Capacitive pressure sensor with a cantilever member

• US 7,478,559 B2
• Filed: 12/03/2004
• Issued: 01/20/2009
• Est. Priority Date: 12/04/2003
• Status: Expired due to Fees

• Current Assignee: National University of Singapore
• Original Assignee: National University of Singapore
• Inventors: Tan, Woei Wan, Ge, Pei, Phang, Jyh Siong, Tay, Eng Hock Francis
• Primary Examiner(s): Lefkowitz; Edward
• Assistant Examiner(s): ROY, PUNAM P
• Application Number:
  US10/581,782
• Publication Number:
  US 20080022777A1
• Time in Patent Office: 1,509 Days
• Field of Search: 737/18, 737/24, 737/80, 738/626.26, 73862636-862939, 438/52, 438/53
• US Class Current: 73/718
• CPC Class Codes: G01F 23/18 Indicating, recording or alarm devices actuated electrically
• CPC Class Codes: G01L 1/148 using semiconductive material, e.g. silicon
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm

Abstract

A capacitive pressure sensing device comprising, a base member, a diaphragm member deflectable under an external pressure, a cantilever member disposed between the base member and the diaphragm member and supported on a support structure, wherein the base member and the cantilever member form a capacitor structure of the device and wherein deflection of the diaphragm member beyond a threshold value causes the cantilever member to deflect to cause a capacitive change in the capacitor structure.

Claims

1. A capacitive pressure sensing device comprising:

a base member;

a diaphragm member deflectable under an external pressure;

a cantilever member disposed between the base member and the diaphragm member and supported on a support structure; and

a contact member moveable relative to the cantilever member under deflection of the diaphragm member and separated by a gap from the cantilever member in a state when no pressure is applied to the diaphragm member,

wherein the base member and the cantilever member form acapacitor structure of the device, and

wherein deflection of the diaphragm member beyond a threshold value causes the contact member to contact the cantilever member causing the cantilever member to deflect to cause a capacitive change in the capacitor structure.

2. The device as claimed in claim 1, wherein the contact member is disposed on the base member.

3. The device as claimed in any one of claim 2, wherein the support structure supporting the cantilever member is disposed on the diaphragm member.

4. The device as claimed in claim 1, wherein the contact member is disposed on the diaphragm member.

5. The device as claimed in claim 4, wherein the support structure supporting the cantilever member is disposed on the base member.

6. The device as claimed in any one of claim 1, wherein the contact member comprises a contact area disposed symmetrically around said support structure supporting the cantilever member.

7. The device as claimed in any one of claim 1, wherein the support structure supporting the cantilever member centrally supports the cantilever member.

8. The device as claimed in any one of claim 1, wherein the cantilever member comprises polysilicon.

9. The device as claimed in any one of claim 1, wherein the diaphragm member comprises polysilicon.

10. The device as claimed in any one of claim 1, wherein the base member comprises a silicon wafer.

11. The device as claimed in any one of claim 1, wherein the base member comprises a glass substrate.

12. The device as claimed in any one of claim 1, wherein the contact member comprises a nitride material.

13. A method of pressure sensing comprising:

providing a contact member moveable relative to the cantilever member under deflection of a diaphragm member and separated by a gap from the cantilever member in a state when no pressure is applied to a diaphragm member; and

deflecting the diaphragm member under an external pressure beyond a threshold value to cause the contact member to contact the cantilever member causing the cantilever member to deflect under the influence of the diaphragm member,

wherein deflection of the cantilever member causes a capacitive change in a capacitive structure including the cantilever member.

14. A method of fabricating a pressure sensing device comprising:

forming a base member;

forming a diaphragm member deflectable under an external pressure;

forming a cantilever member disposed between the base member and the diaphragm member and supported on a support structure;

forming a contact member moveable relative to the cantilever member under deflection of the diaphragm member and separated by a gap from a cantilever member in a state when no pressure is applied to the diaphragm member;

wherein the base member and the cantilever member form a capacitor structure of the device; and

wherein deflection of the diaphragm member beyond a threshold value causes the contact member to contact the cantilever member causing the cantilever member to deflect to cause a capacitive change in the capacitor structure.

15. The method as claimed in claim 14, wherein forming the cantilever member comprises utilising thin film deposition techniques and sacrificial etching techniques.

16. The method as claimed in claims 14, wherein forming the diaphragm member comprises utilising thin film deposition techniques and etching techniques.

17. The method as claimed in any one of claims 14, wherein forming the base member comprises providing a substrate.

18. The method as claimed in claim 17, wherein forming the base member comprises etching the substrate.