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High Contrast Photoresist For Use With Wafer Steppers

The paper discusses the functional performance of the ULTRAMAC PR914 positive photoresist system on a 10:1 wafer stepper, using monochromatic light at 436 nanometers. Submicron resolution capabilities in the order of 0.625 micron are illustrated with resist thicknesses up to 1.6 microns using both metal-ion-free and metal-based developer systems. Submicron resolutions were achieved at exposure energies of 70 mJ/cm4 to 270 mJ/cm2, with film thickness losses of less than 4%. Edge wall profiles of greater than 85° are shown when ULTRAMAC MF62 metal-ion-free developer is used in an immersion development mode. The effect of various developers with respect to percent film thickness loss, resolution, contrast, edge wall profiles and photospeed are discussed and illustrated by SEM photographs. A comparison of the MTF values (modulation transfer function) of the lens system itself, as compared to the resolution capabilities of the resist system, is discussed for submicron geometries. The PR914 resist also has excellent step coverage capability and this is illustrated by SEM photographs. The anisotropic plasma etching characteristics are also shown.