JPS622773Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency, high power semiconductor device, and particularly to an improvement of an emitter bridge of a semiconductor device in which transistor elements are connected and housed in parallel in a package.

In high frequency, high output transistors, an external resistor is generally inserted into the emitter for bias stabilization and transistor protection.
For this reason, the emitter of the transistor cannot be directly grounded to the package, so the emitter electrode is led out of the package via a fin.

Conventional high-frequency, high-output transistors, which have multiple transistor elements connected and housed in parallel in a package, consist of an emitter bridge floating in the air between two emitter fins attached to an insulating substrate such as beryllia porcelain fixed on a heat sink. A connection line led out from each emitter of a plurality of transistor elements provided on an insulating substrate was connected to the emitter bridge. In such conventional devices, a large parasitic inductance occurs in the emitter bridge floating in the air, which reduces the high frequency gain.Also, in high-power transistors, the number of transistor elements is large and the length of the emitter bridge becomes long. The parasitic inductance seen from each point toward the ground side is maximum at the center of the emitter bridge and decreases as it moves toward both ends, resulting in uneven distribution of high-frequency power, resulting in unstable operation and a drop in saturated output.

In order to improve this drawback, as shown in FIG. 1, an insulating substrate 2' is provided on a metal heat sink 1', and a protruding base 3 of the heat sink 1' is exposed on the insulating substrate 2'. One electrode side (semiconductor side) of a MIS type capacitor 4' with a thin insulating film as a dielectric material is fixed on the top of the capacitor 4', and the emitter electrode 7' of each transistor element 6' is connected to the other electrode 5' side. Further, both ends of the other electrode 5' of the capacitor are connected to the emitter pins 8' and 9', and a bypass capacitor having a large capacitance is connected between the emitter of each transistor and the ground, so that the strip electrode That is, there is a semiconductor device in which the parasitic inductance of an emitter bridge can be ignored. However, this semiconductor device, for example
It operates smoothly up to a frequency range of about 400 [MHz], but for example 700 [MHz] or 800 [MHz]
Hz], the parasitic inductance of the emitter fin cannot be ignored. In other words, if such a parasitic inductance is connected to both ends of the emitter bridge, a point of impedance discontinuity will occur on the emitter bridge, and the impedance seen from each connection point of the emitter bridge to the ground side will not be uniform, so high frequency This has the disadvantage that power is not evenly distributed.

The present invention is a novel invention that improves the above-mentioned drawbacks, and its purpose is to obtain a semiconductor device having an emitter bridge that reduces and uniformizes the impedance of each transistor element when looking at the ground side.

Examples will be described in detail below.

As shown in FIGS. 2 and 3, a protruding base 2 is provided on a metal base 1 constituting a heat sink, which is made of a metal with good thermal conductivity such as copper (Cu). An insulator substrate 4 made of beryllia porcelain or the like is disposed on the metal base 1, and is provided with a hole 3 through which the protruding base 2 passes.
Attach the collector fins 5, base fins 6, and emitter fins 7 and 8. A pellet 9 having a plurality of transistor elements is fixed to the upper surface of the collector fin 5. An MIS type capacitor 10 is fixed onto the protruding base 2, which is the grounding portion of the package, by grounding its first electrode to the protruding base 2. Each tip of the connection line 14 led out from the emitter of each transistor element is connected to the band-shaped electrode 13, which is the second electrode of the MIS type capacitor 10, at the shortest distance. Both ends 13 of the strip electrode 13
a and 13b are connected to emitter fins 7 and 8 through connection lines 15 and 16, respectively. Therefore,
The strip electrode 13 is one electrode of the capacitor 10 and also constitutes an emitter bridge.

Next, to explain in detail the structure of the MIS type capacitor 10 used in the present invention, as shown in FIG. 4, a thin film 111 of silicon dioxide (SiO ₂ ) is provided on a semiconductor substrate 100 made of silicon, etc. An electrode 13 is provided, and a capacitor is formed between the semiconductor substrate 100 constituting the first electrode and the band-shaped electrode, that is, the emitter bridge 13 constituting the second electrode, using the thin film 111 as a dielectric. Strip lines 113 and 114 with one end open are connected to both ends 13a and 13b of the emitter bridge 13. And the stripline 11
No. 3,114 has a width and length that makes it capacitive in the frequency band in which it is used. By connecting such a capacitive stripline to both ends of the emitter bridge, the parasitic impedance on the emitter bridge can be canceled.
Moreover, the impedance seen from both ends 13a, b of the emitter bridge 13 toward the ground side becomes capacitive in the frequency band used. As a result, the impedance seen from each point on the emitter bridge toward the ground becomes uniform and has a small negative reactance component, allowing each transistor element to operate stably.

Next, in the emittab bridge of the above embodiment,
The length of the emitsuta bridge is 8 [mm] and the width is 2 [mm]
A strip line with a width and length of 2 mm is connected to both ends of the emitter bridge, and an emitter fin with an inductance of about 1 nH is connected to both ends of the emitter bridge. The impedance value is -j0.55 [Ω] at 400 [MHz], 700
It was -j0.24 [Ω] at [MHz] and -j0.20 [Ω] at 800 [MHz], and was constant regardless of the position on the emitter bridge. The thickness of the silicon dioxide (SiO ₂ ) thin film 111 is 1 [μm], and its dielectric constant is 4.0.

As explained above, in the present invention, a strip line with one end open that is capacitive in the frequency band used is connected to both ends of the emitter bridge, so that the impedance seen from each point of the emitter bridge toward the ground side becomes uniform and low. High frequency power is evenly distributed to each transistor element, and it is expected that the saturation output of the semiconductor device will increase and instability will be eliminated.

Incidentally, if the length of the stripline connected to the emitter bridge is long, the tip may be bent as shown in FIG. Further, in order to widen the band of the transistor amplifier, the capacitor 20 inserted into the base side can be arranged in parallel on the thin film of the capacitor forming the emitter bridge.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a conventional semiconductor device, Figs. 2 to 5 are views showing an embodiment of the present invention, Fig. 2 is a sectional view, Fig. 3 is a perspective view, and Fig. 4 is a capacitor. FIG. 5 is an enlarged perspective view showing another embodiment of the capacitor. In the figure, 1 is a metal base, 2 is a protruding base, and 7
9 is an emitter fin, 9 is a pellet, 10 is an MIS type capacitor, 13 is a band-shaped emitter bridge that constitutes the second electrode, 100 is a semiconductor substrate that constitutes the first electrode, 111 is a dielectric thin film, 113,
114 indicates a stripline.

Claims (1)

[Scope of utility model registration request] A metal base constituting a heat sink, an MIS type capacitor disposed on the metal base with a first electrode grounded to the metal base, and an emitter commonly connected to a second electrode of the MIS type capacitor. It comprises a plurality of transistor elements and an emitter fin connected to the second electrode of the MIS type capacitor, and an open-ended strip line is disposed at the end of the second electrode of the MIS type capacitor. A semiconductor device characterized by: