Pressure sensor including deformable pressure vessel(s)

• US 9,541,462 B2
• Filed: 08/29/2014
• Issued: 01/10/2017
• Est. Priority Date: 08/29/2014
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: Kionix Incorporated (ROHM Co., Ltd.)
• Inventors: Adams, Scott G., Blackmer, Charles W., Lynch, Kristin J.
• Primary Examiner(s): ALLEN, ANDRE J
• Application Number:
  US14/474,059
• Publication Number:
  US 20160061679A1
• Time in Patent Office: 865 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 2207/012 the micromechanical device and the control or processing electronics being separate parts in the same package
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: B81C 1/00 Manufacture or treatment of devices or systems in or on a substrate B81C3/00 takes precedence
• CPC Class Codes: B81C 1/00047 Cavities
• CPC Class Codes: B81C 1/00666 Treatments for controlling internal stress or strain in MEMS structures
• CPC Class Codes: B81C 2201/0167 by adding further layers of materials having complementary strains, i.e. compressive or tensile strain
• CPC Class Codes: B81C 2201/017 Methods for controlling internal stress of deposited layers not provided for in B81C2201/0164 - B81C2201/0169
• CPC Class Codes: G01L 13/00 Devices or apparatus for measuring differences of two or more fluid pressure values
• CPC Class Codes: G01L 13/02 using elastically-deformable members or pistons as sensing elements
• CPC Class Codes: G01L 9/0027 using variations in ohmic resistance
• CPC Class Codes: G01L 9/003 using variations in capacitance
• CPC Class Codes: G01L 9/0055 bonded on a diaphragm
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01L 9/008 using piezoelectric devices piezoelectric resonators G01L9/0022; surface acoustic waves G01L9/0025
• CPC Class Codes: G01L 9/0082 Transmitting or indicating the displacement of capsules by electric, electromechanical, magnetic, or electromechanical means G01L9/0008 takes precedence
• CPC Class Codes: G01P 15/006 by making use of fluid seismic masses
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: H01L 21/00 Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof

Abstract

Techniques are described herein that perform pressure sensing using pressure sensor(s) that include deformable pressure vessel(s). A pressure vessel is an object that has a cross section that defines a void. A deformable pressure vessel is a pressure vessel that has at least one curved portion that is configured to structurally deform (e.g., bend, shear, elongate, etc.) based on a pressure difference between a cavity pressure in a cavity in which at least a portion of the pressure vessel is suspended and a vessel pressure in the pressure vessel.

Claims

1. A pressure sensor comprising:

a semiconductor substrate that includes a first cavity;

a pressure vessel made from a dielectric lining that is formed in a trench that has an aspect ratio greater than four, the pressure vessel having a cross section that defines a void, the pressure vessel having at least one curved portion that is configured to structurally deform based on a pressure difference between a cavity pressure in the first cavity and a vessel pressure in the pressure vessel, at least a first portion of the pressure vessel suspended in the first cavity; and

a first transducer coupled to the first portion of the pressure vessel, the first transducer having an attribute that changes with structural deformation of the pressure vessel.

2. The pressure sensor of claim 1, wherein the first transducer comprises:

a deformable capacitive structure configured to provide a first capacitance that changes with the structural deformation of the pressure vessel.

3. The pressure sensor of claim 2, wherein the deformable capacitive structure comprises:

a plurality of interleaved capacitor plates.

4. The pressure sensor of claim 2, wherein the deformable capacitive structure comprises:

a first set of capacitor plates interleaved with a second set of capacitor plates;

wherein the first set of capacitor plates is configured to move with respect to the second set of capacitor plates based on the structural deformation of the pressure vessel to change the first capacitance.

5. The pressure sensor of claim 4, wherein the deformable capacitive structure is further configured to provide a second capacitance that changes with the structural deformation of the pressure vessel;

wherein the deformable capacitive structure further comprises;

a third set of capacitor plates interleaved with a fourth set of capacitor plates;

wherein the third set of capacitor plates is configured to move with respect to the fourth set of capacitor plates based on the structural deformation of the pressure vessel to change the second capacitance; and

wherein the change of the first capacitance is opposite the change of the second capacitance.

6. The pressure sensor of claim 1, wherein the first transducer comprises:

a piezoelectric element configured to generate a charge based on a force that is applied to the piezoelectric element as a result of the structural deformation of the pressure vessel.

7. The pressure sensor of claim 1, wherein the first transducer comprises:

a piezoresistive element having a resistance that changes based on a force that is applied to the piezoresistive element as a result of the deformation of the pressure vessel.

8. The pressure sensor of claim 1, wherein a second portion of the pressure vessel is external to the first cavity;

and

wherein at least a part of the second portion is removed to provide a vessel pressure port that exposes a first environment in the pressure vessel to a second environment that is external to the pressure vessel.

9. The pressure sensor of claim 1, wherein a second portion of the pressure vessel is external to the first cavity;

wherein the semiconductor substrate includes a second cavity that is external to the first cavity;

wherein at least a part of the second portion of the pressure vessel is included in the second cavity; and

wherein the part of the second portion has an opening that exposes a first environment in the pressure vessel to a second environment in the second cavity.

10. The pressure sensor of claim 9, further comprising:

a lid that includes a hole to provide a vessel pressure port that exposes the first environment and the second environment to a third environment that is external to the pressure sensor.

11. The pressure sensor of claim 1, wherein a surrounding rectangle is defined as a rectangle having a smallest area that surrounds the first cavity in a plane of a wafer from which the pressure sensor is fabricated, the surrounding rectangle having first parallel sides and second parallel sides that are perpendicular the first parallel sides, each first parallel side having a first length, each second parallel side having a second length that is less than or equal to the first length;

and

wherein a distance between a first point at which the pressure vessel couples to the substrate and a second point at which the first transducer couples to the substrate is less than or equal to one-third of the second length.

12. The pressure sensor of claim 1, wherein a surrounding rectangle is defined as a rectangle having a smallest area that surrounds the first cavity in a plane of a wafer from which the pressure sensor is fabricated, the surrounding rectangle having first parallel sides and second parallel sides that are perpendicular the first parallel sides, each first parallel side having a first length, each second parallel side having a second length that is less than or equal to the first length;

and

wherein a distance between a first point at which the pressure vessel couples to the substrate and a second point at which the pressure vessel couples to the first transducer is less than or equal to one-third of the second length.

13. The pressure sensor of claim 1, wherein a surrounding rectangle is defined as a rectangle having a smallest area that surrounds the first cavity in a plane of a wafer from which the pressure sensor is fabricated, the surrounding rectangle having first parallel sides and second parallel sides that are perpendicular the first parallel sides, each first parallel side having a first length, each second parallel side having a second length that is less than or equal to the first length;

and

wherein a distance between a first point at which the first transducer couples to the pressure vessel and a second point at which the first transducer couples to the substrate is less than or equal to one-third of the second length.

14. The pressure sensor of claim 1, wherein a maximum width of the void is less than or equal to two microns.

15. The pressure sensor of claim 1, wherein the at least one curved portion of the pressure vessel includes at least one serpentine portion having a serpentine shape.

16. The pressure sensor of claim 1, wherein the at least one curved portion of the pressure vessel includes at least one spiral portion having a spiral shape.

17. The pressure sensor of claim 1, wherein the at least one curved portion of the pressure vessel includes at least one semicircular portion having a semicircular shape.

18. The pressure sensor of claim 1, wherein the at least one curved portion of the pressure vessel includes a plurality of concentric semicircular portions, each semicircular portion having a semicircular shape.

19. The pressure sensor of claim 1, further comprising:

a connector coupled to the pressure vessel at a first connection point and coupled to the first transducer at a second connection point;

wherein the first connection point has a first motion resulting from the deformation of the pressure vessel; and

wherein the connector is configured to cause the second connection point to have a second motion, which is an amplified version of the first motion.

20. The pressure sensor of claim 1, further comprising:

a connector coupled to the pressure vessel at a first connection point and coupled to the first transducer at a second connection point;

wherein the first connection point has a first motion resulting from the deformation of the pressure vessel; and

wherein the connector is configured to cause the second connection point to have a second motion, which is a de-amplified version of the first motion.

21. The pressure sensor of claim 1, further comprising:

a connector coupled between the pressure vessel and the first transducer, the connector having an anisotropic stiffness.

22. The pressure sensor of claim 1, further comprising:

a second pressure vessel having a cross section that defines a second void, the second pressure vessel having at least one curved portion that is configured to structurally deform based on a pressure difference between a cavity pressure in a second cavity that is included in the semiconductor substrate and a vessel pressure in the second pressure vessel, at least a first portion of the second pressure vessel suspended in the second cavity; and

a second transducer coupled to the first portion of the second pressure vessel, the second transducer having an attribute that changes with structural deformation of the second pressure vessel;

wherein the first transducer is configured to provide a first signal based on a change of the attribute of the first transducer that results from at least one of an acceleration of the pressure vessel or the pressure difference between the cavity pressure in the first cavity and the vessel pressure in the first pressure vessel; and

wherein the second transducer is configured to provide a second signal based on a change of the attribute of the second transducer that results from at least one of the acceleration of the pressure vessel or the pressure difference between the cavity pressure in the second cavity and the vessel pressure in the second pressure vessel.

23. The pressure sensor of claim 22, wherein the pressure sensor is configured such that a difference between the first signal and the second signal provides a measure of the acceleration of the pressure sensor and such that a sum of the first signal and the second signal provides a measure of a pressure difference.

24. The pressure sensor of claim 22, wherein the pressure sensor is configured such that a sum of the first signal and the second signal provides a measure of the acceleration of the pressure sensor and such that a difference between the first signal and the second signal provides a measure of a pressure difference.

25. The pressure sensor of claim 22, wherein the first cavity and the second cavity are same.

26. A method comprising:

providing a semiconductor substrate that includes a cavity;

fabricating a pressure vessel from a dielectric lining that is formed in a trench that has an aspect ratio greater than four, the pressure vessel having a cross section that defines a void, the pressure vessel having at least one curved portion that is configured to structurally deform based on a pressure difference between a cavity pressure in the cavity and a vessel pressure in the pressure vessel, at least a portion of the pressure vessel suspended in the cavity; and

fabricating a transducer coupled to the portion of the pressure vessel, the transducer having an attribute that changes with structural deformation of the pressure vessel.

27. A method comprising:

receiving a cavity pressure in a cavity that is included in a semiconductor substrate of a pressure sensor;

receiving a vessel pressure in a pressure vessel of the pressure sensor that is made from a dielectric lining that is formed in a trench that has an aspect ratio greater than four, the pressure vessel having a cross section that defines a void and having at least one curved portion that is configured to structurally deform based on a pressure difference between the cavity pressure and the vessel pressure, at least a portion of the pressure vessel being suspended in the cavity; and

measuring an attribute of a transducer that is coupled to the portion of the pressure vessel, the attribute changing with structural deformation of the pressure vessel.