JPS62285460A - Protective circuit for input - Google Patents

Abstract

PURPOSE:To obtain an input protective circuit easy to break down and having a large current path by mutually opposing and forming the same conductivity type diffusion layers connected at supply potential to a reverse conductivity type layer and shaping bent sections to opposed sides. CONSTITUTION:An N+ layer 1 at potential VCC and an N<+> layer 2 at potential VSS are arranged oppositely to a P-type substrate at a short distance, bent sections 1a, 2a are shaped to opposed sides, the space of the layers 1, 2 is all equalized, and currents are easy to be flowed similarly, thus forming a larger current path. A large number of the bent sections in the diffusion layers easy to break down are shaped, and the current path is broadened, thus preventing the generation of the breakdown of the diffusion layers in an internal circuit.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Objective of the Invention (Industrial Application Field) The present invention relates to an input protection circuit in a semiconductor integrated circuit.

(Prior art) During electrostatic withstand voltage testing of semiconductor integrated circuits, power supply bins (vcc
and v88), the potential of one of which is fixed, and the potential applied to the other, the diffusion layer causes breakdown, and a current path is generated between the diffusion layer and the diffusion layer with the fixed potential. At this time, if a current flow occurs in only a part of the diffusion layer of the internal circuit, a large current will concentrate and the diffusion layer will be destroyed.

Therefore, in order to prevent large current from concentrating on the internal circuit,
An input protection circuit as shown in FIG. 5 has been proposed in which a diffusion layer at a potential of 'rL and a diffusion layer at a potential of v8s are arranged close to each other. In the figure, 1 is an N+ type diffusion layer of about vcct, 2 is an N+ type v,
1c is a diffusion layer, and 3 is a diffusion layer of these layers.

2t- is a P-type substrate provided. The input protection circuit shown in FIG. 5 must create a large current path that prevents current from concentrating, and must also break down earlier than the internal circuit. The above-mentioned breakdown phenomenon occurs more easily in the curved 9-cornered portion than in the straight line portion of the diffusion layer. This is because the electric field is more concentrated in the curved portions of the diffusion layer than in the straight portions.

(Problem to be Solved by the Invention) As shown in the figure, since the opposing portions of the diffusion layers 1 and 2 are parallel straight lines, 1! There were few dense areas in the field, making it difficult for breakdowns to occur.

The present invention has been made in view of the above circumstances, and is intended to provide an input protection circuit that is prone to breakdown and has a large current/4' current.

[Structure of the Invention (Means and Effects for Solving the Problems)] The present invention provides diffusion layers of the same conductivity type connected to a power supply potential and facing each other in layers of opposite conductivity type. 1# is characterized in that a bent portion is provided on the opposing sides. That is, in the present invention, the diffusion layer has many curved portions that are likely to cause breakdown.

(Example) An example of the present invention will be described below with reference to the drawings. 1st
This figure is a plan view of the same embodiment, but since this is an example corresponding to that of FIG. 5, the same reference numerals are used for corresponding parts. In Figure 1, 1 is type 1 V. 2 is a diffusion layer of C potential, 2 is an N+ type diffusion layer of V88 position, and 3 is a P type substrate on which these diffusion layers 1.2 are disposed facing each other at a short distance.

A feature of this input protection circuit is that a bent portion 1*+2th is provided on the opposite side of the diffusion layer 1.2 to facilitate breakdown. Further, the distances between the diffusion layers 1 and 2 are all made uniform to create conditions where current can easily flow in the same manner, thereby creating a larger current flow.

It should be noted that the present invention is not limited to only practical arrays, and can be applied to many other applications. For example, the bent portions 1a of the diffusion layers 1 and 2.

2a may have a configuration as shown in FIGS. 2 to 4.

[Effects of the Invention] As explained above, according to the present invention, breakdown is likely to occur and the current/gas is large, so that breakdown of the diffusion layer of the internal circuit is less likely to occur.

[Brief explanation of the drawing]

FIG. 1 is a plan view of one embodiment of the present invention, and FIGS.
This figure is a plan view of another embodiment of the present invention, and FIG. 5 is a plan view of a conventional input protection circuit. 1.2...N+ layer, 3...P type substrate,' a r
2 a...Bending part. Applicant's agent Patent attorney Takehiko Suzue @2 diagram
Figure 3

Claims (2)

[Claims] (1) Diffusion layers of the same conductivity type connected to a power supply potential are provided opposite to each other in layers of opposite conductivity type, and each of the diffusion layers is provided with a bent portion on the side where they face each other. input protection circuit. (2) The input protection circuit according to claim 1, wherein the distance between opposing sides of the diffusion layers is uniform.