Micro-relay and method for manufacturing the same

TECHNICAL FIELD

The present invention relates to electronic components such as micro-relays, and in particular micro-relays, matrix relays and micro-relay chips having contacts which are opened and closed by curving a movable piece constructed of a monocrystal thin plate-shaped substrate.

BACKGROUND ART

Conventionally, as a relay, there has been, for example, an electromagnetic relay utilizing an electromagnet. However, the relay, which necessitates mechanical components, is hard to be reduced in size. Furthermore, the movable components of the mechanical components, which have great inertial forces, tend to disadvantageously cause fatigue failure and lack in durability.

There is otherwise existing a semiconductor switching device as a sort of small-sized relay, however, the device disadvantageously has a great resistance in turning on its contact, degraded frequency characteristics and a low insulating property between its input and output and between its terminals of an identical polarity.

In view of the aforementioned problems, the present invention has a first object to provide a subminiature micro-relay that has a small resistance in turning on its contact as well as the desired vibration resistance, frequency characteristics and insulating property.

Conventionally, as a matrix relay, there has been, for example, the one disclosed in the prior art reference of Japanese Patent Laid-Open Publication No. HEI 7-29473. The matrix relay is an electromagnet array comprised of a required number of electromagnets obtained by winding a solenoid around a fixed contact core, where the contacts are opened and closed by driving a movable spring contact provided on a strip.

However, the above-mentioned matrix relay has the electromagnet obtained by winding the solenoid around the fixed contact core as a component, and this puts a limit on compacting the device, and in particular, reduction in thickness.

Most of the components are not flat, meaning that they cannot be stacked in one direction, and this poses the problem that the assembling is troublesome and the productivity is low.

In view of the aforementioned problems, the present invention has a second object to provide a subminiature matrix relay that can be easily assembled.

Further, conventionally, as an electronic component of the micro-relay chip, there has been the one proposed in FIG. 27 and FIG. 28 of Japanese Patent Laid-Open Publication No. HEI 7-299765. That is, the electronic component is a micro-relay obtained by wire-bonding the connecting electrodes of a micro-relay chip to the external terminals of a lead frame and molding them with resin.

However, according to the above-mentioned electronic component, the whole body of the micro-relay chip has been molded with resin, and therefore, heat radiation is hard to be achieved. Therefore, due to the heat generation of the internal components, a malfunction tends to occur and the operating characteristics tend to vary.

The above-mentioned electronic component is required to individually connect by wire bonding each connecting electrode of the micro-relay chip to each external terminal formed on the lead frame. For this reason, there is a great number of working processes, and the productivity is low. Furthermore, wire disconnection tends to be caused by vibration or the like, and this poses the problem that the reliability is low.

In view of the aforementioned problems, the present invention has a third object to provide an electronic component that can prevent the malfunction and the variation in operating characteristics due to heat and has high productivity and reliability.

DISCLOSURE OF THE INVENTION

In order to achieve the aforementioned first object, the first feature of the present invention is a micro-relay characterized by providing a thin plate-shaped substrate comprised of a monocrystal with a driving means, supporting on a base both ends of a movable piece at least one surface of which is provided with at least one movable contact and curving the movable piece via the driving means, thereby bringing the movable contact in and out of contact with a fixed contact that faces the movable contact, for making and breaking an electric circuit.

According to the first feature of the present invention, the contacts can be opened and closed by curving the thin plate-shaped substrate constructed of the monocrystal, and therefore, the device can be easily compacted. Furthermore, the inertial force of the movable piece constructed of the thin plate-shaped substrate is small, and therefore, fatigue failure is hard to occur, so that a micro-relay having an excellent durability can be obtained.

The movable piece has its both ends supported, and therefore, a micro-relay that is hard to receive the influence of external vibration or the like and has stable operating characteristics can be obtained.

Furthermore, there can be obtained a micro-relay that has a very small resistance in turning on the contact as compared with the semiconductor switching element, high frequency characteristics and insulating properties between its input and output and between its terminals of an identical polarity.

A second feature is a micro-relay in which a device wafer is connected and integrated with an opening edge portion of a box-shaped base comprised of a handle wafer via an insulating film, and the movable piece is formed by cutting a pair of slits through the device wafer.

According to the second feature, the movable piece is formed on the device wafer connected and integrated with the box-shaped base of the handle wafer. This arrangement allows the manufacturing processes to be wholly achieved by the semiconductor manufacturing techniques.

The handle wafer and the device wafer are connected and integrated with each other via the insulating film, and therefore, the wafers can be connected and integrated with each other at a temperature lower than in directly connecting and integrating silicon objects. For this reason, a material having a low melting point can be used for the fixed contact and the movable contact, allowing the degree of freedom of design to be expanded.

A third feature is a micro-relay in which the device wafer is formed with a connecting use opening portion in a position opposite to a connecting pad of the fixed contact provided on a bottom surface of the handle wafer.

According to the third feature, connection to the outside can be achieved by utilizing wire bonding via the connecting use opening portion provided at the device wafer. This allows the wiring structure of the micro-relay itself to be simplified for easy manufacturing.

A fourth feature is a micro-relay in which the inside surface of the connecting use opening portion is covered with an insulating film.

According to the fourth feature, the inside surface of the connecting use opening portion is covered with an insulating film. Therefore, even when wire bonding is performed, the wire is not brought in contact with the silicon layer, and it is not interfered by the driving use power source.

A fifth feature is a micro-relay in which a cooling fin is formed on the upper surface of the device wafer.

According to the fifth feature, heat generated from the movable piece speedily dissipates to the outside via the cooling fin formed on the upper surface of the device wafer. This improves the operating characteristics in the restoration stage.

Even when micro-relays are integrated with each other, the cooling fin efficiently radiates heat, so that malfunction due to overheat can be prevented.

A sixth feature is a micro-relay in which the movable piece is previously curved and urged so as to bring a movable contact provided on its one surface in contact with a fixed contact that faces the movable contact.

According to the sixth feature, the thin plate-shaped substrate is previously curved to bring the movable contact in contact with the fixed contact, and therefore, a self-retaining type micro-relay can be obtained, allowing the power consumption to be remarkably reduced.

A seventh feature is a micro-relay in which a pair of pivot axes that are coaxially provided projecting roughly from a center portion between both side edge portions of the movable contact are supported on the base, one side half of the thin plate-shaped substrate is previously curved and urged upward, the remaining side half is previously curved and urged downward and the one side halves are simultaneously reversely buckled via the driving means, thereby alternately making and breaking two electric circuits.

According to the seventh feature, the one side half of the thin plate-shaped substrate can be simultaneously reversely buckled for opening and closing the contacts, and this allows the simultaneous making and breaking of a plurality of electric circuits.

An eighth feature is a micro-relay in which the driving means is a piezoelectric element laminated on one surface of the thin plate-shaped substrate.

According to the eighth feature, the movable piece is curved by the piezoelectric element, and this allows the obtainment of a micro-relay that can save the power consumption attributed to heat generation and has good energy efficiency.

A ninth feature is a micro-relay in which the driving means is a heater layer formed on one surface of the thin plate-shaped substrate.

According to the ninth feature, the movable piece is curved by only the heater layer, and this allows the obtainment of a micro-relay that necessitates a reduced number of manufacturing processes and has a high productivity.

A tenth feature is a micro-relay in which the driving means is comprised of a heater layer formed on one surface of the thin plate-shaped substrate and a driving layer formed by laminating a metal material on the heater layer via an insulating film.

According to the tenth feature, the driving layer is formed by laminating the metal material having a high coefficient of thermal expansion, and this allows the obtainment of a micro-relay that has an excellent response characteristic and a great contact pressure.

An eleventh feature is a micro-relay in which the heater layer of the driving means is comprised of a metal material such as platinum or titanium or a polysilicon laminated on the one surface of the thin plate-shaped substrate via an insulating film.

According to the eleventh feature, the heater layer is formed by laminating the metal material or polysilicon on the one surface of the thin plate-shaped substrate, and this allows the obtainment of a heater layer that has a high dimensional accuracy. Therefore, a micro-relay having uniform operating characteristics can be obtained.

A twelfth feature is a micro-relay in which the driving means is a heater section comprised of a diffused resistor formed inside the thin plate-shaped substrate.

According to the twelfth feature, the driving means is the diffused resistor formed inside the thin plate-shaped substrate made of the monocrystal. Therefore, the generated heat can be effectively utilized, allowing the obtainment of a micro-relay having a small heat loss.

A thirteenth feature is a micro-relay in which an insulating film is formed on at least one of the front surface or the rear surface of the movable piece, the surface being formed with the movable contact.

According to the thirteenth feature, the insulating film ensures the insulating property and prevents the leak of heat generated from the driving means.

A fourteenth feature is a micro-relay in which silicon compound films that are made of a silicon oxide film, a silicon nitride film or the like and have different thickness values are formed on the front and rear surfaces of the movable piece.

According to the fourteenth feature, the silicon compound film is formed on the front and rear surfaces of the movable piece, and this prevents the leak of heat generated from the movable piece, allowing the obtainment of a micro-relay having a good thermal efficiency.

A fifteenth feature is a micro-relay in which a silicon compound film comprised of a silicon oxide film, a silicon nitride film or the like for giving at least one side of the movable piece a compressive stress in proximity to a critical value at which driving starts.

According to the fifteenth feature, the compressive stress in proximity to the critical value at which driving starts can be obtained from the silicon compound film, and this allows the obtainment of a micro-relay having a good response characteristic.

A sixteenth feature is a micro-relay in which at least one adiabatic slit is formed near both end portions of the movable piece.

According to the sixteenth feature, the adiabatic slit is formed near both the end portions of the movable piece. Therefore, the heat conducting area becomes small to allow the prevention of heat conduction from both the end portions of the movable piece. As a result, the energy can be effectively utilized, thereby allowing the response characteristic to be improved.

A seventeenth feature is a micro-relay in which the adiabatic slit is filled with a polymer material having low heat conductivity.

According to the seventeenth feature, the adiabatic slit is filled with the polymer material having low heat conductivity. With this arrangement, the energy can be more effectively utilized, thereby allowing the response characteristic to be improved.

An eighteenth feature is a micro-relay in which the movable piece is extended across the base via an adiabatic silicon compound portion formed in both end portions of the movable piece.

According to the eighteenth feature, heat is hard to be conducted to the base from both the end portions of the movable piece, so that the utilization of energy and the improvement of the operating characteristics can be achieved.

A nineteenth feature is a micro-relay in which the movable piece is provided with a slit in the vicinity of the movable contact, and a pair of hinge portions for pivotally supporting the movable contact are coaxially formed.

According to the nineteenth feature, the movable contact is pivotally supported, and this eliminates the one-side hitting of the movable contact against the fixed contact and improves the contact reliability.

A twentieth feature is a micro-relay in which a root portion of the movable piece is provided with a radius for alleviating stress concentration.

According to the twentieth feature, by providing the root portion of the movable piece with the radius, the fatigue failure due to stress concentration is hard to occur, so that the operating life is prolonged.

A twenty-first feature is a micro-relay manufacturing method characterized by connecting and integrating via an insulating film a device wafer with an opening edge portion of a box-shaped base comprised of a handle wafer and thereafter cutting a pair of parallel slits through the device wafer, thereby forming a movable piece.

According to the twenty-first feature, there is the effect that a micro-relay which can be processed wholly through the semiconductor manufacturing processes and has a high dimensional accuracy can be obtained.

Furthermore, in order to achieve the aforementioned second object, a twenty-second feature of the present invention is a matrix relay characterized by providing a thin plate-shaped substrate comprised of a monocrystal with a driving means, arranging in parallel a plurality of movable pieces whose one surface is provided with a movable contact in an insulated state, fixing and supporting on a base both ends of the movable pieces, individually curving the movable pieces via the driving means, and thereby bringing the movable contact in and out of contact with a fixed contact formed on a ceiling surface of a cover positioned above the base, for making and breaking an electric circuit.

A twenty-third feature is a micro-relay in which the driving means is a piezoelectric element laminated on one surface of the thin plate-shaped substrate.

A twenty-fourth feature is a micro-relay in which the driving means is comprised of a heater layer formed on one surface of the thin plate-shaped substrate.

A twenty-fifth feature is a micro-relay in which the driving means is comprised of a heater layer formed on one surface of the thin plate-shaped substrate and a driving layer formed by laminating a metal material on the heater layer via an insulating film.

According to the twenty-second, twenty-third, twenty-fourth and twenty-fifth features of the present invention, the contacts can be opened and closed by curving the movable piece constructed of the monocrystal thin plate-shaped substrate, and this allows the easy compacting of the device.

Furthermore, since the inertial force of the movable piece is small, the fatigue failure is hard to occur and the operating life is prolonged.

Furthermore, the movable piece has its both ends fixed and supported, and this allows the obtainment of a micro-relay that is hard to receive the influence of external vibration or the like and has stable operating characteristics.

In particular, according to the twenty-fifth feature, the driving layer made of the metal material is provided, and therefore, the operating characteristics become quick, and this improves the response characteristic.

A twenty-sixth feature is a matrix relay in which the driving means is made electrically connectable on a surface of the cover via a through hole provided at the cover.

A twenty-seventh feature is a matrix relay in which the fixed contact is made electrically connectable on a front surface of the cover via a through hole provided at the cover.

According to the twenty-sixth and twenty-seventh features, the electrical connection of the internal components can be performed on the surface of the cover, and this allows the connecting work to be easy.

A twenty-eighth feature is a matrix relay in which an upper end portion of the through hole exposed to the surface of the cover is electrically connected to a connecting pad provided on the surface of the cover via a printed wiring line formed on the surface of the cover.

According to the twenty-eighth feature, the connection to the external device can be performed in the desired position via the connecting pad provided on the surface of the cover, and this has the effect of convenience.

In order to achieve the aforementioned third object, a twenty-ninth feature of the present invention is an electronic component characterized by connecting and integrating a cover made of a glass material with a base made of a silicon material and resin-molding an electronic component chip assembled with an internal component on a substructure so that the cover is coated with the mold and the bottom surface of the base is exposed.

According to the twenty-ninth feature, the bottom surface of the base made of the silicon material having a heat conductivity higher than that of the glass material is exposed to the outside of the substructure. This allows the obtainment of an electronic component that is easy to radiate heat and able to prevent the occurrence of malfunction and a variation in operating characteristics.

A thirtieth feature is an electronic component in which the internal component is electrically connected to an external terminal of the substructure via a through hole provided at the cover.

According to the thirtieth feature, there is no need for performing the individual electrical connection by wire-bonding in contrast to the prior art example, and the internal components are electrically connected to the external terminal of the substructure via the through hole provided at the cover. This arrangement makes simple connecting work, improves the productivity and improves the connection reliability. In particular, if the external terminal is formed of a lead frame, the working processes are further reduced in number, and the productivity is improved.

A thirty-first feature is an electronic component in which a heat sink is provided on the bottom surface of the base exposed to the outside of the substructure.

According to the thirty-first feature, the heat radiation efficiency via the heat sink for radiating heat is improved. This arrangement has the effect of more effectively preventing the malfunction due to heat and the variation in operating characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a schematic sectional view showing a micro-relay according to a first embodiment of the present invention;

FIG. 2A

is a detailed plan view of the micro-relay shown in

FIG. 1

;

FIG. 2B

is a sectional view of the micro-relay bisected;

FIG. 2C

is a sectional view taken along the line

2

C—

2

C in

FIG. 2A

, showing an integrated state;

FIG.

3

A through

FIG. 3E

are sectional views showing the manufacturing processes of the movable contact block shown in

FIG. 1

;

FIG.

4

A through

FIG. 4D

are sectional views showing the manufacturing processes of the movable contact block shown in

FIG. 1

;

FIG.

5

A through

FIG. 5D

are sectional views showing the manufacturing processes of the movable contact block shown in

FIG. 1

;

FIG.

6

A through

FIG. 6D

are sectional views showing the manufacturing processes of the movable contact block shown in

FIG. 1

;

FIG.

7

A through

FIG. 7D

are sectional views showing the manufacturing processes of the movable contact block shown in

FIG. 1

;

FIG.

8

A through

FIG. 8D

are sectional views showing the manufacturing processes of the movable contact block shown in

FIG. 1

;

FIG.

9

A through

FIG. 9C

are sectional views showing the manufacturing processes of the movable contact block shown in

FIG. 1

;

FIG.

10

A through

FIG. 10C

are sectional views showing the manufacturing processes of the movable contact block shown in

FIG. 1

;

FIG.

11

A through

FIG. 11E

are sectional views showing the manufacturing processes of the movable contact block shown in

FIG. 1

;

FIG. 12A

is a plan view showing a micro-relay according to a second embodiment of the present invention;

FIG. 12B

is a sectional view of the micro-relay bisected;

FIG. 12C

is a sectional view taken along the line

12

C—

12

C in

FIG. 12A

, showing an integrated state;

FIG.

13

A through

FIG. 13E

are sectional views showing the manufacturing processes of the movable contact block shown in FIG.

12

A through

FIG. 12C

;

FIG.

14

A through

FIG. 14D

are sectional views showing the manufacturing processes of the movable contact is block shown in FIG.

12

A through

FIG. 12C

;

FIG.

15

A through

FIG. 15D

are sectional views showing the manufacturing processes of the movable contact block shown in FIG.

12

A through

FIG. 12C

;

FIG.

16

A through

FIG. 16D

are sectional views showing the manufacturing processes of the movable contact block shown in FIG.

12

A through

FIG. 12C

;

FIG.

17

A through

FIG. 17D

are sectional views showing the manufacturing processes of the movable contact block shown in FIG.

12

A through

FIG. 12C

;

FIG.

18

A through

FIG. 18D

are sectional views showing the manufacturing processes of the movable contact block shown in FIG.

12

A through

FIG. 12C

;

FIG. 19

is a sectional view showing the manufacturing process of the movable contact block shown in FIG.

12

A through

FIG. 12C

;

FIG. 20A

is a plan view showing a micro-relay according to a third embodiment of the present invention;

FIG. 20B

is a sectional view of the micro-relay bisected;

FIG. 20C

is a sectional view taken along the line

20

C—

20

C in

FIG. 20A

, showing an integrated state;

FIG. 21

is a perspective view showing a micro-relay according to a fourth embodiment of the present invention;

FIG. 22

is a plan view of the micro-relay shown in

FIG. 21

;

FIG.

23

A through

FIG. 23J

are sectional views showing the manufacturing processes of the handle wafer of the micro-relay shown in

FIG. 21

;

FIG.

24

A through

FIG. 24H

are sectional views showing the manufacturing processes of the device wafer of the micro-relay shown in

FIG. 21

;

FIG.

25

A through

FIG. 25F

are sectional views showing the manufacturing processes after the connection of the wafer shown in FIG.

23

A through

FIG. 24J

;

FIG.

26

A through

FIG. 26F

are sectional views showing the manufacturing processes after the connection of the wafer shown in FIG.

23

A through

FIG. 24J

;

FIG. 27

is a plan view showing a micro-relay according to a fifth embodiment of the present invention;

FIG. 28

is a perspective view showing a micro-relay according to a sixth embodiment of the present invention;

FIG. 29

is an enlarged perspective view of the fin shown in

FIG. 28

;

FIG. 30

is a plan view showing a micro-relay according to a seventh embodiment of the present invention;

FIG. 31

is a plan view showing a micro-relay according to an eighth embodiment of the present invention;

FIG. 32

is a plan view showing a micro-relay according to a ninth embodiment of the present invention;

FIG. 33

is a perspective view showing a micro-relay according to a tenth embodiment of the present invention;

FIG. 34

is a sectional view showing a micro-relay according to an eleventh embodiment of the present invention;

FIG. 35

is a sectional view showing a micro-relay according to a twelfth embodiment of the present invention;

FIG. 36

is a sectional view showing a micro-relay according to a thirteenth embodiment of the present invention;

FIG. 37A

is a graph showing the theoretical operating characteristics of a micro-relay that utilizes a piezoelectric element, and in particular, a relation between an application voltage and a contact load;

FIG. 37B

is a graph showing a relation between the application voltage and a displacement;

FIG. 38A

is a graph showing the theoretical operating characteristics of a micro-relay that concurrently uses a heater layer for a driving layer, and in particular, a relation between a temperature rise and the contact load;

FIG. 38B

is a graph showing a relation between the temperature rise and the displacement;

FIG. 39A

is a plan view showing the micro-relay of a fourteenth embodiment that is a matrix relay;

FIG. 39B

is a sectional view taken along the line

39

B—

39

B in

FIG. 39A

;

FIG. 40

is a sectional view taken along the line

40

—

40

in

FIG. 39A

;

FIG. 41A

is a matrix circuit diagram showing the circuit of the matrix relay of FIG.

39

A and

FIG. 39B

;

FIG. 41B

is a circuit diagram redrawn for providing a better view of

FIG. 41A

;

FIG. 42A

is a plan view showing a matrix relay according to a fifteenth embodiment of the present invention;

FIG. 42B

is a sectional view taken along the line

42

B—

42

B in

FIG. 42A

;

FIG. 43

is a sectional view taken along the line

43

—

43

in

FIG. 42A

;

FIG. 44

is a perspective view of a sixteenth embodiment showing a number of movable pieces arranged parallel for constituting a matrix relay;

FIG. 45

is a circuit diagram of a matrix relay according to a seventeenth embodiment, constructed of a number of relay elements;

FIG. 46

is a perspective view of an electronic component according to an eighteenth embodiment of the present invention; and

FIG. 47

is a cross sectional view of the electronic component shown in FIG.

46

.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described next with reference to the accompanying drawings of FIG.

1

through FIG.

47

.

As shown in

FIG. 1

, a micro-relay according to the first embodiment of the present invention is formed of a movable contact block

10

on the upper surface of which both ends of a movable piece

20

are fixed and supported and a fixed contact block

30

that is anodically bonded to this movable contact block

10

. Then, a movable contact

25

provided on the upper surface of the movable piece

20

faces a pair of fixed contacts

38

and

39

formed on the ceiling surface of the fixed contact block

30

while being able to come in and out of contact with the fixed contacts.

That is, as shown in FIG.

2

A through

FIG. 2C

, a base

11

constituting the movable contact block

10

is made of a wafer of silicon, glass or the like.

The movable piece

20

is provided by integrating a driving means for curving the movable piece in the direction of thickness with the upper surface of a thin plate-shaped substrate

21

made of a monocrystal of silicon or the like via an insulating film. Then, this driving means is constructed by laminating a driving use lower electrode and upper electrodes

22

and

23

on the front and rear surfaces of a piezoelectric element

24

.

The fixed contact block

30

is constructed of a wafer

31

of glass, silicon or the like and formed with input and output use through holes

32

and

35

and driving use through holes

33

and

34

.

The input and output use through holes

32

and

35

are electrically connected to the fixed contacts

38

and

39

, respectively, via printed wiring lines

36

and

37

formed on the lower surface of the wafer

31

. Further, the input and output use through holes

32

and

35

are provided with connecting pads

32

a

(not shown) and

35

a,

which are constructed of a conductive material and located at their lower end portions, in order to increase the reliability of connection to the printed wiring lines

36

and

37

.

On the other hand, the driving use through holes

33

and

34

are provided with connecting pads

33

a

and

34

a,

which are constructed of a conductive material and located at their lower end portions, so that the through holes can be connected to the driving use lower and upper electrodes

22

and

23

.

According to the present embodiment, the connecting points are aligned in an identical plane via the through holes

32

and

35

, and this provides the advantage that the connection is made easy.

A manufacturing method of the above-mentioned micro-relay will be described next.

As shown in FIG.

2

A through

FIG. 2C

, the present embodiment adopts the assembling method of manufacturing the movable contact block

10

and the fixed contact block

30

through different processes and thereafter integrating them with each other by anodic bonding.

It is to be noted that FIG.

3

A through

FIG. 10C

show local sectional views showing only the important parts for the sake of convenience of explanation.

First, for the movable contact block

10

as shown in FIG.

3

A through

FIG. 3E

, a thermal oxidation film (thermal SiO

2

) that becomes a mask material for TMAH (tetramethyl ammonium hydroxide) etching is formed on the front and rear surfaces of a first silicon wafer

11

a

that serves as the base

11

and has a thickness of 400 &mgr;m and a crystal orientation of 100. Then, a resist is coated, and a pattern for performing the TMAH etching is formed by photolithography. Next, the thermal oxidation film is etched and thereafter the resist is removed.

Next, as shown in

FIGS. 4A through 4C

, the silicon wafer

11

is etched by TMAH so as to form a cavity, and thereafter a silicon nitride film that becomes a mask material is laminated on the front and rear surfaces thereof. Then, the silicon nitride film and the thermal oxidation film on the front surface side are removed by dry etching and oxide film etching.

On the other hand, a high-concentration B (boron) and Ge (germanium) layer is made to epitaxially grow to a thickness of 2 &mgr;m on one surface of the silicon wafer having the thickness of 400 &mgr;m and the crystal orientation of 100. Further, a normal-concentration B layer is made to epitaxially grow to a thickness of 20 &mgr;m on its surface, thereby obtaining a second silicon wafer

21

a

for forming the thin plate-shaped substrate

21

. Then, the B layer of this second silicon wafer

21

a

is placed on the upper surface of the first silicon wafer

11

a

and integrated with the same by direct bonding (see FIG.

4

D).

Then, as shown in FIG.

5

A through

FIG. 5D

, the surface of the second silicon wafer

21

a

is etched by TMAH for thinning. Through this process, the etching stops in the high-concentration B and Ge layer that has epitaxially grown, and the normal-concentration B layer that has epitaxially grown is exposed, thereby forming the thin plate-shaped substrate

21

. Next, LTO (low-temperature oxide film) that serves as a protecting film for the lower electrode

22

, which will be described later, is formed on the front surface of the exposed B layer. Then, by successively laminating titanium (Ti) and platinum (Pt) by sputtering, the lower electrode

22

is formed. Further, a piezoelectric film (PZT) of lead zirconate titanate or the like is formed by sputtering.

Subsequently, as shown in FIG.

6

A through

FIG. 6D

, a resist is coated and a pattern of the piezoelectric film is formed by photolithography. Then, after etching by RIE (Reactive Ion Etching), the resist is removed, thereby forming the piezoelectric element

24

. Subsequently, an insulating film is formed by SOG (Spin On Glass) coating. The reason why SOG is used is that the piezoelectric film possibly changes its characteristics when heated and intended to form an insulating film without heating. Then, a resist is coated and a pattern is formed by photolithography. Further, after exposing the piezoelectric element

24

by removing the center portion of the insulating film, a platinum (Pt) thin film that becomes an upper electrode

23

is deposited by sputtering.

Subsequently, as shown in

FIGS. 7A through 7D

, a resist is coated on the platinum thin film, and the pattern of the upper electrode

23

is formed by photolithography. Then, the unnecessary platinum is etched away to form the upper electrode

23

, and the resist is removed. Further, a resist is coated, and a pattern for etching the insulating film of SOG located between the lower electrode

22

and the upper electrode

23

is formed by photolithography.

Subsequently, as shown in

FIGS. 8A through 8D

, the insulating film of SOG is etched by photolithography for the formation of a pattern of the insulating film between the lower electrode

22

and the upper electrode

23

and thereafter the photoresist is removed. Then, an insulating film SiO

2

for insulating between the upper electrode

23

and the movable contact

25

, which will be described later, is formed by sputtering or a method with LTO. Further, a movable contact materials Cr and Au are successively laminated by sputtering.

Then, as shown in FIG.

9

A through

FIG. 9C

, a resist is coated, and a pattern is formed by photolithography. Subsequently, the unnecessary movable contact material is removed by etching for the formation of a movable contact

25

and a connecting base

26

, and thereafter the resist is removed.

Further, as shown in FIG.

10

A through

FIG. 10C

, a resist is coated and a pattern is formed by photolithography. Then, the insulating film is removed to expose one end of the lower electrode

22

and the upper electrode

23

, and thereafter the resist is removed, thereby completing a movable contact block

10

provided with the movable piece

20

.

For the fixed contact block

30

as shown in FIG.

11

A through

FIG. 11E

, the output and input use through holes

32

and

35

and the driving use through holes

33

and

34

are formed through a glass wafer

31

. Then, a recess portion

31

a

for ensuring an operation space and a recess portion

31

b

for arranging the fixed contacts

38

and

39

are successively formed. Then, a conductive material is deposited on the recess portions

31

a

and

31

b

of the glass wafer

31

, and the unnecessary conductive material is etched by photolithography, thereby forming the printed wiring lines

36

and

37

. Further, by depositing a conductive material and etching the same by photolithography, the fixed contacts

38

and

39

and the connecting pads

32

a

(not shown),

33

a,

34

a

and

35

a

are formed, thereby completing the fixed contact block

30

. It is to be noted that the connecting pad

33

a

has a great film thickness for electrical connection to the lower electrode

22

.

Finally, as shown in FIG.

2

A through

FIG. 2C

, by placing the fixed contact block

30

on the movable contact block

10

and anodically bonding the same, the assembling is completed.

According to the present embodiment, the connecting pad

35

a

of the through hole

35

provided on the fixed contact block

30

is brought in pressure contact with the connecting base

26

provided on the movable contact block

10

. With this arrangement, the connection between the through hole

35

and the connecting pad

35

a

is ensured, providing the advantage that the connection reliability improves. It is to be noted that the through hole

32

has a similar structure.

The operation of the micro-relay of this first embodiment will be described.

First, if no voltage is applied to the piezoelectric element

24

, then the movable piece

20

remains flat, and the movable contact

25

is separated from the pair of fixed contacts

38

and

39

.

Subsequently, if a voltage is applied to the piezoelectric element

24

via the lower electrode

22

and the upper electrode

23

, then the piezoelectric element

24

is curved upward. By this operation, the movable piece

20

is curved to push up the movable contact

25

, and this movable contact

25

comes in contact with the pair of fixed contacts

38

and

39

, thereby making an electric circuit.

Then, if the voltage application to the piezoelectric element

24

is released, then the movable piece

20

is restored into the original state by the spring force of the thin plate-shaped substrate

21

, and the movable contact

25

is separated from the fixed contacts

38

and

39

.

It is to be noted that the piezoelectric element is not limited to the above-mentioned one, and it is acceptable to utilize a shape memory piezoelectric element that is deformed in the direction of thickness upon the application of voltage and retains its deformed state even when the voltage application is released.

Furthermore, with a design for obtaining the compressive stress in proximity to the critical value at which the driving starts from a silicon compound film such as a silicon oxide film or a silicon nitride film in the above embodiment, there can be provided the advantage that a large displacement can be obtained by a small input. It is to be noted that the position in which the silicon compound film is formed is not limited to the case of direct formation on the thin plate-shaped substrate, and the film may be formed in an arbitrary position.

As shown in

FIGS. 12A through 19

, the second embodiment is constructed so that the movable piece

20

is curved by taking advantage of the difference between the coefficient of thermal expansion of the thin plate-shaped substrate

21

and the coefficient of thermal expansion of a driving layer

28

formed on its upper surface by laminating a metal material, thereby opening and closing contacts. Therefore, the second embodiment differs from the first embodiment in that the contacts are opened and closed by taking advantage of the curving in the direction of thickness of the piezoelectric element

24

in the first embodiment.

It is to be noted that the second embodiment is assembled by anodically bonding the movable contact block

10

whose both ends are supported by the movable piece

20

with the fixed contact block

30

, similar to the first embodiment.

The base

11

constituting the movable contact block

10

is similar to the aforementioned first embodiment, and therefore, no description is provided therefor.

The movable piece

20

is provided by forming a driving layer

28

by laminating a metal material via an insulating film on a heater layer

27

formed inside the surface layer of a thin plate-shaped substrate

21

and further forming a movable contact

25

via an insulating film. Then, connecting pads

27

a

and

27

b

are exposed at both end portions of the heater layer

27

.

The fixed contact block

30

is provided by forming input and output use through holes

32

and

35

and driving use through holes

33

and

34

on a glass wafer

31

, similar to the aforementioned first embodiment. Then, the input and output use through holes

32

and

35

are electrically connected to fixed contacts

38

and

39

via printed wiring lines

36

and

37

. Further, at the lower end portions of the through holes

32

,

33

,

34

and

35

are formed connecting pads

32

a,

33

a,

34

a

and

35

a,

respectively, which are formed of a conductive material. It is to be noted that the connecting pads

32

a

and

35

a

are not shown.

Next, a manufacturing method of the micro-relay having the above construction will be described next.

It is to be noted that FIG.

13

A through

FIG. 19

show local sectional views showing only the important parts for the sake of convenience of explanation. Furthermore, as shown in FIG.

13

A through

FIG. 14D

, the processes to the formation of the thin plate-shaped substrate

21

on the base

11

are similar to those of the first embodiment, and therefore, no description is provided for them.

Therefore, as shown in FIG.

15

A through

FIG. 15D

, a resist is coated on the thin plate-shaped substrate

21

and a pattern of a portion that becomes the heater layer

27

is formed by photolithography. Further, B (Boron) ions are injected into the surface layer of the exposed thin plate-shaped substrate

21

. Subsequently, the photoresist is removed, and heating is performed for activating the injected B ions and increasing the electrical resistance.

Then, as shown in FIG.

16

A through

FIG. 16D

, LTO (low-temperature oxide film) is laminated so as to insulate the heater layer

27

. Further, a resist is coated, and a pattern for a contact hole is formed by photolithography. Subsequently, the unnecessary oxide film is removed to form the contact hole of the heater layer

27

, and thereafter the resist is removed. Subsequently, a metal thin film for forming the driving layer

28

and the connecting portions

27

a

and

27

b

is laminated on its surface by sputtering.

Further, as shown in FIG.

17

A through

FIG. 17D

, a resist is coated, and a pattern for forming the driving layer

28

and the connecting portions

27

a

and

27

b

is formed by photolithography. Then, the unnecessary metal thin film is removed by etching to form the driving layer

28

and the connecting portions

27

a

and

27

b,

and the resist is removed. Subsequently, an insulating film constructed of a low-temperature oxide film and a metal thin film formed by sputtering are successively laminated.

Subsequently, as shown in FIG.

18

A through

FIG. 18D

, a photoresist is coated and a pattern for the movable contact

25

and the connecting base

26

is formed by photolithography. After removing the unnecessary portion of the metal thin film by etching, the resist is removed. Further, the photoresist is coated, and a pattern of a contact hole for connection to the heater layer

27

is formed by photolithography. Then, the insulating film positioned on the contact hole is removed by patterning the insulating film, thereby exposing the connecting portions

27

a

and

27

b.

Then, by removing the photoresist as shown in

FIG. 19

, the movable contact block

10

that supports both ends of the movable piece

20

is completed.

On the other hand, the fixed contact block

30

is formed almost similar to the aforementioned first embodiment, and therefore, no description is provided therefor.

Finally, as shown in

FIG. 12B

, by placing the fixed contact block

30

on the movable contact block

10

and connecting and integrating them with each other by anodic bonding, the assembling work is completed.

According to the present embodiment, the connecting pad

35

a

provided at the lower end portion of the through hole

35

(not shown) comes in pressure contact with the connecting base portion

26

provided for the movable contact block

10

. This arrangement ensures the connection of the through hole

35

to the printed wiring line

37

and provides the advantage that the connection reliability improves. It is to be noted that a through hole

33

has the same structure.

The operation of this second embodiment will be described.

First, if no voltage is applied to the heater layer

27

, then the heater layer

27

does not generate heat. For this reason, the movable piece

20

remains flat, and the movable contact

25

is separated from the pair of fixed contacts

38

and

39

.

Subsequently, if a voltage is applied to the heater layer

27

via the connecting portions

27

a

and

27

b

so as to heat the same, the driving layer

28

is heated by the heat generation of the heater layer

27

so as to expand. This driving layer

28

has a coefficient of thermal expansion greater than that of the thin plate-shaped substrate

21

. For this reason, the movable piece

20

is curved so that its upper surface becomes convex, and the movable contact

25

comes in contact with the pair of fixed contacts

38

and

39

, thereby making an electric circuit.

Then, if the voltage application to the heater layer

27

is released so as to stop the heat generation, then the driving layer

28

contracts. By this operation, the movable piece

20

is restored into the original state by the spring force of the thin plate-shaped substrate

21

, and the movable contact

25

separates from the fixed contacts

38

and

39

.

According to the present embodiment, the coefficient of thermal expansion of the driving layer

28

that expands on the basis of the heat generation of the heater layer

27

is much larger than the coefficient of thermal expansion of the thin plate-shaped substrate

21

. For this reason, the present embodiment has the advantage that the response characteristic is good and a great contact pressure force can be obtained.

As shown in

FIGS. 20A through 20C

, the third embodiment is constructed so that a difference between the coefficient of thermal expansion of the thin plate-shaped substrate

21

and the coefficient of thermal expansion of the heater layer

27

formed inside the surface layer portion of the thin plate-shaped substrate

21

is utilized. For this reason, the third embodiment differs from the aforementioned second embodiment in that the difference between the coefficient of thermal expansion of the thin plate-shaped substrate

21

and the coefficient of thermal expansion of the driving layer

28

made of a metal material is utilized in the second embodiment. It is to be noted that an insulating film

29

is for insulating the movable contact

25

from the heater layer

27

.

The manufacturing of the present embodiment is almost similar to that of the aforementioned second embodiment except for the point that the driving layer

28

made of the metal material is not provided, and therefore, no description is provided therefor.

The operation of this third embodiment will be described.

First, if no voltage is applied to the heater layer

27

, then the heater layer

27

does not generate heat. Therefore, the movable piece

20

remains flat, and the movable contact

25

is separated from the pair of fixed contacts

38

and

39

.

Subsequently, if a voltage is applied to the heater layer

27

via the connecting portions

27

a

and

27

b,

then the heater layer

27

generates heat. For this reason, the heater layer

27

itself expands, and the thin plate-shaped substrate

21

is expanded by being heated by this heater layer

27

. However, the heater layer

27

has a coefficient of thermal expansion greater than that of the thin plate-shaped substrate

21

, and therefore, the movable piece

20

is deformed so that its upper surface becomes convex. For this reason, the movable contact

25

comes in contact with the pair of fixed contacts

38

and

39

, thereby making an electric circuit.

Then, if the voltage application to the heater layer