JPH07106811A - High-frequency circuit - Google Patents

Abstract

PURPOSE:To make the size of the high-frequency circuit module small. CONSTITUTION:A glass ceramic including alumina or barium is employed for a material of a multi-layer board. The multi-layer board is structured by four layer flat plates 1-4 whose thickness is 150mum and whose side is 7mm each and the layers are interconnected by a throughhole 12. The front side 15 of the 1st layer is provided with a high dielectric substance incorporating GaAs- MMIC 11, a chip component 13 and a microstrip line 25. A ground conductor 14 is arranged to almost the entire face of the front side 16 of the 2nd layer and the front side 18 of the 4th layer. A conductor line 21 being a strip line is arranged to the front side 17 of the 3rd layer and the respective conductor lines 21 are separated by a ground conductor 22. A bias resistor being a printed resistive element is formed to the rear side 19 of the 4th layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency circuit including a semiconductor element used in various communication devices.

[0002]

2. Description of the Related Art In recent years, information communication plays an extremely important role, and the demand for mobile communication systems is rapidly increasing. Under such circumstances, in mobile phones and cordless phones, miniaturization of high-frequency circuits used is becoming extremely important due to the demand for miniaturization of systems.
Conventionally, a module using an active element and a passive element, such as a high frequency semiconductor element such as a silicon bipolar transistor, a gallium arsenide field effect transistor or MOSFET, has been used by taking advantage of its excellent high frequency characteristics.

FIG. 3 shows a high-power amplifier as an example of a conventional high-frequency circuit module. This module has a size of 12 × 17 mm and is composed of a semiconductor element 31, a chip component 13, a strip line 32, a terminal 34, a conductor line 35, and the like provided on an alumina ceramic substrate 33. A high output field effect transistor (FET) using GaAs, for example, is used as the semiconductor element 31, and an impedance matching circuit, for example, is provided as the chip component 13 before and after the FET that is the semiconductor element 31.

The bias point of the FET, which is the semiconductor element 31, is determined by the required operating current, operating voltage, and distortion characteristics. Further, in order to attenuate the second harmonic, the length of the open end is set to the above-mentioned F
It is used as the ET drain bias line. Since the conductor line 35 is as long as a quarter of the wavelength in the line, it poses a serious problem in miniaturizing the module. Further, since the conductor line 35 has a long line length, it is likely to be electromagnetically coupled to other lines, causing a problem such as oscillation.

[0005]

As described above, in the conventional module, the chip component 13 which is the impedance matching circuit and the conductor line 35 which is the bias circuit occupy a large area. These are a chip capacitor, a chip resistor, and an inductance, and the size of the module can be reduced by reducing the area occupied by them.

With regard to the chip capacitor, by incorporating the capacitor in an integrated circuit, it is possible to expect a great reduction in size. However, since a dielectric such as a silicon nitride film or a silicon oxide film that has been conventionally used to form a capacitor on a semiconductor substrate has a small dielectric constant (less than 7), the ratio of the capacitor to the chip area is small. A capacitor having a large capacitance value, such as a bypass capacitor, has become very large, and it has been difficult to integrate the capacitor with the conventional configuration.

Since the chip resistance needs to be adjusted according to the required operating characteristics, it cannot be built in the semiconductor element, which hinders miniaturization. Further, when a filter composed of a conductor line and an inductance whose opening length is 1/4 of the wavelength in the line is formed on the semiconductor substrate,
It has a large proportion in the chip area, and the conductor line formed on the semiconductor substrate has a large wiring resistance, so that the Q value is low, and since it is adjacent to another conductor line, electromagnetic coupling occurs. There was a problem that it was easy. Further, when a plurality of conductor lines are arranged adjacent to each other on or inside a module substrate in order to integrate circuits at high density, they are electromagnetically coupled to each other, causing problems such as oscillation.

An object of the present invention is to provide a high frequency circuit which can be miniaturized.

[0009]

In order to solve the above-mentioned problems, a high-frequency circuit according to a first aspect of the present invention is a multi-layer substrate in which two or more flat plates containing alumina or barium are stacked, an active element, and barium titanate and titanium. A semiconductor substrate provided with an integrated circuit including a capacitive element (for example, a bypass capacitor or a coupling capacitor) having a high dielectric thin film made of a mixed crystal thin film of strontium acid as a capacitive insulating film, and placed on the main surface of a multilayer substrate; It has a configuration with.

A multilayer substrate containing alumina is characterized by its good thermal conductivity and low dielectric loss tangent, and is suitable for applications such as high-power power amplifiers. Further, the substrate containing barium has a characteristic that the dielectric constant is high. When a low-temperature fired substrate is used as the multi-layer substrate, the low-temperature fired substrate has a low firing temperature, so that a conductive material having a low melting point such as Cu or Ag can be used.

A high frequency circuit according to a second aspect of the present invention is the high frequency circuit according to the first aspect, wherein a printed resistance element is formed of, for example, RuO _{2 on} the opposite main surface of the multilayer substrate. This is because the resistance value for adjusting the operating current of the semiconductor can be changed by cutting a part of the printed resistance element by laser irradiation. Further, the printed resistance element is formed on the opposite main surface of the multi-layer substrate in order to prevent the semiconductor substrate and the wire provided on the one main surface of the multi-layer substrate from heat and scattered substances generated during laser irradiation.

A high frequency circuit according to a third aspect of the present invention is the high frequency circuit according to the first aspect, in which two or more conductor lines are formed on the surface of one flat plate constituting the multilayer substrate, and conductors on the surface of the single flat plate are formed. A ground metal conductor is formed between the lines, and a ground conductor layer is formed on almost the entire surface of the other flat plate above and below the flat plate. In the high frequency circuit according to the fourth aspect of the present invention, the filter is formed on the surface of one flat plate that constitutes the multilayer substrate, and the ground conductor layer is formed on almost the entire other upper and lower flat plates that sandwich the single flat plate.

[0013]

According to the structure of claim 1, instead of the silicon oxide film which has been conventionally used as the insulating film for forming a capacitor,
For example, by using a compound of barium titanate and strontium titanate (BSTO) having a dielectric constant of 300, the area occupied by the capacitor can be reduced to 1/50 at the same film pressure, and as a result, the chip area can be significantly reduced. .

As the material of the multi-layer substrate, a low temperature firing substrate containing alumina or barium is used. Since the firing temperature is low, a conductive material having a low melting point such as Cu or Ag is used. You can Since Cu and Ag have extremely high electric conductivity, a circuit with little loss can be formed. According to the configurations of claims 2 to 4, by using the multilayer substrate of claim 1, the printed resistance element is disposed on the opposite main surface of the multilayer substrate, and the conductor line and the filter are disposed on the inner layer of the multilayer substrate. The module can be miniaturized.

Particularly, the conductor line and the filter are installed on the inner layer of the multilayer substrate and sandwiched between the flat plates on which the ground conductor layer is formed on almost the entire surface, so that the area occupied by the module can be reduced and It is possible to block the influence of the electromagnetic field from the outside. By thus blocking the influence of electromagnetic fields, it is possible to improve the stability of the pass frequency of the filter and the Q value, for example.

Further, by arranging a printed resistance element as a bias resistance on the back surface, for example, the trimming is carried out by laser trimming for resistance adjustment, and the printed resistance element is arranged on the main surface of the multilayer substrate from heat and scattered substances generated when the printed resistance element is scraped. It is possible to prevent the semiconductor substrate (IC chip) and the wires from being adversely affected. Also, when there are multiple conductor lines in the inner layer,
Since the ground metal conductor is installed between the conductor lines, the coupling between the conductor lines can be prevented.

Further, according to the present invention, by implementing the above configuration, the high frequency circuit can be downsized to about 25% of the size of the conventional example.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a high output amplifier using a multilayer substrate as a high frequency circuit according to the first embodiment of the present invention. The alumina substrate used as a flat plate constituting the multilayer substrate in this circuit is a plate of 97% alumina fired at 1600 degrees and has a thickness of 150 μm.
The size is 7 mm square. This alumina substrate has a characteristic that the thermal conductivity is extremely excellent. Four flat plates 1 made of this alumina substrate (ceramics firing substrate)
4 are used to form a multilayer substrate by laminating these layers, and the layers are connected by through holes 12.

The high output amplifier as the high frequency circuit is
G composed of 3 FETs, high-dielectric coupling capacitor, resistor and high-dielectric bypass capacitor
aAs-MMIC (monolithic microwave IC),
It has a hybrid structure with an input / output matching circuit composed of chip parts. This high power amplifier
On the surface of the flat plate 1, that is, on the surface 15 of the first layer, a GaAs-MMIC 11 with a built-in high dielectric material, a chip component 13 such as a chip capacitor and a chip resistor, and a microstrip line 2 are provided.
5 are arranged. That is, on the surface 15 of the first layer, there are arranged semiconductor elements which are indispensable to thermally dissipate heat, matching circuits which require adjustment, and the like.

On the surfaces of the flat plates 2 and 4, that is, the second layer surface 16 and the fourth layer surface 18, a ground conductor layer (W; tungsten) 14 having a thickness of 18 μm was disposed over almost the entire surface. Furthermore, the surface of the flat plate 3, that is, the third layer surface 1
In FIG. 7, two conductor lines 21 each having a bias power supply line and a termination open length of 1/4 of an in-line wavelength using a strip line having a thickness of 18 μm and a width of 200 μm are arranged.
The second layer surface 16 and the fourth layer surface 18 are formed between the conductor lines 21 and 21 by through holes having a diameter of 100 μm.
Are separated by ground conductors (ground lines) 22 connected to the ground conductor layers 14 of FIG. As a result, the plurality of conductor lines 21 and 21 can be arranged adjacent to each other without worrying about electromagnetic coupling. Further, in the vertical direction, since the structure is sandwiched between the ground conductor layer 14 of the second layer surface 16 and the fourth layer surface 18, it is electromagnetically shielded from the outside and unnecessary coupling at high frequency is prevented. It is blocking. Further, the conductor line 21 formed of a strip line has an advantage that the circuit is downsized due to the wavelength shortening effect as compared with the microstrip line 25 formed on the first layer surface 15.

On the back surface of the flat plate 4, that is, the back surface 19 of the fourth layer, a bias resistor is formed by a printed resistance element (made of RuO ₂ ). This bias resistor can adjust the operation of the circuit by trimming part of it with a laser while monitoring the operating current when the circuit is actually operated. By centrally arranging the printed resistance elements on the back surface, it is possible to prevent the IC, the die bonding pad of the IC, the wire 20 and the like from being affected by heat or scattered substances generated during the trimming by the laser.

With the above structure, the area can be reduced to about 25% of the conventional module. In this embodiment, a GaAs IC with a built-in high dielectric material is used, but a circuit having a similar structure can be formed using a semiconductor other than GaAs with a built-in high dielectric material, for example, another semiconductor such as Si.

In this embodiment, a high temperature sintered substrate of 97% alumina is used, but it contains alumina and Ba or Mg.
A circuit having a similar structure can be formed by using a low temperature baking substrate containing Zn, Zn, Zr, or the like. Such a low-temperature fired substrate has a feature that a material such as Ag or Cu having a high conductivity and a low coefficient of thermal expansion can be used as a conductor. FIG. 2 shows a small signal amplifier for a mobile phone using a glass ceramic multilayer substrate as a high frequency circuit according to the second embodiment of the present invention.

The substrate used as a flat plate constituting a multi-layer substrate in this circuit is a glass composite material containing barium which is fired at 800 ° C. at a low temperature to have a thickness of 150 μm and a length and width of 10 m.
m. Since this substrate is a ceramic with a small coefficient of thermal expansion, a thick film resistor can be formed on the surface layer, and since it is fired at a lower temperature than an alumina substrate, it is possible to use a wiring material (Ag, Cu) with a low electrical conductivity, etc. It has the characteristics of.
In this embodiment, a multi-layer substrate using four substrates is used.

In this embodiment, the glass composite material containing barium is fired at a low temperature of 800 degrees to form four flat plates 1 '.
4'are used to form a multilayer substrate by laminating these layers, and the layers are connected by through holes 12. In this small signal amplifier for mobile phones, a GaAs-MMIC 11 with a built-in high dielectric material, a chip component 13 'such as a chip capacitor and a chip resistor, and a microstrip line 25 are arranged on the surface of the flat plate 1', that is, the first layer surface 15 '. And forms the main part of this circuit.

In other words, semiconductor parts which are indispensable for heat dissipation, matching circuits which need adjustment, etc. are on the surface 15 'of the first layer.
It is located in. In addition, the ground conductor layer 14 is disposed almost all over the surfaces of the flat plates 2'and 4 ', that is, the second layer surface 16' and the fourth layer surface 17 '. Further, on the surface of the flat plate 3 ', that is, the surface 17 of the third layer, the length is 8
Two filters with one-half short-circuited parallel conductor lines 2
3, 23 are arranged, and the respective filters 23,
Between 23, the second layer surface 16 is formed by the through hole 12.
It is separated by a ground conductor (ground line) 24 connected to the ground conductor layer 14 on the surface 18 of the fourth layer. In the vertical direction, since the structure is sandwiched between the ground conductor layers 14 and 14 on the second layer surface 16 and the fourth layer surface 18, it is electromagnetically shielded from the outside to prevent unnecessary coupling at high frequency. It is blocking. Further, the strip line that constitutes the filter 23 has an advantage that the circuit is downsized due to the wavelength shortening effect as compared with the microstrip line 25 installed on the first layer surface 15.

With the above structure, the area can be reduced to about 25% of the conventional module. Further, in this embodiment, a GaAs IC with a built-in high dielectric material is used.
However, a circuit having a similar structure can be formed by using a semiconductor other than GaAs with a built-in high dielectric such as another semiconductor such as Si. In this embodiment, as the filter 23, a terminating short-circuited parallel conductor line having a length of ⅛ of the line wavelength is used. A terminal short-circuited conductor line having a length of ¼ of the line wavelength, an open-ended conductor line having a length of ½ of the line wavelength, a terminal short-circuited conductor line having a length of ½ of the line wavelength,
A parallel conductor line with an open end having a length of ⅜ of the line wavelength, a so-called step impedance type filter in which conductor lines having different widths are combined, a direct coupling type filter having a structure in which the conductor lines are disconnected, and a distributed coupling type bandpass filter. A so-called hybrid ring type filter in which a conductor straight line having a quarter of the line wavelength is formed in a ring shape, a rat race type filter, or a configuration in which the line in which the conductor line is replaced with a slot line is used alone or in parallel Excellent properties are obtained.

In this embodiment, a glass-ceramic low-temperature fired substrate containing barium is used, but a low-temperature fired substrate containing alumina or the like can be used to form a circuit having a similar structure. As the multilayer substrate, it is preferable to use a multilayer substrate containing alumina for a circuit that emits high heat such as a high-power amplifier and a low-temperature firing substrate for a circuit in which loss is important, depending on its use.

[0029]

According to the high frequency circuit of the first aspect, by using the compound of barium titanate and strontium titanate, the area occupied by the capacitor is reduced to 1/50 at the same film pressure, and as a result, the chip area is reduced. Can be significantly reduced. According to the high frequency circuit according to any one of claims 2 to 4, the printed resistance element is arranged on the opposite main surface of the multilayer substrate, and the conductor line (strip line) or the filter is arranged on the inner layer of the multilayer substrate, thereby miniaturizing the module. can do.

In particular, if the conductor line and the filter are installed on the inner layer of the multilayer substrate and sandwiched between the flat plates on which the ground conductor layer is formed on almost the entire surface, the area occupied by the module can be reduced, and It is possible to block from the influence of electromagnetic fields from the outside, and by blocking the influence of electromagnetic fields, the stability of the pass frequency of the filter and Q
The value can be improved.

If a printed resistance element is arranged on the back surface,
It is possible to prevent the semiconductor substrate (IC chip) and the wires arranged on the main surface of the multilayer substrate from being adversely affected by heat and scattered substances generated when the printed resistance element is cut by laser trimming for resistance adjustment. Further, when there are a plurality of conductor lines in the inner layer, a ground conductor may be installed between the conductor lines to prevent coupling between the conductor lines.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a multilayer substrate according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a structure of a multi-layer substrate according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a module in a conventional example.

[Explanation of symbols]

 1 to 4 flat plate 11 GaAs-MMIC with built-in high dielectric material 12 through hole 13 chip component 14 ground conductor 15 first layer surface 16 second layer surface 17 third layer surface 18 fourth layer surface 19 fourth layer back surface 20 wire 21 conductor Line 22 Ground conductor 23 Conductor line 24 Ground conductor 25 Microstrip line

Claims (4)

[Claims] 1. A flat plate containing alumina or barium
A semiconductor provided on one main surface of the multi-layer substrate in which an integrated circuit including a multi-layer substrate in which one or more sheets are stacked, and a capacitive element having an active element and a mixed crystal thin film of barium titanate and strontium titanate as a capacitive insulating film is formed High frequency circuit with a substrate. 2. The high frequency circuit according to claim 1, wherein a printed resistance element is formed on the opposite main surface of the multilayer substrate. 3. A single flat plate constituting a multi-layer substrate is provided with 2 on the surface thereof.
Two or more conductor lines are formed, a ground metal conductor is formed between the conductor lines on the surface of the one flat plate, and a ground conductor layer is formed on almost the entire upper and lower flat plates sandwiching the one flat plate. The high frequency circuit according to claim 1, which is formed. 4. A filter is formed on the surface of one flat plate constituting a multilayer substrate, and a ground conductor layer is formed on almost the entire surface of another flat plate above and below the flat plate.
The described high-frequency circuit.