SAN FRANCISCO — Makers of semiconductor fabrication clean rooms, or fabs, are getting more choices in less-combustible plastics for tools, wet benches, ducts and wall and floor coverings.
``No one has the complete problem description or the complete answer'' to combustibility risks faced by fab clean rooms, moderator Mike Sherman told the 120 plastics, semiconductor and insurance representatives attending a July 14 session on the topic at Semicon West '98 in San Francisco. Sherman is corporate product safety engineer for equipment supplier FSI International Inc. of Chaska, Minn.
Most semiconductor device makers take a wait-and-see attitude on materials used in fabs until their insurers give a definitive nod. And those approvals are surfacing.
Extensive tests already have quantified characteristics for a number of materials, said Roger Benson, a loss-prevention specialist in Rohnert Park, Calif., with Factory Mutual Engineering Association. Three insurers direct Norwood, Mass.-based Factory Mutual and cover many fabs.
``[Polyetheretherketones, polyvinylidene fluorides], Teflons, Halars, those kinds of materials, generically speaking, tested out pretty well,'' Benson said. ``Polypropylene, plasticized PVCs and even fire-retardant polypropylenes in early formulations did not do so well,'' he said. Fire-retardant PP ``either propagated like PP or gave off horrible smoke like PVCs,'' he said.
Benson said Factory Mutual's research arm has listed six polymers under its flammability test protocol, FM4910, since last year and is working on adding more.
``Within two to three months, we will have [a total of] 11 materials,'' he said. ``All have various characteristics that make them good or better or best for different kinds of chemical exposures.''
Among those listed are a PVDF and a fire-retardant PP from Compression Polymers Group of Moosic, Pa.; a fire-retardant PP and PVC from Takiron Co. Ltd. of Osaka, Japan; and two PVDFs from Westlake Plastics Co. of Lenni, Pa.
Still undergoing tests is a PVDF from Westlake made with Kynar 2850-02 that the firm says is so resistant to combustion that Factory Mutual's equipment could not measure its thermal response parameter accurately, according to Domenic Sciamanna, Westlake business manager for corrosion-resistant products. The material will undergo another test using a higher heat flux, Sciamanna said.
Others being reviewed for FM4910 are a post-chlorinated PVC sheet material from BFGoodrich Co. and opaque, clear and laminated varieties of Halar sheet from Compression.
Insurers abhor combustible materials.
``We don't have the normal polypropylenes in the fabs anymore,'' said Gregory Hazlett, a vice president and semiconductor and clean room specialist with Allendale Mutual Insurance Co. in Seven Hills, Ohio. ``There is the exponential to have big fires.''
To illustrate just how extensive fire damage can be, Robert Randall, assistant vice president in risk services for insurance broker Aon Corp. in San Francisco, reported loss estimates on three fab fires, all in Hsinchu, Taiwan. A fire at Advanced Microelectronic Products Inc. in November incurred damages of $66 million; United Integrated Circuits Corp., in October, $470 million; and Winbond Electronics Corp., in October 1996, $430 million.
The Winbond ``fire in Taiwan has been the single-biggest thing in my career in dealing with fire protection, as far as getting the attention of process people and managers in the industry,'' said David Quadrini, fire marshal with Texas Instruments Inc. in Dallas.
He noted that one safety measure U.S. fabs take that Taiwanese firms do not take is installing a sprinkling system.
As for existing equipment, insurers and device makers can differ on how to deal with it.
``Insurers are demanding a retrofit of old sinks,'' with detection systems, suppression systems or both, said Terry Maloney, manager of health, safety and industrial hygiene with Advanced Micro Devices Inc. in Sunnyvale, Calif. ``Owners feel most [or] all [are] fire-safe without retrofit,'' he said.
The Semiconductor Industry Association plans to develop a ``relative risk index'' for wet sinks, but the industry's economic downturn has stalled funding of the proposed $25,000-$35,000 study, Maloney said.
During 1997, IBM evaluated ways to retrofit existing semiconductor facilities with fire suppression systems.
``We've looked at three fabs so far,'' said IBM engineer Frederick Kern, referring to microelectronics unit sites in Burlington, Vt.; East Fishkill, N.Y.; and Essonnes, France.
Kern estimates a retrofit may cost $1.5 million to $2 million per fab. In February, IBM issued a specification for the work. ``One fire suppression company has provided a response'' to date. ``It is hard to estimate,'' Kern said.
The ongoing dialogue among device makers, insurers and equipment makers shows ``just how far we have come,'' said Rick Koski, director of environmental safety and health, wafer surface preparation and facilities for Semi/ Sematech, a nonprofit consortium in Austin, Texas. He recalled a 1995 meeting with ``insurance suppliers on one side of room, device manufacturers on other and [equipment] suppliers ducking.''
Now, people can sit at the same table.
``I said many times, `there is no way we, as an industry, can support 4910,''' said Koski, who recognizes each side has accommodated the others on concerns. ``FM really stepped up to the plate, but so did leading device manufacturers, the Intels and AMDs and TIs.''
Vinnie DeGiorgio, a principal with risk management consultant TRC Services in Mansfield, Mass., agreed: ``Most people now are embracing 4910.''