In-house reclaim of test wafers

Semiconductor pilot wafer reclaim done in-house can represent a huge potential savings for any manufacturer. Historically, however, it is outsourced at 200 mm, either due to costs or fab floor space limitations that can otherwise be used for production increases. Now that 300 mm wafer processing is no longer in it´s infancy, the issue of in-house pilot wafer reclaim must be revisited. Criteria for success of this operation are two-fold: pilot wafers re-used in the fab must be free of film and have few particles, and there must be a significant cost savings to the fab by doing so. Outsourcing this task is not only expensive, but the large amount of silicon removed in the process gives these test wafers a short lifetime and raises the cost. Texas Instruments and Applied Materials have developed a polish process for Pilot Wafer Reclaim. This polishing process removes less than 3% of the silicon removed by third party vendors, dramatically extending pilot wafer lifetime, shortens the inventory turn-around time and significantly reducing the fab´s silicon costs, which are still several times that of 200 mm. This paper will present a methodology to effectively recycle blanket pilot wafers using a two-fold approach: film strip followed by polish.