JP5314932B2 - Electric micro mechanical switch - Google Patents

Description

  The present invention relates to an electric micro mechanical system (MEMS).

  In an actuator in a conventional electric micromechanical device (MEMS), a driving arm serving as a driving unit of the actuator is supported on a substrate, and a positive voltage is applied to one of the substrate and an electrostatic electrode provided on the driving arm. By applying a negative voltage to the other electrostatic electrode, the driving arm is pulled toward the substrate side by using the electrostatic force generated thereby. Further, a configuration is known in which a piezoelectric arm layer and a piezoelectric driving electrode are provided on the driving arm, and the driving arm is pulled toward the substrate side using piezoelectric power.

For example, Japanese Patent Application Laid-Open No. 2005-302711 discloses an actuator that can be driven at a high speed with a low voltage, and a high-frequency switch using the actuator. Specifically, the actuator described in the publication includes a substrate having at least a surface insulation, a drive arm supported by at least one location on the substrate, and a static arm provided at a position facing the substrate and the drive arm. And a first voltage applying means for applying a voltage to the electrostatic electrode. The drive arm is further provided with piezoelectric drive electrodes having electrodes on the upper and lower surfaces of the piezoelectric layer, and second voltage application means for applying a voltage to the piezoelectric drive electrodes. In the high frequency switch described in the publication, the drive arm is driven up and down to control the connection between the connection electrode provided at the tip of the drive arm and the terminal electrode provided on the substrate. .
JP 2005-302711 A

  However, when the drive unit is formed by combining different materials, warpage occurs due to the stress of the material. In addition, it is difficult to control the amount of warpage to be constant, and variations in electrical characteristics (for example, drive voltage, high frequency characteristics, etc.) increase. For example, in the case of an electrical micro mechanical switch (hereinafter sometimes referred to as a MEMS switch) in which the drive arm is in contact with a signal line extending on the drive arm, the drive arm is warped downward. As a result, the distance between the signal line and the drive arm is increased, and the drive voltage must be increased accordingly.

  Therefore, an object of the present invention is to provide an electrical micromechanical switch that can suppress warping due to stress of a material and reduce variation in electrical characteristics.

  An electrical micromechanical switch according to the present invention includes a plate-like elastic body having one or both ends fixed to a substrate, a lower electrode formed on the upper surface of the elastic body, and a piezoelectric formed on the upper surface of the lower electrode. Body, a drive unit having an upper electrode formed on the upper surface of the piezoelectric body, a contact formed on a part of the drive unit, and a signal line having at least one end fixed to the substrate and extending on the contact And a locking portion joined to the substrate and configured of an insulator so as to support the driving portion. The drive unit can come into contact with the signal line through the contact, and the locking unit supports the drive unit from the side opposite to the signal line.

  In this way, for example, in a hole, a notch, or the like, if the locking portion supports the drive portion, warpage due to material stress can be suppressed. That is, the distance between the drive unit and the signal line can be kept constant, and variations in electrical characteristics can be reduced.

  Further, the driving unit described above may be driven so that the contact and the signal line are in contact with each other according to the piezoelectric body by a voltage applied to the lower electrode and the upper electrode.

  Further, the signal line described above may be extended on the contact point so as to have a twisted positional relationship with the drive unit.

  According to the present invention, it is possible to realize an electrical micromechanical switch that can suppress warping due to material stress and reduce variation in electrical characteristics.

FIG. 1 is a top view showing a configuration of an actuator which is a premise of the embodiment of the present invention. For example, a SiO ₂ insulating layer is formed on the surface of a Si substrate 1, and a ground 2 serving as a lower electrode layer of the piezoelectric layer is formed thereon. Furthermore, an upper electrode layer 6 of a piezoelectric layer is formed on the ground 2. The same hatching indicates the same layer. The drive arm 8 includes a contact 8c that contacts the signal lines 3a and 3b, a first cantilever 8a that is connected to the contact 8c via the hinge 8d, and a second that is connected to the contact 8c via the hinge 8e. The cantilever 8b is provided so as to bridge the hole 5. In the hinge portions 8d and 8e, a hole is formed in order to effectively perform the function of the hinge.

  One end of the signal line 3 a is supported by the substrate 1 and extends so as to cover a part of the contact 8 c and a part of the hole 5. And the front-end | tip part (opposite side of a support part) of the signal wire | line 3a is formed so that a width | variety may become narrow gradually. Similarly, the signal line 3 b is supported at one end by the substrate 1 and extends so as to cover a part of the contact 8 c and a part of the hole 5. And the front-end | tip part (opposite side of a support part) of the signal wire | line 3b is formed so that a width | variety may become narrow gradually. The signal lines 3a and 3b are formed so as to have a twisted relationship with the drive arm 8. Further, the signal line 3a and the signal line 3b are cut on the contact point 8c and are vertically symmetrical. In addition, on the left and right of the signal lines 3a and 3b, ground lines 7a and 7b are formed in parallel with the signal lines 3a and 3b so as to bridge the drive arm 8 and the hole 5.

FIG. 2A is a schematic cross-sectional view taken along the line AA ′ in the top view (FIG. 1). The drive arm 8 includes a part of layers 1a, 1b and 1c of the substrate 1 functioning as an elastic layer, grounds 2a, 2b and 2c, piezoelectric layers 4a, 4b such as PZT (Pb (ZrTi) O ₃ ), and the like. 4c and upper electrode layers 6a, 6b and 6c. The drive arm 8 includes a first layer 1a of the substrate 1, a ground 2a, a piezoelectric layer 4a, an upper electrode layer 6a, a first cantilever 8a, and a partial layer of the substrate 1. 1b, a ground 2b, a piezoelectric layer 4b, a second cantilever 8b composed of an upper electrode layer 6b, a partial layer 1c of the substrate 1, a ground 2c, a piezoelectric layer 4c, and an upper portion The contact layer 8c is composed of the electrode layer 6c. The first cantilever 8a and the contact 8c are connected by a hinge portion 8d formed between a part of the layer 1a and the ground 2a of the substrate 1 and a part of the layer 1c and the ground 2c of the substrate 1. Yes. That is, the upper electrode layer and the piezoelectric layer are cut. Similarly, the second cantilever 8b and the contact 8c are a hinge portion 8e formed between a part of the layer 1b and the ground 2b of the substrate 1 and a part of the layer 1c and the ground 2c of the substrate 1. It is connected. Again, the upper electrode layer and the piezoelectric layer are cut. Further, the signal lines 3a and 3b (the signal line 3a is not shown in the cross-sectional view along the line AA ′) extend on the contact 8c.

  Then, by applying a voltage to the first and second cantilevers 8a and 8b, the drive arm 8 is driven, and the contact 8c and the signal lines 3a and 3b are brought into contact with each other. Specifically, the drive arm 8 is pulled up by applying a negative voltage to the ground layers 2a and 2b and applying a positive voltage to the upper electrode layers 6a and 6b. When the actuator is a switch, the contact 8c and the signal lines 3a and 3b are brought into contact with each other to conduct. The contact 8c comes into contact with the signal lines 3a and 3b in an appropriate manner by the hinge portions 8d and 8e.

  However, since the first and second cantilevers 8a and 8b are warped, the entire drive arm 8 is warped as shown in FIG. Therefore, the distance between the signal lines 3a and 3b and the contact 8c increases by the amount of warp M. For example, in a cantilever having a length of 500 μm, warpage of several tens to hundreds of μm occurs. For example, when a warp of about several tens of μm occurs, a voltage of several tens of volts is required to return to the original position.

  Therefore, in the embodiment of the present invention, a configuration as shown in FIG. 3 is adopted. Embodiments of the present invention will be described below.

  FIG. 3 is a cross-sectional view taken along the line A-A ′ of FIG. 1. The top view is basically the same as that shown in FIG. In FIG. 3, a locking portion 9, which is an insulator such as glass, is provided under the substrate 1 so as to support the drive arm 8 from below (that is, from the side opposite to the signal lines 3 a and 3 b). . The locking portion 9 is joined to the substrate 1 and has a protruding portion 9a at a portion below the contact 8c. That is, the locking part 9 is formed in a convex shape. The protrusion 9a supports the contact 8c from below to suppress warpage of the entire drive arm 8. The protrusion 9a and the contact 8c are not joined, and when the drive arm 8 is driven, the contact 8c is separated from the protrusion 9a. Since the mechanism for driving the drive arm 8 is the same as the mechanism described above, the description thereof is omitted here. By providing such a locking portion 9, it is possible to suppress warping due to material stress. That is, the distance between the signal lines 3a and 3b and the contact 8c can be kept constant, and variations in electrical characteristics can be reduced.

  Next, a manufacturing method of the MEMS switch as shown in FIG. 3 will be described with reference to FIGS. 4 to 8, the cross-sectional view A shown on the left side is a cross-sectional view taken along the line AA 'in FIG. 1, and the cross-sectional view B shown on the right side is a cross-sectional view taken along the line BB' in FIG. Indicates.

Figure 4 As shown in (a), Si layer 101 on the surface, the SiO ₂ layer 102 below the Si layer 101 on the surface and SOI (Silicon On the Si layer 103 is formed under the SiO ₂ layer 102, Insulator) wafer is used. Then, as shown in FIG. 4B, the SiO ₂ layers 104 and 105 are formed by thermally oxidizing the upper and lower surfaces of the SOI wafer in a water or oxygen atmosphere. This SiO ₂ layer 104 is an insulating layer on the surface of the substrate 1 shown in FIG. Thereafter, as shown in FIG. 4C, a Pt / Ti layer 106 which becomes a lower electrode layer of the piezoelectric layer is formed on the SiO ₂ layer 104 by sputtering.

  Then, as shown in FIG. 4D, the SOI wafer is rotated, and the PZT sol-gel film is formed by about 1 μm to form the PZT piezoelectric layer 107 on the Pt / Ti layer 106. Next, as shown in FIG. 4 (e), a Pt / Ti layer 108 to be the upper electrode of the piezoelectric layer is formed again on the PZT piezoelectric layer 107 by sputtering. Up to this point, both the sectional view A and the sectional view B remain unchanged.

  Next, a photoresist is applied, exposed through a photomask, exposed, developed, and unnecessary portions of the resist are removed. As shown in FIG. 5A, the Pt / Ti layer 108 and A resist layer 109 for etching the PZT piezoelectric layer 107 is formed. If the photoresist to be used is a positive resist, the exposed portion is removed. If the photoresist is a negative resist, the unexposed portion is removed as an unnecessary portion. In the sectional view A, two grooves 110a and 110b are formed to cut the first and second cantilevers 8a and 8b and the contact 8c. On the other hand, in the cross-sectional view B, the resist layer 109 is formed only at one location so as to leave only the contact 8c portion.

  Then, as shown in FIG. 5B, the Pt / Ti layer 108 and the PZT piezoelectric layer 107 where the resist layer 109 is not formed are etched away, and then the resist layer 109 is removed. Next, a photoresist is applied, exposed through a photomask, exposed, developed, and unnecessary portions of the resist are removed. As shown in FIG. 5C, the lower electrode layer Pt is formed. / A resist layer 111 for etching the Ti layer 106 is formed. In the cross-sectional view A, the resist layer 111 is formed on the entire upper surface. In the cross-sectional view B, the resist layer 111 is formed only at one location so as to leave only the contact 8c.

Then, as shown in FIG. 5D, the Pt / Ti layer 106 where the resist layer 111 is not formed is removed by etching, and then the resist layer 111 is removed. Next, in order to process the SiO ₂ layer 104, the Si layer 101, and the SiO ₂ layer 102, a photoresist is applied, exposed through a photomask, the exposed resist is developed, and unnecessary portions are developed. The resist is removed, and a resist layer 112 is formed as shown in FIG. In the sectional view A, the resist layer 112 is formed on the entire upper surface, but in the sectional view B, two grooves 113a and 113b are formed to separate the contact 8c.

Thereafter, as shown in FIG. 6A, the portions of the SiO ₂ layer 104, the Si layer 101, and the SiO ₂ layer 102 where the resist layer 112 is not formed are removed by etching, and then the resist layer 112 is removed. Removed. The description of the hinge portions 8d and 8e is omitted here. In order to form the hinge portions 8d and 8e, it is necessary to appropriately form a portion where the resist is not formed in the cross-sectional view A in the stage of FIGS. 5C and 5E.

  Next, as a pre-stage for forming the Au signal lines 3a and 3b, as shown in FIG. 6B, a filling resist 114 is applied to the grooves 110a and 110b and the grooves 113a and 113b. Then, in order to form the signal lines 3a and 3b, a photoresist is applied, exposed through the photomask, exposed, the exposed resist is developed, and unnecessary portions of the resist are removed. As shown, a sacrificial layer 115 is formed. The sacrificial layer 115 has a thickness for realizing the length L shown in FIG. Thereafter, as shown in FIG. 6D, an Au layer 116 is formed on the sacrificial layer 115 by sputtering.

  Then, a photoresist is applied, exposed through a photomask and exposed, the exposed resist is developed, and unnecessary portions of the resist are removed to form a resist layer 117 as shown in FIG. In the cross-sectional view A, only the Au layer 116a of the Au layer 116 is used as a signal line, so the resist layer 117 is formed only on the Au layer 116a. On the other hand, in the sectional view B, a groove 118 is formed in order to separate the signal line 3a and the signal line 3b. Thereafter, as shown in FIG. 7B, the Au layer 116 where the resist layer 117 is not formed is etched away by etching.

Next, a photoresist is applied under the SiO ₂ layer 105 on the back surface, exposed through a photomask, developed, and the exposed resist is developed. Unnecessary portions of the resist are removed, and FIG. As shown, a resist layer 119 is formed. Then, etching is performed from below, and as shown in FIG. 7D, the SiO ₂ layer 105, the Si layer 103, and the SiO ₂ layer 102 in the portion where the resist layer 119 is not formed are scraped off.

After that, when the embedding resist 114, the sacrificial layer 115, the resist layer 117, and the resist layer 119 are removed and supercritical drying is performed, as shown in FIG. Is formed. On the other hand, the glass 120 to be the locking portion 9 is finely processed. In order to keep the distance between the signal lines 3a and 3b and the contact 8c constant with high accuracy, it is necessary to precisely process the height of the protrusion 9a of the locking portion 9, and this processing includes fine processing such as dry etching. Use technology. Then, a glass 120, when joining the contact portion 121 of the SiO ₂ layer 105, as shown in FIG. 8 (b), is completed. In addition, in order to join the board | substrate 1 and the latching | locking part 9, techniques, such as anodic bonding, are used. As shown in FIG. 8B, a protrusion 9a is formed under the contact 8c so as to support the drive arm 8 as a whole.

  By performing the manufacturing process as described above, the MEMS switch as shown in FIG. 3 can be manufactured. In addition, about parts other than the latching | locking part 9, it can manufacture by applying the manufacturing process of a presupposed actuator as it is. In addition, each layer described above has a thickness of nm level unless otherwise touched.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this. For example, the fine structure does not have to be all the same. Other hinge structures can be adopted as the structure of the hinge portion.

  In the above description, the structure in which the signal line and the drive arm are twisted is described as an example, but the positional relationship between the signal line and the drive arm is not limited to this. Other structures may be employed as long as the tip of the signal line overlaps with the drive arm. Furthermore, in the above description, a structure in which a hole is provided in the substrate has been described as an example, but the hole does not necessarily have to be configured. For example, a notch may be provided. Moreover, if it is a structure which supports a drive arm, it is also possible to change a latching | locking part into another structure.

It is a top view of the actuator used as a premise. (A) thru | or (b) is a schematic sectional drawing of the actuator used as a premise. It is a schematic sectional drawing of the MEMS switch which concerns on one embodiment of this invention. (A) thru | or (e) is a figure which shows the manufacturing method of a MEMS switch. (A) thru | or (e) is a figure which shows the manufacturing method of a MEMS switch. (A) thru | or (d) is a figure which shows the manufacturing method of a MEMS switch. (A) thru | or (d) is a figure which shows the manufacturing method of a MEMS switch. (A) thru | or (b) is a figure which shows the manufacturing method of a MEMS switch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Ground 3a, 3b Signal line 4 Piezoelectric layer 5 Hole 6 Upper electrode layer 7a, 7b Ground line 8 Drive arm 8a 1st cantilever 8b 2nd cantilever 8c Contact 8d, 8e Hinge part 9 Locking part

Claims (2)

A plate-like elastic body having one or both ends fixed to the substrate, a lower electrode formed on the upper surface of the elastic body, a piezoelectric body formed on the upper surface of the lower electrode, and an upper surface of the piezoelectric body. A drive unit having an upper electrode;
A contact formed on a part of the drive unit;
A signal line having at least one end fixed to the substrate and extending on the contact;
A locking portion joined to the substrate and configured of an insulator so as to support the driving portion;
Have
The drive unit can come into contact with the signal line via the contact point,
The locking part is adapted to support the driving part from the side opposite to the signal line ,
The driving unit is driven by the voltage applied to the lower electrode and the upper electrode so that the contact and the signal line are in contact with each other according to the piezoelectric body,
The electrical micromechanical switch characterized in that the locking portion maintains a constant distance between the contact and the signal line when no voltage is applied to the lower electrode and the upper electrode . The electrical micro mechanical switch according to claim 1, wherein the signal line extends on the contact so as to have a twisted positional relationship with the drive unit.

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