METAL GATE DEVICE WITH REDUCED OXIDATION OF A HIGH-K GATE DIELECTRIC
Embodiments of the invention provide a device with a metal gate, a high-k gate dielectric layer and reduced oxidation of a substrate beneath the high-k gate dielectric layer. An oxygen barrier, or capping, layer on the high-k gate dielectric layer and metal gate may prevent such oxidation during processes such as spacer formation and annealing of ion implanted regions.
1 . A semiconductor device, comprising:
a substrate;
a high-k gate dielectric layer on the substrate;
a metal gate electrode on the high-k gate dielectric layer; and
a capping layer that is substantially free of oxygen and substantially seals a region between the high-k gate dielectric layer and the substrate from structures that comprise oxygen.
2 . The device of claim 1 , further comprising:
a first set of spacers on either side of the metal gate electrode;
a second set of spacers on either side of the first set of spacers; and
wherein the capping layer is between the first set of spacers and the second set of spacers.
3 . The device of claim 2 , wherein the second set of spacers have a bottom surface and the capping layer extends beneath the bottom surface of the second set of spacers.
4 . The device of claim 1 , further comprising a thin oxide layer between the high-k gate dielectric layer and the substrate and a first set of spacers on either side of the metal gate electrode, wherein the first set of spacers have a bottom surface and the thin oxide layer extends beneath the bottom surface of the first set of spacers.
5 . The device of claim 1 , wherein the capping layer comprises a nitride material.
6 . The device of claim 5 , wherein the capping layer has a thickness below about 75 angstroms.
7 . The device of claim 5 , wherein the capping layer comprises a material selected from the group consisting of 8-12% carbon-doped silicon nitride, stoichiometric silicon nitride and silicon carbide.
8 . The device of claim 2 , wherein the second set of spacers have a bottom surface and the capping layer extends beneath the bottom surface of the second set of spacers.