Minienvironments Gear Up
Borrowing technology from the pharmaceutical industry, minienvironments can be adapted to process everything from steppers to masks, from CDs to optics.
By Susan English
Minienvironments and microenvironments are a direct development of the science of isolation technology, providing clean air space and the protection of tool and process environments from contamination, while ensuring the untrammeled flow of clean air around critical product areas. Equipped with exhausts to remove contaminants from the enclosure, minienvironments allow users the flexibility to assemble or manufacture contamination-sensitive products in a contamination-free area at Class M 1.5 or better. Their modularity means they can be added to an existing cleanroom or used within an area that needs an upgrade in cleanliness level. In the semiconductor industry, minienvironments have been widely used in wafer processes such as steppers, tracks, chemical/mechanical polishing, etching, chemical vapor deposition, and in some areas, as reticle stockers for storing photomasks.
Intelligent Enclosures Corp.`s iE Air Division, (Norcross, GA) designs and builds minienvironments for Class 1 or better at 0.16 µm, ranging from simple, low-cost single-pass units to technologically advanced recirculating units, where temperature and relative humidity within the minienvironment are precisely controlled. They are designed for applications such as lithography, compact disk/flat panel display, CMP, material handling, wafer reticle handling and storage, photomask, wet benches/exhaust and air handling. Intelligent Enclosures`s minienvironments include precision HVACs, ranging from R22-based DX-coil to desiccant based, and providing the very low humidity environment required by some photomask and CD manufacturers. All units are capable of controlling temperature and humidity stability at ۪.1F and ۪.5 RH. In most cases, the company performs detailed simulations and physical modeling, including computational fluid dynamics, on all units.
Its Total Control CoatGuard 2000 Mini-environment is a fully isolated, ultra-clean, recirculatory enclosure system with very tight controls for temperature humidity and ESD. Ideal for protecting spin-coat processes in the compact disk, microelectronics and semiconductor industries, the patented system provides a Class 1 or better (at 0.12 micron) contamination-free environment. The stabilities of the temperature and relative humidity inside the minienvironment are ۪.05C and ۪.5 percent RH. A modular system, the CoatGuard 2000 can be configured to accommodate a variety of installation requirements. The CD-Guard 2000 is a fully isolated, ultra-clean (Class 1 at 0.12 µm), recirculatory enclosure system used for compact disk coating and developing processes. The LithoGuard 2000 protects lithography processes.
iE Air`s Ergo-Guard Manual I/O Isolation System encloses product load/unload stations for semiconductor and CD manufacturing equipment. System performance meets 0.25 wafer environment control requirements, with less than 0.1 PWP during a load/unload cycle. The company`s airflow management, supported by computer modeling, provides isolated zones to manage and separate “clean” and “dirty” operations within the enclosure. The system is capable of operating at Class M1 in environments ranging from Class 100,000 to Class 1. Options include bag-in bag-out product transfer stations, glove port access, static charge control, wheels, and a wide range of finishing materials.
Minienvironments from Liberty Industries (East Berlin, CT) allow for control of temperature, humidity, pressure and particulate contamination, as well as gaseous ambients such as nitrogen or argon. Liberty engineers work closely with the user to determine the design to meet the situation — everything from size to mobility.
Clestra Cleanroom Inc. (North Syracuse, NY) designs and manufactures minienvironments to accommodate the specific requirements of the process tool. Its custom-built minienvironment is a completely tool integrated, self-contained unit that provides for a table-height work surface, which allows easy access to the front of the tool. The unit utilizes fab chilled water cooling, and chillers, dehumidifiers and humidifiers for extreme conditions. The minienvironments come complete with standard PID controls, makeup air prefilters, Class II forward-curved centrifugal or plug fans, and require only three connections (electrical, condensate drain and condenser or chilled water). Clestra`s team will work with the process tool manufacturer from initial design concept through construction.
The PRD-1000 minienvironment from General Air Corp. (Chatsworth, CA) is a new environmental control package. It is designed for use where minienvironments using conventional refrigeration and air-conditioning methods are unworkable. The new method provides dehumidification via desiccants in photoresist deposition applications, where tight environmental control conditions of temperature and humidity are required. It takes up very little space and can be packaged in relatively small enclosures of various shapes and sizes. The chamber desiccant dehumidification method requires very little maintenance and is guaranteed to provide a 99.8 percent annual “up-time,” operating continuously 24 hours a day at Class 10 or better. One feature is individually set temperature and humidity controls capable of controlling temperature and humidity — 35 to 55 percent RH @ 50 to 73F.
The “clean tunnel” minienvironment approach to automated wafer transport systems is represented by Design Station (Eden Prairie, MN). With each tunnel project, the company considers construction issues such as fire door mating, variable ceiling heights, power requirements, lighting, heating, ventilation and air-conditioning, static control and seismic requirements, as well as architectural integration within the building. Solid panels are a 3-mm Class 1 conductive aluminum polyethylene composite, while transparent panels are made of a static-dissipative-grade acrylic or polycarbonate. Aluminum extrusions are manufactured of Alcan 66080 HO alloy, sulfuric acid architectural anodization with satin (clear) finish. The ULPA filtration module comes with a disposable prefilter in a filter plenum size of 23.56 in. ¥ 47.56 ¥ 12 in. and a 120-V single-phase, 3-wire electrical system. The company also offers stand-alone and modular minienvironments.
Channel Systems Inc. (San Leandro, CA) Clean Room Channel Wall is designed for environments Class 1 and above. The key to its system is the Clean Room Channel Stud (CRC-100), a one-piece structural framing member which is stronger than 1.625 ¥ 1.625 in. 12-gauge steel channel framing, but made entirely of non-ferrous aluminum. Its flexible design allows framing with unlimited changes because there is no drilling or screwing of trim to framing or inserts. The Stud accepts the panel, which is retained by an air-sealing glazing spline. Any type of panel may be used — from 0.125-in. wide to 0.25-in. wide, aluminum honeycomb, composite panels, polycarbonate, even-tempered glass. The Clean Room Channel Wall may be incorporated with any air filtration system. The company`s patented Chameleon Micro Environments include soft wall, hard wall or vision, vertical or horizontal flow combinations with or without temperature and humidity control. Class 100 rooms usually cost below $100/ft2.
HEMCO Corp. (Independence, MO) is introducing the Robotics Chamber, designed for automated processes and delicate or hazardous procedures. The positive-pressure enclosure tent surrounds Class 100 air in the HEPA-filtered model, which removes particles as small as 0.03-micron, while ULPA and carbon filtration systems provide negative pressure to vent fumes and vapors or recirculating air and temperature and humidity controls. An important feature is the three-way viewing and access capabilities. The chamber can also be designed as a portable unit and integrated with existing equipment in the lab. A variety of accessories are available, including lighting, plumbing and electrical services, work surfaces, transfer boxes, and glove ports.
One company which integrates process air control, minienvironments and enclosure technologies is Semifab (Hollister, CA). Semifab provides minienvironments that are designed to provide SMIF-alternative, Class 1 environments for the manual loading and unloading of products into and out of production tools. The Semifab Manual I/O features a Class 1 load/unload environment, less than 1 particles per wafer pass performance, reduced energy consumption and other cost-saving features, according to the company. In April 1996, Semifab and Empak, Electronics Division (Chanhassen, MN) signed an agreement to develop and market a new inert purge technology designed to “enhance the surface condition of silicon wafers throughout the semiconductor manufacturing process,” according to Semifab. The new system, that was developed by Semifab and dubbed Inertra, includes inert gas distribution, microfiltration and point-of-use delivery that is fully compatible with Empak`s wafer carrier/pod technology.
Simplex Strip Doors Inc. (Fontana, CA) uses Mini Airlock modular rigid, framed panels, which latch together to create laminar flow micro-isolation chambers for protecting critical processes from personnel and equipment. Frames can be anodized or powder coated and are adaptable to a variety of HEPA or ULPA filtration units. The “Novel” Polysim panels are flexible, scratch resistant, static dissipative, non-outgassing and contain no residual solvents or non-critical additives. The company makes many other panels in flexible, clear, colored, antistatic vinyls and rigid acrylics, lexan and metal.
Environmental Specialties Inc. (ESI; Raleigh, NC) has a complete line of freestanding, 33-ft3 Reach-in Environmental Chambers to complement their Walk-In/Step-In Environmental Rooms. The ES2000 Environmental Chamber creates precisely controlled temperature and/or humidity for product testing, storage, incubation and controlled illumination for growth studies or material testing. Horizontal airflow allows for even air distribution and reduces the dead zones associated with product loading.
ESI has expanded its designs into a smaller bench-top series and a larger double-door unit. The ES2000 can be mounted through a cleanroom wall to create a minienvironment separate from the host cleanroom facility. Custom designs include NEC Class 1 Div. 1 or 2 interiors for flammable storage; HEPA filtration to create a reach-in classified interior that will match or exceed the rating of the area; and remote control/monitoring for operator interface outside the cleanroom. The company is currently completing a listing program with a national testing laboratory to allow all ES2000 standard products to be labeled/listed for electrical compliance under stringent test procedures.
M. Braun Inc.`s (Newburyport, MA) Labmaster 100 Glovebox minienvironment is stainless steel with radius corners and moisture and/or oxygen removal to less than 1 ppm. It measures 48 in. ¥ 31 in. ¥ 35 in. and is available in double and triple lengths. Its enhanced HEPA filter system enables it to meet cleanroom class requirements. The system operates at Class 1,000. Several attachments are available including analyzers, vacuum ovens, solvent removal, and datalogging.
The IsoGard minienvironment from The Baker Co. (Sanford, ME), features type 304 stainless steel construction. The pharmacy isolator uses a full gel seal supply HEPA filter with an integral diffuser system that covers the ceiling of the work surface. The filtered air provides better than Class 10 conditions. A plug-in exhaust filter below the work surface traps particulates. The minienvironment also houses a digital photohelic pressure sensor to monitor cabinet safety. n
The PRD-1000 minienvironment from General Air Corp. is specifically designed for photoresist applications using a chamber desiccant dehumidification method to provide Class 10 or better cleanliness.
Simplex Strip Doors Inc. manufactures modular rigid, framed panels that latch together to create laminar flow micro isolation chambers for protecting critical processes from personnel and equipment.
iE Air`s Total Control CoatGuard 2000 Mini-environment is a fully isolated, ultra clean, recirculatory enclosure system, designed for protecting Spin-Coat processes in the compact disc, microelectronics and semiconductor industries.
Channel Systems Inc.`s design allows unlimited configurations with no drilling or screwing of trim to framing, and no inserts.
Minienvironments from Enviroflex Inc. can be designed for use as a complete enclosure or localized for critical areas only in stainless steel, glass, plastics or the company`s own modular wall system.
Intelligent Enclosures` Ergo-Guard Manual I/O is used for enclosing product load/unload stations for semiconductor and CD manufacturing equipment.