Semiconductor dynamic quantity sensor

• US 20050263838A1
• Filed: 05/26/2005
• Published: 12/01/2005
• Est. Priority Date: 06/01/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Sakai, Minekazu
• Granted Patent: US 7,622,781 B2
• Time in Patent Office: Days
• US Class Current: 257/417
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

When movable electrodes of beam arrangement structures are displaced in a direction perpendicular to the surface of a support substrate in first and second capacitance constituent portions by action of an acceleration while carrier voltages are applied, the difference between a first capacitance and second capacitance is output from the support substrate through a third capacitance constituent portion. Under self-diagnosis, the voltage applying counter electrode portion of the self-diagnosis fixed capacitance constituent portion is set to a first potential, and a signal output counter electrode portion of the third capacitance constituent portion is set to a second potential different from the first potential, whereby the potential of the support substrate corresponding to the fixed electrode in the first and second capacitance constituent portions is forcedly changed.

Claims

1. A semiconductor dynamic quantity sensor comprising:

a first capacitance constituent portion having a laminate substrate including a thin film semiconductor layer disposed through insulating film on a support substrate formed of a semiconductor material, a first beam arrangement structure sectionally formed in the thin film semiconductor layer, and a first movable electrode portion of the first beam arrangement structure disposed so as to confront the support substrate through a first cavity, the first movable electrode portion being displaced in a direction perpendicular to the surface of the support substrate under action of a dynamic quantity while a first carrier voltage is applied to the first movable electrode portion to thereby vary a first capacitance between the movable electrode portion and the support substrate;

a second capacitance constituent portion that is formed on the laminate substrate in the form of a one-chip with the first capacitance constituent portion, and has a second beam arrangement structure sectionally formed in the thin film semiconductor layer, and a second movable electrode portion of the second beam arrangement structure disposed so as to confront the support substrate through a second cavity, the second movable electrode portion being displaced in a direction perpendicular to the surface of the support substrate under action of the dynamic quantity while a second carrier voltage is applied to the second movable electrode portion, whereby a second capacitance between the second movable electrode portion and the support substrate being varied in a variation state different from the variation state of the first capacitance based on the displacement of the first movable electrode portion of the first beam arrangement structure, and a differential capacitance between the first capacitance and the second capacitance being output to the support substrate;

a third capacitance constituent portion that is formed on the laminate substrate in the form of a one-chip with the first and second capacitance constituent portions, and has a signal output counter electrode sectionally formed in the thin film semiconductor layer while the insulating film exists below the signal output counter electrode portion, the differential capacitance being output by the signal output counter electrode portion;

a C-V conversion circuit for converting to a voltage signal the differential capacitance output by the signal output counter electrode portion of the third capacitance constituent portion; and

a self-diagnosis fixed capacitance constituent portion that is formed on the laminate substrate in the form of a one-chip with the first, second and third capacitance constituent portions, has a voltage applying counter electrode portion sectionally formed in the thin film semiconductor layer while the insulating film exists below the voltage applying counter electrode portion and forcedly changes the potential of the support substrate, wherein the voltage applying counter electrode portion of the self-diagnosis fixed capacitance constituent portion under self-diagnosis is set to a first potential, and the signal output counter electrode portion of the third capacitance constituent portion is set to a second potential different from the first potential to forcedly change the potential of the support substrate serving as a fixed electrode of the first and second capacitance constituent portions, whereby the first and second movable electrodes of the first and second capacitance constituent portions are displaced by electrostatic force.

2. The semiconductor dynamic quantity sensor according to claim 1, wherein with respect to the voltage applying counter electrode portion of the self-diagnosis fixed capacitance constituent portion and the signal output counter electrode portion of the third capacitance constituent portion, the potential of the voltage applying counter electrode portion of the self-diagnosis fixed capacitance constituent portion under self-diagnosis is varied from that under dynamic quantity detection.

3. The semiconductor dynamic quantity sensor according to claim 1, wherein with respect to the voltage applying counter electrode portion of the self-diagnosis fixed capacitance constituent portion and the signal output counter electrode portion of the third capacitance constituent portion, the potential of the signal output counter electrode portion of the third capacitance constituent portion under self-diagnosis is varied from that under dynamic quantity detection.

5. The semiconductor dynamic quantity sensor according to claim 1, wherein the voltage of the voltage applying counter electrode portion of the self-diagnosis fixed capacitance constituent portion is changed to a predetermined potential during a self-diagnosis state by applying the predetermined potential to the C-V conversion circuit.

7. The semiconductor dynamic quantity sensor according to claim 1, wherein the potential of the substrate is changed by applying the first or second potential to the C-V conversion circuit and fixing a potential of the voltage applying counter electrode portion to ground potential.

6. A semiconductor dynamic quantity sensor comprising:

a plurality of movable electrodes disposed over a substrate, wherein the movable electrodes move in a direction orthogonal to a surface of the substrate in response to an applied dynamic quantity;

a plurality of fixed electrodes disposed on the substrate, wherein a differential capacitance is induced between the movable electrodes and the fixed electrodes in accordance with the movement of the movable electrodes responsive to the applied dynamic quantity;

a signal output electrode disposed on the substrate, wherein the signal output electrode outputs the differential capacitance to a CV conversion circuit; and

wherein the voltage applying counter electrode portion disposed on the substrate, wherein the potential of the voltage applying counter electrode portion is set to a first potential, and the signal output electrode is set to a second potential different from the first potential to forcedly change the potential of the substrate, which serves as the fixed electrodes, and perform a self-diagnosis operation and permit self-diagnosis.