METHOD FOR MANUFACTURING AN ARRAY OF INTERFEROMETRIC MODULATORS

• US 20070269748A1
• Filed: 08/01/2007
• Published: 11/22/2007
• Est. Priority Date: 04/15/2003
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Miles, Mark
• Granted Patent: US 7,723,015 B2
• Time in Patent Office: Days
• US Class Current: 430/321
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26

Abstract

In one embodiment, the invention provides a method for manufacturing an array of interferometric modulators. Each interferometric modulator comprises first and second optical layers which when the interferometric modulator is in an undriven state are spaced by a gap of one size, and when the interferometric modulator is in a driven state are spaced by a gap of another size, the size of the gap determining an optical response of the interferometric modulator. The method comprises fabricating interferometric modulators of a first type characterized by the size of the gap between its first and second optical layers when in the undriven state; fabricating interferometric modulators of a second type characterized by the size of the gap between its first and second optical layers when in the undriven state; and fabricating modulators of a third type characterized by the size of the gap between its first and second optical layers when in the undriven state, wherein fabricating the interferometric modulators of the first, second, and third types comprises using a sequence of deposition and patterning steps of not more than 9 masking steps to deposit and pattern layers of material on a substrate.

Claims

1. A method for fabricating an interferometric modulation structure comprising a plurality of spaced apart posts to support a mechanical layer over an optical layer, the method comprising:

depositing layers of material to form a stacked structure on a substrate;

patterning and etching vias in the stacked structure, the vias being contoured to define a re-entrant profile;

depositing a photo-definable material in the vias;

developing the photo-definable material through the vias; and

removing excess photo-definable material deposited adjacent the vias using a lift-off process.

2. The method of claim 1, wherein the photo-definable material includes a polymeric material.

3. A method for fabricating an interferometric modulation structure comprising a plurality of spaced apart posts to support a mechanical layer over an optical layer, the method comprising:

depositing layers of material to form a stacked structure on a substrate;

patterning and etching vias in the stacked structure, the vias being contoured to define a positively sloped profile; and

depositing at least one mechanical film over the stacked structure, wherein portions of the mechanical film that extend into the vias support the mechanical film.

4. A method for fabricating an interferometric modulator by performing subtractive definition of a multi-height sacrificial layer comprising:

depositing an multilayer sacrificial stack on a substrate for the interferometric modulator, wherein the sacrificial stack comprises a first material and a second material, wherein said first and second materials are etchable by a gas etch, and wherein said first material is etchable by a first solution but not a second solution, and wherein the second material is etchable by the second solution but not the first solution;

removing a portion of a first layer of the sacrificial stack comprising the first material by exposing it to the first solution;

removing a portion of a second layer of the sacrificial stack comprising the second material by exposing it to the second solution; and

removing a remainder of the sacrificial stack by exposing it to the gas etch.

5. The method of claim 4, wherein the first material comprises silicon.

6. The method of claim 5, wherein the second material comprises molybdenum.

7. The method of claim 4, wherein the gas etch is XeF₂.

8. The method of claim 4, wherein the first solution comprises tetramethylammonium hydroxide.

9. The method of claim 4, wherein the second solution comprises phosphoric acid, acetic acid, or nitric acid.

10. A method for fabricating an interferometric modulator by performing subtractive definition of a multi-height sacrificial layer comprising:

depositing an multilayer sacrificial stack on a substrate for the interferometric modulator, wherein the sacrificial stack comprises;

a first layer comprising a first material wherein the first material is etchable by a first solution but not a second solution, and

a second layer comprising a second material wherein the second material is etchable by the second solution but not the first solution;

masking a portion of the first layer with a resist layer;

etching an unmasked portion of the first layer with the first solution, leaving exposed a surface of the second layer not protected by the mask;

masking a portion of the surface of the second layer with a resist layer; and

etching an unmasked portion of the second layer with the second solution.

11. The method of claim 10, wherein the first material comprises silicon.

12. The method of claim 11, wherein the second material comprises molybdenum.

13. The method of claim 10, wherein the gas etch is XeF₂.

14. The method of claim 10, wherein the first solution comprises tetramethylammonium hydroxide.

15. The method of claim 10, wherein the second solution comprises phosphoric acid, acetic acid, or nitric acid.

16. A method for manufacturing an array of interferometric modulators defining multiple patterns using a single photolithographic step, the method comprising:

depositing a multi-layer etch stack on a substrate, the etch stack comprising etch material;

applying a photoresist layer over the etch stack;

positioning a gray-scale mask over the etch stack and the photoresist layer, the gray-scale mask having first and second regions of variable levels of transmission;

exposing the gray-scale mask;

developing the first region of the gray-scale mask by contacting the stack with a developing solution for an interval of time such that the second region does not develop, thereby exposing etch material under the first region; and

removing the stack from the developing solution and etching the etch material under the first region.

17. The method of claim 16, further comprising:

contacting the stack with the developing solution for an interval of time until the second region develops thereby exposing the etch material under the second region; and

removing the stack from the developing solution and etching the etch material under the second region.

18. The method of claim 17, wherein the multilayer etch stack comprises silicon.

19. The method of claim 18, wherein the multilayer etch stack comprises molybdenum.