PBS-An historical perspective

Poly(butene-1-sulfone) (PBS) is a highly sensitive positive electron beam resist widely used today in the electron-beam fabrication of chromium masks for photolithography. Its sensitivity derives from the weak carbon-sulfur bond in the main chain which renders the bond very susceptible to scission. Although this propensity for main chain cleavage under high energy irradiation had been known since the late 1960`s, there were a number of complex, processing issues that needed to be resolved before commercial exploitation as an electron resist could be considered. Many of the problems encountered derive from the unique chemistry of polysulfones. This paper discusses these processing problems, the underlying chemistry, and the solutions adopted which led to successful commercial introduction of PBS in 1976.