JPH0888326A - Electrostatic protection structure of semiconductor device - Google Patents

Abstract

PURPOSE: To obtain an electrostatic protection structure which can make static electricity escape to the outside with reponsivity and prevent occupied by a substrate good responsivity and an area occupied by a substrate from increasing. CONSTITUTION: A Schottky barrier diode 6 is interposed between an external input/output device and an input/output terminal for a semiconductor circuit. The side of a cathode for the Schottky barrier diode 6 and a grounding conductor are connected in such a way that a p-n junction diode is interposed. Thereby, static electricity from an external circuit is cut off by the Schottky barrier diode 6, it can be by-passed to the grounding conductor by the p-n junction diode 7, and the static electricity can be made to escape to the outside with good responsivity in a small area occupied by a substrate. Especially, when an inpurity-diffused layer which is used for the Schottky barrier diode 6 and an impurity-diffused layer, on one side, which is used for the p-n junction diode 7 are used in common, the area occupied by the substrate can be made smaller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device static electricity protection structure, and more particularly to a semiconductor device static electricity protection structure for inputting and outputting a signal from an external input / output line to an internal circuit through an inverter.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, an electrostatic protection circuit in a semiconductor device for inputting / outputting a signal to / from an internal circuit from an external input / output line via an inverter has an external input / output line and an inverter 11, as shown in FIG. A resistor 12 and a transistor (used as a diode) 13 are provided between the two, and when the static electricity is generated, the resistor 12 attenuates the voltage and increases the time constant, and then the transistor 13 bypasses to the GND.

[0003]

However, it is necessary to increase the substrate occupying area so that the resistor 12 itself for lowering the peak voltage of static electricity is not destroyed, and the transistor 13 also has a high responsiveness to bypass. Since it is necessary to increase the substrate occupying area in the same manner as described above in order to improve the performance and reduce the ON resistance, there is a problem that the area of the protection circuit becomes very large as a result and the device becomes large.

The present invention has been made in view of the problems of the prior art as described above, and its main purpose is to allow static electricity to be released to the outside with good responsiveness and not to increase the occupied area of the substrate. It is to provide an electrostatic protection structure for a semiconductor device.

[0005]

According to the present invention, there is provided an electrostatic protection structure of a semiconductor device for protecting a semiconductor device connected to an external device from static electricity from the external device side. A Schottky barrier diode is interposed between the external device and an input / output terminal of the semiconductor device, and a cathode side of the Schottky barrier diode and a ground line are connected via a pn junction diode. This is accomplished by providing an electrostatic protection structure for a semiconductor device. In particular, with the substrate on which the semiconductor device is formed as the ground line, the pn junction diode is formed between the substrate and an impurity diffusion layer formed by diffusing impurities in the substrate, and the Schottky barrier diode is formed. It is preferable that one end is formed on the impurity diffusion layer and the other end is formed between the wiring layer connected to the external device and the impurity diffusion layer.

[0006]

The Schottky barrier diode has a saturation current about 1000 times larger than that of a normal pn junction diode.
Also, since there is no charge storage effect, high-speed response is possible,
It is also easy to manufacture. The Schottky barrier diode blocks static electricity from an external circuit, and the pn junction diode bypasses the ground line to reduce static electricity applied to the internal circuit and protect the circuit.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing a structure of a protection circuit to which the present invention is applied, and FIG. 2 is a circuit diagram thereof. An impurity diffusion region 2 is formed on the substrate 1, and an external connection side wiring layer 3 connected to an external input / output device (not shown) is patterned on the left side of the figure on the surface thereof. Further, on the surface of the impurity diffusion region 2 of the substrate 1, an internal connection side wiring layer 4 connected to the inverter 5 is patterned at a position separated from the external connection side wiring layer 3.
Here, since the external connection side wiring layer 3 made of metal is in contact with the surface of the impurity diffusion region 2, the Schottky barrier diode 6 is formed in this portion. Also,
A pn junction diode 7 is formed between the impurity diffusion region 2 and the substrate 1.

Therefore, in this circuit, as well shown in FIG. 2, the external connection side wiring 3 connected to the external input / output device is connected to the signal input terminal of the inverter 5 via the Schottky barrier diode 6, and the substrate 1 That is, the ground line is connected to the cathode side of the Schottky barrier diode 6 and the signal input terminal of the inverter 5 via the pn junction diode 7. Reference numeral 8 in FIG. 1 is an insulating film such as LOCOS, and reference numeral 9 is a high-concentration impurity diffusion region.

The operating procedure of this embodiment will be described below. First, normally, the Schottky barrier diode 6
Is in the forward direction and the pn junction diode 7 is in the reverse direction, so that the signal of the inverter 5 is directly input.

Next, when static electricity comes in from the external connection side wiring 3 connected to the external input / output device, the Schottky barrier diode 6 blocks this static electricity with good responsiveness and at the same time through the pn junction diode 7 to the substrate. 1, bypassed to ground.

[0011]

As is apparent from the above description, according to the electrostatic protection structure of the semiconductor device of the present invention, the Schottky barrier diode is interposed between the external device and the semiconductor device and the Schottky barrier diode By connecting the cathode side and the ground line with the pn junction diode interposed, the Schottky barrier diode blocks the static electricity from the external circuit, and the pn junction diode bypasses the ground line to eliminate the static electricity in a small board occupation area. It can be released to the outside with good responsiveness. In particular, by making the impurity diffusion layer used for the Schottky barrier diode and the one impurity diffusion layer used for the pn junction diode common, the substrate occupation area can be further reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an electrostatic protection structure of a semiconductor device to which the present invention is applied.

FIG. 2 is an equivalent circuit diagram of FIG.

FIG. 3 is an equivalent circuit diagram of a conventional semiconductor device electrostatic protection structure.

[Explanation of symbols]

 1 substrate 2 impurity diffusion region 3 external connection side wiring layer 4 internal connection side wiring layer 5 inverter 6 Schottky barrier diode 7 pn junction diode 8 insulating film 9 high concentration impurity diffusion region 11 inverter 12 resistor 13 transistor

Claims (2)

[Claims] 1. A static electricity protection structure of a semiconductor device for protecting a semiconductor device connected to an external device from static electricity from the external device side, wherein a Schottky barrier is provided between the external device and the semiconductor device. A static electricity protection structure for a semiconductor device, characterized in that a diode is interposed and a cathode side of the Schottky barrier diode and a ground line are connected via a pn junction diode. 2. The pn junction diode is formed between the substrate and an impurity diffusion layer formed by diffusing impurities into the substrate, with the substrate on which the semiconductor device is formed as the ground line. The barrier diode has one end formed on the impurity diffusion layer and the other end formed between the wiring layer connected to the external device and the impurity diffusion layer. Electrostatic protection structure for semiconductor devices.