JP2009093120A - Optical reflection element - Google Patents

Abstract

An object of the present invention is to realize a small-sized optical reflecting element capable of realizing a predetermined swing motion by applying a small drive voltage to a piezoelectric diaphragm in a biaxial optical reflecting element.
A first frame body 14 having a concave portion 13, first actuator portions 16A and 16B, a second frame body 17, second actuator portions 19A and 19B, and an optical reflection portion 20 are provided. The first actuator parts 16A and 16B have first piezoelectric vibration parts 21A and 21B at least in the longitudinal direction, and the second actuator parts 19A and 19B have second piezoelectric vibration parts 26A and 26B at least in the longitudinal direction. And the drive axes of the first actuator parts 16A and 16B and the second actuator parts 19A and 19B are orthogonal to each other.
[Selection] Figure 1

Description

  The present invention relates to an optical reflection element used in an optical reflection projection apparatus using laser light.

  Conventionally, this type of optical reflecting element is supported on the frame 51 by a frame 51 and a support shaft 53 that is separated from the frame 51 by a gap 52 and provided inside the gap 52 as shown in FIG. The frame body 54, an optical reflecting portion 57 that is separated from the frame body 54 by a gap 55 and is supported by the frame body 54 by a support shaft 56 provided inside the gap 55, and one end of the frame body 51. A piezoelectric diaphragm 59 connected at the other end to the support shaft 53 and a piezoelectric diaphragm 60 connected at one end to the frame body 54 and connected at the other end to the support shaft 56 are provided. The support shaft 56 is provided so that the axial direction of the support shaft 53 is orthogonal to the support shaft 53, and the frame 54 is centered on the support shaft 53, and the optical reflecting portion 57 is oscillated about the support shaft 56. The reflected light of the light incident on the unit 57 is scanned two-dimensionally It had realized the configuration. Further, this optical reflecting element is applied to a display such as a projector by combining a semiconductor laser light source and the like as shown in FIG. 8 (see, for example, Patent Document 1).

As an application example of such an optical reflection element, there is a projector device that displays an image on a screen. The principle of this projector device is to cause a frame 51 to swing in the X-axis direction as shown in FIG. At the same time, by causing the frame body 54 supported by the frame body 51 to swing in the Y-axis direction, the optical reflector 57 supported by the frame body 54 is caused to swing in the biaxial directions of the XY axes. Thus, the light incident from the laser 62 and reflected by the optical reflection unit 57 can be scanned two-dimensionally on the screen 58, and as a result, an optical reflection image can be formed on the screen 58.
JP 2005-148459 A

  However, the optical reflecting element having the conventional configuration has a problem that it is difficult to reduce the size.

  That is, in the conventional configuration, in order to bend the piezoelectric diaphragm to a predetermined angle, it is necessary to secure the length of the piezoelectric diaphragm, and as a result, it is difficult to reduce the size.

  An object of the present invention is to realize a small-sized optical reflecting element that constitutes a swinging motion having a predetermined amplitude in an optical reflecting element using piezoelectric vibration.

  In order to solve the above-described conventional problems, the present invention provides a first frame body having a recess, a meander-shaped first actuator section supported at one end by the first frame body, and a first actuator section. A second frame supported at the other end of the first frame, a meander-shaped second actuator part supported at the one end by the second frame, and an optical reflecting part supported at the end of the second actuator part. The first actuator unit has at least a first piezoelectric vibrating unit in the longitudinal direction, the second actuator unit has at least a second piezoelectric vibrating unit in the longitudinal direction, and the first actuator unit and the first actuator unit The drive axes of the two actuator parts are orthogonal to each other.

  With this configuration, the optical reflecting element according to the present invention realizes a meander-shaped thin piezoelectric actuator structure that can take a large amount of displacement inside the frame body provided with the recesses. Even if the length is reduced, it is possible to increase the bending angle of the longitudinal diaphragm per sheet, and it is possible to reduce the size of the optical reflecting element and to apply a small driving voltage to the piezoelectric diaphragm. By providing the optical reflection unit, it is possible to cause the optical reflection unit to oscillate with a predetermined amplitude, and to realize an optical reflection element that can efficiently and two-dimensionally scan the reflected light incident on the optical reflection unit. Can do.

(Embodiment 1)
Hereinafter, the optical reflecting element according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of the optical reflecting element according to the first embodiment, and FIG. 2 is a cross-sectional view taken along the line AA in FIG.

  As shown in FIGS. 1 and 2, the optical reflecting element according to the first embodiment includes a first frame 14 in which a recess 13 having a predetermined depth is formed, and a gap 15 in the internal space of the recess 13. A second frame body 17 that is separated and supported by first actuator portions 16A and 16B having a meander shape disposed in the internal space of the recess 13 is provided.

  At this time, the depth of the recess 13 is indispensable to ensure a distance that a part of each vibration part does not contact the bottom surface of the recess 13 by swinging when each vibration part swings. . The contact angle when used for an optical mirror used in a normal projector or the like varies depending on the shape of the optical mirror, but is assumed to be about ± 5 to 6 degrees if miniaturization is assumed. In order to swing the optical mirror at the touch angle, the depth of the recess 13 is preferably 200 μm or more. The depth of the concave portion 13 is such that a part of the swinging portion contacts the bottom surface of the concave portion 13 even when the length of the beam in the longitudinal direction is 2 mm or less and the deflection angle of the optical reflecting portion 20 is ± 6 degrees. It is possible to provide an optical reflection element having no surface.

  Further, inside the second frame body 17, the optical reflector 20 is separated by a gap 18 and supported by second actuator parts 19 </ b> A and 19 </ b> B having a meander shape provided inside the gap 18. And.

  The first actuator part 16A has a meander shape in which rectangular piezoelectric vibration parts 21A, 22A, 23A, 24A, and 25A are alternately joined, and the first actuator part 16B has piezoelectric vibration parts 21B, 22B, 23B, 24B, 25B has a meander shape, the second actuator portion 19A has a piezoelectric vibration portion 26A, 27A, 28A, 29A, and the second actuator portion 19B has a piezoelectric vibration portion 26B, Each has a meander shape composed of 27B, 28B, and 29B.

  Here, the configuration of the meander-shaped actuator structure will be described in detail by taking the first actuator portion 16A as an example.

  For example, as shown in FIG. 1, the piezoelectric vibrating portions 22A, 23A, 24A and 25A are all arranged in a direction substantially parallel to the piezoelectric vibrating portion 21A, and one end of the piezoelectric vibrating portion 21A is the piezoelectric vibrating portion 22A. One end, the other end of the piezoelectric vibrating portion 22A is one end of the piezoelectric vibrating portion 23A, the other end of the piezoelectric vibrating portion 23A is one end of the piezoelectric vibrating portion 24A, and the other end of the piezoelectric vibrating portion 24A is one end of the piezoelectric vibrating portion 25A. The first actuator portion 16A having a meander shape is configured by being connected. The first actuator portion 16A having such a shape is an example, and can be designed by appropriately selecting a shape necessary for a desired swing angle. Therefore, the function can be exhibited by arranging at least a plurality of piezoelectric vibrating portions in a meander shape.

  As shown in FIG. 2, the cross section of the first actuator portion 16 </ b> A is configured as a thin film laminate including a lower electrode layer 32, a piezoelectric layer 33, an upper electrode layer 34, and a constraining layer 35. The basic configuration of this cross-sectional structure is the same in the first actuator portions 16A and 16B, the second actuator portions 19A and 19B, and the second frame 17.

  Further, since it is preferable to vibrate only in the longitudinal direction of the piezoelectric vibrating portions 21A, 22A, 23A, 24A and 25A arranged in a substantially parallel direction, the piezoelectric layer 33 is removed so as not to be displaced at each bent joint portion. Alternatively, by designing an electrode pattern such that no potential is applied to the piezoelectric layer 33, it is possible to realize a piezoelectric actuator element that is displaced with high accuracy only in one axial direction. Specifically, it is preferable that the electrode area of the upper electrode layer 34 is minimized in the bent joint portion to form an electrode pattern for electrical connection.

  Furthermore, the constraining layer 35 preferably has rigidity, and the constraining layer 35 is indispensable when considering vibration characteristics and mechanical strength, and the constraining layer 35 is a main part of the beam structure.

  The first frame body 14 is preferably made of a material having excellent rigidity and workability, such as silicon. The first frame body 14 joins and supports one end of the first actuator portions 16A and 16B. Yes. A part of the laminate composed of the lower electrode layer 32, the piezoelectric layer 33, the upper electrode layer 34, and the constraining layer 35 is joined to the upper surface of the frame portion of the first frame 14, but the first frame body The laminated body joined to the outer periphery of the frame 14 is integrated with the first frame 14 and acts. As a result, one end serving as a vibration support portion of the first actuator portions 16A and 16B can be firmly fixed to the first frame body 14.

  The laminated body may be formed only at least on the support portion joined to the first frame body 14.

  In addition, since the first actuator portions 16A and 16B can be formed using a photolithographic technique, each meander-shaped gap formed of a thin film stack can be formed with a minimum dimension, and a silicon wafer or the like can be formed. Can be used as a substrate, so that a structure with excellent productivity can be obtained.

  The piezoelectric vibrating portions 22B, 23B, 24B, and 25B are all arranged in a substantially parallel direction with respect to the piezoelectric vibrating portion 21B. One end of the piezoelectric vibrating portion 21B is one end of the piezoelectric vibrating portion 22B and the piezoelectric vibrating portion 22B. The other end is connected to and supported by one end of the piezoelectric vibrating portion 23B, the other end of the piezoelectric vibrating portion 23B is connected to one end of the piezoelectric vibrating portion 24B, and the other end of the piezoelectric vibrating portion 24B is connected to and supported by one end of the piezoelectric vibrating portion 25B.

  Further, the piezoelectric vibrating portions 26A, 27A, 28A, 29A constituting the second actuator portion 19A are all arranged in a direction substantially perpendicular to the piezoelectric vibrating portion 21A of the first actuator portion 16A, and the piezoelectric vibrating portion 26A. One end of the piezoelectric vibrating portion 27A, the other end of the piezoelectric vibrating portion 27A is one end of the piezoelectric vibrating portion 28A, the other end of the piezoelectric vibrating portion 28A is one end of the piezoelectric vibrating portion 29A, and the other end of the piezoelectric vibrating portion 29A. Is connected to one end of the optical reflecting portion 20 to constitute a second actuator portion 19A.

  Similarly, the piezoelectric vibrating portions 26B, 27B, 28B, and 29B are all disposed substantially perpendicular to the piezoelectric vibrating portion 21B. One end of the piezoelectric vibrating portion 26B is one end of the piezoelectric vibrating portion 27B and the piezoelectric vibrating portion 27B. The other end of the piezoelectric vibration unit 28B is connected to one end of the piezoelectric vibration unit 28B, the other end of the piezoelectric vibration unit 28B is connected to one end of the piezoelectric vibration unit 29B, and the other end of the piezoelectric vibration unit 29B is connected to one end of the optical reflection unit 20. Part 19B is configured.

  3 is an enlarged perspective view of a portion B in FIG. 1. As shown in FIG. 3, the piezoelectric vibrating portions 21A, 22A and 23A have an electrode pattern 30 acting as an upper electrode on the upper surface thereof by using a photolithography technique or the like. At the same time, an electrode pattern 31 for wiring to the upper electrode of the second actuator portion 19A is formed and electrically connected to the terminal electrodes 30A and 31A shown in FIG. The terminal electrodes 30A, 31A, and 32A indicate connection terminals.

  The piezoelectric vibrating portions 21A, 22A, and 23A have a common constraining layer 35 formed on the uppermost surface as shown in the cross-sectional view of FIG. The laminated body formed in order of the body layer 33 and the lower electrode layer 32 is comprised. The lower electrode 32 is electrically connected to the electrode 32A shown in FIG.

  Next, the operating principle of the optical reflecting element in the first embodiment will be described.

  First, an AC voltage is applied to each of the terminal electrodes 30A and 31A shown in FIG. 1, and the terminal electrode 32A is grounded.

  Then, as shown in FIG. 4, at a certain point in time, the piezoelectric vibrating portion 21A has a convex surface downward, the piezoelectric vibrating portion 22A has a convex surface upward, the piezoelectric vibrating portion 23A has a downward convex surface, and the piezoelectric vibrating portion 24A has an upward surface. The convex surface is curved so that the piezoelectric vibrating portion 25A has a convex surface downward and the piezoelectric vibrating portion 26A has a convex surface upward. Since an AC voltage is applied to the electrode patterns 30 and 31, the polarity is reversed after the unit time has elapsed, and accordingly, the piezoelectric vibrating portions 21A, 22A, 23A, 24A, 25A, and 26A are as shown in FIG. It curves in the direction opposite to FIG.

  Similarly, in the first and second actuator portions 16A, 16B, 19A, and 19B, the bending directions of the adjacent piezoelectric vibrating portions are staggered, and the bending direction is reversed each time the polarity of the AC voltage is reversed. Yes.

  With such a configuration, the optical reflecting element according to the first embodiment is a meander-shaped piezoelectric vibration element in the first and second actuator portions 16A, 16B, 19A, and 19B. Since the bending directions of the vibration parts of the vibration parts are staggered, the bending angle is added by the number of vibration parts, and as a result, even if the length of the vibration part is reduced, bending at a predetermined angle is performed. A small optical reflection element 20 that can be obtained in the first actuator portions 16A and 16B and the second actuator portions 19A and 19B and can be swung in two axes can be realized.

  The first actuator portions 16A and 16B and the second actuator portions 19A and 19B are thin film laminates including the constraining layer 35 as a supporting base and the lower electrode 32, the piezoelectric layer 33, and the upper electrode layer 34. Therefore, an extremely thin vibration part can be formed, and thus an actuator structure that can be driven at a low voltage and has a large displacement can be realized. As a result, it is possible to provide an optical reflecting element that is excellent in productivity and can be miniaturized.

  Next, a method for manufacturing the optical reflecting element in the first embodiment will be described with reference to the drawings.

  FIG. 6A to FIG. 6E are cross-sectional views of steps for explaining the method of manufacturing the optical reflecting element in the first embodiment.

  First, as shown in FIG. 6A, a silicon substrate 36 is prepared, and a lower electrode layer 32a made of a platinum electrode is formed thereon using a thin film process such as sputtering or vapor deposition. At this time, the silicon substrate 36 may be thick. As a result, a silicon substrate 36 having a large wafer shape can be used, and since there is little warpage or the like, a highly accurate optical reflection device can be efficiently manufactured.

  Thereafter, a piezoelectric layer 33a is formed on the lower electrode layer 32a by a sputtering method using a piezoelectric material such as lead zirconate titanate (PZT). At this time, an oxide dielectric containing Pb and Ti is preferably used as the orientation control layer between the piezoelectric layer 33a and the lower electrode layer 32a, and an orientation control layer made of PLMT is more preferably formed. Thereby, the crystal orientation of the piezoelectric layer 33a is further increased, and a piezoelectric actuator element having excellent piezoelectric characteristics can be realized.

  Next, an upper electrode layer 34a made of titanium / gold is formed on the piezoelectric layer 33a. At this time, titanium under the gold electrode is formed in order to increase the adhesion with the PZT thin film, and a metal such as chromium can be used in addition to titanium. As a result, a thin layered product with improved adhesion strength can be formed because it has excellent adhesion with the piezoelectric layer 33a and a strong diffusion layer with the gold electrode. At this time, the platinum electrode is 0.2 μm thick, the PZT thin film is 3.5 μm, the titanium electrode is 0.01 μm, and the gold electrode is 0.3 μm.

  Next, as shown in FIG. 6B, a patterned upper electrode layer 34 is formed by etching the upper electrode layer 34a using a photolithography technique. At this time, a predetermined electrode pattern was formed using an etching solution comprising an iodine / potassium iodide mixed solution, ammonium hydroxide, and hydrogen peroxide mixed solution as an etching solution.

  Next, as shown in FIG. 6C, a silicon dioxide thin film is formed by CVD using ethyl silicate (TEOS) as the constraining layer 35a. The constraining layer 35a functions as an important support base material for the vibration part. As a material used for the constraining layer 35a, silicon oxide containing silicon dioxide, silicon nitride is used from the viewpoint of strength and reliability. An inorganic oxide having insulating properties such as the above is preferable. In consideration of productivity, it is preferable to use the silicon oxide or silicon nitride.

  Moreover, as a manufacturing method of this constrained layer 35a, a thin film forming technique such as a sputtering method, a CVD method, a sol-gel method or an electroless plating method can be used.

  This constraining layer 35a is formed as a support base material for the vibration part, and the thickness of the constraining layer 35 patterned in the subsequent process by etching can be greatly exerted when the thickness is 2 μm or more.

  In consideration of the characteristics of the piezoelectric layer 33, the constraining layer 35 is preferably a stacked body in the order shown in FIG.

  Next, as shown in FIG. 6D, the lower electrode layer 32a, the piezoelectric layer 33a, and the constraining layer 35a are etched. As an etching method used for this, any one of a dry etching method and a wet etching method or a combination of these methods can be used.

For example, in the case of a dry etching method, a fluorocarbon-based etching gas or SF ₆ gas can be used. First, the constraining layer 35a is etched by dry etching to form a patterned constraining layer 35. As an etching gas at that time, a fluorocarbon-based etching gas can be used. Thereafter, the piezoelectric layer 33a is subjected to wet etching using an etching solution made of a mixed solution of hydrofluoric acid, nitric acid, acetic acid and hydrogen peroxide, thereby forming a patterned piezoelectric layer 33. Thereafter, the patterned lower electrode layer 32 is formed by etching the lower electrode layer 32a by dry etching, and the gaps 15 and 18 are formed, whereby a meander-shaped vibrating portion can be formed.

In the case of dry etching, it is preferable to perform etching more linearly using SF ₆ gas that promotes etching and C ₄ F ₈ gas that suppresses etching. In the etching, a mixed gas using the gas can be used, or an etching method by performing the dry etching by alternately switching the gas can be performed. It is possible to selectively etch.

Next, as shown in FIG. 6E, the recess 13 is formed by dry etching the silicon substrate 36 using XeF ₂ gas. As a result, the silicon existing on the lower surfaces of the first actuator portions 16A and 16B, the second frame 17, and the second actuator portions 19A and 19B are all removed to form a laminated body composed of thin films. A vibration driving unit of the optical reflecting unit 20 including the first actuator units 16A and 16B, the second frame unit 17, and the second actuator units 19A and 19B supported by the frame body 14 is formed.

  However, the lower electrode layer 32, the piezoelectric layer 33, the upper electrode layer 34, and the constraining layer 35 existing on the outer peripheral portion of the first frame body 14 can make the bonding to the first frame body 14 more complete. , Formed as a part of the first frame 14.

  Through such a process, the optical reflecting element shown in FIG. 1 can be manufactured. By adopting such a configuration, it is possible to produce a vibration support point as a vibrator of the first actuator parts 16A and 16B with high accuracy, and to provide an optical reflection element having a highly reliable vibration drive part. Can be produced.

  The optical reflecting portion 20 can use a gold electrode or the like formed as the upper electrode layer 34 on the lower surface side of the constraining layer 35 as a reflecting film. Furthermore, a new reflective film may be formed on the constraining layer 35. As the reflective film, it is preferable to use a metal film having a high reflectance.

  The optical reflecting element of the present invention can realize a configuration in which a predetermined driving motion is caused to the optical reflecting portion by applying a small driving voltage to the piezoelectric diaphragm, and is useful in various electronic devices such as a projector and a laser printer. is there.

The perspective view of the optical reflective element in Embodiment 1 of this invention Sectional view in the AA part of FIG. Part B enlarged perspective view of FIG. Side view showing the operating principle of the optical reflective element Side view Sectional drawing of the process for demonstrating the manufacturing method Top view of conventional optical reflector Schematic diagram of application example of conventional optical reflection element

Explanation of symbols

13 Concave part 14 First frame 15 Gap 16A, 16B First actuator part 17 Second frame 18 Gap 19A, 19B Second actuator part 20 Optical reflection part 21A, 22A, 23A, 24A, 25A, 26A, 27A, 28A, 29A Piezoelectric vibration part 21B, 22B, 23B, 24B, 25B, 26B, 27B, 28B, 29B Piezoelectric vibration part 30, 31 Electrode pattern 30A, 30B, 31A, 32A Terminal electrode 32 Lower electrode layer 33 Piezoelectric layer 34 Upper electrode layer 35 Constrained layer 36 Silicon substrate

Claims (8)

A first frame having a recess;
A meander-shaped first actuator portion supported at one end by the first frame;
A second frame supported by the other end of the first actuator part;
A meander-shaped second actuator part, one end of which is supported by the second frame,
An optical reflecting portion supported at an end of the second actuator portion;
The first actuator part has at least a first piezoelectric vibration part in the longitudinal direction;
The second actuator part has at least a second piezoelectric vibration part in the longitudinal direction,
An optical reflecting element configured such that the drive axes of the first actuator section and the second actuator section are orthogonal to each other. The optical reflection element according to claim 1, wherein the first piezoelectric vibration part and the second piezoelectric vibration part are a laminated body including a lower electrode layer, a piezoelectric layer, an upper electrode layer, and a constraining layer. The optical reflective element according to claim 1, wherein the upper electrode layer of the first actuator portion has an electrode pattern connected to the upper electrode layer of the second actuator portion. The optical reflective element according to claim 1, wherein the main component of the first frame is silicon. The optical reflection element according to claim 1, wherein the main component of the first frame is glass or quartz. The optical reflective element according to claim 1, wherein the constraining layer contains silicon oxide or silicon nitride as a main component. The optical reflecting element according to claim 6, wherein the thickness of the constraining layer is 2 μm or more. The optical reflective element according to claim 1, wherein the depth of the concave portion of the first frame is 200 μm or more.

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