JP2856701B2 - Microwave circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave circuit, and more particularly to a dielectric resonance oscillator (DR) using a dielectric resonator.
O) and a microwave circuit such as a filter.

[0002]

2. Description of the Related Art A conventional microwave circuit using a dielectric resonator will be described with reference to the drawings. FIG. 10A is a perspective view showing a first example of a microwave circuit using a conventional dielectric resonator, and FIG. 10B is AA ′ of FIG. 10A.
It is sectional drawing which follows a line.

As shown in FIGS. 10A and 10B, in this conventional microwave circuit, a center conductor 3 of a microstrip line is formed on a surface of a semiconductor substrate 2 provided with a ground conductor 1 on a back surface. The dielectric resonator 4 is fixed near the center conductor 3 with an adhesive or the like.

FIG. 11A is a perspective view showing a second example of a microwave circuit using a conventional dielectric resonator.
FIG. 12B is a cross-sectional view taken along line AA ′ of FIG.

As shown in FIGS. 11A and 11B, in this conventional microwave circuit, a center conductor 3 of a microstrip line is formed on the surface of a semiconductor substrate 2 having a ground conductor 1 on the back surface. Further, the dielectric resonator 4 is fixed to the vicinity of the center conductor 3 via a support 5 with an adhesive or the like.

The support base 5 is usually formed by molding using quartz glass or the like as a material, and is previously attached to the back surface of the dielectric resonator 4 with an adhesive. Further, as another example of the support 5, a thick film made of an insulating material may be printed on the semiconductor substrate 2 as described in JP-A-7-38311. Vessel 4
Is fixed on this thick film body with an adhesive.

[0007]

In the first example of the conventional microwave circuit shown in FIG. 10, since the dielectric resonator 4 is directly arranged on the semiconductor substrate 2, the dielectric resonator 4 There is a problem that the distance between the ground conductor 1 and the ground conductor 1 is small, and the reduction of the no-load Q value of the resonance system due to the conductor loss of the ground conductor 1 increases.

Although the reduction of the no-load Q value can be suppressed by increasing the thickness of the semiconductor substrate 2, it is necessary to increase the width of the center conductor 3 in order to obtain the same characteristic impedance of the microstrip line. Leads to an increase. Further, in the case of a monolithic integrated circuit in which active elements are integrated, an increase in the thickness of the semiconductor substrate leads to a deterioration in heat dissipation and an increase in the diameter of the via hole. Therefore, the thickness of the semiconductor substrate 2 cannot be freely increased.

On the other hand, in the second example of the conventional microwave circuit shown in FIG. 11, the thickness of the semiconductor substrate 2 is increased by fixing the dielectric resonator 4 via the support 5. Without this, the distance between the dielectric resonator 4 and the ground conductor 1 can be increased, and a decrease in the no-load Q value due to the conductor loss of the ground conductor 1 can be suppressed.

However, the distance between the dielectric resonator 4 and the center conductor 3 in the direction perpendicular to the surface of the semiconductor substrate 2 (the distance in the thickness direction of the support base 5) increases, and the distance between the dielectric resonator 4 and the center conductor 3 is increased. There is a problem that the bonding strength between them decreases.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a microwave circuit capable of increasing a no-load Q value without increasing a substrate thickness.

Another object of the present invention is to provide a microwave circuit capable of suppressing a decrease in coupling strength between a dielectric resonator and a center conductor.

Still another object of the present invention is to provide a microwave circuit capable of suppressing a characteristic variation due to a displacement of a resonator.

[0014]

To achieve the above object, a microwave circuit according to a first aspect of the present invention is a microwave circuit in which a dielectric resonator is magnetically coupled to a microstrip line. The surface of the substrate that constitutes a part of the microstrip line is higher than the bottom of the dielectric resonator.
The dielectric resonator was fixed via the support having a large surface , and the center conductor forming a part of the microstrip line was protruded from the dielectric resonator of the support .
It is formed on each of the surface portion and the surface of the substrate.

According to the present invention, the dielectric resonator is fixed on the support and the center conductor of the microstrip line is formed on the support, so that the dielectric resonator is not increased without increasing the thickness of the substrate. The dielectric resonator can be kept away from the ground conductor without increasing the distance between the conductor and the center conductor in the direction perpendicular to the substrate surface.

In order to achieve the above object, a microwave circuit according to claims 2 and 3 of the present invention is characterized in that the support for the microwave circuit according to claim 1 is mounted on the substrate by etching the substrate or on the substrate. It is characterized by being formed by an insulating film deposited on the substrate.

A microwave circuit according to a fourth aspect of the present invention is characterized in that the center conductor in the microwave circuit according to the first aspect is connected to a transistor to form a monolithic integrated circuit.

According to a fifth aspect of the present invention, there is provided a microwave circuit, comprising: a substrate on which a support is formed in the microwave circuit according to the first aspect, comprising: a feedback line connected to at least a center conductor; Is an insulating substrate formed on the surface, and the central conductor is connected to the transistor chip via a connection line to form a hybrid integrated circuit.

Further, in the microwave circuit according to a sixth aspect of the present invention, the support base in the microwave circuit according to the first aspect is such that a part of a joint portion with the dielectric resonator is a hollow portion. It is characterized by. According to the present invention, the negative portion of the support that forms the support is air or vacuum having a small dielectric loss.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A is a perspective view of a microwave circuit according to an embodiment of the present invention, and FIG.
It is sectional drawing which follows the A 'line. As shown in FIGS. 1A and 1B, the microwave circuit of this embodiment includes a ground conductor 1 and a semiconductor substrate 2 having the ground conductor 1 formed on the back surface.
, A center conductor 3, a columnar dielectric resonator 4 arranged near the center conductor 3, and a support 6.

Ground conductor 1, semiconductor substrate 2 and center conductor 3
Constitutes a microstrip line. Support 6
Has a portion protruding from the dielectric resonator 4, and the central conductor 3 is formed in a part thereof. The dielectric resonator 4 is fixed to the support 6 near the center conductor 3 with an adhesive or the like.

As described above, in the microwave circuit according to the present embodiment, the height of the support 6 is increased in order to keep the dielectric resonator 4 away from the ground conductor 1 for the purpose of suppressing the deterioration of the no-load Q value. Even if the height is increased, the dielectric resonator 4
Since both the center conductor 3 and the center conductor 3 are placed, the distance between the dielectric resonator 4 and the center conductor 3 in the direction perpendicular to the surface of the semiconductor substrate 2 does not increase. Therefore, even if the thickness of the semiconductor substrate 2 is not increased, and even if the height of the support 6 is increased, a decrease in the bonding strength can be suppressed.

Next, the manufacturing process of the embodiment of the method for manufacturing the microwave circuit of FIG. 1 will be described with reference to FIGS. 2 (a) to 2 (d). This manufacturing method is characterized in that the support 6 is formed of a semiconductor substrate. First, as shown in FIG. 2A, by etching the semiconductor substrate 2, the support 6 shown in FIG.
Is formed. Next, as shown in FIG. 2B, the center conductor 3 is formed on the support 6a. Subsequently, if necessary, the substrate thickness is adjusted by polishing or the like, and then, as shown in FIG.
To form Finally, as shown in FIG. 2D, the dielectric resonator 4 is fixed on the support 6a and in the vicinity of the center conductor 3 with an adhesive or the like.

Next, another embodiment of the method of manufacturing the microwave circuit shown in FIG. 1 will be described with reference to FIGS. 3 (a) to 3 (d).
It is explained together with. This manufacturing method is characterized in that the support 6 is formed of an insulating film. First, a low-loss insulating film 7 is deposited on the semiconductor substrate 2 as shown in FIG. Next, as shown in FIG. 3 (b), the insulating film 7 is etched to form a support 6b made of the insulating film 7 (the support 6 in FIG. 1).
Is formed). Next, as shown in FIG. 3C, the center conductor 3 is formed on the support 6b. Subsequently, the ground conductor 1 is formed on the back surface of the semiconductor substrate 2 as shown in FIG. Finally, as shown in FIG. 3E, on the support 6b,
Further, the dielectric resonator 4 is fixed near the center conductor 3.

In either of the manufacturing methods shown in FIGS. 2 and 3,
In the case of monolithic integration, a process for manufacturing a transistor or a passive element is inserted between the processes shown in FIGS.

FIG. 4 shows a microwave circuit according to the present invention as an MMIC.
(Microwave Monolithic Integrated Circuit) A plan view of an example when applied to a dielectric resonance oscillator (DRO) is shown. The DRO shown in FIG. 4 includes a semiconductor substrate 2 having a ground conductor on the back surface, a center conductor 3, a support 6, a dielectric resonator 4,
Via hole 10, resistor 11, MIM capacitor 1
2. Bias pad 13, output pad 14, matching open stub 15, feedback line 16, 1/4 wavelength line 1.
7, gate electrode 18, drain electrode 19, source electrode 2
0, an active layer 21.

The gate electrode 18, the drain electrode 19, the source electrode 20, and the active layer 21 constitute a field effect transistor (FET). One end of the center conductor 3 is connected to the gate electrode 18 and the other end is connected to the resistor 11. Further, the drain electrode 19 is connected to the center conductor 3 by the feedback line 16 via the MIM capacitor 12.

The DRO is a parallel feedback type oscillation circuit that performs feedback by the feedback line 16 and generates a negative resistance. By loading the dielectric resonator 4 having a large unloaded Q value and a temperature coefficient of an appropriate value, an oscillation circuit having small phase noise and high temperature stability can be realized. A DC voltage is applied from the bias pad 13 to the gate electrode 18 and the drain electrode 19 of the FET. The resistor 11 is added to prevent parasitic oscillation, and the MIM capacitor 12 is added to block DC current.

FIG. 5 shows a microwave circuit according to the present invention using an HIC.
(Hybrid Integrated Circuit) Dielectric Resonant Oscillator (D
(RO) is a plan view of an example when applied to (RO). As shown in the figure, this DRO is composed of a center conductor 3, a dielectric resonator 4, a support 6, a resistor 11, a MIM capacitor 12, an output pad 14, a matching open stub 15, a feedback line 16, 1 / Insulating substrate 22 on which four-wavelength line 17 is formed
And the gate electrode 18, the drain electrode 19, and the source electrode 2
The FET chip 25 having the active layer 21 and the chip capacitor 24 are fixed on the metal block 23, and are electrically connected to each other by the gold wire 26.

FIG. 6 is a sectional view showing an embodiment in which the microwave circuit of the present invention is mounted on a shield case having adjustment screws. A chip of a circuit using the dielectric resonator 4 like the microwave circuit of the present invention is usually mounted on a shield case 28 having an adjusting screw 27 as shown in FIG.

FIG. 7A is a cross-sectional view showing another embodiment of the microwave circuit according to the present invention, and FIG. 7B is a plan view thereof. In the microwave circuit of this embodiment, a hollow portion 29 is formed in a part of the support 5. The hollow portion 29 can be formed at the time of forming the support 6 by etching in the manufacturing process shown in FIG. In this case, a part of the support that forms the support 6 is made into air or vacuum with a small dielectric loss by the hollow portion 29.

[0033]

Embodiments of the present invention will be described below with reference to the drawings.

In the microwave circuit of the present invention shown in the perspective view of FIG. 1A and the cross-sectional view of FIG. 1B, a ground conductor 1 made of 20 μm thick gold, a semiconductor substrate 2 made of 40 μm thick GaAs, Center conductor 3 made of gold having a thickness of 2 μm and a width of 30 μm, a cylindrical Ba having a radius of 650 μm and a height of 550 μm
Dielectric resonators 4 and 10 made of (Mg, Ta) O ₃
It is composed of a support 6 made of GaAs having a thickness of μm.

The support 6 in the microwave circuit of the present invention
In the manufacturing process for forming a semiconductor substrate on a semiconductor substrate, first, FIG.
As shown in (a), a 10 μm-thick support 6a is formed by etching using a sulfuric acid-based etchant or the like on the surface of a 600 μm-thick GaAs semiconductor substrate 2. At this time, a photoresist is used for patterning the support 6a. The lithography technique using is used.

Next, as shown in FIG. 2B, a center conductor 3 made of gold having a thickness of 2 μm is formed on the support 6a. In this step, for example, 0.5 μm of Ti / Pt / Au is used.
a process of forming a metal thin film of about m by sputtering, a lithography process for patterning the center conductor 3,
The method includes a step of plating gold serving as the central conductor 3, a step of removing the photoresist with an organic solvent, and a step of removing the metal thin film by milling.

Thereafter, the substrate thickness is reduced to 4 by polishing and etching.
0 μm, and 20 μm by plating as shown in FIG.
A ground conductor 1 made of gold having a thickness of μm is formed on the back surface of the semiconductor substrate 2 by plating or the like.

Finally, as shown in FIG. 2D, the dielectric resonator 4 is fixed on the support 6a with an adhesive or the like.

Next, in the microwave circuit of the present invention,
In a manufacturing process for forming the support 6 with an insulating film, first, FIG.
As shown in FIG. 1A, an insulating film 7 made of SiO ₂ or the like is deposited on a semiconductor substrate 2 to a thickness of about 5 μm by a plasma CVD method or the like.

Next, as shown in FIG. 3B, the insulating film 7 is etched by using buffered hydrofluoric acid or the like as an etchant.
Is formed. At this time, a lithographic technique using a photoresist is used for patterning the support 6b.

Next, as shown in FIG. 3C, a center conductor 3 made of gold having a thickness of 2 μm is formed on the support 6b. This step is performed, for example, with 0.5 of Ti / Pt / Au or the like.
forming a metal thin film of about μm by sputtering;
A lithographic step for patterning the center conductor;
It comprises a step of plating gold as a central conductor, a step of removing the photoresist with an organic solvent, and a step of removing the metal thin film by milling.

After that, the substrate thickness is also reduced to 4 by polishing and etching.
0 μm, and as shown in FIG.
A ground conductor 1 made of gold having a thickness of μm is formed on the back surface of the semiconductor substrate 2 by plating or the like.

Finally, as shown in FIG. 3E, the dielectric resonator 4 is fixed on the support 6b with an adhesive or the like.

In either of the manufacturing methods shown in FIGS. 2 and 3,
In the case of a monolithic integrated circuit, a manufacturing process of a transistor or a passive element is inserted between the processes shown in FIGS.

Next, an embodiment in which the microwave circuit of the present invention shown in FIG. 4 is applied to an MMIC dielectric resonance oscillator (DRO) will be described. A semiconductor substrate 2 made of GaAs having a thickness of 40 μm having a ground conductor made of gold having a thickness of 20 μm on the back surface; a center conductor 3 made of gold having a thickness of 30 μm and a width of 30 μm;
50 μm, 550 μm height cylindrical Ba (Mg, T
a) Dielectric resonator 4 made of O ₃ , 30 μm square via hole 10, epitaxial layer and Au / Ge / Ni / A
u Ohmic metal resistor 11, MIM capacitor 12 using SiNx for dielectric film, bias pad 1
3, output pad 14, matching open stub 15, feedback line 16, quarter wavelength line 17, gate electrode 18 made of Ti / Al, drain electrode 19 made of Au / Ge / Ni / Au ohmic metal, and source electrode 20 and an active layer 21.

Next, an embodiment in which the microwave circuit of the present invention shown in FIG. 5 is applied to a HIC dielectric resonance oscillator (DRO) will be described. In this DRO, a center conductor 3, a support 6, a dielectric resonator 4, a resistor 11, a MIM capacitor 12, an output pad 13, a matching open stub 15, a feedback line 13, and a 1/4 wavelength line 17 are formed. An insulating substrate 22 made of alumina having a thickness of 100 μm;
A gate electrode 18, a drain electrode 19, a source electrode 20,
An FET chip 25 having an active layer 21 and a chip capacitor 24 are configured by being fixed on a metal block 23 in which a 5 mm-thick copper surface is plated with gold, each of which has a gold wire 26 having a diameter of about 10 μm. It is electrically connected using this. The support 6 is formed by etching an insulating substrate 22 made of alumina.

Next, an example of an embodiment in which the microwave circuit of the present invention shown in FIG. 6 is mounted on a shield case having adjustment screws will be described. Circuit chips using a dielectric resonator, such as the microwave circuit of the present invention, are usually
It is used by being mounted on a shield case 28 having an adjustment screw 27 as shown in FIG. The shield case 28
It is made of metal with a 5 mm thick copper surface plated with gold, and has a closed structure. The adjusting screw 27 has a screw-type vertically movable structure.

Next, an embodiment of the microwave circuit of the present invention shown in FIG. 7 will be described. The dimensions, materials, and the like of this microwave circuit are the same as those of the microwave circuit shown in FIG. However, a hollow portion 29 having a radius of 500 μm and a depth equal to the height of the support base is formed in a part of the support base 6. This hollow portion 29 can be formed by changing the patterning of the support 6a in the manufacturing process shown in FIG.

FIG. 8 is a graph obtained by calculating the dependency of the no-load Q value on the height of the support base in one embodiment of the microwave circuit. When the dielectric resonator 4 is directly disposed on the substrate 2 as in the conventional microwave circuit shown in FIG. 10, the height of the support stand is equal to zero. As can be seen from FIG. 8, the unloaded Q value increases by increasing the height of the support base. In this regard, the microwave circuit of the present invention and the conventional microwave circuit shown in FIG. 11 both have a support, and therefore have no support, compared to the conventional microwave circuit shown in FIG. It is advantageous.

FIG. 9 is a graph showing an embodiment of the microwave circuit of the present invention and the dependency of the external Q value on the height of the support base of the conventional microwave circuit shown in FIG. 11 by calculation.
The external Q value indicates the strength of the coupling between the microstrip line and the dielectric resonator, and the smaller the external Q value, the greater the coupling strength.

The solid line I shows the characteristics of the external Q value and the height of the support in the microwave circuit according to one embodiment of the present invention in which the center conductor 3 is formed on the support 6, and the dotted line II shows the characteristic of the center conductor 3 on the substrate. 11 shows the characteristics of the external Q value and the height of the support base in the conventional microwave circuit shown in FIG.

As shown in FIG. 9, while the external Q value of the conventional microwave circuit increases as the height of the support base increases, the external Q value of the microwave circuit according to one embodiment of the present invention is is decreasing. That is, as the height of the support base increases, the coupling strength of the conventional microwave circuit decreases, and the coupling strength of the microwave circuit of the present invention increases. This is because, in the embodiment of the present invention shown in FIG. 1, by mounting both the dielectric resonator 4 and the center conductor 3 on the support 6, even if the height of the support 6 is increased, the dielectric This is because the dielectric resonator 4 can be kept away from the ground conductor 1 without increasing the distance between the resonator 4 and the center conductor 3 in the direction perpendicular to the surface of the semiconductor substrate 2.

The present invention is not limited to the above embodiment. For example, the width of the support 6 may be smaller than the width of the dielectric resonator 4.

[0054]

As described above, according to the present invention,
By placing both the dielectric resonator and the center conductor on the support, without increasing the substrate thickness, and without increasing the distance between the dielectric resonator and the center conductor in the direction perpendicular to the semiconductor substrate surface, Since the dielectric resonator can be kept away from the ground conductor, deterioration of the no-load Q value can be suppressed while simultaneously preventing an increase in the substrate thickness and a decrease in the coupling strength.

Further, according to the present invention, since the negative part of the support base forming the support base is made of air or vacuum having a small dielectric loss, deterioration of the no-load Q value due to the dielectric loss of the support base is suppressed. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view and a cross-sectional view of an embodiment of a microwave circuit according to the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a manufacturing process of the microwave circuit of FIG.

FIG. 3 is a cross-sectional view illustrating another example of the manufacturing process of the microwave circuit in FIG. 1;

FIG. 4 is a plan view of an example in which the microwave circuit of the present invention is applied to a dielectric resonance oscillator of an MMIC.

FIG. 5 is a plan view of an example in which the microwave circuit of the present invention is applied to a dielectric resonance oscillator of a HIC.

FIG. 6 is a cross-sectional view illustrating a method for mounting a microwave circuit according to the present invention.

FIG. 7 is a cross-sectional view and a plan view of another embodiment of the microwave circuit of the present invention.

FIG. 8 is a graph showing the dependence of the no-load Q value on the height of the support base.

FIG. 9 is a graph showing the dependency of the external Q value on the height of the support base, comparing the microwave circuit of the present invention with a conventional microwave circuit.

FIG. 10 is a perspective view and a cross-sectional view of an example of a conventional microwave circuit.

FIG. 11 is a perspective view and a sectional view of another example of a conventional microwave circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ground conductor 2 semiconductor substrate 3 center conductor 4 dielectric resonator 6, 6 a, 6 b support 7 insulating film 12 MIM capacitor 15 matching open stub 16 return line 17 波長 wavelength line 18 gate electrode 19 drain electrode 20 source Electrode 21 Active layer 22 Insulating substrate 23 Metal block 24 Chip capacitor 25 FET chip 26 Gold wire 27 Adjustment screw 28 Shield case 29 Hollow part

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01P 7/10 H03B 5/18

Claims (6)

(57) [Claims] 1. A microwave circuit in which a dielectric resonator is magnetically coupled to a microstrip line, wherein a surface of a substrate constituting a part of the microstrip line is larger than a bottom surface of the dielectric resonator. Have a surface
That through the support base to fix the dielectric resonators, and the surface portion protruding center conductor forming a part relative to the support base of the dielectric resonator of the microstrip line <br/> And a microwave circuit formed on each of the surfaces of the substrate. 2. The microwave circuit according to claim 1, wherein said support base is formed by etching said substrate. 3. The apparatus according to claim 1, wherein the support is formed of an insulating film deposited on the substrate.
The microwave circuit as described. 4. The microwave circuit according to claim 1, wherein said center conductor is connected to a transistor to form a monolithic integrated circuit. 5. The substrate on which the support base is formed is at least a feedback line connected to the center conductor and an insulating substrate having a capacitor formed on a surface thereof, and the center conductor is connected to a transistor chip. 2. The microwave circuit according to claim 1, wherein the microwave circuit is connected via a line to form a hybrid integrated circuit. 6. The microwave circuit according to claim 1, wherein a part of a joining portion of the support table with the dielectric resonator is a hollow portion. .