Patent ID: 6686214
Filing Date: 2004-02-03
Classification: G03F,H01L

Abstract:
A method of aligning a mask to a specific crystal plane in a wafer, comprising the steps of:forming a first mask having at least one alignment structure on a wafer surface, said alignment structure being coarsely aligned with said specific crystal plane and having an array of components that are offset relative to each other by known angles defining the degree of precision with which said mask can be finely aligned with said crystal plane; performing an orientation-selective anisotropic etch through said first mask to etch said alignment structure into said wafer surface, said components of said alignment structure producing different etch patterns in said wafer surface according to their relative orientation to said specific crystal plane, said etch patterns being aligned with said crystal plane having a symmetrical shape; stripping said first mask from said wafer; providing a second mask, different from said first mask, bearing alignment patterns and an index structure, said index structure being distinct from said alignment patterns; orienting said second mask so that said alignment patterns are aligned with said etch patterns having a symmetrical shape; applying said second mask to said wafer surface; and performing a second etch through said second mask to etch said index structure into said wafer for use in crystal plane alignment during subsequent wafer processing, said index structure being aligned with said specific crystal plane to a precision greater than Â±1Â°.