Metal mask etching of silicon

Abstract

The present disclosure provides a method for etching trenches, contact vias, or similar features to a depth of 100 &mgr;m and greater while permitting control of the etch profile (the shape of the sidewalls surrounding the etched opening). The method requires the use of a metal-comprising masking material in combination with a fluorine-comprising plasma etchant. The byproduct produced by a combination of the metal with reactive fluorine species must be essentially non-volatile under etch process conditions, and sufficiently non-corrosive to features on the substrate being etched, that the substrate remains unharmed by the etch process. Although aluminum is a preferred metal for the metal-comprising mask, other metals can be used for the masking material, so long as they produce an essentially non-volatile, non-corrosive etch byproduct under etch process conditions. By way of example, and not by way of limitation, metallic materials recommended for the mask include aluminum, cadmium, copper, chromium, gallium, indium, iron, magnesium, manganese, nickel, and combinations thereof. In particular, aluminum in combination with copper or magnesium is particularly useful, where the copper or magnesium content is less than about 8% by weight, and other constituents total less than about 2% by weight. The plasma feed gas includes at least one fluorine-containing compound such as nitrogen trifluoride (NF ), carbon tetrafluoride (CF ), and sulfur hexafluoride (SF ), by way of example and not by way of limitation. Oxygen (O ), or an oxygen-comprising compound, or hydrogen bromide (HBr), or a combination thereof may be added to the plasma feed gases to help provide a protective layer over etched sidewalls, assisting in profile control of the etched feature.