JP2006179674A - Variable capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable capacitor having a large capacitance change due to an applied voltage, a high Q value, and good temperature characteristics.
A first variable capacitive element and a first capacitive element connected in series, and a second variable capacitive element and a second capacitive element connected in series are included in the first variable capacitive element. The outer side and the outer side of the second capacitive element are connected at the first connection point, and the outer side of the second variable capacitive element and the outer side of the first capacitive element are connected at the second connection point, and are connected in parallel. A third capacitive element is connected between the first variable capacitive element and the first capacitive element and between the second variable capacitive element and the second capacitive element. A fourth capacitor element is connected between the third capacitor element and the fourth capacitor element, and the first and second connection points are connected to the terminals. A variable capacitor characterized by being connected.
[Selection] Figure 1

Description

  The present invention relates to a variable capacitor whose capacitance changes when a DC voltage is applied, and more particularly, to a variable capacitor having a large capacitance change due to an applied voltage, a high Q value, and good temperature characteristics.

  Among conventional capacitors, there is a thin film capacitor in which upper and lower electrode layers and dielectric layers are formed as thin films. This is usually constituted by laminating a thin film-like lower electrode layer, dielectric layer and upper electrode layer in this order on an electrically insulating support substrate.

  In such a thin film capacitor, the lower electrode layer and the upper electrode layer are formed by a sputtering method, a vacuum deposition method, or the like, respectively, and the dielectric layer is also formed by a sputtering method, a sol-gel method, or the like. Also, for the production of such a thin film capacitor, a photolithography technique is usually used as follows.

  First, after forming a conductor layer as a lower electrode layer on the entire surface of the insulating support substrate, cover only necessary portions with a photoresist, and then remove unnecessary portions by wet etching or dry etching to form a lower portion of a predetermined shape. An electrode layer is formed. Next, a dielectric layer to be a thin film dielectric layer is formed on the entire surface of the support substrate, and unnecessary portions are removed to form a thin film dielectric layer having a predetermined shape in the same manner as the lower electrode layer. Finally, a conductor layer to be an upper electrode layer is formed on the entire surface, and unnecessary portions are removed to form an upper electrode layer having a predetermined shape. Moreover, surface mounting becomes possible by forming a protective layer and a solder terminal part.

In addition, as a material of the thin film dielectric layer, a dielectric material made of (Ba _x Sr _1-x ) Ti _y O ₃ is used, and a predetermined potential is applied between the upper electrode layer and the lower electrode layer, so that the thin film dielectric A variable capacitor that changes the capacitance by changing the dielectric constant of the body layer has the same structure. For example, Patent Document 1 discloses a variable capacitor whose capacitance is changed by applying a DC bias voltage to a thin film dielectric layer.

In addition, as another conventional variable capacitor, there are four electrodes, that is, two capacitance extraction electrodes and two voltage application electrodes, and at least one of them is composed of a plurality of linear electrodes. Patent Document 2 discloses a capacitor that can change the capacitance between two capacitance extraction electrodes by applying a voltage to the two voltage application electrodes.
Japanese Patent Laid-Open No. 11-260667 Japanese Unexamined Patent Publication No. 7-335490

  In the conventional variable capacitor as disclosed in Patent Document 1, the basic characteristics of the variable capacitor are almost determined by the characteristics of the thin film dielectric layer to be used. In order to provide a variable capacitor having a high temperature characteristic and a good temperature characteristic, it is necessary to prepare a thin film dielectric layer having a large change in dielectric constant due to an applied voltage, a high Q value, and a good temperature characteristic.

  However, in general, in a thin film dielectric layer, if the change in the dielectric constant due to the applied voltage is large, the Q value is lowered or the temperature characteristic is deteriorated. If the temperature characteristic is good, the dielectric constant depending on the applied voltage is obtained. There is a problem that the change becomes small or the Q value becomes low.

  Further, in the variable capacitor as shown in Patent Document 2, since it is necessary to change the capacitance control voltage in the same phase as the voltage of the signal applied to the capacitor, a DC voltage is used as the capacitance control voltage. In this case, the capacitance can be changed only with respect to the DC voltage, and the capacitance varies periodically with respect to the AC voltage, so that there is a problem that it does not function as a variable capacitor.

  The present invention has been devised in view of the above-described problems in the prior art, and the object thereof is to realize a large capacitance change due to an applied voltage, which can be realized without using a thin film dielectric layer, and a Q value. It is to provide a variable capacitor having a high temperature characteristic and good temperature characteristics.

  The variable capacitor of the present invention includes 1) a first variable capacitor and a first capacitor connected in series, and a second variable capacitor and a second capacitor connected in series, The outside of the first variable capacitor and the outside of the second capacitor are connected at a first connection point, and the outside of the second variable capacitor and the outside of the first capacitor are connected at a second connection point. Connected in parallel, and a third capacitive element is provided between the first variable capacitive element and the first capacitive element and between the second variable capacitive element and the second capacitive element. A fourth capacitance element is connected between the first connection point and the second connection point, and the third capacitance element and the fourth capacitance element are electrostatically coupled to each other. And terminals are connected to the first connection point and the second connection point, respectively. And it is characterized in and.

  The variable capacitor of the present invention is characterized in that 2) in the configuration of 1), the first and second variable capacitors are dielectric thin-film capacitors whose capacitance changes according to the applied voltage. To do.

  The variable capacitor according to the present invention is characterized in that, 3) in the configuration of 1), the first and second variable capacitors are varactor diodes whose capacitance changes according to the applied voltage. It is.

  In addition, the variable capacitor according to the present invention is characterized in that, 4) in any one of the above 1) to 3), a resistor or an inductor is connected in parallel to each of the first and second capacitive elements. To do.

  In the variable capacitor of the present invention, 5) in any one of the above 1) to 4), the third and fourth capacitive elements have a lower electrode, a dielectric, and an upper electrode. The lower electrodes and the upper electrodes are adjacent to each other.

  In the variable capacitor of the present invention, 6) in any one of the above 1) to 4), the third capacitor element includes a dielectric substrate and two adjacent ones formed on the dielectric substrate. And the fourth capacitor element includes a dielectric layer formed on the third capacitor element and two adjacent electrodes formed on the dielectric layer. Is.

  In the variable capacitor of the present invention, 7) in any one of the above 1) to 4), the third and fourth capacitive elements are formed on a dielectric substrate and the dielectric substrate. It consists of four adjacent electrodes.

  The variable capacitor according to the present invention is characterized in that 8) In any one of 5) to 7) above, the electrodes of the third and fourth capacitors are comb-shaped electrodes. It is.

  According to the variable capacitor of the present invention, 1) a first variable capacitor and a first capacitor connected in series, and a second variable capacitor and a second capacitor connected in series are provided. The outside of the first variable capacitor and the outside of the second capacitor are connected at the first connection point, and the outside of the second variable capacitor and the outside of the first capacitor are connected at the second connection point. Are connected in parallel, and a third capacitor element is connected between the first variable capacitor element and the first capacitor element and between the second variable capacitor element and the second capacitor element. The fourth capacitor element is connected between the point and the second connection point, and the third capacitor element and the fourth capacitor element are electrostatically coupled to each other. 2 are respectively connected to the connection points, the first variable capacitance element, the first capacitance element, Variable capacitor, the second capacitor and the third capacitor forms a bridge circuit. Thus, by changing the capacitances of the first variable capacitance element and the second variable capacitance element, the voltage applied to the third capacitance element can be set to an arbitrary value including 0V. Here, since the third capacitive element and the fourth capacitive element are electrostatically coupled, an electrostatic charge is applied on the electrode of the fourth capacitive element in addition to the charge corresponding to the applied AC voltage. A charge corresponding to the charge of the third capacitor element is generated by the electric induction, and similarly, a fourth capacitor is formed on the electrode of the third capacitor element by the electrostatic induction in addition to the charge corresponding to the applied AC voltage. A charge corresponding to the charge of the element is generated. Due to the charge due to electrostatic induction, both the third capacitive element and the fourth capacitive element have an apparent capacitance that is larger than the capacitance determined by the shape and the dielectric constant of the dielectric. As described above, since the AC voltage applied to the third capacitive element can be changed by changing the capacitance of the variable capacitive element that forms the bridge, the fourth capacitive element can be changed by electrostatic induction. The generated charge changes, and the apparent capacitance of the fourth capacitive element changes. As a result, the variable capacitor can change the overall capacitance.

  According to the variable capacitor of the present invention, 2) when the first and second variable capacitors are dielectric thin film capacitors whose capacitance changes according to the applied voltage, the first to fourth capacitors are configured. It is not necessary to use a dielectric whose dielectric constant changes depending on the applied voltage, and a dielectric material having a high Q value can be used. The overall capacitance change also depends on the degree of coupling between the third capacitive element and the fourth capacitive element that are electrostatically coupled and the capacitance ratio, together with the capacitance change of the dielectric thin film capacitor as the variable capacitance element. Therefore, if the temperature characteristics of the dielectric thin film capacitor are good, it is possible to obtain a variable capacitor having a large capacitance change due to the applied voltage, a high Q value, and a good temperature characteristic.

  According to the variable capacitor of the present invention, 3) when the first and second variable capacitors are varactor diodes whose capacitance changes according to the applied voltage, the varactor diode has a large capacitance change due to the applied voltage, Although the temperature characteristic is good, the Q value is low. On the other hand, the first to fourth capacitive elements do not need to use a dielectric whose dielectric constant changes depending on the applied voltage as described above. Since a dielectric material with a high Q value can be used, the capacitance change due to the applied voltage is large and the temperature characteristics are also good by adjusting the capacitance ratio of the third capacitive element, the fourth capacitive element, and the varactor diode. Thus, a variable capacitor having a higher Q value can be obtained.

  According to the variable capacitor of the present invention, 4) when a resistor or an inductor is connected in parallel to each of the first and second capacitors, the impedance of the resistor or the inductor is used for controlling the variable capacitor. By choosing to pass DC current but not AC current, the control DC voltage can be applied only to the variable capacitance element, and the capacitance of the variable capacitance element can be changed at a low voltage, which is low. The entire capacity can be changed by the voltage.

  According to the variable capacitor of the present invention, 5) the third and fourth capacitive elements have a lower electrode, a dielectric, and an upper electrode, and the lower electrodes and the upper electrodes are adjacent to each other. In some cases, since the lower electrodes and the upper electrodes are adjacent to each other, the third capacitor and the fourth capacitor are efficiently and electrostatically coupled, and the variable capacitor of the present invention as described above Thus, it is possible to reliably obtain the operational effect.

  According to the variable capacitor of the present invention, 6) the third capacitor element includes a dielectric substrate and two adjacent electrodes formed on the dielectric substrate, and the fourth capacitor element includes the third capacitor element. When the dielectric layer formed on the capacitive element and two adjacent electrodes formed on the dielectric layer, the fourth capacitive element is on the dielectric layer formed on the third capacitive element. Therefore, the third capacitive element and the fourth capacitive element are efficiently and electrostatically coupled, and the above-described effects of the variable capacitor of the present invention can be obtained with certainty. Will be able to.

  According to the variable capacitor of the present invention, 7) when the third and fourth capacitive elements are composed of a dielectric substrate and four adjacent electrodes formed on the dielectric substrate, the third capacitor Since the element and the fourth capacitor element are composed of four adjacent electrodes formed on the dielectric substrate, the third capacitor element and the fourth capacitor element are efficiently and electrostatically coupled. Thus, the operational effects of the variable capacitor of the present invention as described above can be obtained with certainty.

  According to the variable capacitor of the present invention, 8) when the electrodes of the third and fourth capacitive elements are comb-shaped electrodes, the third capacitive element and the fourth capacitive element are formed by making the electrode shape a comb-shaped electrode. Since the distance in which the electrodes forming the capacitive element are adjacent to each other can be increased, electrostatic coupling between the third capacitive element and the fourth capacitive element can be strengthened. The effect of the variable capacitor can be obtained more reliably.

  As described above, according to the variable capacitor of the present invention, it is possible to provide a variable capacitor having a large capacitance change due to an applied voltage, a high Q value, and good temperature characteristics.

  Hereinafter, a variable capacitor according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an equivalent circuit of an example of an embodiment of a variable capacitor according to the present invention. In FIG. 1, C1 is a first capacitive element, C2 is a second capacitive element, C3 is a third capacitive element, C4 is a fourth capacitive element, CV1 is a first variable capacitive element, and CV2 is a first capacitive element. 2, N1 is a first connection point, and N2 is a second connection point. As described above, in the variable capacitor of the present invention, the first variable capacitor CV1 and the first capacitor C1 are connected in series, and the second variable capacitor CV2 and the second capacitor C2 are connected in series. And the outside of the first variable capacitance element CV1 and the outside of the second capacitance element C2 are connected at the first connection point N1, and the outside of the second variable capacitance element CV2 and the first capacitance element C1 By connecting the outside with the second connection point N2, the first variable capacitive element CV1 and the first capacitive element C1 connected in series, the second variable capacitive element CV2 connected in series and the first variable capacitive element CV2 The second capacitive element is connected in parallel, and the third capacitive element is between the first variable capacitive element CV1 and the first capacitive element C1 and between the second variable capacitive element CV2 and the second capacitive element C2. Capacitance element C3 is connected, and the first connection point N1 The fourth capacitive element C4 is connected between the second connection point N2 and the third capacitive element C3 and the fourth capacitive element C4 are electrostatically coupled to each other. Terminals are connected to N1 and the second connection point N2, respectively. A broken line surrounding the third capacitive element C3 and the fourth capacitive element C4 shown in FIG. 1 indicates that the third and fourth capacitive elements C3 and C4 are electrostatically coupled. As the variable capacitance elements CV1 and CV2, a dielectric thin film capacitor whose capacitance changes according to the applied voltage, a varactor diode whose capacitance changes according to the applied voltage, or a capacitor whose capacitance can be changed mechanically can be used. . Among these, when a dielectric thin film capacitor whose capacitance changes according to the applied voltage is used as the variable capacitance elements CV1 and CV2, the entire capacitance can be electrically controlled. Further, when a varactor diode whose capacitance changes according to the applied voltage is used as the variable capacitance elements CV1 and CV2, the entire capacitance can be electrically controlled. Furthermore, since the varactor diode is generally excellent in temperature characteristics, a variable capacitor having excellent temperature characteristics can be realized.

  Next, FIG. 2 is a circuit diagram showing an equivalent circuit of another example of the embodiment of the variable capacitor according to the present invention. The resistor R1 is connected in parallel to the first capacitor C1, and the second 3 shows an equivalent circuit of the variable capacitor of the present invention when a resistor R2 is connected in parallel to the capacitor element C2. According to the variable capacitor of the present invention of this example, the first and second capacitor elements C1 and C2 are open for the applied direct current, so that the variable capacitor element CV1 or CV2 and the resistor R1 or R2 is equivalent to that connected in series. Here, if the resistance value of the resistor R1 or R2 is sufficiently small compared to the impedance of the variable capacitance element CV1 or CV2, a voltage substantially the same as the DC voltage applied to the entire variable capacitance capacitor is applied to the variable capacitance element CV1 or CV2. Will be. In addition, since the impedance of the first and second capacitive elements C1 and C2 is small with respect to the applied alternating current, particularly high frequency, the resistance value of the resistor R1 or R2 is smaller than the impedance of the capacitive element C1 or C2. If it is sufficiently large, the resistors R1 and R2 are open, and the equivalent circuit of FIG. 2 is equivalent to the equivalent circuit of FIG. As a result, almost the same voltage as the DC voltage applied to the entire variable capacitor is applied to the first and second variable capacitance elements CV1 and CV2, so the first and second variable capacitances can be applied at a low voltage. The capacities of the elements CV1 and CV2 can be changed, and the capacity of the entire variable capacitor can be changed with a low voltage.

  The resistors R1 and R2 shown in FIG. 2 may be inductors having appropriate impedance as described above.

Next, FIG. 3 is a cross-sectional view showing a cross-sectional structure of an example of an embodiment of the capacitance forming portion of the third capacitor element and the fourth capacitor element in the variable capacitor of the present invention. In FIG. 3, 1 is a support substrate, 21 is a lower electrode of a third capacitor element, and 22 is a lower electrode of a fourth capacitor element arranged adjacent thereto. 31 is a thin film dielectric layer of the third capacitor element, and 32 is a thin film dielectric layer of the fourth capacitor element. Reference numeral 41 denotes an upper electrode of the third capacitive element, and reference numeral 42 denotes an upper electrode of the fourth capacitive element arranged adjacent thereto. Although not shown in FIG. 3, a protective film made of an organic material such as BCB resin or polyimide resin or an inorganic material such as SiN _x or SiO _x does not expose the thin film dielectric layers 31 and 32 to the atmosphere as necessary. It may be installed as follows.

  The support substrate 1 is a ceramic substrate such as alumina ceramic, a single crystal substrate such as sapphire, a glass substrate, a surface-oxidized Si substrate, or the like. Lower electrodes 21 and 22 are formed on the surface of the support substrate 1. The lower electrodes 21 and 22, the thin film dielectric layers 31 and 32, and the upper electrodes 41 and 42 are formed in the same batch on the entire surface of the support substrate 1 by a film forming method such as sputtering, and after the sputtering of all layers is completed. The upper electrodes 41 and 42, the thin film dielectric layers 31 and 32, and the lower electrodes 21 and 22 are formed into a predetermined shape by being physically or chemically etched using a photoresist layer having a predetermined shape.

  The lower electrodes 21 and 22 are electrode layers made of a single metal or alloy such as Au, Pt, Ag, Cu, and Al. The lower electrodes 21 and 22 are formed at a substrate temperature in the range of room temperature to 400 ° C. by a film forming method such as sputtering.

  The thicknesses of the lower electrodes 21 and 22 are the resistance component of the wiring from the terminal portion connected to them to the capacitance forming portion, the continuity of the lower electrodes 21 and 22 (both lower electrodes 21 and 22・ It is desirable that the thickness of 22 is thicker) and the adhesion to the support substrate 1 (in order to improve this, the thickness of the lower electrodes 21 and 22 is preferably relatively thin). For example, 0.1 to 10 μm. When the thickness of the lower electrodes 21 and 22 is smaller than 0.1 μm, the resistance of the lower electrodes 21 and 22 themselves increases, and at the same time, the continuity of the electrodes is lost and the reliability tends to be inferior. On the other hand, when the thickness of the lower electrodes 21 and 22 exceeds 10 μm, the adhesion reliability with the support substrate 1 tends to decrease or the support substrate 1 tends to warp.

The thin film dielectric layers 31 and 32 are layers of a dielectric material made of, for example, an oxide such as SiOx or a nitride such as SiNx. For example, the thin film dielectric layers 31 and 32 having a Q value of about 500 can be obtained by using Si ₃ N ₄ as a target and forming a film by a sputtering method at a substrate temperature of 400 ° C.

  The upper electrodes 41 and 42 are electrode layers made of a single metal or an alloy such as Au, Pt, Ag, Cu, and Al, like the lower electrodes 21 and 22.

  A variable impedance element (not shown) may be externally attached to the third and fourth capacitive elements, or a dielectric thin film capacitor is formed on the same support substrate 1 by a normal thin film process. You may make it.

  According to the variable capacitor of the present invention using the third and fourth capacitive elements as shown in FIG. 3, the lower electrodes 21 and 22 and the upper electrodes 41 and 42 are adjacent to each other. Since the capacitive element and the fourth capacitive element are efficiently electrostatically coupled, the capacitance can be changed according to the capacitance change of the variable capacitive element, and the thin film dielectric layers 31 and 32 can be changed. Since a dielectric having a high Q value can be used, the Q value of the entire variable capacitor can be increased.

Next, FIG. 4 is a cross-sectional view showing another example of the cross-sectional structure of the third capacitor element and the capacitor forming portion of the fourth capacitor element in the variable capacitor of the present invention. In FIG. 4, 10 is a dielectric substrate, 51 and 52 are two adjacent electrodes constituting the third capacitor element formed on the dielectric substrate 10, and 61 and 62 are the dielectric substrate 10 And two adjacent electrodes 51 and 52 are formed on the third capacitor element, and 71 and 72 are the fourth capacitor elements formed on the dielectric layers 61 and 62, respectively. Two adjacent electrodes that make up. Although not shown in FIG. 4, a protective film made of an organic material such as BCB resin or polyimide resin or an inorganic material such as SiN _x or SiO _x may prevent the dielectric layers 61 and 62 from being exposed to the atmosphere as necessary. You may install in.

  The dielectric substrate 10 is a ceramic substrate such as alumina ceramic, a single crystal substrate such as sapphire, a glass substrate, or the like. On the surface of the dielectric substrate 10, two adjacent electrodes 51 and 52 constituting the third capacitor element and the fourth capacitor element are formed.

The dielectric layers 61 and 62 are layers of a dielectric material made of an oxide such as SiO _x or a nitride such as SiN _x , for example. For example, the dielectric layers 61 and 62 having a Q value of about 500 can be obtained by using Si ₃ N ₄ as a target and forming a film by a sputtering method at a substrate temperature of 400 ° C.

  Two adjacent electrodes 51, 52 and 71, 72 are electrode layers similar to the above-described lower electrodes 21, 22 and upper electrodes 41, 42, and are formed in the same manner using the aforementioned materials. The third capacitive element and the fourth capacitive element are both called gap-type capacitors, and the distance between the two electrodes, the length of the adjacent portion, the dielectric substrate 10, and the dielectric layers 61 and 62 The capacitance is determined by the dielectric constant of the air gap. Further, since the fourth capacitive element is laminated on the third capacitive element via the dielectric layers 61 and 62, the distance between the third and fourth capacitive elements can be shortened. Electrostatic coupling can be strengthened.

  In the example shown in FIG. 4, the dielectric layers 61 and 62 formed on the third capacitive element are formed as independent layers on the two adjacent electrodes 51 and 52, respectively. The dielectric layers 61 and 62 may be formed as one continuous layer. In that case, the dielectric constant between the two adjacent electrodes 71 and 72 formed on the layer is larger than that through the air gap, and a fourth capacitive element having a larger capacitance may be obtained. it can.

  In contrast to the third and fourth capacitive elements, the first and second capacitive elements and the first and second variable capacitive elements that are not shown in the figure may be externally attached or may be the same by a normal thin film process. A dielectric thin film capacitor may be formed on the dielectric substrate 10 and connected.

  According to the variable capacitor of the present invention using the third and fourth capacitive elements as shown in FIG. 4, the fourth capacitive element is laminated on the third capacitive element via the dielectric layers 61 and 62. Since the third capacitive element and the fourth capacitive element are electrostatically coupled efficiently, the capacitance can be changed according to the capacitance change of the variable capacitive element, and the dielectric layer Since a dielectric having a high Q value can be used for 61 and 62, the Q value of the entire variable capacitor can be increased.

  Next, FIG. 5 is a cross-sectional view showing a cross-sectional structure of still another example of the embodiment of the third capacitor element and the capacitor forming portion of the third capacitor element in the variable capacitor of the present invention. In FIG. 5, 10 is a dielectric substrate, 211 is a first electrode of the third capacitor element, and 212 is a second electrode of the third capacitor element. Reference numeral 221 denotes a first electrode of the fourth capacitor element, and 222 denotes a second electrode of the fourth capacitor element.

  The dielectric substrate 10 is a ceramic substrate such as alumina ceramic, a single crystal substrate such as sapphire, or a glass substrate. Then, four adjacent electrodes 211, 212, 221, 222 are formed on the upper surface of the dielectric substrate 10, and a third capacitor element is formed by the dielectric substrate 10 and the two adjacent electrodes 211, 212. The fourth capacitive element is formed by the dielectric substrate 10 and the two adjacent electrodes 221 and 222, and the third capacitive element and the fourth capacitive element are formed by the two electrodes 212 and 221 being adjacent to each other. The capacitive element is electrostatically coupled. These four adjacent electrodes 211, 212, 221 and 222 are formed by physical or chemical etching using a photoresist having a predetermined shape.

  These four adjacent electrodes 211, 212, 221, and 222 are electrode layers made of a single metal or alloy such as Au, Pt, Ag, Cu, and Al. These four adjacent electrodes 211, 212, 221, and 222 are formed, for example, by sputtering so that the substrate temperature is in the range of room temperature to 400 ° C.

  The thicknesses of these four adjacent electrodes 211, 212, 221, 222 are the resistance component of the wiring from the terminal portion connected to them to the capacitance forming portion, the continuity of the electrodes 211, 212, 221, 222 (there are In order to improve the accuracy, it is desirable that the electrodes 211, 212, 221, and 222 are thicker in all cases.) And adhesion to the dielectric substrate 10 (in order to improve this, the electrodes 211, 212, 221, and 222 are improved). ) Is determined in consideration of, for example, 0.1 to 10 μm. If the thickness of these four electrodes 211, 212, 221 and 222 is smaller than 0.1 μm, the resistance of the electrodes 211, 212, 221 and 222 themselves will increase, and at the same time, the continuity of the electrodes will be lost and the reliability will tend to be inferior. is there. On the other hand, when the thickness of the electrodes 211, 212, 221, 222 exceeds 10 μm, the adhesion reliability with the dielectric substrate 10 tends to be lowered, or the dielectric substrate 10 tends to be warped.

  Next, FIG. 6A is a plan view showing a planar structure of still another example of the embodiment of the capacitance forming portion of the third capacitive element and the fourth capacitive element in the variable capacitor of the present invention. FIG. 6B is a cross-sectional view showing a cross-sectional structure along the line AA ′ in FIG. In FIG. 6, reference numeral 1 denotes a support substrate, 21 denotes a lower electrode of the third capacitive element, and 22 denotes a lower electrode of the fourth capacitive element arranged adjacent thereto. 31 is a thin film dielectric layer of the third capacitor element, and 32 is a thin film dielectric layer of the fourth capacitor element. Reference numeral 41 denotes an upper electrode of the third capacitive element, and reference numeral 42 denotes an upper electrode of the fourth capacitive element arranged adjacent thereto.

  In this example, the lower electrodes 21 and 22 and the upper electrodes 41 and 42 are respectively comb-shaped electrodes. Thus, by making the lower electrodes 21 and 22 and the upper electrodes 41 and 42 comb-shaped electrodes, the adjacent portions of the third capacitor element and the fourth capacitor element become longer. The capacitive element and the fourth capacitive element can be electrostatically coupled efficiently.

  As such a comb-shaped electrode, the third capacitive element and the fourth capacitive element are adjacent to each other in order to increase the degree of electrostatic coupling between the third capacitive element and the fourth capacitive element. The number of comb teeth is large, the length of the comb teeth portion is long, and the distance between the third capacitor element and the fourth capacitor element is short so that the length is as long as possible. desirable.

  In this example, the case where the lower electrodes 21 and 22 and the upper electrodes 41 and 42 are comb-shaped electrodes is shown with respect to the example shown in FIG. 3, but those electrodes are shown in the examples shown in FIGS. Similar effects can be obtained when 51, 52, 71, 72 or 211, 212, 221, 222 are comb-shaped electrodes.

  Next, FIG. 7A is a plan view showing a planar structure including a variable capacitance element, a capacitance element, a solder terminal and the like of the variable capacitance capacitor of the present invention, and FIG. 7B is a plan view in FIG. It is sectional drawing which shows the cross-section along an AA 'line. In FIG. 7, 701 is a supporting substrate, 702 is a lower electrode, 703 is a thin film dielectric layer, 704 is an upper electrode, 705 is an extraction electrode, 706 is a solder barrier layer, 707 is a solder adhesion layer, 708 is a protective film, 709 is Solder terminal. The variable capacitor of the present invention having such a configuration can be manufactured by a normal thin film process.

  The support substrate 701 is a ceramic substrate such as alumina ceramic, a single crystal substrate such as sapphire, a glass substrate, a surface-oxidized Si substrate, or the like. A lower electrode 702 is formed on the surface of the support substrate 701. The lower electrode 702, the thin film dielectric layer 703, and the upper electrode 704 are formed in the same batch on the entire surface of the support substrate 701 by a film forming method such as sputtering, and after the sputtering of all layers is completed, the upper electrode 704, the thin film dielectric 704 are formed. The body layer 703 and the lower electrode 702 are formed into a predetermined shape by physical or chemical etching using a photoresist layer having a predetermined shape.

  The lower electrode 702 is an electrode layer made of a single metal or alloy such as Au, Pt, Ag, Cu, and Al. The lower electrode 702 is formed at a substrate temperature in the range of room temperature to 400 ° C. by a film forming method such as sputtering.

  The thickness of the lower electrode 702 is the resistance component of the wiring from the terminal portion connected to them to the capacitance forming portion, the continuity of the lower electrode 702 (in order to improve these, the thickness of the lower electrode 702 is both thicker) And the adhesion to the support substrate 701 (in order to improve this, it is desirable that the thickness of the lower electrode 702 is relatively thin), for example, 0.1 to 10 μm. The When the thickness of the lower electrode 702 is smaller than 0.1 μm, the resistance of the lower electrode 702 itself increases, and at the same time, the continuity of the electrode is lost and the reliability tends to be inferior. On the other hand, when the thickness of the lower electrode 702 exceeds 10 μm, the adhesion reliability with the support substrate 701 tends to decrease, or the support substrate 701 tends to warp.

The thin film dielectric layer 703 is a layer of a dielectric material made of an oxide such as SiOx or a nitride such as SiNx. For example, a thin film dielectric layer 703 having a Q value of about 500 can be obtained by using Si ₃ N ₄ as a target and forming a film by a sputtering method at a substrate temperature of 400 ° C. Here, among the thin film dielectric layer 703, what is indicated as CV1 is a thin film dielectric layer that forms a capacitor whose capacitance changes according to the applied voltage. For example, Ba _0.5 Sr _{0.5 is used} as a target. By using TiO ₃ and forming a film by sputtering at a substrate temperature of 600 ° C., a thin film dielectric layer 703 having a capacitance change rate of about 60% by an applied voltage can be obtained. The lower electrode 702, the thin film dielectric layer 703, and the upper electrode 704 are formed in the same batch on the entire surface of the support substrate 701 by a film forming method such as sputtering, and after the sputtering of all layers is completed, the upper electrode 704, the thin film dielectric 704 are formed. Since the body layer 703 and the lower electrode 702 are each physically or chemically etched using a photoresist layer having a predetermined shape to be formed into a predetermined shape, first, the thin film dielectric layer is Ba _0.5 Sr _{0. .5} A laminated body having a predetermined shape made of TiO ₃ is manufactured, and subsequently a laminated body having a predetermined shape whose thin film dielectric layer is made of Si ₃ N _4, thereby obtaining a thin film dielectric layer 703 containing CV1. Can do.

  The upper electrode 704 is an electrode layer made of a single metal or alloy such as Au, Pt, Ag, Cu, and Al, like the lower electrode 702.

  The lead electrode 705 connects the first to fourth capacitive elements, or the first and second variable capacitive elements, and the terminals as appropriate. The extraction electrode 705 can be made of an inexpensive and low resistance metal such as Ag, Cu.

  The solder barrier layer 706 is formed to prevent the diffusion of solder to the electrodes during reflow. A metal such as Ni can be used for the solder barrier layer 706.

  The solder adhesion layer 707 is formed to adhere the solder terminal 709 and the solder barrier layer 706 together. For the solder adhesion layer 707, a metal having good wettability with solder such as Au can be used.

The protective film 708 is formed so as to expose the solder terminal 709. For the protective film 708, an organic substance such as BCB resin or polyimide resin, or an inorganic substance such as SiN _x or SiO _x can be used. Further, a multilayer structure of these materials may be used.

  The solder terminal 709 is formed by performing reflow after printing a solder paste.

  As a result, the lower electrode of the first capacitor is connected to the terminal on the second connection point side, the lower electrode of the second variable capacitor, and the upper electrode of the fourth capacitor, and the upper electrode is the first variable. Connected to the upper electrode of the capacitive element and the lower electrode of the third capacitive element.

  In the second capacitor element, the lower electrode is connected to the terminal on the first connection point side, the lower electrode of the first variable capacitor element, and the lower electrode of the fourth capacitor element, and the upper electrode is connected to the second variable capacitor. The upper electrode of the element and the upper electrode of the third capacitor element are connected.

  The first variable capacitor has a lower electrode connected to the terminal on the first connection point side, a lower electrode of the second capacitor, and a lower electrode of the fourth capacitor, and an upper electrode connected to the upper portion of the first capacitor. The electrode and the lower electrode of the third capacitor element are connected.

  In the second variable capacitor, the lower electrode is connected to the terminal on the second connection point side, the lower electrode of the first capacitor, and the upper electrode of the fourth capacitor, and the upper electrode is connected to the first variable capacitor. The upper electrode of the element and the lower electrode of the third capacitor element are connected.

  The third capacitor element has a lower electrode connected to the upper electrode of the first variable capacitor element and the upper electrode of the first capacitor element, and the upper electrode connected to the upper electrode of the second variable capacitor element and the second capacitor element. Connected to the upper electrode.

  In the fourth capacitor element, the lower electrode is connected to the terminal on the first connection point side, the lower electrode of the first variable capacitor element, and the lower electrode of the second capacitor element, and the upper electrode is on the second connection point side. , The second electrode of the second variable capacitor, and the lower electrode of the first capacitor.

  The third capacitive element and the fourth capacitive element are electrostatically coupled with each other because the lower electrodes 702 and the upper electrodes 704 are adjacent to each other.

  Thus, the variable capacitance capacitor of the present invention is configured, and the third variable capacitance element is changed by changing the capacitance of the first variable capacitance element and the second variable capacitance element by applying a DC voltage between the terminals. The voltage applied to the capacitor element is controlled, and as a result, the charge generated in the third capacitor element is controlled. Since the third capacitive element and the fourth capacitive element are electrostatically coupled, the charge generated in the fourth capacitive element is changed by the charge generated in the third capacitive element, and the fourth capacitive element Since the capacitance changes, the capacitance of the entire variable capacitance capacitor constituted by such a circuit changes.

  As described above, according to the variable capacitor of the present invention, it is possible to provide a variable capacitor having a large capacitance change due to an applied voltage, a high Q value, and good temperature characteristics.

  In addition, this invention is not limited to the example of the above embodiment, A various change may be added in the range which does not deviate from the summary of this invention. For example, the shape of the comb-teeth of the comb-shaped electrode may be a cross instead of a straight line, and in that case, the adjacent portion of the third capacitor element and the fourth capacitor element becomes longer. The electrostatic coupling between the two can be further strengthened.

  Based on the calculation of impedance by an equivalent circuit using a circuit simulator, the first and second variable capacitance elements CV1 and CV2 have a capacitance of 1 pF, a capacitance change due to an applied voltage is 67%, and a Q value is 50 dielectric thin film capacitors are used, capacitors having a capacitance of 1 pF and a Q value of 500 are used as the first to third capacitance elements C1 to C3, and capacitance is 0.1 pF as the fourth capacitance element C4. A variable capacitance capacitor of the present invention was configured with the configuration shown in FIG. 1 using a capacitor having a Q value of 500. When the capacitance, Q value, and capacitance change of this variable capacitor were measured, the overall capacitance was 1.7 pF, the Q value was 110, and the capacitance change due to the applied voltage was 51%.

  As a result, although the Q value of the entire variable capacitor is 110 even though the Q value of the first and second variable capacitors CV1 and CV2 is 50, according to the variable capacitor of the present invention. It was confirmed that the Q value was high and the capacitance change due to the applied voltage was large.

  The variable capacitor of the present invention in the example shown in FIGS. 3 to 6 is configured in the same manner. In any case, the variable capacitor has a high Q value and a large capacitance change due to the applied voltage. did it.

It is a circuit diagram which shows the equivalent circuit of an example of embodiment of the variable capacitor of this invention. It is a circuit diagram which shows the equivalent circuit of the other example of embodiment of the variable capacitor of this invention. It is sectional drawing which shows the cross-section of an example of embodiment of the capacity | capacitance formation part of the 3rd capacitive element and the 4th capacitive element in the variable capacitor of this invention. It is sectional drawing which shows the cross-section of the other example of embodiment of the capacity | capacitance formation part of the 3rd capacitive element and the 4th capacitive element in the variable capacitor of this invention. It is sectional drawing which shows the cross-section of further another example of embodiment of the capacity | capacitance formation part of the 3rd capacitive element and the 4th capacitive element in the variable capacitor of this invention. (A) is a top view which shows the planar structure of the further another example of embodiment of the capacity | capacitance formation part of the 3rd capacitive element and the 4th capacitive element in the variable capacitor of this invention, (b) is ( It is sectional drawing which shows the cross-sectional structure along the AA 'line in a). (A) is a top view which shows the planar structure containing the variable capacitance element of the variable capacitance capacitor of this invention, a capacitive element, a solder terminal, etc., (b) followed the AA 'line in (a). It is sectional drawing which shows a cross-section.

Explanation of symbols

1 ... Support substrate
10 ... Dielectric substrate
21, 22, ... Lower electrode
31, 32 ... Thin film dielectric layer
41, 42 ... Upper electrode
51, 52 ... 2 adjacent electrodes
61, 62 ... Dielectric layer
71, 72 ... two adjacent electrodes
211, 212, 221, 222 ... 4 adjacent electrodes
701 ... Support substrate
702 ... Lower electrode
703 ・ ・ ・ Thin dielectric layer
704 ... Upper electrode
705 ... Extraction electrode
706 ... Solder barrier layer
707 ・ ・ ・ Solder adhesion layer
708 ... Protective film
709: Solder terminal C1, C2, C3, C4 ... Capacitance element CV1, CV2 ... Variable capacitance element R1, R2 ... Resistance N1, N2 ... Connection point

Claims (8)

The first variable capacitive element and the first capacitive element connected in series, and the second variable capacitive element and the second capacitive element connected in series are connected to the outside of the first variable capacitive element and the The outside of the second capacitive element is connected at a first connection point, the outside of the second variable capacitive element and the outside of the first capacitive element are connected at a second connection point, and connected in parallel. A third capacitive element is connected between the first variable capacitive element and the first capacitive element and between the second variable capacitive element and the second capacitive element, and the first connection point and A fourth capacitive element is connected between the second connection points, the third capacitive element and the fourth capacitive element are electrostatically coupled, and the first connection point And a variable capacitance capacitor, characterized in that a terminal is connected to each of the second connection points. . 2. The variable capacitance capacitor according to claim 1, wherein the first and second variable capacitance elements are dielectric thin film capacitors whose capacitance changes according to an applied voltage. 2. The variable capacitor according to claim 1, wherein the first and second variable capacitance elements are varactor diodes whose capacitance changes according to an applied voltage. 4. The variable capacitor according to claim 1, wherein a resistor or an inductor is connected in parallel to each of the first and second capacitive elements. 5. The third and fourth capacitive elements each have a lower electrode, a dielectric, and an upper electrode, and the lower electrodes and the upper electrodes are adjacent to each other. 5. The variable capacitor according to any one of 4 above. The third capacitive element includes a dielectric substrate and two adjacent electrodes formed on the dielectric substrate, and the fourth capacitive element is a dielectric formed on the third capacitive element. 5. The variable capacitor according to claim 1, comprising a body layer and two adjacent electrodes formed on the dielectric layer. The third and fourth capacitive elements each comprise a dielectric substrate and four adjacent electrodes formed on the dielectric substrate. Variable capacitor. The variable capacitor according to claim 5, wherein the electrodes of the third and fourth capacitive elements are comb electrodes.

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