JPH0528493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor protection device, and particularly to a semiconductor protection device for an integrated circuit using a bipolar transistor as a protection element.

[Conventional technology]

Conventionally, a semiconductor protection device using a bipolar transistor as a protection element has, as shown in the cross-sectional model diagram in FIG. Connection terminal 1
01 and the other to ground potential. The equivalent circuit is shown in FIG. 5, and the voltage/current characteristics seen from the external connection terminal ₁₀₁ in the case of a bipolar transistor that can be formed on a semiconductor integrated circuit with a power supply voltage Vcc of about 5V are shown in FIG.

The holding voltage of the conventional example shown in FIG. 4 is higher than the power supply voltage _Vcc , as shown in FIG. 6, and is about 8V. For example, when used as a protection element for a terminal to which a voltage higher than the holding voltage and lower than the breakdown voltage is supplied, noise etc.
When that terminal becomes higher than the breakdown voltage of 16V and enters the negative resistance region, the voltage supplied to this terminal is higher than the holding voltage, so a large current continues to flow, and eventually the aluminum Wiring may melt or bonding may deteriorate.

[Problem that the invention seeks to solve]

The above-described conventional semiconductor protection device has a drawback that the protection voltage range is narrow because the holding voltage is not very high relative to the power supply voltage.

An object of the present invention is to provide a semiconductor protection device with a wide protection voltage range.

[Means for solving problems]

The semiconductor protection device of the present invention uses, as a protection element, a bipolar transistor consisting of a semiconductor substrate or island-like region of a first conductivity type and two diffusion layer regions of a second conductivity type formed close to each other on the surface thereof. In the semiconductor protection device, one of the diffusion layer regions is connected directly or through a resistor to an external connection terminal, and the other is connected to the power supply voltage and the semiconductor substrate, the island region, or the second conductivity type to be protected. It is connected to a potential between the potential to which the source of the insulated gate field effect transistor is connected.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention.

The embodiment shown in FIG. 1 is achieved by providing two N-type diffusion layer regions 2 on the surface of a P-type semiconductor substrate 1.
An NPN bipolar transistor is formed, one N-type diffusion layer region 2 is connected to the external connection terminal 101, the P-type semiconductor substrate 1 is connected to the ground potential, and the other N-type diffusion layer region 2 is connected to the N-type field effect transistor. It is connected to a power supply voltage terminal 102 that is different from the source potential (usually ground potential) of a transistor (not shown).

Fig. 2 shows its equivalent circuit, and Fig. 3 shows its voltage/current characteristics. In FIG. 3, the broken line a is the characteristic of the embodiment shown in FIG. 1, and the broken line b is the characteristic of the conventional example shown in FIG. 4 (same as the broken line b in FIG. 6).

As shown in FIG. 3, the holding voltage is increased by approximately the power supply voltage _Vcc (5V), and what was 8V in the conventional example shown in FIG. 4 becomes 13V in the embodiment shown in FIG. Also, the voltage and current entering the negative resistance region also increase.

As explained above, the embodiment shown in FIG.
By connecting one side of the N-type diffusion layer region 2 as an NPN transistor to the power supply voltage terminal ₁₀₂ , the holding voltage can be increased. This NPN transistor is used as protection, and even if the potential of this terminal exceeds the breakdown voltage and enters the negative resistance region due to noise, etc., if the voltage of that terminal returns to its original state, it will be lower than the holding voltage, so The current does not continue to flow, and the protection element will not be destroyed due to melting of the aluminum wiring or deterioration of the bond.

In the embodiment shown in FIG. 1, the potential of one side of the N-type diffusion region 2 is set to the power supply voltage _Vcc ;
It is sufficient that the potential here is higher than the potential of the P-type semiconductor substrate 1 (or the source potential of the N-type field effect transistor), and the higher the potential, the higher the holding voltage becomes.

In addition, the external connection terminal 1 in the embodiment shown in FIG.
A similar effect can be obtained by providing a resistor between 01 and one of the N type diffusion layer regions 2 connected thereto.

Although the embodiments of the present invention have been described above with respect to the case where a P-type substrate is used, the same applies to the case where an N-type diffusion layer is formed in the P-well region.

〔Effect of the invention〕

As explained in detail above, the semiconductor protection device of the present invention can protect one of the two diffusion layer regions of a conductivity type different from the semiconductor substrate or the island region from the semiconductor substrate or the island region or (the same conductivity type as the diffusion layer region). By connecting to a potential different from the potential to which the source of the field effect transistor is connected, the holding voltage can be increased without adding any steps to the manufacturing process, and the protection voltage range can therefore be widened. There is an effect.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional model diagram showing one embodiment of the semiconductor protection device of the present invention, Figs. 2 and 3 are a circuit diagram and a graph showing voltage/current characteristics of the embodiment shown in Fig. 1, and Fig. 4 5 is a cross-sectional model diagram showing an example of a conventional semiconductor protection device, and FIGS. 5 and 6 are a circuit diagram and a graph showing voltage/current characteristics of the conventional example shown in FIG. 4. DESCRIPTION OF SYMBOLS 1... P-type semiconductor substrate, 2... N-type diffusion layer region, 101... External connection terminal, 102... Power supply voltage terminal.

Claims (1)

[Claims] 1. A bipolar transistor consisting of a semiconductor substrate or island region of a first conductivity type and two diffusion layer regions of a second conductivity type formed close to each other on the surface thereof is used as a protection element. In the semiconductor protection device, one of the diffusion layer regions is connected to an external connection terminal directly or through a resistor, and the other is connected to a power supply voltage and the semiconductor substrate, the island region, or the second region to be protected.
A semiconductor protection device characterized in that the source of an insulated gate field effect transistor of conductivity type is connected to a potential between that and the potential to which it is connected.