Single-sided differential pressure sensor

• US 5,969,591 A
• Filed: 06/03/1996
• Issued: 10/19/1999
• Est. Priority Date: 03/28/1991
• Status: Expired due to Fees

• Current Assignee: Invensys Systems Incorporated (Invensys PLC)
• Original Assignee: The Foxboro Company (Schneider Electric SE)
• Inventors: Fung, Clifford D.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Vu, Bao Q
• Application Number:
  US08/657,177
• Time in Patent Office: 1,233 Days
• Field of Search: 338/4, 338/6, 338/36, 338/42, 73/721
• US Class Current: 338/42
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 19/0038 being part of the housing other details about the housing G01L19/14
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: G01L 19/148 Details about the circuit board integration, e.g. integrated with the diaphragm surface or encapsulation
• 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 9/0055 bonded on a diaphragm

Abstract

A single-sided differential pressure sensing chip having a cavity formed in the top surface of a substrate, a deformable diaphragm spanning the cavity, and a pressure passage connecting the top surface of the substrate with the cavity, and a method of making the same are described. A first fluid pressure applied to the top surface of the substrate in the vicinity of the diaphragm exerts a force on the top surface of the diaphragm, and a second fluid pressure applied to the top surface of the substrate near the pressure passage exerts a force on the bottom surface of the diaphragm. The diaphragm deflects in response to the forces exerted upon it, and a sensing element detects the flexing of the diaphragm. The pressure sensing chip can be contained within a housing structure formed of a carrier and a cap. The housing structure forms a first pressure chamber that communicates with the top surface of the diaphragm and a second pressure chamber that communicates with the bottom surface of the diaphragm through the pressure passage. The cap can include a first opening for connecting a first fluid pressure with the first chamber, and a second opening for connecting a second fluid pressure with the second chamber.

Claims

1. Differential pressure sensor apparatus having an epitaxial semiconductor structure, said pressure sensor comprising

a carrier having a carrier floor and a carrier wall extending from the carrier floor,

a silicon substrate seated on the carrier floor and having a top surface defining a recess therein,

a cap mounted on the carrier wall, the cap having a proximal aperture exposed to fluid at a first fluid pressure and a distal aperture exposed to fluid at a second fluid pressure,

a polysilicon diaphragm having

a periphery secured to said substrate,

a deflecting region spanning the recess,

an upper surface that, together with the carrier wall and said cap, defines an upper chamber, the upper chamber being in fluid communication, through the distal aperture in said cap, with the fluid at a second fluid pressure, and

a lower surface that, together with the recess in the top surface of the substrate, defines a lower chamber, the lower chamber being in fluid communication, through the proximal aperture in said cap, with the fluid at a first fluid pressure,

electrical detection means in communication with said diaphragm for generating an output signal indicative of the deflection of the deflection region due to a pressure differential exerted across the diaphragm by the first and second fluid pressures.

2. Pressure sensor apparatus in accordance with claim 1, further comprising means for dividing the upper chamber into

a proximal chamber in fluid communication with the fluid at a first fluid pressure and

a distal chamber in fluid communication with the fluid at a second fluid pressure.

3. Pressure sensor apparatus in accordance with claim 2, wherein said means for dividing the upper chamber includes

a pressure seal for maintaining different pressures in the proximal chamber and in the distal chamber.

4. Pressure sensor apparatus according to claim 1, wherein the lower chamber has a floor disposed at a depth selected such that the floor forms a pressure stop for deflection of said diaphragm.

5. Pressure sensor apparatus according to claim 4 further comprising a release material coating for diminishing sticking of said diaphragm to the floor of the lower chamber.

6. A pressure sensor apparatus according to claim 1 further comprising

a conductive pad mounted on said carrier,

a conductive wire electrically coupling said electrical detection means with said conductive pad, and

connective means mounted on said carrier and electrically coupled with said conductive pad for providing electrical connections to said electrical detection means.

7. Pressure sensor apparatus in accordance with claim 1, further comprising a pressure passage between the upper chamber and the lower chamber.

9. Pressure sensor apparatus in accordance with claim 1, further comprising coating means for coating said cavity.

10. Pressure sensor apparatus in accordance with claim 1, further comprising means for isolating said electrical detection means from said diaphragm.

11. Pressure sensor apparatus in accordance with claim 1, further comprising means for isolating said electrical detection means from said second fluid.

13. Pressure sensor apparatus in accordance with claim 3 wherein said pressure seal comprises a pressure tight seal.

14. Pressure sensor apparatus in accordance with claim 3 wherein said pressure seal comprises a polymeric sealing material.

15. Pressure sensor apparatus according to claim 5 wherein said release material comprises a coating selected from a group consisting of an oxide coating and a nitride coating.

16. Pressure sensor apparatus in accordance with claim 1, wherein said cap is of a ceramic material.

17. Pressure sensor apparatus in accordance with claim 1, further comprising a dielectric layer between said diaphragm and said electrical detection means.

18. Pressure sensor apparatus in accordance with claim 17, wherein said dielectric layer comprises a silicon oxide layer between said diaphragm and a silicon nitride layer.

19. Pressure sensor apparatus in accordance with claim 7, wherein said pressure passage comprises an aperture in said diaphragm.

20. Pressure sensor apparatus in accordance with claim 7, wherein said pressure passage comprises a channel connecting said upper chamber to said lower chamber.

8. Differential pressure sensor apparatus having a semiconductor structure and comprising

A. a silicon substrate having a top surface and having a cavity recessing said top surface,

B. a polysilicon diaphragm deposited over and secured to said substrate and spanning the cavity, said diaphragm having opposite top and bottom faces,

C. a first pressure port mounted with said substrate and disposed for receiving a first fluid pressure from a first direction along a first axis,

D. an opening through a deflecting portion of said diaphragm, said opening for communicating to the cavity a first fluid pressure applied to said first pressure port,

E. a second pressure port mounted with said substrate and disposed for receiving a second fluid pressure from the first direction, said second pressure port being structured for applying the second fluid pressure to the span of the top face of said diaphragm over said cavity,

F. electrical detection means for detecting the deflection of said diaphragm due to a pressure differential exerted across the diaphragm by the first and second fluid pressures,

G. a housing mounting said pressure ports and said substrate and for directing the first fluid pressure to a first portion of the diaphragm proximal to the pressure passage and for directing the second fluid pressure to a second portion of the diaphragm distal to the pressure passage,

wherein said housing means includes

i. a carrier for mounting said substrate, and

ii. a cap assembled with said carrier, said first and second pressure ports being mounted on said cap,

whereby said first and second fluid pressures are applied to the same side of the pressure sensor apparatus and act substantially exclusively on different faces of said diaphragm.

12. Differential pressure sensor apparatus having a semiconductor structure and comprising

A. a silicon substrate having a top surface and having a cavity recessing said top surface,

B. a polysilicon diaphragm deposited over and secured to said substrate and spanning the cavity, said diaphragm having opposite top and bottom faces,

C. a first pressure port mounted with said substrate and disposed for receiving a first fluid pressure from a first direction along a first axis,

D. an opening through a deflecting portion of said diaphragm, said opening for communicating to the cavity a first fluid pressure applied to said first pressure port,

E. a second pressure port mounted with said substrate and disposed for receiving a second fluid pressure from the first direction, said second pressure port being structured for applying the second fluid pressure to the span of the top face of said diaphragm over said cavity,

F. electrical detection means for detecting the deflection of said diaphragm due to a pressure differential exerted across the diaphragm by the first and second fluid pressures,

G. means forming a first chamber proximal to the pressure passage and forming a second chamber distal to the pressure passage,

whereby said first and second fluid pressures are applied to the same side of the pressure sensor apparatus and act substantially exclusively on different faces of said diaphragm.