Source: http://www.google.com/patents/US5984481?dq=6861155
Timestamp: 2016-05-29 14:27:53
Document Index: 29647884

Matched Legal Cases: ['arts 62', 'arts 62', 'arts 62', 'arts 62', 'arts 62', 'arts 62']

Patent US5984481 - Array of thin film actuated mirrors for use in an optical projection system ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsAn array of M�N thin film actuated mirrors for use in an optical projection system comprises an active matrix, an array of M�N thin film actuating structures, and an array of M�N mirror layers for reflecting light beams, each of the mirror layers further including a first side, a second opposing side...http://www.google.com/patents/US5984481?utm_source=gb-gplus-sharePatent US5984481 - Array of thin film actuated mirrors for use in an optical projection system and method for the manufacture thereofAdvanced Patent SearchPublication numberUS5984481 APublication typeGrantApplication numberUS 09/150,747Publication dateNov 16, 1999Filing dateSep 10, 1998Priority dateNov 16, 1993Fee statusPaidAlso published asCA2176347A1, CN1047904C, CN1135276A, DE69423070D1, DE69423070T2, EP0653657A1, EP0653657B1, US5835293, US6030083, WO1995014351A1Publication number09150747, 150747, US 5984481 A, US 5984481A, US-A-5984481, US5984481 A, US5984481AInventorsYong-Ki Min, Myoung-Jin KimOriginal AssigneeDaewood Electronics Co., Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (28), Referenced by (4), Classifications (27), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetArray of thin film actuated mirrors for use in an optical projection system and method for the manufacture thereof
An array of M�N thin film actuated mirrors for use in an optical projection system comprises an active matrix, an array of M�N thin film actuating structures, and an array of M�N mirror layers for reflecting light beams, each of the mirror layers further including a first side, a second opposing side and a center portion located therebetween, wherein the first side and the second opposited side of each of the mirror layers are secured on top of the first and second actuating parts of each of the actuating structures, respectively, such that when the first and second actuating parts in each of the actuating structures deform in response to an electrical signal applied between the first and second electrodes, the center portion of the corresponding mirror layer tilts while remaining planar, thereby allowing all of the center portion to reflect the light beams, resulting in an increased optical efficiency.
In FIG. 1, there is shown a cross sectional view of an M�N electrodisplacive actuated mirror array 10 for use in an optical projection system, disclosed in a copending commonly owned application, U.S. Ser. No. 08/278,472, entitled "ELECTRODISPLACIVE ACTUATED MIRROR ARRAY", now U.S. Pat. No. 5,735,026, comprising: an active matrix 11 including a substrate 12 and an array of M�N transistors thereon; an array 13 of M�N electrodisplacive actuators 30, each of the electrodisplacive actuators 30 including a pair of actuating members 14, 15, a pair of bias electrodes 16, 17, and a common signal electrode 18; an array 19 of M�N hinges 31, each of the hinges 31 fitted in each of the electrodisplacive actuators 30; an array 20 of M�N connecting terminals 22, each of the connecting terminals 22 being used for electrically connecting each of the signal electrodes 18 with the active matrix 11; and an array 21 of M�N mirrors 23, each of the mirrors 23 being mounted on top of each of the M�N hinges 31.
It is another object of the present invention to provide an improved and novel method for manufacturing an array of M�N actuated mirrors which will give higher reproducibilitv, reliability and yield.
It is a further object of the present invention to provide an array of M�N actuated mirrors having a nove structure and capable of maintaining a performance integrity after an extended use.
In accordance with one aspect of the present invention, there is provided an array of M�N thin film actuated mirrors for use in an optical projection system, the array comprising: an active matrix including a substrate, an array of M�N transistors and an array of M�N connecting terminals; an array of M�N thin film actuating structures, each of the actuating structures including a first and a second actuating parts, the first and second actuating parts being identically structured, each of the first and second actuating parts being provided with a top and a bottom surfaces, a proximal and a distal ends, each of the first and second actuating parts having at least a thin film layer of a motion-inducing material including a top and a bottom surfaces and a first and a second electrode with the first electrode being placed on the top surface of the motion-inducing thin film layer, and the second electrode, on the bottom surface of the motion-inducing thin film layer, wherein an electrical signal applied across the motion-inducing thin film layer between the first and second electrodes of each actuating part causes a deformation of the motion-inducing thin film layer, and hence the actuating part; an array of M�N supporting members, each of the supporting members being provided with a top and a bottom surfaces, wherein each of the supporting members is used for holding each of the actuating structures in place and also for electrically connecting each of the actuating structures with the active matrix; and an array of M�N mirror layers, each of the mirror layers including a mirror for reflecting light beams and a supporting layer, each of the mirror layers further including a first side, a second opposing side and a center portion located therebetween, wherein the first side and the second opposing side of each of the mirror layers are secured on top of the first and second actuating parts of each of the actuating structures, respectively, such that when the first and second actuating parts in each of the actuating structures deform in response to the electrical signal, the center portion of the corresponding mirror layer tilts while remaining planar, thereby allowing all of the center portion to reflect the light beams, resulting in an increased optical efficiency
In accordance with another aspect of the present invention, there is provided a novel method for manufacturing an array of M�N actuated mirrors for use in an optical projection system, utilizing the known thin film techniques, the method comprising the steps of: (a) providing an active matrix having a top and a bottom surfaces, the active matrix including a substrate, an array of M�N transistors and an array of M�N connecting terminals; (b) forming a first supporting layer on the top surface of the active matrix, the first supporting layer including an array of M�N pedestals corresponding to the array of M�N supporting members in the array of M�N thin film actuated mirrors and a first sacrificial area; (c) treating the first sacrificial area of the first supporting layer to be removable; (d) depositing a first thin film electrode layer on the first supporting layer; (e) providing a thin film motion-inducing layer on the first thin film electrode layer; (f) forming a second thin film electrode layer on the thin film motion-inducing layer; (g) patterning the first thin film electrode layer, the thin film motion-inducing layer and the second thin film electrode layer into an array of M�N actuating structures and an empty area surrounding thereof, each of the actuating structures further including a first and a second actuating parts; (h) forming second sacrificial layer on the empty area surrounding each of the actuating structures; (i) treating the second sacrificial layer to be removable; (j) patterning the second sacrificial layer into an array of M�N sacrificial members; (k) depositing a second supporting layer on top of the array of M�N actuating structures and the second sacrificial layer patterned in the previous step; (l) depositing a light reflecting layer on top of the second supporting layer; (m) pattering the light reflecting layer and the second supporting layer into an array of M�N mirror layers; and (n) removing the first sacrificial areas and the array of M�N sacrificial members to thereby form said array of M�N thin film actuatec mirrors.
FIG. 3 represents a detailed cross sectional view of the thin film actuated mirror array 50, shown in FIG. 2. Tne active matrix 52 includes a substrate 59, an array of M�N transistors (not shown) and an array 60 of M�N connecting terminals 61. Each of the actuating structures 54 includes identically structured first actuating and second actuating parts 62(a), 62(b), wherein each actuating part, e.g., 62(a), is provided with a top and a bottom surfaces 63, 64, a proximal and a distal ends 65, 66. Each actuating part, e.g., 62(a), further has at least a thin film layer 67 of a motion-inducing material, e.g., a piezoelectric material, an electrostrictive material or a magnetostrictive material, including a top and a bottom surface 68, 69 and a first and a second electrodes 70, 71 with the first electrode 70 being placed on the top surface 68 of the motion-inducing layer 67 and the second electrode 71, on the bottom surface 71 of the motion-inducing layer 67. In the case when the motion-inducing layer 67 is made of a piezoelectric material., e.g., lead zirconium titanate (PZT), it must be poled. The first and second electrodes are made of a metal such as gold (Au) or silver (Ag).
By way of example of the first embodiment, there are illustrated in FIGS. 3 and 7 an array 50 of M�N thin film actuated mirrors 51 comprising an array 53 of M�N actuating structures 54, made of a piezoelectric material, e.g., PZT. An electric field is applied across the piezoelectric thin film layer 67 located between the first and second electrodes 70, 71 in each of the actuating parts 62(a), 62(b) in each of the actuating structures 54. The application of the electric field will either cause the piezoelectric material to contract or expand, depending on the polarity of the electric field with respect to the poling of the piezoelectric material. Ithe polarity of the electric field corresponds to the polarity of the piezoelectric material, the piezoelectric material will contract. If the polarity of the electric field is opposite the polarity of the piezoelectric material, the piezoelectric material will expand.
There is shown in FIG. 8 a cross sectional view of a second embodiment of an array 100 of M�N thin film actuated mirrors 101, wherein the second embodiment is similar to the first embodiment except that each of the first and second actuating parts 62(a), 62(b) in each of the actuating structures 54 is of a bimorph structure, including a first electrode 70, a second electrode 71, an intermediate metal layers 87 an upper motion-inducing thin film layer 89 having a top and a bottom surfaces 90, 91 and a lower motion-inducing thin film layer 92 provided with a top and bottom surfaces 93, 94. In each of the actuating parts 62(a), 62(b), the upper and lower motion-inducing thin film layers 89, 92 are separated by the intermediate metal layer 87, the first electrode 70 being placed on the top surface 90 of the upper motion-inducing thin film layer 89, and the second electrode 71, on the bottom surface 94 of the lower motion-inducing thin film layer 92.
As an example of how the second embodiment functions, assume that the upper and lower motion-inducing layers 89, 90 in the array 100 of M�N thin film actuated mirrors 101 shown in FIG. 8 are made of a piezoelectric material, e.g., PZT. When an electric field is applied across each of the actuating structures 54, the upper and lower motion-inducing thin film piezoelectric layers 89, 92, of the actuating structure 54 will either bend upward or downward, depending on the soling of the piezoelectric material and the polarity of the electric field. For example, if the polarity causes the upper motion-inducing thin film piezoelectric layer 89 to contract, and the lower motion-inducing thin film piezoelectric layer 92 to expand, the actuating parts 62(a), 62(b) in each of the actuating structures 54 will bend upward. In this situation, the impinging light is deflected at a smaller angle from the actuated mirror 51 than the deflected light from the unactuated actuated mirror 51. However, if the polarity of the piezoelectric material and the electric field causes the upper motion-inducing thin film piezoelectric layer 89 to expand and the lower motion-inducing thin film piezoelectric layer 92 to contract, the actuating structure 54 will bend downward. In this situation, the impinging light is deflected at a larger angle from the actuated mirror 51 than the deflected light from the unactuated actuated mirror 51.
In the subsequent step, there is formed on the top surface 102 of the active matrix 52 a first supporting layer 106, including an array 107 of M�N pedestals 108 corresponding to the array 55 of M�N supporting members 56 and a first sacrificial area 109, wherein the first supporting layer 106 is formed by: depositing a first sacrificial layer (not shown) on the entirety of the top surface 102 of the active matrix 52; forming an array of M�N empty slots (not shown), to thereby generated the first sacrificial area 109, each of the empty slots being located around each of the M�N connecting terminals 61; and providing a pedestal 108 in each of the empty slots, as shown in FIG. 12B. The first sacrificial layer is formed by using a sputtering method, the array of empty slots, using an etching method, and the pedestals, using a sputtering or a chemical vapor deposition (CVD) method, followed by an etching method. The sacrificial area 109 of the first supporting layer 106 is then treated so as to be removable later using an etching method or the application of chemicals.
Thereafter, the first thin film electrode layer 111, the thin film motion-inducing layer 112 and the second thin film electrode layer 113 are patterned into an array 53 of M�N actuating structures 54 and an empty area (not shown) surrounding each of the actuating structures 54, wherein each of the actuating structures 54 includes the first and second actuating parts 62(a), 62(b), as shown in FIG. 12E.