JPH03217058A - Negative resistance type semiconductor element - Google Patents

Abstract

PURPOSE:To obtain a low avalanche breakdown voltage with substantially no influence on the characteristics of such as holding current or trigger current by forming a PN junction for starting the breakdown at a voltage lower than the breakdown voltage of a main PN junction in parallel with the main junction. CONSTITUTION:In a semiconductor device in which a second conductivity type second semiconductor region 2 formed on one main surface of a first conductivity type semiconductor substrate 1 for forming a first semiconductor region 1', a first conductivity type third semiconductor region 4 surrounded by the region 2, and a second conductivity type fourth semiconductor region 3 formed on the other main surface of the substrate 1 are provided, and carriers are injected to the regions 2, 4 by an avalanche current after an avalanche breakdown of a main PN junction J1 formed of the regions 1', 2, a breakdown starting region 10 for forming a PN junction J4 determining the starting voltage of avalanche breakdown between the first region is formed across the region 2, and the junction J4 is disposed at a shallower position than the junction J1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a negative resistance type semiconductor element having a PNPN structure or an NPNPN structure.

[Conventional technology]

In general, surge voltages occur in communication lines and control lines for various electrical devices due to direct strikes or induction of natural lightning, or the switching of loads.In particular, surge voltages occur as a result of high-density modularization of communication devices and other electronic devices. , ICs that are extremely susceptible to surge voltages and overvoltages. Since LSIffi devices and the like are frequently used, it is increasingly necessary to absorb surges with surge absorbers before the surges enter electronic equipment.

There are various types of such surge absorbers, but elements with a PNPN structure or an NPNPN structure are known as low-loss ones. This has basically been widely known as a four-layer diode, and is characterized in that when a voltage higher than the set voltage is applied to both ends, apalanche breakdown occurs, and the voltage at both ends rapidly decreases.

A conventional surge voltage absorbing semiconductor element having such a structure will be explained with reference to FIG. Regions 2 and 3 are formed, respectively, and an annular N-conductivity type semiconductor region 4 is formed in the semiconductor region 2. The N conductivity type semiconductor region 1' and the P conductivity type semiconductor region 2 formed by the semiconductor substrate l are mainly PN.
A junction J1 is formed, and a PN junction J2 separate from the P conductivity type semiconductor region 2 and the N conductivity type semiconductor region 4 is formed. The P-conductivity type semiconductor region 2 is surrounded by the N-conductivity type semiconductor region 4, and includes a short circuit portion 2a forming an ohmic contact with the electrode 5.

Further, the N conductivity type semiconductor region 1' forms a second main PN junction J with the P conductivity type semiconductor region 3.

What about the surge voltage absorbing semiconductor element with this structure? When a voltage equal to or higher than the avalanche breakdown voltage v8 is applied between poles 5 and 6, the first main PN junction J causes avalanche breakdown, and the current after the avalanche breakdown flows to the first main PN junction J1. Semiconductor area 2 from the side
flows to the electrode 5 through the short-circuit portion 2a. At this time, a voltage drop due to lateral resistance in the P conductivity type semiconductor region 2 occurs at the first main PN junction J. When a threshold of 2 is exceeded, the device turns on and enters a low resistance state. The voltage-current characteristics of this element are shown in FIG.

[Problem that the invention seeks to solve]

However, in such a conventional negative resistance type semiconductor device for absorbing surge voltage, the impurity diffusion profile of the P-conductivity type semiconductor region 2 causes large avalanche breakdown voltage V+++, trigger current, holding current, etc. Since the structure was such that the voltage was determined, it had a low avalanche breakdown voltage vIl1, and at the same time
It has been difficult to fabricate semiconductor devices for absorbing surge voltages that have large trigger current values and holding current values.

The present invention provides a semiconductor structure that makes it easy to manufacture a negative resistance type semiconductor element that has a lower avalanche breakdown voltage than conventional ones without having almost any effect on characteristics such as holding current and trigger current. It is an object.

[Means to solve the problem]

In order to eliminate the disadvantages of conventional semiconductor devices as mentioned above and to achieve this objective, the present invention provides a PN junction that initiates avalanche breakdown at a voltage lower than the avalanche breakdown voltage of the main PN junction. It is characterized by being formed in parallel with the PN junction in terms of an equivalent circuit.

[Effect]

In the negative resistance type semiconductor device according to the present invention, the PN junction formed in series with the main PN junction starts avalanche breakdown at a set voltage lower than the aparansis breakdown voltage of the main PN junction. Since the junction also causes avalanche breakdown, the avalanche breakdown voltage of the negative resistance type semiconductor element can be lowered than in the past.

(Embodiments) Each embodiment of the present invention will be described below according to FIGS. 1 to 4. In these figures, the same symbols as those shown in FIG. 7 indicate corresponding semiconductor regions or members. .

First, in FIG. 1, a P-conductivity type semiconductor region 2 is provided with a short-circuit portion 2a consisting of a plurality of pores surrounded by an N-conductivity type semiconductor region 4, and the semiconductor region 2 is directly connected to the short-circuit portion 2a. It is electrically coupled to electrode 5.

A P' type semiconductor region IO having the same conductivity type and high impurity concentration is formed around the semiconductor region 2. This P'
The type semiconductor region 10 is formed shallower than the semiconductor region 2,
Therefore, although it is arranged in parallel with the main PN junction J in terms of an equivalent circuit, the PN junction J4 is formed at a shallower position than the main PN junction.

In the negative resistance surge voltage absorbing semiconductor device having such a structure, in the process of increasing the voltage between the electrodes 6 and 5,
As shown in FIGS. 5 and 6, a PN junction J4 is formed between the semiconductor region IO and the semiconductor region 1' at a breakdown voltage VB2 lower than the conventional breakdown voltage VBI.
causes avalanche breakdown, and the avalanche starting current I. is a P conductivity type semiconductor region 2
flows laterally, and further flows to the electrode 5 through the short-circuit portion 2a. At this time, when the voltage drop occurring in the semiconductor region 2 and its short circuit 2' exceeds the threshold determined by the PN junction J2 formed by the semiconductor region 2 and the semiconductor region 4, the PN junction J2 is forward biased and becomes conductive. The main PN
Most of the avalanche current due to avalanche breakdown of junction J1 flows through PN junction J2, and the voltage drop across this device decreases rapidly. The current value at this time is the trigger current.

Therefore, according to the structure of this semiconductor device for surge voltage absorption, the surge absorption operation is performed at a lower voltage than conventional similar devices without affecting other characteristics, so it can be used for surge voltage absorption over a wide range. Absorption is possible. In addition, the holding current is 1k. }In addition to the semiconductor region 2, which has a large effect on various characteristics such as the magnitude of the trigger current, the semiconductor region 10 that determines the magnitude of the aparanche breakdown voltage is provided, so that the structure of such a conventional semiconductor device would be contradictory. It is possible to reduce the avalanche breakdown voltage and increase the holding current at the same time. When this device is used to absorb surges in electronic circuits, the one with a larger holding current is more likely to self-extinguish after absorbing the surge. The impact can be reduced.

Note that 7 and 8 are insulating films.

Next, FIG. 2 shows a second embodiment of a negative resistance type surge voltage absorbing semiconductor device according to the present invention.

In this figure, the same symbols as those shown in FIG. 1 indicate corresponding members. In this embodiment, semiconductor regions having the same structure are formed from both main surfaces of the semiconductor substrate l, and the structure is symmetrical about the center line in the thickness direction of the semiconductor substrate l.

The device of this embodiment can absorb surge voltages in both directions, and can perform switching operations at low voltages in both directions.

Next, a third embodiment of the negative resistance type semiconductor device according to the present invention will be explained with reference to FIG. It is characterized by This guard ring region 11 has the same conductivity type as the semiconductor region IO, and functions to improve the accuracy of the avalanche breakdown start voltage.

Next, a fourth embodiment of the present invention will be explained with reference to FIG.
The semiconductor region 10 for starting avalanche breakdown is formed between the N-conductivity type semiconductor regions 4 in the P-conductivity type semiconductor region 2 . The avalanche breakdown starting current in the semiconductor region IO spreads through the P-conductivity type semiconductor region 2 in the left-right direction in the drawing, and flows to the electrode 5 through the respective short-circuit portions 2a. In this embodiment, it is relatively easy to obtain the designed avalanche breakdown start voltage.

In the embodiment described below, if it is desired to increase the holding current, it is also possible to diffuse a lifetime key such as gold or platinum into the short circuit portion 2' of the semiconductor region 2.

[Effects of the Invention] As described above, according to the present invention, the semiconductor region 10 that determines the magnitude of the avalanche breakdown voltage is provided separately from the semiconductor region 2 that has a large influence on various characteristics such as the magnitude of the holding current. Therefore, not only is it possible to reduce the avalanche breakdown voltage and increase the holding current at the same time, which are contradictory in the conventional semiconductor device structure, but also it becomes easy to set the 1 dimension of each semiconductor region, and the yield is improved.

In addition, semiconductor region 1 with shallow aparanche breakdown
Since the semiconductor device turns on with this current, the current spreads quickly at turn-on, and di/
This also has the effect of increasing the amount of dt@#.

[Brief explanation of drawings]

1 to 4 show four different embodiments of the negative resistance type semiconductor device according to the present invention, FIG. 5 is a diagram showing the characteristics of the negative resistance type semiconductor device according to the present invention, and FIG. 6 7 is a diagram showing the characteristics of the conventional negative resistance type semiconductor element shown in FIG. 7. FIG. 1... Semiconductor substrates of N conductivity type 2, 3... Semiconductor region 2a of P conductivity type... Short circuit part of semiconductor region 2... Semiconductor region of N conductivity type 5.6... Electrode 7 .8...Insulation N ■ 2 10...Semiconductor region for starting avalanche breakdown

Claims (6)

[Claims] (1) A semiconductor substrate of a first conductivity type forming a first semiconductor region, a first semiconductor substrate formed on one main surface side of the semiconductor substrate;
a second semiconductor region of a second conductivity type opposite to that of the conductivity type; a third semiconductor region of the first conductivity type formed to be surrounded by the second semiconductor region; and the semiconductor substrate. an avalanche break of the main PN junction formed by the first semiconductor region and the second semiconductor region, including at least a fourth semiconductor region of the second conductivity type formed on the other main surface side of the In a semiconductor device in which carriers are injected into the second semiconductor region and the third semiconductor region by an avalanche current after down, a PN junction that determines the starting voltage of avalanche breakdown is connected to the first semiconductor region. The breakdown start region formed in the second
1. A negative resistance type semiconductor device, characterized in that the PN junction is formed so as to extend over a semiconductor region, and the PN junction is located at a shallower position than the main PN junction. (2) Claim (1) characterized in that the breakdown start region is formed around the second semiconductor region.
Negative resistance type semiconductor device according to. (3) The negative resistance type semiconductor device according to claim (1), wherein the breakdown start region exists between the third semiconductor regions. (4) A negative resistance type semiconductor device, characterized in that a guard ring semiconductor region is provided on the outer periphery of the breakdown start region. (5) In the first semiconductor region, a fifth semiconductor region and a sixth semiconductor region, which are equivalent to the second semiconductor region and the third semiconductor region, are provided at positions symmetrical to these regions. Negative resistance type semiconductor device with special features. (6) The negative resistance type semiconductor device according to claim (1), wherein a lifetime killer such as gold or platinum is diffused in the breakdown initiation region.