Apparatus for measuring a mechanical quantity

• US 7,707,894 B2
• Filed: 09/15/2008
• Issued: 05/04/2010
• Est. Priority Date: 06/17/2004
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ohta, Hiroyuki, Sumigawa, Takashi
• Primary Examiner(s): Caputo; Lisa M
• Assistant Examiner(s): ROY, PUNAM P
• Application Number:
  US12/210,261
• Publication Number:
  US 20090007686A1
• Time in Patent Office: 596 Days
• Field of Search: 737/27, 737/77, 438/48, 338/5, 338/6
• US Class Current: 73/777
• CPC Class Codes: G01B 7/16 for measuring the deformation in a solid, e.g. by resistance strain gauge
• CPC Class Codes: G01B 7/18 using change in resistance
• CPC Class Codes: G01B 7/20 formed by printed-circuit technique
• CPC Class Codes: G01L 1/2206 Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
• CPC Class Codes: G01L 1/2262 involving simple electrical bridges
• CPC Class Codes: G01L 5/0047 measuring forces due to residual stresses

Abstract

An apparatus structure and measurement method are provided to retain high precision and high reliability of a semiconductor mechanical quantity measuring apparatus which senses a mechanical quantity and transmits measured information wirelessly. As to a silicon substrate of the semiconductor mechanical quantity measuring apparatus, for example, a ratio of a substrate thickness to a substrate length along a measurement direction is set small, and a ratio of a substrate thickness to a substrate length along a direction perpendicular to the measurement direction is set small. The apparatus upper surface is covered with a protective member. It is possible to measure a strain along a particular direction and realize mechanical quantity measurement with less error and high precision. An impact resistance and environment resistance of the apparatus itself can be improved.

Claims

1. A mechanical quantity measuring apparatus having a strain detector formed on a single crystal semiconductor substrate for detecting a strain, and bonded to or buried in an object to be measured to measure a strain, wherein:

a Wheatstone bridge circuit having a pair of sensor resistor layers and a pair of dummy resistors disposed on a principal surface of said single crystal semiconductor substrate, a resistance of each dummy resistor being equal to a resistance of one of the sensor resistor layers and each sensor resistor layer including a P-type impurity diffusion layer whose longitudinal direction is set to a <

110>

crystal plane direction of the single crystal silicon semiconductor substrate; and

a plurality of second resistor layers not constituting said Wheatstone bridge circuit formed along a longitudinal direction of each of the sensor resistor layers and each of the dummy resistors, wherein said second resistor layers have no electrical connection to each other,

wherein, for each sensor resistor layer, a pair of second resistor layers is formed on opposite sides thereof.

2. The mechanical quantity measuring apparatus according to claim 1, wherein said plurality of second resistor layers not constituting said Wheatstone bridge circuit have almost a same shape as a shape of said strain sensor resistor layer.