This paper examines the application of transform techniques to the problem of compensating for the proximity effect in electron-beam lithography. The patterns examined contain features as small as 0.20 μm. The transform methods employed here have been discussed in earlier papers. However, to date the amount of published experimental evidence documenting the degree of success of the method has been very limited. Therefore, one of the objectives of this paper is to examine thoroughly a set of four patterns containing a number of challenging features which will not develop correctly without some form of compensation. Since very little work on 0.20-μm proximity correction is currently available for comparison, we have attempted to simulate the GHOST method for these same four patterns. The GHOST method is a successful and widely accepted technique for computationless compensation of electron backscattering. It employs a defocused complementary pattern exposure to compensate for this electron backscatter. Thus we can anticipate that it will not adjust for the distortions due to forward scattering, for example, which can affect features in the 0.20-μm range. In addition to forward scattering, we observe that the transform method can compensate for asymmetric astigmatism. We have found asymmetric distortion to be a problem when attempting to write features in the range of 0.20 μm on some commercially available machines. Therefore, the method may have special significance for such machines.
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Haslam et al. (1988) studied this question.