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Photoresist Thickness Verification and Automatic Correction

IP.com Disclosure Number: IPCOM000039796D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Balder, WB: AUTHOR [+2]

Abstract

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.

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Photoresist Thickness Verification and Automatic Correction

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. A conventional method for establishing the desired thickness is to set the appropriate spin parameters for the type of PR being applied and then to process a test wafer to the desired thickness. The PR coating on the test wafer is measured and, if required, the rpm of the spin motor is adjusted, to bring the thickness into line. Usually this is the only adjustment made during a run. A commercial film thickness measurement tool measures the PR thickness on the apply/bake tool non-destructively. The measurement data is fed to a microprocessor which determines the optimum spin speed to produce the desired thickness. The new spin speed is set automatically on the apply/bake tool. The process continues for each wafer. If the film thickness shou...