Megahits and Megabits from CleanRooms `96 West
By Susan English and Lisa Karter
Technology Roundup from the Conferences…
Santa Clara, CA–CleanRooms `96 West in October delivered information on new contamination control technology and products that included new gas purification techniques and ultra clean gas technology for semiconductor manufacturing. Also featured at CleanRooms `96 West was a day-long conference on ultrapure gas and gas delivery systems.
During this conference session, Ultrapure Systems, Inc.`s Brian Warrick, an analytical services manager responsible for developing new gas purification techniques, discussed a new generation of inert gas purifiers with room temperature operation.
A new catalyst, absorber, getter (CAG)-type purifier uses a combination of three materials to remove all active impurities from an inert gas stream. According to Warrick, the new room-temperature technology has a high capacity for impurity removal, removes a wide range of impurities, and does not generate impurities within the purifier. The CAG combination has proven effective in removing moisture, oxygen, carbon dioxide, carbon monoxide, hydrogen and hydrocarbons from unpurified liquid nitrogen or liquid argon sources.
The first stage of the purifier uses a nickel “catalyst” on an inert support to remove moisture and other impurities from the feed gas. Because nickel has a limited capacity of removing carbon dioxide, the second stage of purification is a molecular sieve absorber which is used to remove carbon dioxide and excess moisture. The third stage of the purifier uses a non-evaporable getter alloy operating at room temperature. Because the first two stages are used to prepurify the gas, the room temperature getter is allowed to work in its optimum performance range.
During another presentation representatives of Tohoku University, under the wing of Professor Tadahiro Ohmi, discussed concepts of ultra clean gas technology for semiconductor manufacturing: One, specify the gas supply system. Two, remain outgas free and catalytic behavior free–all valves and mass flow controllers are plastic-free and made entirely of metal. Three, use advanced metal gasket-type fittings. Four, use 100 percent chromium passivation treatment that has non-catalytic properties and can improve dry-down properties and offers high corrosion resistance. Five, use the proper sealing method for fittings and blocks. Compact metal gasket-type fittings can resist external leaks even at low torque. This should be adopted for assembling a gas system.
Finally, the Ohmi Laboratory confirmed that dry down properties of less than 1 ppb of Argon gas purging at room temperature can be obtained if the gas lines are made of all metal-type components and all wetted surfaces are treated with 100 percent Cr2O3 passivation. Ohmi Laboratory constructed this compact ultra clean gas supply system for W-CVD processes. The system was made by using an advanced type of fitting and connection method while all wetted parts were treated with Cr2O3 passivation.
In a session geared toward novice gas handling/delivery users, Dr. Sowmya Krishnan, manager of technology and applications development at Ultra Clean Technology (Menlo Park, CA) presented a seminar on the basics of gas handling. Said Krishnan, “Higher process yields and better ROI are the driving force behind every leading semiconductor fab house…A study is presently under way to determine if superior contamination characteristics of a gas delivery system have a significant impact on process yields. Preliminary results from the study suggest there is an important qualitative and quantitative increase in gate oxidation process yields.”
One of the biggest culprits of gas impurities and contaminants is the gas delivery system (GDS) that supplies semiconductor gases to the process tool. While gas purity levels have dramatically improved over the last decade to a point where they often exceed the detection limits of sophisticated test instruments, advances in gas delivery systems have lagged behind. The GDS typically consists of gas manifolds, mass flow controllers, valves, pressure sensors, and interconnect tubing. The GDS is located between the point-of-use (POU) purifier and the process tool. It regulates the flow of inert and reactive gases for manufacturing semiconductor films. According to Krishnan, “research has shown that various components, materials, and manufacturing processes in conventional gas delivery systems are prime sources of contaminants.
Product Roundup from the Show Floor…
“The washing machine will never be the same again…” Or, so says Extreme Automation Technologies. The company is touting its newest invention–the first washing machine built for cleanroom laundries. Because many companies started a cleanroom laundry business as an offshoot of their uniform rental/laundry service, existing washers and dryers were retrofitted to accommodate the new cleanroom segment of their business.
Extreme`s High Purity washing machines include a patent-pending Particulate Process Control (PPC) program, which the company says enhances cleaning efficiency and reduces water consumption. The washers feature PLC computerized controls, touch-screen operator interfaces, Teflon-coated wetted parts, a high speed extract process, which reduces rinse cycles and saves money.
New air filtration technology launched
A new alliance between Hoechst Celanese Corp. (Charlotte, NC) and Filtration Group, Inc. (Joliet, IL) to manufacture and market air filtration cartridges based on new patented technology to reduce AMC was launched during the CleanRooms `96 West Conference and Exhibition. Based on Hoechst`s patented Celbond Particulate Structure (CPS) technology, the new air filter cartridges for HVAC/process air and other OEM applications are available from Filtration Group under the AQF product name. Initial target markets include microelectronics, pharmaceutical, food and beverage, industrial processing, hospitals, laboratories and all types of cleanrooms.
Introducing the new product line at a special invitation-only conference, Gunter Groeger, a Hoechst Celanese Research Associate, reviewed the AQF technology, the analysis of contamination breakthrough curves based on Dynamic Filter Testing, and its significance to the microcontamination industry.
Minienvironment helps shrink clean manufacturing costs
Certified to Class 1 at 0.1 µm (unoccupied), StratoTech Corp.`s StratoClean Mini-Environment is completely self-contained, portable and transportable from crate to operational clean environment in a matter of hours. Linkable back-to-back or side-to-side to support continuous flow manufacturing, the 5 ft long ¥ 3 ft deep ¥ 8 foot high Modular CleanCell has its own filtration system, process utilities, tooling surface, and auxiliary equipment hookup. The company says up-front capital investment on clean space can be minimized by incrementally adding or subtracting StratoClean Mini-Environments. n