Single and dual wavelength exposure of photoresist

The dependency of photoresist line width control on the photoresist thickness variations has been quantified for three different microelectronics wafer surfaces. The exposures were made with a step-and-repeat projection camera which is designed to image with both the Hg-g and Hg-h spectral lines to the wafer surface. A filter was placed in the light path so that resist exposures with only the Hg-g line could also be studied. The effect of camera defocus and nominal photoresist thicknesses of 800 and 1600 nm was included. The expected result of the line width variation periodicity being equal to 1/2 of the exposing wavelength was found. However, also found is an unexpected periodicity which could be described as λR6. © 1981 SPIE.