JP2011023468A - Varactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a varactor capable of sufficiently shortening a distance between a movable electrode and a fixed electrode, even if the movable electrode warps. <P>SOLUTION: Each fixed electrode 10 of the varactor 1 is disposed in a region facing a circle C inscribed with a square of the movable electrode 8 on an upper surface 2A of a substrate 2, and the fixed electrode 10 is not disposed in a region facing each vertex 8A of the movable electrode 8. In addition, an extraction electrode 11 connected with the fixed electrode 10 is disposed to cross a center of one of sides of the square of the movable electrode 8 in a plan view. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a variable-capacitance element that is suitably used as a variable-capacitance switch that performs a switching operation on a high-frequency signal or the like, for example, by changing an electrostatic capacity, or a variable-capacitance capacitor.

  In general, the variable capacitance element is used as, for example, a variable capacitance switch, a variable capacitance capacitor, or the like. Such a variable capacitance element has a movable electrode provided on a support portion provided on a substrate so as to be displaceable in a thickness direction via a support beam, and is opposed to the movable electrode provided on an upper surface of the substrate via a space. And a fixed electrode disposed at a position to be fixed. In this case, for example, the movable electrode is displaced in the thickness direction by an electrostatic force, thereby changing the distance between the movable electrode and the fixed electrode and changing the capacitance between the two electrodes (for example, Patent Documents). 1).

  In many cases, the movable electrode is formed in a flat plate shape having a square shape in plan view, and the fixed electrode has the same shape and size as the plan view shape of the movable electrode in order to increase the capacitance between the movable electrode and the movable electrode. Is formed. Further, the movable electrode and the fixed electrode are very close to each other, and when the movable electrode is displaced and comes closest to the fixed electrode, the distance between the two is less than 1 μm, for example. As described above, the movable electrode and the fixed electrode are formed in the same shape and size, face each other, and the distance between the two electrodes is reduced, thereby increasing the capacitance value.

JP 2006-147995 A

  By the way, the movable electrode of the variable capacitance element as described above is formed by a film forming technique such as plating, CVD, or vapor deposition. When the movable electrode is formed by such a film forming technique, the movable electrode may be warped due to the internal stress of the film forming the movable electrode.

  The warp of the movable electrode tends to be larger in the peripheral portion than in the central portion. In particular, in the case of a movable electrode having a square shape in plan view, the warp tends to increase at the apex portion of the square, that is, the four corners due to its structure.

  For example, in the case of a movable electrode having a square shape in plan view, when its four corners warp in the direction approaching the fixed electrode, if the movable electrode is brought closer to the fixed electrode, the central portion of the movable electrode is not sufficiently close to the fixed electrode. In addition, the four corners of the movable electrode may come into contact with the fixed electrode. For this reason, in order to avoid contact of the four corners of the movable electrode with the fixed electrode, the distance between the movable electrode and the fixed electrode cannot be reduced, and as a result, the capacitance value between the two electrodes must be increased. Becomes difficult.

  Moreover, the electrostatic capacitance value between a movable electrode and a fixed electrode varies because the curvature of the movable electrode as described above varies. For this reason, it becomes difficult to increase the accuracy of the variable capacitance element.

  The present invention has been made in view of, for example, the problems described above, and an object of the present invention is to sufficiently reduce the distance between the movable electrode and the fixed electrode even when the movable electrode is warped. An object of the present invention is to provide a variable capacitance element that can be used.

  The present invention includes a substrate, a support portion provided on the substrate, a movable electrode supported by the support portion so as to be displaceable in a thickness direction via a support beam, and the movable member provided on an upper surface of the substrate. The present invention is applied to a variable capacitance element including an electrode and a fixed electrode arranged so as to face each other through a space.

  In order to solve the above-mentioned problem, the feature of the configuration adopted by the invention according to claim 1 is that the movable electrode has a polygonal shape in plan view, and the fixed electrode is formed on the upper surface of the substrate. It exists in the area | region which opposes a movable electrode, Comprising: It provided in the area | region which opposes the circle | round | yen or ellipse inscribed in the polygon of the said movable electrode.

  In the invention according to claim 2, the movable electrode is formed using a plating layer formed by plating.

  In the variable capacitor according to a third aspect of the present invention, the shape of the fixed electrode in plan view is circular or elliptical.

  A variable capacitance element according to a fourth aspect of the present invention is provided on the upper surface of the substrate, and includes an extraction electrode for electrically connecting the fixed electrode and an external circuit, and the extraction electrode is in a plan view. The movable electrode is arranged so as to intersect with the center position of one side of the polygon of the movable electrode.

  According to the first aspect of the present invention, since the fixed electrode is provided in a region facing the circle or ellipse inscribed in the polygon of the movable electrode on the upper surface of the substrate, the fixed electrode faces the vertex of the polygon of the movable electrode. It can be avoided that fixed electrodes are arranged in the region. That is, the fixed electrode can be arranged except for the apex portion (corner corner portion) of the polygon of the movable electrode that causes a large warp. As a result, even when the movable electrode is warped, it is possible to avoid the apex portion or the peripheral portion of the movable electrode from contacting the fixed electrode, and the distance between the movable electrode and the fixed electrode can be reduced. . Therefore, the capacitance value between the movable electrode and the fixed electrode can be increased.

  In addition, the central portion of the movable electrode has a relatively small degree of warpage or a small degree of variation in warpage compared to the peripheral portion. For this reason, it is possible to suppress variation in the capacitance value between the movable electrode and the fixed electrode due to variations in the warp of the movable electrode, and it is possible to increase the accuracy of the variable capacitance element.

  According to the second aspect of the present invention, since the movable electrode is formed using the plating layer, the central portion excluding the corner portion of the movable electrode can be formed in a flat shape with little warpage. As a result, the central portion of the movable electrode is displaced in the thickness direction in a state where the entire central portion of the movable electrode is parallel to the fixed electrode, so that the entire central portion of the movable electrode can be brought close to the fixed electrode. The capacitance value between the two can be increased. In addition, since the central portion of the movable electrode is less likely to vary in warpage over the entire portion, it is possible to suppress variation in the capacitance value between the movable electrode and the fixed electrode from element to element.

  According to the third aspect of the present invention, the fixed electrode is not opposed to the apex portion of the movable electrode having a polygonal shape in plan view on the upper surface of the substrate by making the shape of the fixed electrode in plan view circular or elliptical. Can be arranged as follows. As a result, the fixed electrode can be opposed across the entire central portion of the movable electrode with less warping, and the area of the movable electrode and the fixed electrode can be increased in a state where the influence of the warp is reduced, thereby The capacity value can be increased.

  According to the fourth aspect of the present invention, it is possible to dispose the extraction electrode while avoiding a region facing the polygonal apex portion of the movable electrode, which tends to generate a large warp on the upper surface of the substrate. Thereby, since the extraction electrode is arranged in a region where the warp is small in the movable electrode, the distance between the movable electrode and the fixed electrode can be reduced in a state where the movable electrode and the extraction electrode are not short-circuited.

It is a longitudinal cross-sectional view which shows the variable capacitance element by embodiment of this invention. FIG. 2 is a cross-sectional view of the variable capacitance element as viewed from the direction of arrows II-II in FIG. 1. FIG. 3 is a cross-sectional view of the variable capacitance element as viewed from the direction of arrows III-III in FIG. 1. FIG. 4 is a cross-sectional view of the variable capacitance element viewed from the direction of arrows IV-IV in FIG. 1. It is a longitudinal cross-sectional view which shows the state which applied the drive voltage to the variable capacitance element in FIG. It is explanatory drawing which shows the arrangement | positioning relationship in the planar view of a movable electrode and a fixed electrode. FIG. 7 is an explanatory diagram showing a case where a movable electrode and a fixed electrode are viewed from the direction of arrows VII-VII in FIG. 6, and warping occurs at four corners of the movable electrode. It is explanatory drawing which shows the modification of a fixed electrode. It is explanatory drawing which shows the other modification of a fixed electrode. It is an explanatory view showing the arrangement relation in the plane view of the movable electrode and the fixed electrode according to the first comparative example. FIG. 11 is an explanatory diagram showing a case where the movable electrode and the fixed electrode are viewed from the direction of arrows XI-XI in FIG. 10 and warping occurs at the four corners of the movable electrode. FIG. 12 is an explanatory view similar to FIG. 11, showing a case where the movable electrode and the fixed electrode according to the second comparative example are warped at the four corners of the movable electrode.

  Hereinafter, variable capacitance elements according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  In FIG. 1, the variable capacitance element 1 according to the embodiment of the present invention includes a functional layer 3 provided on a first substrate 2 and a second substrate 5 provided on the functional layer 3 via a sealing frame 4. It is configured. The substrate 2, the functional layer 3, and the substrate 5 extend in the horizontal direction along the X axis and the Y axis when the three axis directions orthogonal to each other are taken as the X axis, the Y axis, and the Z axis.

  The substrates 2 and 5 are formed of, for example, an insulating glass material or the like, and are formed in a square shape with a side of about several millimeters.

  Two fixed electrodes 10 and extraction electrodes 11 are provided on the upper surface 2A of the first substrate 2 (see FIG. 3), and the first substrate 2 has a through electrode penetrating the substrate 2 in the Z-axis direction. 15 and 16 are formed (see FIG. 3). Further, a plurality of stoppers 13 are formed on the upper surface 2A of the substrate 2. The fixed electrode 10, the extraction electrode 11, the through electrodes 15, 16 and the stopper 13 will be described in detail later.

  A drive electrode 12 is provided on the lower surface 5A of the substrate 5 and a plurality of stoppers 14 are formed. The substrate 5 is formed with through electrodes 17 and 18 that penetrate the substrate 5 in the Z-axis direction. The drive electrode 12, the stopper 14, and the through electrodes 17 and 18 will be described in detail later.

  The functional layer 3 is made of a conductive metal material such as copper (Cu), and is formed as a plating layer formed by plating. In the functional layer 3, a support portion 7, a movable electrode 8, and a support beam 9 described later are formed.

  The sealing frame 4 is disposed between the functional layer 3 and the second substrate 5 and is formed in a substantially rectangular frame shape along the outer peripheral edge of the substrate 5. The sealing frame 4 is formed using a conductive metal material such as an alloy containing gold (Au) or gold, and is bonded to the substrate 5 and the support portion 7 of the functional layer 3, respectively. As a result, the sealing frame 4 forms an accommodation space 6 for accommodating the movable electrode 8, the support beam 9, the fixed electrode 10, the drive electrode 12, and the like between the substrates 2 and 5, and makes the accommodation space 6 airtight. It is sealed.

  Further, a bonding film 4A made of a metal film such as platinum / chromium (Pt / Cr) is provided between the sealing frame 4 and the substrate 5 in order to bond the sealing frame 4 to the substrate 5. Yes. On the other hand, a pressure-bonding film 4B made of a conductive metal film such as an alloy containing gold (Au) or gold is provided on the surface of the functional layer 3 at a position facing the sealing frame 4. The sealing frame 4 is bonded to the pressure-bonding film 4 </ b> B by thermocompression bonding and is fixed to the functional layer 3 and the substrate 5.

  The support portion 7 is formed on the functional layer 3 and is fixed together with the sealing frame 4 between the substrates 2 and 5. The support portion 7 is formed, for example, in a rectangular frame shape extending along the peripheral edges of the substrates 2 and 5 and surrounds the movable electrode 8, the support beam 9, and the like. In addition, two beam connecting portions 7A located on both sides in the X-axis direction with the movable electrode 8 interposed therebetween are provided inside the support portion 7. The support portion 7 has a thickness dimension of about several μm to several tens of μm (for example, 10 μm), and forms an accommodation space 6 between the substrates 2 and 5 together with the sealing frame 4.

  The movable electrode 8 is formed on the functional layer 3 and supported by the support portion 7 via the support beam 9 so as to be displaceable in the Z-axis direction (thickness direction). The movable electrode 8 is disposed on the center side of the substrates 2 and 5. Further, the movable electrode 8 is formed in a flat plate shape, for example, in a plan view, and the length of one side thereof is set to, for example, about several tens to several hundreds μm. Furthermore, the movable electrode 8 has a thickness dimension smaller than the support portion 7 by, for example, about 0.1 μm to 0.2 μm.

  The movable electrode 8 is connected to the support beam 9 at the apex portion 8A, and is displaced in the Z-axis direction by an electrostatic force (electrostatic attractive force) generated between the movable electrode 8 and the drive electrode 12, and approaches the fixed electrode 10. , Separated. The movable electrode 8 is held at a position close to the fixed electrode 10 by the support beam 9 when no driving voltage is applied to the driving electrode 12.

  In addition, a through hole 8 </ b> B that penetrates in the thickness direction is provided at the center of the movable electrode 8. The through-hole 8B removes a sacrificial layer (not shown) provided between the substrate 2 and the movable electrode 8 when the movable electrode 8 is formed, and at the same time, the movable electrode 8 is displaced in the thickness direction. Sometimes it reduces the resistance caused by the surrounding gas. A plurality of through holes 8B may be provided in the movable electrode 8. Further, the movable electrode 8 may be configured to omit the through hole 8B.

  The support beams 9 support the movable electrode 8 so as to be displaceable in the Z-axis direction. For example, four support beams 9 are provided between the movable electrode 8 and the support portion 7 as shown in FIG. These support beams 9 are formed, for example, as beams bent in a crank shape, and are positioned between the substrates 2 and 5 and extend in a direction (horizontal direction) parallel to a plane including the X axis and the Y axis. It is separated from the substrates 2 and 5 in the Z-axis direction (vertical direction).

  Each support beam 9 is connected to the beam connecting portion 7 </ b> A of the support portion 7 on the base end side and connected to each vertex portion 8 </ b> A that is the four corners of the movable electrode 8 on the distal end side. As shown in FIG. 5, the support beam 9 is twisted or bent in the Z-axis direction when the movable electrode 8 is displaced toward the substrate 5.

  As shown in FIG. 3, two fixed electrodes 10 are provided on the upper surface 2 </ b> A of the substrate 2. These fixed electrodes 10 are arranged in the Y-axis direction and are separated from each other. Any fixed electrode 10 is arranged so as to face the movable electrode 8 with a space in between. Each fixed electrode 10 is formed of a conductive metal thin film, for example, and has a substantially semicircular shape in plan view.

  The fixed electrode 10 is electrically connected to the through electrodes 15 and 16 formed through the substrate 2 in the Z-axis direction via the extraction electrodes 11. The extraction electrode 11 is provided on the upper surface 2A of the substrate 2 and is formed of a linear metal film having conductivity.

  Here, FIG. 6 shows an arrangement relationship between the movable electrode 8 and the fixed electrode 10 in a plan view (when the movable electrode 8 or the like is viewed from directly above).

  As shown in FIG. 6, each fixed electrode 10 is in a region facing the movable electrode 8 on the upper surface 2 </ b> A of the substrate 2, and is opposed to the rectangular vertex of the movable electrode 8 and its peripheral portion, that is, the vertex portion 8 </ b> A. It is provided in an area other than the area to be used. Specifically, each fixed electrode 10 is arranged in a circular region facing the circle C inscribed in the square of the movable electrode 8 on the upper surface of the substrate 2 as indicated by a two-dot chain line in FIG. Yes.

  Furthermore, the extraction electrode 11 is disposed so as to intersect with the center position of one side of the square of the movable electrode 8 in plan view. Specifically, one end of the extraction electrode 11 is connected to the fixed electrode 10 at a position below the central portion of one side of the square of the movable electrode 8.

  For each fixed electrode 10 having such an arrangement relationship with the movable electrode 8, a high frequency signal of, for example, about several hundred kHz to several GHz is provided from an external signal circuit via the through electrodes 15 and 16 and the extraction electrode 11. Is entered. In this case, the fixed electrode 10 on the upper side (one side in the Y-axis direction) and the movable electrode 8 in FIG. 3 and the fixed electrode 10 and the movable electrode 8 on the lower side (other side in the Y-axis direction) in FIG. Between these, two capacitors (air gap capacitors) connected in series via the movable electrode 8 are formed. The overall capacitance of these capacitors, that is, the capacitance between the two fixed electrodes 10 changes according to the distance between each fixed electrode 10 and the movable electrode 8.

  The drive electrode 12 is provided on the lower surface 5A of the substrate 5 and is disposed at a position facing the movable electrode 8 with a space in between. The drive electrode 12 is formed of, for example, the same conductive metal thin film as the bonding film 4A.

  Here, the drive electrode 12 is electrically connected to the through electrode 17 penetrating the substrate 5 in the Z-axis direction, and a drive voltage composed of, for example, a positive DC voltage is applied. On the other hand, the movable electrode 8 is electrically connected to another through electrode 18 that penetrates the substrate 5 in the Z-axis direction via the support beam 9 and the sealing frame 4, and is connected to, for example, the ground. As a result, an external drive circuit is electrically connected to the through electrodes 17 and 18, a drive voltage is applied between the drive electrode 12 and the movable electrode 8, and an electrostatic is applied between the drive electrode 12 and the movable electrode 8. An attractive force is generated, and the movable electrode 8 can be displaced in a direction approaching the drive electrode 12 (Z-axis direction).

  That is, in an initial state where no drive voltage is applied between the drive electrode 12 and the movable electrode 8, the movable electrode 8 is held at a position close to the fixed electrode 10 by the support beam 9, and the movable electrode 8, the fixed electrode 10, A narrow gap G1 having a small interval dimension is formed between them.

  In a driving state in which a driving voltage is applied between the driving electrode 12 and the movable electrode 8, the movable electrode 8 is attracted to the driving electrode 12 by an electrostatic attraction acting between them. As a result, as shown in FIG. 5, the movable electrode 8 is displaced in the Z-axis direction so as to approach the drive electrode 12, and as a result, moves away from the fixed electrode 10. At this time, a wide gap G 2 having a large gap is formed between the movable electrode 8 and the fixed electrode 10.

  On the other hand, a plurality of stoppers 13 are provided in a protruding manner at positions facing the movable electrode 8 on the upper surface 2 </ b> A of the substrate 2. Each stopper 13 is formed of a material having an insulating property like the substrate 2. The stopper 13 serves to support the movable electrode 8 in the initial state. That is, in the initial state where no drive voltage is applied between the drive electrode 12 and the movable electrode 8, the movable electrode 8 comes into contact with the tip of the stopper 13, and thereby, between the movable electrode 8 and the fixed electrode 10. The narrow gap G1 is ensured with high accuracy.

  A plurality of stoppers 14 are provided so as to protrude from the lower surface of the substrate 5 at a position facing the movable electrode 8. Each stopper 14 is formed of a material having an insulating property like the substrate 5. The stopper 14 serves to prevent contact between the movable electrode 8 and the drive electrode 12 in the drive state. That is, in a driving state in which a voltage is applied between the driving electrode 12 and the movable electrode 8, the movable electrode 8 is attracted in a direction approaching the driving electrode 12 by the electrostatic attraction generated between the two, and the tip end portion of the stopper 14. Abut. Thereby, the contact between the movable electrode 8 and the drive electrode 12 is prevented.

  The through electrodes 15 and 16 are formed through the substrate 2 in the Z-axis direction. The through-electrodes 15 and 16 are formed by filling a through-hole formed in the substrate 2 with a conductive metal material, and serve to electrically connect the fixed electrode 10 and an external signal circuit.

  The through electrodes 17 and 18 are formed through the substrate 5 in the Z-axis direction. The through-electrodes 17 and 18 are formed by filling a through-hole formed in the substrate 5 with a conductive metal material, and serve to electrically connect the movable electrode 8 and an external drive circuit.

  Next, a method for manufacturing the variable capacitance element 1 will be described. First, a plurality of stoppers 13 are formed on the upper surface 2A of the substrate 2 made of a glass material by, for example, etching. Subsequently, a through hole is formed in the substrate 2 by using laser processing, a microblast method or the like, and then a conductive metal material such as copper is filled in the through hole by, for example, plating, and the through electrodes 15 and 16 are formed. Form. Further, the fixed electrode 10 and the extraction electrode 11 which are conductive metal thin films such as gold are provided on the upper surface 2A of the substrate 2 by using, for example, sputtering or vapor deposition.

Next, after a sacrificial layer made of, for example, titanium (Ti), silicon oxide (SiO ₂ ), or the like is formed on the upper surface 2A of the substrate 2 at a position corresponding to the movable electrode 8 and the support beam 9, the substrate including the sacrificial layer is formed. A seed layer is formed on the entire top surface of 2 using a conductive metal material such as copper. The seed layer is a thin film having a thickness of, for example, 0.1 μm or less, and serves as a basic part when performing a plating process.

  Next, a mold for forming the support portion 7, the movable electrode 8, the support beam 9, and the like is formed on the upper surface of the seed layer using a mold material (for example, a photoresist material) that inhibits the growth of plating.

  Next, a plating process is performed on the upper surface of the seed layer to grow a plating layer made of a conductive metal material such as copper, and then the mold is removed. At this time, in order to reduce the stress acting on the inside of the plated layer, the plated layer is annealed. Thereafter, the upper surface of the plating layer is polished in a flat state by using, for example, a CMP (Chemical Mechanical Polishing) method. Thereby, the functional layer 3 provided with the support part 7, the movable electrode 8, the support beam 9, etc. is formed.

  Next, a pressure-bonding film 4B made of a metal thin film such as gold (Au) is formed on the upper surface of the support portion 7 by using, for example, vapor deposition or sputtering.

  Next, the sacrificial layer is removed by etching using thin hydrofluoric acid, for example, and then an unnecessary seed layer is removed using thin sulfuric acid. Thereby, the movable electrode 8 is released from the substrate 2 and can be displaced in the thickness direction.

  On the other hand, the plurality of stoppers 14 are formed by, for example, etching the lower surface 5A of the substrate 5 made of a glass material. Subsequently, after a through hole penetrating in the thickness direction is formed in the substrate 5, a conductive metal material such as copper is filled in the through hole to form the through electrodes 17 and 18. Further, the bonding film 4A and the drive electrode 12 which are conductive metal thin films such as gold are formed on the lower surface 5A of the substrate 5 by using, for example, sputtering or vapor deposition. Further, the sealing frame 4 made of a metal thin film such as gold (Au) is formed on the lower surface 5A of the substrate 5 at a position corresponding to the bonding film 4A using, for example, vapor deposition or sputtering.

  Next, the sealing frame 4 and the pressure-bonding film 4B are thermocompression bonded. As a result, a sealed housing space 6 that houses the movable electrode 8, the support beam 9, the fixed electrode 10, the drive electrode 12, and the like is formed between the substrate 2 and the substrate 5.

  The variable capacitance element 1 according to the present embodiment is manufactured by the above-described manufacturing method, and the operation thereof will be described next.

  First, in an initial state where no voltage is applied between the movable electrode 8 and the drive electrode 12, the movable electrode 8 is held at a position close to the fixed electrode 10 as shown in FIG. The capacitance between the electrode 10 and the electrode 10 is a maximum capacitance value corresponding to the interval dimension of the narrow gap G1 between the movable electrode 8 and the fixed electrode 10.

  Further, as shown in FIG. 4, in a driving state in which a voltage is applied between the movable electrode 8 and the driving electrode 12, an electrostatic attractive force is generated between them. At this time, the movable electrode 8 is displaced in the vertical direction to a position where it comes into contact with the stopper 14 while bending and deforming the support beam 9, and the movable electrode 8 is held at a position separated from the fixed electrode 10. As a result, the electrostatic capacitance between the movable electrode 8 and the fixed electrode 10 becomes a minimum capacitance value corresponding to the distance dimension of the wide gap G2 between the movable electrode 8 and the fixed electrode 10 which are separated from each other.

  Thus, the variable capacitance element 1 can switch the electrostatic capacitance between the movable electrode 8 and the fixed electrode 10 according to the presence or absence of voltage application. The variable capacitance element 1 that performs such an operation can be used as a switch element that switches between transmission and interruption of a high-frequency signal between the two fixed electrodes 10 in accordance with the capacitance.

  As described above, in the variable capacitance element 1 according to the embodiment of the present invention, as shown in FIG. 6, each fixed electrode 10 is opposed to the circle C inscribed in the square of the movable electrode 8 on the upper surface 2 </ b> A of the substrate 2. The fixed electrode 10 is not disposed in the region that is disposed in the region and that faces each vertex portion 8A of the movable electrode 8. As described above, by not arranging the fixed electrode 10 in the region facing each vertex portion 8A of the movable electrode 8, even if the movable electrode 8 is warped, the vertex portion 8A of the movable electrode 8 is fixed to the fixed electrode. 10, and the distance between the center region of the movable electrode 8 and each fixed electrode 10, that is, the narrow gap G 1 can be reduced. Therefore, the capacitance value between the movable electrode 8 and each fixed electrode 10 can be increased.

  As a result of intensive studies by the inventors, it has been found that when the movable electrode 8 is formed using a plating layer, the central region of the movable electrode 8 has a flat shape with almost no warpage. More specifically, for example, when the movable electrode 8 is formed in a square shape having a thickness dimension of 10 μm and a length of one side of 150 μm, each vertex portion 8A of the movable electrode 8 is warped by about 500 nm and a peripheral portion. Among them, a warp of about 200 nm occurs at the center position of each side. On the other hand, it was found that, for example, in the central region having a radius of about 80 to 100 μm, only a warp of about several tens of nm smaller than 100 nm occurs.

  For this reason, the central region of the movable electrode 8 has a relatively small degree of warpage or a degree of variation in warpage. Therefore, variation in the capacitance value between the movable electrode 8 and each fixed electrode 10 due to variations in the warp of the movable electrode 8 can be suppressed, and the accuracy of the variable capacitance element 1 can be increased.

  Here, the effect of the variable capacitance element 1 described above will be confirmed with reference to FIGS. 7 and 10 to 12. 7, 11, and 12, illustration of the support beam 9 and the like is omitted for convenience of explanation.

  FIG. 7 shows a state in which the movable electrode 8 formed of a plating layer made of a conductive metal material such as copper is warped, and each apex portion 8A is curved in a direction approaching the substrate 2. Even if the movable electrode 8 warps as shown in FIG. 7, the fixed electrode 10 is not disposed in the region facing each vertex 8 </ b> A of the movable electrode 8. While avoiding the contact, the narrow gap G1 between the movable electrode 8 and each fixed electrode 10 can be reduced, and the capacitance value between both electrodes can be increased.

  Further, in the case of the movable electrode 8 formed of a plating layer made of a conductive metal material such as copper, a large warp is generated in each vertex portion 8A, but almost no warp is generated in the central portion of the movable electrode 8. Tend. For this reason, the narrow gap G1 between the movable electrode 8 and the fixed electrode 10 can be made substantially constant at various portions of the fixed electrode 10, and the electrostatic capacitance between the movable electrode 8 and the fixed electrode 10 due to variations in warpage. It is possible to prevent the value from varying.

  On the other hand, FIG. 10 shows, as a first comparative example for confirming the effect of the embodiment of the present invention, a fixed electrode 41 formed in a square substantially the same as the square of the movable electrode 8 is provided in place of the fixed electrode 10. Shows the case. FIG. 11 shows a case where warpage occurs in each apex portion 8A of the movable electrode 8 formed of a plating layer made of a conductive metal material such as copper when the fixed electrode 41 is provided. As shown in FIG. 11, in the case of the fixed electrode 41 formed in a square substantially the same as the square of the movable electrode 8, if the contact between the movable electrode 8 and the fixed electrode 41 is to be avoided, The narrow gap G3 between the fixed electrode 41 must be made larger than the narrow gap G1 in FIG. As a result, in the fixed electrode 41 in the comparative example, it is difficult to increase the capacitance value between the movable electrode 8 and the fixed electrode 41.

  Further, in the case of the fixed electrode 41 in the comparative example, the fixed electrode 41 is disposed below each apex portion 8A of the movable electrode 8 where the warp has occurred. The capacitance value between the two tends to vary.

  FIG. 12 shows, as a second comparative example for confirming the effect of the embodiment of the present invention, a movable electrode 8 formed of a plating layer made of a conductive metal material such as copper, using a silicon material, for example. The case where it replaces with the movable electrode 51 formed in this is shown. In this case, the movable electrode 51 is formed using a film forming method other than plating such as CVD or vapor deposition. As shown in FIG. 12, in the case of the movable electrode 51 formed using a film forming method other than plating, not only each vertex portion 51A but also the central portion of the movable electrode 51 tends to warp. . When the warpage occurs as a whole as described above, the fixed electrode 10 is disposed so as to sink into a position below the central portion of the movable electrode 51, avoiding a region facing each apex portion 51 </ b> A of the movable electrode 51. In addition, the narrow gap G 4 between the movable electrode 51 and each fixed electrode 10 becomes large at the center position of the movable electrode 51 and becomes non-uniform over the entire fixed electrode 10. As a result, the capacitance value between the two electrodes decreases, the capacitance value changes according to the shape of the warp, and the capacitance value tends to vary from element to element.

  As described above, by comparing FIG. 7 showing the embodiment of the present invention with FIGS. 11 and 12 showing the first and second comparative examples, the variable capacitance element 1 according to the embodiment of the present invention is narrow. It can be seen that the gap G1 can be reduced to increase the capacitance value, and variations in the capacitance value can be suppressed.

  Further, in the variable capacitance element 1 according to the embodiment of the present invention, each extraction electrode 11 that connects each fixed electrode 10 and the through electrodes 15 and 16 intersects the central portion of one side of the square of the movable electrode 8 in plan view. It is arranged to do. Thereby, each extraction electrode 11 can be arranged avoiding the region facing each vertex portion 8A of the movable electrode 8 which tends to generate a large warp, and other than the region facing each vertex portion 8A of the movable electrode 8 In this region, each fixed electrode 10 and each extraction electrode 11 can be connected. As a result, since the extraction electrode 11 is disposed in the region of the movable electrode 8 where the warp is small, the distance between the movable electrode 8 and the fixed electrode 10 is reduced in a state where the movable electrode 8 and the extraction electrode 11 are not short-circuited. Thus, the capacitance value between the movable electrode 8 and each fixed electrode 10 can be increased.

  In the above-described embodiment, the planar shape of the movable electrode 8 is a square, but the present invention is not limited to this. The planar view shape of the movable electrode 8 may be another quadrangle such as a rectangle, or another polygon such as a pentagon and a hexagon.

  Further, in the above-described embodiment, as shown in FIG. 6, the fixed electrodes 10 are arranged side by side on almost the entire area in the circular region facing the circle C inscribed in the movable electrode 8 on the upper surface 2 </ b> A of the substrate 2. As an example, the present invention is not limited to this. As shown in FIG. 8, each fixed electrode 21 may be arranged only in the center portion of the circle C (for example, a portion of about 50 to 80% of the diameter dimension of the circle C). Thereby, on the upper surface 2 </ b> A of the substrate 2, not only the region facing each vertex 8 </ b> A of the movable electrode 8, but also the region facing each side of the movable electrode 8, i.e., the region facing the entire peripheral portion of the movable electrode 8. The fixed electrodes 21 can be arranged avoiding the above. Therefore, if warpage occurs not only in each vertex 8A of the movable electrode 8 but also in each side portion of the movable electrode 8, the movable electrode 8 is avoided while avoiding contact between the movable electrode 8 and each fixed electrode 21. And the distance between each fixed electrode 21 can be reduced.

  In the above-described embodiment, as shown in FIG. 6, the case where the two fixed electrodes 10 are arranged side by side has been described as an example, but the present invention is not limited to this. As shown in FIG. 9, one fixed electrode 31 may be provided. In this case, the fixed electrode 31 is preferably circular. However, when the movable electrode 8 is rectangular instead of square, it is desirable that the fixed electrode 31 has an elliptical shape. Three or more fixed electrodes may be provided.

  In the above-described embodiment, the drive electrode 12 is provided above the movable electrode 8 as an example, but the arrangement of the drive electrode is not limited to this. It is also possible to dispose the drive electrode at a position different from the fixed electrode 10 on the upper surface 2 </ b> A of the substrate 2 below the movable electrode 8.

DESCRIPTION OF SYMBOLS 1 Variable capacitance element 2 Board | substrate 2A Upper surface 3 Functional layer (plating layer)
7 Supporting part 8 Movable electrode 9 Supporting beam 10, 21, 31 Fixed electrode 11 Extraction electrode

Claims (4)

A substrate, a support provided on the substrate, a movable electrode supported by the support via a support beam so as to be displaceable in a thickness direction, and a space provided between the movable electrode and the space provided on the upper surface of the substrate; In a variable capacitance element provided with fixed electrodes arranged so as to face each other,
The movable electrode has a polygonal shape in plan view,
The fixed electrode is provided in a region facing the movable electrode on a top surface of the substrate and facing a circle or an ellipse inscribed in a polygon of the movable electrode. Variable capacitance element.   The variable capacitance element according to claim 1, wherein the movable electrode is formed using a plated layer formed by plating.   The variable capacitance element according to claim 1, wherein the fixed electrode has a circular or elliptical shape in plan view. Provided on the upper surface of the substrate, comprising an extraction electrode for electrically connecting the fixed electrode and an external circuit,
4. The variable capacitance element according to claim 1, wherein the extraction electrode is disposed so as to intersect with a central portion of one side of the polygon of the movable electrode in a plan view.

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