Pressure sensor and manufacturing method thereof

• US 6,860,154 B2
• Filed: 01/14/2002
• Issued: 03/01/2005
• Est. Priority Date: 01/16/2001
• Status: Expired due to Fees

• Current Assignee: Fujikura Limited
• Original Assignee: Fujikura Limited
• Inventors: Sato, Masahiro, Nishimura, Hitoshi, Yamamoto, Satoshi, Nakao, Osamu
• Primary Examiner(s): Hirshfeld, Andrew H.
• Assistant Examiner(s): FERGUSON SAMRETH, MARISSA LIANA
• Application Number:
  US10/047,627
• Publication Number:
  US 20020092356A1
• Time in Patent Office: 1,142 Days
• Field of Search: 737/15, 737/18, 73724-727, 738/620.43, 737/54, 738/62, 361/503, 361/523, 3612831-2834, 438/53, 438/504, 216/2, 296/21, 156/357, 156/662
• US Class Current: 73/718
• CPC Class Codes: G01L 1/148 using semiconductive material, e.g. silicon
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm

Abstract

It is an object of the present invention to provide a touch mode capacitive pressure sensor having higher pressure durability than conventional sensors. In this invention, a touch mode capacitive pressure sensor has a diaphragm made from boron-doped silicon, and the boron concentration at the top face of the diaphragm is equal to or greater than 1×10¹⁹ cm⁻³ and less than 9×10¹⁹ cm⁻³. Further, in this invention, a touch mode capacitive pressure sensor has a conductive diaphragm made by doping of an impurity and anisotropic etching, and the etch pit density on the top face of the diaphragm is equal to or less than five per μm², and preferably equal to or less than one per μm². As a result, the pressure durability of the diaphragm is greatly improved.

Claims

1. A pressure sensor comprising a silicon structure having a conductive diaphragm, the silicon structure being bonded on a substrate, which comprises an electrode covered by a dielectric film, so that the diaphragm and the electrode are facing each other and there is a gap between the diaphragm and the dielectric film, the pressure sensor measuring a pressure applied thereto by detecting capacitance according to the area of a contact face of the diaphragm which touches the dielectric film when the pressure is applied;

the concentration of an impurity at the top face of the diaphragm being equal to or greater than 1×

10¹⁹ cm<sup>−

3</sup> and less than 9×

10¹⁹ cm<sup>−

3</sup>.

3. The pressure sensor of claim 1, wherein the impurity is boron.

2. A pressure sensor comprising a silicon structure having a conductive diaphragm, provided by doping of an impurity and anisotropic etching, the silicon structure being bonded on a substrate, which comprises an electrode covered by a dielectric film, so that the diaphragm and the electrode are facing each other and there is a gap between the diaphragm and the dielectric film, the pressure sensor measuring a pressure applied thereto by detecting capacitance according to the area of a contact face of the diaphragm which touches the dielectric film when the pressure is applied;

the etch pit density on the top face of the diaphragm being equal to or less than five per μ

m².

4. The pressure sensor of claim 2, wherein in etch pit density on the top face of the diaphragm is equal to or less than three pits per μ

m².

5. The pressure sensor of claim 2, wherein in etch pit density on the top face of the diaphragm is equal to or less than one pit per μ

m².

6. The pressure sensor of claim 2, wherein the impurity is boron.