Micro electro mechanical system

• US 9,500,666 B2
• Filed: 02/26/2014
• Issued: 11/22/2016
• Est. Priority Date: 08/18/2008
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Degawa, Munenori, Jeong, Heewon
• Primary Examiner(s): Kwok, Helen
• Application Number:
  US14/190,968
• Publication Number:
  US 20140174181A1
• Time in Patent Office: 1,000 Days
• Field of Search: 735/143.2, 735/041.2, 735/041.4
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/025 Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242
• CPC Class Codes: B81B 2203/0109 Bridges
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5733 Structural details or topology
• CPC Class Codes: G01P 1/003 used for damping
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/0802 Details
• 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

In order to provide a technology capable of suppressing degradation of measurement accuracy due to fluctuation of detection sensitivity of an MEMS by suppressing fluctuation in natural frequency of the MEMS caused by a stress, first, fixed portions 3a to 3d are displaced outward in a y-direction of a semiconductor substrate 2 by deformation of the semiconductor substrate 2. Since a movable body 5 is disposed in a state of floating above the semiconductor substrate 2, it is not affected and displaced by the deformation of the semiconductor substrate 2. Therefore, a tensile stress (+σ₁) occurs in the beam 4a and a compressive stress (−σ₂) occurs in the beam 4b. At this time, in terms of a spring system made by combining the beam 4a and the beam 4b, increase in spring constant due to the tensile stress acting on the beam 4a and decrease in spring constant due to the compressive stress acting on the beam 4b are offset against each other.

Claims

1. A micro electro mechanical system, comprising:

a sensor element, comprising;

a first spring system including a first fixed portion and a first elastically-deformable beam connected to the first fixed portion and extending therefrom in a first direction,

a second spring system including a second fixed portion and a second elastically-deformable beam connected to the second fixed portion and extending therefrom in a second direction opposite to the first direction,

a third spring system including a third fixed portion and a third elastically-deformable beam connected to the third fixed portion and extending therefrom in a third direction,

a fourth spring system including a fourth fixed portion and a fourth elastically-deformable beam connected to the fourth fixed portion and extending therefrom in a fourth direction opposite to the third direction, and

a movable body, movable in a moving direction, suspended from the first fixed portion via the first beam, suspended from the second fixed portion via the second beam, suspended from the third fixed portion via the third beam, and suspended from the fourth fixed portion via the fourth beam,

wherein the first and second spring systems are arranged on one side of a virtual line extending in the moving direction through a center of the sensor element, the third and fourth spring systems are arranged on the other side of the virtual line, and, when the movable body is displaced in the moving direction, tensile stresses are generated within the first, second, third and fourth spring systems at the same time.

2. The micro electro mechanical system according to claim 1,

wherein the first and the second fixed portions are the same, and

wherein the third and the fourth fixed portions are the same.

3. The micro electro mechanical system according to claim 1,

wherein the first beam suspends the movable body via a first turning portion,

wherein the second beam suspends the movable body via a second turning portion,

wherein the third beam suspends the movable body via a third turning portion, and

wherein the fourth beam suspends the movable body via a fourth turning portion.

4. The micro electro mechanical system according to claim 3,

wherein a distance between the first and the second fixed portions is smaller than a distance between the first and the second turning portions, and

wherein a distance between the third and the fourth fixed portions is smaller than a distance between the third and the fourth turning portions.

5. The micro electro mechanical system according to claim 1,

wherein the first beam is in alignment with the second beam, and

wherein the third beam is in alignment with the fourth beam.

6. The micro electro mechanical system according to claim 1,

wherein the first and the second spring systems are symmetric with respect to the virtual line, and

wherein the third and the fourth spring system are symmetric with respect to the virtual line.

7. The micro electro mechanical system according to claim 1,

wherein each of the first, second, third and fourth beams include a number of beams.

8. The micro electro mechanical system according to claim 7,

wherein the number of first beams is the same as the number of second beams, and

wherein the number of third beams is the same as the number of fourth beams.

9. The micro electro mechanical system according to claim 1,

wherein the first, second, third and fourth fixed portions, the first, second, third and fourth beams, and the movable body are arranged on a first semiconductor chip, and

wherein the first semiconductor chip is mounted on an underlayer substrate via an adhesive agent.

10. The micro electro mechanical system according to claim 9,

wherein the underlayer substrate is a second semiconductor chip on which an integrated circuit is formed.

11. The micro electro mechanical system according to claim 1,

wherein the sensor element is an angular velocity sensor.

12. The micro electro mechanical system according to claim 2,

wherein the first, second, third and fourth fixed portions are fixed to a semiconductor substrate that is deformable in a direction perpendicular to the moving direction, and

wherein the center of the sensor element is located at a stress inflection point along the direction perpendicular to the moving direction.

13. The micro electro mechanical system according to claim 12,

wherein the stress inflection point is a zero stress point.

14. The micro electro mechanical system according to claim 1,

wherein the first, second, third and fourth elastically-deformable beams are arranged perpendicular to the moving direction.