Imager method and apparatus employing photonic crystals

• US 7,688,378 B2
• Filed: 06/07/2005
• Issued: 03/30/2010
• Est. Priority Date: 06/07/2005
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Mouli, Chandra
• Primary Examiner(s): Ye; Lin
• Assistant Examiner(s): HOGUE, DENNIS A
• Application Number:
  US11/146,090
• Publication Number:
  US 20060274189A1
• Time in Patent Office: 1,757 Days
• Field of Search: 348/340, 348/362, 348/207.99, 348/296, 359/278, 359/230, 428/457, 438/52, 257/680
• US Class Current: 348/342
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 1/005 made of photonic crystals or photonic band gap materials photonic band-gap structures or photonic lattices in integrated optics G02B6/1225; photonic band-gap structures or photonic lattices in optical fibres G02B6/02295
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14623 Optical shielding
• CPC Class Codes: H01L 27/14645 Colour imagers
• CPC Class Codes: H01L 27/14649 Infrared imagers
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H01L 27/148 Charge coupled imagers individual charge coupled devices H01L29/765
• CPC Class Codes: H01L 31/02162 for filtering or shielding light, e.g. multicolour filters for photodetectors
• CPC Class Codes: H01L 31/02165 using interference filters, e.g. multilayer dielectric filters interference filters G02B5/28
• CPC Class Codes: Y10S 977/954 Of radiant energy

Abstract

An image sensor and a method of forming an image sensor. The image sensor includes an array of pixel cells at a surface of a substrate. Each pixel cell has a photo-conversion device. At least one a micro-electro-mechanical system (MEMS) element including a photonic crystal structure is provided over at least one of the pixel cells. The MEMS-based photonic crystal element is supported by a support structure and configured to selectively permit electromagnetic wavelengths to reach the photo-conversion device upon application of a voltage. As such, the MEMS-based photonic crystal element of the invention can replace or compliment conventional filters, e.g., color filter arrays.

Claims

1. An image sensor comprising:

an array of pixel cells at a surface of a substrate, each pixel cell comprising a photo-conversion device; and

at least two micro-electro-mechanical system (MEMS) elements stacked over at least one of the pixel cells and displaced over one another at different heights from the surface of the substrate, the MEMS elements comprising;

a photonic crystal structure comprising;

an insulating layer supported by a support structure;

a plurality of pillars on the insulating layer, the pillars being spaced apart from each other; and

a conductive layer in contact with at least a portion of the pillars, wherein the photonic crystal structure is located over at least one of the pixel cells and adapted to selectively permit electromagnetic radiation having a predetermined wavelength to pass through the photonic crystal structure to the photo-conversion device of the at least one cell in response to at least one applied voltage; and

wherein the support structure is adapted to selectively displace the photonic crystal structure in a direction perpendicular to the surface of the substrate in response to the at least one applied voltage.

2. The image sensor of claim 1, wherein the MEMS elements are configured to be controllable by applied voltages to selectively permit green wavelengths of light, red wavelengths of light, and blue wavelengths of light to reach the photo-conversion device at different times.

3. The image sensor of claim 1, wherein the MEMS elements are configured to be controllable by applied voltages to selectively permit visible wavelengths of light and infrared wavelengths of light to reach the photo-conversion device at different times.

4. The image sensor of claim 1, wherein the photonic crystal structure further comprises a material within the spacing between the pillars, the material having a dielectric constant that is lower than a dielectric constant of the pillars.

5. The image sensor of claim 4, wherein the pillars comprise aluminum oxide.

6. The image sensor of claim 1 wherein the conductive layer is a metal layer.

7. A processor system comprising:

a processor; and

an optoelectronic device coupled to the processor, the device comprising;

an array of pixel cells at a surface of a substrate, each pixel cell comprising a photo-conversion device, and a plurality of micro-electro-mechanical system (MEMS) elements displaced over one another at different heights from the surface of the substrate comprising;

a photonic crystal structure comprising;

an insulating layer supported by a support structure;

a plurality of pillars on the insulating layer, the pillars being spaced apart from each other; and

a metal layer in contact with at least a portion of the pillars, wherein the photonic crystal structure is located over at least one of the pixel cells and adapted to selectively permit electromagnetic radiation having a predetermined wavelength to pass through the photonic crystal structure to the photo-conversion device of the at least one cell in response to at least one applied voltage; and

wherein the support structure is adapted to selectively displace the photonic crystal structure in a direction perpendicular to the surface of the substrate in response to the at least one applied voltage.

8. The processor system of claim 7, wherein the image sensor is a CMOS image sensor.

9. The processor system of claim 7, wherein the device is a charge coupled device image sensor.

10. The processor system of claim 7, wherein the at least one MEMS element is configured to be controllable by applied voltages to selectively permit predetermined electromagnetic wavelengths to reach the photo-conversion device at different times.

11. A method of forming an image sensor, the method comprising the acts of:

forming an array of pixel cells at a surface of a substrate, each pixel cell formed comprising a photo-conversion device; and

forming at least two micro-electro-mechanical system (MEMS) elements displaced over one another over at least one of the pixel cells comprising;

a photonic crystal structure located over at least one of the pixel cells adapted to selectively permit electromagnetic radiation having a predetermined wavelength to reach the photo-conversion device of the at least one cell in response to at least one applied voltage,

wherein the photonic crystal structure comprises an insulating layer supported by a support structure;

a plurality of pillars on the insulating layer, the pillars being spaced apart from each other; and

a conductive layer in contact with at least a portion of the pillars; and

wherein the support structure is adapted to displace the photonic crystal structure in a direction perpendicular to the surface of the substrate in response to the at least one applied voltage.

12. The method of claim 11, wherein the act of forming the plurality of MEMS elements comprises configuring the photonic crystal structures to be controllable by applied voltages to selectively permit green wavelengths of light, red wavelengths of light, and blue wavelengths of light to reach the photo-conversion device at different times.

13. The method of claim 11, wherein the act of forming the plurality of MEMS elements comprises configuring the MEMS elements to be controllable to selectively permit visible wavelengths of light and infrared wavelengths of light to reach the photo-conversion device at different times.

14. The method of claim 11, wherein the photonic crystal structure further comprises material within the spacing between the pillars, the material having a dielectric constant that is lower than a dielectric constant of the pillars.

15. The method of claim 11, wherein the conductive layer is a metal layer.