Outgassing Issues in Acetal Resist Design

The outgassing issues that have long plagued conventional acetal resist designs are shown to be significantly mitigated depending on the structure of the acetal-blocked polymer. Resists formulated with acetal-blocked polymers based on low molecular weight vinyl ethers such as ethyl vinyl ether and t-butyl vinyl ether deblock during exposure resulting in considerable outgassing inside the stepper and attendant film shrinkage. By modifying the acetal structure, deblocking can be completely prevented during exposure, in which case the resist requires post-exposure baking to initiate the deblocking reaction as with conventional high activation energy systems. Such systems also show superior plasma etch resistance compared to conventional lower molecular weight acetals.