1. Field of the Invention
The present invention relates to a method for generating a pattern, a storage medium, and an information processing apparatus.
2. Description of the Related Art
In a lithography technique, an exposure apparatus including an illumination optical system for illuminating a mask with light from a light source and a projection optical system for projecting an image of a pattern of a mask on a substrate (e.g., a wafer) is used.
As a minimum size of a target pattern to be formed on a substrate becomes a size lower than the wavelength of the light from a light source to be used for exposure, when the mask pattern image is projected onto the substrate, unintended interactions occur between adjacent patterns. The interactions of the light from respective patterns in the mask generate interference fringes, and this causes formation of an unintended image of a shape different from the target pattern on the substrate. With the increase in the difference between the minimum size of the target pattern and the wavelength of the light source, the occurrence of the resolution failure of the pattern increases.
As a method for generating a mask pattern using a computer, there has been known a method for selecting and placing a plurality of cells from a cell library including many standard cells, and performing an optical proximity correction (OPC) on the pattern of the placed cells. In the OPC, in consideration of the effects on the image of the pattern due to the interactions of the light from adjacent patterns, a correction for changing the shape of each pattern element constituting the pattern is performed so that the image of the pattern is formed within a target range. The cell library includes a plurality of cells constituting basic patterns to be used as patterns of masks, and the respective cells have patterns different from each other.
Unfortunately, if the OPC is performed onto the entire mask pattern (full chip) after the generation of the pattern of the mask by placing all of the cells to be used, the calculations for changing the shape of the pattern elements increases as the number of the pattern elements increases. This largely increases the amount of calculation in the OPC. To solve the problem, United States Patent Application Publication No. 2009/0100396 discusses a method for correcting shapes of patterns by separately performing an OPC onto the pattern of each cell in advance, generating a mask pattern by placing the OPC-processed cells, and performing a finishing OPC onto the entire mask pattern. Through the processing, in the OPC processing to be performed onto the entire mask pattern, with respect to a part of the pattern elements, if the images of the pattern elements have already been within the target range as a result of the OPC processing performed onto the pattern of each cell, the OPC processing thereon can be eliminated. This can reduce the number of the pattern elements to be corrected, and as a result, the amount of calculation can be reduced.
Unfortunately, still the calculation amount in the OPC processing to be performed onto the entire pattern of the mask is large even if the method discussed in United States Patent Application Publication Application No. 2009/0100396 is used, and there is a need for further reduction in the calculation amount.