Semiconductor pressure sensor and pressure sensing device

• US 6,892,582 B1
• Filed: 08/20/1999
• Issued: 05/17/2005
• Est. Priority Date: 08/20/1999
• Status: Expired due to Fees

• Current Assignee: Hitachi Car Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Original Assignee: Hitachi Car Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Inventors: Onose, Yasuo, Momma, Naohiro, Satou, Shinya, Miyazaki, Atsushi, Horie, Junichi, Watanabe, Atsuo, Shimada, Satoshi, Kuryu, Seiji
• Primary Examiner(s): Hirshfeld, Andrew H.
• Assistant Examiner(s): FERGUSON SAMRETH, MARISSA LIANA
• Application Number:
  US09/936,480
• Time in Patent Office: 2,097 Days
• Field of Search: 737/16, 737/20, 737/21, 737/54, 737/15, 737/17, 737/23, 737/77, 257/254, 257/417, 361/283.1, 361/283.4
• US Class Current: 73/715
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81C 1/00293 maintaining a controlled atmosphere with processes not provided for in B81C1/00285
• CPC Class Codes: B81C 1/00333 Aspects relating to packaging of MEMS devices, not covered by groups B81C1/00269 - B81C1/00325
• CPC Class Codes: B81C 2203/0145 Hermetically sealing an opening in the lid
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm

Abstract

The object of the present invention is to propose an etch channel sealing structure characterized by excellent impermeability to moisture and resistance to temporal change of the diaphragm in the pressure sensor produced according to the sacrificial layer etching technique, and to provide a pressure sensor characterized by excellent productivity and durability. After a very small gap is formed by the sacrificial layer etching technique, silicon oxide film is deposited by the CVD technique or the like, thereby sealing the etch channel. Further, impermeable thin film of polysilicon or the like is formed to cover the oxide film.

This allows an etch channel sealing structure to be simplified in the pressure sensor produced according to the sacrificial layer etching technique, and prevents entry of moisture into the cavity, thereby improving moisture resistance. Moreover, sealing material with small film stress reduces temporal deformation of the diaphragm.

Claims

1. A semiconductor pressure sensor, comprising:

a substrate;

a diaphragm arranged on said substrate, the diaphragm comprising an etch channel;

a silicon oxide film covering said diaphragm and sealing said etch channel; and

a polysilicon film with a first side covering part or all of said silicon oxide film and a second side exposed to an environment of the pressure sensor.

2. A semiconductor pressure sensor according to claim 1, wherein a distance of said covered part is at least 10 microns or less from said etch channel.

3. A semiconductor pressure sensor according to claim 1, wherein a thickness of said polysilicon film is 0.1 microns or more.

4. A semiconductor pressure sensor according to claim 1, wherein a thickness of said polysilicon film is 0.1 microns or more up to and including 0.4 microns.

5. A pressure detector, comprising:

(a) a detector providing an output, the detector including as an integral unit;

a substrate,

a diaphragm arranged on said substrate, the diaphragm comprising an etch channel;

a silicon oxide film covering said diaphragm and sealing said etch channel, and

a polysilicon film with a first side covering part or all of said silicon oxide film and a second side exposed to an environment of the pressure sensor;

(b) a correction circuit for correction of the output of said detector;

(c) a package enclosing said correction circuit and said detector; and

(d) an intake tube provided in said package, the intake tube being used for introducing external pressure to said detector.

6. A pressure detector according to claim 5, wherein a distance (h) of said covering part is at least 10 microns or less from said etch channel.

7. A pressure detector according to claim 5, wherein a thickness (i) of said polysilicon film is 0.1 microns or more.

8. A pressure detector according to claim 5, wherein a thickness (j) of said polysilicon film is 0.1 microns or more up to and including 0.4 microns.

9. A pressure detector according to claim 5 comprising:

(e) a sub-package further comprising said correction circuit and said detector as an integral unit, and having on a surface a pad connected to said correction circuit; and

(f) an output terminal removably connected to an external signal line and being used to send a signal from said correction circuit to the external signal line;

wherein said correction circuit and said detector are enclosed by said package after said pad and said output terminal are connected by a metal wire.

10. A semiconductor pressure sensor, comprising:

a substrate;

a diaphragm arranged on the substrate, a gap between the diaphragm and the substrate being formed by sacrificial layer etching using etch channels arranged about a periphery of the diaphragm;

a silicon oxide film arranged over the diaphragm in order to seal the etch channels; and

a polysilicon film covering at least a substantial portion of the silicon oxide film.

11. A semiconductor pressure sensor according to claim 10, wherein the polysilicon film has a first side covering at least a substantial portion of the oxide film and a second side exposed to an environment of the pressure sensor.

12. A semiconductor pressure sensor according to claim 11, wherein the pressure sensor is an electrostatic capacity or piezoresistive pressure sensor.