VLSI Production with a multi-layer photolithography process

Multi-layer resist processes have been reported by researchers with varying success as applied to a manufacturable photolithography process. Since 1980, Hewlett Packard has used a version of the portable conformal mask (PCM) process (1) to increase production margins on the 1.0 um geometries used in the manufacture of its NMOS III circuits (2) . This process with the introduction of a bleachable dye (3) in the bottom photoresist layer drastically increases GCA wafer stepper performance by reducing substrate effects (4).