JPS58132981A - Zener diode - Google Patents

Abstract

PURPOSE:To strengthen the resistivity to a surge voltage by avoiding concentration of field to the edge of an emitter. CONSTITUTION:An emitter region 3 is formed within a base region 2. A graft- base region 4 is a high impurity concentration region provided for extending a base electrode. On the occasion of forming the graft-base region 4, a high impurity concentration region 4' is formed simultaneously under the emitter region 3. Thereby, zener yielding of a zener diode occurs at the entire part of junction area 6 between the emitter region 3 and high impurity concentration region 4'. Therefore, such yielding point becomes equal, as an electrostatic breakdown strength, to difference of impurity concentrations of the emitter region 3 and high impurity concentration region 4' and a theoretical strength determined by the junction area.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Zener diode that is resistant to electrostatic damage.

Bipolar transistor pace and emitter in general? It is widely known that a 1% compound can be used as a Zener diode, but generally speaking, during the emitter diffusion, the base of the emitter is shallow and spreads out in a circular shape with a small curvature, and the surface of the emitter is shallow during diffusion. The impurity concentration is highest in the near area, so in a Zener diode that uses the PM junction between the pace and emitter of a bipolar transistor, if a reverse bias is applied to the PN junction, a surge voltage may be applied. The electric field is concentrated in the circular portion, and destruction may occur at the end of the emitter with an intensity lower than the theoretical intensity.

FIG. 1 is a cross-sectional view of a Zener diode that utilizes a PN junction between the emitter of a conventional bipolar transistor and a paste, in which an emitter region 3 is formed in a paste region 2, and a graft base region 4 is a paste electrode. This is a high impurity concentration region for extracting. The Zener breakdown of the Zener diode is determined at the end 5 of the emitter, and since this part has a circular shape, electric field concentration also occurs.
Electrostatic breakdown also occurs in this part. However, the electrostatic breakdown that occurs at the emitter end 5 occurs at a strength lower than the theoretical strength of the P1iT junction, which is simply determined by the difference in impurity concentration. This means that the required curvature of the emitter end This is thought to be due to the electric field concentration phenomenon caused by the low circular shape.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a Zener diode that does not generate electric field concentration noise, that is, Zener breakdown occurs throughout the junction.

A feature of the present invention is that, for example, in a zener diode that utilizes the PM junction between the pace and emitter of a bipolar transistor, the base electrode is usually provided at a graft base portion (selectively provided) with a relatively high concentration. By selectively forming a semiconductor region similar to the semiconductor layer under the region where the emitter is to be formed within a range that does not protrude from the above-mentioned head, the difference in impurity concentration can be reduced in the junction between the emitter and the paste. The area where Zener breakdown is determined is the bottom of the emitter.This eliminates the electric field concentration at the end of the m&2 emitter, resulting in a Zener diode that is resistant to surge voltages such as static electricity. It is.

Hereinafter, one embodiment of the present invention will be described in detail using the drawings.

FIG. 2 is a cross-sectional view of one embodiment of the Zener diode of the present invention. Its structure is almost the same as that in FIG. If formed in advance, Zener breakdown of the Zener diode of the present invention occurs throughout the junction 6 between the emitter region 3 and the high impurity concentration region 41.

At this time, the electric field concentration that occurred at the emitter end 5 shown in FIG. It is almost equal to the determined theoretical strength.

As described above, according to the present invention, a Zener diode with high electrostatic breakdown strength can be easily obtained without increasing the number of conventional Zener diode formation steps.

Although the above embodiment has described a Zener diode that utilizes the PM junction between the pace and emitter of a bipolar transistor, in addition, as shown in FIG.
Needless to say, the present invention can also be applied to Zener diodes that utilize the PM junction created by forming 7 and 7.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a Zener diode that uses a conventional bipolar transistor pace and emitter PM junction, and Figure 2 is a Zener diode that uses a bipolar transistor pace and emitter PM junction in an embodiment of the present invention. FIG. 3 is a cross-sectional view of a Zener die and an ode using a PM junction between a bipolar transistor pace and a buried layer lead-out region in another embodiment of the present invention. 100. Semiconductor substrate 200. Pace area ゛300. Emitter area 4.41°. Graft base region 50. . m part 6' of the emitter region, 1. Junction 700 of the rL high bulk impurity concentration region provided simultaneously when forming the emitter region and the craft base region. Embedded layer drawer area ゛800. Buried layer 90. . Applicant for vapor growth layer and above: Daini Seikosha Co., Ltd.

Claims (1)

[Claims] A first semiconductor layer of an opposite conductivity board selectively formed on a semiconductor substrate of one conductivity type, and a second semiconductor layer of one conductivity type selectively formed as one terminal in the first semiconductor layer. and a third semiconductor layer of an opposite conductivity type that is higher than the first semiconductor layer and is formed as another terminal under the second semiconductor layer, and the second semiconductor layer The impurity concentration of the third and first semiconductor layers applied to the junction between the semiconductor layer and the third and first semiconductor layers is the highest at the junction at the bottom of the second semiconductor layer. Zener diode.