JP2010177143A - Piezoelectric drive type mems switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric drive type MEMS switch capable of suppressing deviations in a structure caused by bending of a driving part and having stable electrical characteristics and effective in power consumption saving. <P>SOLUTION: The piezoelectric drive type MEMS switch 10 has a structure in which, an opposing pair of cantilevers 20, 22, in which a ground (a lower electrode) 14 and an upper electrode 18 are formed at the front and the rear of a piezoelectric layer 16 are supported on a base board 12 in cantilever form. On a shorter cantilever 22, there are formed a signal line 36 and a contact electrode 24. The signal line 34 formed on a longer cantilever 20 is extended up to a length enough to contact the contact electrode 24. Since the signal line 34 lies along the bent of the first cantilever 20, a state of a switch-ON is maintained, by pressing the contact electrode 24 in a state of non-voltage load; and since in a state of voltage being impressed, the signal line follows the cantilever 20 bent in a direction opposed to initial state, it parts with the contact electrode 24 to become a state of switch-OFF. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric drive type MEMS switch used in an electronic apparatus.

  In a conventional actuator as an electric micromechanical device (MEMS), a driving arm serving as a driving unit of the actuator is supported on a substrate, a positive voltage is applied to one of the substrate and the electrostatic electrode provided on the driving arm, and the other By applying a negative voltage to the electrostatic electrode, the drive arm is pulled toward the substrate side by using the electrostatic force generated thereby. In addition, the actuator described in Patent Document 1 and the control method thereof and the switch using the actuator are provided with a piezoelectric layer and a piezoelectric drive electrode with respect to the drive arm, so that the drive arm is mounted on the substrate side using piezoelectric power. A configuration for attracting the user is disclosed.

  FIG. 9 shows an example of a piezoelectric driven micromechanical device. FIG. 9A is a perspective view showing the overall configuration of the piezoelectric drive type MEMS switch, and FIG. 9B is a schematic view showing an end face when the (A) is cut along line # C- # C. . In the piezoelectric drive type MEMS switch 100 shown in FIG. 9, a ground 104 serving as a lower electrode of the piezoelectric layer 112 is formed on a substrate 102, and a connection electrode 104A for connection is formed on the ground 104. ing. Further, an upper electrode 114 of the piezoelectric layer 112 is formed on the ground 104, and a connection electrode 114A for connection is formed on the upper electrode 114. The drive arm 110 includes a first cantilever 110A, a second cantilever 110B, hinges 118A and 118B, and a contact 120. On the upper surface of the contact 120, a capacitor portion (or capacitor) 122 corresponding to the hinge portions 118A and 118B is provided. On the other hand, the signal line 108 is formed so as to bridge the driving arm 110 and the hole 106 formed in the substrate 102, and a ground line 116 is formed on the left and right sides so as to bridge the driving arm 110 and the hole 106. Is formed.

JP 2005-302711 A

  However, in the electrostatic and piezoelectric drive type micro mechanical device (MEMS) of the background art as described above, when a movable part formed by combining different materials is formed, as shown in FIG. Warping occurs, making it difficult to control the gap between the signal line 108 and the contact 120, and the switch ON / OFF characteristics cannot be obtained due to the structure.

  The present invention pays attention to the above points, and its purpose is to suppress the variation of the structure caused by the warp of the drive unit, and to have a stable electrical characteristic and also effective for low power consumption. A driven MEMS switch is provided.

  In order to achieve the above object, the piezoelectric drive type MEMS switch of the present invention has electrode layers on the front and back surfaces of a substantially plate-like piezoelectric layer, and one end side is supported in a cantilever shape on the substrate. , A pair of cantilevers with different warping amounts arranged on the other cantilever, and a first signal formed on one cantilever so as to protrude from the end facing the other cantilever And a second signal line that is formed on the other cantilever and is connected to the contact electrode provided on the end facing the one cantilever, and at least uses the warpage of one cantilever By doing so, the connection between the contact electrode and the first signal line is switched ON / OFF.

  One of the main forms is characterized in that the difference in the amount of warpage between the pair of cantilevers is caused by the difference in the stress of the material constituting the cantilevers or the difference in the size or weight of the cantilevers. Another aspect is characterized in that opposing ends of the pair of cantilevers are connected via a hinge while allowing the warping.

  In another embodiment, the contact electrode and the second signal line are formed on a cantilever with a small amount of warp, and the first signal line is formed on a cantilever with a large amount of warp, so that there is no connection to the cantilever. The contact electrode and the first signal line are in contact with each other in a voltage load state, and the contact electrode and the first signal line are separated from each other when the voltage applied to the cantilever is bent in the opposite direction to the initial state. The switch is formed. Alternatively, the contact electrode and the second signal line are formed on a cantilever having a large amount of warping, and the first signal line is formed on a cantilever having a small amount of warping, so that the cantilever is in a no-voltage load state. The contact electrode is separated from the first signal line, and by applying a voltage to the cantilever, the cantilever is warped in the opposite direction to the initial state to form a normally-off switch in which the contact electrode and the first signal line are in contact with each other. It is characterized by that.

  Still another embodiment is characterized in that a plurality of the normally ON switch and the normally OFF switch are formed at a time so as to include one or more. Still another embodiment is characterized in that the normally ON switch and the normally OFF switch are collectively formed to constitute an SPDT (single pole double throw) switch. Yet another embodiment is characterized in that the normally OFF switch is multistaged. The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

  The present invention has electrode layers on the front and back surfaces of the piezoelectric layer, and the other end is supported in a cantilever shape on the substrate so that the one end faces each other, and on a pair of cantilevers with different warpage amounts, By forming signal lines and contact electrodes, and switching the ON / OFF of the connection between the contact electrodes and the signal lines using the warp of the cantilever, it is possible to suppress the variation in the structure caused by the warp and to stabilize the electricity. There is an effect that characteristics can be obtained. In addition, since the switch can be kept on in a no-voltage load state, power consumption can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the piezoelectric drive type MEMS switch of Example 1 of this invention, (A) is an external appearance perspective view which shows the whole structure, (B) cuts said (A) along the # A- # A line. Sectional view seen in the direction of the arrow, (C) is an enlarged view of the contact portion (A). It is a figure which shows the structure remove | excluding the signal wire | line and the ground wire from the switch of the said Example 1, (A) is an external appearance perspective view which shows the whole structure, (B) is said (A) to # B- # B line | wire. A section taken along the line and viewed in the direction of the arrow, (C) is a sectional view of a modification. It is explanatory drawing of the drive state of the switch of the said Example 1. FIG. It is principal sectional drawing which shows the piezoelectric drive type MEMS switch of Example 2 of this invention, (A) is a figure which shows an initial state (switch OFF state), (B) and (C) are at the time of voltage application (drive mode ( It is a figure which shows a switch ON state)). It is a circuit diagram which shows the piezoelectric drive type MEMS switch of Example 3 of this invention, (A) is a figure which shows an initial state, (B) is a figure which shows the state at the time of voltage application. It is explanatory drawing of the drive state of Example 4 of this invention, and the piezoelectric drive type MEMS switch of a modification. It is a figure which shows the example of stress of a metal thin film. It is a figure which shows the other Example of this invention. It is a figure which shows an example of background art, (A) is an external appearance perspective view which shows the whole structure of a piezoelectric drive type MEMS switch, (B) is an end surface when said (A) is cut | disconnected along # C- # C FIG.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on examples.

  First, Embodiment 1 of the present invention will be described with reference to FIGS. 1A and 1B are diagrams showing a piezoelectric drive type MEMS switch according to the present embodiment, in which FIG. 1A is an external perspective view showing the overall configuration, and FIG. 1B is a sectional view taken along line # A- # A. FIG. 6C is a cross-sectional view viewed in the direction of the arrow, and FIG. 2A and 2B are diagrams showing a structure in which the signal line and the ground line are removed from the switch of the present embodiment. FIG. 2A is an external perspective view showing the entire configuration, and FIG. Sectional drawing cut | disconnected along B line | wire and it looked at the arrow direction, (C) is sectional drawing which shows a modification. FIG. 3 is an explanatory diagram of a driving state of the piezoelectric drive type MEMS switch of the present embodiment.

  In the piezoelectric drive type MEMS switch 10 (hereinafter simply referred to as “switch”) of the present embodiment, a ground 14 serving as a lower electrode of the piezoelectric layer 16 is formed on a substrate 12. A piezoelectric layer 16 and its upper electrode 18 are formed. A hole 40 is formed in a substantially central portion of the substrate 12, and on both sides thereof, one end side of the first cantilever 20 and the second cantilever 22 is supported in a cantilever shape, and the other end side is supported. The holes 40 face each other in the vicinity of the approximate center.

  As the substrate 12, for example, an SOI substrate (a conductor using single crystal silicon formed on an insulating film as a substrate) is used, and as the ground (lower electrode) 14 and the upper electrode 18, for example, Pt (platinum) or Ru (ruthenium) or the like is used. As the piezoelectric layer 16, for example, PZT (lead zirconate titanate) is used. The first cantilever 20 and the second cantilever 22 are a laminate of the upper electrode 18 / piezoelectric layer 16 / ground (lower electrode 14) / substrate 12, and have different lengths on the left and right. There is a difference in warpage. In the present embodiment, the first cantilever 20 is formed longer than the second cantilever 22, and as shown in FIG. 2 (B), the second cantilever 22 shows almost no warp, One cantilever 20 is warped relatively large.

  In this embodiment, the opposing end portions of the first cantilever 20 and the second cantilever 22 are connected via a hinge 26 while allowing warping, so that the first cantilever 20 is more than necessary. To prevent warping. The hinge 26 may be provided as necessary, and may be configured without a hinge as in the modification shown in FIG.

  On the second cantilever 22, one signal line 36 (second signal line) constituting the signal line 32 is formed, and a contact electrode is connected to the end portion 36 </ b> A of the signal line 36. 24 is provided on the free end side of the second cantilever 22. On the other first cantilever 20, the other signal line 34 (first signal line) constituting the signal line 32 is formed. The signal line 34 is longer than the first cantilever 20, and its end 34 </ b> A is set to have a length that allows contact with the contact electrode 24. Since such a signal line 34 follows the warp of the first cantilever 20, it presses the contact electrode 24 in the no-voltage load state and follows the cantilever 20 that warps in the opposite direction to the initial state in the voltage applied state. , Away from the contact electrode 24, and is in a non-contact state. On both sides of the signal line 32, ground lines 28 and 30 substantially parallel to the signal line 32 are provided so as to bridge the hole 40. As the signal line 32, the ground lines 28 and 30, and the contact electrode 24, for example, Au is used.

  Next, driving of the switch of this embodiment will be described with reference to FIG. 3 (A-1) and (A-2) are diagrams showing an initial state (non-voltage load state), and FIGS. 3 (B-1) and (B-2) are diagrams showing a voltage application state. Since the cantilever warpage is proportional to its length, the signal wire 34 presses the contact electrode 24 when the first long cantilever 20 is greatly warped, and the RF signal passes through the contact electrode 24. (Fig. 3 (A-1)). As a result, even when there is no voltage load, the switch SW is in an ON state (FIG. 3 (A-2)). Switching to the switch OFF is performed by applying a voltage to the actuator unit (cantilevers 20 and 22). When a voltage is applied, as shown in FIG. 3 (B-1), the first cantilever 20 is displaced upward (along the direction opposite to the initial state), and the signal line 34 is separated from the contact electrode 24. The switch SW is turned off (FIG. 3 (B-2)).

Thus, according to the first embodiment, there are the following effects.
(1) A signal line 32 (34 and 36) and a contact electrode 24 are formed on a pair of cantilevers 20 and 22 supported in a cantilever shape on the substrate 12 so that one end faces each other. Since the ON / OFF switching of the connection between the contact electrode 24 and the signal line 34 is performed by using the warpage of the normal ON type having stable electrical characteristics while suppressing the variation in the structure caused by the warpage. The piezoelectric drive type MEMS switch 10 is obtained.
(2) Since the switch ON state can be maintained in the initial state (no-voltage load state), the power consumption can be reduced.
(3) Miniaturization can be realized by forming the signal line 32 and the contact electrode 24 on the first and second cantilevers 20 and 22.
(4) Since the first cantilever 20 and the second cantilever 22 are connected via the hinge 26, the cantilever can be prevented from warping more than necessary.

  Next, Embodiment 2 of the present invention will be described with reference to FIG. In addition, the same code | symbol shall be used for the component which is the same as that of Example 1 mentioned above, or respond | corresponds (it is the same also about a following example). The first embodiment described above is an example of a piezoelectric drive type MEMS switch having a normally ON structure, but the present embodiment is an example in which a normally OFF structure is used by utilizing the warpage of a cantilever. FIG. 4 is a main cross-sectional view showing the piezoelectric drive type MEMS switch of the present embodiment, (A) is a diagram showing an initial state (switch OFF state), and (B) and (C) are when voltage is applied (drive mode). , Switch ON state).

  Also in the present embodiment, the difference in the amount of warpage caused by the difference in length between the pair of cantilevers is used as in the above-described embodiment. In the piezoelectric drive type MEMS switch 50 of the present embodiment, a first cantilever 52 and a second cantilever 54 are connected via a hinge 26, and in the vicinity of the end of the longer first cantilever 52, A signal line 58 (second signal line) and a contact electrode 56 connected to the signal line 58 are provided. The signal line 60 (first signal line) provided on the shorter second cantilever 54 is longer than the cantilever 54, and its end 60A is set to a length that can contact the contact electrode 56. Yes. The basic laminated structure of the first cantilever 52 and the second cantilever 54 is the same as that of the first embodiment.

  In the switch 50 having such a structure, as shown in FIG. 4A, the contact electrode 56 and the signal line 60 are in a non-contact state, that is, in a switch OFF state, in a no-voltage load state. In order to turn on the switch, as shown in FIG. 4B, a voltage is applied to the first cantilever 52, and the first cantilever 52 is warped in the opposite direction to that shown in FIG. The electrode 56 and the signal line 60 are brought into contact with each other. Alternatively, as in the example shown in FIG. 4C, a voltage is applied to both the first cantilever 52 and the second cantilever 54 to drive the contact electrode 56 and the signal line 60 in contact with each other. Good. According to the present embodiment, similarly to the above-described first embodiment, a normally OFF type piezoelectric drive type MEMS switch 50 having stable electrical characteristics by suppressing the variation of the structure caused by the warp can be obtained.

  Next, Embodiment 3 of the present invention will be described with reference to FIG. 5A and 5B are circuit diagrams of the piezoelectric drive type MEMS switch of the present embodiment, in which FIG. 5A is a diagram illustrating an initial state, and FIG. 5B is a diagram illustrating a state when a voltage is applied. The present embodiment is an example of an SPDT (single pole double throw) structure in which the normally ON type switch of the first embodiment described above and the normally OFF type switch of the second embodiment are combined. The normally-on type switch SW1 and the normally-off type switch SW2 can be formed together. In the initial state shown in FIG. 5A, the switch SW1 is normally ON, the RF signal (high-frequency signal) passes to out1, and the switch SW2 is normally OFF. The power consumption in this state Is zero.

  Next, as shown in FIG. 5B, to switch the RF signal to out2, the switch SW1 needs to be turned off. As shown in FIG. 3 of the first embodiment, it is necessary to apply a voltage to turn off SW1, and this voltage (power consumption) is used to switch on SW2, thereby reducing power consumption. Can be planned. The SPDT structure of this embodiment is effective in a circuit configuration that uses RFout1 preferentially and uses RFout2 less frequently.

  Next, Embodiment 4 of the present invention will be described with reference to FIG. 6 (A-1) and (A-2) are diagrams showing an initial state (no-voltage load state), and FIGS. 6 (B-1) and (B-2) are diagrams showing a voltage application state. FIG. 6C is a diagram illustrating an initial state (non-voltage load state) of the modification. FIG. 7 is a diagram illustrating an example of stress of a metal thin film. The piezoelectric drive type MEMS switch 70 of the present embodiment has a form in which a compressive stress film is formed on the upper electrode 18. In the piezoelectric drive type MEMS switch 70, the first cantilever 20 and the second cantilever 22 have the same length in the example shown in FIGS. Therefore, a compressive stress film 72 is formed on the upper electrode 18 of the first cantilever 20 so that the warp of the first cantilever 20 faces downward. As the compressive stress film 72, a metal film (for example, Ta) is used, and shows a stress as shown in FIG. 7 (reference: DW Hoffman, J. Vac. Sci. Technol. 20 (3 ), March 1982).

  Here, since the lengths of the first cantilever 20 and the second cantilever 22 are equal, if the compressive stress film 72 is selectively formed only on the upper electrode 18 of the first cantilever 20, When only the cantilever 20 is warped downward, the signal line 34 presses the contact electrode 24, and the RF signal passes through the contact electrode 24 (FIG. 6A-1). As a result, the switch SW is in an ON state (FIG. 6 (A-2)) even when there is no voltage load. Switching to the switch OFF is the same as in the first embodiment described above, and is performed by applying a voltage to the actuator unit (cantilevers 20 and 22). When a voltage is applied, as shown in FIG. 6B-1, the first cantilever 20 is displaced upward (along the direction opposite to the initial state), and the signal line 34 is separated from the contact electrode 24. The switch SW is turned off (FIG. 6 (B-2)).

  As described above, according to the fourth embodiment, since the compressive stress film 72 is provided, the first and second cantilevers 20 and 22 can be set to substantially the same length. The example shown in FIGS. 6A-1 and B-1 is also an example. As shown in the piezoelectric driven MEMS switch 70A shown in FIG. 6C, the upper electrode of the first cantilever 20 is used. A compressive stress film 72 may be provided on the upper electrode 18, and a compressive stress film 74 may be provided on the upper electrode 18 of the second cantilever 22.

In addition, this invention is not limited to the Example mentioned above, A various change can be added in the range which does not deviate from the summary of this invention. For example, the following are also included.
(1) The shapes and dimensions shown in the above embodiments are merely examples, and may be changed as appropriate. Similarly, the material can be appropriately changed as necessary.
(2) In the first and second embodiments, the hinge 26 is provided between the pair of cantilevers. However, the hinge 26 may be provided as necessary.
(3) The circuit configuration shown in the third embodiment is also an example, and as shown in the example shown in FIG. 8, the normally OFF switch of the present invention can be paralleled to be multistaged.
(4) In the above embodiment, the difference in the amount of warpage caused by the difference in length between the pair of cantilevers was used, but this is also an example. In addition to the length, dimensions (thickness, etc.) and materials (silicon, You may make it utilize the difference in the amount of curvature resulting from the difference in the stress of a metal, a piezoelectric member). In particular, metal and oxide thin film materials are known to exhibit various tensile stresses and compressive stresses depending on the materials, and the difference in stress between these materials may be positively utilized as shown in Example 4. .
(5) The materials of the compressive stress films 72 and 74 shown in the fourth embodiment are also examples, and various known materials may be used as long as the same effects can be obtained. Further, the formation ranges of the compressive stress films 72 and 74 may be changed as appropriate so as to achieve the same effect according to the length and size of the cantilever or the material.

  According to the present invention, the piezoelectric layer has electrode layers on the front and back surfaces thereof, and the other end side is supported in a cantilever shape on the substrate so that the one end sides face each other. In addition, signal lines and contact electrodes are formed. And, by switching on / off the connection between the contact electrode and the signal line using the warp of the cantilever, it is possible to suppress the variation of the structure caused by the warp and to obtain a stable electric characteristic, and to reduce the size. Therefore, it can be applied to the use of a piezoelectric drive type MEMS switch. In particular, it is suitable for switching the use frequency (especially for high frequency applications) of mobile communication devices typified by mobile phones.

10: Piezoelectric drive type MEMS switch 12: Substrate 14: Ground (lower electrode)
16: Piezoelectric layer 18: Upper electrode 20: First cantilever 22: Second cantilever 24: Contact electrode 26: Hinge 28, 30: Ground line 32, 34, 36: Signal line 34A, 36A: End 40: Hole 50: Piezoelectric drive type MEMS switch 52: First cantilever 54: Second cantilever 56: Contact electrode 58, 60: Signal line 60A: End portion 70, 70A: Piezoelectric drive type MEMS switch 72, 74: Compression stress Film 100: Piezoelectric drive MEMS switch 102: Substrate 104: Ground (lower electrode)
104A: Connection electrode 106: Hole 108: Signal line 110: Drive arm 110A: First cantilever 110B: Second cantilever 112: Piezoelectric layer 114: Upper electrode 114A: Connection electrode 116: Ground lines 118A, 118B: Hinge portion 120: contact 122: capacitance portion (or capacitor)
SW, SW1, SW2: Switch

Claims (8)

It has electrode layers on the front and back surfaces of the substantially plate-like piezoelectric layer, and is arranged so that one end side is cantilevered on the substrate and the other end faces each other, and warps. A pair of cantilevers with different quantities,
A first signal line formed on one cantilever so as to protrude from an end facing the other cantilever;
A second signal line formed on the other cantilever and connected to a contact electrode provided on the end facing the one cantilever;
With
A piezoelectric drive type MEMS switch, wherein the connection between the contact electrode and the first signal line is switched ON / OFF by utilizing the warp of at least one of the cantilevers. The difference in warpage between the pair of cantilevers is
2. The piezoelectric drive type MEMS switch according to claim 1, which is caused by a difference in stress of a material constituting the cantilever or a difference in size or weight of the cantilever.   3. The piezoelectric drive type MEMS switch according to claim 1, wherein opposite ends of the pair of cantilevers are connected via a hinge while allowing the warpage. 4. By forming the contact electrode and the second signal line on a cantilever with a small amount of warping, and forming the first signal line on a cantilever with a large amount of warping,
The contact electrode and the first signal line are in contact with each other in a no-voltage load state on the cantilever, and when the voltage is applied to the cantilever, the cantilever is warped in a direction opposite to the initial state and the contact electrode and the first signal line are in contact with each other. 4. The piezoelectric drive type MEMS switch according to claim 1, wherein a normally-on switch in which a line is separated is formed. By forming the contact electrode and the second signal line on a cantilever having a large amount of warping, and forming the first signal line on a cantilever having a small amount of warping,
The contact electrode and the first signal line are separated from each other in a no-voltage load state on the cantilever, and by applying a voltage to the cantilever, the cantilever is warped in the opposite direction to the initial state and the contact electrode and the first signal line 4. A normally-driven switch according to claim 1, wherein a normally-off switch is formed.   6. A piezoelectric drive type MEMS switch, wherein the piezoelectric drive type MEMS switch according to claim 4 is formed in a lump so as to include at least one of each of the piezoelectric drive type MEMS switches.   6. A piezoelectric drive type MEMS switch, wherein the piezoelectric drive type MEMS switch according to claim 4 and 5 is collectively formed to constitute an SPDT (single pole double throw) switch.   6. A piezoelectric drive type MEMS switch according to claim 5, wherein the piezoelectric drive type MEMS switch is multi-staged.

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