Utilizing a protective plug to maintain the integrity of the FTP shrink hinge

• US 7,262,900 B2
• Filed: 05/10/2005
• Issued: 08/28/2007
• Est. Priority Date: 05/10/2005
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Baker, James C., DiCarlo, Anthony, Mezenner, Rabah, Harakas, George, Franklin, Mark A.
• Primary Examiner(s): Thompson; Timothy
• Application Number:
  US11/125,473
• Publication Number:
  US 20060255424A1
• Time in Patent Office: 840 Days
• Field of Search: 359/224, 359/223, 359/291, 359/290, 359/295
• US Class Current: 359/291
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 2203/0181 See-saws
• CPC Class Codes: B81C 1/00801 Avoid alteration of functional structures by etching, e.g. using a passivation layer or an etch stop layer B81C1/00595, B81C1/00468 take precedence
• CPC Class Codes: B81C 2201/053 Depositing a protective layers
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B

Abstract

As robust hinge post structure for use with torsional hinged devices such as micromirrors and method of manufacturing is disclosed. The fabrication process uses a protective layer such as BARC on the bottom of the aperture used to form the hinge post structure to protect an oxide layer during an etching step. The oxide layer, in turn protects the metal layer at the bottom of the aperture. Therefore, the metal layer, the oxide layer, and the protective layer prevent the erosion and/or pitting of the bottom electrode during a cleaning process, and provide additional support to the structure.

Claims

1. A process for forming a metal hinge post structure over an electrically conductive electrode comprising the steps of:

forming a patterned spacer layer having a top surface on said electrically conductive electrode, said patterned spacer layer defining at least one hinge post aperture extending from said top surface through said spacer layer to said electrically conductive electrode;

forming a metal layer over said spacer layer;

forming an oxide layer over said metal layer;

depositing a protective layer over said oxide layer, said protective layer deposited to a first thickness over said top surface of said spacer layer and to a second thickness in said at least one hinge post aperture, said second thickness greater than said first thickness;

etching said protective layer to expose said oxide layer, such that only a layer of said protective material remains at the bottom of said at least one hinge post aperture;

anisotropically etching said oxide layer such that a cup-shaped layer of oxide remains in said at least one hinge post aperture; and

cleaning said metal layer and said at least one hinge post aperture.

2. The process of claim 1 further comprising the step of removing said spacer layer.

3. The process of claim 1 wherein said patterned spacer layer defines a multiplicity of hinge post apertures.

4. The process of claim 1 wherein said process for forming a metal hinge post structure further comprises forming a torsional hinge connected to said metal hinge post structure.

5. The process of claim 1 wherein said step of forming an oxide layer comprises forming an oxide layer having a thickness of between about 2,000 Å

and about 5,000 Å

.

6. The process of claim 1 wherein said protective layer is an ARC layer or a photoresist layer.

7. The process of claim 6 wherein said step of depositing a protective layer comprises spinning on a BARC layer.

8. The process of claim 7 wherein said step of spinning on said ARC layer comprises spinning on said first thickness to about 890 Å

on said top surface and such that 2000 Å

-4000 Å

is deposited in said at least one hinge post aperture.

9. The process of claim 8 wherein the step of etching said protective layer leaves a layer of BARC material at the bottom of said at least one said hinge post aperture having a thickness of between about 1000 Å

to about 3000 Å

.

10. The process of claim 1 wherein said step of anisotropically etching said oxide layer comprises the step of anisotropically plasma etching said oxide layer.

11. The process of claim 1 wherein said step of forming an oxide layer comprises the step of depositing an oxide layer comprising 66% aluminum and 33% titanium.

12. The process of claim 1 wherein said step of cleaning said at least one hinge post aperture comprising cleaning with a solution of ammonia hydroxide (NH₃OH).

13. The process of claim 1 wherein said conductive electrode comprises a material selected from the group consisting of aluminum, titanium, and a combination of aluminum, titanium and silicon.

14. The process of claim 1 wherein said step of forming a metal layer comprises forming a layer of “

binge”

metal.

15. The process of claim 9 further comprising the step of “

ashing”

said oxide layer on said top surface.

16. The process of claim 1 wherein said spacer layer comprises silicon.

17. The process of claim 1 wherein said metal layer has a thickness of between about 400 Å

and 900 Å

.

18. A process for forming a multiplicity of metal hinge post structures over an electrically conductive electrode layer for supporting a reflective pixel having surface dimensions of less than 10 μ

m comprising the steps of;

forming a patterned spacer layer having a top surface on said electrically conductive electrode layer, said patterned spacer layer defining a multiplicity of hinge post apertures extending from said top surface through said spacer layer to said electrically conductive electrode layer;

forming a layer of “

binge”

metal over said spacer layer, including said multiplicity of hinge post apertures;

forming an oxide layer of aluminum and titanium over said layer of “

binge”

metal, including said multiplicity of hinge post apertures;

depositing a BARC layer over said oxide layer including said multiplicity of hinge post apertures, said BARC layer deposited to a first thickness over said top surface of said spacer layer and to a second thickness in said multiplicity of hinge post apertures, said second thickness being greater than said first thickness;

etching said BARC layer to expose said oxide layer, such that only a layer of BARC material remains at the bottom of said multiplicity of hinge post apertures;

anisotropically plasma etching said oxide layer such that a cup-shaped layer of oxide remains in said multiplicity of hinge post apertures; and

cleaning said metal layer and said multiplicity of hinge post apertures.

19. A hinge post structure formed over a substrate including a conductive electrode comprising:

an electrically conductive electrode;

at least one cup-shaped metal structure formed above said electrically conductive electrode, said at least one cup-shaped metal structure defining sidewalls and a planar bottom portion next to said electrically conductive electrode;

an oxide layer formed on said planar bottom portion and said sidewalls of said at least one cup-shaped metal structure; and

a protective layer covering said oxide layer formed on said planar bottom portion, wherein said protective layer does not substantially extend up said sidewalls.

20. The hinge post structure of claim 19 wherein said cup-shaped metal structure further comprises torsional hinges extending from top portion thereof.

21. The structure of claim 19 wherein said oxide layer has a thickness of between about 2,000 Å

and about 5,000 Å

.

22. The structure of claim 19 wherein said protective layer is a material selected from the group consisting of ARC or photoresist.

23. The structure of claim 19 wherein said protective layer is a BARC layer having a thickness of between about 1000 Å

and 3000 Å

.

24. The structure of claim 19 wherein said oxide layer comprises about 66% aluminum and 33% titanium.