JP2002052499A - Actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator actuating in two directions. SOLUTION: Two girder structural bodies, which are formed by having first conductive semiconductor layers 1 and 7, second conductive impurity diffusion layers 2 and 8 formed on the surface of the conductive semiconductor layers 1 and 7 by diffusing impurities, insulating layers 3 and 9 formed on the first conductive semiconductor layers 1 and 7 and the second conductive impurity diffusion layers 2 and 8, metal layers 6 and 12 formed on the second conductive impurity diffusion layers 2 and 8 via the insulating layers 3 and 9 and having thermal expansion coefficient larger than that of the first conductive semiconductor layers, and two metal electrodes 4, 5 and 10, 11 contacting with the second conductive impurity diffusion layers 2 and 8 clamping the metal layers 6 and 12 are so joined that the faces of the first conductive semiconductor layers 1 and 7 without formed with the insulating layers 3 and 9 aye faced to each other via a heat insulation layer 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an actuator which is expected to be used in the field of micromachines.
In particular, the present invention relates to an actuator using silicon.

[0002]

2. Description of the Related Art In recent years, the need for an actuator using silicon, particularly a microactuator has been increasing. Here, the microactuator is a device that drives a minute structure by some force and uses the movement.

As a form of a conventional microactuator using silicon, as shown in FIG. 2, there is a form using a bimetal type silicon beam structure. This is specifically applied to micro relays and the like. Here, the bimetal system is a structure in which two types of metals having different thermal expansion coefficients are bonded to each other as shown in FIG. 3A.
As shown in (b), a driving force is used in which the metal member 14 having a large coefficient of thermal expansion expands and the metal member 15 having a small coefficient of thermal expansion contracts.

As shown in FIG. 2, a conventional basic actuator 21 includes a first conductive type semiconductor layer 1 and a second conductive type impurity diffusion layer formed on the surface of the first conductive type semiconductor layer 1 by impurity diffusion. 2, an insulating layer 3 formed on the first conductive type semiconductor layer 1 and the second conductive type impurity diffusion layer 2, and metal electrodes 4 and 5 in contact with the second conductive type impurity diffusion layer 2.
A metal layer formed on the impurity diffusion layer of the second conductivity type via the insulating layer and having a thermal expansion coefficient larger than that of the semiconductor layer of the first conductivity type; And metal electrodes 4 and 5 in contact with the impurity diffusion layer 2. Further, as shown in FIG. 2, one surface of the first conductivity type semiconductor layer 1 is fixed to the substrate 20.

More specifically, the first conductivity type semiconductor layer 1 has N
Type silicon layer, a P-type resistance layer for the second conductivity type impurity diffusion layer 2, a silicon oxide film for the insulating layer 3, a metal electrode 4,
An aluminum electrode can be used for 5 and an aluminum film can be used for the metal layer 6.

Next, the operation principle will be described. First, Joule heat is generated when a current is applied between the aluminum electrode 4 and the aluminum electrode 5 via the P-type resistive layer 2 by an energizing means (not shown). The Joule heat heats the N-type silicon layer 1 and the aluminum film 6. Since the coefficient of thermal expansion of the aluminum film 6 is larger than the coefficient of thermal expansion of the N-type silicon layer 1, it is indicated by an arrow A in FIG. As described above, a driving force curving downward is generated, and the actuator 21 is displaced downward. The angle of the actuator 21 with respect to the substrate 20 can be adjusted by controlling the magnitude of the current flowing between the aluminum electrode 4 and the aluminum electrode 5.

[0007]

In the above-mentioned conventional microactuator using silicon, the silicon beam structure can be displaced only in one direction as described above. For this reason, there is a problem that the application of the actuator is limited.

The present invention has been made in view of the above problems, and has as its object to provide an actuator that can be driven in two directions.

[0009]

According to a first aspect of the present invention, there is provided an actuator comprising: a first conductivity type semiconductor layer; a second conductivity type impurity diffusion layer formed on a surface of the first conductivity type semiconductor layer by impurity diffusion; An insulating layer formed on the first conductive type semiconductor layer and the second conductive type impurity diffusion layer, and a thermal expansion coefficient formed on the second conductive type impurity diffusion layer via the insulating layer; A two-beam structure including a metal layer having a larger thermal expansion coefficient than the one conductivity type semiconductor layer, and two metal electrodes in contact with the second conductivity type impurity diffusion layer so as to sandwich the metal layer. The body is joined via a heat insulating layer with the surfaces of the first conductive type semiconductor layers on which the insulating layer is not formed facing each other.

Further, the actuator according to claim 2 is
The invention according to claim 1, wherein the first conductive semiconductor layer is a conductive silicon layer.

The actuator according to claim 3 is
The invention according to claim 1 or 2, wherein the metal layer has a coefficient of thermal expansion of 1.3 × 10 ⁻⁵ / ° C. or more.

Further, the actuator according to claim 4 is
The invention according to any one of claims 1 to 3, wherein the thermal insulation layer has a thermal conductivity of 10 W / m · ° C or less.

[0013] The actuator according to the fifth aspect is characterized in that:
The invention according to any one of claims 1 to 4, wherein the heat insulating layer is a silicon oxide film.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, the first beam structure includes a first conductive type semiconductor layer 1, a second conductive type impurity diffusion layer 2 formed on the surface of the first conductive type semiconductor layer 1 by impurity diffusion, An insulating layer 3 formed on the one-conductivity-type semiconductor layer 1 and the second-conductivity-type impurity diffusion layer 2; and a thermal expansion coefficient formed on the second-conductivity-type impurity diffusion layer 2 via the insulating layer 3. It has a metal layer 6 having a larger thermal expansion coefficient than the one conductivity type semiconductor layer 1, and metal electrodes 4 and 5 having ohmic contact with the second conductivity type impurity diffusion layer 2 so as to sandwich the metal layer 6. ing.

In general, when a conductor is brought into contact with a conductor and the voltage-current characteristics of the contact portion have a linear relationship, this is called an ohmic contact.

Further, in FIG. 1, the second beam structure having the same structure as the first beam structure also has the first conductive type semiconductor layer 7 and the impurity diffusion on the surface of the first conductive type semiconductor layer 7. A second conductivity type impurity diffusion layer 8 formed by the above, an insulation layer 9 formed on the first conductivity type semiconductor layer 7 and the second conductivity type impurity diffusion layer 8, and a second conductivity type impurity diffusion layer 8 on the second conductivity type impurity diffusion layer 8. A metal layer 12 having a thermal expansion coefficient larger than that of the first conductive type semiconductor layer 7 and an ohmic contact with the second conductive type impurity diffusion layer 8 with the metal layer 12 interposed therebetween. , And metal electrodes 10 and 11 which take the same shape. Note that, as described above, the first beam structure and the second beam structure employ a bimetal system.

The actuator 22 according to the present embodiment includes:
As shown in FIG. 1, a first beam structure is formed, and an insulating layer 3 is formed.
One surface of the heat insulating layer 13 is joined to the surface of the first conductive type semiconductor layer 1 where no insulating layer 9 is formed, and the first conductive type semiconductor layer where the insulating layer 9 is not formed. The other surface of the heat insulating layer 13 is joined to the surface 7. Also,
As shown in FIG. 2, one surface of the first conductivity type semiconductor layer 7 is fixed to the substrate 20.

Specifically, an N-type silicon layer is formed on the first conductivity type semiconductor layers 1 and 7, and a P-type resistance layer formed by impurity diffusion such as boron is formed on the second conductivity type impurity diffusion layers 2 and 8. A silicon oxide film on the insulating layers 3 and 9;
5, 10, and 12 are provided with aluminum electrodes and metal layers 6, 1 and 2, respectively.
2 uses an aluminum film. Further, a silicon oxide film is used for the heat insulating layer 13. Since the thermal conductivity of the silicon oxide film is 8.4 W / m · ° C. and the thermal conductivity of silicon is 139 W / m · ° C., the thermal conductivity of the silicon oxide film 13 is , 7 are smaller than the thermal conductivity. The coefficient of thermal expansion of aluminum is 2.4 × 10
⁻⁵ / ° C., and the coefficient of thermal expansion of silicon is 7.6 × 10 ^−6.
/ ° C.

For example, the metal electrodes 4, 5, 10, and 12 may be made of Al-Si, Al-Si-C
An aluminum alloy electrode such as u can also be used. Also,
As the metal layers 6 and 12, a nickel film can be used in addition to the aluminum film. The thermal expansion coefficient of the nickel film is 1.
3 × 10 ⁻⁵ / ° C. The thermal conductivity of the heat insulating layer 13 is preferably about 1/10 or less of the thermal conductivity of silicon, and more preferably 10 W / m · ° C. or less.

Further, SOI (Silicon on I)
The buried oxide film of the wafer is used as the thermal insulating layer 13, and the silicon layer sandwiching the oxide film is N
The use as the mold silicon layers 1 and 7 is an effective means for realizing the actuator structure of the present embodiment.

Further, for example, the first conductivity type semiconductor layers 1 and 7
When a P-type silicon layer is used, an N-type resistance layer can be used for the second conductivity type impurity diffusion layers 2 and 8.

Next, the operation principle will be described. First, Joule heat is generated when a current is applied between the aluminum electrode 4 and the aluminum electrode 5 via the P-type resistive layer 2 by a current supply means (not shown). The Joule heat heats the N-type silicon layer 1 and the aluminum film 6, and the coefficient of thermal expansion of the aluminum film 6 is larger than that of the N-type silicon layer 1, as shown by the arrow B in FIG. A driving force curving downward is generated, and the bimetallic actuator 22 is displaced downward.

At this time, a part of the Joule heat is also conducted to the N-type silicon layer 7 and the aluminum film 12 through the silicon oxide film 13, and a force for bending upward and displacing in FIG. Since the oxide film 13 exists, the temperature of the N-type silicon layer 1 and the temperature of the aluminum film 6 rise more than the N-type silicon layer 7 and the aluminum film 1 respectively.
It is much larger than the temperature rise of 2. Therefore, the actuator 22 is displaced downward. Actuator 22
Can be adjusted by controlling the magnitude of the current flowing between the aluminum electrode 4 and the aluminum electrode 5. Next, similarly, a P-type electrode is formed between the aluminum electrode 10 and the aluminum electrode 11. Resistance layer 8
Joule heat is generated when an electric current is passed through an energizing means (not shown) via the. The N-type silicon layer 7 is generated by the Joule heat.
And the aluminum film 12 is heated, and the N-type silicon layer 7 is heated.
Since the coefficient of thermal expansion of the aluminum film 12 is greater than the coefficient of thermal expansion of the aluminum film 12, a driving force curving upward is generated as shown by the arrow C in FIG. 1, and the bimetallic actuator 22 is displaced upward.

At this time, a part of the Joule heat is also conducted to the N-type silicon layer 1 and the aluminum film 6 through the silicon oxide film 13, and a force which is bent downward in FIG. Due to the presence of the oxide film 13, the temperature rise of the N-type silicon layer 7 and the aluminum film 12 is greater than that of the N-type silicon layer 1 and the aluminum film 6, respectively.
Much higher than the temperature rise. Therefore, the actuator 22 is displaced upward. The angle of the actuator 22 with respect to the substrate 20 depends on the aluminum electrode 10
It can be adjusted by controlling the magnitude of the current flowing between the electrode and the aluminum electrode 11.

The present embodiment is a microactuator having a bimetallic silicon beam structure, and can be used for a microrelay, for example.

In such an actuator, the actuator 22 can be displaced in two directions via the heat insulating layer 13.

In the above embodiment, the insulating layers 3 and 9
A silicon oxide film, an aluminum electrode for the metal electrodes 4, 5, 10, and 12, an aluminum film for the metal layers 6 and 12, and a silicon oxide film for the heat insulating layer 13.
It is not limited to this configuration.

[0029]

As described above, in the actuator according to the first aspect of the present invention, the first conductive type semiconductor layer and the second conductive type impurity diffusion layer formed on the surface of the first conductive type semiconductor layer by impurity diffusion. A layer, an insulating layer formed on the first conductive type semiconductor layer and the second conductive type impurity diffusion layer, and a thermal expansion formed on the second conductive type impurity diffusion layer via the insulating layer. A metal layer whose coefficient is larger than the coefficient of thermal expansion of the first conductivity type semiconductor layer;
The two beam structures having the conductive impurity diffusion layer and the two metal electrodes in contact with each other are separated by a heat insulating layer into the first conductive semiconductor layer on which the insulating layer is not formed. The actuators can be driven in two directions by using the difference in the coefficient of thermal expansion because the surfaces are joined to face each other. Therefore, the use as an actuator has been expanded compared to the case where driving can be performed in only one direction as in the conventional method.

The actuator according to claim 2 is
In the first aspect of the present invention, the first conductive type semiconductor layer is a conductive type silicon layer, so that the actuator according to the present invention can be easily realized.

Further, the actuator according to claim 3 is
In the invention according to claim 1 or 2, the thermal expansion coefficient of the metal layer is 1.3 × 10 ⁻⁵ / ° C. or more, and a driving force generated due to a difference in the thermal expansion coefficient is determined. It can be sufficiently expressed.

Further, the actuator according to claim 4 is
The invention according to any one of claims 1 to 3, wherein the thermal insulation layer has a thermal conductivity of 10 W / m · ° C or less, and the first beam structure and the second beam structure. By reducing the heat conduction between the structure and the structure, it is possible to perform two-way driving that makes full use of the difference in the coefficient of thermal expansion.

Further, the actuator according to claim 5 is
The invention according to any one of claims 1 to 4, wherein the heat insulating layer is a silicon oxide film, and a thermal interface between the first beam structure and the second beam structure. Conduction can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of an actuator according to an embodiment of the present invention.

FIG. 2 is a sectional view of an actuator according to a conventional example.

FIG. 3 is a sectional view showing a bimetal system.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first conductive type semiconductor layer 2 second conductive type impurity diffusion layer 3 insulating layer 4 metal electrode 5 metal electrode 6 metal layer 7 first conductive type semiconductor layer 8 second conductive type impurity diffusion layer 9 insulating layer 10 metal electrode 11 metal Electrode 12 Metal layer 13 Thermal insulation layer 14 Metal member 15 Metal member 20 Substrate 21 Actuator 22 Actuator

Claims (5)

[Claims] A first conductivity type semiconductor layer; a second conductivity type impurity diffusion layer formed on the surface of the first conductivity type semiconductor layer by impurity diffusion; the first conductivity type semiconductor layer and the second conductivity type. An insulating layer formed on the impurity diffusion layer; and a thermal expansion coefficient formed on the second conductivity type impurity diffusion layer via the insulating layer, the thermal expansion coefficient being larger than that of the first conductivity type semiconductor layer. The two beam structures each having a metal layer and two metal electrodes in contact with the second conductivity type impurity diffusion layer so as to sandwich the metal layer are separated from each other by a heat insulating layer. An actuator, wherein the surfaces of the first conductivity type semiconductor layers, on which no layers are formed, are joined to face each other. 2. The actuator according to claim 1, wherein the first conductive semiconductor layer is a conductive silicon layer. 3. The thermal expansion coefficient of said metal layer is 1.3 × 10
The actuator according to claim 1 or 2, wherein the temperature is ⁻⁵ / ° C. or more. 4. A thermal conductivity of the heat insulating layer is 10 W / m ·
The actuator according to any one of claims 1 to 3, wherein the temperature is lower than or equal to ° C. 5. The actuator according to claim 1, wherein the heat insulating layer is a silicon oxide film.