JPH011284A - zener diode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a Zener diode formed on a semiconductor substrate such as a monolithic IC.

[Technical background of the invention and its problems] Conventionally, there are Zener diodes as described above as shown in FIGS. 4 and 5. In the figure, 11 is an n-type layer formed on the substrate by epitaxial growth, and 12 is a p'' region 13 formed in the n-type layer by impurity diffusion.
is an n''prJ region formed by diffusion to form a pn junction with the p' region 2.

14 is an insulating layer of silicon dioxide grown in a vapor phase; 15.
Reference numeral 16 denotes an aluminum electrode formed so as to be connected to the p'' region 2 and the n+ region 13, respectively, through a hole formed in the insulating layer I4.
A depletion layer is formed near the pn junction of the and n' regions 13 due to carrier diffusion between both regions.

When a reverse bias voltage is applied between the p'' region 12 and the n'' region 13 via the electrodes 15 and 16, tunneling occurs at the diagonally shaded junction in the figure, that is, at the portion near the insulating layer 1-4 of the p-n junction. A breakdown phenomenon occurs due to the effect or avalanche effect, and it operates as a Zener diode.

However, in the conventional Zener diode as described above, hot electrons are injected into the insulating layer 14 during reverse bias, and this affects the portion of the pn junction near the insulating layer where junction breakdown occurs, so the depletion layer There was a problem in that the shape of the capacitor changed slightly and the breakdown voltage changed over time.

[Purpose of the invention]

An object of the present invention is to solve the above problems and provide a stable Zener diode whose characteristics such as breakdown voltage do not change.

[Summary of the invention]

In order to achieve the above object, the present invention provides a Zener diode in which junction breakdown occurs at a pn junction near a surface insulating layer. Most of the area was covered with an electrode connected to the p-swell region side.

This reduces hot electrons injected into the insulating layer, suppresses changes in the depletion layer, and maintains a stable breakdown voltage.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the Zener diode of the present invention, where (a) is a plan view and fbl is a cross-sectional view.

In the figure, 1 is an n-type layer formed on the substrate by epitaxial growth, 2 is a p'' region 3 formed in the n-type layer 1 by impurity diffusion, and is an n'' region formed in the above p'' region. p between n″ area 2 and n″ area 3
A depletion layer is formed near the n-junction by carrier diffusion between both regions.

4 is an insulating layer of silicon dioxide formed by heat treatment, and 5 and 6 are the above-mentioned p'' through holes formed in insulating layer 4.
The electrode 5 is made of aluminum and is formed to be connected to the n″ area 2 and the n″ area 3, respectively.As shown in FIG. n
It is formed in such a shape as to cover the terminal portion of the pn junction with the ``region 3, that is, the pn junction J near the insulating layer 4 from above the insulating layer 4.

Further, the electrodes 6 in the three examples of the n'' region are connected to a contact portion 6a formed at the same time as the electrode 5 on the p'' region side, and a second insulating layer that is bonded to the contact portion 6a and maintains insulation from the electrode 5. 4
'.

When a reverse bias voltage is applied between the n'' region 2 and the n'' region 3 via the electrodes 5 and 6, a tunnel effect occurs at the diagonally shaded junction in the figure, that is, at the pn junction J near the insulating layer 4. Alternatively, a breakdown phenomenon occurs due to an avalanche effect, and the diode operates as a Zener diode.

At this time, since the electrode 5 on the p'' region side, which is negatively biased, covers the pn junction J from above the insulating layer 4, it becomes difficult for hot electrons to be injected into the insulating layer 4. Changes in the shape of the depletion layer due to injection are suppressed, and changes in breakdown voltage over time are reduced.

FIG. 2 is a diagram showing another embodiment, in which parts corresponding to those of the first embodiment are designated by the same reference numerals as in FIG. 1. Moreover, n-type layer 1. p” region 2. n” region 3.
The insulating layer 4 is formed in the same manner as in the first embodiment.

In this embodiment, the electrode 6 on the side of the n+ region 3 is formed in one step so that its lead-out portion overlaps the insulating image 4.
As shown in FIG.
It is formed to cover the pn junction J with the + region 3.

In this way, since the electrode 5 on the p'' region side to which a negative bias is applied covers most of the pn junction J, the same effect as described above can be obtained, and the number of planar processing steps can be reduced. can.

In the above embodiments, the n'' region is formed within the p' region, but as shown in FIG.
Regarding a Zener diode in which a pn junction is partially formed by the and n'' region 3, the pn junction J near the insulating layer 4 is connected to the electrode 5 on the p'' region 2 side from above the insulating layer 4. A similar effect can be obtained by covering it.

〔Effect of the invention〕

According to the present invention, in a Zener diode in which junction breakdown occurs at a pn junction near a surface insulating layer, all or most of the termination portion of the pn junction on the surface insulating layer side where junction breakdown occurs is placed on the p-type region side. Since it is covered with an electrode bonded to the insulating layer, hot electrons injected into the insulating layer can be reduced and changes in the depletion layer can be reduced, making it possible to obtain a stable Zener diode with no change in characteristics such as breakdown voltage. can.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the Zener diode of the present invention, Fig. 2 is a diagram showing another embodiment of the Zener diode of the present invention, and Fig. 3 is a diagram showing a junction surface with a part of the p'' region and the n'' region. 4 and 5 are diagrams showing examples of conventional Zener diodes. 2... p'' region 3... n'' region 4... insulating layer, 5
... Electrode on the p'' region side, 6... Electrode on the n'' region side. Patent applicant Pioneer Corporation Pioneer Video Corporation Figure 1 (a) Figure 2

Claims (1)

[Claims] In a Zener diode in which junction breakdown occurs at a pn junction near the surface insulating layer, an electrode in which all or most of the terminal end on the surface insulating layer side of the pn junction where junction breakdown occurs is connected to the p-type region side. Zener diode characterized by covered.