# US 10,766,768 B2 · Encapsulated microelectromechanical structure

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- Number: US 10,766,768 B2
- Document ID: US10766768B2
- Status: Granted
- Kind: B2
- Application number: 16/565,876
- Filed: 2019-09-10
- Published: 2020-03-12
- Granted: 2020-09-08
- Earliest claimed: 2006-01-20
- Assignees: SiTime Corporation
- Applicants: SiTime Corporation
- Inventors: Aaron Partridge; Markus Lutz; Pavan Gupta
- Web page: https://patentgrep.com/patent/US10766768B2

## CPC

- B81C 1/00277: {for maintaining a controlled atmosphere inside of the cavity containing the MEMS}
- B81B 7/0035: {for maintaining a controlled atmosphere inside of the chamber containing the MEMS}
- B81B 7/0058: {for protecting against damages due to external chemical or mechanical influences, e.g. shocks or vibrations}
- B81B 7/007: {Interconnections between the MEMS and external electrical signals}
- B81C 1/00269: {Bonding of solid lids or wafers to the substrate}
- B81C 1/00301: {Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias}
- H10N 30/306: {Cantilevers}
- H10W 76/138: having another interconnection being formed by a cover plate parallel to the conductive base, e.g. sandwich type
- B81B 2201/0271: Resonators; ultrasonic resonators
- B81B 2203/0315: Cavities
- B81B 2203/04: Electrodes
- B81B 2207/07: Interconnects
- B81C 2201/0171: Doping materials
- B81C 2203/031: Anodic bondings
- B81C 2203/036: Fusion bonding
- B81C 2203/037: Thermal bonding techniques not provided for in B81C2203/035 - B81C2203/036
- B81C 2203/038: Bonding techniques not provided for in B81C2203/031 - B81C2203/037
- B81C: PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS (making microcapsules or microballoons B01J13/02; processes or apparatus specially adapted for the manufacture or treatment of piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/01)
- B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00)
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

A semiconductor layer having an opening and a MEMS resonator formed in the opening is disposed between first and second substrates to encapsulate the MEMS resonator. An electrical contact that extends from the opening to an exterior of the MEMS device is formed at least in part within the semiconductor layer and at least in part within the first substrate.

## Claims

### Claim 1

An integrated circuit device comprising:
a resonant microelectromechanical system (MEMS) structure supported by a first substrate, wherein the resonant MEMS structure comprises a silicon material doped with phosphorus;
a second substrate mounted to the first substrate so as to enclose the resonant MEMS structure within a chamber defined between interior surfaces respective to the first substrate and the second substrate;
an electrical contact formed in an exterior surface of one of the first substrate or the second substrate, the electrical contact to provide an output signal representing a resonance frequency of the resonant MEMS structure; and
oscillator circuitry to generate a clock signal from the output signal.

### Claim 2 (depends on 1)

The integrated circuit device of claim 1 wherein the oscillator circuitry comprises compensation circuitry to compensate a frequency represented by the output signal and a fractional locked-loop circuit to generate the clock signal as a frequency-multiple of a compensated frequency produced by the compensation circuitry.

### Claim 3 (depends on 1)

The integrated circuit device of claim 1 wherein the silicon material comprises single crystal silicon.

### Claim 4 (depends on 1)

The integrated circuit device of claim 1 wherein the resonant MEMS structure is formed from the first substrate by an etch-release process, the chamber being at least partially formed by the etch-release process.

### Claim 5 (depends on 4)

The integrated circuit device of claim 4 wherein the second substrate is bonded in fixed relation to the first substrate.

### Claim 6 (depends on 5)

The integrated circuit device of claim 5 wherein the etch-release process is characterized by the presence of trenches in at least one of the first substrate or the second substrate, and wherein further, openings of the trenches are filled so as to encapsulate the resonant MEMS structure within the chamber.

### Claim 7 (depends on 6)

The integrated circuit device of claim 6 wherein the openings of the trenches are filled with a material comprising at least one of silicon dioxide and silicon nitride, and wherein the resonant MEMS structure is hermitically sealed within the chamber.

### Claim 8 (depends on 1)

The integrated circuit device of claim 1 wherein the oscillator circuitry is mounted by the exterior surface and wherein the integrated circuit device is formed by a process which bonds the second substrate in fixed relation to the first substrate after the electrical contact has been formed in exterior surface and after the oscillator circuitry has been mounted to the exterior surface.

### Claim 9 (depends on 1)

The integrated circuit device of claim 1 wherein the oscillator circuitry is mounted by the exterior surface.

### Claim 10 (depends on 1)

The integrated circuit device of claim 1 wherein the electrical contact comprises heavily-doped silicon.

### Claim 11

A method of fabricating an integrated circuit device, the method comprising:
forming a resonant microelectromechanical system (MEMS) structure from a silicon material, in a manner such that the resonant MEMS structure is doped with phosphorus, and in a manner such that the resonant MEMS structure is supported by a first substrate;
mounting a second substrate to the first substrate so as to enclose the resonant MEMS structure within a chamber defined between interior surfaces respective to the first substrate and the second substrate;
forming an electrical contact formed in an exterior surface of one of the first substrate or the second substrate, the electrical contact to provide an output signal representing a resonance frequency of the resonant MEMS structure; and
providing oscillator circuitry, the oscillator circuitry to generate a clock signal from the output signal during operation of said integrated circuit device.

### Claim 12 (depends on 11)

The method of claim 11 wherein providing the oscillator circuitry comprises providing compensation circuitry and a fractional locked-loop circuit, the compensation circuitry to compensate a frequency represented by the output signal and the fractional locked-loop circuit to generate the clock signal as a frequency-multiple of a compensated frequency produced by the compensation circuitry.

### Claim 13 (depends on 11)

The method of claim 11 wherein the silicon material comprises single crystal silicon.

### Claim 14 (depends on 11)

The method of claim 11 wherein forming the resonant MEMS structure comprises using an etch-release process to form the resonant MEMS structure from the first substrate, the chamber being at least partially formed by the etch-release process.

### Claim 15 (depends on 14)

The method of claim 14 further comprising bonding the second substrate in fixed relation to the first substrate.

### Claim 16 (depends on 15)

The method of claim 15 wherein the etch-release process is characterized by the presence of trenches in at least one of the first substrate or the second substrate, and wherein further, the method comprises filling openings of the trenches so as to encapsulate the resonant MEMS structure within the chamber.

### Claim 17 (depends on 16)

The method of claim 16 wherein filling the openings of the trenches comprises filling the openings with a material comprising at least one of silicon dioxide and silicon nitride, and hermetically sealing the resonant MEMS structure within the chamber.

### Claim 18 (depends on 11)

The method of claim 11 wherein providing the oscillator circuitry comprises mounting the oscillator circuitry on the exterior surface and wherein the method further comprises forming the integrated circuit device using a process which bonds the second substrate in fixed relation to the first substrate after the electrical contact has been formed in exterior surface and after the oscillator circuitry has been mounted on the exterior surface.

### Claim 19 (depends on 11)

The method of claim 11 wherein providing comprises mounting the oscillator circuitry on the exterior surface.

### Claim 20 (depends on 11)

The method of claim 11 wherein forming the electrical contact comprises heavily-doping silicon to form the electrical contact.