Sematech effort to simplify comparisons of consumables
Hank Hogan
AUSTIN, TX — Consider the possibility of categorizing consumables into different grades, thereby transforming things like gloves and wipers from the high tech black magic they appear as to some people into commodities, easily understood and specified by all users.
In fact, there`s a group effort underway to develop, as a first step, methods to characterize gloves and wipers for semiconductor users. The first goal, according to Sematech (Austin, TX) spokesman Jess Blackburn, is expansion of an Institute of Environmental Sciences and Technology (IEST) wiper document that now covers testing to also include characterization.
An IEST group is currently updating Recommended Practice CC004.2, published in 1987, on cleanroom wipers.
Beyond this initial target lies the aforementioned possibility of categorizing consumables into different grades. Such a grading system would simplify purchasing. That could have implications about the price and performance of consumables far beyond the semiconductor industry. However, the consensus is that such a development is a year or more off. But even accomplishing the initial goal would yield contamination control benefits.
“Everyone would be using the same test methods, and hopefully then wiper comparison would be just a matter of comparing test data rather than how it currently stands, which is there are no standardized test methods that everyone follows,” explains David P. Nobile, product development manager for wiper manufacturer Contec Inc. (Spartanburg, SC).
Sematech, the semiconductor manufacturing consortium, is spearheading the effort to bring some order to the consumables jungle. Also involved is the IEST as well as the consortium`s member companies, such as Advanced Micro Devices Inc. (Sunnyvale, CA), Lucent Technologies Inc. (Murray Hill, NJ), Motorola Inc. (Schaumburg, IL), and Texas Instruments Inc. (Dallas). On the vendor side, participants include glove manufacturers, such as Safeskin Corp. (San Diego) and Oak Technical Inc. (Stow, OH). Besides Contec, other wiper manufacturers involved include Lym-Tech Scientific (Chicopee, MA), the Texwipe Company LLC (Upper Saddle River, NJ), Berkshire Holding Corp. (Great Barrington, MA), and Milliken and Co. (Spartanburg, SC).
Although there have been several meetings of the participants, no documents have yet been produced. What has emerged is a tentative work flow, with a four-step process. Crucial in this is the evaluation of the proposed test methods by the semiconductor manufacturers. Because the semiconductor companies are the end-customers, any characterization methods have to meet their approval. The glove effort seems to be further along, according to assessments from various participants.
“They`ve actually developed a set of standards that the semiconductor manufacturers are evaluating,” says Blackburn of Sematech.
Donna Di Gangi, quality manager for the scientific group at Safeskin, says that some of the parameters being tested include particulates; extractables such as anions and cations; pinholes; strength of the glove, including tensile and elongation; electrostatic discharge properties and organic matter. Di Gangi worked on the extractable and particulate measurement methods, trying to make them as sound as possible. However, the tests are destructive, and that adds a bit of uncertainty to the process.
“You`re going to get varying results because each glove is going to be slightly different,” notes Di Gangi. “You can`t really retest to see how your methods worked.”
One side effect, says Di Gangi, is that manufacturing process control is highlighted. Or rather, the lack of control is highlighted. Without manufacturing consistency, any test result will be of little value, especially because the tests cannot be repeated.
As for wipers, the situation is not so clean.
According to participants, there are 13 or so parameters that have been under discussion. Of particular interest for cleanrooms are those involving particulates. Steven J. Paley, president and chief technical officer at Texwipe, points out that wiper particulate measurements have moved from a dry test, which consisted of shaking a wiper near a particle counter, to wet methods. These in turn have evolved from using water to using low tension cleaning solutions, such as water-isopropyl alcohol mixtures. At the same time, there`s been a move toward the use of scanning electron microscopes. All of these innovations have boosted the value of the particulate measurement techniques.
“The tests that we`ve developed are certainly repeatable and we have a tremendous amount of data to show and measure that repeatability,” says Paley.
However, these innovations are still on-going and subject to some debate. Indeed, the wiper group has been looking at all possibilities.
“One of the things that Sematech did ask was that each of the manufacturers go back and do some research to locate any and all third party methods that might pre-exist that could be adapted for use on cleanroom wipers. There has been a fair amount of activity in that regard that has taken place. And there have been some methods that have been proposed to the group as being potentially useful in this exercise,” says Berkshire president and CEO Rusty Bromley.
In light of this, there have reportedly been some lively discussions within the wiper group about how best to proceed. It`s a somewhat overwhelming process that`s been likened to eating an elephant. As a result, the participants have decided to start small. They`re tackling the less contentious topics first to establish a guideline, a procedure, for developing these methods.
For both gloves and wipers, it`s unknown how long the process will take. Because the glove side already has characterization methods under evaluation, it will likely be done first.
Blackburn of Sematech characterizes the effort as enjoying a good level of mutual collaboration from both suppliers and users. As for the wiper specifications, he acknowledges that the group hasn`t yet produced preliminary methods. However, he notes that the group is working on them.