PYRAMID-a hierarchical, rule-based approach toward proximity effectcorrection. I. Exposure estimation

摘要

One of the major limiting factors in electron beam (e-beam)nlithography is the undesired development of circuit area caused bynelectron scattering (the proximity effect). Since the proximity effectnimposes a severe limitation on the ultimate resolution attainable withnelectron beam lithography, it is important to examine ways in which thenproximity effect can be reduced. In order to develop a fast andnefficient proximity effect correction scheme it is necessary to have anfast and accurate technique for finding the exposure (energy) depositednat any given point in the circuit pattern. In this paper we present thenhierarchical digital signal processing (DSP) model utilized by PYRAMIDn(our proximity effect correction scheme) to estimate these exposures.nOur approach employs a two part hierarchical estimation technique whichnis several orders of magnitude faster than a direct (spatial domain ornFFT-based) convolution yet is able to predict the result of an exposurenwith a high degree of accuracy. A detailed description of our method ofnexposure estimation is followed by a thorough analysts of itsnperformance through simulation and experimental results