JPH011285A - 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. 5 and 6. In the figure, 21 is an n-type layer formed on the substrate by epitaxial growth, and 22 is a p'' region 23 formed in the n-type layer by impurity diffusion.
is an n' region formed by diffusion so as to form a pn junction with the p' region 2 described above.

24 is an insulating layer of silicon dioxide grown in a vapor phase; 25.
Reference numeral 26 designates aluminum electrodes formed so as to be connected to the p'' region 2 and the n'' region 23, respectively, through holes formed in the insulating layer 24. In addition, the above p'' region 2
A depletion layer is formed near the pn junction of the and n' regions 23 due to carrier diffusion between both regions.

When a reverse bias voltage is applied between the p'' region 22 and the n' region 23 via the electrodes 25 and 26, a tunnel effect or avalanche occurs at the diagonally shaded junction in the figure, that is, at the pn junction near the insulating layer 24. A breakdown phenomenon occurs due to the 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 24 during reverse bias, and this affects the part of the pn junction near the insulating layer where junction breakdown occurs, so the depletion layer There was a problem in that the shape changed suddenly 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 formed by forming a layered semiconductor, in which an n-type region or a p-type region is formed near the surface, and the n-type region or p-type region is formed inside the semiconductor layer. A p-type or n-type buried region with high impurity concentration forming a pn junction is formed at the boundary surface of the region, and the pn of the buried region inside the semiconductor layer is
Made yielding occur at the junction.

This reduces the influence of charges such as hot electrons injected into the insulating layer on the semiconductor surface, suppresses changes in the depletion layer, and keeps the breakdown voltage stable.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the Zener diode of the present invention, where 1 is a p-type substrate, 2 is an n-type layer formed on the p-type substrate 1 by epitaxial growth, and 31 and 32 are the surfaces of the n-type layer 20. The n-type layer 2 is divided into a plurality of island-like regions by the p-separated classification regions 3xs3t.

4 is an n'' region formed by diffusing impurities in one of the p-isolated regions 32, and this n'' region 4 and the p-isolated region 32 are
A pnn junction furnace is formed by this. A depletion layer is formed near this pnn junction furnace by carrier diffusion between both regions.

5 is an insulating layer of silicon dioxide formed on the surface by heat treatment, and 6 is the above n through the hole formed in the insulating layer 5.
This electrode is made of aluminum and is formed to be connected to another diagonal region 31 that is not connected to the "n" region, and 7 is an electrode that is similarly joined to the n" region 4.

Then, when a reverse bias voltage is applied between the p-isolated region 31 and the n'' region 4 via the electrodes 6 and 7, a breakdown phenomenon occurs at the pn junction due to the tunnel effect or avalanche effect, and the n'' region 4 , p゛゛ separation region 32 , p
Carriers are transferred between the shaped substrate 1 and the p'min'F=M region 31, and the device operates as a Zener diode.

In other words, the 1ii1 area 32 for the above p'' is the n'' area 4
The implantation region is formed between the p-type substrate 1 and the p-type substrate 1, and since it is inside the pnn junction furnace semiconductor layer formed by this, it is not affected by charges such as hot electrons injected into the insulating layer 4, and the depletion Changes in the shape of the layer are suppressed,
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.

This Zener diode is connected to the p-isolated region 32 forming the n'' region 4 of the first embodiment.
A second p'' region 3' having a higher impurity concentration is formed, and after this second p'' region 3' is formed, an n+ region 4 is formed.

In this way, the second p4 region 3' is formed as a buried region under the n' region, and this p'LQ 1jj
A breakdown phenomenon occurs at the pn junction J' between t, 3' and the n'' head region 4, and carriers are transferred via the p-type substrate 1 and the p-separation region 31, as described above. .

FIG. 3 is a diagram showing a third embodiment, in which 12 is an n-type layer formed on a substrate by epitaxial growth;
13 is a p-type layer formed in the n-type layer 12 by impurity diffusion.
The ``region 13'' is a second p'' region formed as a buried region in the p'' region 13, and this second p'' region 13' is similar to the second embodiment. 1 p''
It is formed with a higher impurity concentration than region 13.

1'4 is a p'' region formed above the second p'' region 13', and this n+ region 14 is a p'' region 1
2, the junction J1 at the interface with the second p' region 13
A junction J2 is formed at the interface with '.

15 is an insulating layer of silicon dioxide formed by heat treatment; 16 is a first insulating layer formed through a hole formed in the insulating layer 15;
An electrode made of aluminum is formed so as to be connected to the p'' region 13, and an electrode 17 is similarly connected to the n'' region 14.

Then, when a reverse bias voltage is applied between the first p'' region 13 and the n'' region 14 via the electrodes 16 and 17, the second p'' region 13' becomes more sensitive than the first p' region 13. Since the impurity concentration is high, a breakdown phenomenon occurs at the junction J2 between the second p'' region 13' and the n'' region 14, and the junction J2 operates as a Zener diode.

Therefore, since the junction J2 in which the breakdown phenomenon occurs is located inside the semiconductor layer, it is not affected by charges and the like as described above, and the change in breakdown voltage over time is reduced.

In addition, as shown by the single point iJi line in Fig. 3, the first p
It is also possible to form an n'' region 14 within the 'region 13.

In this way, if the impurity concentration of the second p'' region 13' is higher than that of the first p'' region 13, the effect can be reduced,
For example, it goes without saying that the second p'' region 13' may be formed by diffusion to a depth that reaches the n-type layer 12, as shown in FIG.

〔Effect of the invention〕

According to the present invention, in a Zener diode made of a layered semiconductor, a buried region is formed inside the semiconductor layer, and breakdown occurs at a pn junction inside the semiconductor layer due to the buried region. The influence on the depletion layer due to charges such as injected hot electrons can be reduced, and a stable Zener diode whose characteristics such as breakdown voltage do not change can be obtained.

[Brief explanation of drawings]

FIGS. 1 to 4 are diagrams showing each embodiment of the Zener diode of the present invention, and FIGS. 5 and 6 are diagrams showing an example of a conventional Zener diode of -1°. 31.32...p separation region, 3', 13.13'.
...p'' area, 4,14...p'' area. Patent applicant Pioneer Corporation Pioneer Video Corporation Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] A Zener diode formed of a layered semiconductor, comprising an n-type region or p-type region formed near the surface and an interface between the n-type region or p-type region inside the semiconductor layer. It is characterized by having a p^+ type or n^+ type buried region with high impurity concentration forming a pn junction in the semiconductor layer, and breakdown occurs at the pn junction of the buried region inside the semiconductor layer. Zener diode.