JP2010021252A - Variable capacitance element, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable capacitance element can hold a capacitance value even when applied with a shock etc., from outside. <P>SOLUTION: The variable capacitance element 1 is formed using a function layer 4 sandwiched between first and second substrates 2 and 3. In the function layer 4, a support portion 5, a movable portion 6, and a support beam 7 are formed. At this time, the movable portion 6 faces a signal electrode 9 provided to a first substrate 2, and also faces a driving electrode 10 provided to a second substrate 3. Further, a beam pressing portion 12 projecting from the second substrate 3 presses an intermediate reception portion 8 of the support beam 7 against the first substrate 2. Consequently, the movable portion 6 is energized toward the signal electrode 9 in an initial state to form a narrow gap G1 having a minimum interval size between the movable portion 6 and signal electrode 9. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  In general, the variable capacitance element is used as, for example, a variable capacitance switch, a variable capacitance capacitor, or the like. Such a variable capacitance element has a structure in which a movable portion that can be displaced in the thickness direction is provided on a substrate, and a signal electrode and a drive electrode are provided on the substrate at a position facing the movable portion (for example, Patent Documents). 1 and 2).

  Here, in the variable capacitance elements described in Patent Documents 1 and 2, after a sacrificial layer is formed on the signal electrode and the drive electrode, a movable portion is formed to cover the sacrificial layer. Thereafter, the sacrificial layer is removed by etching or the like, so that the movable portion is released into a hollow structure, and a space is formed between the movable portion and the signal electrode or the like. For this reason, in the initial state where the electrostatic force due to the drive electrode does not act, a wide gap having a maximum interval dimension is formed between the movable portion and the signal electrode. On the other hand, in a driving state in which an electrostatic force is applied by the driving electrode, the movable portion approaches the signal electrode, and the gap between the movable portion and the signal electrode is reduced. Thereby, the variable capacitance element has a configuration in which the capacitance between the movable portion and the signal electrode changes depending on whether or not a DC bias voltage is applied to the drive electrode.

JP 2003-124063 A JP-T-2006-503717

  By the way, in the variable capacitance element described in Patent Documents 1 and 2 described above, the movable portion is held in a hollow state by the spring force of the support beam in the minimum capacitance state where the signal electrode and the movable portion are farthest apart. For this reason, when an external impact or the like acts on the variable capacitance element, there is a problem that the movable portion is easily displaced and the capacitance value changes.

  Further, the variable capacitance elements described in Patent Documents 1 and 2 are configured such that the sacrificial layer is removed after the signal electrode, the sacrificial layer, and the movable portion are formed on the substrate in this order. At this time, although it is necessary to form a stopper for preventing a short circuit between the signal electrode and the movable part, it is difficult to pattern the stopper after the movable part is formed. For this reason, in the prior art, the entire surface of the signal electrode is covered with an insulating film in order to prevent a short circuit between the signal electrode and the movable part. However, when the entire signal electrode is covered with the insulating film in this way, there is a problem that the insulating film is charged by repeated switching (approach and separation of the movable part), and the signal electrode and the movable part are stuck.

  In the prior art, both the signal electrode and the drive electrode are provided on the substrate. At this time, since the movable portion is displaced toward the signal electrode due to electrostatic attraction acting between the driving electrode, the thickness of the sacrificial layer is formed in accordance with the maximum distance between the movable portion and the signal electrode. There is a need to.

  In general, as the sacrificial layer becomes thicker, the unevenness of the lower signal electrode and the unevenness of the sacrificial layer formed thereon do not match. In other words, the unevenness of the movable part formed on the sacrificial layer and the unevenness of the signal electrode facing the movable part do not match, and a gap (air gap) larger than the design value is formed between the movable part and the signal electrode. Is done. For this reason, even when the movable part is closest to the signal electrode, the maximum capacity value as designed cannot be obtained, and there is a problem that the ratio of capacitance change becomes small.

  Further, as the sacrificial layer becomes thicker, the stress applied to the movable part by the sacrificial layer becomes stronger. As a result, after the sacrificial layer is removed, a large warp occurs in the movable part, and the warp dimension may change the distance between the movable part and the signal electrode, and a desired maximum capacitance value may not be obtained. is there.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a variable capacitance element capable of holding a capacitance value even when an impact or the like is applied from the outside, and a method for manufacturing the same. is there.

  Another object of the present invention is to provide a variable capacitance element capable of setting a maximum capacitance value with high accuracy and a method for manufacturing the same.

  In order to solve the above-mentioned problem, the invention of claim 1 is a movable part supported by a supporting part sandwiched between first and second substrates and a supporting beam so as to be displaceable in the thickness direction. And a signal electrode which is provided on the first substrate at a position facing the movable portion, and whose capacitance changes with the movable portion when the movable portion approaches and separates, and the movable portion And a drive electrode that is provided on any one of the first and second substrates at a position opposite to the electrode and drives the movable part in a direction to approach or separate from the signal electrode using electrostatic force. In the variable capacitance element, the second substrate is provided with a beam pressing portion that presses the support beam toward the first substrate, and in an initial state where the electrostatic force due to the drive electrode does not act, the movable portion and the A narrow gap with a minimum gap dimension is formed between the signal electrodes. In the driven state in which the electrostatic force is applied by the drive electrode, between the said signal electrode and the movable unit is characterized in that it has a configuration in which the wide gap widened space dimension is formed.

  According to a second aspect of the present invention, the movable portion is provided with a stopper that protrudes toward the first substrate.

  According to a third aspect of the present invention, there is provided a support portion sandwiched between the first and second substrates, a movable portion supported by the support portion so as to be displaceable in the thickness direction using a support beam, and opposed to the movable portion. A signal electrode that is provided on the first substrate at a position where the electrostatic capacity changes between the movable part when the movable part approaches and separates from the first substrate, and the first electrode at a position facing the movable part. , And a driving electrode that is provided on any one of the second substrates and drives the movable part in a direction approaching or separating from the signal electrode using electrostatic force. A step of forming the signal electrode on the first substrate; a step of covering the signal electrode to form a sacrificial layer; and a function of covering the sacrificial layer and including the movable portion, the support beam, and the support portion. Forming a layer, and removing the sacrificial layer to provide a gap between the signal electrode and the movable part. A step of forming, and the second substrate a beam pressing portion protruding in a state of pressing the support beam from said second substrate is configured to include a step of attaching to the support part.

  According to a fourth aspect of the present invention, the sacrificial layer is provided with a stopper forming hole which is located around the signal electrode and penetrates in the thickness direction. When the functional layer is formed, the movable layer is formed using the stopper forming hole. A stopper that protrudes from the portion toward the first substrate is formed.

  In a fifth aspect of the present invention, the sacrificial layer has a stepped portion in which a portion corresponding to the support beam is a thick portion having a large thickness, and a portion corresponding to the movable portion is a thin portion having a small thickness. It is formed into a shape.

  According to the first aspect of the present invention, the second substrate is provided with the beam pressing portion that presses the support beam toward the first substrate. Therefore, in the initial state where the electrostatic force due to the drive electrode does not act, the movable portion is signaled. It can be pressed toward the electrode. For this reason, in the initial state, a narrow gap having a minimum interval dimension can be formed between the movable portion and the signal electrode. In the driving state in which the electrostatic force by the driving electrode is applied, the movable part is separated from the signal electrode by the electrostatic force by the driving electrode. For this reason, in the driving state, it is possible to form a wide gap with a wide interval dimension between the movable part and the signal electrode.

  Further, in the initial state, the movable portion can be urged toward the signal electrode by the beam pressing portion, and in the driving state, the movable portion can be urged away from the signal electrode by the electrostatic force. As a result, the displacement of the movable part can be suppressed when an external impact is applied in both the initial state and the driving state, and the maximum capacity value in the initial state and the minimum capacity value in the driving state are maintained. can do.

  According to the second aspect of the present invention, the movable portion is provided with the stopper protruding toward the first substrate. Therefore, when the movable portion is pressed toward the signal electrode by the beam pressing portion, the stopper is moved to the first electrode. By contacting the substrate, a narrow gap having a minimum distance can be formed between the movable portion and the signal electrode.

  According to the invention of claim 3, since the step of removing the sacrificial layer and forming a gap between the signal electrode and the movable portion is provided, the signal electrode and the movable portion are closest to each other depending on the thickness dimension of the sacrificial layer. The interval size of the narrow gap can be set. For this reason, since the thickness dimension of a sacrificial layer can be made small, the unevenness | corrugation of a movable part and a signal electrode can be made to correspond. Further, since the stress applied to the movable part by the sacrificial layer is weakened, the movable part is not greatly warped even after the sacrificial layer is removed. As a result, the gap dimension of the narrow gap when the signal electrode and the movable part are closest to each other can be set accurately, and the maximum capacity value can be set with high accuracy.

  In addition, since the method includes a step of attaching the second substrate to the support portion in a state where the beam pressing portion protruding from the second substrate is pressed against the support beam, in the initial state where the electrostatic force by the drive electrode does not act, the movable portion is signaled. It can be pressed toward the electrode. For this reason, in the initial state, a narrow gap having a minimum interval dimension can be formed between the movable portion and the signal electrode. In the driving state in which the electrostatic force by the driving electrode is applied, the movable part is separated from the signal electrode by the electrostatic force by the driving electrode. For this reason, in the driving state, it is possible to form a wide gap with a wide interval dimension between the movable part and the signal electrode.

  Further, in the initial state, the movable portion can be urged toward the signal electrode by the beam pressing portion, and in the driving state, the movable portion can be urged away from the signal electrode by the electrostatic force. As a result, the displacement of the movable part can be suppressed when an external impact is applied in both the initial state and the driving state, and the maximum capacity value in the initial state and the minimum capacity value in the driving state are maintained. can do.

  According to the invention of claim 4, the sacrificial layer is provided with a stopper forming hole which is located around the signal electrode and penetrates in the thickness direction. When the functional layer is formed, the sacrificial layer is formed from the movable portion by using the stopper forming hole. A stopper that protrudes toward the first substrate is formed. At this time, the protruding dimension of the stopper coincides with the thickness dimension of the sacrificial layer. For this reason, when the movable part is pressed against the signal electrode by the beam pressing part, the stopper comes into contact with the first substrate, and the same dimension as the thickness of the sacrificial layer is provided between the movable part and the signal electrode. A narrow gap can be formed.

  According to the invention of claim 5, the sacrificial layer has a stepped shape in which the portion corresponding to the support beam is a thick portion having a large thickness, and the portion corresponding to the movable portion is a thin portion having a small thickness. Forming. For this reason, the movable part formed in the thin part of the sacrificial layer has a large thickness, whereas the support beam formed in the thick part of the sacrificial layer has a small thickness. For this reason, since the spring constant of a support beam can be made small, a movable part can be easily displaced with a small electrostatic force.

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

  In the figure, the variable capacitance element 1 is formed by first and second substrates 2 and 3 and a functional layer 4 sandwiched between the substrates 2 and 3. Here, the substrates 2 and 3 are made of, for example, an insulating glass material or the like, and are formed in a square shape having a size of about several millimeters. And between the board | substrates 2 and 3, the space which accommodates the below-mentioned movable part 6 is defined.

  The substrates 2 and 3 and the functional layer 4 extend in the horizontal direction along, for example, the X axis and the Y axis, when the three axis directions orthogonal to each other are taken as the X axis, the Y axis, and the Z axis. Further, a plurality of recessed portions 3A are formed on the back surface side of the second substrate 3, and protrusions 3B and 3C protruding from the back surface toward the functional layer 4 are formed between the recessed portions 3A. Yes. At this time, the projecting portion 3B is disposed at a position facing a movable portion 6 described later, and the projecting portion 3C is disposed at a position facing an intermediate portion of a support beam 7 described later.

  On the other hand, the functional layer 4 is formed using a conductive metal material such as copper (Cu). The functional layer 4 is formed with a support portion 5, a movable portion 6, and a support beam 7 which will be described later.

  The support portion 5 is formed on the functional layer 4 and is fixed to the first and second substrates 2 and 3. The support portion 5 is formed in a rectangular frame shape that extends along the peripheral edges of the substrates 2 and 3, for example, and surrounds the movable portion 6, the support beam 7, and the like. Here, two beam connecting portions 5 </ b> A located on both sides in the X-axis direction with the movable portion 6 interposed therebetween are provided inside the support portion 5. The support portion 5 has a thickness of about several μm to several tens of μm (for example, 10 μm), and a space for accommodating the movable portion 6 between the substrates 2 and 3 together with a sealing frame 11 described later. keeping.

  The movable portion 6 is formed in the functional layer 4 and supported by the support portion 5 using a support beam 7 described later. The movable portion 6 is located on the center side of the substrates 2 and 3 and is disposed to face the protruding portion 3B of the substrate 3, and is movable in the thickness direction (Z-axis direction). Here, the movable portion 6 is formed in, for example, a rectangular flat plate shape and has a thickness dimension similar to that of the support portion 5. However, when the movable portion 6 is disposed at the same position as the support portion 5 with respect to the Z-axis direction, a narrow gap G 1 described later is formed between the movable portion 6 and the first substrate 2. For this reason, the thickness dimension of the movable part 6 is thinner than the support part 5 by the interval dimension (for example, about 0.1 to 0.2 μm) of the narrow gap G1.

  The movable portion 6 is displaced in the vertical direction (Z-axis direction) by an electrostatic force (electrostatic attractive force) generated between the movable electrode 6 and a drive electrode 10 described later, and approaches and separates from the first substrate 2. For this reason, the movable part 6 is held at a position close to the substrate 2 by a support beam 7 to be described later when no voltage is applied to the drive electrode 10.

  The movable portion 6 may be provided with a plurality of through holes penetrating in the thickness direction in order to reduce resistance due to surrounding gas.

  For example, four support beams 7 are provided between the movable part 6 and the support part 5 so as to support the movable part 6 so as to be movable in the vertical direction. These support beams 7 are formed, for example, as beams bent in a crank shape, are positioned between the substrates 2 and 3 and extend in the horizontal direction, and are spaced apart from these substrates 2 and 3 in the vertical direction (thickness direction). is doing.

  Each support beam 7 has a base end connected to the beam connecting portion 5 </ b> A of the support portion 5 and a distal end connected to the four corners of the movable portion 6. As shown in FIG. 4, the support beam 7 is bent and deformed in the vertical direction when the movable portion 6 is displaced toward the substrate 3.

  Furthermore, the support beam 7 has a smaller thickness dimension (for example, about several μm) than the support portion 5 and the movable portion 6. As a result, the support beam 7 can be easily deformed in the vertical direction.

  The intermediate receiving portion 8 is provided at an intermediate position in the X-axis direction of the support beam 7 and connects two support beams 7 separated in the Y-axis direction. And the intermediate | middle receiving part 8 is formed in the substantially rectangular flat plate shape, for example, and contacts the beam pressing part 12 mentioned later. Accordingly, the intermediate receiving portion 8 is pressed toward the first substrate 2 by the beam pressing portion 12.

  For example, two signal electrodes 9 are provided on the surface side of the first substrate 2 at a position facing the movable portion 6. As shown in FIGS. 1 and 2, these signal electrodes 9 are formed of, for example, a conductive metal thin film. The two signal electrodes 9 are arranged side by side along the X-axis direction and are separated from each other. Further, these signal electrodes 9 face the movable portion 6 over almost the entire surface, and are connected to a signal extraction electrode 15 described later. For example, a high frequency signal of about several hundred kHz to several tens GHz is input to the signal electrode 9.

  In this case, the movable part 6 is provided between the signal electrode 9 on the left side (one side in the X-axis direction) and the movable part 6 and between the signal electrode 9 on the right side (the other side in the X-axis direction) and the movable part 6. Thus, two capacitors (air gap capacitors) connected in series are formed. The overall capacitance of these capacitors, that is, the capacitance between the left and right signal electrodes 9, changes according to the distance (distance dimension) between the signal electrodes 9 and the movable portion 6. ing.

  For example, two drive electrodes 10 are provided on the back side of the second substrate 3 at a position facing the movable portion 6. These drive electrodes 10 are formed of, for example, a conductive metal thin film, face the movable portion 6 over almost the entire surface, and are disposed on both sides in the X-axis direction with the protruding portion 3B interposed therebetween. Here, the two drive electrodes 10 are electrically connected to each other using the connecting portion 10 </ b> A and are connected to a drive extraction electrode 17 described later.

  The drive electrode 10 is opposed to the movable portion 6 with a gap in the vertical direction (Z-axis direction). Then, by applying a voltage between the drive electrode 10 and the movable part 6, a vertical electrostatic force (electrostatic attractive force) that attracts the movable part 6 toward the substrate 3 is generated. Thus, the movable part 6 is driven in a direction away from the substrate 2.

  That is, in an initial state where no voltage is applied between the drive electrode 10 and the movable part 6, the movable part 6 is held at a position close to the substrate 2 by the support beam 7, and between the movable part 6 and the signal electrode 9. Is formed with a narrow gap G1 having a small interval dimension.

  On the other hand, in a driving state in which a voltage is applied between the drive electrode 10 and the movable part 6, the movable part 6 is attracted to the drive electrode 10 by an electrostatic force acting between them. As a result, as shown in FIG. 4, the movable portion 6 is displaced in the vertical direction to a position where it comes into contact with a stopper 14 described later, and is held at a position separated from the substrate 2. At this time, a wide gap G2 having a large distance is formed between the movable portion 6 and the signal electrode 9.

  The variable capacitance element 1 has a capacitance value between the signal electrode 9 and the movable portion 6 by changing the distance between the signal electrode 9 and the movable portion 6 according to the position of the movable portion 6. It is selectively switched.

  The sealing frame 11 is disposed between the functional layer 4 and the second substrate 3, and is formed in a substantially rectangular frame shape along the outer peripheral edge of the second substrate 3. Here, the sealing frame 11 is formed using a conductive metal material such as an alloy containing gold (Au) or gold, for example, and is bonded to the substrate 3 and the support portion 5, respectively. Thereby, the sealing frame 11 defines an accommodating space for accommodating the movable portion 6 between the first and second substrates 2 and 3 and seals the accommodating space in an airtight state.

  The sealing frame 11 joins the substrate side sealing portion 11A made of a metal film provided on the back surface of the substrate 3 and the functional layer side sealing portion 11B made of a metal film provided on the surface of the functional layer 4. It is formed by. The thickness dimension of the sealing frame 11 is set to a value larger than that of the drive electrode 10. Further, the sealing frame 11 is joined to the recessed portion 3 </ b> A located on the outer peripheral side of the substrate 3. Thereby, even when the sealing frame 11 is sandwiched between the substrate 3 and the support portion 5, a gap is formed between the movable portion 6 and the drive electrode 10.

  The beam pressing portion 12 is disposed on the back surface side of the second substrate 3 and is provided on each of the two protruding portions 3C that are separated in the X-axis direction. These beam pressing portions 12 are formed of, for example, a conductive metal material similar to that of the sealing frame 11 and protrude toward the functional layer 4. Here, the beam pressing portion 12 is disposed at a position facing the intermediate receiving portion 8 of the functional layer 4.

  The beam pressing portion 12 includes a substrate side beam pressing portion 12A made of a metal film provided on the back surface of the substrate 3 and a functional layer side beam pressing portion 12B made of a metal film provided on the surface of the functional layer 4. ing. The beam pressing portion 12 has a thickness dimension (projection dimension) comparable to that of the sealing frame 11. For this reason, the beam pressing portion 12 protrudes toward the functional layer 4 from the sealing frame 11 by the protruding dimension of the protruding portion 3C. That is, the tip of the beam pressing portion 12 is disposed at a position closer to the first substrate 2 than the joint surface between the support portion 5 and the sealing frame 11. As a result, the beam pressing unit 12 presses the support beam 7 toward the first substrate 2.

  A plurality of first stoppers 13 are provided around the two signal electrodes 9 on the back side of the movable portion 6. These stoppers 13 have a protrusion shape with a small area at the front end surface, are formed using the same conductive metal material as the movable portion 6, and protrude from the movable portion 6 toward the first substrate 2. Here, the protruding dimension of the stopper 13 is set to be approximately the same as the thickness dimension of the thin portion 22B of the sacrificial layer 22 described later. Thereby, in the initial state in which the stopper 13 is in contact with the substrate 2, a narrow gap having a small space dimension of 1 μm or less (for example, 0.1 to 0.2 μm) is provided between the signal electrode 9 and the movable portion 6. G1 is formed.

  On the other hand, a plurality of second stoppers 14 are provided between the two drive electrodes 10 on the back surface side of the second substrate 3. These stoppers 14 also have projections with a small area as in the stopper 13, and are formed using, for example, a conductive metal material similar to that of the sealing frame 11 and project toward the movable portion 6. .

  Here, the stopper 14 is provided on the protrusion 3 </ b> B of the substrate 3 while being insulated from the drive electrode 10. Further, the protruding dimension of the stopper 14 is set to, for example, substantially the same value as the thickness dimension of the drive electrode 10. For this reason, the stopper 14 protrudes toward the movable part 6 rather than the drive electrode 10 by the protrusion dimension of the protrusion part 3B. Thereby, the stopper 14 prevents the movable part 6 from being short-circuited to the drive electrode 10 by contacting the movable part 6 before the drive electrode 10 when the movable part 6 is displaced toward the substrate 3. Yes.

  Furthermore, the protruding dimension of the stopper 14 is set to a value smaller than the protruding dimension of the beam pressing portion 12. For this reason, in the initial state where the movable part 6 is located on the substrate 2 side, the beam pressing part 12 contacts the intermediate receiving part 8, whereas a gap is formed between the stopper 14 and the movable part 6. Is.

  In an initial state where no voltage is applied between the movable portion 6 and the drive electrode 10, the stopper 13 contacts the substrate 2, and the stopper 14 is separated from the movable portion 6. At this time, the stopper 13 maintains an interval of a predetermined dimension therebetween so that the movable portion 6 and the signal electrode 9 do not come into contact with each other.

  On the other hand, in a driving state in which a voltage is applied between the movable portion 6 and the drive electrode 10, the stopper 13 is separated from the substrate 2, and the stopper 14 is in contact with the movable portion 6. At this time, the stopper 14 maintains an interval of a predetermined dimension therebetween so that the movable portion 6 and the drive electrode 10 do not come into contact with each other.

  The signal extraction electrode 15 is provided on the first substrate 2 and connected to the signal electrode 9. Here, the signal extraction electrode 15 is disposed at a position corresponding to the movable portion 6 and is electrically connected to the signal electrode 9.

  These signal extraction electrodes 15 are formed by, for example, using a laser processing or microblasting method to form a through hole penetrating in the thickness direction in the substrate 2 and conducting metal such as copper (Cu) in the through hole. It is formed by filling the material. The two signal electrodes 9 are connected to an external circuit or the like via the signal extraction electrode 15.

  The drive lead electrodes 16 and 17 are provided on the second substrate 3 and connected to the movable portion 6 and the drive electrode 10, respectively. Here, the drive extraction electrode 16 is disposed at a position corresponding to the support portion 5 and is electrically connected to the movable portion 6 through the support beam 7 and the like. On the other hand, the drive lead electrode 17 is disposed at a position corresponding to the movable portion 6 and is electrically connected to the drive electrode 10.

  Similar to the signal extraction electrode 15, these drive extraction electrodes 16 and 17 are formed by filling a through hole with a conductive metal material. The drive lead electrodes 16 and 17 connect the movable portion 6 and the drive electrode 10 to a DC power source 18 as shown in FIG. Thereby, the power source 18 applies a DC voltage of about 3 V, for example, between the movable portion 6 and the drive electrode 10 and generates an electrostatic attractive force therebetween.

  Next, a method for manufacturing the variable capacitance element 1 will be described with reference to FIGS.

  First, in the first substrate forming step shown in FIG. 5, an insulating glass substrate 21 to be the first substrate 2 of the variable capacitance element 1 is prepared, and for example, sputtering, vapor deposition or the like is applied to the glass substrate 21. Is used to form a conductive metal thin film such as gold. Thereby, the signal electrode 9 is formed on the surface of the glass substrate 21 at a position corresponding to the movable portion 6.

  In addition, a through hole is formed in the glass substrate 21 by using laser processing, a microblast method, or the like, and then a conductive metal material such as copper is filled in the through hole by, for example, plating. Thus, the signal extraction electrode 15 connected to the signal electrode 9 is formed on the glass substrate 21. Through the above steps, the first substrate 2 including the signal electrode 9 and the like is formed.

  The through hole of the signal extraction electrode 15 is formed by using laser processing, a microblast method, or the like. However, the present invention is not limited to this, and for example, the glass substrate 21 may be formed using a photosensitive glass material, and a through hole may be formed by irradiating the photosensitive glass material with ultraviolet rays or the like.

Next, in the sacrificial layer forming step shown in FIG. 6, a sacrificial layer 22 made of, for example, titanium (Ti), silicon oxide (SiO ₂ ) or the like is formed on the surface of the substrate 2 at a position corresponding to the movable portion 6 and the support beam 7. Form. At this time, the sacrificial layer 22 has a stepped shape in which a portion corresponding to the support beam 7 becomes a thick portion 22A having a large thickness and a portion corresponding to the movable portion 6 becomes a thin portion 22B having a small thickness. Is formed. For this reason, the thick portion 22A has a thickness dimension of about several μm (for example, 1 to 2 μm), and the thin portion 22B has a thickness dimension of about 1 μm or less (for example, 0.1 to 0.2 μm). Yes.

  At this time, the sacrificial layer 22 is formed by, for example, forming a first layer having the same thickness as the thin portion 22B and then laminating the second layer on a portion corresponding to the support beam 7. The thin portion 22B covers the signal electrode 9 over the entire surface. Further, a plurality of stopper formation holes 23 are formed in the sacrificial layer 22 so as to be located around the signal electrode 9 and penetrate in the thickness direction.

  Next, in the seed layer forming step, the seed layer 24 is formed on the entire surface of the substrate 2 so as to cover the sacrificial layer 22 using, for example, the same conductive metal material (for example, copper) as the movable portion 6 or the like. At this time, the seed layer 24 is formed by a thin metal thin film having a thickness of, for example, 0.1 μm or less, and serves as a base portion for performing the plating process.

  Next, in the plating mold forming step shown in FIG. 7, the mold 25 is formed on the surface of the seed layer 24 excluding the support portion 5, the movable portion 6, the support beam 7, and the like. At this time, the mold 25 is formed by applying a predetermined patterning after applying a mold material (for example, a photoresist material) that inhibits the growth of plating. The mold 25 has a thickness dimension (for example, 15 to 30 μm) larger than the thickness dimension (for example, 10 μm) of the support portion 5 or the like.

  Next, in the plating process shown in FIG. 8, the surface of the seed layer 24 is plated to grow a plated layer 26 made of a conductive metal material such as copper. When the plated layer 26 grows beyond the thickness dimension of the support portion 5 and the like, the plating process is terminated and the mold 25 is removed. Thereafter, the surface of the plating layer 26 is polished in a flat state by using, for example, a CMP (Chemical Mechanical Polishing) method. Thereby, the functional layer 4 provided with the support part 5, the movable part 6, the support beam 7, etc. is formed (refer FIG. 9). At this time, a plurality of stoppers 13 protruding into the stopper forming hole 23 are formed on the back surface of the movable portion 6.

  Next, in the functional layer side sealing portion forming step shown in FIG. 9, a metal thin film such as gold (Au) is formed on the surface of the support portion 5 by using, for example, vapor deposition or sputtering, and the functional layer side sealing is performed. A stop 11B is formed. At the same time, the functional layer side beam pressing portion 12B is formed on the surface of the intermediate receiving portion 8 of the support beam 7 by using the same material as that of the functional layer side sealing portion 11B.

  In order to improve the adhesion between the metal thin film made of gold or the like and the functional layer 4 made of copper, which forms the functional layer side sealing portion 11B and the functional layer side beam pressing portion 12B, for example, chromium ( A bonding layer such as Cr) or platinum (Pr) is provided.

  Next, in the sacrificial layer removal step shown in FIG. 10, for example, after removing the sacrificial layer 22 by etching using thin hydrofluoric acid or the like, the tip portion of the stopper 13 or the like of the seed layer 24 is removed using thin sulfuric acid. Remove. As a result, the movable portion 6 is released from the substrate 2 and can be displaced in the thickness direction.

  On the other hand, in the second substrate forming step shown in FIG. 11, an insulating glass substrate 27 to be the second substrate 3 of the variable capacitance element 1 is prepared, and etching processing is performed on a predetermined portion of the back surface of the glass substrate 27. By applying, a recessed portion 3A (cavity) and projecting portions 3B and 3C are formed. Next, a conductive metal thin film such as gold is formed on the glass substrate 27 by using, for example, sputtering or vapor deposition.

  Thereby, on the back surface of the glass substrate 27, the drive electrode 10 is formed at a position corresponding to the movable portion 6 in the recessed portion 3A, and the substrate side sealing portion is positioned at a position corresponding to the support portion 5 in the recessed portion 3A. 11A is formed. Together with these, on the back surface of the glass substrate 27, the stopper 14 is formed on the protruding portion 3B, and the substrate-side beam pressing portion 12A is formed on the protruding portion 3B. At this time, the drive electrode 10, the substrate side sealing portion 11A, the substrate side beam pressing portion 12A, and the stopper 14 are electrically insulated from each other.

  Furthermore, after a through hole penetrating in the thickness direction is formed in the glass substrate 27, the through hole is filled with a conductive metal material such as copper. Thus, the driving lead electrodes 16 and 17 connected to the substrate side sealing portion 11A and the driving electrode 10 are formed on the glass substrate 27, respectively. Through the above steps, the second substrate 3 including the drive electrode 10 and the like is formed.

  Next, in the sealing frame joining step shown in FIG. 12, the substrate-side sealing portion 11A of the second substrate 3 and the functional layer-side sealing portion 11B of the functional layer 4 are thermocompression bonded. Specifically, while heating the sealing portions 11A and 11B at a predetermined temperature in a range from room temperature to 400 ° C., a predetermined load (for example, on a 4-inch wafer) is applied so that the sealing portions 11A and 11B are in close contact with each other. Load about 4t). Thereby, the sealing portions 11A and 11B are pressure-bonded to each other, and the second substrate 3 and the functional layer 4 are bonded and fixed to each other. As a result, the space in which the movable part 6 is accommodated is surrounded by the first and second substrates 2 and 3, the sealing frame 11, and the like, and is sealed in a sealed state.

  At this time, the substrate side beam pressing portion 12 </ b> A comes into contact with the functional layer side beam pressing portion 12 </ b> B and presses the intermediate receiving portion 8 provided at an intermediate position of the support beam 7 toward the first substrate 2. As a result, the movable portion 6 is disposed at a position covering the signal electrode 9 of the substrate 2, and the stopper 13 contacts the substrate 2. Thereby, in the initial state, a narrow gap G1 having a distance dimension corresponding to the thickness dimension of the thin part 22B of the sacrificial layer 22 is formed between the signal electrode 9 and the movable part 6.

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

  First, in an initial state in which no voltage is applied between the movable portion 6 and the drive electrode 10, as shown in FIG. 1, the movable portion 6 is held at a position close to the signal electrode 9, and the movable portion 6 and the signal The capacitance between the electrode 9 and the electrode 9 has a maximum capacitance value corresponding to the interval size of the narrow gap G1 between the movable portion 6 and the signal electrode 9.

  Further, as shown in FIG. 4, in a driving state in which a voltage is applied between the movable portion 6 and the driving electrode 10, an electrostatic force is generated between them. At this time, the movable portion 6 is displaced in the vertical direction to a position where it comes into contact with the stopper 14 while bending and deforming the support beam 7, and the movable portion 6 is held at a position separated from the signal electrode 9. As a result, the electrostatic capacitance between the movable portion 6 and the signal electrode 9 becomes a minimum capacitance value corresponding to the gap dimension of the wide gap G2 between the movable portion 6 and the signal electrode 9 that are separated from each other.

  Thereby, the variable capacitance element 1 switches the electrostatic capacitance between the movable part 6 and the signal electrode 9 according to the presence or absence of voltage application. For this reason, the variable capacitance element 1 functions as a switch element that switches transmission / reception of a high-frequency signal between the two signal electrodes 9 according to the capacitance.

  Thus, according to the present embodiment, since the beam pressing portion 12 that presses the support beam 7 toward the first substrate 2 is provided on the second substrate 3, the initial state in which the electrostatic force by the drive electrode 10 does not act. Then, the movable part 6 can be pressed toward the signal electrode 9. Therefore, in the initial state, it is possible to form a narrow gap G1 having a minimum distance dimension between the movable portion 6 and the signal electrode 9. In the driving state in which the electrostatic force by the driving electrode 10 acts, the movable part 6 is separated from the signal electrode 9 by the electrostatic force by the driving electrode 10. For this reason, in the driving state, a wide gap G2 having a wide interval dimension can be formed between the movable portion 6 and the signal electrode 9.

  In the initial state, the beam pressing portion 12 urges the movable portion 6 in a direction approaching the signal electrode 9, and in the driving state, the movable portion 6 is urged away from the signal electrode 9 by electrostatic force. As a result, the displacement of the movable portion 6 can be suppressed when an impact is applied from the outside in both the initial state and the driving state, and the maximum capacity value in the initial state and the minimum capacity value in the driving state are maintained. be able to.

  Further, since the movable portion 6 is provided with the stopper 13 protruding toward the first substrate 2, when the movable portion 6 is pressed toward the signal electrode 9 by the beam pressing portion 12, the stopper 13 is moved to the first portion. A narrow gap G1 having a minimum distance dimension can be formed between the movable portion 6 and the signal electrode 9 by contacting the substrate 2 with the substrate 2.

  In particular, in the present embodiment, in the sacrificial layer removing step, the sacrificial layer 22 is removed to form a gap between the signal electrode 9 and the movable portion 6, and therefore, depending on the thickness dimension of the sacrificial layer 22 (thin wall portion 22B). The interval dimension of the narrow gap G1 when the signal electrode 9 and the movable part 6 are closest to each other can be set. For this reason, since the thickness dimension of the sacrificial layer 22 can be reduced to 1 μm or less (for example, about 0.1 to 0.2 μm), the concavities and convexities are made to coincide on the opposed surfaces of the movable portion 6 and the signal electrode 9. Can do. Further, by forming the sacrificial layer 22 thin, the stress applied to the movable part 6 by the sacrificial layer 22 is weakened, so that the movable part 6 is not greatly warped even after the sacrificial layer 22 is removed. As a result, the distance dimension of the narrow gap G1 when the signal electrode 9 and the movable part 6 are closest to each other can be set accurately, and the maximum capacity value can be set with high accuracy.

  In the sealing frame joining step, the second substrate 3 is attached to the support portion 5 while the beam pressing portion 12 protruding from the second substrate 3 is pressed against the support beam 7. A narrow gap G 1 can be formed between the movable portion 6 and the signal electrode 9 by pressing toward the signal electrode 9. Further, in the driving state, the movable portion 6 is separated from the signal electrode 10 by the electrostatic force generated by the driving electrode 10, so that a wide gap G 2 can be formed between the movable portion 6 and the signal electrode 10.

  Further, the sacrificial layer 22 is provided with a stopper forming hole 23 which is located around the signal electrode 9 and penetrates in the thickness direction. When the functional layer 4 is formed, the first portion is moved from the movable portion 6 using the stopper forming hole 23. The stopper 13 protruding toward the substrate 2 is formed. At this time, the protruding dimension of the stopper 13 matches the thickness dimension of the sacrificial layer 22. For this reason, when the movable portion 6 is pressed against the signal electrode 9 by the beam pressing portion 12, the stopper 13 comes into contact with the first substrate 2 and the sacrificial layer 22 is formed between the movable portion 6 and the signal electrode 9. A narrow gap G1 having the same spacing as the thickness can be formed.

  Further, the sacrificial layer 22 is formed in a stepped shape in which a portion corresponding to the support beam 7 is a thick portion 22A having a large thickness and a portion corresponding to the movable portion 6 is a thin portion 22B having a small thickness. . For this reason, when the functional layer 4 is formed so as to cover the sacrificial layer 22, the movable portion 6 formed in the thin portion 22 </ b> B of the sacrificial layer 22 has a large thickness, whereas the thick portion of the sacrificial layer 22. The thickness of the support beam 7 formed on 22A is reduced. For this reason, since the spring constant of the support beam 7 can be made small, the movable part 6 can be easily displaced by a small electrostatic force.

  In the above embodiment, the beam pressing portion 12 is provided separately from the second substrate 3. However, if the second substrate 3 can be processed with high accuracy, the second substrate 3 is used. 3 may be formed integrally.

  In the above embodiment, the stopper 14 is provided separately from the second substrate 3, but may be formed integrally with the second substrate 3. The stopper 14 is formed using a conductive metal material as in the case of the sealing frame 11 or the like, but may be formed using an insulating material. In this case, the stopper made of an insulating material may be disposed between the drive electrode and the movable part.

  In the above embodiment, two signal electrodes 9 are provided. However, only one signal electrode 9 may be provided. In this case, a high-frequency signal is input to the movable portion 6, and transmission / reception of the high-frequency signal is switched between the movable portion 6 and the signal electrode 9.

  In the embodiment, the protrusions 3B and 3C are formed on the back surface of the second substrate 3 so that the stopper 14 protrudes from the drive electrode 10 toward the first substrate 2 and the beam pressing portion 12 is provided. The first substrate 2 is protruded from the sealing frame 11 to the first substrate 2 side. However, the present invention is not limited to this, and the back surface of the second substrate 3 is formed flat, and the projecting dimensions (thickness dimensions) of the drive electrode 10, the sealing frame 11, the beam pressing portion 12, and the stopper 14 are set. By appropriately making the difference, the stopper 14 may protrude from the drive electrode 10 toward the first substrate 2, and the beam pressing portion 12 may protrude from the sealing frame 11 toward the first substrate 2.

  Further, in the above-described embodiment, the signal electrode 9 is provided on the first substrate 2 and the drive electrode 10 is provided on the second substrate 3 so that an electrostatic attractive force acts between the drive electrode 10 and the movable portion 6. The configuration. However, the present invention is not limited to this. For example, both the signal electrode and the drive electrode may be provided on the first substrate, and an electrostatic repulsive force (repulsive force) may be applied between the drive electrode and the movable portion. .

It is a longitudinal cross-sectional view which shows the variable capacitance element by embodiment of this invention. It is sectional drawing which looked at the 1st board | substrate and the functional layer from the arrow II-II direction in FIG. It is sectional drawing which looked at the 2nd board | substrate etc. from the arrow III-III direction in FIG. It is a longitudinal cross-sectional view similar to FIG. 1 which shows the state which the movable part displaced by the electrostatic force. It is a longitudinal cross-sectional view which shows the state which formed the signal electrode etc. in the glass substrate by the 1st board | substrate formation process. It is a longitudinal cross-sectional view which shows the state which formed the sacrificial layer etc. in the 1st board | substrate by the sacrificial layer formation process. It is a longitudinal cross-sectional view which shows the state which formed the mold on the surface of the seed layer by the plating mold formation process. It is a longitudinal cross-sectional view which shows the state which covered the sacrificial layer by the plating process process, and formed the functional layer provided with the support part, the movable part, the support beam. It is a longitudinal cross-sectional view which shows the state which formed the functional layer side sealing part and the functional layer side beam pressing part in the surface of the functional layer by the functional layer side sealing part formation process. It is a longitudinal cross-sectional view which shows the state which removed the sacrificial layer by the sacrificial layer removal process. It is a longitudinal cross-sectional view which shows the state which formed the drive electrode, the board | substrate side sealing part, the board | substrate side beam pressing part, the stopper, etc. in the glass substrate by the 2nd board | substrate formation process. It is a longitudinal cross-sectional view which shows the state which crimp-bonds the board | substrate side sealing part of a 2nd board | substrate, and the function side sealing part of a functional layer by a sealing frame joining process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Variable capacitance element 2 1st board | substrate 3 2nd board | substrate 4 Functional layer 5 Support part 6 Movable part 7 Support beam 8 Intermediate receiving part 9 Signal electrode 10 Drive electrode 11 Sealing frame 12 Beam pressing part 13 1st stopper 14 2nd stopper 22 Sacrificial layer 22A Thick part 22B Thin part 23 Stopper formation hole

Claims (5)

A support portion sandwiched between first and second substrates;
A movable part supported by the support part so as to be displaceable in the thickness direction using a support beam;
A signal electrode provided on the first substrate at a position facing the movable portion, and a capacitance of the movable electrode changing when the movable portion approaches and separates;
A driving electrode provided on one of the first and second substrates at a position facing the movable portion, and driving the movable portion in a direction approaching or separating from the signal electrode using electrostatic force; In the variable capacitance element provided,
The second substrate is provided with a beam pressing portion that presses the support beam toward the first substrate,
In an initial state where the electrostatic force due to the drive electrode does not act, a narrow gap having a minimum distance dimension is formed between the movable part and the signal electrode,
A variable capacitance element having a configuration in which a wide gap having a wide gap is formed between the movable portion and the signal electrode in a driving state in which an electrostatic force is applied by the driving electrode.   The variable capacitance element according to claim 1, wherein the movable portion is provided with a stopper protruding toward the first substrate. A support portion sandwiched between the first and second substrates, a movable portion supported by the support portion so as to be displaceable in the thickness direction using a support beam, and the first portion at a position facing the movable portion; A signal electrode provided on a substrate, the capacitance of which changes between the movable portion when the movable portion approaches and separates, and the first and second substrates at a position facing the movable portion. A method of manufacturing a variable capacitance element, comprising: a drive electrode that is provided on either side and drives the movable portion in a direction approaching or separating from the signal electrode using electrostatic force,
Forming the signal electrode on the first substrate;
Forming a sacrificial layer over the signal electrode;
Forming a functional layer that covers the sacrificial layer and includes the movable portion, the support beam, and the support portion;
Removing the sacrificial layer to form a gap between the signal electrode and the movable part;
And a step of attaching the second substrate to the support portion in a state in which the beam pressing portion protruding from the second substrate is pressed against the support beam. The sacrificial layer is provided with a stopper forming hole that is located around the signal electrode and penetrates in the thickness direction,
4. The method of manufacturing a variable capacitance element according to claim 3, wherein when the functional layer is formed, a stopper protruding from the movable portion toward the first substrate is formed using the stopper forming hole.   The sacrificial layer is formed in a stepped shape in which a portion corresponding to the support beam is a thick portion having a large thickness and a portion corresponding to the movable portion is a thin portion having a small thickness. Item 5. A method for manufacturing a variable capacitor according to Item 3 or 4.

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