Abstract: Magnesium oxide is deposited on a substrate as a mask with a pattern of openings which exposes a corresponding pattern of a surface of a substrate which is to be subjected to dry etching.In a specific application, the magnesium oxide mask is employed to delineate a conductor pattern on semiconductor substrates by dry etching.

Abstract: A process for forming an embedded interconnection metallurgy system on a substrate by (1) forming a first layer of an organic thermosetting polymerized resin material on the substrate, (2) forming a second overlying layer of a material that is soluble in a solvent that does not appreciably affect the material of the first layer, (3) forming a third layer resistant to reactive ion etching in O.sub.2 on the second layer, (4) masking the third layer to define the pattern of the desired metallurgy, (5) removing the exposed areas of the third layer, (6) reactive ion etching the resultant exposed areas of the first and second layers, (7) depositing a conductive metal with a thickness approximately matching the thickness of the first layer, and (8) exposing the substrate to a solvent selective to the material of the second layer thereby removing it and the overlying portions of the conductive metal layer.