Out with the old, in with the new
08/01/2002
by Mike Fitzpatrick
Industry professionals who spent the first half of their careers designing and building "state-of-the-art" semiconductor fabs will now spend their autumn years trying to figure out how to tear the darn things down.
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The transition to the highly-productive 300 mm fab, coupled with the growing age of our existing facilities, will bring us to a point in the next few years where we may see more facilities decommissioned than constructed.
Business conditions will lead manufacturers to shut down process lines, either abandoning certain products altogether, or relocating them overseas. Some facilities may be so outdated that they will be abandoned, sold to another manufacturer or converted for a different use. Unlike facility construction, a discipline in which we've had three decades to hone our skills, decommissioning a facility is a whole new ballgame.
Decommissioning guidelines
While the goal in building a new facility is to construct "contamination-free" systems to protect the process and the product, our goal in decommissioning is to remove those same systems in a "contamination-free" man ner, protecting both personnel and the environment. While the driving factors in constructing a new facility might be safety, quality and meeting deadlines, the driving factors in decommissioning a facility are safety, safety and safety.
Decommissioning requires the development of a project-specific closure plan that includes a review of the regulatory requirements applicable and an understanding of the chemical history of the plant. Existing building permits are studied for any specified closure requirements and environmental permit requirements are examined.
Suspected hazards are identified and an environmental health and safety (EHS) analysis is prepared before starting any work. Only when these tasks are complete are we able to develop the specific procedures required to remove and dispose of the production equipment and the facility systems.
Because the closing of any plant entails the transfer or disposal of considerable assets, owners frequently employ the services of professional asset management firms to identify assets and to evaluate optional strategies for their disposition. An appraisal of major equipment will determine both the "as is" and reconditioned value of each component. The assets can then be categorized for re-use, sale or disposal.
When process tools and facility equipment are offered for resale, it's necessary to compile a record of equipment histories, operation and service manuals, maintenance records and available spare parts. Asset management firms may also serve as the owner's agent in the sale of equipment, identifying potential buyers and negotiating financial terms. Owners may also ask these firms to determine the most beneficial disposition of the real property involved, assessing the options of selling or leasing all or part of the plant site.
The Environmental Protection Agency (EPA) has adopted a "cradle-to-grave" accountability to track hazardous waste from its production through eventual disposal. The process of disposing of this material is both time-consuming and expensive, and it's often preferable to decontaminate this waste prior to disposal. Hazardous waste treatment can minimize expensive waste disposal and maximize cost-effective, non-hazardous waste disposal.
You can relocate or sell manufacturing production equipment after decontamination. Chemicals and gasses used in the manufacturing process will either be present or have left residues in this equipment. Any hazardous material needs to be identified and removed or neutralized before the system components can be disposed of. This is accomplished onsite by pumping down and cycle purging the equipment and/or by shipping the equipment offsite for chemical neutralization. During this portion of the work, an EHS signoff procedure is used, similar to the procedure used when first installing the production equipment.
SEMI's stance
Semiconductor Equipment and Materials International (SEMI) S-12-0298 Guidelines for Equipment Decontamination specifies the "minimum requirements for the transfer or relocation of equipment which has been exposed to hazardous or toxic materials."
The standard provides an equipment assessment methodology, decontamination guide lines and documentation requirements. Procedures for wipe sampling suspected material and establishing "non-hazardous" levels are addressed. Decontamination is usually performed by a specialty contractor that has knowledge of the semiconductor manufacturing process, is familiar with process equipment and has experience in cleaning and decontaminating semiconductor equipment.
Process utility systems are evaluated and decontaminated using methods similar to those used for process tools. Bulk gas systems (upon testing) may be found to be suitable for non-regulated disposal, while many of the specialty gas systems will require testing and decontamination. Exhaust ducts and waste lines will almost always be contaminated and require decontamination. Separate procedures may be required for abandoned de-ionized water systems and waste collection/neutralization facilities.
All process system components should be tested and decontaminated if necessary, labeled and then inventoried for disposal or resale. The plant closure plan will specify not only the schedule for the removal of equipment but also the sequence for removal. It may be necessary to leave systems such as life safety and acid neutralization operating so that they may be used in the decontamination process.
Facility distribution systems, such as plant-chilled water, are rarely contaminated and usually suitable for non-regulated disposal or recycling. All systems should be tested prior to removal. Major plant equipment such as chillers, boilers and electrical switchgear may be scrapped, re-used or sold.
Demolition
If any part of the structure is to be demolished, testing and abatement of lead paint and asbestos materials may be required.
Demolition of grade-level slabs, sumps and trenches may uncover areas of contaminated soil that require re-mediation by a specialty firm. Although cleanroom finishes such as floors, ceilings and walls should be free from hazardous material, their possible exposure to chemical spills over the decades may require them to be cleaned or decontaminated. HEPA filters, as a rule, should be tested and scheduled for disposal.
Michael A. Fitzpatrick is program director of microelectronics for Lockwood Greene Engineers. A senior member of the Institute of Environmental Sciences and Technology (IEST), he is chairman for WG012 (Considerations in Cleanroom Design) and WG028 (Minienvironments).