seal. often referred to as a tied diaphragm, works best ditions earlier described, the foiiow­ Safefy_...... t.2~2.~'2.::..'=2..'-- 4. Inspect your monel, stainless ualiy from one halogen panel to the ing cost-effective steps should be Doctor Corporate __ steel, or nickei-plated regulators that other when a new spectral line is to for halogen service. The design pre­ taken. have been in corrosive gas service. If be used. This offers the ultimate vents creep even when particles 1. Secure all inert compressed-gas there is any evidence of a problem. safety precaution: Even if valves fail, have accumulated on or around the cylinders with brackets to stabie HALOGEN EXPERTS: SPECTRA GASES INC. arrange for repair by your supplier. there is never an opportunity for seat. When being used as pari of a cabinet system, regulators are benches or walls. 1-800-932-0624 (in NJ: 1-201-372-2060) 5. IncOIporate the use of either a fluorine to come in contact with hy­ 2. Secure the halogen gas miX­ cross-purge or deep-purge (dual-pig­ drogen chlOride. mounted on a panel to avoid damage tures in either a fume hood or vented tall) system for each halogen gas The cabinet is the most important when moving cylinders in this con­ safety enclosure which has suffiCient being used. element ofyour gas handJing system fined area. An additional advantage Safe Handling of Excimer Laser Gases Lasers

TABLE 2. FACTORS DETERMINING DESIGN OF EXCIMER GAS DELIVERY

Applications Work Projected Gov'l Sately Environment Power&. Regulatory Duration Bodies Materials Production Varied­ OSHA processing floor, probably (Le.: micrO' Multiple excimer '- continuous machining system (24 hr/day. of plastics 6-7 days/wk) &melals) Medical Hospital or Varied­ FDA procedures outpatient usually short OSHA (Le.: laser clinic, duration angioplasty) Operating room (sec to hours) Semiconductor Clean room Varied­ OSHA processing probably (Le.: photo­ continuous lithography)

is the abiltty to see and adjust panel­ before a cylinder is removed, or additional factors to consider in mounted regulators easily. Either a when the system is on extended designing a safe gas-handling high-pressure flexible hose or a stain­ shutdown. system. less steel pIgtail (coiled tubing) con­ Every panel should be clearly la­ nects the cylinderto the regulator. beled and easy to use and maintain Summary A control panel has two major in working order. In conclusion, excimer-based sys­ functions: the safe delivery of gases Additional safety equIpment may tems are now realizing their poten­ to the point of use and the preven~ be required by state, local or corpo­ tial. They may alter the need for eye­ tion ofsystem contamination during rate regulations. These options may glasses and heart bypass surgery, cylinder exchange. Safe delivery of include: Improve Ie manufacturing, and help the gases is assured by carefully se­ • toxic gas detector make possible rapid strides In the lected components to reduce and • emergency shut-down system manufacturing of thin-film sub­ control pressure, to control flow and (electropneumatic controller) strates for superconductors. These to eliminate potential leaks. • halogen scrubbers are just a few of the new markets The user gains several other im~ • flow restrictors in the cylinder that are currently using excimer las­ portant benefits by using a purge valve. ers. For excimer-based systems to be system: Systems can also be partially successful in these fields, the issues • leakcheck new connections or fully automated, with local or ofgas safety must not be ignored. • prevent air from contaminating remote controls. Automation is most Al Dietz & the system dming cylinder changes often a corporate safety requirement Elaine Bradford • purge toxic gases from the lines in production situations. Table 2 lists Spectra Gases Inc.

KEITH DARABOS Technical Product Specialist

SPECTRA GASES, INC, 277 Coit Street Irvington, NJ 07111 201-372-2060 / 800-932-0624 FAX: 201-372-8551