JP2009223226A - Polymer mems actuator, optical switch, and method for manufacturing polymer mems actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hardly cause damage and failure and to reduce manufacturing processes and man-hours by achieving an actuator with a simple structure using a polymeric material. <P>SOLUTION: A polymer MEMS (microelectromechanical system) actuator 10 with an electrically drivable micro mechanical structure formed on a silicon substrate 11 using the polymeric material includes: a polymer movable part 12 of longitudinal plate shape formed of the polymeric material; a metal heater 13 formed in almost the same shape as the polymer movable part 12 and stuck to the upper face of the polymer movable part 12; and a mirror 14 fixed to the tip part of the metal heater 13 and the polymer movable part 12 and having mirror finished surfaces 14a for reflecting light, on the front and rear faces. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polymer MEMS actuator, an optical switch, and a method for manufacturing a polymer MEMS actuator in which a MEMS (microelectromechanical system), which is a micromechanical structure that can be electrically driven, is formed on a silicon substrate using a polymer material.

  MEMS (Micro Electro Mechanical System) is an ultra-compact system (micro-mechanical structure) that combines electricity and machine, and is manufactured by a microfabrication technology that applies semiconductor (LSI) manufacturing technology. While LSIs integrate electronic circuits on a silicon substrate, MEMS is a technique for creating a micromechanical structure on a silicon substrate. This MEMS technology is a culmination of microfabrication / combination technologies, and contributes to the miniaturization of existing products in every field of the world. Therefore, it is said that there are countless potentially applicable products.

  The MEMS technology is used, for example, when an optical switch is formed in an optical communication device in which a plurality of optical waveguides are formed in a matrix by an insulating material such as a polymer on a silicon substrate. The optical switch drives a mirror so as to perform control to change the transmission path by passing or reflecting light transmitted to each optical waveguide, and is realized by a MEMS actuator. Recently, as disclosed in Patent Document 1, there is a technique for forming a MEMS actuator with an insulating material such as a polymer on a silicon substrate.

  This includes a fixed comb fixed on the substrate, a movable comb separated from the substrate, a post fixed on the substrate, and a movable comb that is connected to the post while being separated from the substrate. A MEMS comb actuator comprising a supporting spring. Further, the fixed comb, the movable comb, the post, and the spring are formed of an insulating material layer formed on the substrate, and conductive metal coating films are formed on the surfaces of the fixed comb and the movable comb, respectively.

And a step of providing a substrate, a step of forming an insulating material layer of a predetermined thickness made of silica or polymer on the substrate, a selective comb and a movable comb on the insulating material layer by selectively etching the insulating material layer and the substrate. Forming a post and a spring, and forming a conductive metal coating film on the surface of each of the stationary comb and the movable comb, respectively. In addition, the fixed comb and the movable comb are both comb-like, and are provided with an uneven portion of the teeth facing each other so that the convex portion enters the concave portion through a gap.
JP 2005-519784 A

  By the way, in Patent Document 1, the fixed comb and the movable comb of the MEMS actuator are formed of an insulating material layer, and both of the shapes are comb-toothed, and the uneven portions of the teeth are mutually connected, and the protruding portion is in the recessed portion through the gap. Due to the intricately opposed arrangement, the structure is complex and the insulating material layer must be etched to form fixed and movable combs and posts and springs. In other words, because the actuator structure is complicated, it is easy to break or break down, and the complicated structure must be formed by etching the insulating material layer, which increases the manufacturing process and man-hours. .

  In order to solve the above-mentioned problems, the present invention aims to make it difficult to break or break down by realizing an actuator with a simple structure using a polymer material, and to reduce its manufacturing process and man-hours. .

  In order to achieve the above object, the inventor uses a polymer material on a substrate, and has a simple cantilever structure in which a longitudinal end is fixed and the other end is movable in a direction perpendicular to the substrate. A polymer MEMS actuator having a structure similar to a bimetal was prepared.

  Specifically, a polymer MEMS actuator formed by forming a MEMS, which is a micromechanical structure that can be electrically driven by a polymer material, on a substrate, one end of which is fixed on the substrate, and the fixed one end A polymer movable portion made of a long plate-like polymer material, wherein a tip portion facing in the longitudinal direction is movable in a direction perpendicular to the upper surface of the substrate above the substrate, and the polymer A metal heater that has substantially the same shape as the movable part and is fixed to one surface of the polymer movable part, has a linear expansion coefficient different from that of the polymer movable part, and generates heat when energized, and the tip of the polymer movable part or the metal heater A polymer MEMS actuator comprising a mirror that reflects light fixed to the unit.

  According to this configuration, since the polymer MEMS actuator is realized with a structure similar to a simple bimetal using a polymer material, it is less likely to be damaged or broken compared to a conventional complex structure.

  Specifically, optical waveguides that transmit light by a polymer material are formed on a substrate in a matrix shape that intersects vertically and horizontally, and light transmitted to these optical waveguides is allowed to pass or reflect at the intersecting positions. In an optical switch that performs switching control for changing a transmission path, the polymer MEMS actuator according to claim 1 is disposed at the intersection, and the presence or absence of energization of the metal heater of the polymer MEMS actuator is controlled. An optical switch characterized by performing switching control.

  According to this configuration, since the polymer MEMS actuator can also be formed of a polymer material, it can be easily formed and disposed at the intersection of the optical waveguides. Even if the number of vertical and horizontal optical waveguides is large, the polymer MEMS can be provided. The actuator can be integrated.

  More specifically, a method for manufacturing a polymer MEMS actuator for forming a MEMS, which is a micromechanical structure that can be electrically driven by a polymer material, on a substrate, the resist layer being formed on the substrate, and then exposure and development. The resist layer is formed into a convex shape by the above, a sacrificial layer forming step using the resist layer as a sacrificial layer, and a negative polymer material is applied onto the substrate including the sacrificial layer formed in the sacrificial layer forming step to form a polymer Forming a layer, and forming the polymer layer by exposure and development into a shape extending in a longitudinal shape from a part on the substrate to the upper surface of the sacrificial layer, and using this as a polymer movable part; A metal film is formed on the substrate including the polymer movable part formed in the movable part forming step, and the metal film is etched by using a resist pattern film. A metal heater forming step using the metal heater as a metal heater, and a mirror surface that reflects light to the tip of the polymer moving portion after the metal heater forming step. Is a mirror surface forming step of forming a polymer surface, and a removal step of removing the sacrificial layer after the mirror surface is formed in the mirror surface forming step.

  According to this method, the sacrificial layer below the polymer movable part is removed, so that only one end of the polymer movable part is fixed on the substrate, that is, a cantilever structure is formed. It is possible to form an actuator that is opposed to the one end portion in the longitudinal direction and in which a tip portion having a mirror surface is movable in a direction perpendicular to the upper surface of the substrate above the substrate.

  In the manufacturing method of the polymer MEMS actuator of the present invention, the metal film formed in the metal heater forming step has a linear expansion coefficient different from that of the polymer movable portion formed in the movable portion forming step, and generates heat when energized. Is preferably used.

  According to this method, a metal film having a different linear expansion coefficient from the polymer moving part is fixed to the polymer movable part and has a structure similar to a bimetal. Therefore, if the metal film is energized to generate heat, both are heated. The one with a larger coefficient of linear expansion stretches physically longer than the one with a smaller coefficient of linear expansion. Therefore, it bends (moves) from the larger linear expansion coefficient to the smaller one.

  According to the present invention, a polymer MEMS actuator, an optical switch, and a polymer MEMS actuator that make it difficult to break or break down by realizing the actuator with a simple structure using a polymer material, and reduce the manufacturing process and man-hours of the actuator. A manufacturing method can be provided.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

  FIG. 1 is a cross-sectional view showing a configuration of a polymer MEMS actuator according to an embodiment of the present invention. The polymer MEMS actuator 10 of the present embodiment is configured to have a MEMS that is a micromechanical structure that can be electrically driven by a polymer material on a silicon substrate 11. The MEMS includes a polymer movable portion 12 made of a long plate-shaped polymer material, a metal heater 13 having substantially the same shape as the polymer movable portion 12 and fixed to the upper surface thereof, and the polymer movable portion 12 and the metal heater 13. And a mirror 14 having front and back mirror surfaces 14a that reflect light fixed to the front end portion.

  More specifically, the polymer movable portion 12 has one end portion fixed to the upper surface of the silicon substrate 11, and a tip portion facing the fixed one end portion in the longitudinal direction above the silicon substrate 11. 11 is arranged in a cantilever structure that is movable in a vertical direction (hereinafter also referred to as an up-down direction) with respect to the upper surface of 11. Moreover, the thickness of the polymer movable part 12 shall be 5-30 micrometers in this example.

The metal heater 13 is made of chromium (Cr) having a linear expansion coefficient of about 10 ⁻⁵ and a linear expansion coefficient smaller than that of the polymer material of about 10 ⁻⁴ forming the polymer movable portion 12 and generating heat when energized. In this example, the film thickness of chromium is assumed to be 50 to 300 nm. It is assumed that the height of the mirror 14 is 10 to 200 μm.

  That is, the polymer movable portion 12 and the metal heater 13 have a structure similar to a bimetal, and if the metal heater 13 is energized to generate heat, both are heated and the polymer movable portion 12 having a large linear expansion coefficient is small. It extends physically longer than the metal heater 13. As a result, a force is applied from the polymer movable portion 12 to the metal heater 13 to bend and move in the direction indicated by the arrow Y1, and the mirror 14 also moves with this movement. On the other hand, if the energization is released, the metal heater 13 and the polymer movable portion 12 are cooled, so both return to the original position, and the mirror 14 necessarily returns to the original position.

  Next, a method for manufacturing such a polymer MEMS actuator 10 will be described with reference to FIGS.

  First, in the sacrificial layer forming process shown in FIGS. 2A to 2C, as shown in FIG. 2A, a silicon oxide material is applied to the upper surface of the silicon substrate 11 to a predetermined thickness to thereby form a positive type photo. A resist layer 17-0 is formed. Next, as shown in (b), a photomask 18 having a predetermined mask pattern portion 18a is arranged above the photoresist layer 17-0, and ultraviolet rays are applied from above the photomask 18 as shown by a plurality of arrows. Irradiate. As a result, portions other than the mask pattern portion 18a are exposed to ultraviolet rays for exposure. Then, as shown in (c), when development is performed, the portions other than the ultraviolet-irradiated portion of the photoresist layer 17-0 remain convex. This becomes the sacrificial layer 17.

  Next, in the movable part forming step shown in FIGS. 3D to 3F, as shown in FIG. 3D, a negative polymer material (SU8: chemical amplification) is formed on the entire upper surface of the silicon substrate 11 including the sacrificial layer 17. Type negative resist) is applied to a predetermined thickness to form a polymer layer 12-0. Next, as shown in (e), a photomask 21 having a predetermined mask pattern portion 21a is arranged above the polymer layer 12-0, and ultraviolet rays are emitted from above the photomask 21 as shown by a plurality of arrows. Irradiate. As a result, the portions other than the mask pattern portion 21a are irradiated with ultraviolet rays to be exposed. And as shown in (f), when it develops, since it is a negative type, the ultraviolet irradiation part of the polymer layer 12-0 remains. That is, it remains in a shape extending from the part of the silicon substrate 11 to the upper surface of the sacrificial layer 17 in a longitudinal shape. This becomes the polymer movable portion 12.

  Next, in the metal heater forming step shown in FIGS. 4G to 4J, as shown in FIG. 4G, chromium is vapor-deposited on the silicon substrate 11 including the polymer movable portion 12 to form the metal film 13-0. Form. Next, as shown in (h), a silicon oxide material is applied on the metal film 13-0 to a predetermined thickness to form a resist layer 23-0, and as shown in (i), the resist layer 23-0 is exposed and developed to be patterned into a predetermined shape. The resist pattern film 23 thus formed has a substantially similar shape with one end side slightly longer than the polymer movable portion 12 below the metal film 13-0. Next, as shown in (j), after performing metal etching using the resist pattern film 23 and then removing the resist pattern film 23, the metal heater 13 fixed to the polymer movable portion 12 in substantially the same shape as this. Remains.

  Next, in the mirror surface forming step shown in FIGS. 5 (k) to 5 (o), as shown in (k), a mirror layer 14-0 is formed on the entire surface after the metal heater 13 is formed. A photomask 25 having a mirror pattern mask pattern portion 25a is disposed on the mirror layer 14-0, and ultraviolet rays are irradiated from above the photomask 25 as indicated by a plurality of arrows. As a result, portions other than the mask pattern portion 25a are exposed to ultraviolet rays for exposure. Next, as shown in (m), development is performed to form a mirror structure 14b serving as a base of the mirror. In (n), in order to selectively form a metal film on the formed mirror structure 14b, the entire surface after the formation of the mirror structure 14b is covered with a masking material 15, and in (o), only the portion of the mirror structure 14b is covered. Exposure is performed using a photomask 25 for removing the masking material 15.

  Next, in the mirror surface forming step and the removing step shown in FIGS. 6 (p) to (s), as shown in (p), the masking material 15 in the exposed portion is removed by development to thereby create a mirror structure. Only the mask 14b is exposed. Next, as shown in (q), after a metal film 14a-0 serving as a reflective film is formed on the entire surface of the substrate where the mirror structure 14b is exposed, a metal film other than the mirror structure 14b as shown in (r). The mirror surface 14a is formed by removing 14a-0. Thereby, the mirror 14 having the mirror surface 14a is formed. Finally, as shown in (s), the sacrificial layer 17 is removed.

  According to the method for manufacturing the polymer MEMS actuator of this embodiment, finally, the sacrificial layer 17 below the polymer movable part 12 is removed, so that only one end of the polymer movable part 12 is formed on the silicon substrate 11. It is in a fixed state, that is, a cantilever structure. That is, the polymer MEMS actuator 10 that is opposed to the fixed one end in the longitudinal direction and whose tip formed with the mirror 14 is movable in a direction perpendicular to the upper surface of the substrate above the silicon substrate 11 is formed. be able to.

  Since this polymer MEMS actuator 10 has a structure similar to a simple bimetal in which the polymer movable portion 12 and the metal heater 13 are fixed, the structure is complicated as in the conventional actuator, so that the polymer MEMS actuator 10 is easily damaged or failed. The problem of the manufacturing process and the increase in man-hours caused by forming a complicated structure by etching the insulating material layer is eliminated.

  In other words, according to the polymer MEMS actuator 10 of the present embodiment, since the actuator can be realized with a simple structure using a polymer material, it is difficult to break or break down, and the manufacturing process and man-hours are reduced. can do.

  The polymer MEMS actuator 10 described above operates upward when energization of the metal heater 13 fixed to the polymer movable portion 12 is turned on, and operates in the reverse direction when off, as indicated by an arrow Y1 in FIG. The structure returned to the original position. However, if the positions of the metal heater 13 and the polymer movable portion 12 are manufactured in reverse, it can be structured such that it operates from top to bottom when energized and operates in the reverse direction when not energized and returns to its original position.

  Next, as shown in FIG. 7, an optical switch 30 using such a polymer MEMS actuator 10 will be described.

  The optical switch 30 is formed on a silicon substrate 31 with a polymer material in a matrix shape in which optical waveguides 32 and 33 for transmitting light intersect vertically and horizontally. More specifically, four optical waveguides 32 are formed between the end surfaces in the vertical direction of the silicon substrate 31 at a constant adjacent interval, and four optical waveguides 33 are formed between the end surfaces in the horizontal direction at a constant adjacent interval. Each of the optical waveguides 32 and 33 is arranged in a matrix that intersects in an orthogonal state. However, it is assumed that a perfluorinated polyimide having a low optical transmission loss is used for the polymer material forming the optical waveguides 32 and 33.

  A groove 34 is formed at an angle of 45 degrees with respect to the optical waveguides 32 and 33 at the intersecting positions of the vertical and horizontal optical waveguides 32 and 33, and the mirror 14 is movably inserted in the groove 34. A polymer MEMS actuator 10 is disposed. The groove 34 is formed in a state in which both the vertical and horizontal optical waveguides 32 and 33 are cut at a predetermined gap. However, the gap of the groove 34 has a dimension that does not affect the optical transmission of the optical waveguides 32 and 33 at all.

  The mirror 14 inserted in the groove 34 is controlled by the switching control means (not shown) of the optical switch 30 to control whether the metal heater 13 is energized or not energized, so that the arrow Y1 in FIG. As shown in FIG. 2, the state moves upward and is positioned upward, and returns to the original position when not energized. Further, when the metal heater 13 is not energized, the mirror 14 is in a reflection position where the transmission light of each of the optical waveguides 32 and 33 is reflected by the groove 34. When energized, the mirror 14 moves upward and becomes a passing position where the transmission light of each of the optical waveguides 32 and 33 passes through the groove 34. Such switching control is performed on each polymer MEMS actuator 10 disposed in the optical switch 30.

  Next, the operation of the optical switch 30 will be described. For example, it is assumed that the metal heater 13 of one polymer MEMS actuator 10 in the upper right corner of each polymer MEMS actuator 10 in FIG. 7 is not energized, and thus the mirror 14 is in the reflection position. In this case, as indicated by an arrow Y2, when light is input to the vertical optical waveguide 32, the light is transmitted through the optical waveguide 32, reflected by the mirror 14 by 90 degrees, and directed to the horizontal optical waveguide 33. The transmission route is changed and output in the direction indicated by the arrow Y3.

  On the other hand, it is assumed that the metal heater 13 of only one polymer MEMS actuator 10 in the upper right corner is energized, whereby the mirror 14 is in the passing position. In this case, as indicated by the arrow Y2, the light input to the vertical optical waveguide 32 passes through the first groove 34 and is transmitted through the next vertical optical waveguide 32. The transmitted light is reflected 90 degrees by the mirror 14 of the polymer MEMS actuator 10 immediately below the upper right corner, changes the transmission route to the horizontal optical waveguide 33, and is output in the direction indicated by the arrow Y4.

  Thus, in the optical switch 30, the polymer MEMS actuator 10 is disposed at the intersection of the vertical and horizontal optical waveguides 32 and 33 so that switching control for changing the optical transmission route can be performed. In the optical switch 30, vertical and horizontal optical waveguides 32 and 33 are formed in a matrix shape with a polymer material on the silicon substrate 11. However, since the polymer MEMS actuator 10 can also be formed with a polymer material, the crossing position of the optical waveguides 32 and 33. In addition, the polymer MEMS actuator 10 can be integrated even if the number of the vertical and horizontal optical waveguides 32 and 33 is large.

  In the above description, when the metal heater 13 is not energized, the mirror 14 is moved to the reflection position, and when energized, the transmission light is in the passing state. When the mirror 14 is in the passing position of each of the optical waveguides 32 and 33 and the transmission light is in a passing state, when energized, the mirror 14 may be moved to the reflection position to make the transmission light in a reflecting state. In the above-described embodiment, it is assumed that the optical waveguides 32 and 33 intersect at right angles, but may intersect at an angle. In this case, the transmitted light is reflected at an intersecting angle.

  The polymer MEMS actuator, the optical switch, and the manufacturing method of the polymer MEMS actuator according to the present invention include an acceleration sensor that detects acceleration by distorting a structure due to acceleration and changing capacitance, and a thin film that bends due to a pressure difference. A pressure sensor that detects pressure by detecting the change in capacitance, a switch that controls the presence or absence of reflection of incident light with a movable mirror, an optical MEMS scanner used in sensors and displays, and many micromirrors The present invention can be applied to a DMD (digital micro display) which is a display element arranged in a plane.

It is sectional drawing which shows the structure of the polymer MEMS actuator which concerns on embodiment of this invention. It is explanatory drawing of the sacrifice layer formation process by the manufacturing method of the polymer MEMS actuator which concerns on embodiment of this invention. It is explanatory drawing of the movable part formation process by the manufacturing method of the polymer MEMS actuator which concerns on embodiment of this invention. It is explanatory drawing of the metal heater formation process by the manufacturing method of the polymer MEMS actuator which concerns on embodiment of this invention. It is explanatory drawing of the mirror surface formation process by the manufacturing method of the polymer MEMS actuator which concerns on embodiment of this invention. It is explanatory drawing of the mirror surface formation process and removal process by the manufacturing method of the polymer MEMS actuator which concerns on embodiment of this invention. It is a top view which shows the structure of the optical switch using the polymer MEMS actuator which concerns on embodiment of this invention.

Explanation of symbols

10: Polymer MEMS actuator 11, 31: Silicon substrate 12: Polymer movable part 12-0: Polymer layer 13: Metal heater 13-0: Metal film 14: Mirror 14a: Mirror surface 14a-0: Metal film 14b: Mirror structure 14- 0: Mirror layer 15: Masking material 17: Sacrificial layer 17-0: Photoresist layer (positive type)
18, 21, 25: Photomasks 18a, 21a, 25a: Mask pattern portion 23: Resist pattern film 23-0: Resist layer 30: Optical switch 32, 33: Optical waveguide 34: Groove

Claims (4)

A polymer MEMS actuator formed on a substrate by forming MEMS, which is a micromechanical structure that can be electrically driven by a polymer material,
One end portion is fixed on the substrate, and a tip portion facing the fixed one end portion in the longitudinal direction is arranged to be movable in a direction perpendicular to the upper surface of the substrate above the substrate. A movable polymer portion made of a long plate-shaped polymer material,
A metal heater that has substantially the same shape as the polymer movable part and is fixed to one surface of the polymer movable part, and has a linear expansion coefficient different from that of the polymer movable part and generates heat when energized;
A mirror that reflects light fixed to a tip of the polymer movable part or the metal heater;
A polymer MEMS actuator comprising: Optical waveguides that transmit light by a polymer material on the substrate are formed in a matrix shape that intersects vertically and horizontally, and switching control that changes the transmission path by passing or reflecting the light transmitted to these optical waveguides at the intersecting position is performed. In the optical switch to perform
An optical switch, wherein the polymer MEMS actuator according to claim 1 is disposed at the intersection position, and the switching control is performed by controlling whether or not the metal heater of the polymer MEMS actuator is energized. A method of manufacturing a polymer MEMS actuator for forming a MEMS, which is a micromechanical structure that can be electrically driven by a polymer material on a substrate,
After forming a resist layer on the substrate, the resist layer is formed into a convex shape by exposure and development, and a sacrificial layer forming step using this as a sacrificial layer;
A negative polymer material is applied on the substrate including the sacrificial layer formed in the sacrificial layer forming step to form a polymer layer, and the polymer layer is exposed and developed to expose the sacrificial portion from a part on the substrate. A movable part forming step that is formed into a shape extending in a longitudinal shape over the upper surface of the layer, and this is a polymer movable part,
A shape in which a metal film is formed on the substrate including the polymer movable part formed in the movable part forming step, and the metal film is fixed to the polymer movable part in substantially the same shape by etching using a resist pattern film. Forming a metal heater, and using this as a metal heater,
After passing through the metal heater forming step, a mirror surface forming step of forming a mirror surface that reflects light on the tip of the polymer movable portion;
A removal step of removing the sacrificial layer after the mirror surface formation in the mirror surface formation step;
The manufacturing method of the polymer MEMS actuator provided with these in order.   The metal film formed in the metal heater forming step is made of a metal material that has a linear expansion coefficient different from that of the polymer movable portion formed in the movable portion forming step and generates heat when energized. Item 4. A method for producing a polymer MEMS actuator according to Item 3.

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