Spatial light modulator

• US 4,956,619 A
• Filed: 10/28/1988
• Issued: 09/11/1990
• Est. Priority Date: 02/19/1988
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hornbeck, Larry J.
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US07/266,220
• Time in Patent Office: 683 Days
• Field of Search: 358/204, 358/206
• US Class Current: 359/317
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field

Abstract

A deflectable beam spatial light modulator formed from a structure of a reflecting layer, typically metal, on a spacer layer, typically photoresist, which in turn is on a substrate containing electronic addressing circuitry is disclosed. Also, the method of fabrication including a plasma etch after dicing of the substrate into chips is disclosed.

Claims

1. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a substrate, a spacer layer on said substrate, a reflecting layer on said spacer layer, and electrical addressing circuitry;

(c) each of said pixels including

i. an electrostatically deflectable element formed in said reflecting layer and

ii. a well formed in said spacer and located beneath said deflectable element plus adjacent portions of said reflecting layer, said well characterized by formation by plasma etching of said spacer between said substrate and said reflecting layer with said spacer on said substrate; and

(d) said reflecting layer made of conductive material.

2. The spatial light modulator of claim 1, wherein:

(a) said spacer is a planarizing spun-on material.

3. The spatial light modulator of claim 1, wherein:

(a) said deflectable elements of said pixels are electrically interconnected; and

(b) said addressing circuitry includes for each pixel and electrode on said substrate at the bottom of said well.

4. The spatial light modulator of claim 1, wherein:

(a) said deflectable element contains at least one hole through which said plasma etching of said spacer may proceed.

5. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a substrate, a spacer layer on said substrate, a reflecting layer on said spacer layer, and electrical addressing circuitry;

(c) each of said pixels including

(i) an electrostatically deflectable element formed in said reflecting layer and

(ii) a well formed in said spacer layer and located beneath said deflectable element plus adjacent portions of said reflecting layer; and

(d) said spacer layer of a planarizing spun-on material.

6. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a substrate, a spacer layer on said substrate, a reflecting layer on said spacer layer, and electrical addressing circuitry;

(c) each of said pixels including

(i) an electrostatically deflectable element formed in said reflecting layer and

(ii) a well formed in said spacer layer and located beneath said deflectable element plus adjacent portions of said reflecting layer; and

(d) said addressing circuitry including for each of said pixels an electrode on said substrate at the bottom of said well and located away from the portion of said bottom closest to said deflectable element during electrostatic deflection.

11. The spatial light modulator of claim 6, wherein:

(a) said spacer is a planarizing spun-on material.

7. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a substrate, a spacer layer on said substrate, a reflecting layer on said spacer layer, and electrical addressing circuitry;

(c) each of said pixels including

(i) an electrostatically deflectable element formed in said reflecting layer, said deflectable element of essentially square shape with connections on each of two diagonally opposed corners to the remainder of said reflecting layer, and

(ii) a well formed in said spacer layer and located beneath said deflectable element plus adjacent portions of said reflecting layer; and

(d) said addressing circuitry including for each of said pixels an electrode on said substrate at the bottom of said well and located under a portion of said deflectable element on one side of the diagonal through said connections.

12. The spatial light modulator of claim 7, wherein:

(a) said spacer is a planarizing spun-on material.

8. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a substrate, a planarizing spacer layer on said substrate, a reflecting layer on said spacer layer, and electrical addressing circuitry;

(c) each of said pixels including

(i) an electrostatically deflectable element formed in said reflecting layer, and

(ii) a well formed in said spacer layer and located beneath said deflectable element plus adjacent portions of said reflecting layer; and

(d) the bottom of said reflecting layer and the bottom of said well both electrical conductors.

13. The spatial light modulator of claim 8, wherein:

(a) said spacer is a planarizing spun-on material.

9. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a substrate, a spacer layer on said substrate, a reflecting layer on said spacer layer, and electrical addressing circuitry;

(c) each of said pixels including

(i) an electrostatically deflectable element formed in said reflecting layer, and

(ii) a well formed in said spacer layer and located beneath said deflectable element plus adjacent portions of said reflecting layer;

(d) said reflecting layer including at least a first sublayer of a first material on a second sublayer;

said

(e) said well including deposits of said first material characteristic of essentially uniform deposition of said first material on said second layer subsequent to the formation of said wells.

14. The spatial light modulator of claim 9, wherein:

(a) said spacer is a planarizing spun-on material.

10. A spatial light-modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a substrate, a planarizing spacer layer on said substrate, a reflecting layer on said spacer layer, and electrical addressing circuitry;

(c) each of said pixels including

(i) an electrostatically deflectable element formed in said reflecting layer, and

(ii) a well formed in said spacer layer and located beneath said deflectable element plus adjacent portions of said reflecting layer;

(d) said deflectable element characterized by an essentially square portion connected by a hinge portion to the remainder of said reflecting layer, said hinge portion of length measured from said square portion to said remainder greater than the width of said hinge portion.

15. The spatial light modulator of claim 10, wherein:

(a) said spacer is a planarizing spun-on material.

16. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a bottom layer, a planarizing middle layer on said bottom layer, and a conductive reflecting layer on said middle layer;

(c) each of said pixels including;

i. a deflectable element formed in said reflecting layer;

ii. an addressing electrode between said middle layer and said bottom layer and extending beneath said deflectable element; and

iii. a well formed in said middle layer, said well extending from said deflectable element to said electrode.

17. The spatial light modulator of claim 16, wherein:

(a) said deflectable element is a portion of said reflecting layer connected to the remainder of said reflecting layer by a hinge formed from said reflecting layer.

18. The spatial light modulator of claim 17, wherein:

(a) said portion of said reflecting layer is of square shape and said hinge is located at a corner of said portion.

19. The spatial light modulator of claim 16, wherein:

(a) said deflectable element is a portion of said reflecting layer connected to the remainder of said reflecting layer by two hinges formed from said reflecting layer.

20. The spatial light modulator of claim 19, wherein:

(a) said portion of said reflecting layer is of square shape and said hinges are located at diagonally opposite corners of said portion.

21. The spatial light modulator of claim 16, wherein:

(a) said well is characterized by a plasma etching of said middle layer after said reflecting layer is on said middle layer and said middle layer is on said bottom layer and said deflectable element has been formed in said reflecting layer.

22. The spatial light modulator of claim 16, wherein:

(a) said bottom layer is silicon;

(b) said middle layer is an insulating spun-on material; and

(c) said reflecting layer is predominantly aluminum.

23. The spatial light modulator of claim 16, wherein:

(a) said bottom layer is silicon with a layer of silicon dioxide;

(b) said electrode is polysilicon;

(c) said middle layer is an insulating spun-on material; and

(d) said reflecting layer is predominantly aluminum.

24. The spatial light modulator of claim 16, wherein:

(a) said bottom layer is a silicon substrate;

(b) said electrode is a diffused region in said silicon substrate;

(c) said middle layer includes a silicon dioxide layer on at least a portion of said diffused region plus polysilicon on at least a portion of said silicon dioxide and an insulator between said polysilicon and said reflecting layer; and

(d) said reflecting layer is predominantly aluminum.

25. A spatial light modulator, comprising:

(a) a plurality of pixels formed in a layered structure;

(b) said layered structure including a bottom layer, a plurality of addressing electrodes on said bottom layer, a planarizing spacer layer on said electrodes and said bottom layer, and a conductive reflecting layer on said spacer layer;

(c) each of said pixels including;

i. a deflectable element formed in said reflecting layer;

ii. one of said addressing electrodes and extending beneath said deflectable element; and

iii. a well formed in said spacer layer, said well extending from said deflectable element to said one addressing electrode and of width greater than the width of said deflectable element.

26. The spatial light modulator of claim 25, wherein:

(a) said deflectable element is a portion of said reflecting layer connected to the remainder of said reflecting layer by a hinge formed from said reflecting layer.

27. The spatial light modulator of claim 26, wherein:

(a) said portion of said reflecting layer is of square shape and said hinge is located at a corner of said portion.

28. The spatial light modulator of claim 25, wherein:

(a) said deflectable element is a portion of said reflecting layer connected to the remainder of said reflecting layer by two hinges formed from said reflecting layer.

29. The spatial light modulator of claim 28, wherein:

(a) said portion of said reflecting layer is of square shape and said hinges are located at diagonally opposite corners of said portion.

30. The spatial light modulator of claim 25, wherein:

(a) said well is characterized by a plasma etching of said spacer layer after said reflecting layer is on said spacer layer and said spacer layer is on said addressing electrodes and said bottom layer and said deflectable element has been formed in said reflecting layer.