JPH0786002A - Method of manufacturing actuator - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of stably manufacturing an actuator having very thin substrate at low cost. CONSTITUTION:A structure manufactured by respective steps including the forming step of an aperture part 14 is provided with a semiconductor substrate 12 leaving a framed shape intact. At this time, a flexible thin film 16 extends over the whole surface of the semiconductor substrate 12 in such a way as to cover the aperture part 14 wherein an actuator 10 is constituted. This actuator 10 is composed of a flexible thin film 16, shape memory alloys 20 provided on the surface of the thin film 16 and electronic circuits 18 provided on the rear surface thereof as well as wirings 22 and electrothermal converters 26 provided inside the flexible thin film 16. This structure 10 is cut down out of the structure by properly cutting off this flexible thin film 16. Furthermore, this actuator 10 is electrically connected to outer elements by forming an aperture part in the flexible thin film 16 on the part of the electrode forming regions 24 in the end parts of the wirings 22.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for manufacturing an actuator, in particular a microactuator.

[0002]

2. Description of the Related Art In recent years, attention has been focused on micromachine technology, and its application to medical microrobots is expected. For this, it is essential to realize a miniaturized microactuator. In this regard, for example, an articulated manipulator using a shape memory alloy is disclosed in Japanese Patent Laid-Open No. 63-136014. The shape memory alloy actuator that is also used in this manipulator has a large displacement amount and a generated force amount per unit volume, and is regarded as a promising microactuator.

[0003]

In such a manipulator, an electrothermal conversion element for converting electric power for heating the shape memory alloy into heat and a feedback sensor are provided for each joint, so that the number of joints increases. Along with this, the number of wirings becomes very large. To avoid this, an electronic circuit for controlling the shape memory alloy must be provided for each joint. Individually creating and assembling these minute components is a major obstacle to miniaturization and leads to an increase in manufacturing cost. For these reasons, it is desired to establish a new manufacturing technology that does not require assembly.

As a method of realizing such a microactuator by a conventional technique, application of a technique for manufacturing a flexible substrate can be considered. Generally, a flexible substrate is made by sandwiching a wiring material such as copper with a flexible material such as polyimide. An opening is provided in the polyimide in the electrode region of the wiring material to mount an integrated circuit and various electronic components.
By applying this method and mounting a control electronic circuit, an electrothermal conversion element, a sensor, a displacement element, or the like on a flexible substrate, a microactuator can be realized. In this method, various functional elements must be individually mounted on a flexible substrate. The spatial area required for this implementation is an obstacle to miniaturization. Also,
Since there are many steps, it is disadvantageous in terms of manufacturing cost. Furthermore, the thinning of the flexible substrate is limited to about 100 μm. It is an object of the present invention to provide a method for stably and inexpensively manufacturing a shape memory alloy actuator having a very thin substrate.

[0005]

SUMMARY OF THE INVENTION The present invention is a flexible thin film, a shape memory alloy provided on the flexible thin film that deforms in response to temperature, and a flexible thin film for heating the shape memory alloy. A method for manufacturing an actuator, comprising: an electrothermal conversion element provided inside; and a wiring provided inside a flexible thin film for electrically connecting the electrothermal conversion element to an external circuit. Forming a flexible thin film having the inside thereof on the entire first main surface of the semiconductor substrate, providing a shape memory alloy on the flexible thin film, and arranging the flexible thin film in the actuator formation region of the semiconductor substrate. And a substrate removing step of exposing the flexible thin film by selectively removing the portion to be etched from the second main surface opposite to the first main surface.

Alternatively, according to the present invention, the flexible thin film, the shape memory alloy provided on the flexible thin film, which deforms depending on the temperature, and the flexible thin film for heating the shape memory alloy are provided. An actuator having an electrothermal conversion element, an electronic circuit for controlling the electrothermal conversion element, and wiring provided in a flexible thin film for electrically connecting the electrothermal conversion element and the electronic circuit to an external circuit A method of manufacturing an electronic circuit on the first main surface of the semiconductor substrate, and a flexible thin film having an electrothermal conversion element and wiring inside, on the entire first main surface of the semiconductor substrate. A step of forming, a step of providing a shape memory alloy on the flexible thin film, and a portion of the semiconductor substrate located in the actuator forming region is selectively removed from the second main surface opposite to the first main surface. The flexible thin film and the substrate removal process that exposes the electronic circuit It is.

[0007]

In the present invention, the actuator is once manufactured on the semiconductor substrate by utilizing the semiconductor manufacturing technology. After that, the semiconductor substrate is selectively removed while leaving a frame portion around the actuator. As a result, a structure is obtained in which the periphery of the actuator is supported by the semiconductor substrate. When using the actuator,
By appropriately cutting the flexible thin film, it is cut off from the structure and mounted on another structure or the like.

Next, the structure obtained through the steps of the present invention will be described with reference to FIG. In FIG.
(A) is a top view of the structure, (B) is the structure of (A) 1
It is sectional drawing cut | disconnected by the B-1B line. The structure has the semiconductor substrate 12 remaining in a frame shape as a result of selectively removing the semiconductor substrate and forming the opening 14. A flexible thin film 16 covering the opening 14 is provided over the entire surface of the semiconductor substrate 12. The actuator 10 is formed at the opening 14. The actuator includes a flexible thin film 16, a shape memory alloy 20 provided on the upper surface of the flexible thin film 16, an electrothermal conversion element (heater) 26 for heating the shape memory alloy 20, and a flexible thin film 16. It is composed of an electronic circuit 18 provided on the lower surface and a wiring 22 provided inside the flexible thin film 16. This actuator is cut off in a desired shape by appropriately cutting the flexible thin film 16 during use. The connection with an external circuit is made by forming an opening in the flexible thin film 16 in the electrode forming region 24 at the end of the wiring 22.

FIG. 2 shows a bending tube in which this actuator is mounted and used as a manipulator. The bending tube 30 is composed of a plurality of bending pieces 32 having a rotating shaft 34. The three bending pieces 32 form one bending portion. In the figure, a first bending portion 36 and a second bending portion 38 are shown. The first bending portion 36 and the second bending portion 38 are curved in directions in which the rotating shafts 34 of the bending pieces 32 forming the first bending portion 36 and the second bending portion 38 are orthogonal to each other. The actuator 10 shown in FIG. 1 is mounted on the bending tube 30, and one shape memory alloy 20 is arranged on one bending portion. The shape memory alloy 20 has a concave portion 4 extending in the longitudinal direction in the curved portion.
It is slidably inserted between 0 and the guide 42 provided above it. With this configuration, the shape memory alloy 20
Each bending portion bends in a predetermined direction according to the deformation of the.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 3, the semiconductor substrate 10
Silicon nitride films 104 and 106 are formed on both surfaces of No. 2 by low pressure chemical vapor deposition. Lower surface silicon nitride film 10
6, a predetermined region is etched to form the opening 108 by using a lithography process used in a general integrated circuit manufacturing technique. A polyimide film 110 is formed on the silicon nitride film 104 on the upper surface.

As shown in FIG. 4, on the polyimide film 110, an aluminum thin film pattern 112 functioning as wiring,
Titanium thin film pattern 1 that functions as a heater (electrothermal conversion element) for heating a shape memory alloy to be provided later
16. A constantan thin film pattern 118 and a copper thin film pattern 120 are formed. Constantan thin film pattern 1
The ends of 18 and the copper thin film pattern 120 are electrically connected to each other to form a thermocouple that functions as a temperature sensor. Each of the aluminum thin film pattern 112, the constantan thin film pattern 118, and the copper thin film pattern 120 has an electrode formation region 114 at the end. This is useful when forming a contact hole for the purpose of establishing an electrical connection with the outside. The metal thin film pattern described above is formed by using, for example, laser assisted CVD, sputter deposition, and a lithography technique. When the lithography technique is applied, an interlayer insulating film made of polyimide and a contact hole are made by the lithography technique as needed.

As shown in FIG. 5, a polyimide film 121 is formed on these metal thin film patterns 112, 116, 118 and 120. A shape memory alloy film 122 is formed on a portion of the polyimide film 121 corresponding to the titanium thin film pattern 116 by sputter deposition and a lithography technique. At this time, by setting the temperature during sputtering to a relatively high temperature of, for example, about 450 ° C., it is possible to function as a shape memory alloy without performing a special solution treatment.

As shown in FIG. 6, a wax 126 is applied on the laminated structure 124 formed on the semiconductor substrate 102 by the above-mentioned process, and the wax 126 is brought into contact with the glass plate 128 to make the semiconductor substrate 102 a glass plate 128. Fixed to. This is dipped in an organic alkali aqueous solution to form a silicon nitride film 106.
The semiconductor substrate 102 is etched from the lower surface using (see FIG. 3) as a mask. The etching is performed until the laminated structure 124 is exposed, as shown in FIG. The portion of the semiconductor substrate 102 where the silicon nitride film 106 is present remains without being etched. The structure remaining after etching is removed from the glass plate 128 by heating, and the remaining wax 124 is washed away with an organic solvent.

In the structure thus formed, the semiconductor substrate 102, which is finally left, serves as a framework for supporting the polyimide films 110 and 121 from all sides. The target actuators are polyimide films 110 and 121 having various metal thin film patterns 112, 116, 118, 120 supported between frames (semiconductor substrate 102) and shape memory formed thereon. It is composed of an alloy film 122. This actuator is separated from the semiconductor substrate 102 by cutting the polyimide film at an appropriate position. Such an actuator has a link mechanism after connecting each electrode forming region to an external circuit including a power source and a measuring device and performing feedback control of the current flowing through the heater by the temperature obtained from the thermocouple. By mounting on another structure, a two-joint manipulator can be constructed.

Although only one structure is shown in FIGS. 3 to 7 in the above description, this structure is very small, and many structures are actually manufactured on one silicon substrate at a time.
According to the present embodiment, the flexible thin film serving as the substrate of the actuator is a polyimide film formed on the entire surface of the semiconductor substrate,
Since it is obtained by removing the semiconductor substrate later, it can be formed very thin. The film thickness can be reduced to several microns. In addition, since the semiconductor substrate 102 that finally remains functions as a framework for supporting the polyimide films 110 and 121, it is effective in preventing damage when etching or separating from the glass plate. In this connection, the polyimide film can be formed with a very thin film thickness of about several microns. In addition, since the sensor, heater, and wiring between joints are all integrally formed, it is not necessary to assemble them, so it is possible to make them significantly smaller. In addition, many actuators can be manufactured with one substrate, which is also preferable in terms of manufacturing cost.

Next, a second embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 8, a silicon nitride film 204 is provided on the lower surface of the p-type semiconductor substrate 202, and an opening 208 is formed in a predetermined area. In addition, an island-shaped relatively deep n-type diffusion region 204 is formed on the upper surface of the p-type semiconductor substrate 202, and a CMOS device forming a predetermined electronic circuit is formed in the inner wiring layer by using a normal semiconductor manufacturing technique. It forms including. Hereinafter, although not particularly shown, the n-type diffusion region 2
In 04, a CMOS semiconductor circuit including an internal wiring layer is formed.

As shown in FIG. 9, a polyimide film 210 is formed on the upper surface of the semiconductor substrate 202 on which the n-type diffusion region (electronic circuit) 204 is formed, and corresponds to an electrode formation region provided on the electronic circuit 204 at a predetermined position. The opening 212 is formed. Here, although not particularly shown in the drawing, the polyimide film 210
In the lower layer, there is a silicon oxide film formed in the manufacturing process of the electronic circuit.

As shown in FIG. 10, an aluminum thin film pattern 2 which serves as wiring for electrically connecting the electronic circuits 204 to each other.
14 is formed. The aluminum thin film pattern 214 is connected to the electronic circuit 204 through the opening 212 described above. The wiring pattern 214a, which is one of the aluminum thin film patterns, is not an element forming an electronic circuit,
The n-type diffusion regions are electrically connected to each other. An electrode formation region 216 for connection with an external circuit is provided at an end of the aluminum thin film pattern 214. A titanium thin film pattern 218 which is connected to the aluminum thin film pattern 214 and serves as a heater for heating a shape memory alloy provided later.
To form. The titanium thin film pattern 218 is connected to the electronic circuit 204 via the aluminum thin film pattern 214.

As shown in FIG. 11, the polyimide film 210
A polyimide film 220 covering the aluminum thin film pattern 214 and the titanium thin film pattern 218 is formed on the upper surface of the. An opening is formed in the polyimide film 220 in the electrode formation region of the aluminum thin film pattern 214 for connection with an external circuit. Located above the titanium thin film pattern 218,
A shape memory alloy film 222, which has been subjected to shape memory processing in advance, is formed in a predetermined region on the polyimide film 220.

As shown in FIG. 12, a protective film 224 is provided to cover the laminated structure manufactured by the above-mentioned process, and it is dipped in an organic alkaline solution 226. The electrode 228 arranged in the organic alkaline solution 226 and the aluminum thin film pattern 214a are connected to the power supply 230, and a positive bias voltage is applied to the aluminum thin film pattern 214 with respect to the electrode 228. In this way, the p-type semiconductor substrate 202 is etched from the lower surface with the organic alkali solution 226 using the silicon nitride film 226 as a mask. Since the silicon nitride film is not etched with organic alkali, the etching is performed on the polyimide film 21.
It stops when the silicon nitride film (not shown) under 0 is exposed. In addition, the n-type diffusion region 20 in which an electronic circuit is formed
Since 4 is biased, anodization occurs when this region 204 is exposed during etching, so n
The mold diffusion region 204 remains without being etched. As a result, as shown in FIG. 13, the opening 2 is formed in the p-type semiconductor substrate 202 so that the n-type diffusion region 204 and the polyimide film remain.
32 is formed. Then, the silicon nitride film and the protective film 224 exposed on the lower surface are removed.

The structure thus manufactured is in a state of being supported by the semiconductor substrate 202 on which the intended actuator remains. The actuator is cut off by appropriately cutting the polyimide film as in the first embodiment, and mounted on another structure.

In this embodiment, the titanium thin film pattern 2 is used.
18 functions as a heater, and shape memory alloy 2
It also functions as a strain sensor that detects strain due to deformation of 22 as a change in resistance value. The electronic circuit 204 to which this heater is connected includes a bridge circuit and an amplifier necessary for detecting this change in resistance value. Further, the electronic circuit 204 has a function of defining an output to each heater by a predetermined drive signal pulse given from the outside and a function of sequentially transmitting the resistance value of the heater to a controller connected to the outside. By this, the manipulator is feedback-controlled by generating an appropriate drive signal pulse in the controller.

Since the actuator of this embodiment is provided with one electronic circuit for one shape memory alloy, it is suitable for application to a manipulator having a large number of joints. Further, since the detection circuit is arranged near the sensor, highly accurate feedback control can be performed. Since the electronic circuit is integrally formed with the inter-joint wiring, the heater, the actuator, and the sensor, it is not necessary to assemble them, so that it is possible to greatly reduce the size and reduce the manufacturing cost.

[0024]

According to the present invention, since the semiconductor manufacturing technique is utilized, the actuator can be manufactured in a large amount at a time at a very small size and at a low cost. In particular, in the structure that has undergone the steps of the present invention, the actuator is supported by the finally remaining semiconductor substrate, so that the actuator can be stably manufactured.

[Brief description of drawings]

FIG. 1 is a top view (A) and a sectional view taken along line 1B-1B (B) of a structure obtained through a process of the present invention.

FIG. 2 is a perspective view (A) and a sectional view taken along the line 2B-2B (B) of a bending tube in which the actuator shown in FIG. 1 is mounted.

FIG. 3 is a drawing for explaining the first step of the manufacturing method of the first embodiment.

FIG. 4 is a drawing for explaining the second step of the manufacturing method of the first embodiment.

FIG. 5 is a drawing for explaining the third step of the manufacturing method of the first embodiment.

FIG. 6 is a drawing for explaining the fourth step of the manufacturing method according to the first embodiment.

FIG. 7 is a drawing for explaining the final step of the manufacturing method of the first embodiment.

FIG. 8 is a drawing for explaining the first step of the manufacturing method of the second embodiment.

FIG. 9 is a drawing for explaining the second step of the manufacturing method of the second embodiment.

FIG. 10 is a drawing for explaining the third step of the manufacturing method of the second embodiment.

FIG. 11 is a drawing for explaining the fourth step of the manufacturing method of the second embodiment.

FIG. 12 is a drawing for explaining the etching step of the substrate in the manufacturing method of the second embodiment.

FIG. 13 is a diagram showing a state in which etching is completed in FIG.

[Explanation of symbols]

12 ... Semiconductor substrate, 14 ... Opening part, 16 ... Flexible thin film,
20 ... Shape memory alloy, 22 ... Wiring, 26 ... Electrothermal conversion element.

Claims (3)

[Claims] 1. A flexible thin film, a shape memory alloy provided on the flexible thin film and deformable according to temperature, and an electrothermal conversion element provided in the flexible thin film for heating the shape memory alloy. A method of manufacturing an actuator having a wiring provided in a flexible thin film for electrically connecting an electrothermal conversion element to an external circuit, wherein the electrothermal conversion element and the wiring may be internally provided. The step of forming a flexible thin film on the entire first main surface of the semiconductor substrate, the step of providing a shape memory alloy on the flexible thin film, and the portion of the semiconductor substrate located in the actuator formation region on the first main surface A substrate removing step of selectively removing the flexible thin film from the opposite second main surface to expose the flexible thin film. 2. A flexible thin film, a shape memory alloy provided on the flexible thin film and deformable according to temperature, and an electrothermal conversion element provided in the flexible thin film for heating the shape memory alloy. A method for manufacturing an actuator having an electronic circuit for controlling an electrothermal conversion element, and wiring provided in a flexible thin film for electrically connecting the electrothermal conversion element and the electronic circuit to an external circuit. And a step of forming an electronic circuit on the first main surface of the semiconductor substrate, and a step of forming a flexible thin film having an electrothermal conversion element and wiring inside on the entire first main surface of the semiconductor substrate. , A step of providing a shape memory alloy on the flexible thin film, and a portion of the semiconductor substrate located in the actuator formation region is selectively removed from the second main surface opposite to the first main surface to form the flexible thin film. And a substrate removing step for exposing the electronic circuit. Manufacturing method of Eta. 3. The substrate removing step comprises a step of forming a mask having an opening in an actuator formation region on the second main surface of the semiconductor substrate, and an alkaline solution of the semiconductor substrate with a voltage applied to the electronic circuit region. The method for manufacturing an actuator according to claim 2, further comprising: