Capacitance type semiconductor dynamic quantity sensor

• US 20050061075A1
• Filed: 08/26/2004
• Published: 03/24/2005
• Est. Priority Date: 09/22/2003
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Sugiura, Makiko
• Granted Patent: US 7,275,435 B2
• Time in Patent Office: Days
• US Class Current: 73/514.320
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A capacitance type semiconductor dynamic quantity sensor includes a beam-shaped movable electrode displaceable in a predetermined direction in response to application of a dynamic quantity to a support substrate, and beam-shaped fixed electrodes which are fixedly supported on the support substrate and disposed so that the side surface thereof faces a side surface of the movable electrode. The applied dynamic quantity is detected on the basis of variation of electric capacitance between the side surface of the movable electrode and the side surface of the fixed electrodes. Countermeasures are included to prevent sticking between the fixed electrodes and the movable electrode.

Claims

1. A capacitance type semiconductor dynamic quantity sensor comprising:

a support substrate;

a beam-shaped movable electrode displaceable in a predetermined direction in response to application of a dynamic quantity to the support substrate; and

beam-shaped fixed electrodes fixedly supported on the support substrate and disposed so that the side surface thereof faces a side surface of the movable electrode,

wherein when the movable electrode is displaced in accordance with the application of the dynamic quantity, the applied dynamic quantity is detected on the basis of variation of electric capacitance between the side surface of the movable electrode and the side surface of the fixed electrodes,

wherein either the movable electrode or both of the fixed electrodes is a width-larger electrode and an other of the movable electrode or both of the fixed electrodes is a width-smaller electrode, the width-larger electrode having a larger width than that of the width-smaller electrode.

2. The capacitance type semiconductor dynamic quantity sensor according to claim 1, wherein the width-larger electrode out of the movable and fixed electrodes is preferably designed to be larger in width than the width-smaller electrode by 0.5 μ

m or more.

16. The capacitance type semiconductor dynamic quantity sensor according to claim 1, wherein a plurality of movable electrodes are disposed in a comb-shaped arrangement, and a plurality of fixed electrodes are disposed in a comb-shaped arrangement so as to be fitted in the gaps between the teeth of the comb-shaped arrangement of the movable electrodes.

3. A capacitance type semiconductor dynamic quantity sensor comprising:

a support substrate;

a beam-shaped movable electrode displaceable in response to application of a dynamic quantity to the support substrate; and

beam-shaped fixed electrodes fixedly supported on the support substrate so that side surfaces thereof face a side surface of the movable electrode, an applied dynamic quantity being detected on the basis of variation in electrostatic capacitance between the side surface of the movable electrode and the side surface of each of the fixed electrodes when the movable electrode is displaced in response to the application of the dynamic quantity, wherein;

the side surface of either the movable electrode or both of the fixed electrodes is equipped with adherence preventing projecting portions projecting from the side surface concerned at sites where the side surfaces of the movable and fixed electrodes face each other so that the projecting portions are arranged along a longitudinal direction of the movable and fixed electrodes; and

when L represents the length of the movable and fixed electrodes at the sites where the side surfaces of the movable and fixed electrodes face each other, La represents the distance between neighboring projecting portions in the arrangement of the projecting portions, σ

2(x) represents a sagging amount, W represents the width of the electrodes, h represents the thickness of the electrodes, d2 represents the height of the projecting portions, V represents the voltage applied between the movable electrode and the fixed electrode, and Fe(x) represents the electrostatic force applied between the electrodes,

σ

2(x)=[Fe(x)·

La³]/(48·

E·

I)]×

(⅝

)
I=W³h/12
Fe(x)=ε

0·

V²/(2·

d2²)·

h·

L

La/L, W, d2 are determined so that the sagging amount σ

2(x) is less than the half of the height d2 of the projecting portions (σ

2(x)<

d2/2).

4. The capacitance type semiconductor dynamic quantity sensor according to claim 3, wherein the ratio of the distance La to the length L (La/L) is set in the range from 0.1 to 0.9.

5. The capacitance type semiconductor dynamic quantity sensor according to claim 3, wherein the projecting portions are equipped to the side surfaces of both the movable and fixed electrodes at sites where the side surfaces of the movable and fixed electrodes face each other.

6. The capacitance type semiconductor dynamic quantity sensor according to claim 3, wherein either the movable electrode or both of the fixed electrodes is a width-larger electrode and an other of the movable electrode or both of the fixed electrodes is a width-smaller electrode, wherein the width-larger electrode has a larger width than that of the width-smaller electrode

7. The capacitance type semiconductor dynamic quantity sensor according to claim 6, wherein the width-larger electrode out of the movable and fixed electrodes is preferably set to be larger in width than the width-smaller electrode by 0.5 μ

m or more.

8. The capacitance type semiconductor dynamic quantity sensor according to claim 3, wherein when the length L is set to 500 μ

m or less and the width of the movable and fixed electrodes is set to 2 μ

m, the ratio La/L is set in the range from 0.1 to 0.5.

9. The capacitance type semiconductor dynamic quantity sensor according to claim 3, wherein when the length L is set to 500 μ

m or less and the width of the movable and fixed electrodes is set to 3 μ

m, the ratio La/L is set in the range from 0.1 to 0.7.

10. The capacitance type semiconductor dynamic quantity sensor according to claim 3, wherein when the length L is set to 500 μ

m or less and the width of the movable and fixed electrodes is set to 4 μ

m, the ratio La/L may be set in the range from 0.1 to 0.9.

14. The capacitance type semiconductor dynamic quantity sensor according to claim 3, wherein a plurality of movable electrodes are disposed in a comb-shaped arrangement, and a plurality of fixed electrodes are disposed in a comb-shaped arrangement so as to be fitted in the gaps between the teeth of the comb-shaped arrangement of the movable electrodes.

11. A capacitance type semiconductor dynamic quantity sensor comprising:

a support substrate;

a beam-shaped movable electrode displaceable in response to application of a dynamic quantity to the support substrate; and

beam-shaped fixed electrodes fixedly supported on the support substrate so that side surfaces thereof face a side surface of the movable electrode, an applied dynamic quantity being detected on the basis of variation in electrostatic capacitance between the side surface of the movable electrode and the side surface of each of the fixed electrodes when the movable electrode is displaced in response to the application of the dynamic quantity,

wherein either the movable electrode or both of the fixed electrodes is a width-larger electrode and an other of the movable electrode or both of the fixed electrodes is a width-smaller electrode, the width-larger electrode having a larger width than that of the width-smaller electrode,

wherein the side surface of at least one of the movable and fixed electrodes is equipped with adherence preventing projecting portions projecting from the side surface concerned at sites where the side surfaces of the movable and fixed electrodes face each other so that the projecting portions are arranged along a longitudinal direction of the movable and fixed electrodes,

wherein when L represents the length of the movable and fixed electrodes at the sites where the side surfaces of the movable and fixed electrodes face each other, La represents the distance between neighboring projecting portions in the arrangement of the projecting portions, σ

2(x) represents a sagging amount, W represents the width of the electrodes, h represents the thickness of the electrodes, d2 represents the height of the projecting portions, V represents the voltage applied between the movable electrode and the fixed electrode, and Fe(x) represents the electrostatic force applied between the electrodes,

σ

2(x)=[Fe(x)·

La³]/(48·

E·

I)]×

(⅝

)
I=W³·

h/12
Fe(x)=ε

0·

V²/(2·

d2²)·

h·

L

La/L, W, d2 are determined so that the sagging amount σ

2(x) is less than the half of the height d2 of the projecting portions (σ

2(x)<

d2/2).

12. The capacitance type semiconductor dynamic quantity sensor according to claim 11, the ratio of the distance La to the length L (La/L) is set in the range from 0.1 to 0.9.

13. The capacitance type semiconductor dynamic quantity sensor according to claim 11, wherein a plurality of movable electrodes are disposed in a comb-shaped arrangement, and a plurality of fixed electrodes are disposed in a comb-shaped arrangement so as to be fitted in the gaps between the teeth of the comb-shaped arrangement of the movable electrodes.

15. A capacitance type semiconductor dynamic quantity sensor comprising:

a support substrate;

a beam-shaped movable electrode displaceable in response to application of a dynamic quantity to the support substrate; and

beam-shaped fixed electrodes fixedly supported on the support substrate so that side surfaces thereof face the side surface of the movable electrode, an applied dynamic quantity being detected on the basis of variation in electrostatic capacitance between a side surface of the movable electrode and the side surface of each of the fixed electrodes when the movable electrode is displaced in response to the application of the dynamic quantity,

wherein the side surface of at least one of the movable electrode and fixed electrodes is equipped with adherence preventing projecting portions projecting from the side surface concerned at sites where the side surfaces of the movable electrode and fixed electrodes face each other so that the projecting portions are arranged along a longitudinal direction of the movable electrode and fixed electrodes,

wherein when L represents the length of the movable electrode and fixed electrodes at the sites where the side surfaces of the movable electrode and fixed electrodes face each other and La represents the distance between neighboring projecting portions in the arrangement of the projecting portions, the ratio of the distance La to the length L (La/L) is set in the range from 0.1 to 0.9.