Method and arrangement for aligning a mask pattern relative to a semiconductor substrate
AssigneeU.S. Philips Corporation
InventorsGijsbertus Bouwhuis, Theodorus F. Lamboo
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Abstract
A method and arrangement for aligning a mask comprising a mask-pattern relative to a substrate when the mask-pattern is repeatedly and directly imaged on the substrate, gratings in the mask and gratings on the substrate (phase gratings) being employed as alignment references. The gratings in the mask are located outside the mask pattern and the phase gratings are located on the substrate outside the area where the mask-pattern is imaged. The substrate (phase) gratings are imaged on one of the mask gratings with a projection system which is also used for projecting the mask-pattern on the substrate. The image of the gratings on the grating in the mask is adjusted. Thus, a very accurate alignment can be achieved.
Claims10
A method of aligning with a substrate a mask pattern formed in a mask, wherein the mask pattern is repeatedly imaged directly on said substrate, comprising the steps of:
- (a) providing said mask comprising plural gratings which are located in said mask outside the area of said mask pattern, (b) providing said substrate comprising two phase gratings which are located outside the area on said substrate where a plurality of images of said mask pattern are to be formed, (c) using a first of said mask gratings as a reference with which other gratings are aligned, (d) imaging a said phase grating on said reference grating with a projection system which is used for imaging said mask pattern on said substrate, (e) modulating the position of an observed image of a certain said grating which is momentarily aligned relative to said reference grating, and (f) adjusting the position of said certain grating so that, averaged in time, the observed image of said certain grating is aligned relative to the reference grating.
Dependencies are inferred from the claim text.