Photoresist Thickness Verification and Automatic Correction
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
With this method, photoresist (PR) thickness applied to semiconductor wafers is measured and the information is used to modify application parameters for wafers being coated subsequently. Thickness data is converted into parallel binary-coded decimal (BCD) data and transmitted to a microprocessor to produce and drive optimum spin speeds. The wafer-to-wafer thickness variation is generally a drift in the average thickness of the coating due to gradual changes in parameters, as follows: (1) the temperature of the PR; (2) ambient temperatures; (3) viscosity of the fluid being evaporated; and (4) variations in the spin motor speed as its temperature increases upon running.