Semiconductor nitride pressure microsensor and method of making and using the same
First Claim
1. An integrated microsensor for sensing pressure of a fluid comprising:
- a micromachined membrane having a peripheral edge, which membrane is bowed by stress formed in the membrane during its fabrication;
a substrate coupled to at least a portion of said peripheral edge to define a microcavity between said substrate and membrane to which microcavity said fluid whose pressure is to be sensed is communicated; and
an integrated piezoelectric strain sensor coupled to said micromachined membrane to generate a signal responsive to deformation of said membrane and hence responsive to said pressure of said fluid in said microcavity, where said integrated strain sensor comprises a strain-FET comprised of an AlGaN/GaN heterostructure having an AlGaN/GaN interface where deformation of said membrane is coupled as strain to said AlGaN/GaN interface.
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Abstract
An integrated microsensor includes a bowed micromachined membrane coupled to a substrate to define a microcavity therebetween. An integrated strain sensor is coupled to the micromachined membrane to generate a signal responsive to (deformation of the membrane and hence responsive to the pressure of the fluid in the microcavity. A frame is coupled to the peripheral edge of the membrane to assist in enlarging the microcavity. The membrane is composed of a nitride of B, Al, Ga, In, Tl or combinations thereof, or more particularly of p-type GaN where the frame is comprised of n-type GaN. The membrane and frame are fabricated using a photoelectrochemical etching technique. The fabrication of the integrated strain sensor creates stresses across the membrane. The strain sensor comprises an integrated circuit strain-FET. The strain-FET comprises an AlGaN/GaN heterostructure having an AlGaN/GaN interface where deformation of the membrane is coupled as strain to the AlGaN/GaN piezoelectric interface.
50 Citations
10 Claims
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1. An integrated microsensor for sensing pressure of a fluid comprising:
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a micromachined membrane having a peripheral edge, which membrane is bowed by stress formed in the membrane during its fabrication;
a substrate coupled to at least a portion of said peripheral edge to define a microcavity between said substrate and membrane to which microcavity said fluid whose pressure is to be sensed is communicated; and
an integrated piezoelectric strain sensor coupled to said micromachined membrane to generate a signal responsive to deformation of said membrane and hence responsive to said pressure of said fluid in said microcavity, where said integrated strain sensor comprises a strain-FET comprised of an AlGaN/GaN heterostructure having an AlGaN/GaN interface where deformation of said membrane is coupled as strain to said AlGaN/GaN interface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of sensing pressure in a microcavity comprising:
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providing said microcavity between a substrate and a membrane, wherein said membrane is comprised of a p-type nitride of B, Al, Ga, In, or Tl and wherein said substrate is comprised at least in part of an n-type nitride of B, Al, Ga, In, or Tl, said microcavity formed between said p-type and n-type layers using a photoelectrochemical etching technique;
providing an integrated strain-FET comprised of an AlGaN/GaN heterostructure having an AlGaN/GaN interface where deformation of the membrane is coupled as strain to said AlGaN/GaN interface coupling the strain FET to said membrane thereby bowing said membrane;
deforming said membrane by a pressure change in said microcavity;
straining said strain FET by deformation of said membrane, where straining said strain FET by deformation of said membrane comprises straining a heterojunction in said strain FET; and
sensing a change in an electrical parameter of said strain FET in response to said pressure change in said microcavity.
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Specification