Integrated getter area for wafer level encapsulated microelectromechanical systems

• US 8,980,668 B2
• Filed: 02/08/2013
• Issued: 03/17/2015
• Est. Priority Date: 02/12/2004
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Lutz, Markus, Partridge, Aaron
• Primary Examiner(s): Toledo, Fernando L
• Assistant Examiner(s): Newton, Valerie N
• Application Number:
  US13/762,584
• Publication Number:
  US 20130285162A1
• Time in Patent Office: 767 Days
• Field of Search: None
• US Class Current: 438/50
• CPC Class Codes: B81B 7/0038 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• CPC Class Codes: B81C 1/00269 Bonding of solid lids or wafers to the substrate
• CPC Class Codes: B81C 1/00285 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• CPC Class Codes: B81C 2203/0136 Growing or depositing of a covering layer
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

There are many inventions described and illustrated herein. In one aspect, present invention is directed to a thin film encapsulated MEMS, and technique of fabricating or manufacturing a thin film encapsulated MEMS including an integrated getter area and/or an increased chamber volume, which causes little to no increase in overall dimension(s) from the perspective of the mechanical structure and chamber. The integrated getter area is disposed within the chamber and is capable of (i) “capturing” impurities, atoms and/or molecules that are out-gassed from surrounding materials and/or (ii) reducing and/or minimizing the adverse impact of such impurities, atoms and/or molecules (for example, reducing the probability of adding mass to a resonator which would thereby change the resonator'"'"'s frequency). In this way, the thin film wafer level packaged MEMS of the present invention includes a relatively stable, controlled pressure environment within the chamber to provide, for example, a more stable predetermined, desired and/or selected mechanical damping of the mechanical structure.

Claims

1. A method of manufacturing a microelectromechanical device including a mechanical structure and a periphery area which are disposed over a substrate and in a chamber which is formed, at least in part, by a thin film encapsulation structure, the method comprising:

forming the mechanical structure;

depositing a fluid in the chamber;

forming a getter area in the periphery area by forming a plurality of gaps in the periphery area, wherein the plurality of gaps are disposed in the chamber; and

sealing the chamber by depositing the thin film encapsulation structure;

wherein;

at least a portion of the respective mechanical structure, periphery area and getter area are disposed in a same cavity of the chamber; and

the getter area captures impurities, atoms, or molecules that are out-gassed from materials contained within the chamber.

2. The method of claim 1, wherein the mechanical structure and the periphery area are formed within a single layer that extends over the substrate.

3. The method of claim 1, wherein:

the mechanical structure includes at least one fixed electrode and at least one anchor region which are disposed over the substrate and in the chamber; and

at least one of;

the at least one fixed electrode includes a plurality of gaps therein, and the at least one anchor region includes a plurality of gaps therein.

4. The method of claim 1, wherein sealing the chamber by depositing the thin film encapsulation structure includes:

depositing a sacrificial layer on or around at least a portion of the mechanical structure and the periphery area;

depositing a first encapsulation layer over the sacrificial layer;

forming at least one vent through the first encapsulation layer to allow removal of at least a portion of the sacrificial layer;

removing at least a portion of the sacrificial layer juxtaposed the mechanical structure and the periphery area; and

depositing a second encapsulation layer over or in the vent to seal the chamber.

5. The method of claim 4, wherein the substrate includes a sacrificial layer, and wherein removing at least a portion of the deposited sacrificial layer juxtaposed the mechanical structure and the periphery area further includes removing at least a portion of the sacrificial layer of the substrate that is disposed beneath the mechanical structure and the gaps of the periphery area.

6. The method of claim 4, wherein the first encapsulation layer comprises a polycrystalline silicon, amorphous silicon, germanium, silicon/germanium and/or gallium arsenide.

7. The method of claim 4, wherein the second encapsulation layer is a semiconductor material which comprises of polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium and/or gallium arsenide.

17. The method of claim 1, wherein the getter area at least one of:

(a) purifies contents of the chamber by facilitating diffusion of volatile species in surrounding solids during high temperature process steps, and (b) reduces the probability of mass loading on the mechanical structure.

8. A microelectromechanical device comprising:

a substrate;

a mechanical structure disposed over the substrate;

a periphery area disposed over the substrate;

a getter area including a plurality of gaps disposed in a portion of the periphery area; and

a chamber formed, at least in part, by depositing a thin film encapsulation structure over the mechanical structure, the periphery area, and the getter area;

wherein;

at least a portion of the respective mechanical structure, periphery area and getter area are disposed in a same cavity of the chamber; and

the getter area captures impurities, atoms, or molecules that are out-gassed from materials contained within the chamber.

9. The device of claim 8, wherein the thin film encapsulation structure includes first and second encapsulation layers.

10. The device of claim 9, wherein the first encapsulation layer includes monocrystalline silicon, polycrystalline silicon, porous polycrystalline silicon, amorphous silicon, silicon carbide, silicon nitride, silicon/germanium, germanium, or gallium arsenide.

11. The device of claim 10, wherein the second encapsulation layer includes monocrystalline silicon, polycrystalline silicon, porous polycrystalline silicon, silicon nitride, silicon oxide, porous silicon, amorphous silicon, germanium, silicon/germanium, gallium arsenide, or silicon carbide.

12. The device of claim 8, wherein a fluid is disposed in the chamber.

13. The device of claim 8, wherein the mechanical structure includes at least one fixed electrode and at least one anchor region which are disposed over the substrate and in the chamber.

14. The device of claim 8, wherein the at least one fixed electrode is formed to include a plurality of gaps therein, and the at least one anchor region is formed to include a plurality of gaps therein.

15. The device of claim 8, wherein the mechanical structure is a resonator.

16. The device of claim 8, wherein the mechanical structure and the periphery area are formed within a single layer that extends over the substrate.