| 摘要 |
A mask for use in photolithography and apparatus for using the mask, in which a pattern formed as opaque regions in a transparent mask or as transparent regions in an opaque mask are to be transferred to a photosensitive layer by exposing the photosensitive layer through the mask. Alternatively the photosensitive layer could be exposed to light reflected from the mask if the pattern were formed as variations in the reflectivity of the mask. In order that the mask can be accurately positioned with respect to the photosensitive layer they are both formed with fiducial marks and the fiducial mark on the mask is formed as a plurality of very small elements extending transverse the general line of the fiducial mark and so positioned that diffraction effects at the edges of the elements cooperate to provide a single dense image, that is a single bright image on a dark ground or a single dark image on a bright ground depending on whether the elements are opaque or transparent. |
