JPH03136374A - Surge protective device - Google Patents

Abstract

PURPOSE:To surely perform surge protection by constituting an electrode of an N type base and P type emitter, part of which is short-circuited with the base, and two pieces of such electrodes are provided on each surface of a common P type semiconductor substrate so that the two pieces of electrodes on one surface can face nother two pieces of electrodes on the other surface. CONSTITUTION:By using a P type semiconductor substrate as a common substrate, layers N1, N2, N3 and N4 having the same shape, the same impurity concentration distribution, the same thickness, etc., are formed on both surfaces of the substrate by the same forming process under the same left-right positional relation and layers P1, P2, P3 and P4 having the same shape, the same impurity concentration distribution, the same thickness, etc., are respectively formed in the layers N1, N2, N3, and N4 under the same positional relation. Then, metallic electrodes T1, T2, T3, and T4 are respectively formed between the layers N1 and P1, N2 and P2, N3 and P3, and N4 and P4. In such a way, one electrode is constituted of one N type base and P type emitter, part of which is short-circuited with the base, and two pieces of such electrode are provided on one surface of the common substrate, with nother two piece being provided on the other surface, so that the electrodes can face each other and can be connected by junction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a PNPNP (or NPNPN) type surge protection device, which has excellent surge protection functions for communication lines, etc. be.

(Prior art and its problems to be solved) A bidirectional two-terminal thyristor consisting of five layers of PNPNP as shown in Fig. 1(a) and having an equivalent circuit as shown in Fig. 1(c) is as follows:
Because they are small and inexpensive, have a high overcurrent resistance, and are easy to use because they are two-terminal devices, they have begun to be widely used as protection against lightning surges in communication lines and other areas.

By the way, in the past, for example, as shown in Figure 2, when protecting the line L11L! Protective elements against positive and negative surges that enter between and contact E, so-called vertical surge protective elements (1) (2)
The use of three bidirectional two-terminal thyristors is a so-called mechanical surge element (3), which is a protection element against surges that enter between the line, line, and Lx.

However, as mentioned above, in a protection circuit using a bidirectional two-terminal thyristor with multiple tubes, for example,

When a vertical surge simultaneously enters between line L2 and ground E, elements (1) and (2) do not operate at the same time,
If only child (1) is activated, line p, L1. A surge voltage (lateral surge) is applied between Lz and the element (3) connected between lines jlL, , i.
] If the operation of ψ is delayed than that of the element (υ), there is a risk that the surge current will enter the protected electronic circuit G connected between the lines 14 L, i, and Lz, causing its damage.

Therefore, in order to avoid such a situation, it is important to suppress variations in the characteristics of each surge protection element to an extremely low level so as not to cause a delay in operation.

However, its characteristics are related to the impurity concentration distribution of the PNPNP layer shown in Figure 1 (a), its lifetime, thickness, and mutual positional relationship, and it is very difficult to form these in the same way in each device. The difficulty becomes even greater because the amount changes during manufacturing processes such as diffusion methods. Moreover, even if it were to select elements with very few characteristics from among the manufactured ones, not only would it take a lot of effort, but it would also be difficult to find elements that generally match.

(Object of the Invention) The present invention has been made for the purpose of providing a surge protection device that can solve the above problems.

(Means of the present invention for solving the problem) In the conventional surge protection circuit shown in FIG.
) have the same characteristics and are turned on at the same time against vertical surges, protection can be provided not only against vertical surges but also against horizontal surges applied across the line and L2, and device (1) A surge protection circuit can be formed using only (2).

From the above, if the present invention has a structure in which elements (1) and (2) are combined using a P-type semiconductor substrate as a common substrate, element (1)
) and the PN layer forming element (2).
By adopting the same manufacturing process for the PNP layers, it is possible to form the impurity concentration distribution, thickness, mutual positional relationship, etc. required for each layer to be the same, and even if there are changes during the manufacturing process, these will change in the same way.

Therefore, it is possible to obtain a composite device of the conventional elements (1) and (2) having the same characteristics, and as a result, even when the surge voltage described above is applied as shown in FIG. can be turned on at the same time, and substantially the same surge protection effect as the circuits using devices (1), (2), and (3) can be obtained.

Since the present invention has been made based on the above idea, the present invention will now be described with reference to examples.

3(a), (b), and (C) are a top view (the electrodes are not shown), a sectional view, and a bottom view (the electrodes are not shown) showing the embodiment of the present invention, and their characteristics are The place to do it is P
N, N, N, N of the same shape with the same impurity concentration distribution, the same thickness, etc. based on the same positional relationship on the left and right sides of both sides by the same manufacturing process using a type semiconductor substrate as a common substrate.
3. In addition, in the 20 NINg N3 N4 layer, there are P I+ P ! of the same shape with the same impurity concentration distribution, the same thickness, etc. based on the same positional relationship. +P 3t
Form P a. And N1PI, N! Pg and N3 P3. Electrode metals T + , T 2 and T 3 . respectively span N4 Pa. The point is that the configuration includes T4. As a result, the N-type base and the P-type emitter, which is partially short-circuited, are used as one electrode, and two of these are separated by bonding so as to face each other with the common substrate in between, and the electrodes of each layer are Figure 1 (
Devices A and B having the characteristics of the 5-layer bidirectional 2-terminal silicon risk shown in b) are formed.

Therefore, if the electrode T1 of the device C of the present invention is connected to the line L2 and the electrode T2 is connected to the ground E, and the electrode T is connected to the line L2 and T is connected to the ground E as shown in FIG. ,,
When a vertical surge is applied between L and ground E,
Based on the same principle as the conventionally well-known bidirectional two-terminal thyristor, the two electrodes T1T and TsTa are turned on at the same time, so the surge voltage is not applied as a lateral surge across the line LIL2, and one The element (1
)(2) This results in the same surge protection effect as that provided by (3). Furthermore, since the present invention is a combination of two devices, it is compact and economical.

The present invention has been explained above using one embodiment, but N1Nt N
s, Na, P+ P! Various modifications can be considered as long as the shapes of the P z P4 layer and the like are the same. Further, a conductivity type structure opposite to that described above may be used. Still further, the present invention can be constructed using any desired semiconductor material, such as silicon.

Further, in an actual device, in order to ensure voltage resistance and reliability, as in the conventional device, consideration is given to providing a P+ layer and installing a surface protection film to which a channel stopper structure is applied, as shown in FIG.

Practically, as shown in FIG. 4, a structure is used in which the electrodes T, T connected to the grounding wire are connected inside a device made of resin molding or the like, and one connection lead is pulled out.

(Effects of the Invention) As is clear from the above, according to the present invention, it is possible to provide a device that can provide reliable protection without causing problems due to uneven characteristics of elements as in conventional circuits. It is highly effective when used for protection.

[Brief explanation of the drawing]

1 and 2 are an explanatory diagram of a bidirectional two-terminal thyristor and a conventional surge protection circuit diagram, FIG. 3 is a diagram of an embodiment of the present invention, and FIG. 4 is a surge protection circuit diagram according to the present invention. FIG. 5 is a diagram of another embodiment. Figure 3 Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] N-type (P-type) base and P-type (N
A P-type (N type) emitter is used as one electrode, and this is connected to two P-type (N
type) A surge protection device characterized by being provided facing each other across a common semiconductor substrate.