Semiconductor mechanical sensor

• US 7,866,210 B2
• Filed: 03/11/2009
• Issued: 01/11/2011
• Est. Priority Date: 08/21/1992
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Imai, Masahito, Fujii, Tetsuo
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US12/381,356
• Publication Number:
  US 20090179288A1
• Time in Patent Office: 671 Days
• Field of Search: 7350412-50415, 735/040.4, 735/143.2, 735/142.9, 735/141.6, 257415-419, 438 50- 52
• US Class Current: 73/514.32
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 7/0006 Interconnects
• CPC Class Codes: C07C 303/32 of salts of sulfonic acids
• CPC Class Codes: C07C 303/44 Separation; Purification
• CPC Class Codes: C07C 309/17 containing carboxyl groups bound to the carbon skeleton
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5656 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0817 for pivoting movement of the mass, e.g. in-plane pendulum
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/49004 including measuring or testing of device or component part

Abstract

A semiconductor mechanical sensor having a new structure in which a S/N ratio is improved. In the central portion of a silicon substrate 1, a recess portion 2 is formed which includes a beam structure. A weight is formed at the tip of the beam, and in the bottom surface of the weight in the bottom surface of the recess portion 2 facing the same, an electrode 5 is formed. An alternating current electric power is applied between the weight portion 4 and the electrode 5 so that static electricity is created and the weight is excited by the static electricity. In an axial direction which is perpendicular to the direction of the excitation of the weight, an electrode 6 is disposed to face one surface of the weight and a wall surface of the substrate which faces the same. A change in a capacitance between the facing electrodes is electrically detected, and therefore, a change in a physical force acting in the same direction is detected.

Claims

1. A semiconductor mechanical quantity sensor comprising:

a silicon substrate having an insulation layer on a first surface;

a silicon layer formed on the silicon substrate;

a weight disposed on the silicon layer and movable in a predetermined direction parallel with the first surface of the silicon substrate due to an effect of a mechanical quantity, said weight being provided with a plurality of movable electrodes which are in parallel with each other, each of said plurality of movable electrodes being provided with a surface perpendicular to the first surface of the silicon substrate;

a plurality of fixed electrodes secured to the insulation layer and being opposed to the surfaces of the plurality of movable electrodes to form capacitors with the plurality of movable electrodes; and

a peripheral portion surrounding the plurality of movable electrodes and the plurality of fixed electrodes, wherein

major surfaces of the plurality of movable electrodes, the plurality of fixed electrodes, and the peripheral portion being formed to be substantially on the same plane with each other,

the plurality of movable electrodes, the plurality of fixed electrodes, and the peripheral portion being insulated and separated from one another to detect the mechanical quantity based on a change of the capacitance of the capacitors,

all electrode contacting portions being formed on a major surface of the silicon layer.

2. A semiconductor mechanical quantity sensor as set forth in claim 1, further comprising a wiring layer for electrically interconnecting the plurality of fixed electrodes.

3. A semiconductor mechanical quantity sensor as set forth in claim 1, wherein each of said plurality of movable electrodes has a surface and a back surface as the other surface, the sensor comprising:

a plurality of first fixed electrodes which are secured to the insulation layer and which are opposed to one surface of the plurality of movable electrodes to form a first capacitor together with the plurality of movable electrodes; and

a plurality of second fixed electrodes which are secured to the insulation layer and which are opposed to the other surface of the plurality of movable electrodes to from a second capacitor together with the plurality of movable electrodes, where a direction of a change in the capacitance of the second capacitor caused by movement of the plurality of movable electrodes is opposite to that of the first capacitor, so that the mechanical quantity is detected based on the change in the capacitance of the first and second capacitors.

4. A semiconductor mechanical quantity sensor as set forth in claim 3, further comprising a first wiring layer for electrically interconnecting the plurality of first fixed electrodes and a second wiring layer for electrically interconnecting the plurality of second fixed electrodes.

5. A semiconductor mechanical quantity sensor having a first layer comprising a silicon substrate, a second layer comprising an insulation layer disposed on the first layer, a third layer comprising a silicon layer disposed on the second layer, a fourth layer comprising an insulation film partially disposed on the third layer, and a fifth layer comprising a silicon layer disposed on the fourth layer and partly connected to the third layer through a portion where the fourth layer is not disposed, wherein the sensor comprises:

a plurality of movable electrodes formed by the fifth layer, and arranged in parallel with each other, said plurality of movable electrodes being movable in a predetermined direction parallel with a surface of the first layer due to an effect of a mechanical quantity; and

a plurality of fixed electrodes formed by the fifth layer and secured to the first layer through at least the second layer, said fixed electrodes being opposed to the surfaces of the plurality of movable electrodes to form capacitors together with the plurality of movable electrodes, so that the mechanical quantity is detected based on a change in the capacitance of the capacitors.

7. A semiconductor mechanical quantity sensor as set forth in claim 5, wherein each of said plurality of movable electrodes has a surface and a back surface as the other surface, and the sensor comprising:

a plurality of first fixed electrodes which are secured to the insulation layer and which are opposed to one surface of the movable electrodes to form a first capacitor together with the movable electrodes; and

a plurality of second fixed electrodes which are secured to the insulation layer and which are opposed to the other surface of the movable electrodes to form a second capacitor together with the plurality of movable electrodes, where the direction of a change in the capacitance of the second capacitor caused by the movement of the plurality of movable electrodes is opposite to that of the first capacitor, so that the mechanical quantity is detected based on the change in the capacitance of the first and second capacitors.

8. A semiconductor mechanical quantity sensor as set forth in claim 7, further comprising a first wiring layer for electrically interconnecting the plurality of first fixed electrodes and a second wiring layer for electrically interconnecting the plurality of second fixed electrodes.

6. A semiconductor mechanical quantity sensor as set forth in clam 5, further comprising a wiring layer for electrically interconnecting the plurality of fixed electrodes.

9. A semiconductor mechanical quantity sensor having a first layer comprising a silicon substrate, a second layer comprising an insulation layer disposed on the first layer, a third layer comprising a silicon layer disposed on the second layer, a fourth layer comprising an insulation layer disposed on the third layer, and a fifth layer comprising a silicon layer disposed on the fourth layer, wherein

said fifth layer is provided with a weight movable due to an effect of a mechanical quantity, a plurality of movable electrodes formed on the weight, and a plurality of fixed electrodes opposed to the plurality of movable electrode,

said third layer is made of a polysilicon layer containing high density impurities, which is formed in parallel with the first layer and under the weight,

a predetermined area of the fifth layer is electrically connected to the polysilicon layer through a bottom contact for an electric connection, formed on a predetermined area of the polysilicon layer and a major surface of said fifth layer is provided with electrode contacting portions made of at least one metal layer and arranged on substantially the same plane with each other.

10. A semiconductor mechanical quantity sensor as set forth in claim 9, further comprising a wiring layer for electrically interconnecting the plurality of fixed electrodes.

11. A semiconductor mechanical quantity sensor as set forth in claim 9, wherein each of said plurality of movable electrodes has a surface and a back surface as the other surface, the sensor comprising:

a plurality of first fixed electrodes which are opposed to one surface of the plurality of movable electrodes to form a first capacitor together with the plurality of movable electrodes; and

a plurality of second fixed electrodes which are opposed to the other surface of the plurality of movable electrodes to form a second capacitor together with the plurality of movable electrodes, where a direction of a change in the capacitance of the second capacitor caused by movement of the plurality of movable electrodes is opposite to that of the first capacitor, so that the mechanical quantity is detected based on the change in the capacitance of the first and second capacitors.

12. A semiconductor mechanical quantity sensor as set forth in claim 11, further comprising a first wiring layer for electrically interconnecting the plurality of first fixed electrodes and a second wiring layer for electrically interconnecting the plurality of second fixed electrodes.