MEMS pressure sensing device

• US 7,373,833 B2
• Filed: 08/09/2006
• Issued: 05/20/2008
• Est. Priority Date: 10/29/2004
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: McGinty, James, Hopper, Peter J., Drury, Robert, Mian, Michael
• Primary Examiner(s): Allen; Andre J.
• Application Number:
  US11/501,318
• Publication Number:
  US 20060278009A1
• Time in Patent Office: 650 Days
• Field of Search: 737/18, 737/24, 737/53, 737/54
• US Class Current: 73/718
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 2207/015 the micromechanical device and the control or processing electronics being integrated on the same substrate
• CPC Class Codes: B81C 1/00246 Monolithic integration, i.e. micromechanical structure and electronic processing unit are integrated on the same substrate
• CPC Class Codes: B81C 2201/019 Bonding or gluing multiple substrate layers
• CPC Class Codes: B81C 2203/0735 Post-CMOS, i.e. forming the micromechanical structure after the CMOS circuit
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm

Abstract

A pressure sensing system formed in a monolithic semiconductor substrate. The pressure sensing system comprises a pressure sensing device formed on the monolithic semiconductor substrate. The pressure sensing device is adapted to be disposed in an environment for developing an electrical pressure signal corresponding to the pressure in the environment. The system includes driver circuitry formed in the monolithic semiconductor substrate. The driver circuitry is responsive to input electrical signal for generating an output pressure signal. A conductive interconnect structure formed in the monolithic semiconductor substrate to electrically connects the pressure sensing device to the driver circuitry such that electrical pressure signals developed by the pressure sensing device are provided as input electrical signals to the driver circuitry.

Claims

1. A pressure sensing system formed in a monolithic semiconductor substrate, the pressure sensing system comprising:

(a) driver circuitry formed in the monolithic semiconductor substrate, the driver circuitry being responsive to input electrical signals for generating an output pressure signal;

(b) a capacitive pressure sensing device formed on the semiconductor substrate, the capacitive pressure sensing device including

(i) a conductive lower capacitor plate formed at an upper surface of the semiconductor substrate;

(ii) a conductive pad formed at the upper surface of the semiconductor substrate and spaced-apart from the lower capacitor plate;

(iii) patterned dielectric material formed over the upper surface of the semiconductor substrate and having a first opening formed therein to expose an upper surface of the conductive pad and having a second opening formed therein over the lower capacitor plate;

(iv) a supporting layer of dielectric material formed on the patterned dielectric material, the supporting layer having a first opening formed therein over the conductive pad and having a plurality of openings formed therein over the second opening in the patterned dielectric material; and

(v) an upper layer of conductive material formed on the supporting layer and extending through the first opening in the supporting layer and into the first opening in the patterned dielectric material to form electrical contact with the exposed upper surface of the conductive pad, the upper layer of conductive material extending over the plurality of openings formed in the supporting layer to close said openings to define an enclosed cavity between the lower capacitor plate and the upper conductive layer; and

(c) a conductive interconnect structure formed in the monolithic semiconductor substrate, the conductive interconnect structure being connected between the capacitive pressure sensing device and the driver circuitry for providing electrical pressure signals developed by the capacitive pressure sensing device as input electrical signals to the driver circuitry.

2. A pressure sensing system as in claim 1, and wherein

the supporting layer comprises silicon nitride;

and

the upper layer of conductive material comprises a metal.

3. A pressure sensing system as in claim 2, and wherein the metal comprises aluminum.

4. A pressure sensing system as in claim 1, and wherein the semiconductor substrate comprises crystalline silicon.

5. A pressure sensing system as in claim 4, and wherein the patterned dielectric material comprises:

a silicon nitride layer having an opening formed therein to expose the upper surface of the conductive pad and that extends over the lower capacitor plate; and

a silicon oxide layer formed on the silicon nitride layer and having a first opening formed therein to expose the upper surface of the conductive pad and a second opening formed therein over the lower capacitor plate.

6. A method of forming a pressure sensing system on a semiconductor substrate, the method comprising;

(a) forming a capacitive pressure sensing device in the monolithic semiconductor substrate, the capacitive pressure sensing device being adapted to be disposed in an environment for developing an electrical pressure signal corresponding to the pressure in the environment, the capacitive pressure sensing device including

(i) a conductive lower capacitor plate formed at an upper surface of the semiconductor substrate;

(ii) a conductive pad formed at the upper surface of the semiconductor substrate and spaced-apart from the lower capacitor plate;

(iii) dielectric material formed over the upper surface of the semiconductor substrate, the lower capacitor plate and the conductive pad, the dielectric material being patterned to have a first opening formed therein to expose an upper surface of the conductive pad and to have a second opening formed therein over the lower capacitor plate;

(iv) a supporting layer of dielectric material formed on the patterned dielectric material, the supporting layer having a first opening formed therein over the conductive pad and having a plurality of openings formed therein over the second opening in the patterned dielectric material; and

(v) an upper layer of conductive material formed on the supporting layer and extending through the first opening in the supporting layer and into the first opening in the patterned dielectric material to form electrical contact with the exposed upper surface of the conductive pad, the upper layer of conductive material extending over the plurality of openings in the supporting layer to close said openings to define an enclosed cavity between the lower capacitor plate and the upper conductive layer;

(b) forming driver circuitry in the monolithic semiconductor substrate, the driver circuitry being responsive to input electrical signals for generating an output pressure signal; and

(c) forming a conductive interconnect structure in the monolithic semiconductor substrate, the conductive interconnect structure being connected between the capacitive pressure sensing device and the driver circuitry for providing electrical pressure signals developed by the pressure sensing device as input electrical signals to the driver circuitry.

7. A method as in claim 6, and wherein the upper layer of conductive material comprises aluminum.

8. A method as in claim 6, and wherein the semiconductor substrate comprises crystalline silicon.

9. A method as in claim 6, and wherein the patterned dielectric material comprises:

a silicon nitride layer formed over the upper surface of the semiconductor substrate, the conductive pad and the lower capacitor plate;

an opening formed in the silicon nitride layer to expose the upper surface of the conductive pad; and

a silicon oxide layer formed over the silicon nitride layer, the silicon oxide layer being patterned to form a first opening therein to expose the upper surface of the conductive pad and to form a second opening therein over the lower capacitor plate.