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Exposure characteristics of character projection-type low-energy electron-beam direct writing system

We have developed a character projection (CP)-type low-energy electron beam (EB) direct writing (EBDW) system called EBIS (Electron Beam Integrated System). A low-energy EB of less than 5 keV has the potential to expose by the CP-method without intra- and inter-layer proximity effect corrections. In this paper, the advantages of the proximity effect of the low-energy EBDW system of 5 keV with the CP exposure are discussed. The experimental results to compare the intra-layer proximity effect between 5 keV and 50 keV showed that the low-energy EB has an advantage over high-energy EB in terms of small shot size deviation at the pattern edge. The experimental results of inter-layer proximity effect of 5 keV indicate that no proximity effect corrections for structures in underlying layers are necessary in the case of the combination of low-energy EB and multi-layer resist. On the other hand, in response to concern about the Coulomb interaction effect, which is a critical problem of low-energy EB, a dose correction function of each shot was proposed for the EBIS system. We are convinced that the low-energy EBDW is useful for exposure of practical patterns of logic devices by the CP exposure with higher throughput, because the proximity effect is so small that complicated corrections due to the adjacent pattern and structures of substrate under exposure layer are unnecessary.