MEMS and method for forming the same

• US 10,023,459 B2
• Filed: 04/11/2013
• Issued: 07/17/2018
• Est. Priority Date: 03/11/2013
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Chang, Kuei-Sung, Wu, Ting-Hau
• Primary Examiner(s): Miyoshi, Jesse Y
• Assistant Examiner(s): Hoang, Tuan A
• Application Number:
  US13/860,759
• Publication Number:
  US 20150353342A1
• Time in Patent Office: 1,923 Days
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: B81B 3/0013 Structures dimensioned for mechanical prevention of stiction, e.g. spring with increased stiffness
• CPC Class Codes: B81B 3/0016 Arrangements for avoiding sticking of the flexible or moving parts not provided for in groups B81B3/0005 - B81B3/0013
• CPC Class Codes: B81C 1/00134 comprising flexible or deformable structures manufacture of MEMS devices for specific applications, see relevant places, e.g. gyroscopes G01C19/5719, pressure sensors G01L9/0042, accelerometers G01P15/0802, acoustic transducers or diaphragms therefor H04R31/00
• CPC Class Codes: B81C 1/00142 Bridges deformable micromirrors G02B26/0841
• CPC Class Codes: B81C 1/0015 Cantilevers switches using MEMS H01H1/0036; electrostatic relays using micromechanics H01H59/0009; microelectro-mechanical resonators H03H9/02244
• CPC Class Codes: B81C 1/0019 Flexible or deformable structures not provided for in groups B81C1/00142 - B81C1/00182
• CPC Class Codes: B81C 1/00468 Releasing structures
• CPC Class Codes: B81C 1/00484 Processes for releasing structures not provided for in group B81C1/00476
• CPC Class Codes: B81C 1/00936 Releasing the movable structure without liquid etchant
• CPC Class Codes: B81C 1/0096 For avoiding stiction when the device is in use, i.e. after manufacture has been completed
• CPC Class Codes: H01L 2924/1461 MEMS

Abstract

A method and apparatus are provided to prevent or reduce stiction of a MEMS device. The MEMS device may include a protrusion extending from a surface of the MEMS device. During manufacture, the protrusion may be connected across an opening in the MEMS device to a sidewall of the substrate. Before manufacture of the MEMS device is completed, at least a portion of the protrusion connecting the MEMS device to the substrate may be removed. During operation, the protrusion may provide stiction prevention or reduction for the surface from which the first protrusion may extend. A plurality of protrusions may be formed along a plurality of surfaces for the MEMS device to prevent or reduce stiction along the corresponding surfaces. Protrusions may also be formed on devices surrounding or encapsulating the MEMS device to prevent or reduce stiction of the MEMS device to the surrounding or encapsulating devices.

Claims

1. A method comprising:

forming a MEMS device in a first substrate, the first substrate having a first surface and a second surface opposing the first surface, the first surface of the first substrate having a recess, the MEMS device being formed in the recess, the MEMS device having a first surface, the first surface of the MEMS device extending in a direction that is parallel to the first surface of the first substrate, the first surface of the MEMS device being between the first surface of the first substrate and the second surface of the first substrate;

forming a trench in the second surface of the first substrate, the trench having a first sidewall and a second sidewall opposing the first sidewall, wherein a region of the first substrate at a bottom of the trench and extending from the first sidewall of the trench to the second sidewall of the trench forms a first protrusion, wherein a first thickness of the first protrusion, measured along a first direction perpendicular to the first surface of the MEMS device, is different from a second thickness of the MEMS device measured along the first direction;

bonding the first substrate to a second substrate, the first surface of the first substrate being interposed between the second surface of the first substrate and the second substrate; and

after bonding the first substrate to the second substrate, extending the trench through the first substrate to remove at least a portion of the first protrusion, wherein after removing the at least the portion of the first protrusion, the first protrusion comprises a sidewall that is connected to a sidewall of the MEMS device, wherein the sidewall of the first protrusion and the sidewall of the MEMS device are made of a same material, wherein a sidewall of the first substrate exposed by the trench extends along a straight line from the first surface of the first substrate to the second surface of the first substrate.

2. The method of claim 1, further comprising:

forming a second protrusion on the second substrate, wherein the second protrusion is opposite to and separated from the first surface of the MEMS device.

3. The method of claim 1, further comprising:

forming a second protrusion to extend from the first surface of the MEMS device across an opening to connect to another sidewall of the first substrate adjacent to the MEMS device.

4. The method of claim 3, wherein the second protrusion is opposite to and separated from the second substrate.

5. The method of claim 3, further comprising:

removing at least a portion of the second protrusion connected to the first substrate following the bonding the first substrate to the second substrate.

6. The method of claim 1, further comprising:

forming a second protrusion to extend from a second surface of the MEMS device.

7. The method of claim 1, further comprising bonding a third substrate to the first substrate following the bonding the first substrate to the second substrate.

8. The method of claim 7, further comprising:

before bonding the third substrate to the first substrate, forming a second protrusion to extend from a second surface of the MEMS device, wherein, after bonding the third substrate to the first substrate, the second surface of the MEMS device is opposite to the third substrate.

9. The method according to claim 1, wherein a sidewall of the recess is laterally disposed between a first opening of the MEMS device and the first sidewall of the trench, the first opening extending from the second surface of the first substrate to the first surface of the MEMS device.

10. The method according to claim 1, wherein after the trench is formed, the bottom of the trench is planar with the first surface of the MEMS device.

11. A method comprising:

forming a MEMS device in a first substrate, the MEMS device having a first surface, a second surface and a third surface, wherein the first surface and the third surface are parallel;

forming a first protrusion to extend from the second surface of the MEMS device, a portion of the first protrusion connecting the MEMS device to a sidewall of the first substrate, where the first protrusion has a first thickness different from a second thickness of the MEMS device, wherein the first thickness and the second thickness are measured along a direction perpendicular to the first surface of the MEMS device;

forming a second protrusion to extend from the first surface of the MEMS device;

bonding the first substrate to a second substrate;

removing the portion of the first protrusion connecting the MEMS device to the first substrate following the bonding the first substrate to the second substrate, the removing allowing the MEMS device to move, wherein after the portion of the first protrusion is removed the first protrusion comprises a top surface and a bottom surface, the top surface and the bottom surface each extending in a direction that is parallel to the first surface, the top surface and the bottom surface extending along an opening adjacent to the MEMS device, and the top surface and the bottom surface being made of a same material; and

bonding a third substrate to the first substrate, the third substrate having a fourth surface opposite the third surface of the MEMS device.

12. The method of claim 11, further comprising:

forming a third protrusion on the second substrate, wherein the third protrusion is separated from the second surface of the MEMS device.

13. The method of claim 11, further comprising:

forming a third protrusion to extend from a fifth surface of the MEMS device, a portion of the third protrusion connecting the MEMS device to another sidewall of the first substrate; and

removing the portion of the third protrusion connecting the MEMS device to the first substrate following the bonding the first substrate to the second substrate, the removing allowing the MEMS device to move.

14. The method of claim 11, further comprising:

forming a third protrusion to extend from the third surface of the MEMS device prior to the bonding the third substrate to the first substrate.

15. The method of claim 11, wherein the first protrusion and the first substrate comprise a same material.

16. The method of claim 11, wherein the first surface of the MEMS device is between the third surface of the MEMS device and a lower side of the first substrate facing the second substrate, wherein an upper side of the first substrate is level with the third surface of the MEMS device, wherein the sidewall of the first substrate is straight and extends from the upper side of the first substrate to the lower side of the first substrate.

17. An apparatus comprising:

a first substrate having formed therein a MEMS device, the MEMS device having a first surface, a second surface and a third surface, the third surface being level with a major surface of the first substrate and the second surface being parallel to another major surface of the first substrate;

a first protrusion extending from the first surface of the MEMS device, the first protrusion having a portion extending into an opening adjacent to the MEMS device, wherein a sidewall of the first substrate that is opposite to the first protrusion across the opening in the MEMS device extends in a straight line from the major surface of the first substrate to the another major surface of the first substrate, the sidewall of the first substrate being made of a same material between the major surface and the another major surface, wherein a thickness of the first protrusion, measured along a first direction parallel to the sidewall of the first substrate, is smaller than a thickness of the MEMS device measured along the first direction, and wherein the opening extends from the major surface to the another major surface of the first substrate;

a second substrate bonded to the first substrate, the second substrate having a fourth surface opposite the second surface of the MEMS device; and

a second protrusion extending from the fourth surface of the second substrate, the second protrusion having a fifth surface, wherein the fifth surface of the second protrusion is smaller than the second surface of the MEMS device.

18. The apparatus of claim 17, wherein the second protrusion is separated from the second surface of the MEMS device.

19. The apparatus of claim 17, further comprising:

a third protrusion extending from a sixth surface of the MEMS device, the third protrusion having a seventh surface, wherein the seventh surface of the third protrusion is smaller than the sixth surface of the MEMS device.

20. The apparatus of claim 17, wherein a lower side of the first protrusion is level with the second surface of the MEMS device.