Methods of fabricating interferometric modulators by selectively removing a material

• US 7,420,728 B2
• Filed: 03/25/2005
• Issued: 09/02/2008
• Est. Priority Date: 09/27/2004
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Floyd, Philip D., Tung, Ming-Hau, Arbuckle, Brian W.
• Primary Examiner(s): Sugarman; Scott J.
• Assistant Examiner(s): PINKNEY, DAWAYNE
• Application Number:
  US11/090,552
• Publication Number:
  US 20060076311A1
• Time in Patent Office: 1,257 Days
• Field of Search: 359/237, 359290-292, 359/295, 359/298
• US Class Current: 359/290
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0181 See-saws
• CPC Class Codes: B81C 1/00174 See-saws
• CPC Class Codes: B81C 1/00182 Arrangements of deformable or non-deformable structures, e.g. membrane and cavity for use in a transducer
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• 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

Methods for making MEMS devices such as interferometric modulators involve selectively removing a sacrificial portion of a material to form an internal cavity, leaving behind a remaining portion of the material to form a post structure. The material may be blanket deposited and selectively altered to define sacrificial portions that are selectively removable relative to the remaining portions. Alternatively, a material layer can be laterally recessed away from openings in a covering layer. These methods may be used to make unreleased and released interferometric modulators.

Claims

1. A method for making a MEMS device comprising:

depositing a material over a first electrode layer;

selectively altering a portion of the material to define a sacrificial portion of the material and a remaining portion of the material;

forming a second electrode layer over the material; and

selectively removing the sacrificial portion of the material to thereby form a cavity and a support structure of the MEMS device, the support structure comprising the remaining portion of the material, the second electrode layer comprising a moveable layer supported by the support structure;

wherein the material is a radiation-sensitive polymer; and

wherein the step of selectively altering a portion of the material comprises irradiating a portion of the radiation-sensitive polymer to thereby form an irradiated portion of the radiation-sensitive polymer and a non-irradiated portion of the radiation-sensitive polymer.

2. The method of claim 1 in which the MEMS device comprises an interferometric modulator.

3. The method of claim 2 in which at least one of the first electrode layer and the second electrode layer comprises a mirror.

4. The method of claim 1 in which the step of selectively removing the sacrificial portion of the material comprises removing the irradiated portion of the radiation-sensitive polymer.

5. The method of claim 1 in which the step of selectively removing the sacrificial portion of the sacrificial material comprises removing the non-irradiated portion of the radiation-sensitive polymer.

6. The method of claim 1 in which the step of forming the second electrode layer is conducted after the step of irradiating the portion of the radiation-sensitive polymer.

21. The method of claim 1 in which the second electrode layer is directly supported by the support structure.

22. The method of claim 1 in which the support structure comprises a post.

7. An unreleased MEMS substrate comprising a material, the MEMS substrate being configured so that a sacrificial portion of the material is removable to form a cavity;

and the MEMS substrate being further configured so that a remaining portion of the material forms a post structure of an interferometric modulator upon removal of the sacrificial portion, wherein the sacrificial portion of the material is compositionally distinct from the remaining portion of the material; and

wherein the material comprises a polymer and the sacrificial portion of the polymer has a degree of crosslinking that is different from the remaining portion of the polymer.

8. The unreleased MEMS substrate of claim 7 in which the material is a photoresist.

9. The unreleased MEMS substrate of claim 8 in which the sacrificial portion of the photoresist has a greater solubility than the remaining portion of the photoresist.

10. The unreleased MEMS substrate of claim 7 further comprising a first mirror layer and a second mirror layer, at least a portion of the material being positioned between the first mirror layer and the second mirror layer.

11. The unreleased MEMS substrate of claim 10 further comprising a mechanical layer attached to the second mirror layer.

12. The unreleased MEMS substrate of claim 11 in which a second portion of the material is positioned between the second mirror layer and the mechanical layer.

13. A method for making an interferometric modulator, the interferometric modulator comprising at least a first mirror, a second mirror separated from the first mirror by a cavity, and a post structure positioned at a side of the cavity and configured to support the second mirror spaced from the first mirror, the method comprising:

providing a substrate, the substrate having a first area configured to underlie the first mirror and a second area configured to underlie the post structure;

depositing a first mirror layer over at least the first area;

depositing a material over the first area and over the second area;

selectively altering by irradiation at least one selected from the group consisting of the material over the first area and the material over the second area; and

depositing a second mirror layer over at least the material over the first area;

the material over the first area being removable to thereby form the cavity and the post structure, where the post structure comprises the material over the second area;

wherein the material is a radiation-sensitive polymer.

14. The method of claim 13 further comprising removing at least a part of the material over the first area to thereby form the cavity.

15. The method of claim 14 in which the material over the second area remains after removing the at least a part of the material over the first area, thereby forming the post structure comprising the material over the second area.

16. The method of claim 14 further comprising forming a via configured to facilitate flow of an etchant to the material over the first area.

17. The method of claim 13, wherein selectively altering by irradiation comprises irradiating the material over the first area.

18. The method of claim 17 further comprising removing at least a part of the material over the first area to thereby form the cavity.

19. The method of claim 13, wherein selectively altering by irradiation comprises irradiating the material over the second area.

20. The method of Claim 19 further comprising removing at least a part of the material over the first area to thereby form the cavity.