JPH0628300B2 - Static electricity protection device for complementary MIS integrated circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrostatic protection device for a complementary MIS integrated circuit, and in particular, a non-conducting MI at steady state used as a protection element.
The present invention relates to an electrostatic protection device for a complementary MIS integrated circuit formed so as to protect an S-transistor gate insulating film.

[Conventional technology]

Conventionally, in this main electrostatic protection device for a complementary MIS integrated circuit, a MIS transistor which is non-conductive at a steady state is used as a protection element, and the gate of the MIS transistor is directly connected to a power supply terminal by a metal wiring. Or, as shown in FIG. 3 as an example circuit diagram,
P-channel M acting as a protection element for internal circuits
Resistors 4-1 and 4-are provided for the IS transistor 1-1 and the N-channel MIS transistor 1-2, respectively.
It is general that two are connected.

[Problems to be solved by the invention]

In the above-described conventional electrostatic protection device for a MIS integrated circuit, for example, when the gate of the MIS transistor used as a protection element is directly connected to the power supply terminal or the like, a high electric field is applied to the gate insulating film when static electricity is applied. In addition, the insulating film may be destroyed. In particular, there is a drawback that the risk is further increased as the gate insulating film of the MIS transistor is made thinner. Also, the third
As shown in the figure, the method of connecting resistors has a drawback in that it is not easy to set the resistance value.

[Means for solving problems]

A static electricity protection device for a complementary MIS integrated circuit according to the present invention is a static electricity protection device that uses a MIS transistor that is normally non-conducting as a protection element against static electricity at a terminal of the complementary MIS integrated circuit. In order to achieve this, a complementary MIS of the same power supply system for supplying a predetermined potential to the gate electrode of the MIS transistor
It is configured with an inverter composed of transistors.

〔Example〕

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

FIG. 1 is a circuit diagram of the first embodiment of the present invention. As shown in FIG. 1, in this embodiment, the terminal 5 is connected via the resistor 3.
P channel MI corresponding to the internal circuit connected to 1.
The S-transistor 1-1, the N-channel MIS transistor 1-2, and the inverters 2-1 and 2-2 are provided.

In FIG. 1, a P-channel MIS transistor 1-1 is provided.
The N-channel MIS transistor 1-2 and the N-channel MIS transistor 1-2 play a role of protection elements for the internal circuit.
The gate potentials of IS transistors are complementary MI.
Inverters 2-1 and 2-2 composed of S transistors
Is supplied via.

Now, consider a case where positive static electricity is applied between the terminal 51 and the ground power supply. N-channel MIS transistor 1-2
Although a high electric field is temporarily applied between the drain in and the gate, an AC current flows through the coupling capacitance between the drain and the gate and is discharged to the ground power source through the complementary inverter 2-2. At this time, the β values of the N-channel MIS transistor 1-2 and the complementary MIS transistor forming the inverter 2-2 are β _1-2 and β _2-2, and β _2-2 ≦ β _1-2 / 10 By setting the relationship in the order of magnitude, the on-resistance of the inverter 2-2 at the time of the above-described discharge can be made sufficiently high, and the N-channel MIS transistor 1-2 can be obtained.
It is possible to suppress the electric field between the gate and the drain of the device sufficiently low. Even when negative static electricity is applied between the power supply to which the power supply voltage V _DD is supplied and the terminal 51, the electric field between the gate and the drain of the P-channel MIS transistor 1-1 is similarly sufficient. It is suppressed to a low value. Therefore, according to the present invention, the ability to protect the gate insulating films of the P-channel MIS transistor 1-1 and the N-channel MIS transistor 1-2 that act as protection elements for the internal circuit is significantly enhanced.

Note that the values of the inverters 2-1 and β can be designed in proportion to the sizes (β∝W) of the P-channel MIS transistor 1-1 and the N-channel MIS transistor 1-2. There is an advantage that the design is easy as compared with the case of setting the resistance value of the conventional example shown. That is, according to the present invention, the protection capability of the MIS transistor acting as a protection element with respect to the gate insulating film is enhanced, and an electrostatic protection circuit which is easy to design is realized.

FIG. 2 is a circuit diagram of the second embodiment of the present invention.

As shown in FIG. 2, in the present embodiment, a P-channel MIS transistor 1-1, an N-channel MIS transistor 1-2, and a P-channel MIS transistor 1-1 are provided corresponding to the internal circuit connected to the terminal 51 via the resistor 3. The inverters 2-1 and 2-2 and the resistors 4-1 and 4-2 are provided.

As is apparent from FIG. 2, the difference between the second embodiment and the first embodiment is that the inverter 2 for supplying the gate potential is used.
A resistor 4-1 is inserted between the input side of -1 and the ground power source, and a resistor 4-is inserted between the input side of the inverter 2-2 and the power source.
2 is inserted. By adding the resistors 4-1 and 4-2, the protection ability of the inverters 2-1 and 2-2 with respect to the gate insulating film is further improved.
There is an advantage that an integrated circuit with higher reliability can be realized as compared with the above embodiment.

〔The invention's effect〕

As described above, according to the present invention, the gate potential of the non-conductive MIS transistor, which acts as a protection element against static electricity, is supplied through the inverter composed of the complementary MIS transistors of the same power supply system to provide a protection element. There is an effect that the protection capability for the gate insulating film of the MIS transistor can be enhanced and a highly reliable integrated circuit can be provided.

[Brief description of drawings]

1 and 2 are circuit diagrams of the first and second embodiments of the present invention, respectively, and FIG. 3 is a circuit diagram of a conventional electrostatic protection device for a complementary MIS integrated circuit. In the figure, 1-1 ... P-channel MIS transistor, 1-2 ... N-channel MIS transistor, 2-
1, 2-2 ... Inverter, 3, 4-1, 4-2 ... Resistor.

Claims (1)

[Claims] 1. A static electricity protection device using a MIS transistor which is non-conducting in a steady state as a protection element against static electricity of a terminal of a complementary MIS integrated circuit, in order to bring the MIS transistor into a non-conducting state, a gate of the MIS transistor is provided. An electrostatic protection device for a complementary MIS integrated circuit, comprising: an inverter composed of complementary MIS transistors of the same power supply system for supplying a predetermined potential to electrodes.