Comparison of liquid- and vapor-phase silylation processes for 193-nm positive-tone lithography

Liquid- and vapor-phase silylation processes are compared for a 193 nm positive-tone lithographic process using polyvinylphenol as a resist. The liquid-phase process, using a mixture of xylene, hexamethylcyclotrisilazane, and propylene glycol methyl ether acetate, was found to have higher silylation contrast, better sensitivity, and a smaller proximity effect (a decrease in silylation depth for smaller feature sizes). These factors result in a larger exposure latitude, particularly at feature sizes below 0.5 micrometers . These advantages are greatly offset, however, by the increased chemical costs, which are estimated to be more than 100 times greater than for the vapor-phase process.