Spinners systems are used to apply photoresist to the wafers as one of the first steps in a photo lithography process. I design a custom spinner chuck to allow Non-vacuum, Non central bottom contact of silicon wafers. Researches at NIST were having problems with the standard spinner chucks in the CNST NanoFab. They had problems getting a good vacuum seal and they had contamination from the chuck surface onto the bottom of the wafer. Some researchers had thin delicate membranes and a vacuum chuck would have destroyed their wafer. I solve all these problems with a custom spinner chuck design that only supported the wafer at the outer edge “~1mm lip” and holds the wafer via three fins positioned 120 degrees apart. The important feature here is the that one fin is placed closer to the center then the other two. This closer fin is used to lock the wafer via interface with flat on wafer edge. This closer fin “Cams” the wafer into the center of the spinner chuck and allows perfect spins with minimal edge defects and no contamination or scratches to the lower side of the wafer. We have made about ten of these chucks, most are for 100mm and a few were for 150mm diameter wafers. It is important to have a wafer that has a flat on the edge, most wafers that are 25.4mm to 150mm in diameter have this standard.
The Nonvacuum, Non-contact spinner chuck design solves the problem of how to work with fragile membranes on silicon wafers. Since this chuck does not require a vacuum to hold the wafer in place many process are possible that could not be done before.
This design allows a standard spinner unit to be used to now provide self -alignment, non-vacuum interface to wafer and Non-contact to center region of wafer.