JPS6364081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transistor for high frequency, high power amplification with impedance matching.

High frequency high power transistor is bipolar type,
For both FET types, high output is achieved by connecting multiple unit transistors in parallel, and as the frequency and output are increased, the input and output impedance of the element decreases. For this reason, traditionally,
A so-called internal matching circuit is used in the element container, which consists of a MOS chip capacitor, inductance by bonding wire, microstrip line, etc., and this allows the impedance of the external line to be 50Ω. Impedance conversion is being performed to bring it closer. However, this internal matching circuit is not only used to bring the impedance closer to the external line impedance to facilitate external impedance matching, but also to enable impedance conversion close to the transistor chip. Therefore, it is possible to prevent the relatively large inductance of the bonding wire connecting the transistor chip and the device container, which occurs when an internal matching circuit is not used, from increasing the operating Q of the device and thereby narrowing the frequency band. For this reason, an internal matching circuit is essential for devices that require wide frequency band characteristics, and in the 2GHz to 4GHz band, bipolar transistors without an internal matching circuit have several
Although it was possible to achieve only a 10MHz band, by providing an internal matching circuit, it is possible to achieve several times as wide band characteristics. Internal matching circuits commonly used in the past generally consist of a T-type circuit in which a chip capacitor is connected in parallel to a series inductance formed by a bonding wire, or a multi-stage circuit formed by subsequent connections thereof, and are in the form of a low-pass filter. Therefore, if the impedance of the transistor chip is a resistance component, it is possible to widen the band as described above, but if the grounding inductance due to grounding bonding wires, parasitic elements in the device container, etc. cannot be ignored, Input impedance becomes inductive. In such a case, the transistor chip itself has a considerably large operating Q value, and with a conventional low-pass type internal matching circuit, it is impossible to lower this operating Q value, and there is a limit to widening the band. The effect of grounding inductance becomes more pronounced as the frequency increases, so at high frequencies above 4GHz,
It is difficult to achieve frequency band characteristics wider than about 10% of the operating frequency using conventional internal matching circuits.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-frequency, high-output transistor having an internal matching circuit that can solve the above-mentioned drawbacks of the conventional internal matching circuit and significantly expand the limit of the frequency band.

According to the present invention, chip capacitors for internal matching circuits can be connected not only in parallel as a low-pass type but also in series. In this way, the inductive impedance component of the transistor chip is canceled out by the capacitance connected in series,
The limits of the frequency band can be greatly expanded.

The invention will now be described in more detail with reference to the following passages so that the principles and features of the invention may be better understood.

First of all, Figure 1 shows the conventional 2
This is an example of a stepped internal matching circuit, in which the resistance component 1 of a transistor chip and the ground inductance component 2 are internal matching circuit elements, including inductances 3 and 4 by bonding wires, capacitances 5 and 6 by chip capacitors, and capacitances 5 and 6 by chip capacitors. The inductance 7 of the bonding wire for connecting the capacitor 6 and the input lead of the element, and the microstripline component 8 generated from the input terminal metallization of the element container are connected to perform impedance conversion. According to this method, the bandwidth BW is approximately expressed by the following formula. That is, BWR ₁ /WL ₂ +WL ₃ where R ₁ is the resistance component of the transistor chip, WL ₂ is the reactance component of the transistor chip, and WL ₃ is the reactance component due to the bonding wire.

Therefore, in this circuit type, the only internal matching circuit element for increasing the bandwidth is to make the inductance component _L3 of the bonding line as small as possible, which naturally has a limit.

FIG. 2 shows an example of a high frequency output/output transistor using a chip capacitor for an internal matching circuit according to the present invention. In addition to the capacitance 5 connected in parallel, there is also a capacitance 9 connected in series, An inductance 10 is provided. By selecting the impedance value of the inductance 10 to be relatively large compared to the impedance value of the capacitance 9 so that it acts as a chiyoke coil,
Since the capacitance 9 can cancel out the ground inductance component 2 of the transistor chip and the inductance 3 of the bonding wire, the circuit operation Q can be freely selected by selecting the value of the capacitance 9, which is different from the conventional Significant broadband characteristics can be achieved compared to conventional circuits.

FIG. 3 shows the structure of a MOS type chip capacitor used in this circuit, with FIG. 3a showing a sectional view and FIG. 3b showing a plan view.

A dielectric 12 such as silicon dioxide is formed on a silicon substrate 11 with a high impurity concentration, an electrode metal 13 is formed thereon, and another electrode metal 15 is further formed with a dielectric 14 interposed therebetween.

Further, FIG. 4 shows an example in which the above-mentioned chip capacitor is formed of ceramic, in which a surface electrode metal 13 is formed on a high dielectric ceramic substrate 17 having a back electrode 16, and other metals are placed on top of it via a dielectric 14. The electrode metal 15 is formed.

FIG. 5 shows an embodiment of a high frequency, high power transistor having an internal matching circuit according to the present invention. Figure A shows a sectional view, and Figure B shows a plan view. Ceramic substrate 18 such as beryllia with good thermal conductivity
has metallization 19 on the back and sides,
This will serve as the ground electrode. The metallization 19 is also applied on the surface and surrounds the collector metallization portion 21, which is the mounting portion of the transistor chip 20, in an insulated manner. A chip capacitor 22 and a chip yoke coil board 2 forming the inductance shown in FIG.
3 is also mounted on the ground metallization 19, and each part is bonded wire, 24, 25, 26, 27,
28. bonding wire 24
connects the collector metallized portion and the output lead metallized portion 29, and the wire 25 connects the connection electrode of the transistor chip to the grounded metallized portion 19 of the element container, and most of the grounding inductance in FIG. 2 is due to the inductance due to this bonding wire. arise. The wire 26 is connected to the input electrode of the transistor chip and the electrode 15 of the chip capacitor.
, resulting in an inductance of 3. wire 2
7 connects the electrode 13 of the chip capacitor and the input lead metallization 30 to generate an inductance 4. Furthermore, the wire 28 connects the coil substrate 23 in parallel between the surface electrodes of the chip capacitor, and is used to form a large inductance 10 as a chain yoke. With the above configuration, a broadband high-frequency, high-output transistor can be realized, but in order to further increase the bandwidth, it is also possible to configure an equivalent circuit as shown in FIG. 6.

The part surrounded by broken lines in Figure 6 is composed of a single chip capacitor.
A cross-sectional view of a MOS type chip capacitor is shown in FIG. The same applies to the ceramic type, which has a structure in which the electrode 15 protrudes outward from the region of the lower electrode 13, and the capacitance 31 is formed by that portion.

FIG. 8 shows the band characteristics of these internal matching circuits in the 4 GHz band, and is the result of theoretical calculation assuming that the impedance of the transistor chip is an inductive impedance of 1.5+j8. curve 32
is the conventional case, curve 33 is the equivalent circuit according to the present invention shown in FIG. 2, and curve 34 is the equivalent circuit shown in FIG. 6 which has a wider band, and a significant improvement can be seen.

In this example, a bipolar transistor was explained, but it is clear that a FET has the same effect, and in order to adjust the chip capacitor electrode pattern b, it is actually more convenient to use multiple electrodes. In addition, the coil board as a base is several nH above 4GHz.
Since the above is possible, it is possible to replace the bonding wire by wiring it in a loop using metallization on a suitable island, but this does not limit the present invention.

[Brief explanation of drawings]

Figure 1 shows an example of an input-side equivalent circuit diagram of a conventional high-frequency, high-output transistor with an internal matching circuit.
FIG. 2 shows an example of an equivalent circuit on the input side of a high-frequency, high-output transistor having an internal matching circuit according to the present invention, and FIG. 3A is a cross-sectional view showing the structure of a MOS type chip capacitor used in the internal matching circuit according to the present invention. 4A is a sectional view showing the structure of a ceramic chip capacitor used in the internal matching circuit according to the present invention. Figure A is a cross-sectional view of an embodiment of a high-frequency, high-power transistor having an internal matching circuit according to the present invention, Figure B is a plan view thereof, and Figure 6 is a cross-sectional view of an embodiment of a high-frequency, high-power transistor having an internal matching circuit according to the present invention. 7 is a sectional view showing the structure of another embodiment of the MOS type chip capacitor used in the internal matching circuit according to the present invention; FIG. FIG. 3 is a characteristic curve diagram showing calculation results showing frequency band characteristics. 1...Resistance component of transistor chip, 2...
Grounding inductance component of transistor chip,
3, 4, 7... Inductance of bonding wire, 5, 6... Capacitance due to capacitor, 9...
...Capacitance, 10...Inductance, 11...
Silicon substrate, 12, 14...Dielectric material, 13, 1
5...Metal for electrode, 16...Back electrode, 17,1
8... Ceramic substrate, 19... Metallization, 2
0...Transistor chip, 21...Collector metallized portion, 22...Chip capacitor, 23...
...Coil board, 24-28...Bonding wire, 29,30...Metallization for lead.

Claims (1)

[Claims] 1. In a high-frequency transistor comprising a transistor element and a low-pass filter type internal matching circuit provided on the input or output electrode side of this element and having a capacitor whose one end is grounded, in the same container, the input or output of the transistor element A capacitance element is connected between the electrode and the other end of the capacitor, an inductance element functioning as a choke coil is connected in parallel to the capacitance element, and the input or output impedance of the transistor element is The band characteristics are widened by setting the capacitance value of the capacitive element so as to cancel out the inductance component of the capacitor. The capacitive element includes a second electrode formed on the dielectric layer and a second electrode formed on the dielectric layer, with the second electrode of the capacitor as one electrode. A high frequency transistor comprising a dielectric layer and another electrode formed on the dielectric layer.