One-dimensional calculation method for proximity effect correction in cell projection electron-beam direct writing

Electron beam (EB) direct writing has often been used for advanced device development because the dimensions of the pattern required for advanced device fabrication are below the maximum resolution of applicable optical lithography. Recently, EB direct writing has been put to practical use in advanced device production using the cell projection (CP) method, which drastically increases the writing throughput of an EB direct writing system. When CP EB direct writing is used to produce advanced DRAM, however the handling of a large volume of data becomes an important issue. A data preparation system with simple proximity effect correction, which is suitable for the CP method, is therefore required for the reduction of the data preparation time (conversion time). We therefore propose the improved proximity effect correction, which is based on the self-consistent method, using a one dimensional calculation method for CP direct writing. This method can drastically reduce the exposure intensity calculation time because the calculation of a linear integral can be substituted for that of a surface integral. The conversion time to fabricate a 0.15 micrometer Gbit DRAM (10.3 multiplied by 109 rectangle patterns) with a CD accuracy within plus or minus 5%, was reduced to be only 10% of original elapsed time (in conventional 2-D correction method).