IBM to Recycle Silicon Wafers for Solar Cells
November 5, 2007 Timothy Prickett Morgan
IBM is probably best known for its enterprise-class servers and related systems software, but the company is obviously a pretty big player in the chip industry with its various Power and PowerPC chips. IBM’s techies in Burlington, Vermont, where IBM still makes a lot of chips, have been scratching their heads about what to do with defective silicon wafers, which are the inevitable result of any chip-making process, and have come up with a novel idea: recycle them for use in solar cells.
An engineer named Eric White from the Burlington factory, which is located there because the Watson family that ran IBM for the better part of 60 years liked to ski, has created a means to polish all of the semiconductor etchings that turn a silicon wafer into a microprocessor (or any other kind of chip such as memory) off the wafer, thus turning it back into a raw piece of polysilicon material. Once the wafer is cleaned, IBM can use it to calibrate its machinery as it does its chip-making runs–this is called a monitor wafer–and after it gets a little worn out from use, then IBM can sell it to the burgeoning solar power industry, which is eagerly looking for raw silicon material from which it can make solar cells.
These wafers are usually cast off into landfills–which is something of a creepy thought, but this is the modern industrial economy’s way of handling waste. The IBM method means this silicon resource, which is very expensive to produce, can be recycled for other uses. IBM estimates that the global chip industry produces approximately 3 million scrap silicon wafers a year, which would be sufficient to create a solar farm that could generate 13.5 megawatts of electricity. That works out to 57 million kilowatt-hours of juice per year, which is enough to power 6,000 Western-style homes at 9,500 kilowatt-hours per home per year. The shocking thing, of course, is how few homes that amount of electricity powers. Why someone didn’t think to do this 30 years ago is also a bit of a shame, but progress is progress and IBM is to be commended for coming up with the scheme to recycle its silicon.
The Semiconductor Industry Association says that around 250,000 silicon wafers are started each day in the world, and IBM estimates that about 3.3 percent of the wafers are scrapped. By recycling those scrapped wafers at the Burlington facility as monitor wafers, IBM saved more than $500,000 in 2006 and is projected to save $1.5 million in 2007 and that much each year going forward. IBM did not say how much money it could make selling the second-hand wafers. And by using recycled silicon, solar cell manufacturers can save between 30 percent and 90 percent of the energy they normally expend creating solar cells, those lowering the carbon footprint of their products.
Because Big Blue now has now gone green, it plans to share the methodology behind the wafer scrubbing with the rest of the silicon industry.