MEMS devices
A method of manufacturing a MEMS device comprises forming a MEMS device element ( 14 ). A sacrificial layer ( 20 ) is provided over the device element and a package cover layer ( 22 ) is provided over the sacrificial layer. The sacrificial layer is removed using at least one opening ( 22 ) in the cover layer and the at least one opening ( 24 ) is sealed by an anneal process.
1. A method of manufacturing a MEMS device, comprising:
forming a MEMS device element;
forming a sacrificial layer over the device element;
forming a package cover layer over the sacrificial layer;
defining at least one opening in the package cover layer;
removing the sacrificial layer through the at least one opening, thereby forming a package space over the device element; and
sealing the at least one opening by a hydrogen anneal process.
2. A method as claimed in claim 1 , wherein the sacrificial layer comprises an oxide layer.
3. A method as claimed in claim 2 , wherein the sacrificial layer comprises silicon oxide.
4. A method as claimed in claim 1 , wherein the package cover layer comprises silicon.
5. A method as claimed in claim 4 , wherein the package cover layer comprises polycrystalline silicon-germanium.
6. A method as claimed in claim 4 , wherein the package cover layer comprises polycrystalline silicon.
7. A method as claimed in claim 1 , wherein removing the sacrificial layer comprises at least one of a HF wet etch process and a HF-vapor process.
8. A method as claimed in claim 1 , further comprising providing a silicon nitride layer beneath the package cover layer, through which at least one opening is also formed.
9. A method as claimed in claim 1 , further comprising providing an anneal protection layer as part of the process of forming the MEMS device element.
10. A method as claimed in claim 9 , wherein the protection layer comprises silicon nitride.
11. A method as claimed in claim 1 , wherein the MEMS device element comprises at least one of a switch, a capacitor and a resonator.
12. A packaged MEMS device, comprising:
a MEMS device element;
a package cover layer, provided over a cavity above the MEMS device element;
a hydrogen annealed sealed sacrificial-etch opening in the package cover layer; and
a silicon nitride layer beneath the package cover layer, having at least one opening aligned with the sealed sacrificial-etch opening.
13. A device as claimed in claim 12 , wherein the package cover layer comprises at least one of polycrystalline silicon, polycrystalline silicon-germanium and germanium.
14. A device as claimed in claim 13 , wherein the hydrogen annealed sealed sacrificial-etch opening includes silicon atoms migrated due to an H 2 anneal.