Effect of time-dependent development process on the limit of proximity exposure compensation in electron beam lithography

Abstract

In our earlier papers, it was pointed out that the limit of proximity exposure compensation (PEC) in electron beam lithography using the dose correction technique is achieved if the dose correction factors are derived from the electron energy dissipation distribution (EED) at a depth in the resist where it has maximum lateral spread. The energy threshold criterion for the development process was used (this implicitly assumes a time-independent development process), to show that under such limiting PEC the resist edge slope of isolated and closely spaced line patterns becomes nearly equal to the edge slope of a single beam line. In this paper we show the effect of a time-dependent development process on the resist edge slope and pattern dimensional accuracy, when PEC is at its limits. The two developers 1:3 MIBK:IPA and MIBK are considered. A two-step development process which combines the advantages of the two developers is shown to provide much better control over the resist edge slope, pattern dimensional accuracy and process flexibility. Finally, the results of different time-dependent development processes are compared with the results when the energy threshold criterion is used for the development process.