October 29, 2007 9:00 PM PDT
IBM aims to salvage silicon for solar industry
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IBM has come up with a way to more efficiently recycle scrap silicon wafers owned by semiconductor manufacturers for the solar industry. The technique basically involves polishing a scrap wafer with water, an abrasive pad, and a piece of machinery ordinarily used to smooth out the pits and valleys in production chips. Rather than smooth out the surface of the wafer, the primary goal of the water polishing process is to erase any intellectual property or chip designs on the wafer.
"We use it literally to scrap off the integrated circuits," said Tom Jagielski, an engineering manager at IBM working on the project.
Water makes the process more eco-friendly--usually, wafers get dipped in abrasive chemicals or blasted with tiny glass beads to remove circuitry.
IBM estimates that around 3 million wafers get scrapped a year. If you could turn those all into solar panels, the panels would be capable of generating 13.5 megawatts of power.
That would represent a small percentage of the world's solar output. Sharp, the largest solar panel maker in the world, can manufacture more than 600 megawatts of solar cells a year. But a global silicon shortage--which started after large subsidies in Germany goosed solar demand in early 2004--makes any source of processed silicon welcome.
Texas Instruments, Intel, and other companies already sell their scrap wafers. TI used to unload them, garage-sale style, outside the factory. Starting in 2004, it began to sell them in a more uniform program. Now, TI sells about 1 million scrap wafers a year to solar manufacturers, which results in about $8 million in revenue.
Scrap wafers, more often than not, are blanks--for instance, wafers that were used to calibrate or test manufacture processes. The wafers get repolished after each test and, after a certain point, are too thin to use as test blanks anymore. Even though thin, the wafers remain thick enough for the solar industry.
Jagielski said that IBM plans to share the technique with other chipmakers, but how and when the process will be shared has yet to be determined. IBM currently recycles wafers this way in its Burlington, Va., facility and will bring it to its East Fishkill, N.Y., plant.
The solar shortage is expected to continue at least through next year. Although supply has increased, global demand for solar panels is expanding. Other solutions for ameliorating the problem lie in relying on dirty or less-pure silicon for solar panels. CaliSolar has come up with a way to isolate impurities in dirty silicon so that panels made from the material will still generate electricity. Ordinarily, impurities cause silicon panels to fail.