This invention relates to an improved method of electron beam exposure.
As a result of the microminiaturization and high packing density of semiconductor elements, a certain lithography technique using the electron beam exposure method has recently been highlighted as a submicron patterning technique. This electron beam exposure method exposes a positive type (or a negative type) resist film 2 on a mask or a semiconductor substrate 1 as shown in FIG. 1, while scanning it with an electron beam. In this method, however, a portion 5 of a marginal area 4 other than a desired exposure area 3 is exposed due to the forward-scattered beams in the resist film 2 and the backward-scattered beams from the substrate 1, causing a problem of what is called "proximity effects", that is, causing the deformation of a pattern configuration. "Proximity Corrections in a Raster Scan Electron Lithography Machine" (S. K. S. Ma, M. Parikh and W. Ward ), which appeared in J. Vac, Scl. Technol., 19(4), November/December 1981 describes a method for reducing the proximity effect caused by the electron beam exposure. According to this method, when a specific pattern and an adjacent narrow pattern are to be formed, the spacing, etc. of these patterns is initially calculated through simulation and an optimal dose of an electron beam corresponding to each pattern is selected based on the pattern data, thereby reducing the proximity effect. This method takes a relatively long time when the raster scan electron lithography machine is used. In order to identify pattern data involving the proximity data and process it, it is necessary to perform processing by both a main frame computer and minicomputers. In this case, a relatively long time is required even using the main frame computer. In the raster scan electron lithography machine, not only the whole surface of the exposure area, but also the whole surface of the data area must be scanned, also requiring a considerable length of time.