Optical detection method and optical MEMS detector, and method for making MEMS detector

• US 8,368,005 B2
• Filed: 11/30/2009
• Issued: 02/05/2013
• Est. Priority Date: 11/30/2009
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Wang, Chuan-Wei, Hsu, Hsin-Hui, Lu, Chih-Hung
• Primary Examiner(s): Epps, Georgia Y
• Assistant Examiner(s): WILLIAMS, DON J
• Application Number:
  US12/627,374
• Publication Number:
  US 20110126623A1
• Time in Patent Office: 1,163 Days
• Field of Search: 250/216, 25023113-23118, 250/208.1, 250/221, 250/237.R, 250/237.G, 250/229, 356614-617
• US Class Current: 250/231.13
• CPC Class Codes: G01D 5/34 the beams of light being detected by photocells
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/093 by photoelectric pick-up

Abstract

The present invention discloses an optical MEMS detector, comprising: a substrate; at least one photo diode in a region within the substrate; an isolation wall above the substrate and surrounding the photo diode region; and at least one movable part having an opening for light to pass through and reach the photo diode, wherein when the at least one movable part is moved, an amount of light reaching the photo diode is changed.

Claims

1. An optical MEMS detector, comprising:

a substrate;

at least one photo diode in a region within the substrate;

an isolation wall above the substrate and surrounding the photo diode region; and

at least one movable part having an opening for light to pass through and reach the photo diode,

wherein when the optical MEMS detector is moved, the at least one movable part passively moves to generate a movement relative to the photo diode, thereby changing an amount of light reaching the photo diode such that a corresponding displacement of the optical MEMS detector is determined according to a difference of the amount of the light received by the photo diode.

2. The optical MEMS detector of claim 1, further comprising a light-transmissible layer made of a transparent material above the substrate.

3. The optical MEMS detector of claim 1, further comprising a light-transmissible layer made of a transparent material above the substrate, wherein the light-transmissible layer has a light passage over the photo diode.

4. The optical MEMS detector of claim 1, further comprising an optical device for guiding the light to enter the at least one opening of the movable part.

5. The optical MEMS detector of claim 1, further comprising a light source for providing a stable light.

6. The optical MEMS detector of claim 1, comprising multiple photo diode regions and multiple movable parts which are divided by multiple isolation walls, wherein at least one photo diode region and at least one movable part are both surrounded by at least a same one of the multiple isolation walls.

7. The optical MEMS detector of claim 6, wherein the size of at least one photo diode region is not the same as the size of another photo diode region.

8. The optical MEMS detector of claim 6, wherein at least one of the multiple isolation walls surrounds more than one photo diode regions.

9. The optical MEMS detector of claim 1, which is used for an accelerometer.

10. A method for making an optical MEMS detector, comprising the following steps:

providing a substrate;

forming at least one photo diode in a region within the substrate;

forming an isolation wall above the substrate, the isolation wall surrounding the photo diode region; and

forming at least one movable part above the photo diode, the at least one movable part having an opening for light to pass through and reach the photo diode, wherein when the optical MEMS detector is moved, the at least one movable part passively moves to generate a movement relative to the photo diode, thereby changing an amount of light reaching the photo diode such that a corresponding displacement of the optical MEMS detector is determined according to a difference of the amount of the light received by the photo diode.

11. The method of claim 10, wherein the step of forming the isolation wall includes:

depositing and patterning multiple non-transparent layers to form the isolation wall, the at least one movable part being formed when forming the isolation wall.

12. The method of claim 11, further comprising:

forming a light passage in the first light-transmissible layer by etching.

13. The method of claim 10, further comprising:

depositing a first light-transmissible layer made of a transparent material above the substrate; and

etching the first light-transmissible layer for a predetermined period of time, such that a portion of the first light-transmissible layer remains above the substrate.

14. The method of claim 13, further comprising:

forming a light passage in the first light-transmissible layer by etching.

15. The method of claim 10, further comprising:

depositing a first light-transmissible layer made of a transparent material above the substrate;

depositing an etch stop layer above the first light-transmissible layer;

depositing a second light-transmissible layer above the etch stop layer;

etching the second light-transmissible layer; and

etching the etch stop layer.

16. The method of claim 15, wherein the etch stop layer is made of a material including:

amorphous silicon or silicon nitride.

17. An optical detection method, comprising the following steps:

providing a detector including at least one photo diode and at least one movable part above the photo diode, the at least one movable part having an opening for light to pass through and reach the photo diode;

changing an amount of light passing through the opening and reaching the photo diode when the at least one movable part passively moves to generate a movement relative to the photo diode the photo diode as the detector is moved; and

determining whether the detector is moved and a corresponding displacement according to a difference of the amount of the light received by the photo diode.

18. The method of claim 17, further comprising:

providing a light source for the detector to receive a stable light.

19. The method of claim 17, further comprising:

moving the at least one movable part vertically, wherein when the at least one movable part is vertically moved toward the photo diode, it reduces the amount of the light received by the photo diode;

when the at least one movable part is vertically moved away from the photo diode, it increases the amount of the light received by the photo diode.

20. The method of claim 17, further comprising:

moving the at least one movable part horizontally, wherein when the at least one movable part covers a larger area of the photo diode, it reduces the amount of the light received by the photo diode.