MEMS with small-molecule barricade
A MEMS element within a semiconductor device is enclosed within a cavity bounded at least in part by hydrogen-permeable material. A hydrogen barrier is formed within the semiconductor device to block propagation of hydrogen into the cavity via the hydrogen-permeable material.
1. An integrated circuit comprising:
a silicon substrate;
a lid;
a microelectromechanical system (MEMS) structure having a movable body within a cavity, the cavity being defined at least in part by release of oxide from at least one oxide layer through at least one vent in the lid, and at least one electrode;
one or more electrical contacts on an exterior surface of the integrated circuit;
at least one conductive via that electrically couples the one or more electrical contacts with the at least one electrode;
one or more barrier layers to inhibit diffusion of hydrogen and helium through an oxide present in the lid;
one or more barrier materials encircling the at least one oxide layer;
wherein the one or more barrier layers, the one or more barrier materials, the at least one via, the lid and the silicon substrate encapsulate the cavity relative to an atmosphere outside said integrated circuit, so as to inhibit the passage of hydrogen from the atmosphere into said cavity.
2. The integrated circuit of claim 1 wherein the one or more barrier layers comprise at least one of silicon nitride, aluminum nitride, aluminum oxide and silicon carbide.
3. The integrated circuit of claim 1 wherein the lid comprises one of monocrystalline silicon and polycrystalline silicon.
4. The integrated circuit of claim 1 wherein the one or more barrier materials comprises at least one metal.
5. The integrated circuit of claim 1 wherein the one or more barrier materials comprises a chip-surround barrier.
6. The integrated circuit of claim 1 wherein the one or more barrier materials comprises a trench filled with at least one of monocrystalline silicon and polycrystalline silicon.
7. The integrated circuit of claim 1 wherein the lid comprises one or more apertures, the at least one vent defined by the one or more apertures, wherein the at least one via passes through the lid via the one or more apertures, and wherein the one or more barrier layers seal the at least one vent following the oxide release.
8. The integrated circuit of claim 1 further comprising a gettering layer to chemically react with residual hydrogen within said integrated circuit.
9. The integrated circuit of claim 1 wherein the at least one oxide layer comprises a first oxide layer and a second oxide layer, with a crystal silicon layer therebetween, the movable body formed from the crystal silicon layer.
10. The integrated circuit of claim 9 wherein the crystal silicon layer is doped so as to have an n-type dopant concentration of at least 1E19/CM 3 .
11. The integrated circuit of claim 1 wherein the MEMS structure comprises a resonator and wherein the movable body is to resonate at a resonance frequency.
12. The method of claim 1 wherein forming the M EMS structure comprises forming a resonator and wherein the movable body is to resonate at a resonance frequency.
13. A method of fabricating an integrated circuit, the method comprising:
providing a substrate, a lid and at least one oxide layer;
forming a microelectromechanical system (MEMS) structure so as to have at least one electrode and a movable body within a cavity, wherein forming comprises releasing oxide through at least one vent in the lid so as to free the movable body to move and to at least partially define the cavity;
forming one or more electrical contacts on an exterior surface of the integrated circuit, and forming at least one conductive via to provide electrical communication between the one or more electrical contacts and the at least one electrode;
forming one or more barrier layers to inhibit diffusion of hydrogen through the lid;
forming one or more barrier materials so as to encircle the at least one oxide layer;
wherein the one or more barrier layers, the one or more barrier materials, the at least one via, the lid and the silicon substrate encapsulate the cavity so as to inhibit passage of hydrogen from an atmosphere outside said integrated circuit into said cavity.
14. The method of claim 13 wherein forming the one or more barrier layers comprises depositing at least one of silicon nitride, aluminum nitride, aluminum oxide and silicon carbide.
15. The method of claim 13 wherein providing the lid comprises depositing one of monocrystalline silicon and polycrystalline silicon.
16. The method of claim 13 wherein forming the one or more barrier materials comprises depositing at least one metal.
17. The method of claim 13 wherein forming the one or more barrier materials comprises forming a chip-surround barrier.
18. The method of claim 13 wherein forming the one or more barrier materials comprises etching a trench and filling the trench with at least one of monocrystalline silicon and polycrystalline silicon.
19. The method of claim 13 wherein forming the lid comprises forming one or more apertures in the lid, the at least one vent being defined by the one or more apertures, and wherein forming the at least one via comprises forming the at least one via so as to pass through the lid via the one or more apertures, and wherein forming the one or more barrier layers comprises sealing the one or more vents following the oxide release.
20. The method of claim 13 further comprising depositing a gettering layer so as to chemically react with residual hydrogen in said integrated circuit following encapsulation of the at least one oxide layer.
21. The method of claim 13 wherein the at least one oxide layer comprises a first oxide layer and a second oxide layer, with a crystal silicon layer therebetween, and wherein forming the MEMS structure comprises forming the movable body from the crystal silicon layer.
22. The method circuit of claim 21 wherein forming the MEMS structure comprises doping the crystal silicon layer so as to have an n-type dopant concentration of at least 1E19/CM 3 .