JP2002110928A - Capacitor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor device inserted in parallel in a high frequency balanced line to be integrated, enabling its area to be reduced, especially without sacrificing the high-frequency characteristics. SOLUTION: A pair of upper and lower electrodes opposed through a dielectric layer are each divided into two in a symmetric shape, and the divided upper and lower electrodes are connected crosswise. The divided upper and lower electrodes especially have their respective projections extending opposite from main portions opposed through the dielectric layer to their divided parts. The projections are crosswise connected and oppositely superposed between the divided upper and lower electrodes. These cross connections are respectively connected, using conductors piercing the dielectric layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor which is interposed in parallel with a high-frequency balanced line to form an integrated circuit.
In particular, the present invention relates to a capacitor device whose area can be reduced without sacrificing high-frequency characteristics.

[0002]

[Related Background Art] A high frequency circuit such as a power amplifier section in a mobile phone is usually realized as a balanced circuit.
As illustrated in FIG. 5, a capacitor C1 is inserted in parallel with the high-frequency balanced line, and a capacitor C2 is inserted in series. The capacitor C1 is connected in parallel between the high-frequency balanced lines L1 and L2 and a virtual ground point, and the capacitor C2 is connected in series to the high-frequency balanced lines L1 and L2.

In recent years, various attempts have been made to integrate such a high-frequency circuit into an integrated circuit using a compound semiconductor such as GaAs having excellent high-frequency characteristics. In this case, as shown in the schematic plan view of FIG. 6, the capacitor C1 has upper electrode bodies U1 and U2 symmetrically disposed on both sides of two high-frequency balanced lines L1 and L2. This is realized by burying a common lower electrode body D under a predetermined dielectric layer (not shown) below the upper electrode bodies U1 and U2. In the capacitor C2, upper electrode bodies U3 and U4 are provided at each end of the two high-frequency balanced lines L1 and L2, and a predetermined dielectric layer is provided below each of these upper electrode bodies U3 and U4. The lower electrode bodies D3 and D4 are respectively buried and formed. Then, a pair of high-frequency balanced lines L1, L2 is formed from these lower electrode bodies D3, D4.
Is pulled out.

[0004]

However, the capacitor C1 realized as described above occupies a considerably large area, and it cannot be denied that it hinders the miniaturization of the integrated circuit. Therefore, two capacitors C1 inserted in parallel with the high-frequency balanced lines L1 and L2 form a series circuit,
As shown in FIG. 7, the capacitance is 1/2 (= C1 / 2).
Paying attention to the fact that the capacitor Ca can be replaced with a plurality of capacitors, it is conceivable to realize the capacitor Ca as shown in FIG. That is, the capacitor Ca is formed, for example, by embedding a predetermined half of the upper electrode body Ua formed on the side of one of the high-frequency balanced lines L2 under the upper electrode body Ua with a predetermined dielectric layer interposed therebetween. Realized by the lower electrode body Da,
It is conceivable to connect the lower electrode body Da to the other high-frequency balanced line L1.

However, in this case, since the capacitor Ca is provided asymmetrically only on one side of the pair of high-frequency balanced lines L1 and L2, if the electric field balance and the magnetic field balance in the high-frequency balanced circuit are broken, and the high-frequency characteristics are degraded. The problem described above occurs. In addition, since the connection position (tap) between the pair of high-frequency balanced lines L1 and L2 and the capacitor Ca is divided into an upper electrode body Ua and a lower electrode body Da, new problems such as a difference in line length arise.

The present invention has been made in view of such circumstances, and has as its object to reduce the area of the integrated circuit without sacrificing high-frequency characteristics, and to reduce the size of the entire integrated circuit. It is to provide a capacitor device which can be used.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, a capacitor device according to the present invention is interposed in parallel with a high-frequency balanced line and integrated with the high-frequency balanced line. The upper electrode body and the lower electrode body, which are opposed to each other via the dielectric layer, are divided into two symmetrical shapes, and the upper electrode body and the lower electrode body divided into two are cross-connected. It is characterized by.

Preferably, the upper electrode body and the lower electrode body which are divided into two parts are oppositely directed from the main body part opposed to each other via the dielectric layer toward the divided part. The upper electrode body and the lower electrode body are formed as cross-connecting portions overlapping in opposite directions between the two divided upper electrode bodies and the lower electrode bodies.

According to a third aspect of the present invention, the upper electrode body is divided into two parts by providing a conductor that vertically connects the respective projecting parts that penetrate through the dielectric layer and overlap each other at the cross connection part. And the lower electrode body is cross-connected. That is, in the capacitor device according to the present invention, as shown in FIG. 1, the capacitance obtained by integrating two capacitors C1 inserted in parallel with the high-frequency balanced lines L1 and L2 is reduced to 1/2 (= C1). / 2) by replacing the capacitor Ca (capacitor device) with two capacitors Cb and Cb (capacitor elements) connected in parallel, thereby further reducing the capacitance by 1/2 (=
C1 / 4), and by providing these capacitors Cb, Cb in anti-parallel, they are connected in parallel to the high-frequency balanced lines L1, L2 while maintaining their electric and magnetic field balances, without sacrificing high-frequency characteristics. The feature is that the area is reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A capacitor device for a high-frequency balanced circuit according to one embodiment of the present invention will be described below with reference to the drawings. The capacitor device according to this embodiment includes:
The high-frequency balanced lines L1 and L2 are inserted in parallel, and as shown in FIG.
Two capacitor elements (Cb,
Cb) 10, 20 are realized. These capacitor elements 10 and 20 have shapes symmetrical to each other, and have a predetermined size (area) of the upper electrode body 11 and 20.
12 and a dielectric layer 12,
And lower electrode bodies 13 and 23 which are opposed to each other with an interposition 22 therebetween.

The dielectric layers 12 and 22 are made of a nitride or the like having a predetermined thickness, and the lower electrode bodies 13 and 23 are connected to a semiconductor substrate (not shown) of GaAs or the like via the dielectric layers 12 and 22. An embedded circuit is formed by embedding the above. Then, the upper electrode body 11 of the capacitor element 10 and the lower electrode body 23 of the capacitor element 20 are connected.
By cross-connecting the lower electrode body 13 of the element 10 with the lower electrode body 13, these two capacitor elements 1
0 and 20 are connected in anti-parallel to each other to equivalently constitute one capacitor device (Ca) inserted in parallel with the high-frequency balanced lines L1 and L2.

That is, as shown in a schematic plan view of FIG. 3 and a schematic exploded perspective view of FIG. 4, a pair of upper and lower capacitors arranged opposite to each other with a dielectric layer interposed therebetween. Each of the electrode bodies is divided into two symmetrical shapes to form two capacitor elements 10 and 20, and these two capacitor elements 10, 20 are connected in antiparallel to be realized. The upper electrode bodies 11 and 21 and the lower electrode bodies 13 and 23 of the capacitor elements 10 and 20 are respectively formed from a rectangular main body A opposed to each other with the dielectric layers 12 and 22 interposed therebetween. Projections B projecting in opposite directions toward the other capacitor element side
Respectively. And by making these protrusions B enter each other, the upper electrode body 11,
21 and the respective protruding portions B between the lower electrode bodies 13 and 23.
Are overlapped in the opposite directions to form a cross-connecting portion C for connecting the two capacitor elements 10 and 20 in anti-parallel.

In this cross-connecting portion, the protruding portion B protruding from the upper electrode body 11 penetrating through the dielectric layers 12 and 22 and the protruding portion B protruding from the lower electrode body 23
And a conductor 24 connecting the protruding portion B protruding from the upper electrode body 21 and the protruding portion B protruding from the lower electrode body 13. The conductors 14 and 24 connect the upper electrode bodies 11 and 21 and the lower electrode bodies 13 and 23 of the two capacitor elements 10 and 20 in antiparallel with each other.

Thus, according to the capacitor device having such a structure, as shown in FIG. 3, a pair of high-frequency balanced lines L1 and L2 and two capacitor elements 10,
20 can be arranged symmetrically. In addition, the capacitance of each of the capacitor elements 10 and 20 may be 1/4 (= C1 / 4) as described with reference to FIG.
4 and the size (area) of the capacitor device as a whole can be reduced to ２.

With such a structure, the high-frequency balanced lines L1 and L2 are symmetrical, and the balance of the capacitor elements 10, 20 with respect to the electric and magnetic fields can be ensured with good symmetry. In addition, since the high-frequency balanced lines L1 and L2 need only be connected to the upper electrode bodies 11 and 21 of the capacitor elements 10 and 20, respectively, the line lengths can be set equal. Therefore, the high-frequency characteristics of a high-frequency circuit in which a capacitor device is inserted in parallel with the high-frequency balanced lines L1 and L2 can be maintained at a sufficiently high level. A great effect can be obtained.

The present invention is not limited to the above embodiment. For example, the upper electrode bodies 11 and 21 described above
The size (area) of the lower electrode members 13 and 23 and the distance between the opposing electrodes and the like may be determined according to the capacitance required for the capacitor device, the dielectric constant of the dielectric layers 12 and 22, and the like. The shape can be variously modified in accordance with, for example, trial use of a power amplifier unit which is simultaneously integrated. Projection B
Is sufficient if the two capacitor elements 10 and 20 are formed to project in opposite directions so that they can cross each other. Other. The present invention can be implemented with various modifications without departing from the scope of the invention.

[0017]

As described above, according to the capacitor device of the present invention, two capacitor elements realized by symmetrically dividing the upper electrode body and the lower electrode body into two parts are connected in anti-parallel and equivalently. Since a single capacitor is realized, even in the case of being interposed in parallel with a high-frequency balanced line, a balance with respect to an electric field or a magnetic field can be secured and the line length can be equalized, so that high-frequency characteristics are sacrificed. Since the electrode area can be reduced to １ ／, there is an enormous effect that it can greatly contribute to the integration of a high-frequency circuit.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the configuration principle of a capacitor device according to the present invention.

FIG. 2 is a sectional view showing a schematic configuration of a capacitor device according to an embodiment of the present invention.

FIG. 3 is a schematic plan view of a capacitor device according to an embodiment of the present invention.

FIG. 4 is a schematic exploded perspective view of a capacitor device according to an embodiment of the present invention.

FIG. 5 is a diagram showing an example of a capacitor inserted in a high-frequency balanced line.

FIG. 6 is a view showing an example of realizing the capacitor shown in FIG. 5;

FIG. 7 is a diagram showing equivalent conversion of a capacitor.

FIG. 8 is a diagram showing an implementation example of the capacitor shown in FIG. 7 and its problems.

[Explanation of symbols]

 10,20 Capacitor element 11,21 Upper electrode body 12,22 Dielectric layer 13,23 Lower electrode body 14,24 Conductor (cross connection part) A Main part of electrode body B Projection of electrode body L1, L2 High frequency balance line

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H01G 4/38 F term (Reference) 5E082 AB03 BB05 CC03 EE05 EE11 EE23 FF05 FG03 FG22 GG10 JJ03 JJ15 JJ23 KK01 KK07 MM21 5F038 AC02 AC04 AC15 AC17 AC20 CA01 EZ02 EZ20

Claims (3)

[Claims] 1. A capacitor device interposed in parallel with a high-frequency balanced line and integrated with the high-frequency balanced line, comprising a pair of an upper electrode body and a lower electrode which are opposed to each other via a dielectric layer. A capacitor device characterized in that the body is divided into two symmetrical shapes, and the upper electrode body and the lower electrode body divided into two are cross-connected. 2. The two-parted upper electrode body and the lower electrode body each have a protruding part projecting in opposite directions from a main body part opposed to the main body part via the dielectric layer toward the divided part. 2. The capacitor device according to claim 1, wherein the projecting portions serve as cross-connecting portions that overlap in opposite directions between the two divided upper electrode bodies and lower electrode bodies. 3. The capacitor device according to claim 2, wherein the cross-connecting portion is provided with a conductor penetrating the dielectric layer and vertically connecting the respective projecting portions overlapping each other.