United States Patent Number: 6,177,133, January 23, 2001. 8 pages. Also available from the United States Patent and Trademark Office. Website: http://www.uspto.gov.
NOTE: At the time of publication, the author Richard Savage was not yet affiliated with Cal Poly.
A spin coating process for controlling the mean thickness of photoresist on the surface of a semiconductor wafer. The wafer surface has a central axis normal to the surface. The process comprises the steps of applying the solution to the wafer surface and spinning the wafer about the central axis at a spindle speed until the solution has dried. The spindle speed is a function of the desired mean thickness of the photoresist, the barometric pressure and the relative humidity. The spindle speed is determined from a statistical model described by the equation: MT=A+BxRH+CxBP+D/SS1/2 wherein: MT is mean thickness in Å; RH is relative humidity in percent; BP is barometric pressure in mm of Hg; SS is spindle speed in rpm; and A, B, C and D are constant coefficients.
Materials Science and Engineering