Selective isotropic etch for titanium-based materials

A process for selectively etching a sacrificial layer formed in a structure comprising a microelectromechanical device and one or more semiconductor devices, the process comprising;

• forming a plasma etchant from a fluorine-containing gas;
• maintaining the structure temperature at greater than about 100° C.;
• forming an opening extending from a surface of the structure to the sacrificial layer, wherein the sacrificial layer is exposed on a sidewall of the opening;
• and
• exposing the sacrificial layer to the plasma etchant through the opening for removing regions of the sacrificial layer without compromising the integrity of the semiconductor devices, wherein at least a portion of the sacrificial layer material that is exposed on the sidewall of the opening is removed and any remaining sacrificial layer material is laterally disposed relative to the opening, wherein the sacrificial layer is selected from among titanium, titanium-nitride, a titanium compound and a titanium alloy.

A process for selectively etching a sacrificial layer formed in a structure comprising a microelectromechanical device and one or more semiconductor devices, the process comprising:

• forming a plasma etchant from a fluorine-containing gas;
• maintaining the structure temperature at greater than about 100° C.;
• forming an opening extending from a surface of the structure to the sacrificial layer;
• exposing the sacrificial layer to the plasma etchant to remove regions of the sacrificial layer without compromising the integrity of the semiconductor devices, wherein at least a portion of removed regions of the sacrificial layer are laterally disposed relative to the opening and
• wherein an etch ratio of the etchant is at least 10:1 wherein the sacrificial layer is selected from among titanium, titanium-nitride, a titanium compound and a titanium alloy.

A process for forming a contact between a conductive via and a doped region formed in a semiconductor substrate, comprising:

• forming a sacrificial layer overlying the doped region;
• forming a material layer overlying the sacrificial layer;
• forming an opening in the material layer, wherein the opening exposes a region of the sacrificial layer;
• etching at least a portion of the sacrificial layer disposed laterally with respect to the opening;
• forming a conductive material in the etched portion of the sacrificial layer;
• and
• forming conductive material in the opening.

A process for forming a reentrant feature in a substrate, comprising:

• forming the substrate comprising in stacked relation, a first material layer, a first sacrificial layer, a second material layer, a second sacrificial layer, and a third material layer;
• forming a substantially vertical region of sacrificial material in the second material layer bridging the first and the second sacrificial layers;
• forming an opening through the third material layer, the second sacrificial layer and the second material layer, wherein the opening is bounded by the bridging sacrificial material and exposes the first sacrificial layer;
• laterally etching by plasma containing fluorine-containing gas a portion of the first and the second sacrificial layers proximate the opening and vertically etching the bridging sacrificial material.