Temperature stable MEMS resonator

• US 9,148,073 B1
• Filed: 02/27/2014
• Issued: 09/29/2015
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: SiTime Corporation (Megachips Corporation)
• Original Assignee: SiTime Corporation (Megachips Corporation)
• Inventors: Hagelin, Paul M., Grosjean, Charles I.
• Primary Examiner(s): Gannon, Levi
• Application Number:
  US14/191,939
• Time in Patent Office: 579 Days
• Field of Search: 310/311, 310/315, 310/341, 310/346, 310/370, 331/66, 331/154, 331/156, 331/176, 333186-189, 333/197, 333/200, 333/219, 333/219.1, 333/234
• US Class Current: 1/1
• CPC Class Codes: H02N 1/00 Electrostatic generators or motors using a solid moving electrostatic charge carrier
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator
• CPC Class Codes: H03B 5/32 being a piezoelectric resonator selection of piezoelectric material H10N30/00
• CPC Class Codes: H03H 2009/02251 Design
• CPC Class Codes: H03H 2009/02283 Vibrating means
• CPC Class Codes: H03H 2009/02291 Beams
• CPC Class Codes: H03H 2009/02299 Comb-like, i.e. the beam comprising a plurality of fingers or protrusions along its length
• CPC Class Codes: H03H 2009/02322 Material
• CPC Class Codes: H03H 2009/0233 comprising perforations
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 2009/155 using MEMS techniques
• CPC Class Codes: H03H 3/0072 of microelectro-mechanical resonators or networks micromembranes or microbeams B81B2203/01; manufacture of microstructural devices in general B81C
• CPC Class Codes: H03H 3/0073 Integration with other electronic structures
• CPC Class Codes: H03H 3/0076 for obtaining desired frequency or temperature coefficients
• CPC Class Codes: H03H 9/02244 of microelectro-mechanical resonators
• CPC Class Codes: H03H 9/02433 Means for compensation or elimination of undesired effects
• CPC Class Codes: H03H 9/02448 of temperature influence
• CPC Class Codes: H03H 9/125 Driving means, e.g. electrodes, coils
• CPC Class Codes: H03H 9/21 Crystal tuning forks
• CPC Class Codes: H03H 9/2405 of microelectro-mechanical resonators
• CPC Class Codes: H03H 9/2468 : Tuning fork resonators
• CPC Class Codes: H03H 9/2484 : with two fork tines, e.g. Y-beam cantilever
• CPC Class Codes: H10N 30/01 : Manufacture or treatment
• CPC Class Codes: H10N 30/04 : Treatments to modify a piezoelectric or electrostrictive property, e.g. polarisation characteristics, vibration characteristics or mode tuning
• CPC Class Codes: Y10T 29/42 : Piezoelectric device making
• CPC Class Codes: Y10T 29/49002 : Electrical device making
• CPC Class Codes: Y10T 29/49005 : Acoustic transducer
• CPC Class Codes: Y10T 29/4902 : Electromagnet, transformer or inductor
• CPC Class Codes: Y10T 29/4908 : Acoustic transducer

Abstract

In a microelectromechanical system (MEMS) resonator having a reduced magnitude of thermal coefficient of frequency (TCF), a resonant member has first and second surfaces and an opening in the first surface that extends toward the second surface. A compensating material is disposed within the opening and characterized by a temperature coefficient of Young'"'"'s Modulus (TCE) having a sign opposite that of a TCE of the resonant member.

Claims

1. A microelectromechanical system (MEMS) resonator having a reduced magnitude of thermal coefficient of frequency (TCF), the MEMS resonator comprising:

a resonant member to generate an oscillatory output signal through oscillation in a mechanical resonance mode, the resonant member having first and second surfaces and an opening in the first surface that extends toward the second surface, wherein the opening in the first surface of the resonant member extends into the resonant member without reaching the second surface; and

a compensating material disposed within the opening in the first surface of the resonant member and characterized by a temperature coefficient of Young'"'"'s Modulus (TCE) having a sign opposite that of a TCE of the resonant member.

2. The MEMS resonator of claim 1 wherein the opening in the first surface of the resonant member extends to a depth less than a distance between the first and second surfaces along an axis normal to the first and second surfaces.

3. The MEMS resonator of claim 1 further comprising a liner material disposed in the opening.

4. The MEMS resonator of claim 1 wherein a cross section of the resonant member through the opening and the first and second surfaces is characterized by opposing sidewalls of the resonant member that constitute sides of the opening.

5. The MEMS resonator of claim 1 wherein the opening in the first surface of the resonant member is formed by removal of a constituent material of the resonant member.

6. The MEMS resonator of claim 1 wherein a cross section of the opening, parallel to the first surface, has a quadrilateral shape.

7. The MEMS resonator of claim 1 wherein the compensating material comprises an oxide.

8. The MEMS resonator of claim 1 wherein the resonant member comprises silicon.

9. The MEMS resonator of claim 1 wherein the fillable space is formed in a region of the resonating element by removal of a constituent material of the resonating element from that region.

10. The MEMS resonator of claim 1 wherein the fillable space is formed beneath the first surface of the resonating element and wherein a cross section of the fillable space parallel to the first surface has a quadrilateral shape.

11. The MEMS resonator of claim 1 wherein the fillable space is formed beneath the first surface of the resonating element and wherein the fillable space has a cuboidal shape having an opening at the first surface and bounded on five sides.

12. A microelectromechanical system (MEMS) resonator having a reduced magnitude of thermal coefficient of frequency (TCF), the MEMS resonator comprising:

a resonating element having a fillable space therein, wherein the resonating element has opposite first and second surfaces and the fillable space extends into the resonant element from the first surface without reaching the second surface; and

a compensating material disposed in the fillable space within the resonating element and characterized by a temperature coefficient of Young'"'"'s Modulus (TCE) having a sign opposite that of a TCE of the resonating element.

13. The MEMS resonator of claim 12 wherein the fillable space is defined by at least one sidewall in the resonating element that extends from the first surface of the resonant element toward the second surface of the resonant element.

14. The MEMS resonator of claim 13 wherein a depth of the fillable space is less than a distance between the first and second surfaces measured along an axis normal to the first and second surfaces.

15. The MEMS resonator of claim 12 further comprising a liner material disposed between the fillable space and the second surface.

16. The MEMS resonator of claim 12 wherein a cross section of the resonating element and fillable space is characterized by opposing sidewalls of the resonating element that constitute sides of the fillable space.

17. A microelectromechanical system (MEMS) resonator having a reduced magnitude of thermal coefficient of frequency (TCF), the MEMS resonator comprising:

a resonant member to generate an oscillatory output signal through oscillation in a mechanical resonance mode, the resonant member having first and second surfaces and an opening in the first surface that extends toward the second surface;

a liner material disposed within the opening; and

a compensating material disposed within the opening in the first surface of the resonant member and characterized by a temperature coefficient of Young'"'"'s Modulus (TCE) having a sign opposite that of a TCE of the resonant member.