WO2010137447A1 - Variable capacity element - Google Patents

Variable capacity element Download PDF

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Publication number
WO2010137447A1
WO2010137447A1 PCT/JP2010/057802 JP2010057802W WO2010137447A1 WO 2010137447 A1 WO2010137447 A1 WO 2010137447A1 JP 2010057802 W JP2010057802 W JP 2010057802W WO 2010137447 A1 WO2010137447 A1 WO 2010137447A1
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Prior art keywords
movable
fixed
electrode
support beam
substrate
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PCT/JP2010/057802
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French (fr)
Japanese (ja)
Inventor
光治 竹村
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株式会社村田製作所
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Publication of WO2010137447A1 publication Critical patent/WO2010137447A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G5/00—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture
    • H01G5/01—Details
    • H01G5/011—Electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G5/00—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture
    • H01G5/16—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture using variation of distance between electrodes
    • H01G5/18—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture using variation of distance between electrodes due to change in inclination, e.g. by flexing, by spiral wrapping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/10—Auxiliary devices for switching or interrupting
    • H01P1/12—Auxiliary devices for switching or interrupting by mechanical chopper
    • H01P1/127—Strip line switches
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H59/00—Electrostatic relays; Electro-adhesion relays
    • H01H59/0009—Electrostatic relays; Electro-adhesion relays making use of micromechanics
    • H01H2059/0072—Electrostatic relays; Electro-adhesion relays making use of micromechanics with stoppers or protrusions for maintaining a gap, reducing the contact area or for preventing stiction between the movable and the fixed electrode in the attracted position
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H59/00—Electrostatic relays; Electro-adhesion relays
    • H01H59/0009—Electrostatic relays; Electro-adhesion relays making use of micromechanics

Definitions

  • the present invention relates to a variable capacitance element which is a kind of MEMS (Micro Electro Mechanical Systems) device.
  • MEMS Micro Electro Mechanical Systems
  • variable capacitance element which is a kind of MEMS device can be used as, for example, a varicap, a relay element, a switch element, or the like.
  • a variable capacitance element is generally configured as follows.
  • a support portion and a movable portion supported by the support portion so as to be displaceable in the thickness direction via a support beam are formed by etching.
  • Such a silicon substrate is sandwiched between the first and second glass substrates, and the support portion is fixed between these glass substrates.
  • one or both of the two glass substrates are provided with a recessed portion at a position facing the movable portion, and a space for accommodating the movable portion between the two glass substrates by the recessed portion. Is formed. Thereby, the movable part can be displaced in the thickness direction within the space formed between the two glass substrates.
  • driving electrodes facing each other through spaces are respectively provided on the surface of the movable part facing each other and the back surface of the second glass substrate.
  • An electrostatic force is generated by applying a driving voltage between these driving electrodes, and the movable part can be displaced by this electrostatic force.
  • signal electrodes facing each other through a space are respectively provided on the back surface of the movable part facing each other and the surface of the first glass substrate, and a signal path through which a high-frequency signal flows is provided between these signal electrodes.
  • the distance between the signal electrodes arranged to face each other changes, and the capacitance between these signal electrodes changes.
  • variable capacitance element for example, an insulating film that insulates between the signal electrode and the drive electrode of the movable part is formed.
  • the insulating film has a small thickness (for example, about several ⁇ m), the impedance on the high frequency side is small. For this reason, when a high frequency signal of, for example, several tens of MHz to several GHz is supplied to the signal electrode, the high frequency signal may leak to the drive electrode through the insulating film and flow into the drive voltage supply path.
  • the movable part includes a silicon region located in the center, a silicon region located in the periphery thereof, and an oxidation region interposed between these silicon regions, A metallized region corresponding to the signal electrode is provided in the silicon region located in the part, and the silicon region located in the peripheral part functions as a drive electrode. According to such a configuration, leakage of the high frequency signal flowing through the signal electrode provided in the movable part can be suppressed by the oxidation region.
  • a P ++ epi layer and a P type epi layer formed by epitaxial growth are sequentially stacked on a P type silicon substrate to form a three layer substrate, and the three layer substrate is etched.
  • the support beam and the movable part are formed by processing.
  • the movable part does not have a symmetric structure with respect to the thickness direction, it is not easy to control the warp of the movable part.
  • the movable part is formed using the three-layer substrate, the formation process of the movable part is complicated and the manufacturing cost increases, and in addition to the warp of the movable part, the signal electrode on the movable side and the signal electrode on the fixed side The capacitance cannot be set with high accuracy. Furthermore, since the thickness of the support beam is determined by the thickness of the P-type epi layer, the spring design of the support beam is limited. In addition, since the movable part is formed by wet etching using potassium hydroxide (KOH) using the P ++ epi layer as an etching stop layer, there is a problem that the processing accuracy of the movable part is poor.
  • KOH potassium hydroxide
  • the present invention has been made in view of, for example, the above-described problems, and an object of the present invention is supplied between signal electrodes arranged opposite to each other, that is, between a fixed signal electrode and a movable signal electrode.
  • An object of the present invention is to provide a variable capacitance element that can suppress the leakage of a high-frequency signal to the support portion and can set the capacitance between signal electrodes with high accuracy.
  • the present invention provides a single-layer silicon substrate provided between a first substrate and a second substrate, the silicon substrate, the first substrate, A support portion fixed to a second substrate; a movable portion formed on the silicon substrate and supported by the support portion so as to be displaceable in a thickness direction using a support beam; and provided on the first substrate.
  • a fixed-side drive electrode disposed at a position facing the movable portion; and an electrostatic force provided between the fixed-side drive electrode and disposed at the position opposed to the fixed-side drive electrode.
  • the capacitive element is an insulating state by oxidizing all of the support beams, and the support beam is used to leak a high-frequency signal supplied to the fixed-side signal electrode toward the support portion. It is set as the structure which prevents.
  • the entire support beam is insulative by oxidizing the entire support beam. For this reason, even if the high-frequency signal supplied to the fixed-side signal electrode propagates into the movable part through the movable-side signal electrode, the leakage of the high-frequency signal from the movable part to the support part side is prevented or suppressed by the support beam. Can do.
  • the movable portion and the support beam are formed using a single layer silicon substrate, when forming the movable portion or the like, the silicon substrate is processed by dry etching such as ICP (InductivelyductCoupled Plasma) etching, for example. be able to. For this reason, a movable part and a support beam can be processed with high precision compared with the case where wet etching is used.
  • dry etching such as ICP (InductivelyductCoupled Plasma) etching
  • the movable side drive electrode is disposed on the front surface of the movable portion facing the first substrate, and the movable side signal electrode is disposed on the rear surface facing the second substrate, in the thickness direction of the movable portion.
  • electrodes made of a conductive metal material can be arranged at symmetrical positions. Thereby, thermal stress etc. can be made comparable on both surfaces of a movable part, and the curvature of a movable part can be suppressed.
  • the support beam may be formed by forming the shape of the support beam by dry etching and then oxidizing it by performing an oxidation treatment.
  • the shape of the support beam is formed by dry etching such as ICP etching, for example, a thin support beam having a width dimension of about several ⁇ m can be formed easily and with high accuracy. For this reason, the spring constant of the support beam can be set with high accuracy, and the design flexibility of the support beam can be increased. Further, the support beam can be easily oxidized by, for example, heat treatment after being formed by dry etching. For this reason, even if it is a fine support beam with a complicated and weak mechanical rigidity, all of it can be oxidized reliably, and all of a support beam can be made into an insulation state.
  • the entire support beam can be reliably oxidized even when the depth of the oxide layer is saturated at about 2 ⁇ m. Therefore, the high-frequency signal supplied to the signal path formed between the fixed-side signal electrode and the movable-side signal electrode is reliably prevented or suppressed from leaking from the movable part to the support part side via the support beam. Can do.
  • FIG. 3 is a longitudinal sectional view showing the variable capacitance element as seen from the direction of arrows III-III in FIG.
  • FIG. 4 is a cross-sectional view showing the variable capacitance element as viewed from the direction of arrows IV-IV in FIG.
  • FIG. 5 is a transverse sectional view showing the variable capacitance element as seen from the direction of arrows VV in FIG. 1.
  • FIG. 5 is a cross-sectional view showing the variable capacitance element as viewed from the direction of arrows VI-VI in FIG. It is a longitudinal cross-sectional view which expands and shows the support beam of a variable capacitance element. It is a cross-sectional view which expands and shows the support beam of a variable capacitance element.
  • variable capacitor 1 according to an embodiment of the present invention is formed by sandwiching a silicon substrate 4 between an upper glass substrate 2 and a lower glass substrate 3.
  • the upper glass substrate 2 constitutes a first substrate and is formed of, for example, an insulating glass material, and is formed in a quadrangular shape having a horizontal dimension in FIG. Further, a recess 2A is formed on the lower surface side (back surface side) of the upper glass substrate 2 by etching, for example. Further, the peripheral edge portion of the lower surface of the upper glass substrate 2 is bonded to the silicon substrate 4 via a fixed-side conductive film 25 and a movable-side conductive film 12 described later.
  • a sealed space is formed between the recessed portion 2A of the upper glass substrate 2 and the recessed portion 3A of the lower glass substrate 3, and a movable portion 7, a support beam 9, and an extraction electrode arrangement, which will be described later, are formed in the sealed space.
  • the installation part 10 (refer FIG. 3) etc. are accommodated. Note that the upper glass substrate 2 and the lower glass substrate 3 may be replaced with substrates formed of other insulating materials.
  • the support portion 5 is formed on the silicon substrate 4 and is fixed to the upper glass substrate 2 and the lower glass substrate 3. As shown in FIG. 4, the support part 5 is formed in a rectangular frame shape and surrounds the movable part 7. Further, as shown in FIG. 1, the support portion 5 has a thickness dimension of about 50 ⁇ m to 300 ⁇ m, for example.
  • an insulating film 6 is formed on the upper surface side, the lower surface side, the side surface facing outward, and the side surface facing inward of the support portion 5. That is, the support portion 5 is covered with an insulating film 6 made of a silicon oxide film except for a portion to which a support beam 9 described later is connected.
  • the thickness dimension of the insulating film 6 is about 2 ⁇ m.
  • the movable part 7 is formed on the silicon substrate 4 and supported by the support part 5 using a support beam 9 described later. As shown in FIG. 4, the movable part 7 is formed in a rectangular flat plate shape. Further, as shown in FIG. 1, the thickness dimension of the movable part 7 is substantially equal to the thickness dimension of the support part 5, or about several ⁇ m to several tens ⁇ m smaller than the thickness dimension of the support part 5. In addition, the movable portion 7 has a thickness direction (vertical direction in FIG. 1) in a sealed space formed inside the variable capacitor 1 by the recessed portion 2A of the upper glass substrate 2 and the recessed portion 3A of the lower glass substrate 3. Can be displaced.
  • each support beam 9 is provided between the support portion 5 and the movable portion 7 as shown in FIG. 4, and support the movable portion 7 so as to be displaceable in the thickness direction as shown in FIG.
  • Each support beam 9 has a base end connected to the support portion 5 and a distal end extending substantially parallel to the upper glass substrates 2 and 3 and connected to the corners of the movable portion 7.
  • each support beam 9 is separated from the upper glass substrate 2 and the lower glass substrate 3, respectively, and displaces the movable part 7 in the thickness direction by being twisted or bent in the thickness direction. be able to. For this reason, as shown in FIG. 4, each support beam 9 has a shape bent in a crank shape or a meander shape, for example, as a shape that can be easily bent and deformed in the thickness direction. As shown in FIG. 7, the thickness dimension d1 of each support beam 9 is set to a value smaller than the thickness dimension of the support portion 5, for example, 50 ⁇ m or less. The thickness dimension d1 of the support beam 9 may be the same value as the thickness dimension of the support portion 5.
  • each support beam 9 has a width dimension d2 of 4 ⁇ m or less, more specifically about 2 ⁇ m to 3 ⁇ m.
  • Each support beam 9 is entirely formed of silicon oxide, and each part of each support beam 9 has an insulating property.
  • each support beam 9 is obtained by subjecting the silicon substrate 4 to ICP etching, forming a crank shape or meander shape having a thickness dimension d1 and a width dimension d2, and then performing a thermal oxidation treatment. Is formed.
  • the thermal oxidation process is continued until the thickness dimension of the insulating film reaches about 2 ⁇ m.
  • the thickness dimension of the insulating film to be formed increases corresponding to the time to perform.
  • the thickness dimension of the insulating film to be formed hardly increases compared to the time for which the thermal oxidation process is continued.
  • the extraction electrode arrangement portion 10 is provided in a sealed space formed inside the variable capacitor 1 by the recessed portion 2 ⁇ / b> A of the upper glass substrate 2 and the recessed portion 3 ⁇ / b> A of the lower glass substrate 3. 5 is connected.
  • the extraction electrode disposing unit 10 is a part for disposing a driving extraction electrode 16 that is a supply path of a driving voltage to be applied between a movable driving electrode 13 and a fixed driving electrode 14 described later.
  • the extraction electrode arrangement portion 10 is covered with an insulating film 11 made of a silicon oxide film having a thickness dimension of about 2 ⁇ m, in the same manner as the support portion 5 and the movable portion 7.
  • the first movable conductive film 12 is a conductive thin film formed of a metal material such as gold or an alloy containing gold. It is formed using.
  • the first movable conductive film 12 is formed on the upper surface side of the support portion 5, the movable portion 7, the support beam 9, and the extraction electrode arrangement portion 10.
  • the movable conductive film 12 provided on the upper surface side of the movable portion 7 serves as the movable drive electrode 13.
  • the movable-side conductive film 12 is continuously formed without being physically cut halfway from the support portion 5 through the support beams 9 to the movable portion 7.
  • the movable drive electrode 13 is electrically connected to the movable conductive film 12 provided on the upper surface side of the support portion 5 via the movable conductive film 12 provided on the upper surface side of each support beam 9. ing.
  • the movable conductive film 12 provided on the upper surface side of the support portion 5 is electrically connected to a drive lead electrode 15 described later (see FIG. 3).
  • the movable-side conductive film 12 provided on the upper surface side of the extraction electrode arrangement portion 10 is physically cut off from the movable-side conductive film 12 (including the movable-side drive electrode 13) provided in other parts, And separated.
  • the fixed-side drive electrode 14 is a conductive thin film formed of a metal material such as gold or an alloy containing gold, and the lower surface ( The bottom surface of the recessed portion 2A is provided by using, for example, sputtering, vapor deposition or the like, and is disposed at a position facing the movable drive electrode 13.
  • a space S1 is formed between the fixed drive electrode 14 and the movable drive electrode 13 as shown in FIG.
  • the fixed side drive electrode 14 is connected to the movable side conductive film 12 provided on the upper surface side of the extraction electrode disposition portion 10, so that both are electrically connected. Yes.
  • the movable conductive film 12 provided on the upper surface side of the extraction electrode placement portion 10 is electrically connected to a drive extraction electrode 16 described later (see FIG. 3).
  • the first drive lead electrode 15 is made of copper or the like in a via hole (through hole) drilled through both the lower glass substrate 3 and the support portion 5 in the thickness direction. It is formed by filling the conductive metal material.
  • the upper end side of the drive lead electrode 15 is electrically connected to the movable drive electrode 13 via the movable conductive film 12 provided continuously on the upper surface side of the support portion 5 and the upper surface of each support beam 9,
  • the lower end side is a connection terminal that can be connected to an external drive voltage supply circuit 31.
  • the second drive lead electrode 16 is made of a conductive metal such as copper in a via hole (through hole) drilled through both the lower glass substrate 3 and the lead electrode placement portion 10 in the thickness direction. It is formed by filling the material.
  • the upper end side of the drive extraction electrode 16 is electrically connected to the fixed drive electrode 14 via the movable conductive film 12 provided on the upper surface side of the extraction electrode arrangement portion 10, and the lower end side is externally driven. This is a connection terminal that can be connected to the voltage supply circuit 31.
  • the upper stopper 17 is a plurality of insulating protrusions formed by etching on the lower surface of the upper glass substrate 2 (the bottom surface of the recessed portion 2A), as shown in FIGS.
  • the upper stopper 17 protrudes toward the movable portion 7 (lower side) with respect to the fixed drive electrode 14. Thereby, the upper stopper 17 prevents the movable drive electrode 13 and the fixed drive electrode 14 from being short-circuited.
  • the lower stopper 18 is a plurality of insulating projections formed by etching on the upper surface of the lower glass substrate 3 (the bottom surface of the recessed portion 3A). And the lower side stopper 18 protrudes toward the movable part 7 side (upper side) rather than the fixed side signal electrode 21 mentioned later. As a result, the lower stopper 18 prevents the movable signal electrode 20 and the fixed signal electrodes 21 and 22 from being short-circuited, and the static stopper between the movable signal electrode 20 and the fixed signal electrodes 21 and 22.
  • the maximum capacity is set.
  • the second movable-side conductive film 19 is a thin film formed of a conductive metal material such as gold similar to the first movable-side conductive film 12, and is formed by sputtering, for example. , Using a vapor deposition method or the like. Further, the second movable-side conductive film 19 is formed on the lower surface side of the support portion 5, the movable portion 7, the support beam 9, and the extraction electrode arrangement portion 10. Of the movable conductive film 19, the movable conductive film 19 provided on the lower surface side of the movable portion 7 serves as the movable signal electrode 20.
  • the movable conductive film 19 is physically cut at the boundary portion between the support portion 5 and each support beam 9 and at the boundary portion between each support beam 9 and the movable portion 7.
  • the movable-side signal electrode 20 is electrically cut off from the movable-side conductive film 19 provided on the lower surface side of each support beam 9 and the movable-side conductive film 19 provided on the lower surface side of the support portion 5.
  • the movable conductive film 19 provided on the lower surface side of the extraction electrode placement portion 10 is also physically cut from the movable conductive film 19 (including the movable signal electrode 20) provided in other parts, And it is electrically cut off.
  • the movable side conductive film 19 (movable side signal electrode 20) and the movable side conductive film 12 (movable side drive electrode 13) are electrically cut off by the insulating films 6, 8, and 11.
  • the movable side drive electrode 13 and the movable side signal electrode 20 have substantially the same thickness. Thereby, the structure of the movable part 7 is symmetrical in the thickness direction.
  • each of the first fixed-side signal electrode 21 and the second fixed-side signal electrode 22 is a conductive thin film formed of a metal material such as gold or an alloy containing gold, for example.
  • the lower glass substrate 3 is provided on the upper surface (the bottom surface of the recessed portion 3 ⁇ / b> A) using, for example, sputtering, vapor deposition, or the like, and is disposed at a position facing the movable signal electrode 20.
  • a space S2 is formed between the fixed signal electrodes 21 and 22 and the movable signal electrode 20.
  • each of the first signal extraction electrode 23 and the second signal extraction electrode 24 is in a via hole (through hole) formed through the lower glass substrate 3 in the thickness direction. It is formed by filling a conductive metal material such as copper.
  • the upper end side of the signal extraction electrode 23 is electrically connected to the fixed-side signal electrode 21, and the lower end side is a connection terminal that can be connected to an external high-frequency circuit or the like.
  • the upper end side of the signal extraction electrode 24 is electrically connected to the fixed-side signal electrode 22, and the lower end side is a connection terminal that can be connected to an external high-frequency circuit or the like.
  • the second fixed-side conductive film 26 is provided on the periphery of the upper surface of the lower glass substrate 3 by using, for example, sputtering, vapor deposition or the like.
  • the lower glass substrate 3 is bonded to the support portion 5 by thermocompression bonding of the fixed-side conductive film 26 and the movable-side conductive film 19 provided on the lower surface side of the support portion 5.
  • variable capacitance element 1 according to the embodiment of the present invention has the above-described configuration, and this manufacturing method will be described next.
  • etching is performed from the lower surface side of the silicon substrate 4, and a portion corresponding to the support beam 9 in the silicon substrate 4 is thinly processed.
  • ICP etching is performed from the upper surface side of the silicon substrate 4 to shape the shapes of the support portion 5, the movable portion 7, each support beam 9, and the extraction electrode arrangement portion 10 (silicon substrate forming step).
  • a via hole for providing the driving lead electrode 15 is formed in the support portion 5 and a via hole for providing the driving lead electrode 16 is formed in the lead electrode arrangement portion 10.
  • the movable-side conductive film 12 is provided on the upper surface side of each of the support portion 5, the movable portion 7, and the extraction electrode placement portion 10 and on the upper surface of each support beam 9 by vapor deposition.
  • the portion corresponding to the extraction electrode placement portion 10 in the movable conductive film 12 is separated from other portions.
  • a movable drive electrode 13 is formed on the upper surface side of the movable portion 7.
  • the movable-side conductive film 19 is provided on each lower surface side of the support portion 5, the movable portion 7, the extraction electrode arrangement portion 10, and the like by using a vapor deposition method.
  • the movable side signal electrode 20 is formed on the lower surface side of the movable portion 7 (movable side electrode forming step).
  • the recessed portion 2A and the upper stopper 17 are formed by etching the upper glass substrate 2, and the fixed movable electrode 14 and the fixed conductive film 25 are formed on the upper glass substrate 2 by sputtering, vapor deposition or the like. Provided (first glass substrate forming step).
  • the recessed portion 3A and the lower stopper 18 are formed by etching the lower glass substrate 3, and the drive extraction electrodes 15 and 16 and the signal extraction electrode 23 are formed using laser processing, microblasting, or the like.
  • 24 are formed in the lower glass substrate 3, and the fixed signal electrodes 21 and 22 and the fixed conductive film 26 are formed in the lower glass substrate 3 by sputtering, vapor deposition or the like ( Second glass substrate forming step).
  • the upper surface side of the silicon substrate 4 that has undergone the silicon substrate forming step, the oxidation step, and the movable electrode forming step and the lower surface side of the upper glass substrate 2 that has undergone the first glass substrate forming step are pressure bonded. Substrate bonding step).
  • the lower surface side of the silicon substrate 4 and the upper surface side of the lower glass substrate 3 that has undergone the second glass substrate forming step are bonded by pressure bonding (second substrate bonding step).
  • a drive extraction electrode 15 is provided in the via hole formed so as to penetrate the support portion 5 and the lower glass substrate 3, and is formed so as to penetrate the extraction electrode arrangement portion 10 and the lower glass substrate 3.
  • the drive lead electrode 16 is provided in the formed via hole, and the signal lead electrodes 23 and 24 are provided in the via holes respectively formed below the fixed side signal electrodes 21 and 22 in the lower glass substrate 3 (lead electrode forming step). ).
  • variable capacitance element 1 Next, the basic operation of the variable capacitance element 1 will be described. That is, one output terminal of the drive voltage supply circuit 31 is connected to the movable drive electrode 13 via the drive lead electrode 15, and the other output terminal is connected to the fixed drive electrode 14 via the drive lead electrode 16. It is connected to the. As a result, the drive voltage output from the drive voltage supply circuit 31 is applied between the movable drive electrode 13 and the fixed drive electrode 14.
  • one terminal of the high-frequency circuit is connected to the fixed-side signal electrode 21 through the signal extraction electrode 23, and the other terminal is connected to the fixed-side signal electrode 22 through the signal extraction electrode 24.
  • variable capacitance element 1 of the present embodiment functions as a switch element that switches between transmission and stop of a high-frequency signal according to the position of the movable portion 7.
  • the entire support beam 9 is insulated by oxidizing all of the support beams 9. For this reason, even if the high-frequency signal supplied to the fixed-side signal electrodes 21 and 22 propagates through the movable-side signal electrode 20 to the inside of the movable portion 7, it supports leakage of the high-frequency signal from the movable portion 7 to the support portion 5 side. It can be blocked or suppressed by the beam 9.
  • the thickness dimension of the insulating film 8 is made substantially equal to each other on the upper surface side and the lower surface side of the movable portion 7, and the thickness dimension of the movable drive electrode 13 and the thickness dimension of the movable signal electrode 20 are mutually equal. Make almost equal. Thereby, the movable part 7 can be made into a symmetrical structure in the thickness direction.
  • the thermal stress and the like can be made comparable between the upper surface and the lower surface of the movable portion 7, the warp of the movable portion 7 can be suppressed to the minimum, and the movable-side signal electrode 20 and the fixed-side signal can be suppressed. Capacitance can be set between the electrodes 21 and 22 with high accuracy. Furthermore, since the movable portion 7 and the like are formed using the single-layer silicon substrate 4, for example, the manufacturing process of the movable portion 7 can be simplified and the manufacturing cost can be reduced as compared with the case where a three-layer substrate is used. .
  • the spring constant of the support beam 9 can be set with high accuracy, and the design flexibility of the support beam 9 can be increased.
  • the support beam 9 can be easily oxidized by, for example, heat treatment after being formed by dry etching. For this reason, even if the support beam 9 is complicated and has a weak mechanical rigidity, all of the support beam 9 can be surely oxidized. Isolation between the two can be increased.
  • each support beam 9 is set to be larger than 4 ⁇ m and the width dimension of each support beam 9 is set to 4 ⁇ m or less.
  • the thickness dimension of each support beam 9 may be set to 4 ⁇ m or less, and the width dimension of each support beam 9 may be set to be larger than 4 ⁇ m.
  • the shape of the support beam 9 may be a shape other than the crank shape and the meander shape, and the number of the support beams 9 may be 1 to 3, or 5 or more. Further, the support beam 9 may be formed by dry etching other than ICP etching.
  • the present invention is not limited to this, and a single fixed-side signal electrode is provided on the upper surface of the lower glass substrate, and ground electrodes are provided on both sides in the width direction of the fixed-side signal electrode. A coplanar line may be formed by the ground electrode.
  • variable capacitance element 1 variable capacitance element 2 upper glass substrate (first substrate) 3 Lower glass substrate (second substrate) 4 Silicon Substrate 5 Supporting Section 7 Movable Part 9 Supporting Beam 13 Movable Drive Electrode 14 Fixed Drive Electrode 20 Movable Signal Electrode 21 First Fixed Signal Signal 22 Second Fixed Signal Signal

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Abstract

Support beams (9) that are set to a width dimension of no more than 4 µm are shaped by ICP etching and then subjected to heat oxidation treatment to oxidise the entire support beams (9). In this way, it is possible to prevent or suppress leakage of the high-frequency signal supplied to the fixed-side signal electrodes (21, 22) provided on the underlying glass substrate (3) into the support section (5) through a movable section (7) and the support beams (9). Also, the movable section (7) may be endowed with a symmetrical structure in the thickness direction thereof, by forming the same using a single-layer silicon substrate (4). In this way, warping of the movable section (7) is suppressed and the electrostatic capacity between the signal electrode (20) on the movable side and the signal electrodes (21, 22) on the fixed side can be set with high precision.

Description

可変容量素子Variable capacitance element
　本発明は、ＭＥＭＳ（Micro Electro Mechanical Systems）デバイスの一種である可変容量素子に関する。 The present invention relates to a variable capacitance element which is a kind of MEMS (Micro Electro Mechanical Systems) device.
　ＭＥＭＳデバイスの一種である可変容量素子は、例えばバリキャップ、リレー素子、スイッチ素子等として用いることができる。このような可変容量素子は概ね次のように構成されている。 A variable capacitance element which is a kind of MEMS device can be used as, for example, a varicap, a relay element, a switch element, or the like. Such a variable capacitance element is generally configured as follows.
　即ち、シリコン基板には、支持部と、該支持部に支持梁を介して厚さ方向に変位可能に支持された可動部とがエッチング加工により形成されている。このようなシリコン基板は第１，第２のガラス基板の間に挟み込まれ、支持部はこれらのガラス基板の間に固定されている。また、２枚のガラス基板のうちのいずれか一方または双方には、可動部と対向する位置に凹陥部が形成され、この凹陥部によって２枚のガラス基板の間には可動部を収容する空間が形成されている。これにより、可動部は、２枚のガラス基板の間に形成された空間内を厚さ方向に変位することができる。 That is, on the silicon substrate, a support portion and a movable portion supported by the support portion so as to be displaceable in the thickness direction via a support beam are formed by etching. Such a silicon substrate is sandwiched between the first and second glass substrates, and the support portion is fixed between these glass substrates. In addition, one or both of the two glass substrates are provided with a recessed portion at a position facing the movable portion, and a space for accommodating the movable portion between the two glass substrates by the recessed portion. Is formed. Thereby, the movable part can be displaced in the thickness direction within the space formed between the two glass substrates.
　また、互いに対向する可動部の表面および第２のガラス基板の裏面には、空間を介して互いに対向する駆動電極がそれぞれ設けられている。これら駆動電極間に駆動電圧を印加することにより静電力を発生させ、この静電力により可動部を変位させることができる。さらに、互いに対向する可動部の裏面と第１のガラス基板の表面には、空間を介して対向する信号電極がそれぞれ設けられ、これら信号電極間は高周波信号が流れる信号経路となる。 Further, driving electrodes facing each other through spaces are respectively provided on the surface of the movable part facing each other and the back surface of the second glass substrate. An electrostatic force is generated by applying a driving voltage between these driving electrodes, and the movable part can be displaced by this electrostatic force. Furthermore, signal electrodes facing each other through a space are respectively provided on the back surface of the movable part facing each other and the surface of the first glass substrate, and a signal path through which a high-frequency signal flows is provided between these signal electrodes.
　そして、駆動電圧の印加により可動部が変位すると、互いに対向して配置された信号電極間の距離が変化し、これら信号電極間の静電容量が変化する構成となっている。 Further, when the movable part is displaced by the application of the drive voltage, the distance between the signal electrodes arranged to face each other changes, and the capacitance between these signal electrodes changes.
　また、可動部は、中心部に位置するシリコン領域と、該シリコン領域を取囲む枠状のシリコン領域とに分離し、これらの間を酸化領域で連結した構成も知られている（特許文献１参照）。この場合、中央のシリコン領域に信号電極を形成し、周囲のシリコン領域を駆動電極として使用している。 In addition, a configuration is also known in which the movable part is divided into a silicon region located in the center and a frame-like silicon region surrounding the silicon region, and these are connected by an oxidation region (Patent Document 1). reference). In this case, the signal electrode is formed in the central silicon region, and the surrounding silicon region is used as the drive electrode.
米国特許出願公開第２００４／００５６３２０号明細書US Patent Application Publication No. 2004/0056320
　ところで、従来技術による可変容量素子では、例えば可動部の信号電極と駆動電極との間に、これらの間を絶縁する絶縁膜を形成している。しかし、絶縁膜は、その厚さ寸法が薄い（例えば数μｍ程度）から、高周波側のインピーダンスが小さい。このため、信号電極に例えば数十ＭＨｚ～数ＧＨｚの高周波信号を供給したときには、この高周波信号が絶縁膜を介して駆動電極に漏洩し、駆動電圧供給経路に流れ込んでしまう虞れがある。 By the way, in the variable capacitance element according to the prior art, for example, an insulating film that insulates between the signal electrode and the drive electrode of the movable part is formed. However, since the insulating film has a small thickness (for example, about several μm), the impedance on the high frequency side is small. For this reason, when a high frequency signal of, for example, several tens of MHz to several GHz is supplied to the signal electrode, the high frequency signal may leak to the drive electrode through the insulating film and flow into the drive voltage supply path.
　一方、特許文献１に記載のリレー素子は、可動部を、中心部に位置するシリコン領域と、その周辺部に位置するシリコン領域と、これらシリコン領域間に介在する酸化領域とから構成し、中央部に位置するシリコン領域に、信号電極に相当する金属化領域を設けると共に、周辺部に位置するシリコン領域を駆動電極として機能させている。このような構成によれば、可動部に設けられた信号電極を流れる高周波信号の漏洩を酸化領域により抑制することができる。 On the other hand, in the relay element described in Patent Document 1, the movable part includes a silicon region located in the center, a silicon region located in the periphery thereof, and an oxidation region interposed between these silicon regions, A metallized region corresponding to the signal electrode is provided in the silicon region located in the part, and the silicon region located in the peripheral part functions as a drive electrode. According to such a configuration, leakage of the high frequency signal flowing through the signal electrode provided in the movable part can be suppressed by the oxidation region.
　しかしながら、特許文献１に記載のリレー素子では、Ｐ型シリコン基板上にエピタキシャル成長によって形成されたＰ＋＋エピ層およびＰ型エピ層を順次積層して３層基板を形成すると共に、該３層基板をエッチング加工することにより支持梁および可動部を形成している。この結果、可動部がその厚さ方向に対して対称な構造とならないため、可動部の反りの制御が容易でない。また、３層基板を用いて可動部等を形成するから、可動部の形成工程が複雑で製造コストが嵩むのに加え、可動部の反りによって可動側の信号電極と固定側の信号電極との間で静電容量を高精度に設定することができない。さらに、支持梁の厚さがＰ型エピ層の厚さで決まるため、支持梁のばね設計が制約される。これに加え、Ｐ＋＋エピ層をエッチングストップ層とした水酸化カリウム（ＫＯＨ）を用いたウェットエッチングにより可動部を形成しているため、可動部の加工精度が悪いという問題がある。 However, in the relay element described in Patent Document 1, a P ++ epi layer and a P type epi layer formed by epitaxial growth are sequentially stacked on a P type silicon substrate to form a three layer substrate, and the three layer substrate is etched. The support beam and the movable part are formed by processing. As a result, since the movable part does not have a symmetric structure with respect to the thickness direction, it is not easy to control the warp of the movable part. In addition, since the movable part is formed using the three-layer substrate, the formation process of the movable part is complicated and the manufacturing cost increases, and in addition to the warp of the movable part, the signal electrode on the movable side and the signal electrode on the fixed side The capacitance cannot be set with high accuracy. Furthermore, since the thickness of the support beam is determined by the thickness of the P-type epi layer, the spring design of the support beam is limited. In addition, since the movable part is formed by wet etching using potassium hydroxide (KOH) using the P ++ epi layer as an etching stop layer, there is a problem that the processing accuracy of the movable part is poor.
　本発明は例えば上述したような問題に鑑みなされたものであり、本発明の目的は、互いに対向して配置された信号電極間、即ち、固定側信号電極および可動側信号電極間に供給される高周波信号が支持部側へ漏洩することを抑制することができると共に、信号電極間の静電容量を高精度に設定することができる可変容量素子を提供することにある。 The present invention has been made in view of, for example, the above-described problems, and an object of the present invention is supplied between signal electrodes arranged opposite to each other, that is, between a fixed signal electrode and a movable signal electrode. An object of the present invention is to provide a variable capacitance element that can suppress the leakage of a high-frequency signal to the support portion and can set the capacitance between signal electrodes with high accuracy.
　（１）．上述した課題を解決するために、本発明は、第１の基板と第２の基板との間に設けられた単層のシリコン基板と、前記シリコン基板に形成され、前記第１の基板および前記第２の基板に固定された支持部と、前記シリコン基板に形成され、支持梁を用いて前記支持部に厚さ方向に変位可能に支持された可動部と、前記第１の基板に設けられ、前記可動部と対向する位置に配置された固定側駆動電極と、前記可動部に設けられ、前記固定側駆動電極と対向する位置に配置され、前記固定側駆動電極との間の静電力を作用させるための可動側駆動電極と、前記第２の基板に設けられ、前記可動部と対向する位置に配置された固定側信号電極と、前記可動部に設けられ、前記固定側信号電極と対向する位置に配置された可動側信号電極とを備えた可変容量素子であって、前記支持梁は、その全てを酸化させることによって絶縁状態とし、当該支持梁を用いて、前記固定側信号電極に供給された高周波信号が前記支持部に向けて漏洩するのを防止する構成としている。 (1). In order to solve the above-described problem, the present invention provides a single-layer silicon substrate provided between a first substrate and a second substrate, the silicon substrate, the first substrate, A support portion fixed to a second substrate; a movable portion formed on the silicon substrate and supported by the support portion so as to be displaceable in a thickness direction using a support beam; and provided on the first substrate. A fixed-side drive electrode disposed at a position facing the movable portion; and an electrostatic force provided between the fixed-side drive electrode and disposed at the position opposed to the fixed-side drive electrode. A movable drive electrode for acting, a fixed signal electrode provided on the second substrate and disposed at a position facing the movable part, and provided on the movable part and facing the fixed signal electrode With movable signal electrode arranged at the position The capacitive element is an insulating state by oxidizing all of the support beams, and the support beam is used to leak a high-frequency signal supplied to the fixed-side signal electrode toward the support portion. It is set as the structure which prevents.
　本発明によれば、支持梁の全部を酸化させることによって、支持梁全体を絶縁状態とした。このため、固定側信号電極に供給された高周波信号が可動側信号電極を通じて可動部の内部に伝搬したとしても、可動部から支持部側への高周波信号の漏洩を支持梁によって阻止または抑制することができる。 According to the present invention, the entire support beam is insulative by oxidizing the entire support beam. For this reason, even if the high-frequency signal supplied to the fixed-side signal electrode propagates into the movable part through the movable-side signal electrode, the leakage of the high-frequency signal from the movable part to the support part side is prevented or suppressed by the support beam. Can do.
　また、支持部、支持梁および可動部は単層のシリコン基板を用いて形成したから、厚さ方向において対称な構造を有する可動部の形成が容易となり、可動部の反りの制御をし易くすることができる。このため、可動部の反りを抑制して、可動側信号電極と固定側信号電極との間で静電容量を高精度に設定することができる。さらに、単層のシリコン基板を用いて可動部等を形成するから、可動部の形成工程を簡略化して製造コストを低減することができる。 In addition, since the support portion, the support beam, and the movable portion are formed using a single layer silicon substrate, it is easy to form a movable portion having a symmetric structure in the thickness direction, and to easily control the warp of the movable portion. be able to. For this reason, it is possible to suppress the warp of the movable part and set the capacitance between the movable side signal electrode and the fixed side signal electrode with high accuracy. Furthermore, since the movable part and the like are formed using a single layer silicon substrate, the manufacturing process of the movable part can be simplified and the manufacturing cost can be reduced.
　また、単層のシリコン基板を用いて可動部および支持梁を形成するから、可動部等を形成するときには、例えばＩＣＰ（Inductively Coupled Plasma：誘導結合プラズマ）エッチング等のドライエッチングによってシリコン基板を加工することができる。このため、ウェットエッチングを用いた場合に比べて、可動部および支持梁を高精度に加工することができる。 Further, since the movable portion and the support beam are formed using a single layer silicon substrate, when forming the movable portion or the like, the silicon substrate is processed by dry etching such as ICP (InductivelyductCoupled Plasma) etching, for example. be able to. For this reason, a movable part and a support beam can be processed with high precision compared with the case where wet etching is used.
　さらに、可動部のうち第１の基板と対向した表面には可動側駆動電極を配置し、第２の基板と対向した裏面には可動側信号電極を配置したから、可動部の厚さ方向において対称な位置に例えば導電性金属材料からなる電極をそれぞれ配置することができる。これにより、可動部の両面で熱応力等を同程度にすることができ、可動部の反りを抑制することができる。 Further, since the movable side drive electrode is disposed on the front surface of the movable portion facing the first substrate, and the movable side signal electrode is disposed on the rear surface facing the second substrate, in the thickness direction of the movable portion. For example, electrodes made of a conductive metal material can be arranged at symmetrical positions. Thereby, thermal stress etc. can be made comparable on both surfaces of a movable part, and the curvature of a movable part can be suppressed.
　（２）．本発明では、前記支持梁は、当該支持梁の形状をドライエッチングにより成形した後に酸化処理を施すことにより酸化させることによって形成される構成としてもよい。 (2). In the present invention, the support beam may be formed by forming the shape of the support beam by dry etching and then oxidizing it by performing an oxidation treatment.
　この場合、例えばＩＣＰエッチング等のドライエッチングにより支持梁の形状を成形するから、例えば幅寸法が数μｍ程度の細い支持梁を容易かつ高精度に形成することができる。このため、支持梁のばね定数を高精度に設定することができ、支持梁の設計自由度を高めることができる。また、支持梁は、ドライエッチングによる成形後に例えば加熱処理等を行うことによって容易に酸化処理を施すことができる。このため、複雑で機械的な剛性の弱い微細な支持梁であっても、その全てを確実に酸化させることができ、支持梁の全部を絶縁状態にすることができる。 In this case, since the shape of the support beam is formed by dry etching such as ICP etching, for example, a thin support beam having a width dimension of about several μm can be formed easily and with high accuracy. For this reason, the spring constant of the support beam can be set with high accuracy, and the design flexibility of the support beam can be increased. Further, the support beam can be easily oxidized by, for example, heat treatment after being formed by dry etching. For this reason, even if it is a fine support beam with a complicated and weak mechanical rigidity, all of it can be oxidized reliably, and all of a support beam can be made into an insulation state.
　（３）．本発明では、前記支持梁の各部の幅寸法または厚さ寸法は４μｍ以下としてもよい。 (3). In the present invention, the width or thickness of each part of the support beam may be 4 μm or less.
　このように構成したことにより、例えばシリコン基板を加熱して熱酸化する場合に、酸化層の深さが２μｍ程度で飽和するときでも、支持梁の全部を確実に酸化させることができる。従って、固定側信号電極と可動側信号電極との間に形成された信号経路に供給された高周波信号が可動部から支持梁を介して支持部側へ漏洩することを確実に阻止または抑制することができる。 With this configuration, for example, when the silicon substrate is heated and thermally oxidized, the entire support beam can be reliably oxidized even when the depth of the oxide layer is saturated at about 2 μm. Therefore, the high-frequency signal supplied to the signal path formed between the fixed-side signal electrode and the movable-side signal electrode is reliably prevented or suppressed from leaking from the movable part to the support part side via the support beam. Can do.
本発明の実施形態による可変容量素子を示す縦断面図である。It is a longitudinal cross-sectional view which shows the variable capacitance element by embodiment of this invention. 可動部が変位した状態の可変容量素子を示す縦断面図である。It is a longitudinal cross-sectional view which shows the variable capacitance element of the state which the movable part displaced. 図１中の矢示III－III方向から見た可変容量素子を示す縦断面図である。FIG. 3 is a longitudinal sectional view showing the variable capacitance element as seen from the direction of arrows III-III in FIG. 図１中の矢示IV－IV方向から見た可変容量素子を示す横断面図である。FIG. 4 is a cross-sectional view showing the variable capacitance element as viewed from the direction of arrows IV-IV in FIG. 図１中の矢示V－V方向から見た可変容量素子を示す横断面図である。FIG. 5 is a transverse sectional view showing the variable capacitance element as seen from the direction of arrows VV in FIG. 1. 図１中の矢示VI－VI方向から見た可変容量素子を示す横断面図である。FIG. 5 is a cross-sectional view showing the variable capacitance element as viewed from the direction of arrows VI-VI in FIG. 可変容量素子の支持梁を拡大して示す縦断面図である。It is a longitudinal cross-sectional view which expands and shows the support beam of a variable capacitance element. 可変容量素子の支持梁を拡大して示す横断面図である。It is a cross-sectional view which expands and shows the support beam of a variable capacitance element.
　以下、本発明の実施の形態を図１ないし図８に従って詳細に説明する。図１において、本発明の実施形態による可変容量素子１は、上側ガラス基板２と下側ガラス基板３との間にシリコン基板４を挟み込むことにより形成されている。 Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. In FIG. 1, a variable capacitor 1 according to an embodiment of the present invention is formed by sandwiching a silicon substrate 4 between an upper glass substrate 2 and a lower glass substrate 3.
　上側ガラス基板２は、第１の基板を構成し、例えば絶縁性を有するガラス材料により形成され、図１における左右方向の寸法が例えば数ｍｍ程度の四角形状に形成されている。また、上側ガラス基板２の下面側（裏面側）には、例えばエッチングにより凹陥部２Ａが形成されている。さらに、上側ガラス基板２の下面の周縁部は、後述する固定側導電膜２５および可動側導電膜１２を介してシリコン基板４に接合されている。 The upper glass substrate 2 constitutes a first substrate and is formed of, for example, an insulating glass material, and is formed in a quadrangular shape having a horizontal dimension in FIG. Further, a recess 2A is formed on the lower surface side (back surface side) of the upper glass substrate 2 by etching, for example. Further, the peripheral edge portion of the lower surface of the upper glass substrate 2 is bonded to the silicon substrate 4 via a fixed-side conductive film 25 and a movable-side conductive film 12 described later.
　下側ガラス基板３は、第２の基板を構成し、上側ガラス基板２とほぼ同様に、ガラス材料により四角形状に形成されている。また、下側ガラス基板３の上面側（表面側）には、エッチングにより凹陥部３Ａが形成されている。さらに、下側ガラス基板３の上面の周縁部は、後述する固定側導電膜２６および可動側導電膜１９を介してシリコン基板４に接合されている。 The lower glass substrate 3 constitutes a second substrate, and is formed in a quadrangular shape from a glass material in substantially the same manner as the upper glass substrate 2. Further, a recess 3A is formed on the upper surface side (front surface side) of the lower glass substrate 3 by etching. Further, the peripheral edge portion of the upper surface of the lower glass substrate 3 is bonded to the silicon substrate 4 via a fixed-side conductive film 26 and a movable-side conductive film 19 described later.
　そして、上側ガラス基板２の凹陥部２Ａと下側ガラス基板３の凹陥部３Ａとの間には密閉空間が形成され、この密閉空間内には後述する可動部７、支持梁９、引出電極配設部１０（図３参照）等が収容されている。なお、上側ガラス基板２および下側ガラス基板３を、絶縁性を有する他の材料により形成された基板にそれぞれ置き代えてもよい。 A sealed space is formed between the recessed portion 2A of the upper glass substrate 2 and the recessed portion 3A of the lower glass substrate 3, and a movable portion 7, a support beam 9, and an extraction electrode arrangement, which will be described later, are formed in the sealed space. The installation part 10 (refer FIG. 3) etc. are accommodated. Note that the upper glass substrate 2 and the lower glass substrate 3 may be replaced with substrates formed of other insulating materials.
　シリコン基板４は、例えば単結晶シリコンにより形成された単層の基板であり、シリコン基板４には、後述する支持部５、可動部７、支持梁９、引出電極配設部１０等が例えばＩＣＰエッチング等のドライエッチングにより形成されている。 The silicon substrate 4 is a single-layer substrate made of, for example, single crystal silicon. The silicon substrate 4 includes a support portion 5, a movable portion 7, a support beam 9, an extraction electrode arrangement portion 10 and the like, which will be described later, for example, an ICP. It is formed by dry etching such as etching.
　支持部５は、シリコン基板４に形成され、上側ガラス基板２および下側ガラス基板３に固定されている。支持部５は、図４に示すように、四角形の枠状に形成され、可動部７を取り囲んでいる。また、支持部５は、図１に示すように、例えば５０μｍないし３００μｍ程度の厚さ寸法を有する。 The support portion 5 is formed on the silicon substrate 4 and is fixed to the upper glass substrate 2 and the lower glass substrate 3. As shown in FIG. 4, the support part 5 is formed in a rectangular frame shape and surrounds the movable part 7. Further, as shown in FIG. 1, the support portion 5 has a thickness dimension of about 50 μm to 300 μm, for example.
　また、支持部５の上面側、下面側、外側に向いた側面側、および内側に向いた側面側には、絶縁膜６が形成されている。即ち、支持部５は、後述する支持梁９が接続された部位を除き、シリコン酸化膜からなる絶縁膜６により覆われている。絶縁膜６の厚さ寸法はおよそ２μｍである。 Also, an insulating film 6 is formed on the upper surface side, the lower surface side, the side surface facing outward, and the side surface facing inward of the support portion 5. That is, the support portion 5 is covered with an insulating film 6 made of a silicon oxide film except for a portion to which a support beam 9 described later is connected. The thickness dimension of the insulating film 6 is about 2 μm.
　また、支持部５（絶縁膜６）の上面（表面）は、後述する可動側導電膜１２および固定側導電膜２５を介して上側ガラス基板２の下面周縁部と密着している。また、支持部５（絶縁膜６）の下面（裏面）は、後述する可動側導電膜１９および固定側導電膜２６を介して下側ガラス基板３の上面周縁部と密着している。 Further, the upper surface (front surface) of the support portion 5 (insulating film 6) is in close contact with the lower surface peripheral portion of the upper glass substrate 2 through the movable-side conductive film 12 and the fixed-side conductive film 25 described later. Further, the lower surface (back surface) of the support portion 5 (insulating film 6) is in close contact with the upper surface peripheral portion of the lower glass substrate 3 through the movable conductive film 19 and the fixed conductive film 26 described later.
　可動部７は、シリコン基板４に形成され、後述する支持梁９を用いて支持部５に支持されている。可動部７は、図４に示すように四角形状の平板状に形成されている。また、可動部７の厚さ寸法は、図１に示すように、支持部５の厚さ寸法とほぼ等しいか、あるいは支持部５の厚さ寸法よりも数μｍないし数十μｍ程度小さい。また、可動部７は、上側ガラス基板２の凹陥部２Ａおよび下側ガラス基板３の凹陥部３Ａにより可変容量素子１の内部に形成された密閉空間内において厚さ方向（図１において上下方向）に変位することができる。 The movable part 7 is formed on the silicon substrate 4 and supported by the support part 5 using a support beam 9 described later. As shown in FIG. 4, the movable part 7 is formed in a rectangular flat plate shape. Further, as shown in FIG. 1, the thickness dimension of the movable part 7 is substantially equal to the thickness dimension of the support part 5, or about several μm to several tens μm smaller than the thickness dimension of the support part 5. In addition, the movable portion 7 has a thickness direction (vertical direction in FIG. 1) in a sealed space formed inside the variable capacitor 1 by the recessed portion 2A of the upper glass substrate 2 and the recessed portion 3A of the lower glass substrate 3. Can be displaced.
　また、可動部７の上面側、下面側および側面側には、絶縁膜８が形成されている。即ち、可動部７は、後述する支持梁９が接続された部位を除き、シリコン酸化膜からなる絶縁膜８により覆われている。絶縁膜８の厚さ寸法はおよそ２μｍである。 Further, an insulating film 8 is formed on the upper surface side, the lower surface side, and the side surface side of the movable portion 7. That is, the movable portion 7 is covered with the insulating film 8 made of a silicon oxide film except for a portion where a support beam 9 described later is connected. The thickness dimension of the insulating film 8 is about 2 μm.
　支持梁９は、図４に示すように支持部５と可動部７との間に例えば４本設けられ、図１に示すように可動部７を厚さ方向に変位可能に支持している。また、各支持梁９は、その基端側が支持部５に連結されると共に、その先端側が上側ガラス基板２，３とほぼ平行に伸びて可動部７の角隅にそれぞれ連結されている。 For example, four support beams 9 are provided between the support portion 5 and the movable portion 7 as shown in FIG. 4, and support the movable portion 7 so as to be displaceable in the thickness direction as shown in FIG. Each support beam 9 has a base end connected to the support portion 5 and a distal end extending substantially parallel to the upper glass substrates 2 and 3 and connected to the corners of the movable portion 7.
　また、各支持梁９は、上側ガラス基板２、下側ガラス基板３とそれぞれ離間しており、厚さ方向に対して捩れ変形または撓み変形することにより、可動部７を厚さ方向に変位させることができる。このため、各支持梁９は、図４に示すように、厚さ方向に対して撓み変形等が容易な形状として、例えばクランク状またはミアンダ状に屈曲した形状を有している。そして、図７に示すように、各支持梁９の厚さ寸法ｄ1は、支持部５の厚さ寸法よりも小さい値として例えば５０μｍ以下の値に設定されている。なお、支持梁９の厚さ寸法ｄ1は、支持部５の厚さ寸法と同じ値でもよい。 Each support beam 9 is separated from the upper glass substrate 2 and the lower glass substrate 3, respectively, and displaces the movable part 7 in the thickness direction by being twisted or bent in the thickness direction. be able to. For this reason, as shown in FIG. 4, each support beam 9 has a shape bent in a crank shape or a meander shape, for example, as a shape that can be easily bent and deformed in the thickness direction. As shown in FIG. 7, the thickness dimension d1 of each support beam 9 is set to a value smaller than the thickness dimension of the support portion 5, for example, 50 μm or less. The thickness dimension d1 of the support beam 9 may be the same value as the thickness dimension of the support portion 5.
　また、各支持梁９は、図８に示すように、その各所の幅寸法ｄ2が４μｍ以下、より具体的にはおよそ２μｍないし３μｍである。そして、各支持梁９は、その全部が酸化シリコンにより形成されており、各支持梁９の各所が絶縁性を有する。 Further, as shown in FIG. 8, each support beam 9 has a width dimension d2 of 4 μm or less, more specifically about 2 μm to 3 μm. Each support beam 9 is entirely formed of silicon oxide, and each part of each support beam 9 has an insulating property.
　ここで、各支持梁９は、シリコン基板４にＩＣＰエッチングを施し、厚さ寸法ｄ1を有し、かつ幅寸法ｄ2を有するクランク状またはミアンダ状の形状を成形した後に熱酸化処理を施すことにより形成されている。 Here, each support beam 9 is obtained by subjecting the silicon substrate 4 to ICP etching, forming a crank shape or meander shape having a thickness dimension d1 and a width dimension d2, and then performing a thermal oxidation treatment. Is formed.
　ここで、シリコン基板を加熱処理してシリコン基板の外表面に熱酸化による絶縁膜（シリコン酸化膜）を形成する場合、絶縁膜の厚さ寸法がおよそ２μｍに達するまでは、熱酸化処理を継続する時間に対応して、形成される絶縁膜の厚さ寸法が増加する。しかし、絶縁膜の厚さ寸法がおよそ２μｍに達した後は、熱酸化処理を継続する時間に比して、形成される絶縁膜の厚さ寸法がほとんど増加しなくなる。この点を考慮し、本発明の実施形態による可変容量素子１では、各支持梁９の幅寸法ｄ2を２μｍの２倍の４μｍ以下に設定し、各支持梁９の全部を短時間（製品の製造を効率良く行うのに許容される時間内）で酸化させ、各支持梁９の各所に絶縁性を持たせている。 Here, when an insulating film (silicon oxide film) is formed by thermal oxidation on the outer surface of the silicon substrate by heat treatment, the thermal oxidation process is continued until the thickness dimension of the insulating film reaches about 2 μm. The thickness dimension of the insulating film to be formed increases corresponding to the time to perform. However, after the thickness dimension of the insulating film reaches approximately 2 μm, the thickness dimension of the insulating film to be formed hardly increases compared to the time for which the thermal oxidation process is continued. In consideration of this point, in the variable capacitance element 1 according to the embodiment of the present invention, the width dimension d2 of each support beam 9 is set to 4 μm or less, which is twice 2 μm, and the entire support beam 9 is set in a short time (product Oxidation is performed within a time allowed for efficient production), and each support beam 9 is insulative.
　図３において、引出電極配設部１０は、上側ガラス基板２の凹陥部２Ａおよび下側ガラス基板３の凹陥部３Ａにより可変容量素子１の内部に形成された密閉空間内に設けられ、支持部５に連結されている。引出電極配設部１０は、後述する可動側駆動電極１３と固定側駆動電極１４との間に印加する駆動電圧の供給経路である駆動用引出電極１６を配設するための部位である。また、引出電極配設部１０は、支持部５および可動部７とほぼ同様に、およそ２μｍの厚さ寸法を有するシリコン酸化膜からなる絶縁膜１１により覆われている。 In FIG. 3, the extraction electrode arrangement portion 10 is provided in a sealed space formed inside the variable capacitor 1 by the recessed portion 2 </ b> A of the upper glass substrate 2 and the recessed portion 3 </ b> A of the lower glass substrate 3. 5 is connected. The extraction electrode disposing unit 10 is a part for disposing a driving extraction electrode 16 that is a supply path of a driving voltage to be applied between a movable driving electrode 13 and a fixed driving electrode 14 described later. In addition, the extraction electrode arrangement portion 10 is covered with an insulating film 11 made of a silicon oxide film having a thickness dimension of about 2 μm, in the same manner as the support portion 5 and the movable portion 7.
　第１の可動側導電膜１２は、図１および図３に示すように、例えば金または金を含む合金等の金属材料により形成された導電性を有する薄膜であり、例えばスパッタ、蒸着法等を用いて形成されている。また、第１の可動側導電膜１２は、支持部５、可動部７、支持梁９および引出電極配設部１０の上面側に形成されている。そして、これら可動側導電膜１２のうち、可動部７の上面側に設けられた可動側導電膜１２が可動側駆動電極１３となっている。 As shown in FIGS. 1 and 3, the first movable conductive film 12 is a conductive thin film formed of a metal material such as gold or an alloy containing gold. It is formed using. The first movable conductive film 12 is formed on the upper surface side of the support portion 5, the movable portion 7, the support beam 9, and the extraction electrode arrangement portion 10. Among these movable conductive films 12, the movable conductive film 12 provided on the upper surface side of the movable portion 7 serves as the movable drive electrode 13.
　また、可動側導電膜１２は、支持部５から各支持梁９を介して可動部７に至るまで途中で物理的に切断されることなく連続して形成されている。これにより、可動側駆動電極１３は、各支持梁９の上面側に設けられた可動側導電膜１２を介して支持部５の上面側に設けられた可動側導電膜１２に電気的に接続されている。さらに、支持部５の上面側に設けられた可動側導電膜１２は、後述する駆動用引出電極１５に電気的に接続されている（図３参照）。一方、引出電極配設部１０の上面側に設けられた可動側導電膜１２は、他の部位に設けられた可動側導電膜１２（可動側駆動電極１３を含む）と物理的に切断され、かつ離間している。 Further, the movable-side conductive film 12 is continuously formed without being physically cut halfway from the support portion 5 through the support beams 9 to the movable portion 7. Thus, the movable drive electrode 13 is electrically connected to the movable conductive film 12 provided on the upper surface side of the support portion 5 via the movable conductive film 12 provided on the upper surface side of each support beam 9. ing. Furthermore, the movable conductive film 12 provided on the upper surface side of the support portion 5 is electrically connected to a drive lead electrode 15 described later (see FIG. 3). On the other hand, the movable-side conductive film 12 provided on the upper surface side of the extraction electrode arrangement portion 10 is physically cut off from the movable-side conductive film 12 (including the movable-side drive electrode 13) provided in other parts, And separated.
　固定側駆動電極１４は、図１、図３および図５に示すように、例えば金または金を含む合金等の金属材料により形成された導電性を有する薄膜であり、上側ガラス基板２の下面（凹陥部２Ａの底面）に、例えばスパッタ、蒸着法等を用いて設けられ、可動側駆動電極１３と対向する位置に配置されている。そして、固定側駆動電極１４と可動側駆動電極１３との間には、図１に示すように空間Ｓ1が形成されている。また、固定側駆動電極１４は、図３に示すように引出電極配設部１０の上面側に設けられた可動側導電膜１２と連結しており、これにより、両者は電気的に接続されている。さらに、引出電極配設部１０の上面側に設けられた可動側導電膜１２は、後述する駆動用引出電極１６に電気的に接続されている（図３参照）。 As shown in FIGS. 1, 3 and 5, the fixed-side drive electrode 14 is a conductive thin film formed of a metal material such as gold or an alloy containing gold, and the lower surface ( The bottom surface of the recessed portion 2A is provided by using, for example, sputtering, vapor deposition or the like, and is disposed at a position facing the movable drive electrode 13. A space S1 is formed between the fixed drive electrode 14 and the movable drive electrode 13 as shown in FIG. Further, as shown in FIG. 3, the fixed side drive electrode 14 is connected to the movable side conductive film 12 provided on the upper surface side of the extraction electrode disposition portion 10, so that both are electrically connected. Yes. Furthermore, the movable conductive film 12 provided on the upper surface side of the extraction electrode placement portion 10 is electrically connected to a drive extraction electrode 16 described later (see FIG. 3).
　第１の駆動用引出電極１５は、図３に示すように、下側ガラス基板３と支持部５との双方を厚さ方向に貫通して穿設されたビアホール（スルーホール）内に銅等の導電性金属材料を充填することにより形成されている。駆動用引出電極１５の上端側は、支持部５の上面側および各支持梁９の上面に連続して設けられた可動側導電膜１２を介して可動側駆動電極１３に電気的に接続され、下端側は、外部の駆動電圧供給回路３１と接続可能な接続端子となっている。 As shown in FIG. 3, the first drive lead electrode 15 is made of copper or the like in a via hole (through hole) drilled through both the lower glass substrate 3 and the support portion 5 in the thickness direction. It is formed by filling the conductive metal material. The upper end side of the drive lead electrode 15 is electrically connected to the movable drive electrode 13 via the movable conductive film 12 provided continuously on the upper surface side of the support portion 5 and the upper surface of each support beam 9, The lower end side is a connection terminal that can be connected to an external drive voltage supply circuit 31.
　第２の駆動用引出電極１６は、下側ガラス基板３と引出電極配設部１０との双方を厚さ方向に貫通して穿設されたビアホール（スルーホール）内に銅等の導電性金属材料を充填することにより形成されている。駆動用引出電極１６の上端側は、引出電極配設部１０の上面側に設けられた可動側導電膜１２を介して固定側駆動電極１４に電気的に接続され、下端側は、外部の駆動電圧供給回路３１と接続可能な接続端子となっている。 The second drive lead electrode 16 is made of a conductive metal such as copper in a via hole (through hole) drilled through both the lower glass substrate 3 and the lead electrode placement portion 10 in the thickness direction. It is formed by filling the material. The upper end side of the drive extraction electrode 16 is electrically connected to the fixed drive electrode 14 via the movable conductive film 12 provided on the upper surface side of the extraction electrode arrangement portion 10, and the lower end side is externally driven. This is a connection terminal that can be connected to the voltage supply circuit 31.
　上側ストッパ１７は、図３および図５に示すように、上側ガラス基板２の下面（凹陥部２Ａの底面）にエッチングにより形成された絶縁性を有する複数の突起である。そして、上側ストッパ１７は、固定側駆動電極１４よりも可動部７側（下側）に向けて突出している。これにより、上側ストッパ１７は、可動側駆動電極１３と固定側駆動電極１４とが短絡するのを防止している。 The upper stopper 17 is a plurality of insulating protrusions formed by etching on the lower surface of the upper glass substrate 2 (the bottom surface of the recessed portion 2A), as shown in FIGS. The upper stopper 17 protrudes toward the movable portion 7 (lower side) with respect to the fixed drive electrode 14. Thereby, the upper stopper 17 prevents the movable drive electrode 13 and the fixed drive electrode 14 from being short-circuited.
　下側ストッパ１８は、図３および図６に示すように、下側ガラス基板３の上面（凹陥部３Ａの底面）にエッチングにより形成された絶縁性を有する複数の突起である。そして、下側ストッパ１８は、後述する固定側信号電極２１よりも可動部７側（上側）に向けて突出している。これにより、下側ストッパ１８は、可動側信号電極２０と固定側信号電極２１，２２とが短絡するのを防止すると共に、可動側信号電極２０と固定側信号電極２１，２２との間の静電容量の最大値を設定している。 3 and 6, the lower stopper 18 is a plurality of insulating projections formed by etching on the upper surface of the lower glass substrate 3 (the bottom surface of the recessed portion 3A). And the lower side stopper 18 protrudes toward the movable part 7 side (upper side) rather than the fixed side signal electrode 21 mentioned later. As a result, the lower stopper 18 prevents the movable signal electrode 20 and the fixed signal electrodes 21 and 22 from being short-circuited, and the static stopper between the movable signal electrode 20 and the fixed signal electrodes 21 and 22. The maximum capacity is set.
　一方、第２の可動側導電膜１９は、図１および図３に示すように、第１の可動側導電膜１２と同様な金等の導電性金属材料により形成された薄膜であり、例えばスパッタ、蒸着法等を用いて形成されている。また、第２の可動側導電膜１９は、支持部５、可動部７、支持梁９および引出電極配設部１０の下面側に形成されている。そして、可動側導電膜１９のうち、可動部７の下面側に設けられた可動側導電膜１９が可動側信号電極２０となっている。 On the other hand, as shown in FIGS. 1 and 3, the second movable-side conductive film 19 is a thin film formed of a conductive metal material such as gold similar to the first movable-side conductive film 12, and is formed by sputtering, for example. , Using a vapor deposition method or the like. Further, the second movable-side conductive film 19 is formed on the lower surface side of the support portion 5, the movable portion 7, the support beam 9, and the extraction electrode arrangement portion 10. Of the movable conductive film 19, the movable conductive film 19 provided on the lower surface side of the movable portion 7 serves as the movable signal electrode 20.
　また、可動側導電膜１９は、図１に示すように、支持部５と各支持梁９との境界部分および各支持梁９と可動部７との境界部分で物理的に切断されている。これにより、可動側信号電極２０は、各支持梁９の下面側に設けられた可動側導電膜１９とも、支持部５の下面側に設けられた可動側導電膜１９とも電気的に遮断されている。また、引出電極配設部１０の下面側に設けられた可動側導電膜１９も、他の部位に設けられた可動側導電膜１９（可動側信号電極２０を含む）と物理的に切断され、かつ電気的に遮断されている。さらに、可動側導電膜１９（可動側信号電極２０）と可動側導電膜１２（可動側駆動電極１３）との間は、絶縁膜６，８，１１によって電気的に遮断されている。 Further, as shown in FIG. 1, the movable conductive film 19 is physically cut at the boundary portion between the support portion 5 and each support beam 9 and at the boundary portion between each support beam 9 and the movable portion 7. Thereby, the movable-side signal electrode 20 is electrically cut off from the movable-side conductive film 19 provided on the lower surface side of each support beam 9 and the movable-side conductive film 19 provided on the lower surface side of the support portion 5. Yes. In addition, the movable conductive film 19 provided on the lower surface side of the extraction electrode placement portion 10 is also physically cut from the movable conductive film 19 (including the movable signal electrode 20) provided in other parts, And it is electrically cut off. Further, the movable side conductive film 19 (movable side signal electrode 20) and the movable side conductive film 12 (movable side drive electrode 13) are electrically cut off by the insulating films 6, 8, and 11.
　また、可動側駆動電極１３と可動側信号電極２０とはほぼ等しい厚さ寸法を有する。これにより、可動部７の構造がその厚さ方向において対称となっている。 The movable side drive electrode 13 and the movable side signal electrode 20 have substantially the same thickness. Thereby, the structure of the movable part 7 is symmetrical in the thickness direction.
　図１および図６において、第１の固定側信号電極２１および第２の固定側信号電極２２はそれぞれ、例えば金または金を含む合金等の金属材料により形成された導電性を有する薄膜であり、下側ガラス基板３の上面（凹陥部３Ａの底面）に、例えばスパッタ、蒸着法等を用いて設けられ、可動側信号電極２０と対向する位置に配置されている。そして、固定側信号電極２１，２２と可動側信号電極２０との間には空間Ｓ2が形成されている。また、固定側信号電極２１と固定側信号電極２２とは互いに十分に離間しているため、高周波信号が固定側信号電極２１と固定側信号電極２２との間を、後述する信号経路を介さずに、直接流通したり、漏洩したりすることはない。 In FIG. 1 and FIG. 6, each of the first fixed-side signal electrode 21 and the second fixed-side signal electrode 22 is a conductive thin film formed of a metal material such as gold or an alloy containing gold, for example. The lower glass substrate 3 is provided on the upper surface (the bottom surface of the recessed portion 3 </ b> A) using, for example, sputtering, vapor deposition, or the like, and is disposed at a position facing the movable signal electrode 20. A space S2 is formed between the fixed signal electrodes 21 and 22 and the movable signal electrode 20. Further, since the fixed side signal electrode 21 and the fixed side signal electrode 22 are sufficiently separated from each other, the high frequency signal does not pass between the fixed side signal electrode 21 and the fixed side signal electrode 22 via a signal path described later. In addition, there is no direct distribution or leakage.
　第１の信号用引出電極２３および第２の信号用引出電極２４はそれぞれ、図１に示すように、下側ガラス基板３を厚さ方向に貫通して穿設されたビアホール（スルーホール）内に銅等の導電性金属材料を充填することにより形成されている。信号用引出電極２３の上端側は、固定側信号電極２１に電気的に接続され、下端側は、外部の高周波回路等と接続可能な接続端子となっている。また、信号用引出電極２４の上端側は、固定側信号電極２２に電気的に接続され、下端側は、外部の高周波回路等と接続可能な接続端子となっている。 As shown in FIG. 1, each of the first signal extraction electrode 23 and the second signal extraction electrode 24 is in a via hole (through hole) formed through the lower glass substrate 3 in the thickness direction. It is formed by filling a conductive metal material such as copper. The upper end side of the signal extraction electrode 23 is electrically connected to the fixed-side signal electrode 21, and the lower end side is a connection terminal that can be connected to an external high-frequency circuit or the like. Further, the upper end side of the signal extraction electrode 24 is electrically connected to the fixed-side signal electrode 22, and the lower end side is a connection terminal that can be connected to an external high-frequency circuit or the like.
　第１の固定側導電膜２５は、上側ガラス基板２の下面の周縁部に、例えばスパッタ、蒸着法を用いて設けられている。そして、上側ガラス基板２は、固定側導電膜２５と、支持部５の上面側に設けられた可動側導電膜１２とを熱圧着することにより、支持部５と圧着接合されている。 The first fixed-side conductive film 25 is provided on the periphery of the lower surface of the upper glass substrate 2 by using, for example, sputtering or vapor deposition. The upper glass substrate 2 is bonded to the support portion 5 by thermocompression bonding of the fixed-side conductive film 25 and the movable conductive film 12 provided on the upper surface side of the support portion 5.
　第２の固定側導電膜２６は、下側ガラス基板３の上面の周縁部に、例えばスパッタ、蒸着法等を用いて設けられている。そして、下側ガラス基板３は、固定側導電膜２６と、支持部５の下面側に設けられた可動側導電膜１９とを熱圧着することにより、支持部５と圧着接合されている。 The second fixed-side conductive film 26 is provided on the periphery of the upper surface of the lower glass substrate 3 by using, for example, sputtering, vapor deposition or the like. The lower glass substrate 3 is bonded to the support portion 5 by thermocompression bonding of the fixed-side conductive film 26 and the movable-side conductive film 19 provided on the lower surface side of the support portion 5.
　本発明の実施形態による可変容量素子１は以上のような構成を有するものであり、次にこの製造方法を説明する。 The variable capacitance element 1 according to the embodiment of the present invention has the above-described configuration, and this manufacturing method will be described next.
　まず、シリコン基板４の下面側からエッチングを施し、シリコン基板４のうち支持梁９に対応する部位を薄く加工する。次に、シリコン基板４の上面側から例えばＩＣＰエッチングを施し、支持部５、可動部７、各支持梁９、引出電極配設部１０の形状を成形する（シリコン基板成形工程）。また、この工程で、駆動用引出電極１５を設けるためのビアホールを支持部５に形成すると共に、駆動用引出電極１６を設けるためのビアホールを引出電極配設部１０に形成する。 First, etching is performed from the lower surface side of the silicon substrate 4, and a portion corresponding to the support beam 9 in the silicon substrate 4 is thinly processed. Next, for example, ICP etching is performed from the upper surface side of the silicon substrate 4 to shape the shapes of the support portion 5, the movable portion 7, each support beam 9, and the extraction electrode arrangement portion 10 (silicon substrate forming step). In this step, a via hole for providing the driving lead electrode 15 is formed in the support portion 5 and a via hole for providing the driving lead electrode 16 is formed in the lead electrode arrangement portion 10.
　続いて、このシリコン基板４を加熱して熱酸化処理を施す。これにより、シリコン基板４には、厚さ寸法がおよそ２μｍの絶縁膜６、８、１１を形成すると同時に、各所の幅寸法が４μｍ以下の各支持梁９の全部を酸化させる（酸化工程）。 Subsequently, the silicon substrate 4 is heated and subjected to thermal oxidation treatment. As a result, insulating films 6, 8, and 11 having a thickness of about 2 μm are formed on the silicon substrate 4, and at the same time, all of the support beams 9 having a width of 4 μm or less are oxidized (oxidation process).
　続いて、蒸着法を用いて、支持部５、可動部７、引出電極配設部１０のそれぞれの上面側および各支持梁９の上面に可動側導電膜１２を設ける。このとき、メタルマスク等を用いて、可動側導電膜１２のうち引出電極配設部１０に対応した部位と、他の部位とを分離する。また、可動部７の上面側には可動側駆動電極１３が形成される。さらに、蒸着法を用いて、支持部５、可動部７、引出電極配設部１０等のそれぞれの下面側に可動側導電膜１９を設ける。これにより、可動部７の下面側には可動側信号電極２０が形成される（可動側電極形成工程）。 Subsequently, the movable-side conductive film 12 is provided on the upper surface side of each of the support portion 5, the movable portion 7, and the extraction electrode placement portion 10 and on the upper surface of each support beam 9 by vapor deposition. At this time, using a metal mask or the like, the portion corresponding to the extraction electrode placement portion 10 in the movable conductive film 12 is separated from other portions. A movable drive electrode 13 is formed on the upper surface side of the movable portion 7. Furthermore, the movable-side conductive film 19 is provided on each lower surface side of the support portion 5, the movable portion 7, the extraction electrode arrangement portion 10, and the like by using a vapor deposition method. Thereby, the movable side signal electrode 20 is formed on the lower surface side of the movable portion 7 (movable side electrode forming step).
　一方、上側ガラス基板２にエッチングを施すことにより凹陥部２Ａおよび上側ストッパ１７を成形し、さらに、スパッタ、蒸着法等を用いて固定側可動電極１４および固定側導電膜２５を上側ガラス基板２に設ける（第１のガラス基板形成工程）。 On the other hand, the recessed portion 2A and the upper stopper 17 are formed by etching the upper glass substrate 2, and the fixed movable electrode 14 and the fixed conductive film 25 are formed on the upper glass substrate 2 by sputtering, vapor deposition or the like. Provided (first glass substrate forming step).
　他方、下側ガラス基板３にエッチングを施すことにより凹陥部３Ａおよび下側ストッパ１８を成形し、さらに、レーザー加工、マイクロブラスト法等を用いて駆動用引出電極１５，１６および信号用引出電極２３，２４を設けるためのビアホールを下側ガラス基板３にそれぞれ形成し、さらに、スパッタ、蒸着法等を用いて固定側信号電極２１，２２および固定側導電膜２６を下側ガラス基板３に設ける（第２のガラス基板形成工程）。 On the other hand, the recessed portion 3A and the lower stopper 18 are formed by etching the lower glass substrate 3, and the drive extraction electrodes 15 and 16 and the signal extraction electrode 23 are formed using laser processing, microblasting, or the like. , 24 are formed in the lower glass substrate 3, and the fixed signal electrodes 21 and 22 and the fixed conductive film 26 are formed in the lower glass substrate 3 by sputtering, vapor deposition or the like ( Second glass substrate forming step).
　続いて、シリコン基板成形工程、酸化工程および可動側電極形成工程を経たシリコン基板４の上面側と、第１のガラス基板形成工程を経た上側ガラス基板２の下面側とを圧着接合する（第１の基板接合工程）。 Subsequently, the upper surface side of the silicon substrate 4 that has undergone the silicon substrate forming step, the oxidation step, and the movable electrode forming step and the lower surface side of the upper glass substrate 2 that has undergone the first glass substrate forming step are pressure bonded. Substrate bonding step).
　続いて、シリコン基板４の下面側と、第２のガラス基板形成工程を経た下側ガラス基板３の上面側とを圧着接合する（第２の基板接合工程）。 Subsequently, the lower surface side of the silicon substrate 4 and the upper surface side of the lower glass substrate 3 that has undergone the second glass substrate forming step are bonded by pressure bonding (second substrate bonding step).
　続いて、支持部５と下側ガラス基板３とを貫通するように形成されたビアホールに駆動用引出電極１５を設け、引出電極配設部１０と下側ガラス基板３とを貫通するように形成されたビアホールに駆動用引出電極１６を設け、下側ガラス基板３において固定側信号電極２１，２２の下側にそれぞれ形成されたビアホールに信号用引出電極２３，２４をそれぞれ設ける（引出電極形成工程）。 Subsequently, a drive extraction electrode 15 is provided in the via hole formed so as to penetrate the support portion 5 and the lower glass substrate 3, and is formed so as to penetrate the extraction electrode arrangement portion 10 and the lower glass substrate 3. The drive lead electrode 16 is provided in the formed via hole, and the signal lead electrodes 23 and 24 are provided in the via holes respectively formed below the fixed side signal electrodes 21 and 22 in the lower glass substrate 3 (lead electrode forming step). ).
　次に、可変容量素子１の基本動作を説明する。即ち、駆動電圧供給回路３１の一方の出力端子は、駆動用引出電極１５を介して可動側駆動電極１３に接続され、他方の出力端子は、駆動用引出電極１６を介して固定側駆動電極１４に接続されている。これにより、駆動電圧供給回路３１から出力される駆動電圧は、可動側駆動電極１３と固定側駆動電極１４との間に印加される。 Next, the basic operation of the variable capacitance element 1 will be described. That is, one output terminal of the drive voltage supply circuit 31 is connected to the movable drive electrode 13 via the drive lead electrode 15, and the other output terminal is connected to the fixed drive electrode 14 via the drive lead electrode 16. It is connected to the. As a result, the drive voltage output from the drive voltage supply circuit 31 is applied between the movable drive electrode 13 and the fixed drive electrode 14.
　また、高周波回路の一方の端子は信号用引出電極２３を介して固定側信号電極２１に接続され、他方の端子は信号用引出電極２４を介して固定側信号電極２２に接続されている。 Further, one terminal of the high-frequency circuit is connected to the fixed-side signal electrode 21 through the signal extraction electrode 23, and the other terminal is connected to the fixed-side signal electrode 22 through the signal extraction electrode 24.
　そして、駆動電圧供給回路３１から可動側駆動電極１３と固定側駆動電極１４との間への駆動電圧の印加を停止しているときは、図１に示すように、可動部７は初期位置に留まり、可動部７の下面側が下側ストッパ１８に当接した状態で静止している。このとき、固定側信号電極２１と可動側信号電極２０との間の距離および固定側信号電極２２と可動側信号電極２０との間の距離はそれぞれ小さくなるため、固定側信号電極２１と固定側信号電極２２との間の静電容量は大きくなる。これにより、高周波回路から供給される高周波信号は、図１中の矢示Ａで示すように、固定側信号電極２１、可動側信号電極２０および固定側信号電極２２を順次直列に接続した信号経路を通じて伝送する。 When the application of the drive voltage from the drive voltage supply circuit 31 to the movable drive electrode 13 and the fixed drive electrode 14 is stopped, as shown in FIG. It stays and is stationary with the lower surface side of the movable part 7 in contact with the lower stopper 18. At this time, the distance between the fixed-side signal electrode 21 and the movable-side signal electrode 20 and the distance between the fixed-side signal electrode 22 and the movable-side signal electrode 20 are reduced. The capacitance between the signal electrode 22 and the signal electrode 22 increases. Thereby, the high-frequency signal supplied from the high-frequency circuit is a signal path in which the fixed-side signal electrode 21, the movable-side signal electrode 20, and the fixed-side signal electrode 22 are sequentially connected in series as shown by an arrow A in FIG. Transmit through.
　一方、駆動電圧供給回路３１から可動側駆動電極１３と固定側駆動電極１４との間に駆動電極を印加すると、可動側駆動電極１３と固定側駆動電極１４との間に静電引力が発生する。この静電引力により、可動部７は、図２に示すように、各支持梁９をそのばね力に抗して撓み変形させつつ初期位置から上方向に変位し、可動部７の上面側が上側ストッパ１７に当接した状態で静止する。このとき、固定側信号電極２１と可動側信号電極２０との間の距離および固定側信号電極２２と可動側信号電極２０との間の距離はそれぞれ大きくなるため、固定側信号電極２１と固定側信号電極２２との間の静電容量は小さくなる。このため、高周波回路から供給される高周波信号は、可動側信号電極２０と固定側信号電極２１，２２との間で遮断される。 On the other hand, when a drive electrode is applied between the movable drive electrode 13 and the fixed drive electrode 14 from the drive voltage supply circuit 31, an electrostatic attractive force is generated between the movable drive electrode 13 and the fixed drive electrode 14. . Due to this electrostatic attraction, the movable portion 7 is displaced upward from the initial position while flexibly deforming each support beam 9 against its spring force, as shown in FIG. Still in contact with the stopper 17. At this time, the distance between the fixed-side signal electrode 21 and the movable-side signal electrode 20 and the distance between the fixed-side signal electrode 22 and the movable-side signal electrode 20 are increased. The capacitance between the signal electrode 22 and the signal electrode 22 becomes small. For this reason, the high-frequency signal supplied from the high-frequency circuit is blocked between the movable-side signal electrode 20 and the fixed- side signal electrodes 21 and 22.
　続いて、この駆動電極の印加を再び停止すると、可動側駆動電極１３と固定側駆動電極１４との間に静電引力が消失する。これにより、可動部７は、図１に示すように、各支持梁９のばね力により下方向に変位し、初期位置に戻る。これにより、固定側信号電極２１と可動側信号電極２０との間の距離および固定側信号電極２２と可動側信号電極２０との間の距離はそれぞれ小さくなるため、固定側信号電極２１と固定側信号電極２２との間の静電容量は大きくなり、固定側信号電極２１，２２間での高周波信号の伝送が再開される。 Subsequently, when the application of the drive electrode is stopped again, the electrostatic attractive force disappears between the movable drive electrode 13 and the fixed drive electrode 14. Thereby, as shown in FIG. 1, the movable part 7 is displaced downward by the spring force of each support beam 9, and returns to the initial position. As a result, the distance between the fixed side signal electrode 21 and the movable side signal electrode 20 and the distance between the fixed side signal electrode 22 and the movable side signal electrode 20 are reduced. The capacitance between the signal electrode 22 and the signal electrode 22 is increased, and transmission of the high-frequency signal between the fixed- side signal electrodes 21 and 22 is resumed.
　このように、本実施形態の可変容量素子１は、可動部７の位置に応じて高周波信号の伝送、停止を切り換えるスイッチ素子として機能する。 Thus, the variable capacitance element 1 of the present embodiment functions as a switch element that switches between transmission and stop of a high-frequency signal according to the position of the movable portion 7.
　次に、可変容量素子１における高周波信号の漏洩抑制効果について説明する。仮に、各支持梁９の全部を酸化させないとすると、各支持梁９の各所にインピーダンスが低い部位が形成されてしまい、固定側信号電極２１、可動側信号電極２０および固定側信号電極２２からなる信号経路を伝送する高周波信号が、図７中の矢示Ｂで示すように、可動側信号電極２０、可動部７、支持梁９を介して支持部５側に漏洩し、さらに、この高周波信号が駆動用引出電極１５に流れ込み、可変容量素子１の外部にさらに漏洩する虞れがある。 Next, the effect of suppressing leakage of high frequency signals in the variable capacitance element 1 will be described. If all of the support beams 9 are not oxidized, portions with low impedance are formed at various portions of the support beams 9, and the fixed signal electrode 21, the movable signal electrode 20, and the fixed signal electrode 22 are formed. A high frequency signal transmitted through the signal path leaks to the support portion 5 side via the movable signal electrode 20, the movable portion 7, and the support beam 9, as indicated by an arrow B in FIG. May flow into the driving extraction electrode 15 and further leak to the outside of the variable capacitance element 1.
　しかしながら、上述したように、可変容量素子１の各支持梁９はその全部が酸化し、各支持梁９の各所が絶縁性を有している。従って、図７中の矢示Ｂ上に×印を付することにより明示した通り、固定側信号電極２１、可動側信号電極２０および固定側信号電極２２からなる信号経路に供給された高周波信号の漏洩は、各支持梁９により、可動部７と支持部５との間で遮断され、または制限される。これにより、可動部７と駆動用引出電極１５との間のアイソレーションが向上している。 However, as described above, all of the support beams 9 of the variable capacitance element 1 are oxidized, and portions of the support beams 9 have insulating properties. Therefore, as clearly shown by putting an X on the arrow B in FIG. 7, the high-frequency signal supplied to the signal path composed of the fixed-side signal electrode 21, the movable-side signal electrode 20, and the fixed-side signal electrode 22 is shown. Leakage is blocked or restricted between the movable part 7 and the support part 5 by each support beam 9. Thereby, the isolation between the movable part 7 and the drive extraction electrode 15 is improved.
　以上説明した通り、本発明の実施形態による可変容量素子１によれば、各支持梁９の全部を酸化させることにより、支持梁９全体を絶縁状態とした。このため、固定側信号電極２１，２２に供給された高周波信号が可動側信号電極２０を通じて可動部７の内部に伝搬したとしても、可動部７から支持部５側への高周波信号の漏洩を支持梁９によって阻止または抑制することができる。 As described above, according to the variable capacitor 1 according to the embodiment of the present invention, the entire support beam 9 is insulated by oxidizing all of the support beams 9. For this reason, even if the high-frequency signal supplied to the fixed- side signal electrodes 21 and 22 propagates through the movable-side signal electrode 20 to the inside of the movable portion 7, it supports leakage of the high-frequency signal from the movable portion 7 to the support portion 5 side. It can be blocked or suppressed by the beam 9.
　また、シリコン基板４として単層のシリコン基板を用いたことにより、厚さ方向において対称な構造を有する可動部７の形成が容易となり、可動部７の反りの制御をし易くすることができる。例えば、可動部７の上面側には、絶縁膜８および可動側駆動電極１３を可動部７の上面全部を覆うようにそれぞれ形成すると共に、可動部７の下面側には、絶縁膜８および可動側信号電極２０を可動部７の下面全部を覆うようにそれぞれ形成する。このとき、可動部７の上面側と下面側とにおいて絶縁膜８の厚さ寸法を互いにほぼ等しくすると共に、可動側駆動電極１３の厚さ寸法と可動側信号電極２０の厚さ寸法とを互いにほぼ等しくする。これにより、可動部７をその厚さ方向において対称な構造とすることができる。 Further, by using a single layer silicon substrate as the silicon substrate 4, it is easy to form the movable portion 7 having a symmetric structure in the thickness direction, and the warpage of the movable portion 7 can be easily controlled. For example, the insulating film 8 and the movable drive electrode 13 are respectively formed on the upper surface side of the movable portion 7 so as to cover the entire upper surface of the movable portion 7, and the insulating film 8 and the movable film are disposed on the lower surface side of the movable portion 7. The side signal electrodes 20 are respectively formed so as to cover the entire lower surface of the movable portion 7. At this time, the thickness dimension of the insulating film 8 is made substantially equal to each other on the upper surface side and the lower surface side of the movable portion 7, and the thickness dimension of the movable drive electrode 13 and the thickness dimension of the movable signal electrode 20 are mutually equal. Make almost equal. Thereby, the movable part 7 can be made into a symmetrical structure in the thickness direction.
　従って、可動部７の上面と下面との間で熱応力等を同程度にすることができるから、可動部７の反りを最低限に抑制することができ、可動側信号電極２０と固定側信号電極２１，２２との間で静電容量を高精度に設定することができる。さらに、単層のシリコン基板４を用いて可動部７等を形成するから、例えば３層基板を用いた場合に比べて、可動部７の形成工程を簡略化して製造コストを低減することができる。 Accordingly, since the thermal stress and the like can be made comparable between the upper surface and the lower surface of the movable portion 7, the warp of the movable portion 7 can be suppressed to the minimum, and the movable-side signal electrode 20 and the fixed-side signal can be suppressed. Capacitance can be set between the electrodes 21 and 22 with high accuracy. Furthermore, since the movable portion 7 and the like are formed using the single-layer silicon substrate 4, for example, the manufacturing process of the movable portion 7 can be simplified and the manufacturing cost can be reduced as compared with the case where a three-layer substrate is used. .
　また、単層のシリコン基板４を用いて可動部７および支持梁９を形成するから、可動部７等を形成するときには、例えばＩＣＰエッチング等のドライエッチングによってシリコン基板４を加工することができる。このため、ウェットエッチングを用いた場合に比べて、可動部７および支持梁９を高精度に加工することができ、例えば幅寸法ｄ2が４μｍ以下の細い支持梁９を容易かつ高精度に形成することができる。 Further, since the movable portion 7 and the support beam 9 are formed using the single layer silicon substrate 4, when forming the movable portion 7 and the like, the silicon substrate 4 can be processed by dry etching such as ICP etching. For this reason, the movable portion 7 and the support beam 9 can be processed with high accuracy compared to the case where wet etching is used. For example, the thin support beam 9 having a width dimension d2 of 4 μm or less can be formed easily and with high accuracy. be able to.
　これにより、支持梁９のばね定数を高精度に設定することができ、支持梁９の設計自由度を高めることができる。また、支持梁９は、ドライエッチングによる成形後に例えば加熱処理等を行うことによって容易に酸化処理を施すことができる。このため、複雑で機械的な剛性の弱い微細な支持梁９であっても、その全てを確実に酸化させることができ、支持梁９の全部を絶縁状態にして、可動部７と支持部５との間のアイソレーションを高めることができる。 Thereby, the spring constant of the support beam 9 can be set with high accuracy, and the design flexibility of the support beam 9 can be increased. Further, the support beam 9 can be easily oxidized by, for example, heat treatment after being formed by dry etching. For this reason, even if the support beam 9 is complicated and has a weak mechanical rigidity, all of the support beam 9 can be surely oxidized. Isolation between the two can be increased.
　なお、前記実施形態では、各支持梁９の厚さ寸法を４μｍより大きく設定し、各支持梁９の幅寸法を４μｍ以下に設定する場合を例にあげたが、本発明はこれに限らない。各支持梁９の厚さ寸法を４μｍ以下に設定し、各支持梁９の幅寸法を４μｍよりも大きく設定してもよい。また、各支持梁９の厚さ寸法および幅寸法をそれぞれ４μｍ以下に設定してもよい。 In the above embodiment, the thickness dimension of each support beam 9 is set to be larger than 4 μm and the width dimension of each support beam 9 is set to 4 μm or less. However, the present invention is not limited to this. . The thickness dimension of each support beam 9 may be set to 4 μm or less, and the width dimension of each support beam 9 may be set to be larger than 4 μm. Moreover, you may set the thickness dimension and width dimension of each support beam 9 to 4 micrometers or less, respectively.
　また、支持梁９の形状を、クランク状およびミアンダ状以外の形状としてもよく、支持梁９の本数も１本ないし３本、または５本以上としてもよい。また、支持梁９を、ＩＣＰエッチング以外のドライエッチングにより形成してもよい。 Further, the shape of the support beam 9 may be a shape other than the crank shape and the meander shape, and the number of the support beams 9 may be 1 to 3, or 5 or more. Further, the support beam 9 may be formed by dry etching other than ICP etching.
　さらに、前記実施形態では、２つの固定側信号電極２１，２２を備える構成とした。しかし、本発明はこれに限らず、下側ガラス基板の上面に単一の固定側信号電極を設けると共に、該固定側信号電極の幅方向両側にグランド電極をそれぞれ設け、これらの固定側信号電極とグランド電極とによってコプレーナ線路を形成する構成としてもよい。 Furthermore, in the said embodiment, it was set as the structure provided with the two fixed side signal electrodes 21 and 22. FIG. However, the present invention is not limited to this, and a single fixed-side signal electrode is provided on the upper surface of the lower glass substrate, and ground electrodes are provided on both sides in the width direction of the fixed-side signal electrode. A coplanar line may be formed by the ground electrode.
　１　可変容量素子
　２　上側ガラス基板（第１の基板）
　３　下側ガラス基板（第２の基板）
　４　シリコン基板
　５　支持部
　７　可動部
　９　支持梁
　１３　可動側駆動電極
　１４　固定側駆動電極
　２０　可動側信号電極
　２１　第１の固定側信号電極
　２２　第２の固定側信号電極 1 variable capacitance element 2 upper glass substrate (first substrate)
3 Lower glass substrate (second substrate)
4 Silicon Substrate 5 Supporting Section 7 Movable Part 9 Supporting Beam 13 Movable Drive Electrode 14 Fixed Drive Electrode 20 Movable Signal Electrode 21 First Fixed Signal Signal 22 Second Fixed Signal Signal

Claims (3)

  1. 　第１の基板と第２の基板との間に設けられた単層のシリコン基板と、
    　前記シリコン基板に形成され、前記第１の基板および前記第２の基板に固定された支持部と、
    　前記シリコン基板に形成され、支持梁を用いて前記支持部に厚さ方向に変位可能に支持された可動部と、
    　前記第１の基板に設けられ、前記可動部と対向する位置に配置された固定側駆動電極と、
    　前記可動部に設けられ、前記固定側駆動電極と対向する位置に配置され、前記固定側駆動電極との間の静電力を作用させるための可動側駆動電極と、
    　前記第２の基板に設けられ、前記可動部と対向する位置に配置された固定側信号電極と、
    　前記可動部に設けられ、前記固定側信号電極と対向する位置に配置された可動側信号電極とを備えた可変容量素子であって、
    　前記支持梁は、その全てを酸化させることによって絶縁状態とし、当該支持梁を用いて、前記固定側信号電極に供給された高周波信号が前記支持部に向けて漏洩するのを防止する構成としたことを特徴とする可変容量素子。     A single layer silicon substrate provided between the first substrate and the second substrate;
    A support formed on the silicon substrate and fixed to the first substrate and the second substrate;
    A movable part formed on the silicon substrate and supported by the support part so as to be displaceable in the thickness direction using a support beam;
    A fixed drive electrode provided on the first substrate and disposed at a position facing the movable portion;
    A movable drive electrode provided in the movable part, disposed at a position facing the fixed drive electrode, and acting on an electrostatic force between the fixed drive electrode;
    A fixed-side signal electrode provided on the second substrate and disposed at a position facing the movable portion;
    A variable capacitance element provided with a movable side signal electrode provided at the movable portion and disposed at a position facing the fixed side signal electrode;
    The support beam is made into an insulating state by oxidizing all of the support beam, and the high-frequency signal supplied to the fixed-side signal electrode is prevented from leaking toward the support portion using the support beam. The variable capacitance element characterized by the above-mentioned.
  2. 　前記支持梁は、当該支持梁の形状をドライエッチングにより成形した後に酸化処理を施すことにより酸化させたものである請求項１に記載の可変容量素子。 2. The variable capacitance element according to claim 1, wherein the support beam is formed by performing oxidation treatment after forming the shape of the support beam by dry etching.
  3. 　前記支持梁の各部の幅寸法または厚さ寸法は４μｍ以下である請求項１に記載の可変容量素子。 The variable capacitance element according to claim 1, wherein a width dimension or a thickness dimension of each part of the support beam is 4 µm or less.
PCT/JP2010/057802 2009-05-29 2010-05-07 Variable capacity element WO2010137447A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1079324A (en) * 1996-09-04 1998-03-24 Murata Mfg Co Ltd Capacitance-variable-element
WO2005027257A1 (en) * 2003-09-08 2005-03-24 Murata Manufacturing Co., Ltd. Variable capacitance element
JP2005340536A (en) * 2004-05-27 2005-12-08 Kyocera Corp Variable capacitor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1079324A (en) * 1996-09-04 1998-03-24 Murata Mfg Co Ltd Capacitance-variable-element
WO2005027257A1 (en) * 2003-09-08 2005-03-24 Murata Manufacturing Co., Ltd. Variable capacitance element
JP2005340536A (en) * 2004-05-27 2005-12-08 Kyocera Corp Variable capacitor

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