Method and apparatus for run-time correction of proximity effects in pattern generation

A method of forming a pattern using a beam corrected for proximity effects comprising the steps of:

• converting a vectorized data base of a pattern to a rasterized data base of said pattern comprising a plurality of pixels, wherein each pixel is represented as a specified exposure dose of said beam;
• defining a plurality of cells from said rasterized data base wherein each cell has a dimension larger than one pixel and smaller than a predetermined scattering range of said beam;
• creating a coarse coverage map wherein said coarse coverage map comprises a convolution value for each cell of said plurality of cells;
• creating a global thermal expansion map for said pattern wherein said global thermal expansion map is calculated using said convolution values;
• creating first dose correction multipliers for each cell by convolving values from said coarse coverage map with pre-calculated convolution kernels;
• identifying a pattern context for each pixel of said rasterized data base using said specified exposure dose of each near neighbor pixel;
• creating second dose correction multipliers for each pixel by applying pre-calculated edge correction factors in accordance with said pattern context;
• calculating dose modulations by combining said first and second dose correction multipliers using a lookup table;
• calculating a corrected exposure dose for each pixel using said dose modulation;
• calculating a feature origin shift for each pixel using said global thermal expansion map;
• and
• exposing said pattern on a resist coated substrate using said beam, wherein each pixel of said pattern is exposed using said corrected exposure dose and said feature origin shift.

A pattern generating system comprising:

• a source of a charged particle beam;
• an apparatus for periodically scanning said charged particle beam over a surface;
• a pattern conversion apparatus for converting a pattern data base from a vectorized representation to a rasterized representation;
• a first data storage apparatus coupled to said pattern conversion apparatus, wherein a portion of said rasterized representation of said pattern data base is stored as a first plurality of pixel data, each pixel having an exposure dose, for said beam, at a first exposure level;
• a proximity effect correction apparatus coupled to said first data storage apparatus, wherein said first exposure level of each pixel stored in said first data storage apparatus is retrieved and modified to correct for proximity effects to form a second plurality of pixel data corresponding to said first plurality of data, each pixel having an exposure dose, for said beam, at a second exposure level;
• a second data storage apparatus coupled to said proximity effect correction apparatus, for storing said second plurality of pixel data;
• and
• an exposure dose modulator and beam position apparatus coupled to said second data storage apparatus, wherein said second plurality of pixel data is retrieved from said second data storage apparatus and used to control said source of said charged particle beam to expose each pixel on said substrate;
• wherein said proximity effect correction apparatus causes pixel data to be input to said first storage apparatus and said second storage apparatus as said exposure dose modulator and beam position apparatus retrieves pixel data from said second storage apparatus, such that pixel data for a portion of said pattern is stored within said first storage apparatus and second storage apparatus until retrieved for exposure of said pattern by said charged particle beam is completed.