MEMS with small-molecule barricade

1. A semiconductor device comprising:

a cavity enclosed at least in part by hydrogen-permeable material;

a microelectromechanical system (MEMS) element disposed in the cavity; and

a hydrogen barrier that blocks propagation of hydrogen into the cavity via the hydrogen-permeable material;

wherein the cavity is formed in a first layer of silicon and enclosed, at least in part, by a hydrogen-permeable oxide, and wherein the hydrogen barrier blocks propagation of hydrogen into the cavity via the hydrogen-permeable oxide; and

wherein the first layer of silicon is disposed adjacent a silicon lid layer, the silicon lid layer having a first substantially planar surface that encloses a portion of the cavity and a second substantially planar surface having the hydrogen-permeable oxide disposed thereon in a first hydrogen-permeable oxide layer.

2. The semiconductor device of claim 1 wherein the hydrogen barrier comprises silicon nitride.

3. The semiconductor device of claim 1 wherein the hydrogen barrier comprises a hydrogen-impermeable material layer disposed over the first hydrogen-permeable oxide layer.

4. The semiconductor device of claim 1 wherein the hydrogen barrier comprises a hydrogen-impermeable material layer disposed between the hydrogen permeable oxide layer and the second substantially planar surface of the silicon lid layer.

5. The semiconductor device of claim 1 wherein a hydrogen-permeable trench extends from the first hydrogen-permeable oxide layer through the silicon lid layer to a second hydrogen-permeable layer interposed between the silicon lid layer and the first layer of silicon, and wherein the hydrogen barrier comprises one or more hydrogen-impermeable materials that prevent hydrogen outside the semiconductor device from propagating through the first hydrogen-permeable oxide layer to the hydrogen-permeable trench.

6. The semiconductor device of claim 5 wherein the one or more hydrogen-impermeable materials comprise a metal feature electrically coupled to a conductive region separated from the silicon lid layer by the hydrogen-permeable trench.

7. The semiconductor device of claim 6 wherein the one or more hydrogen-impermeable materials comprise a dielectric material disposed over the first hydrogen-permeable oxide layer.

8. A semiconductor device comprising:

a cavity enclosed at least in part by hydrogen-permeable material;

a microelectromechanical system (MEMS) element disposed in the cavity; and

a hydrogen barrier that blocks propagation of hydrogen into the cavity via the hydrogen-permeable material;

wherein the cavity is formed in a first silicon layer that is sandwiched between second and third silicon layers, the second and third silicon layers being separated from the first silicon layer by first and second hydrogen-permeable oxide layers and having respective substantially planar opposing surfaces that enclose the cavity, and wherein the hydrogen barrier forms a ring around the cavity within at least one of the first and second hydrogen-permeable oxide layers.

9. The semiconductor device of claim 8 wherein the hydrogen barrier comprises silicon nitride.

10. A semiconductor device comprising:

a first silicon layer disposed between second and third silicon layers and having a MEMS cavity bounded at least in part by respective surfaces of the second and third silicon layers;

a first hydrogen permeable channel disposed between the first and second silicon layers; and

a first hydrogen barrier structure disposed in the first hydrogen-permeable channel around the MEMS cavity to block propagation of hydrogen into the MEMS cavity via the first hydrogen-permeable channel;

a hydrogen-permeable dielectric layer disposed on a surface of the second silicon layer opposite the second-silicon-layer surface that bounds the MEMS cavity; and

an electrical contact disposed in an opening of the hydrogen-permeable dielectric layer and extending for at least five (5) microns over a surface of the hydrogen-permeable dielectric layer.

11. The semiconductor device of claim 10 wherein the first hydrogen barrier structure comprises at least one of single-crystal silicon, polysilicon or silicon nitride.

12. The semiconductor device of claim 10 wherein the first hydrogen-permeable channel comprises a hydrogen-permeable oxide layer disposed between the first and second silicon layers.

13. The semiconductor device of claim 10 further comprising a second hydrogen-permeable channel disposed between the first and third silicon layers and wherein the first hydrogen barrier structure extends through the first silicon layer and into the second hydrogen-permeable channel to block propagation of hydrogen into the MEMS cavity via the second hydrogen-permeable channel.

14. The semiconductor device of claim 10 further comprising a second hydrogen-permeable channel disposed between the first and third silicon layers and a second hydrogen barrier structure disposed in the second hydrogen-permeable channel around the MEMS cavity to block propagation of hydrogen into the MEMS cavity via the second hydrogen-permeable channel.