Wafer encapsulated microelectromechanical structure

• US 9,434,608 B2
• Filed: 10/27/2014
• Issued: 09/06/2016
• Est. Priority Date: 01/20/2006
• Status: Active Grant

• Current Assignee: SiTime Corporation (Megachips Corporation)
• Original Assignee: SiTime Corporation (Megachips Corporation)
• Inventors: Partridge, Aaron, Lutz, Markus, Gupta, Pavan
• Primary Examiner(s): FOURSON III, GEORGE R
• Application Number:
  US14/524,986
• Publication Number:
  US 20150041928A1
• Time in Patent Office: 680 Days
• Field of Search: 257/417, 257/684, 257/773, 438/52, 438/98
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/0271 Resonators; ultrasonic resonators
• CPC Class Codes: B81B 2203/0315 Cavities
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 2207/07 Interconnects
• CPC Class Codes: B81B 7/0035 for maintaining a controlled atmosphere inside of the chamber containing the MEMS
• CPC Class Codes: B81B 7/0058 for protecting against damages due to external chemical or mechanical influences, e.g. shocks or vibrations
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals
• CPC Class Codes: B81C 1/00269 Bonding of solid lids or wafers to the substrate
• CPC Class Codes: B81C 1/00277 for maintaining a controlled atmosphere inside of the cavity containing the MEMS
• CPC Class Codes: B81C 1/00301 Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
• CPC Class Codes: B81C 2201/0171 Doping materials
• CPC Class Codes: B81C 2203/031 Anodic bondings
• CPC Class Codes: B81C 2203/036 Fusion bonding
• CPC Class Codes: B81C 2203/037 Thermal bonding techniques not provided for in B81C2203/035 - B81C2203/036
• CPC Class Codes: B81C 2203/038 Bonding techniques not provided for in B81C2203/031 - B81C2203/037
• CPC Class Codes: H01L 23/051 another lead being formed by a cover plate parallel to the base plate, e.g. sandwich type
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

A cavity is formed within a first substrate together with trenches that separate first and second portions of the first substrate from each other and from the remainder of the first substrate. The first portion of the first substrate is disposed within the cavity and constitutes a microelectromechanical structure, while the second portion of the substrate is disposed at least partly within the cavity and constitutes a first portion of an electrical contact. A second substrate is secured to the first substrate over the cavity to define a chamber containing the microelectromechanical structure. The second substrate has a first portion that constitutes a second portion of the electrical contact and is disposed in electrical contact with the second portion of the first substrate such that the electrical contact extends from within the chamber to an exterior of the chamber.

Claims

1. A microelectromechanical device comprising:

a first substrate;

a chamber;

a microelectromechanical structure at least partially disposed within the chamber and formed, at least in part, from a first portion of the first substrate;

a second substrate, connected to the first substrate, and having a first surface that forms a wall of the chamber; and

a contact having first and second portions, the first portion of the contact being at least partially disposed outside the chamber and formed, at least in part from a second portion of the first substrate, and the second portion of the contact being formed, at least in part from a portion of the second substrate.

2. The microelectromechanical device of claim 1 wherein the first and second portions of the contact constitute a continuous conduction path extending from an interior of the chamber to an exterior of the chamber.

3. The microelectromechanical device of claim 2 wherein the second substrate comprises a second surface opposite the first surface, and wherein the continuous conduction path extends from the interior of the chamber to the second surface of the second substrate.

4. The microelectromechanical device of claim 1 wherein the second portion of the contact is doped to have a conductivity substantially higher than a conductivity of one or more other portions of the second substrate.

5. The microelectromechanical device of claim 1 wherein a trench is formed in the second substrate around at least a portion of the second portion of the contact.

6. The microelectromechanical device of claim 5 further comprising a first insulating material disposed within the trench to electrically isolate the second portion of the contact from one or more other portions of the second substrate.

7. The microelectromechanical device of claim 1 further comprising a third substrate, the third substrate being an insulator and the first substrate comprising a semiconductor substrate disposed on the insulator.

8. The microelectromechanical device of claim 1 wherein the second substrate is connected to the first substrate by a bond formed by at least one of fusion bonding, anodic-like bonding, silicon-direct bonding, soldered bonding, thermo-compression bonding, thermo-sonic bonding, laser bonding or glass-reflow bonding.

9. The microelectromechanical device of claim 1 wherein the second substrate comprises one or more of single-crystal silicon, polycrystalline silicon, porous polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium, or gallium arsenide.

10. The microelectromechanical device of claim 1 wherein the microelectromechanical structure comprises a moveable electrode and wherein the first portion of the contact extends into the chamber adjacent the moveable electrode.

11. A method of fabricating a microelectromechanical device, the method comprising:

forming a microelectromechanical structure within a first substrate, including forming a cavity within the first substrate, and forming trenches within the first substrate to separate first and second portions of the first substrate from each other and from one or more remaining portions of the first substrate, the first portion of the first substrate being disposed within the cavity and constituting the microelectromechanical structure, and the second portion of the substrate being disposed at least in part within the cavity and constituting a first portion of an electrical contact; and

securing a second substrate to the first substrate over the cavity to define a chamber containing the microelectromechanical structure, the second substrate having a first portion that constitutes a second portion of the electrical contact, the first portion of the second substrate being disposed in electrical contact with the second portion of the first substrate such that the electrical contact extends from within the chamber to an exterior of the chamber and is formed partly from each of the first and second substrates.

12. The method of claim 11 wherein the second substrate comprises a first surface that defines a wall of the chamber and a second surface opposite the first surface, the electrical contact forming continuous conduction path extending from the interior of the chamber to the second surface of the second substrate.

13. The method of claim 11 further comprising doping the first portion of the second substrate to establish a conductivity in the second portion of the contact substantially higher than a conductivity in one or more remaining portions of the second substrate.

14. The method of claim 11 further comprising forming a trench within the second substrate around the first portion of the second substrate to separate the first portion of the second substrate from one or more remaining portions of the second substrate.

15. The method of claim 14 further comprising disposing a first insulating material within the trench formed around the first portion of the second substrate to electrically isolate the second portion of the electrical contact from the one or more remaining portions of the second substrate.

16. The method of claim 11 wherein the first substrate comprises a semiconductor substrate, the method further comprising disposing the semiconductor substrate on an insulator substrate to form a semiconductor-on-insulator, and wherein securing the second substrate to the first substrate comprises securing the second substrate to a side of the first substrate opposite the insulator substrate.

17. The method of claim 11 wherein securing the second substrate to the first substrate over the cavity comprises bonding the second substrate to the first substrate by at least one of fusion bonding, anodic-like bonding, silicon-direct bonding, solder bonding, thermo-compression bonding, thermo-sonic bonding, laser bonding or glass-reflow bonding.

18. The method of claim 11 wherein forming the microelectromechanical structure within the first substrate comprises forming a moveable electrode within the first substrate, and wherein the first portion of the electrical contact extends into the chamber adjacent the moveable electrode.

19. The method of claim 11 wherein the second substrate comprises one or more of single-crystal silicon, polycrystalline silicon, porous polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium, or gallium arsenide.

20. A microelectromechanical device comprising:

a first substrate having a cavity formed therein and trenches to separate first and second portions of the first substrate from each other and from one or more remaining portions of the first substrate, the first portion of the first substrate being disposed within the cavity and constituting a microelectromechanical structure, and the second portion of the first substrate being disposed at least in part within the cavity and constituting a first portion of an electrical contact; and

a second substrate secured to the first substrate over the cavity to define a chamber containing the microelectromechanical structure, the second substrate having a first portion that constitutes a second portion of the electrical contact, the first portion of the second substrate being disposed in electrical contact with the second portion of the first substrate such that the electrical contact extends from within the chamber to an exterior of the chamber and is formed partly from each of the first and second substrates.