Method of masking semiconductor wafers using a self-aligning mask

Claim 1

A process for applying a wax maskant to selected portions of a semiconductor wafer face prior to chemical etching of said wafer face, said process comprising: forming a pattern of ridges on a face of a wafer of semiconductive material having a plurality of regions containing active semiconductor devices; affixing an opposite face of said wafer to a support; placing a face of a spray mask on said wafer, said spray mask being a grid of a magnetic metal, said grid having a plurality of intersecting portions surrounding apertures corresponding to said regions in said wafer, and having a pattern of grooves on said face corresponding to said pattern of ridges on said wafer face; nesting said ridges in said grooves and abutting said spray mask face with said wafer face to interlock said mask with said wafer and align said grid apertures with said wafer regions; magnetically holding said mask against said wafer face; spraying wax onto said wafer regions through said apertures in said mask; and removing said mask from said wafer face.