Method of making a low voltage micro-mirror array light beam switch

• US 6,379,510 B1
• Filed: 11/16/2000
• Issued: 04/30/2002
• Est. Priority Date: 11/16/2000
• Status: Expired due to Fees

• Current Assignee: Computer Optics, Inc. (Clear Align North)
• Original Assignee: Gareth A. Hughes, Jonathan S. Kane
• Inventors: Kane, Jonathan S., Hughes, Gareth A.
• Primary Examiner(s): Nguyen, Nam
• Assistant Examiner(s): Cantelmo, Gregg
• Application Number:
  US09/714,505
• Time in Patent Office: 530 Days
• Field of Search: 204/192.34, 204/192.27, 427/579, 427/588, 427/255.37, 427/100, 427/125, 427/162, 216/67, 438/29, 438/31, 29/25, 29/35
• US Class Current: 204/192.34
• CPC Class Codes: B81B 2201/045 Optical switches
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81C 1/00142 Bridges deformable micromirrors G02B26/0841
• CPC Class Codes: B81C 2201/0132 Dry etching, i.e. plasma etching, barrel etching, reactive ion etching [RIE], sputter etching or ion milling
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 26/0858 the reflecting means being moved or deformed by piezoelectric means
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/3556 NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• CPC Class Codes: G02B 6/3578 Piezoelectric force piezoelectric forces controlling reflecting elements in general G02B26/0858; piezo-optic devices G02F1/0131
• CPC Class Codes: G02B 6/3584 constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching MEMS per se B81B, B81C
• CPC Class Codes: H10N 30/2043 connected at their free ends, e.g. parallelogram type
• CPC Class Codes: H10N 39/00 Integrated devices, or assemblies of multiple devices, comprising at least one piezoelectric, electrostrictive or magnetostrictive element covered by groups H10N30/00 – H10N35/00

Abstract

A method of making a micro-mirror light beam switch having a thin flexible movable support member for supporting a thin central reflective mirror surface thereon and for supporting a plurality of thin unimorph piezoelectric cantilevered mirror actuators mechanically coupled between a fixed substrate and movable hinging portions of the thin movable support member. The method employs thin film deposition techniques and photolithography for readily forming the extremely thin switch, whereby the components thereof are substantially co-planar for precisely controlled, multi-axial micro-mirror motion and low voltage operation necessary for the rapid switching of optical traffic from fiber to fiber in the next-generation optical networks.

Claims

1. A method of making by thin film deposition techniques a micro-mirror light beam switch having a thin movable support member (5) for supporting a thin central reflective mirror surface (6) thereon and for supporting a plurality of thin piezoelectric cantilevered mirror actuators (1a) mechanically coupled between a fixed substrate (7) and movable portions of said thin movable support member comprising the steps of:

(a) depositing by chemical vapor deposition a support material layer (8) of silicon nitride or silicon dioxide of 1-3 microns thickness upon a silicon wafer substrate (7);

(b) thereafter depositing by sputtering or evaporation, bottom electrode layer (9) by sputtering or evaporation of 100-300 angstroms of titanium for adhesion and then depositing 1000-15000 angstroms of platinum;

(c) thereafter depositing by chemical vapor deposition or SolGel process, PZT piezoelectric layer (10) to a thickness of between 0.5 and 1.0 microns;

(d) thereafter depositing by chemical vapor deposition or evaporation, 1000-1500 angstroms of platinum or gold, forming a top electrode layer (11);

(e) thereafter etching said top electrode layer using ion milling to form top actuator electrode structure;

(f) etching piezoelectric layer (10) using ion milling to remove piezoelectric material from areas between said top actuator electrode structure;

(g) etching bottom electrode layer (9) to form bottom actuator electrode structure;

(h) etching support material (8) to form support structures for said thin piezoelectric cantilevered mirror actuators (11) and the mirror;

(i) etching substrate from beneath the support material (8) to create a free-floating central mirror area with cantilevered mirror actuators on each side; and

(j) depositing reflective mirror material (12) to thickness of between 0.2 and 1.0 microns.

2. A method of making by thin film deposition techniques a micro-mirror light beam switch having a thin movable support member (5) for supporting a thin central reflective mirror surface (6) thereon and for supporting a plurality of thin piezoelectric cantilevered mirror actuators (1a) mechanically coupled between a fixed substrate (7) and movable portions of said thin movable support member comprising the steps of:

(a) depositing a layer (8) of silicon nitride or silicon dioxide layer of 1-3 microns thickness upon a substrate (7);

(b) thereafter depositing bottom electrode layer (9);

(c) thereafter depositing piezoelectric layer (10) to a thickness of between 0.5 and 20 microns;

(d) thereafter depositing top electrode layer (11);

(e) etching a top electrode structure;

(f) etching piezoelectric layer (10) to remove piezoelectric material from areas between said top electrode structure;

(g) etching bottom electrode layer (9) to form bottom actuator electrode structure;

(h) etching support material (8) to form support structures for said thin piezoelectric cantilevered mirror actuators piezoelectric actuators (11) and said reflective mirror surface;

(i) etching said substrate from beneath the support material (8) to create a free-floating central area with said cantilevered mirror actuators on opposite sides thereof; and

(j) depositing reflective mirror material (12).

3. The method of claim 2 wherein said piezoelectric layer is selected from the group consisting of barium titanate, zinc oxide, lead zirconium titanate (PZT) and polyvinylidene fluoride.

4. The method of claim 3 wherein said piezoelectric layer is lead zirconium titanate (PZT).

5. The method of claim 2 wherein said piezoelectric layer is deposited to a thickness within the range of 0.5-1 microns.

6. The method of claim 3 wherein said piezoelectric layer is deposited to a thickness within the range of 0.5-1 microns.

7. The method of claim 4 wherein said piezoelectric layer is deposited to a thickness within the range of 0.5-1 microns.

8. The method of any one of claims 2-7 wherein said reflective mirror material is deposited to a thickness of between 0.2 and 1.0 microns.

9. The method of any one of claims 2-7 wherein said top electrode layer is platinum or gold, deposited to a thickness of 1000-1500 angstroms.

10. The method of any one of claims 2-7 wherein said bottom electrode layer is formed by depositing 100-300 angstroms of titanium for adhesion, then 1000-1500 angstroms of platinum over said titanium.

11. The method of claim 8 wherein said bottom electrode layer is formed by depositing 100-300 angstroms of titanium for adhesion, then 1000-1500 angstroms of platinum over said titanium.

12. The method of claim 9 wherein said bottom electrode layer is formed by depositing 100-300 angstroms of titanium for adhesion, then 1000-1500 angstroms of platinum over said titanium.

13. The method of any one of claim 2-7 wherein etching of said piezoelectric layer in accordance with step (f) is rapidly performed by the use of an ultrasonic chemical bath containing a mixture of HF:

HCI;

DI water.