Pressure sensor structure and fabrication method thereof

Abstract

A pressure sensing structure includes a semiconductor substrate, a composite thin film, a cavity, a semiconductor resistor, and a cover plate. The semiconductor substrate has a first surface and a second surface on opposite sides. The composite thin film is embedded in the semiconductor substrate and located on the first surface. The cavity is disposed within the semiconductor substrate and extends from the second surface to the composite thin film. The semiconductor resistor is disposed on the composite thin film and located directly above the cavity. The cover plate is bonded to the semiconductor substrate to seal the cavity.

Claims

1. A pressure sensing structure, comprising: A semiconductor substrate having a first surface and a second surface on opposite sides; A composite film is embedded in the semiconductor substrate and located on the first surface, wherein the composite film includes a semiconductor filling layer and an insulating layer covering the semiconductor filling layer, and the top surface of the composite film and the first surface of the semiconductor substrate are on the same plane; a cavity is disposed in the semiconductor substrate and extends from the second surface to the composite film; a semiconductor resistor is disposed on the composite film and located directly above the cavity; And a cover plate, bonded to the semiconductor substrate, to seal the cavity.

2. The pressure sensing structure as claimed in claim 1, wherein the semiconductor filling layer comprises undoped or lightly doped polycrystalline silicon, and the insulating layer comprises silicon oxide.

3. The pressure sensing structure as described in claim 1, wherein, in the vertical projection direction, the boundary of the cavity is within the boundary of the composite film.

4. The pressure sensing structure as described in claim 1 further includes: An interconnect layer is disposed above the semiconductor substrate; A pressure-sensing opening penetrates the interconnect layer and is located directly above the semiconductor resistor; And a transistor is disposed in the semiconductor substrate.

5. The pressure sensing structure as described in claim 4, wherein the interconnect layer is electrically connected to the transistor and the semiconductor resistor.

6. The pressure sensing structure as described in claim 4, wherein the transistor includes a gate structure, and the composition of the semiconductor resistor is the same as the composition of the gate structure.

7. The pressure sensing structure as claimed in claim 1, wherein the semiconductor resistor comprises doped polysilicon and the semiconductor resistor constitutes a Wheatstone bridge circuit.

8. The pressure sensing structure as described in claim 1, wherein the semiconductor resistor comprises: A first resistor and a second resistor, each having a first conductivity type, are disposed separately along a first direction; The resistors include a third resistor and a fourth resistor, each having a second conductivity type, and are arranged separately along a second direction, wherein the second direction is different from the first direction, the major axes of the first resistor and the second resistor are both in the first direction, and the major axes of the third resistor and the fourth resistor are both in the second direction.

9. The pressure sensing structure as described in claim 1, wherein the semiconductor resistor comprises: A first resistor and a second resistor are separately disposed along a first direction; A third resistor and a fourth resistor are separately disposed along a second direction, wherein the second direction is different from the first direction, the major axes of the first resistor, the second resistor, the third resistor and the fourth resistor are all in the second direction, and the first resistor, the second resistor, the third resistor and the fourth resistor all have the same conductivity type.

10. A method for manufacturing a pressure sensing structure, comprising: A semiconductor substrate is provided, having a first surface and a second surface on opposite sides; A groove is etched from the first surface of the semiconductor substrate; Forming a composite film within the groove, wherein forming the composite film includes: forming a semiconductor filling layer to fill the groove; forming an insulating layer to encapsulate the semiconductor filling layer; forming a semiconductor resistor on the composite film; etching a cavity from the second surface of the semiconductor substrate, wherein the etching of the cavity stops at the composite film, and the semiconductor resistor is located directly above the cavity; and providing a cover plate bonded to the semiconductor substrate to seal the cavity; wherein the top surface of the composite film and the first surface of the semiconductor substrate are on the same plane.

11. The method of manufacturing the pressure sensing structure as described in claim 10 further includes forming a transistor in the semiconductor substrate, wherein the semiconductor substrate includes a P-type silicon substrate.

12. A method for manufacturing the pressure sensing structure as described in claim 11, wherein the semiconductor resistor and a gate structure of the transistor are formed simultaneously by the same process steps.

13. The method of manufacturing the pressure sensing structure as described in claim 11 further includes: An interconnect layer is formed on top of the semiconductor substrate; And a pressure sensing opening is formed, penetrating the interconnect layer, wherein the pressure sensing opening is located directly above the semiconductor resistor.

14. A method of manufacturing a pressure sensing structure as described in claim 13, wherein the cavity is formed after the pressure sensing opening is formed.

15. A method of manufacturing a pressure sensing structure as described in claim 13, wherein, in the vertical projection direction, the boundary of the pressure sensing opening extends beyond the boundary of the cavity.

16. A method of manufacturing a pressure sensing structure as claimed in claim 10, wherein, in the vertical projection direction, the boundary of the cavity is within the boundary of the composite film.

17. A method of manufacturing a pressure sensing structure as described in claim 10, wherein forming the semiconductor resistor comprises: Simultaneously, a first resistor and a second resistor, each having a first conductivity type and separated along a first direction, are formed, with the major axes of the first resistor and the second resistor both in the first direction; and a third resistor and a fourth resistor, each having a second conductivity type and separated along a second direction, with the major axes of the third resistor and the fourth resistor both in the second direction, are also formed.

18. A method of manufacturing a pressure sensing structure as described in claim 10, wherein forming the semiconductor resistor comprises: Simultaneously, a first resistor, a second resistor, a third resistor, and a fourth resistor, each having the same conductivity type, are formed, wherein the first resistor and the second resistor are separated along a first direction, the third resistor and the fourth resistor are separated along a second direction, and the major axes of the first resistor, the second resistor, the third resistor, and the fourth resistor are all in the second direction.

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