Method for etched cavity devices

A method for etching a cavity in a substrate including a pressure sensor diaphragm and a body of semiconductor material, the body of semiconductor material having a first principal surface over which the pressure sensor diaphragm is formed and having a second principal surface opposite the first principal surface, the method comprising:

• anisotropically locally etching a preliminary cavity in the body of semiconductor material extending from the second principal surface toward the first principal surface and underlying the pressure sensor diaphragm;
• and
• exposing the preliminary cavity to a tetra-methyl-ammonium hydroxide (TMAH) etchant thereby forming a final cavity having a smoother final sidewall, the final cavity extending from the first principal surface to the second principal surface to expose at least a portion of the pressure sensor diaphragm through the body of semiconductor material.

A method for producing a pressure sensor device comprising:

• for a substrate having a substantially silicon body, a first principal surface, a second principal surface spaced from the first principal surface, and a pressure sensor element location proximate the first principal surface, locally anisotropically etching a preliminary cavity extending at least partly through the silicon body extending from the second principal surface toward the first principal surface, wherein the preliminary cavity underlies the pressure sensor element location and has a preliminary sidewall;
• and
• exposing the preliminary sidewall of the preliminary cavity to tetra-methyl-ammonium hydroxide (TMAH) etchant to provide a final cavity extending through the substantially silicon body to expose a portion of the substrate underlying the pressure sensor element location and acting as a pressure sensor diaphragm of the pressure sensor device.