Surface-imaged silicon polymers for 193-nm excimer laser lithography

A negative-tone surface-imaged resist process based upon the area-selective oxidation of silicon-backbone polymers, is described. A bromine-based plasma is the resist developer, where the oxidized polymer inhibits the bromine-initiated etching to yield a negative-tone image. Using either polysilanes or polysilynes, resist sensitivities in the range of 50 mJ/cm² have been obtained and resolutions to 0.2 μm achieved. Photosensitizers can be added to further accelerate the photoxidation, resulting in sensitivities less than 20 mJ/cm². The latent image formation is reciprocal with respect to fluence in the range 0.05 to 1.5 mJ/cm² per pulse and with respect to repetition rate. The photooxidation contrast is one, whereas the bromine-based etch step can have a contrast as high as 5. In addition, the exposure, focus, and development latitudes have all been characterized and compared to other surface-imaged 193-nm resist systems. When high-ion-density plasma sources are used, throughput levels appropriate for single-wafer processing can be achieved.