Thin film actuated mirror array for use in an optical projection system and method for the manufacture thereof

• US 5,663,830 A
• Filed: 03/07/1995
• Issued: 09/02/1997
• Est. Priority Date: 03/09/1994
• Status: Expired due to Fees

• Current Assignee: Dongbu Daewoo Electronics Corporation
• Original Assignee: Daewoo Electronics (Government of South Korea)
• Inventors: Min, Yong-Ki, Ji, Jeong-Beom
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): CORNELY, JOHN
• Application Number:
  US08/400,065
• Time in Patent Office: 910 Days
• Field of Search: 359/290, 359/291, 359/295, 359/846, 359/848, 359/850
• US Class Current: 359/295
• CPC Class Codes: G02B 26/0816 by means of one or more reflecting elements
• CPC Class Codes: G02B 26/0858 the reflecting means being moved or deformed by piezoelectric means
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]

Abstract

An array of M×N actuated mirrors comprises an active matrix, an array of M×N elastic members, an array of M×N pairs of actuating structures and an array of M×N mirrors. Each of the elastic members is provided with a distal and a proximal ends, the proximal end including a first and a second tab portions, the first tab and the second tab portions being separated by a retraction therebetween, the distal end including a protrusion. Each of the actuating structures is located on the first and the second tab portions on each of the elastic members, respectively. Each of the mirrors is formed on top of the elastic members. When the pair of actuating structures deform in response to an electrical signal, the first and the second tab portions tilt while the remainder of the elastic member, and, the mirror formed on top thereof, stays planar, thereby allowing all of the mirrors to reflect the light beams.

Claims

1. An array of M×

N thin film actuated mirrors, wherein M and N are integers, for use in an optical projection system, said array comprising;

an active matrix including a substrate, an array of M×

N transistors and an array of M×

N pairs of connecting terminals, wherein the connecting terminals in each pair are electrically connected to each of the transistors;

an array of M×

N elastic members, each of the elastic members being provided with a distal and a proximal ends, and a top and a bottom surfaces, the proximal end including a first tab and a second tab portions, the first tab and second tab portions being separated by a retraction therebetween, the distal end including a protrusion, wherein the protrusion from each of the elastic members extends into the retraction of a successive elastic member in the array;

an array of M×

N pairs of actuating structures, each pair of the actuating structures being located on the first and second tab portions on each of the elastic members, respectively, each of the actuating structures including a bias electrode, a motion-inducing thin film layer and a signal electrode with the bias and the signal electrodes being placed on top and bottom of the motion-inducing thin film layer, respectively, the bias electrode being made of an electrically conducting, light reflecting material, the signal electrode in each of the actuating structures in each pair being electrically connected to a same transistor in the active matrix, wherein an electrical signal applied across the motion-inducing thin film layer between the bias and the signal electrodes in each of the actuating structures causes a deformation of the motion-inducing thin film layer, and hence said each of the actuating structures;

an array of M×

N pairs of supporting members, each pair of the supporting members being used for holding each of the elastic members in place, wherein the first and second tab portions in each of the elastic members are secured to each of the supporting members in each pair, respectively;

an array of M×

N mirrors for reflecting light beams, each of the mirrors being formed on the top surface of the elastic member, each of the mirrors being made of the same material as the bias electrode, such that when the pair of actuating structures deform in response to the electrical signal, the first and second tab portions on the elastic member with the actuating structures attached thereto tilt while the remainder of the elastic member, and, hence, the mirror formed on top thereof, stays planar, thereby allowing all of the mirror to reflect the light beams.

2. The thin film actuated mirror array of claim 1, wherein each of the supporting members in made of a ceramic.

3. The thin film actuated mirror array of claim 1, wherein each of the elastic members is made of a ceramic.

4. The thin film actuated mirror array of claim 1, wherein each of the thin film actuated mirrors is provided with a pair of conduits, each of the conduits extending from a signal electrode to a corresponding connecting terminal in the active matrix via a supporting member, thereby electrically connecting the signal electrode and the connecting terminal.

5. The thin film actuated mirror array of claim 4, wherein each of the conduits is made of a metal.

6. The thin film actuated mirror array of claim 3, wherein each of the elastic members is provided with a distal and a proximal ends, the proximal and including a first, a second and a center tab portions, the first, second and center tab portions being separated by a gap therebetween.

7. The thin film actuated mirror array of claim 1, wherein each of the signal electrodes and the motion-inducing layer on top thereof are surrounded by an insulation in order to prevent the bias electrode from coming in contact with the signal electrode.

8. The thin film actuated mirror array of claim 1, wherein the motion-inducing thin film layer is made of an electrostrictive material or a piezoelectric material.

9. The thin film actuated mirror array of claim 1, wherein each of the signal electrodes is made of platinum or platinum/titanium.

10. A method for manufacturing an array of M×

N thin film actuated mirrors for use in an optical projection system, said method comprising the steps of;

a) providing an active matrix having a top surface, the active matrix including a substrate, an array of M×

N transistors and an array of M×

N pairs of connecting terminals on the top surface thereof;

b) forming a sacrificial layer on the top surface of the active matrix in such a way that the sacrificial layer completely covers the array of M×

N pairs of connecting terminals;

c) removing the sacrificial layer surrounding each of the connecting terminals;

d) forming a supporting member around each of the connecting terminals;

e) depositing an elastic layer on top of the sacrificial layer and supporting members;

f) forming an array of M×

N pairs of conduits, each of the conduits extending from top of the elastic layer to each of the connecting terminals via each of the supporting members;

g) providing an array of M×

N pairs of signal electrodes on top of the elastic layer in such a way that each of the signal electrodes is in contact with each of the conduits and hence each of the connecting terminals;

h) forming a motion-inducing thin film layer on top of each of the signal electrodes;

i) depositing a layer made of an electrically conducting light reflecting material on top of the motion inducing and elastic layers to thereby form a semifinished array of actuated mirror structures;

j) patterning the semifinished array of actuated mirror structures into an array of M×

N actuated mirror structures, each of the actuated mirror structures including a pair of supporting members, a sacrificial layer, an elastic member with a pair of actuating structures and a mirror made of the electrically conducting, light reflecting material formed on top thereof, each of the actuating structures having a bias electrode made of the electrically conducting, light reflecting material, the motion-inducing thin film layer and the signal electrode, the elastic member further being provided with a distal and a proximal ends, and a top and bottom surfaces, the proximal end including a first tab and a second tab portions, the first and second tab portions being separated by a retraction therebetween, the distal end including a protrusion, each of the actuating structures being placed on top of the first and second tab portions, respectively, wherein the protrusion from each of the elastic members, and hence, the actuated mirror structures, extends into the retraction of a successive elastic member, and hence, a successive actuated mirror structure, in the array; and

k) removing the sacrificial layer to thereby form said array M×

N thin film actuated mirrors.

11. The method of claim 10, wherein the sacrificial layer is made of a metal;

or a phosphor silicate glass(PSG) or a poly-Si.

12. The method of claim 11, wherein the sacrificial layer is formed using a chemical vapor deposition (CVD) or a spin coating method if the sacrificial layer is made of a metal, a CVD method if the sacrificial layer is made of a PSG, a CVD method if the sacrificial layer is made of a poly-Si.

13. The method of claim 10, wherein the first supporting layer is formed by using a combination of a photolithography method followed by a sputtering method or a CVD method.

14. The method of claim 10, wherein the signal electrode is formed by using a sputtering method.

15. The method of claim 10, wherein the motion-inducing layer is formed by using a sol-gel method or a sputtering method.

16. The method of claim 10, wherein the bias electrode and the mirror are formed using a sputtering or a vacuum evaporation method.

17. The method of claim 10, wherein the semifinished array of actuated mirror structures is patterned into the array of M×

N actuated mirror structures by using a dry etching method or a photolithography method.

18. The method of claim 10, wherein the sacrificial layer is removed by using an etching method.