Quasi-differential capacitive MEMS pressure sensor and manufacturing methods thereof

• US 10,295,422 B2
• Filed: 12/10/2015
• Issued: 05/21/2019
• Est. Priority Date: 05/29/2015
• Status: Active Grant

• Current Assignee: Weifang Goertek Microelectronics Co., Ltd. (Goertek Incorporated)
• Original Assignee: Goertek Incorporated
• Inventors: Zheng, Guoguang
• Primary Examiner(s): Villaluna, Erika J
• Application Number:
  US15/559,311
• Publication Number:
  US 20180113040A1
• Time in Patent Office: 1,258 Days
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 19/0618 Overload protection
• CPC Class Codes: G01L 9/0045 Diaphragm associated with a buried cavity
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/12 by making use of variations in capacitance , i.e. electric circuits therefor

Abstract

The present invention discloses a quasi-differential capacitive MEMS pressure sensor and manufacturing methods thereof. The quasi-differential capacitive MEMS pressure sensor includes a first lower electrode, a second lower electrode, a first upper electrode supported above the first lower electrode, and a second upper electrode supported above the second lower electrode, wherein the first upper electrode is a pressure-sensitive film, and a cavity between the first upper electrode and the first lower electrode is a closed cavity, so that the first upper electrode and the first lower electrode constitute an air pressure-sensitive type capacitor; and the second upper electrode and the second lower electrode constitute a reference capacitor whose capacitance does not vary with external air pressure. The pressure sensor provided by the present invention can at least partially filter out a common-mode interference signal in an output signal of the air pressure-sensitive type capacitor by use of the reference capacitor, thereby improving the stability and resolution of the output signal of the air pressure-sensitive type capacitor.

Claims

1. A quasi-differential capacitive MEMS pressure sensor, comprising:

a substrate, an insulating layer formed on the substrate, a first lower electrode and a second lower electrode respectively formed on the insulating layer, a first upper electrode supported above the first lower electrode, and a second upper electrode supported above the second lower electrode, wherein the first upper electrode is a pressure-sensitive film, a cavity between the first upper electrode and the first lower electrode is a closed cavity, so that the first upper electrode and the first lower electrode constitute an air pressure-sensitive type capacitor, the air pressure-sensitive type capacitor further comprising an anti-collision projection formed on the first lower electrode and/or an anti-collision projection formed on the insulating layer and penetrating through the first lower electrode to protrude upward, wherein there is a gap between the anti-collision projection and the first upper electrode; and

the second upper electrode and the second lower electrode constitute a reference capacitor whose capacitance does not vary with external air pressure.

2. The quasi-differential capacitive MEMS pressure sensor of claim 1, wherein the closed cavity is a vacuum cavity.

3. The quasi-differential capacitive MEMS pressure sensor of claim 1, wherein the second upper electrode is also a pressure-sensitive film;

and the reference capacitor further comprises a limiting structure for restricting deformation of the second upper electrode under the action of the external air pressure.

4. The quasi-differential capacitive MEMS pressure sensor of claim 3, wherein the first upper electrode and the second upper electrode form an integrated structure.

5. The quasi-differential capacitive MEMS pressure sensor of claim 3, wherein the reference capacitor is provided with a supporting post for supporting the second upper electrode to form the limiting structure.

6. The quasi-differential capacitive MEMS pressure sensor of claim 3, wherein the reference capacitor is provided with a pressure-balancing hole through which a cavity between the second upper electrode and the second lower electrode of the reference capacitor communicates with the outside so as to form the limiting structure.

7. The quasi-differential capacitive MEMS pressure sensor of claim 3, wherein the air pressure-sensitive type capacitor has the same structure as the reference capacitor, except for the limiting structure.

8. A manufacturing method of a quasi-differential capacitive MEMS pressure sensor, the method comprising the following steps:

a), depositing a first oxide layer as an insulating layer on a substrate;

b), depositing and etching a first metal layer on the insulating layer to form a first lower electrode and a second lower electrode independent of each other;

c) depositing and etching a second oxide layer on the first lower electrode and the second lower electrode to form a supporting part and a supporting post corresponding to the second lower electrode; and

d), bonding a pressure-sensitive film on the supporting part and the supporting post to form a closed cavity between the pressure-sensitive film and the first lower electrode to enable the pressure-sensitive film, which acts as a first upper electrode, and the first lower electrode to constitute an air pressure-sensitive type capacitor, and to form a second upper electrode supported by the supporting post, to enable the second upper electrode and the second lower electrode to constitute a reference capacitor whose capacitance does not vary with external air pressure.

9. A manufacturing method of a quasi-differential capacitive MEMS pressure sensor, the method comprising the following steps:

a), depositing a first oxide layer as an insulating layer on a substrate;

b), depositing and etching a first metal layer on the insulating layer to form a first lower electrode and a second lower electrode independent of each other;

c) depositing and etching a second oxide layer on the first lower electrode and the second lower electrode to form a supporting part;

d), bonding a pressure-sensitive film on the supporting part to form a closed cavity between the pressure-sensitive film and the first lower electrode to enable the pressure-sensitive film, which acts as a first upper electrode, and the first lower electrode to constitute an air pressure-sensitive type capacitor, and to form another closed cavity between the pressure-sensitive film and the second lower electrode; and

e) etching the pressure-sensitive film to enable the another closed cavity to become a cavity communicating with the outside, enabling the pressure-sensitive film, which acts as a second upper electrode, and the second lower electrode to constitute a reference capacitor whose capacitance does not vary with external air pressure.