| 摘要 |
A photolithographic mask is made by a computer generated two-dimensional array of light and dark pixels being photoreduced to provide the mask in which the pixels remain resolved. In use the mask is imaged on to a workpiece such that individual pixels are not resolved, thus providing a varying grey scale which closely approximates to a true grey scale. Problems with non-linear response of photographic materials to illumination intensity are avoided. The pixel array is divided up into resolution cells or pixel sub-arrays each providing a respective optical transmission coefficient. The computer assigns each cell a respective pixel pattern appropriate to the respective transmission coefficient. Pixel patterns may be prearranged and stored or computed using a random number generator. Transmission coefficients may be input to the computer as data, or alternatively computed from a mathematical function where the required mask transmission profile corresponds to such a function. |
