MEMS accelerometer with enhanced structural strength

• US 20120042729A1
• Filed: 11/10/2010
• Published: 02/23/2012
• Est. Priority Date: 08/17/2010
• Status: Active Grant

• Current Assignee: Pixart Imaging Incorporation ROC
• Original Assignee: Pixart Imaging Incorporation ROC
• Inventors: Wang, Chuan-Wei
• Granted Patent: US 8,459,115 B2
• Time in Patent Office: Days
• US Class Current: 73/514.32
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/082 for two degrees of freedom of movement of a single mass
• CPC Class Codes: G01P 2015/0837 the mass being suspended so as to only allow movement perpendicular to the plane of the substrate, i.e. z-axis sensor
• CPC Class Codes: G01P 2015/0854 using a particular shape of the mass, e.g. annular
• CPC Class Codes: G01P 2015/0857 using a particular shape of the suspension spring

Abstract

The present invention discloses a MEMS (Micro-Electro-Mechanical System, MEMS) accelerator with enhanced structural strength. The MEMS accelerator is located on a substrate, and it includes: multiple springs, wherein each spring includes: an anchor, fixed on the substrate; an extensible part, which has a fixed end fixed on the anchor, and a free end floating above the substrate; a proof mass, connected to the free ends of the springs; and multiple in-plane sense electrodes, wherein the extensible part is folded back and forth to form a substantially polygon shape as a whole, in which the fixed end is located within the middle one third length of one side of the substantially polygon shape, and the free end is located within the middle one third length of an opposite side of the substantially polygon shape.

Claims

1. A MEMS accelerometer with enhanced structural strength, comprising:

multiple springs wherein each spring includes;

a spring anchor fixed on a substrate; and

an extensible part having;

a fixed end fixed to the spring anchor; and

a free end floating above the substrate;

wherein the extensible part is folded back and forth to form a substantially polygon shape as a whole, in which the fixed end is not located around a corner of the substantially polygon shape, and the free end is located within an opposite side of the substantially polygon shape and neither around a corner;

a proof mass having multiple joints connected to corresponding free ends of the multiple springs respectively; and

multiple in-plane sense electrodes wherein each in-plane sense electrode includes;

at least one stator fixed on the substrate, having;

a stator anchor fixed on the substrate;

multiple stator metal layers fixed to the stator anchor; and

at least one stator connection plug for connecting adjacent layers of the stator metal layers; and

at least one rotor connected to the proof mass, having;

multiple rotor metal layers connected to the proof mass; and

at least one rotor connection plug for connecting adjacent layers of the rotor metal layers.

2. The MEMS accelerometer of claim 1, wherein the fixed end is located within the middle one third length of one side of the substantially polygon shape, and the free end is located within the middle one third length of an opposite side of the substantially polygon shape.

3. The MEMS accelerometer of claim 1, wherein each spring further includes a stabilizing sector connecting the free end to the proof mass, the stabilizing sector being located on the same side with the free end and wider than the free end.

4. The MEMS accelerometer of claim 1, wherein a top one, a bottom one, or both top and bottom ones of the stator metal layers include multiple metal sectors which are not connected to one another at the same level but are connected to an adjacent stator metal layer by the at least one stator connection plug.

5. The MEMS accelerometer of claim 1, wherein a top one, a bottom one, or both top and bottom ones of the rotor metal layers include multiple metal sectors which are not connected to one another at the same level but are connected to an adjacent rotor metal layer by the at least one rotor connection plug.

6. The MEMS accelerometer of claim 1, wherein the rotor includes a relatively wider enhancement beam and a relatively narrower electrode, for enhancing the structural strength of the rotor.

7. The MEMS accelerometer of claim 6, wherein the enhancement beam includes an “

I”

shape, an “

II”

shape, or a cross shape from top view.

8. The MEMS accelerometer of claim 1, further comprising an out-of-plane sense electrode, wherein the out-of-plane sense electrode includes:

a Z-axis stator fixed on the substrate; and

at least one Z-axis rotor connected to the proof mass, and each Z-axis rotor having;

multiple Z-axis rotor metal layers connected to the proof mass; and

at least one Z-axis rotor connection plug for connecting adjacent layers of the Z-axis rotor metal layers.

9. The MEMS accelerometer of claim 8, wherein a top one, a bottom one, or both top and bottom ones of the Z-axis rotor metal layers include multiple metal sectors which are not connected to one another at the same level but are connected to an adjacent Z-axis rotor metal layer by the at least one Z-axis rotor connection plug.

10. The MEMS accelerometer of claim 8, wherein the Z-axis rotor includes extended metal sectors perpendicular to each other from top view.

11. The MEMS accelerometer of claim 1, wherein the stator has a substantially linear shape from top view, and the stator anchor is located at an end nearer to the proof mass.

12. A MEMS accelerometer with enhanced structural strength, comprising:

multiple springs wherein each spring includes;

a spring anchor fixed on a substrate; and

an extensible part having;

a fixed end fixed to the spring anchor; and

a free end floating above the substrate;

a proof mass having multiple joints connected to corresponding free ends of the multiple springs respectively; and

multiple in-plane sense electrodes wherein each in-plane sense electrode includes;

at least one stator fixed on the substrate, having;

a stator anchor fixed on the substrate;

multiple stator metal layers fixed to the stator anchor; and

at least one stator connection plug for connecting adjacent layers of the stator metal layers; and

at least one rotor connected to the proof mass, having;

multiple rotor metal layers connected to the proof mass; and

at least one rotor connection plug for connecting adjacent layers of the rotor metal layers;

wherein a top one, a bottom one, or both top and bottom ones of the rotor metal layers include multiple metal sectors which are not connected to one another at the same level but are connected to an adjacent rotor metal layer by the at least one rotor connection plug.

13. The MEMS accelerometer of claim 12, wherein a top one, a bottom one, or both top and bottom ones of the stator metal layers include multiple metal sectors which are not connected to one another at the same level but are connected to an adjacent stator metal layer by the at least one stator connection plug.

14. The MEMS accelerometer of claim 12, wherein the rotor includes a relatively wider enhancement beam and a relatively narrower electrode, for enhancing the structural strength of the rotor.

15. The MEMS accelerometer of claim 14, wherein the enhancement beam includes an “

I”

shape, an “

II”

shape, or a cross shape from top view.

16. The MEMS accelerometer of claim 12, further comprising an out-of-plane sense electrode, wherein the out-of-plane sense electrode includes:

a Z-axis stator fixed on the substrate; and

at least one Z-axis rotor connected to the proof mass, and each Z-axis rotor having;

multiple Z-axis rotor metal layers connected to the proof mass; and

at least one Z-axis rotor connection plug for connecting adjacent layers of the Z-axis rotor metal layers.

17. The MEMS accelerometer of claim 16, wherein a top one, a bottom one, or both top and bottom ones of the Z-axis rotor metal layers include multiple metal sectors which are not connected to one another at the same level but are connected to an adjacent Z-axis rotor metal layer by the at least one Z-axis rotor connection plug.

18. The MEMS accelerometer of claim 16, wherein the Z-axis rotor includes extended metal sectors perpendicular to each other from top view.

19. The MEMS accelerometer of claim 12, wherein the stator has a substantially linear shape from top view, and the stator anchor is located at an end nearer to the proof mass.

20. A MEMS accelerometer with enhanced structural strength, comprising:

multiple springs wherein each spring includes;

a spring anchor fixed on a substrate; and

an extensible part having;

a fixed end fixed to the spring anchor; and

a free end floating above the substrate;

a proof mass having multiple joints connected to corresponding free ends of the multiple springs respectively; and

multiple in-plane sense electrodes wherein each in-plane sense electrode includes;

at least one stator fixed on the substrate, having;

an stator anchor fixed on the substrate;

multiple stator metal layers fixed to the stator anchor; and

at least one stator connection plug for connecting adjacent layers of the stator metal layers; and

at least one rotor connected to the proof mass, having;

multiple rotor metal layers connected to the proof mass; and

at least one rotor connection plug for connecting adjacent layers of the rotor metal layers;

wherein a top one, a bottom one, or both top and bottom ones of the stator metal layers include multiple metal sectors which are not connected to one another at the same level but are connected to an adjacent stator metal layer by the at least one stator connection plug.

21. The MEMS accelerometer of claim 20, wherein the rotor includes a relatively wider enhancement beam and a relatively narrower electrode, for enhancing the structural strength of the rotor.

22. The MEMS accelerometer of claim 21, wherein the enhancement beam includes an “

I”

shape, an “

II”

shape, or a cross shape from top view.

23. The MEMS accelerometer of claim 20, further comprising an out-of-plane sense electrode, wherein the out-of-plane sense electrode includes:

a Z-axis stator fixed on the substrate; and

at least one Z-axis rotor connected to the proof mass, and each Z-axis rotor having;

multiple Z-axis rotor metal layers connected to the proof mass; and

at least one Z-axis rotor connection plug for connecting adjacent layers of the Z-axis rotor metal layers.

24. The MEMS accelerometer of claim 23, wherein a top one, a bottom one, or both top and bottom ones of the Z-axis rotor metal layers include multiple metal sectors which are not connected to one another at the same level but are connected to an adjacent Z-axis rotor metal layer by the at least one Z-axis rotor connection plug.

25. The MEMS accelerometer of claim 23, wherein the Z-axis rotor includes extended metal sectors perpendicular to each other from top view.

26. The MEMS accelerometer of claim 20, wherein the stator has a substantially linear shape from top view, and the stator anchor is located at an end nearer to the proof mass.