Integrated pressure and acceleration measurement device and a method of manufacture thereof

• US 20060261424A1
• Filed: 02/02/2004
• Published: 11/23/2006
• Est. Priority Date: 01/31/2003
• Status: Abandoned Application

• Current Assignee: Melexis NV (Sensinnovat BVBA)
• Original Assignee: Melexis NV (Sensinnovat BVBA)
• Inventors: Van Der Wiel, Appolonius Jacobus A.
• Application Number:
  US10/544,038
• Publication Number:
  US 20060261424A1
• Time in Patent Office: Days
• US Class Current: 257/417
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 7/02 containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS] B81B7/04 takes precedence
• CPC Class Codes: G01L 19/0092 Pressure sensor associated with other sensors, e.g. for measuring acceleration or temperature G01L9/025, G01L9/045, G01L9/065, G01L9/085, G01L9/105, G01L9/125, G01L19/02, G01L19/04 take precedence; measuring two or more variable G01D21/02; temperature sensors with pressure compensation G01K1/26
• CPC Class Codes: G01P 13/00 Indicating or recording presence, absence, or direction, of movement electric switches H01H; counting moving objects G06M7/00
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 3/22 transferred to the indicator by electric or magnetic means

Abstract

An integrated pressure and acceleration sensing device comprises three silicon wafers (101-103) bonded together by silicon fusion bonding. The wafers (101-103) are shaped so as to define a pressure sensitive element (113) and an acceleration sensing element (112). At least one stress measuring means linked to each of said pressure sensing and acceleration sensing elements (113,112) which are operable to generate a measurement signal responsive to deformation of said stress measuring means and which is indicative of the sensed values of pressure and/or acceleration. The device is manufactured by shaping said silicon wafers (101-103) define parts which act to form pressure and acceleration sensing elements (113,112) and bonding said silicon wafers (101-103) together using bonding techniques such as silicon fusion bonding, anodic bonding or glass-frit bonding. The wafers (101-103) are polished or lapped said to produce a relatively thin single integrated device.

Claims

1. An integrated pressure and acceleration sensing device comprising three silicon wafers bonded together by silicon fusion bonding, said wafers being shaped so as to define a pressure sensitive element and an acceleration sensing element, at least one stress measuring means linked to each of said pressure sensing and acceleration sensing elements which are operable to generate a measurement signal responsive to deformation of said stress measuring means and which is indicative of the sensed values of pressure and/or acceleration.

2. An integrated pressure and acceleration sensing device as claimed in claim 1 wherein said wafers form a three layer sandwich, said sandwich having top, centre and bottom wafers.

3. An integrated pressure and acceleration sensing device as claimed in claim 2 wherein the centre wafer has a mass formed integrally therewith which forms the acceleration sensing element.

4. An integrated pressure and acceleration sensing device as claimed in claim 2 wherein the centre wafer has a membrane formed integrally therewith which forms the pressure sensing element.

5. An integrated pressure and acceleration sensing device as claimed in claim 2 wherein the centre wafer carries additional circuitry for control and or operation and or configuration of the integrated device.

6. An integrated pressure and acceleration sensing device as claimed in any one of claim 2 wherein said top and bottom wafers form matching halves whereby when the matching halves are brought together they define cavities in which the sensing elements are housed.

7. An integrated pressure and acceleration sensing device as claimed in claim 6 wherein either the top wafer or the bottom wafer is shaped to provide an opening through which the pressure sensing element can be exposed to ambient air pressure.

8. An integrated pressure and acceleration sensing device as claimed in claim 6 wherein the top wafer and or the bottom wafer are shaped to provide a recess, thereby defining an area where electrical connections can be made to the circuitry on the centre wafer.

9. An integrated pressure and acceleration sensing device as claimed in claim 2 wherein the mass forming the acceleration sensing element has a relatively thin section and a relatively thick section.

10. An integrated pressure and acceleration sensing device as claimed in claim 9 wherein the stress measuring means linked to the acceleration sensing element are provided on the relatively thin section of the acceleration sensing element.

11. An integrated pressure and acceleration sensing device as claimed in claim 1 wherein the stress measuring means comprise piezoresistors.

12. An integrated pressure and acceleration sensing device as claimed in claim 2, wherein two shallow recesses are provided on said bottom wafer facing said centre wafer and one shallow recess and one deep recess are provided on said top wafer facing said centre wafer, one said recess on the bottom wafer in combination with the deep recess on the top wafer member defining a cavity to house the pressure sensing element and the other said recess on the bottom wafer in combination with the shallow recess on the top member defining a cavity to house said acceleration sensing element.

13. An integrated pressure and acceleration sensing device as claimed in claim 2 two shallow recesses are provided on said centre wafer facing said bottom wafer and one shallow recess and one deep recess are provided on said top wafer facing said centre wafer, one said recess on the centre wafer in combination with the deep recess on the top wafer member defining a cavity to house the pressure sensing element and the other said recess on the centre wafer in combination with the shallow recess on the top member defining a cavity to house said acceleration sensing element.

14. An integrated pressure and acceleration sensing device as claimed in claim 12 wherein the deep recess in the top member is processed to provide an opening through which the pressure sensing element can be exposed to ambient air pressure.

15. An integrated pressure and acceleration sensing device as claimed in claim 2 wherein the top wafer is a structured silicon top wafer and bonded to the centre wafer by anodic bonding to produce a silicon cap which resists standard moulding during packaging.

16. An integrated pressure and acceleration sensing device as claimed in claim 15 wherein the top cap is thinned and filled with thin gel to provide a low g sensitivity pressure sensing element.

17. An integrated pressure and acceleration sensing device as claimed in claim 1 wherein the total thickness of the device is less than 200 microns.

24. An integrated pressure and acceleration sensing device as claimed in claim 1 wherein the device is made by the method of claim 18.

25. An integrated pressure and acceleration sensing device as claimed in claim 13 wherein the deep recess in the top member is processed to provide an opening through which the pressure sensing element can be exposed to ambient air pressure.

18. A method of forming an integrated pressure and acceleration sensing device comprising a silicon-silicon-silicon assembly, said method comprising shaping said silicon wafers by etching such that said shaped wafers define parts which act to form pressure and acceleration sensing elements, bonding said silicon wafers together using silicon fusion bonding, and polishing or lapping said bonded wafers to produce a relatively thin single integrated device.

19. A method of forming an integrated pressure and acceleration sensing device as claimed in claim 18 wherein said wafers are shaped using Potassium Hydroxide (KOH) etching.

20. A method of forming an integrated pressure and acceleration sensing device as claimed in claim 18 wherein said wafers are shaped using plasma etching.

21. A method of forming an integrated pressure and acceleration sensing device as claimed in claim 18 wherein one or more of the wafers are bonded together using anodic bonding.

22. A method of forming an integrated pressure and acceleration sensing device as claimed in claim 18 wherein the device is thinned by back-grinding one or more wafers.

23. A method of forming an integrated pressure and acceleration sensing device as claimed in claim 18 wherein etching is used to thin areas of the wafers forming said pressure and acceleration sensing elements.