Semiconductor mechanical sensor and method of manufacture

• US 6,227,050 B1
• Filed: 10/28/1998
• Issued: 05/08/2001
• Est. Priority Date: 08/21/1992
• Status: Expired due to Term

• Current Assignee: DENSO Corporation
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Fujii, Tetsuo, Imai, Masahito
• Primary Examiner(s): Kwok, Helen C.
• Application Number:
  US09/181,615
• Time in Patent Office: 923 Days
• Field of Search: 73/504.15, 73/514.32, 73/514.16, 73/504.12, 73/504.13, 73/504.14, 361/307, 361/283.3, 361/321.1, 361/321.5, 361/283.1
• 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 sensor comprising:

a supporting substrate;

a beam structure of semiconductive material having a geometry that a thickness thereof is greater than a width thereof;

a vibrating member to vibrate said beam structure with respect to a surface of said supporting substrate; and

a detecting electrode portion to detect a displacement of said beam structure according to a mechanical force acting upon said beam structure in a perpendicular direction along a vibration of said beam structure by said vibrating member.

2. A semiconductor mechanical sensor device, wherein a plurality of semiconductor mechanical sensors as defined by claim 1 are arranged monolithically.

3. A semiconductor mechanical sensor according to claim 1, wherein said supporting substrate comprises monocrystalline silicon.

4. A semiconductor mechanical sensor according to claim 1, wherein said beam structure comprises a first portion forming a pair of first capacitive electrodes in association with said vibrating member, a second portion forming a pair of second capacitive electrodes in association with said detecting electrode portion, a fixed portion fixing said beam structure to said supporting substrate and a support portion intermediately supporting said first and second portions to said fixed portion.

5. A semiconductor mechanical sensor according to claim 1, wherein said vibrating member includes a vibration electrode which is disposed between said supporting substrate and said beam structure to be spaced from said beam structure.

6. A semiconductor mechanical sensor according to claim 5, wherein said vibration electrode is stationary disposed on said supporting substrate with an insulating layer interposed therebetween.

7. A semiconductor mechanical sensor according to claim 6, wherein said vibration electrode comprises a doped polycrystalline silicon.

8. A semiconductor mechanical sensor according to claim 5, wherein said vibrating member includes a vertical portion connected to said vibration electrode for electrically conducting between said vibration electrode and an external part.

9. A semiconductor mechanical sensor according to claim 8, wherein said vertical portion comprises monocrystalline silicon and is isolated from said supporting substrate by means of an insulating layer.

10. A semiconductor mechanical sensor according to claim 4, wherein a comb-teeth-like structure is so formed on said beam structure that each tooth of said comb-teeth-like structure functions as said second portion of said beam structure, and corresponding detecting electrode portions are stationary provided over said supporting substrate, thereby plural pairs of said second capacitive electrodes are integrated on said beam structure.

11. A semiconductor mechanical sensor according to claim 1, wherein said detecting electrode portion comprises a detection electrode which is isolated from said supporting substrate by means of an insulating layer.

12. A semiconductor mechanical sensor according to claim 11, wherein said detecting electrode portion comprises monocrystalline silicon and said detection electrode comprises a high impurity concentration region.

13. A semiconductor mechanical sensor according to claim 4, wherein said fixed portion is fixed to said supporting substrate through an insulating layer.

14. A semiconductor mechanical sensor according to claim 13, wherein said first and second portions, said support portion and said fixed portion comprise monocrystalline silicon.

15. A semiconductor mechanical sensor according to claim 1, wherein said beam structure comprises monocrystalline silicon, and is isolated from said supporting substrate by means of an insulating layer.

16. A semiconductor mechanical sensor according to claim 15, wherein said beam structure has a high impurity concentrating region disposed to encompass sidewalls and bottom of said beam structure.

17. A semiconductor mechanical sensor according to claim 16, wherein said high impurity concentration region of said beam structure is covered with an insulation film.

18. A semiconductor mechanical sensor comprising:

a layer of a silicon material which is used as a conductive material;

a substrate provided on the lower side of said layer and electrically insulated from the layer;

said layer including;

a beam structure having a first weight portion forming a first capacitive electrode for first displacement in a parallel direction to a surface of said substrate, a second weight portion forming a second capacitive electrode for second displacement in a perpendicular direction to said first displacement, a fixed portion for fixing said beam structure to said substrate and a support portion for intermediately supporting said first and second weight portions to said fixed portion,

an insulating groove extending through a thickness of said layer around the entire periphery of said beam structure, and

a first stationary block capacitively coupling with said first capacitive electrode, said first stationary block being defined by said insulating groove on the outer side of said beam structure to face said first weight portion separately across said insulating groove and being fixed to said substrate; and

gap means forming a gap space in order to space said first and second weight portions and said support portion from a surface of said second substrate,

said substrate being separated from said layer by an insulating layer which is at least provided on the lower side of said fixed portion and said first stationary block.

19. A semiconductor mechanical sensor according to claim 18, wherein a width of said support portion is smaller than a thickness of said fixed portion.

20. A semiconductor mechanical sensor according to claim 18, wherein said layer is formed of a n-type silicon material.

21. A semiconductor mechanical sensor according to claim 18, wherein said substrate is formed of a silicon material having a surface covered with an insulating oxidation film.

22. A semiconductor mechanical sensor according to claim 18, further comprising a driving electrode member facing said second weight portion for producing an electrostatic force for said beam structure and causing said second displacement of said beam structure.

23. A semiconductor mechanical sensor according to claim 22, wherein said driving electrode member is provided on a lower side of said second weight portion of said beam structure.

24. A semiconductor mechanical sensor according to claim 23, wherein said insulating layer is further provided on the lower side of said driving electrode member.

25. A semiconductor mechanical sensor according to claim 23, wherein said layer further includes a second stationary block electrically connected to said driving electrode member, said second stationary block being defined by said insulating groove on the outer side of said beam structure separately across said insulating groove and being fixed to said substrate, and wherein said insulating layer is further provided on the lower side of said second stationary block.

26. A semiconductor mechanical sensor according to claim 18, wherein said beam structure has a high impurity concentration region disposed to encompass sidewalls and bottom of said beam structure.

27. A semiconductor mechanical sensor according to claim 26, wherein said high impurity concentration region of said beam structure is covered with an insulation film.

28. A semiconductor mechanical sensor comprising:

a supporting substrate;

a beam structure which includes a first weight portion forming a first capacitive electrode on a side surface of said first weight portion, a fixed portion for fixing said beam structure to said supporting substrate and a thin support portion for intermediately connecting between said first weight portion and said fixed portion;

a first stationary block arranged on a side of said beam structure to face said first capacitive electrode separately across an air gap, and fixed to said supporting substrate;

gap means for forming a gap space in order to space said first weight portion and said thin support portion from a surface of said supporting substrate, whereby said first weight portion may be displaced in a parallel direction to the surface of said supporting substrate according to the degree of mechanical force applied thereon;

an electrode line conveying an electrical signal for said semiconductor mechanical sensor, and provided on a lower side of said beam structure; and

a second stationary block electrically connected to said electrode line, said second stationary block being fixed to said supporting substrate to be arranged on a outer side of said beam structure and isolated from said first stationary block,

said beam structure and said first and second stationary blocks being formed of a silicon material which is used as a conductive material and electrically insulated from said supporting substrate.

29. A semiconductor mechanical sensor according to claim 28, wherein said electrode line is provided with a signal for producing an electrostatic force for said beam structure and causing a vibration of said beam structure.

30. A semiconductor mechanical sensor according to claim 28, wherein said beam structure has a high impurity concentration region disposed to encompass sidewalls and bottom of said beam structure.

31. A semiconductor mechanical sensor according to claim 30, wherein said high impurity concentration region of said beam structure is covered with an insulation film.