mask

A patterned screen of any of several materials and types used in shielding selected areas of a semiconductor, photosensitive layer, or substrate from radiation during processing, so that the unshielded areas can be further processed to reproduce the chosen pattern.

NOTE The type of mask can be designated either by type (e.g., oxide mask or metal mask) or by function (e.g., diffusion mask or vapor-deposition mask).

References: 

JESD99B, 5/07