Manufacturing photomask for photolithography involves selecting transparency-adjusting pattern features during exposure process, and ascertaining densities of pattern features

摘要

Manufacturing photomask by comparing critical dimension values to reference critical dimension value, determining degrees of illumination intensity to be decreased, selecting transparency-adjusting pattern features provided in set at substrate of photomask during exposure process, obtaining correlation between densities of pattern features, ascertaining densities of pattern features corresponding to distribution of degree of illumination intensity to be decreased, and providing pattern features at substrate. Manufacturing photomask comprises providing photomask, transferring image of main pattern (150) to a wafer; quantifying the critical dimensions to obtain a distribution of values of the critical dimensions on the wafer; comparing the critical dimension values to reference critical dimension value to as certain differences between them; determining the degrees to which the intensity of the illumination used in the exposure process would need to be decreased in order to reduce the differences in relation to localities on the photomask between the critical dimension values and reference critical dimension value to obtain distribution of degrees in relation to the localities; selecting transparency-adjusting pattern features if provided in a set at a rear side of the substrate (100) of the photomask during the exposure process to change the intensity of the illumination passing through the photomask during the exposure process due to the density of the features (200) in terms of their size and spacing; obtaining correlation between the densities of the transparency-adjusting pattern features in terms of their size and spacing and the changes that the transparency-adjusting pattern features provided at those densities at the rear side of the substrate would make in the intensity of the illumination directed through it during the exposure process based on the correlation; ascertaining the densities of the transparency-adjusting pattern features that correspond to the distribution of the degree to which the intensity of the illumination needs to be decreased to obtain a distribution of the densities of the transparency adjusting pattern features in relation to the localities; and providing transparency-adjusting pattern features at the rear side of the substrate in an arrangement corresponding to the distribution of the densities of the transparency-adjusting pattern features. The image of main pattern is transferred to a wafer by directing illumination on the wafer through the photomask in an exposure process and using the image to produce a pattern on the wafer formed of critical dimensioned mechanisms.