CHARACTERIZATION ENHANCEMENTS IN RESIST PHOTOSPEED

Current photospeed testing methods are based on dose to clear (E0) or resist contrast (gamma10). Either method is inadequate for controlling sensitivity to within +/- 1.5%. We investigated various methods for i mproving these photospeed tests. Ranked in order of decreasing importa nce are: (i) controlling standing waves (reflectivity); (ii) choice of developer; (iii) develop time; and (iv) exposure pattern. Reflectivit y can be controlled by careful attention to resist thickness, addition of a bottom antireflective layer, addition of a low refractive index layer (AquaTar), or by using a thick photoresist. Moreover, we can uti lize the whole dissolution curve rather than the one-point determinati on of the E0 test. We have identified regions in the dissolution curve that are highly sensitive measures of change in development rate per change in dose. This test dubbed PS-50 measures the dose required to a chieve 50% film retention of the exposed and developed film. This test with the addition of a bottom antireflective layer has improved test precision.