Spatial light modulator and method

• US 5,172,262 A
• Filed: 04/16/1992
• Issued: 12/15/1992
• Est. Priority Date: 10/30/1985
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hornbeck, Larry J.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/871,593
• Time in Patent Office: 243 Days
• Field of Search: 350/269, 350/320, 350/360, 350/484, 350/486, 350/487, 358/231, 358/233, 313/465, 359/230, 359/291, 359/196, 359/223, 359/224, 359/846, 359/847, 359/855
• US Class Current: 359/223.1
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 26/08 for controlling the direction of light in light guides G02B6/35
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices

Abstract

An electrostatically deflectable beam spatial light modulator with the beam composed of two layers of aluminum alloy and the hinge connecting the beam to the remainder of the alloy formed in only one of the two layers; this provides a thick stiff beam and a thin compliant hinge. The alloy is on a spacer made of photoresist which in turn is on a semiconductor substrate. The substrate contains addressing circuitry in a preferred embodiment.

Claims

1. A spatial light modulator, comprising:

(a) a plurality of pixels;

(b) each of said pixels comprising

i. a supporting spacer,

ii. an electrostatically deflectable element comprising a hinge layer under a beam layer,

iii. at least one hinge, essentially only in said hinge layer and thinner than said deflectable element, connecting said deflectable element to said supporting spacer, and

iv. addressing circuitry under said element.

2. The modulator of claim 1, wherein:

(a) said deflectable element is separated from said circuitry by said spacer including an opening under said element.

3. The modulator of claim 2, wherein:

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

4. The modulator of claim 2, wherein:

(a) said opening is of curvature characterized by plasma etch formation of said spacer in situ between said layer and element and said addressing circuitry.

5. The modulator of claim 1, wherein:

(a) said at least one hinge is two hinges.

6. The modulator of claim 1, wherein said hinge layer and said beam layer are both an aluminum alloy.

7. A method of fabricating a deflectable beam spatial light modulator, comprising the steps:

(a) forming addressing circuitry on a semiconductor substrate;

(b) forming a supporting spacer over said circuitry;

(c) forming a layer of hinge material on said spacer;

(d) forming a thick layer of beam material over said hinge material layer;

(e) patterning and etching said layers to define at least one hinge and at least one deflectable element such that said hinge is thinner than said deflectable element and is essentially only said hinge material; and

(f) etching the portion of said spacer immediately between said deflectable beam and said addressing circuitry.

8. The method of claim 7, wherein:

(a) each of said beam and hinge material is an aluminum alloy, said spacer is baked photoresist and said substrate is silicon.

9. The method of claim 7, wherein:

(a) said forming a thick layer of beam material includes patterning to define hinges, depositing beam material, and lifting off the beam material deposited on said hinge pattern.

10. The method of claim 9, wherein:

(a) said patterning to define hinges includes deposition of layers of PMMA, antireflective coating, and photoresist.

11. A method of fabricating a deflectable beam spatial light modulator, comprising the steps:

(a) forming addressing circuitry on a semiconductor substrate;

(b) forming a supporting spacer over said circuitry and substrate;

(c) depositing a hinge layer directly or indirectly over said spacer;

(d) masking a portion of said hinge layer;

(e) forming a beam layer over at least exposed portions of said hinge layer;

(f) forming a mask to define at least one hinge, at least one deflectable beam and at least one etch access hole such that said hinge is thinner than said deflectable beam and is essentially only said hinge layer; and

(g) etching the portion of said spacer between said deflectable beam and said addressing circuitry.

12. The method of claim 11, wherein said masking a portion of said hinge layer includes deposition of layers of PMMA, antireflective coating and photoresist.