Wireless self-powered monolithic integrated capacitive sensor and method of manufacture

• US 8,316,717 B2
• Filed: 06/29/2010
• Issued: 11/27/2012
• Est. Priority Date: 06/29/2010
• Status: Active Grant

• Current Assignee: Rogue Valley Microdevices, Inc.
• Original Assignee: Rogue Valley Microdevices, Inc.
• Inventors: Ismail, Salleh, Kayatta, Patrick
• Primary Examiner(s): ALLEN, ANDRE J
• Application Number:
  US12/826,316
• Publication Number:
  US 20110314922A1
• Time in Patent Office: 882 Days
• Field of Search: 73700-756
• US Class Current: 73/718
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 2207/015 the micromechanical device and the control or processing electronics being integrated on the same substrate
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm

Abstract

Disclosed is a wireless self-powered monolithic integrated capacitive sensor, as well as methods of manufacturing same. A single monolithic chip may include various technologies, including RF MEMS, CMOS devices and related circuitry, and physical sensor MEMS. An example pressure sensor is disclosed, including a sensing capacitor and a reference capacitor that together allow the system to provide steady output in various environmental conditions. In one embodiment a pre-fabricated circuit wafer is fusion bonded to a pre-fabricated diaphragm wafer. Doped silicon may form the monolithic structure to provide the voltage necessary to run the system.

Claims

1. A wireless self-powered monolithic integrated capacitive sensor, comprising:

a sensing capacitor that produces a first signal; and

a reference capacitor that produces a second signal;

wherein the wireless self-powered monolithic integrated capacitive sensor produces a sensing signal based on the difference between the first signal and the second signal;

a CMOS circuit wafer; and

a diaphragm wafer;

wherein the CMOS circuit wafer is fusion bonded to the diaphragm wafer.

3. The wireless self-powered monolithic integrated capacitive sensor of claim 1, wherein the wireless self-powered monolithic integrated capacitive sensor senses pressure.

4. The wireless self-powered monolithic integrated capacitive sensor of claim 1, wherein the sensing signal is not substantially affected by variations in temperature.

2. A wireless self-powered monolithic integrated capacitive sensor, comprising:

a sensing capacitor that produces a first signal; and

a reference capacitor that produces a second signal;

wherein the wireless self-powered monolithic integrated capacitive sensor produces a sensing signal based on the difference between the first signal and the second signal;

a circuit wafer having one or more metal silicide plates; and

a diaphragm wafer having one or more metal silicide bump springs;

wherein a metal silicide plate is in electrical contact with a metal silicide bump spring.

5. A wireless self-powered monolithic integrated capacitive sensor, comprising:

RF MEMS;

a CMOS device; and

physical sensor MEMS.

6. The wireless self-powered monolithic integrated capacitive sensor of claim 5, further comprising:

a circuit wafer; and

a diaphragm wafer.

7. The wireless self-powered monolithic integrated capacitive sensor of claim 5, further comprising:

a circuit wafer fusion bonded to a diaphragm wafer.

8. The wireless self-powered monolithic integrated capacitive sensor of claim 5, further comprising:

a circuit wafer having one or more metal silicide plates; and

a diaphragm wafer having one or more metal silicide bump springs;

wherein a metal silicide plate is in electrical contact with a metal silicide bump spring.

9. The wireless self-powered monolithic integrated capacitive sensor of claim 5, wherein the wireless self-powered monolithic integrated capacitive sensor senses pressure.

10. The wireless self-powered monolithic integrated capacitive sensor of claim 5, wherein the sensor'"'"'s output is not substantially affected by variations in temperature.

11. A method of manufacturing a wireless self-powered monolithic integrated capacitive sensor, comprising the steps of:

fusion bonding a CMOS circuit silicon wafer to a diaphragm silicon wafer.

12. The method of claim 11, further comprising the steps of:

etching an isolation trench on the CMOS circuit silicon wafer or the diaphragm silicon wafer to electrically isolate a first portion of the etched wafer from a second portion of the etched wafer.

13. The method of claim 11, further comprising the steps of:

applying form field oxide by local oxidation of silicon (LOCOS) to the CMOS circuit silicon wafer or the diaphragm silicon wafer.

14. The method of claim 11, further comprising the steps of:

applying one or more metal silicide plates to the CMOS circuit silicon wafer or the diaphragm silicon wafer.

16. The method of claim 11, further comprising the steps of:

grinding down the CMOS circuit silicon wafer or the diaphragm silicon wafer to a predetermined thickness.

17. The method of claim 11, further comprising the steps of:

adding heavily doped n++ regions and p++ regions in either the CMOS circuit silicon wafer or the diaphragm silicon wafer.

18. The method of claim 11, further comprising the steps of:

etching a sensing window in either the CMOS circuit silicon wafer or the diaphragm silicon wafer.

15. A method of manufacturing a wireless self-powered monolithic integrated capacitive sensor, comprising the steps of:

fusion bonding a circuit silicon wafer to a diaphragm silicon wafer; and

creating an electrically connective bump spring containing field oxide or metal silicide on the circuit silicon wafer or the diaphragm silicon wafer.