JPS60257174A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve device capabilities to withstand external surges by a method wherein elements equipped with inductance is inserted between IGFET gate electrodes and a gate-protecting diode. CONSTITUTION:Diodes 25, 26, connected in contactenation reverse to each other, are provided between the gate 22 and source 21 and between the gate 23 and source 21, respectively, of an FET20, provided with a source terminal 21, gate terminals 22, 23, drain terminal 24. Further, between a protecting diode and gate electrodes located on a gate oxide film, inductors 27, 28 are connected, respectively. The inductors 27, 28 should use Al lines and have an inductance of approximately 3mH. In a device structured as such, external surges are stopped before entering the gate oxide film, which augments the device in terms of its capabilities to withstand breakdown voltages.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor device, and particularly to a semiconductor device including an insulated gate field effect transistor having an MO8 structure.

In recent years, high-frequency field-effect transistors have increasingly finer patterns in order to improve their high-frequency characteristics, such as power gain and noise figure.The MO8Wt structure exhibits excellent high-frequency characteristics, especially in the UH1i' band. Twin-gate field effect transistor (hereinafter referred to as MO8 twin-gate FET)
) is used in the tuner part of televisions, video tape recorders, etc.

It is also widely used in cable TV Chiron converters, etc. And the power gain of this MO8 twin gate FET,
In order to further improve high-frequency characteristics such as noise figure, the gate length is increasingly shortened and the gate oxide film thickness is made thinner.

Generally, the gate electrostatic breakdown strength of MOS FFtT is determined by the gate oxide film having a film thickness of 10 nm when the gate oxide film is a silicon thermal oxide film.
It is said to be IOV per m. This kind of high frequency MO
The gate oxide film of the 8-twin gate F'F'r is usually several tens of nanometers thick, and for example, when the gate oxide film thickness is 60 nm, an electrostatic breakdown strength of only about 60 V can be obtained as shown in FIG.

Therefore, for the conventional MO8 double gate F'F'[', a gate protection diode was provided to protect the gate oxide film.

Figure 2 shows a conventional MO8O8-)F with a protection diode.
It is an equivalent circuit diagram of an example of gT. In FIG. 2, 1 is a source, 2 is a first gate, 3 is a second gate, 4 is a drain, and 5 and 6 are protection diodes connected between the gate and the source.

The protection diodes 5 and 6 consist of a set of two diodes connected in cascade so as to have opposite characteristics, and are connected between the first gate and the source and between the second gate and the source, respectively.

FIG. 3 is a current-voltage characteristic diagram between the gate and source of the MO8 dual-gate FF3T with a protection diode shown in FIG. As shown in FIG. 3, each bias direction exhibits reverse direction characteristics.

Figure 4 shows the actual measured value of the voltage that leads to the breakdown of this conventional MO8 double gate];" Shows similar values.

As mentioned above, when a protection diode is connected between the gate and the source, the electrostatic breakdown strength against the surge power that enters between the first gate and source or between the second gate and source is 1oo~120cm even with a gate oxide film thickness of 5+1 nm. improve. Each protective diode connected here has a reverse breakdown voltage of 15
A capacitance of 0.5 PF is used when the applied voltage is 0.

By the way, MO8FF in Figure 5! When the gate breakdown strength is measured by changing the capacitance value 11 using a gate surge breakdown strength testing device of T, the result is as shown in FIG. 6 (shown by the line), and the slope is smaller. This indicates that the conventional protection diode alone is sufficient to absorb external surge energy, and a portion of it flows toward the gate oxide film. Incidentally, the destruction of only the protection diode has a slope of 1/2 power with respect to the capacitance, as shown in FIG.

(Problems to be Solved by the Invention) The purpose of the present invention is to eliminate the conventional drawback that external surge power is not sufficiently absorbed by the protection diode and a portion flows toward the gate oxide film, thereby destroying the gate oxide film. It is an object of the present invention to provide a semiconductor device including an insulated gate field effect transistor which is improved so as not to cause problems.

(Means for Solving the Problems) According to the present invention, a semiconductor device is obtained in which a circuit element having an inductance component is inserted between a gate protection diode and a gate electrode of an insulated gate field effect transistor.

(Example) Next, details of the present invention will be explained using the drawings.

FIG. 8 is an equivalent circuit diagram of an embodiment of the present invention.

Source terminal 21. First gate terminal 22. Second gate terminal 23. N-channel MO with drain terminal 14
Two sets of cascaded diodes 25 and 26 are connected between the first gate and source and the second gate and source of the 8-twin gate F'E'r 20 so as to have opposite direction characteristics, and a protection diode is further connected. Inductors 27 and 28 are connected between the gate electrode and the gate electrode on the gate oxide pattern, respectively.

To give a specific numerical example, inductors 27 and 28 are made of Al
A wire is used, and its inductance is approximately 3 nH. These inductors 27 and 28 prevent external surge energy from flowing into the gate oxide film of the MOS.
blocked.

FIG. 9 shows the case where the capacitance value is changed according to the actually measured value of the voltage that causes the destruction of the MO8 twin gate pti:'r according to this embodiment. Approximately 1 at 100PF compared to the conventional example shown in Figure 6
00 ■Improved.

In the present invention, an N-channel type has been described, but a P-channel type is also possible. In addition to silicon, Ga
A compound semiconductor material such as As may also be used.

Although the inductor symbol in the equivalent circuit of FIG. 8 is represented by a coil, it goes without saying that it is actually a distributed constant circuit.

(Effect of the invention) As explained above, according to the present invention, MO8 double game) F'
It becomes possible to greatly improve the fracture strength of B'r.

[Brief explanation of drawings]

Fig. 1 is a graph showing the breakdown voltage of MOS, Fig. 26 is a graph showing the conventional MO8 double gate with protection diode) F'Fi
An equivalent circuit diagram of an example of T, FIG. 3 is a graph showing the above-mentioned diode withstand voltage, FIG. 4 is a graph showing the voltage leading to the above-mentioned breakdown, and FIG. 5 is a circuit diagram of a test device for measuring breakdown strength.
FIG. 6 is a graph showing the capacitance characteristics of the breaking strength using the above-mentioned test apparatus, and FIG. 7 is a graph showing the capacitance characteristics of the breaking strength using only diodes. FIG. 8 is an equivalent circuit diagram of one embodiment of the present invention, and FIG. 9 is a graph showing the capacitance characteristics of the breaking strength of this embodiment. 1... Source terminal, 2... First gate terminal, 3... Second gate terminal, 4......
Drain, 5...Protection diode, 6...
...protection diode, 27,28...inductor. Shipi 1: Voltage (V) 1 Figure 3 100 10SII0 115 720 Shipi 1 = Ri-
(V) Figure 4 1 Figure 5 100 300 7000 Capacity (PF) Figure 6 +00 300 7000 Customer volume (PF) Dream 7 Figure 700 300 1000 Volume (P") Figure 9 Figure 8

Claims (1)

[Claims] 1. A semiconductor device including a gate protection diode for preventing gate destruction due to an external surge of an insulated gate of an insulated gate field effect transistor, characterized in that a circuit element having an ance component is inserted therein.