Semiconductor pressure sensor

• US 4,813,272 A
• Filed: 07/31/1987
• Issued: 03/21/1989
• Est. Priority Date: 08/01/1986
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kobayashi, Ryoichi, Miyazaki, Atsushi
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US07/080,102
• Time in Patent Office: 599 Days
• Field of Search: 73/708, 73/720, 73/721, 73/726, 73/727, 73/729, 73/766, 73/DIG. 4, 338/4
• US Class Current: 73/708
• CPC Class Codes: G01L 9/0054 integral with a semiconducting diaphragm
• CPC Class Codes: G01L 9/065 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

There is a bridge circuit which is driven by a constant-current including a thermistor. The bridge circuit is constituted by strain gages defined by P-type diffused layers. Strain gages which constitute in combination the bridge circuit are defined by diffused resistor layers having a surface impurity concentration which is set so as to fall within the range from 2.3×10¹⁸ to 2.5×10¹⁸ atoms/cm³. The B constant of the thermistor is selected so as to fall within the range from 1400K to 2400K.

Claims

1. In a semiconductor pressure sensor including a silicon single crystal elastic substrate whose surface tension changes in accordance with the pressure applied thereto, a strain gage defined by a P-type diffused layer formed on the surface of said substrate, a bridge circuit including said strain gage, a constant-current circuit for supplying a driving current to said bridge circuit, and an amplifier circuit for amplifying an output from the output terminals of said bridge circuit to form an output signal,

the improvement comprising:

strain gages in said bridge circuit which are diffused resistor layers having a surface impurity concentration within the range from 2.3×

10¹⁸ to 2.5×

10¹⁸ atoms/cm³ ; and

thermistor means in said constant-current circuit, the thermistor means having a temperature-resistance characteristic for cancelling a temperature-resistance characteristic of said diffused resistor layers by selection of a B constant of the thermistor within the range from 1400K to 2400K, thereby effecting temperature compensation of sensitivity.