Method and apparatus for improving the uniformness of patterns generated by electron beam lithography.

摘要

To improve the uniformness of patterns for LSI circuits or masks generated in an electron beam lithographic system, a backscatter indicator signal (BS indicator) is obtained and used to vary a control signal (SRF) for the beam stepping rate proportional to the variations in the amount of backscattered electrons. This avoids non-uniformity such as line width variations which otherwise occur when the pattern to be generated covers border lines between two different substrate or base layer materials. Special range setting circuitry (47) is provided for adjusting, during an initial prescan of a sample of two materials having an extreme difference in their backscatter characteristic, the offset and the gain for the backscatter detector (41). During subsequent exposure of a wafer, the backscatter indicator signal and thus the stepping rate control signal variations remain within preselected limits.