Air Film System for Handling Semiconductor Wafers

In an automated fabrication facility, the thin, fragile silicon wafers in which semiconductor circuits are formed must be transported to and from processing stations with a minimum of contact with other solid objects so as to minimize damage, contamination, and consequent lowering of product yield. This task has been undertaken for some time now, in IBM and elsewhere, by systems based on a lubricating film of air as a means for levitating and moving wafers. However, due to inherent motion instabilities and specific control needs, some solid contact is typically involved in effecting prescribed wafer motion. The need for solid contact control is greatly reduced by the air film system described in this paper. It is based on a surface configuration that combines two fluid mechanics phenomena to generate a supporting air film that provides and guides wafer motion. Wafer transportation and positioning are achieved with the air film operating in conjunction with special control device techniques.