Shell type actuator

• US 20060239635A1
• Filed: 02/20/2006
• Published: 10/26/2006
• Est. Priority Date: 08/20/2003
• Status: Active Grant

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University), Naval Research Laboratory (U.S. Department Of Defense)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: Craighead, Harold G., Parpia, Jeevak M., Houston, Brian H., Aubin, Keith, Zalalutdinov, Maxim, Reichenbach, Robert B.
• Granted Patent: US 7,812,502 B2
• Time in Patent Office: Days
• US Class Current: 385/147
• CPC Class Codes: G02B 26/0858 the reflecting means being moved or deformed by piezoelectric means
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator
• CPC Class Codes: H03C 1/46 Modulators with mechanically-driven or acoustically-driven parts
• CPC Class Codes: H03D 1/00 Demodulation of amplitude-modulated oscillations H03D5/00, H03D9/00, H03D11/00 take precedence
• CPC Class Codes: H03D 1/02 Details
• CPC Class Codes: H03D 3/34 by means of electromechanical devices H03D3/16 takes precedence
• CPC Class Codes: H03H 2009/02488 Vibration modes
• CPC Class Codes: H03H 2009/02511 Vertical, i.e. perpendicular to the substrate plane
• 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 9/02259 Driving or detection means
• CPC Class Codes: H03H 9/2405 of microelectro-mechanical resonators
• CPC Class Codes: H03H 9/2436 Disk resonators

Abstract

A micromechanical resonator is formed on a substrate. The resonator has a partial spherical shell clamped on an outside portion of the shell to the substrate. In other embodiments, a flat disc or other shape may be used. Movement is induced in a selected portion of the disc, inducing easily detectible out-of-plane motion. A laser is used in one embodiment to heat the selected portion of the disc and induce the motion. The motion may be detected by capacitive or interferometric techniques.

Claims

1. A micromechanical resonator comprising:

a substrate;

a partial spherical shell clamped on an outside portion of the shell to the substrate.

2. The resonator of claim 1 wherein the shell is formed of polysilicon.

3. The resonator of claim 1 having a quality factor of approximately 9,000 or above.

4. The resonator of claim 1 wherein the shell exhibits out-of-plane motion in response to local heating.

5. The resonator of claim 1 wherein the shell has a resonant frequency of at least approximately 9 MHz.

6. The resonator of claim 1 having a static deformation of approximately 0.3 nm.

7. The resonator of claim 1 and further comprising a detecting laser proximate the shell that detects deformation of the shell in response to heat.

8. The resonator of claim 1 wherein the shell deforms in response to thermal expansion, magnetostriction, optically-induced stress or piezoelectric effects.

9. A method of forming a spherical shaped micromechanical resonator, the method comprising:

forming a sacrificial layer on a substrate;

forming a polysilicon film on top of the sacrificial layer;

forming a hole through the polysilicon film;

removing a portion of the sacrificial layer to form a suspended and buckled membrane-like micromechanical structure with a hole at the center.

10. The method of claim 9 wherein the membrane-like structure is approximately 60 um in diameter or less.

11. The method of claim 9 wherein the sacrificial layer is a thermally grown oxide.

12. The method of claim 9 wherein the polysilicon film is formed using low pressure chemical vapor deposition.

13. The method of claim 12 and further comprising annealing the polycrystalline silicon film to create compression of the film.

14. The method of claim 9 wherein the hole is formed using electron beam lithography followed by a CF₄ etch.

15. The method of claim 14 and further comprising stripping off resist used in the electron beam lithography and dipping into concentrated hydrofluoric acid to remove the portion of the sacrificial layer.

16. The method of claim 9 wherein the membrane is formed using a critical point dry process.

17. A micromechanical resonator comprising:

a substrate;

a partial spherical shell clamped on an outside portion of the shell to the substrate; and

means for inducing movement of the shell.

18. The resonator of claim 17 wherein the means for inducing movement of the shell comprises a laser focused on a selected portion of the shell.

19. The resonator of claim 18 wherein the laser comprises an AC component proximate a resonant frequency of the shell.

20. The resonator of claim 17 wherein the means for inducing movement of the shell comprises a resistive heater coupled to a selected portion of the shell.

21. A micromechanical resonator comprising:

a substrate;

a disc clamped on an outside portion of the disc to the substrate;

means for inducing movement of the disc; and

means for detecting movement of the disc.

22. The resonator of claim 21 wherein the means for inducing movement of the disc comprises a laser focused on a selected portion of the disc, and the means for detecting movement of the disc comprises a photodetector that receives reflected laser light from the disc.

23. The resonator of claim 21 wherein the means for inducing movement of the disc comprises a laser focused on a selected portion of the disc, and the means for detecting movement of the disc comprises an interferometer.

24. The resonator of claim 21 wherein the resonator exhibits different modes of vibration as a function of resonant frequency of the resonator.

25. The resonator of claim 21 and further comprising means for providing feedback.

26. The resonator of claim 25 wherein the resonator operates as a frequency generator with the shell acting as a frequency determining element.

27. The resonator of claim 21 wherein the means for inducing movement of the disc uses in-plane stress to induce out-of-plane motion.

28. The resonator of claim 27 wherein the means for inducing movement affects a ring along a significant part of the circumference of the disc.

29. The resonator of claim 21 wherein the disc comprises a partial spherical shell.

30. The resonator of claim 21 wherein the disc is substantially circular.