JPH084094B2 - Field effect transistor - Google Patents

Description

The present invention relates to a field effect transistor, and more particularly to the electrode wiring shape of its input portion.

[Prior Art] Conventionally, particularly in a high output field effect transistor, the electrode shape is a comb shape, and the electrode wiring of the input portion is formed in a pattern as shown in the plan view of FIG. That is, in FIG. 3, the gate electrode 1 in which the source electrode 5 and the drain electrode 4 are alternately arranged in the lateral direction with a constant channel interval and the gate electrode busbar is branched on the channel portion is formed into a comb shape. It is provided.
In addition, a lead wire that is drawn at a right angle from the gate electrode busbar
The gate pad 3 is provided via 2, and the gate pad 3
Source pads 6 which are ground electrodes are arranged on both sides of the source pad 6, and the source pads 6 are connected to each other by wiring 8 outside the lower end of the gate pad 3 as shown by the diagonal lines in FIG.

[Problems to be solved by the invention]

Generally, the input impedance of a field effect transistor is the characteristic impedance of the measurement circuit system that is normally used.
Well below Ω, so a matching circuit is inserted between the device and the external measurement circuitry. Although the element and the matching circuit are connected by a gold wire, the phase rotation increases due to the inductance L of the wire as the frequency used increases, and it becomes difficult to achieve matching. Therefore, it is an indispensable condition for high frequency operation to make the wire length as short as possible, but in the case of the conventional pattern, since the source wiring 8 in FIG. When the wire is pulled out, the wire must be arcuate to avoid contact with the wiring 8, and the wire length becomes long. If each source pad is not connected, it is very inconvenient because a check needle must be set for each source in the characteristic check process in the wafer manufacturing process. Therefore, the above-mentioned drawbacks cannot be avoided with the conventional patterns.

[Means for solving problems]

To solve the above problems, the input part pattern of the field effect transistor of the present invention eliminates the conventional connection between source pads that circumscribe the outside of the lower end of the gate pad, and instead replaces the gate lead wire from the gate electrode to the gate pad. Of the gate pad and the upper or lower layer of the gate pad are connected between adjacent source pads by a wiring that crosses the insulating film between the adjacent source pads, and In the area on the opposite side, the source pads are separated from each other.

〔Example〕

 Next, the present invention will be described with reference to examples.

FIG. 1 is a plan view showing an input part pattern according to an embodiment of the present invention. In FIG. 1, the gate electrode 1 has a width W ₁ ,
The gate electrode 3 is led out by the lead electrode 2 having a length l ₁ . The source pads 6 and 6 located on both sides of the gate pad 3 are wired by the wiring 7 so as to cross over the gate pad 3, and the crossover region has a size of a width l ₂ and a length W of a size shown by a hatched portion in the drawing. _{Is 2} .

FIG. 2 is a sectional view taken along the line AA of FIG.
It is shown that the crossover wiring 7 crosses the upper layer of the gate pad 3 with an insulating film having a thickness t, for example, a SiO ₂ film 9 interposed therebetween. As is clear from FIG. 1, according to this source pad connection method, the connection wire length from the gate pad to the external matching circuit can be made as short as possible. Further, the width W ₁ , the length l ₁ , the width l ₂ , the length W ₂ , and the insulating film thickness t of the lead-out wiring 2 are shown in FIG. 1 by appropriately selecting them according to the frequency used. The impedance Z of the element can be made somewhat closer to the characteristic impedance 50Ω of the outer measuring circuit system, and the effect of facilitating matching can be obtained. For example, W ₁ , l ₁ , W ₂ , l ₂ , and t are respectively 15 μm, 60 μm, 50 μm, 2
When 0 μm, 1500 Å, the inductance L of the lead wire described by W ₁ , l ₁ is 0.032 nH, and the standardized impedance (= 40 Ω) at the characteristic impedance of 50 Ω (= 40 GHz)
ωL / 50) is 0.16. Similarly, the capacitance C at the crossover portion is 0.33 pF and the standardized admittance is 2.73. When the element impedance Z shown in FIG. 1 is sufficiently small, for example, when the standardized impedance is set to 0, the real part Re of the standardized impedance is represented by the above L and C as can be easily understood from the conversion operation on the Smith chart. (Z) is ~
It becomes 0.15. In other words, the power reflection coefficient | Γ |
It is considerably improved as | = 1 → | Γ | 0.75. Even if the final matching is performed by an external circuit, the matching operation becomes easier than before.

〔The invention's effect〕

As described above, in the input part pattern shape according to the present invention,
By wiring the source pad so that it crosses over part of the gate electrode lead-out part or part of the gate pad, the length of the wire connecting the gate pad and the external matching circuit can be shortened. The impedance of the element is determined by the inductance L of the section and the capacitance C of the crossover section.
Since it is close to Ω, there is an effect that matching with an external circuit can be easily achieved.

[Brief description of drawings]

1 is a plan view of a pattern of an input section according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 3 is a plan view of an input section pattern of a conventional field effect transistor. Is. 1 ... Gate electrode, 2 ... Gate extraction wiring, 3 ... Gate pad, 4 ... Drain electrode, 5 ... Source electrode,
6 ... Source pad, 7 ... Crossover wiring, 8 ...
... source wiring.

Claims (1)

[Claims] 1. In a field effect transistor having a comb-shaped electrode structure, source pads located on both sides of a gate pad with an insulating film interposed between the gate and the source pad reach the gate pad. Wiring is connected across a part of the lead-out portion or a part of the gate pad above or below, and the source pads are separated from each other in a region of the gate pad opposite to the gate lead-out portion. Field effect transistor characterized by.