WO1993026048A1

WO1993026048A1 - Pn junction diode and its manufacture method

Info

Publication number: WO1993026048A1
Application number: PCT/JP1993/000810
Authority: WO
Inventors: Yasuhiro Sakurai
Original assignee: Citizen Watch Co., Ltd.
Priority date: 1992-06-16
Filing date: 1993-06-16
Publication date: 1993-12-23
Also published as: JPH065885A; JP3288430B2

Abstract

A PN junction diode which is provided with a diffusion region (3) of first conductivity type and a diffusion region (5) of second conductivity type, which are arranged in contact with each other on a semiconductor substrate (1). In the surface of the diffusion region (3) which abuts upon the junction of the two regions (3, 5), a low concentration region (11) of the first conductivity type is provided, and the surface of this semiconductor substrate is covered with a protective film (9). No hot carrier is trapped by the protective film (9) upon reverse breakdown. Hence the diode characteristics do not deteriorate with time.

Description

Description PN junction diode and its manufacturing method

The present invention relates to a PN junction diode and a method of manufacturing the same, and more particularly to a configuration of a PN junction diode capable of preventing a change in diode characteristics with time and a method of manufacturing the same. Background art

• The reverse breakdown voltage of a PN junction diode is uniquely determined by the impurity concentration when its junction surface is flat or close to flat, making it easy to control the voltage value. Therefore, PN junction diodes are widely used for reference voltage sources such as regulator circuits and voltage limiters for boost circuits.

The PN junction diode is formed by diffusing a P-type impurity and an N-type impurity into a semiconductor substrate so as to be in contact with each other. At this time, in order to make the bonding surface as close as possible to the plane and to make connection with metal wiring, both the P-type impurity diffusion region and the N-type impurity diffusion region Must be in contact with

Therefore, the simplest configuration of a PN junction diode is to form both diffusion regions near the substrate surface so that they are in lateral contact with each other.

The configuration of such a conventional PN junction diode will be described with reference to FIG. FIG. 8 is a cross-sectional view showing a configuration near a bonding surface of a conventional PN junction diode, and illustration of a connection portion with a metal wiring and the like is omitted.

As shown in the figure, a diffusion region 3 of the first conductivity type and a diffusion region 5 of the second conductivity type are formed near the surface of the semiconductor substrate 1, and both regions are in contact with each other at the bonding surface 7 to form a PN junction. Constitutes a diode. And. The surface of the semiconductor substrate 1 including the bonding surface 7 is covered with a protective film 9 such as an oxide film.

In such a PN junction diode configuration, the entire bonding surface 7 serves as a breakdown surface during reverse breakdown.

That is, the conventional PN junction diode has a configuration in which the breakdown surface is in contact with the protective film 9 on the surface.

Such a PN junction diode is excellent in that the manufacturing process is simple and can be manufactured without changing the manufacturing process of the peripheral semiconductor integrated circuit. However, there was a problem that the diode characteristics gradually changed when the breakdown operation was repeated.

The present invention has been made to solve the above problems, and has as its object to provide a PN junction diode that does not change with time, and to easily manufacture the PN junction diode. Disclosure of the invention

The structure of the PN junction diode according to the present invention covers a first conductivity type diffusion region formed in a semiconductor substrate, a second conductivity type diffusion region in contact with the first conductivity type diffusion region, and the semiconductor substrate. A first conductive type low-concentration region on a surface side of the first conductive type diffusion region which is in contact with a junction surface between the first conductive type diffusion region and the second conductive type diffusion region. It is characterized by having provided.

The method of manufacturing a PN junction diode according to the present invention is characterized in that the following steps (1) to (6) are sequentially performed.

(1) a step of selectively introducing a first conductivity type impurity into a semiconductor substrate,

(2) a step of selectively introducing a second conductivity type impurity so as to be in contact with the region into which the first conductivity type impurity has been introduced;

(3) a step of diffusing these first conductivity type impurities and second conductivity type impurities to form a first conductivity type diffusion region and a second conductivity type diffusion region which are in contact with each other; (4) In the region including the junction surface between the first conductivity type diffusion region and the second conductivity type diffusion region, a smaller amount of the second conductivity type impurity than the first conductivity type impurity introduced earlier. The process of selectively introducing

(5) a step of diffusing this small amount of the second conductivity type impurity to form a first conductivity type low concentration region on the surface side of the first conductivity type diffusion region previously formed;

(6) covering the semiconductor substrate surface with a protective film,

The characteristics of the PN junction diode change gradually, not the characteristics of the diode itself, but the hot carriers generated during reverse breakdown are trapped in the protective film near the breakdown surface, and the protective film is It is gradually charged, and the electric field reaches the PN junction surface.

However, in the PN junction diode according to the present invention, in the region on the surface side close to the protective film, no breakdown occurs because the diffusion region of the first conductivity type has a low concentration, and the breakdown surface is the protective film. Away from

, PN junction only. Therefore, the hot carrier is not trapped by the protective film, and the diode characteristics do not change with time. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view showing a configuration near a bonding surface of a PN junction diode according to one embodiment of the present invention.

2 to 7 are cross-sectional views similar to FIG. 1 showing respective steps of one embodiment of a method for manufacturing a PN junction diode according to the present invention.

FIG. 8 is a cross-sectional view showing a configuration near a bonding surface of a conventional PN junction diode. BEST MODE FOR CARRYING OUT THE INVENTION

In order to explain the present invention in more detail, embodiments of the present invention will be described with reference to the accompanying drawings.

First, the structure of a PN junction diode according to the present invention will be described with reference to FIG. FIG. 1 shows a PN junction die according to an embodiment of the present invention. FIG. 9 is a cross-sectional view showing a configuration near a joint surface of a groove, and portions corresponding to FIG. 8 are denoted by the same reference numerals. It should be noted that the illustration of the connection portion with the metal wiring is omitted.

As shown in FIG. 1, the PN junction diode has a diffusion region 3 of the first conductivity type (for example, P type) and a diffusion region 5 of the second conductivity type (for example, N type) near the surface of the semiconductor substrate 1. And a diffusion region of the first conductivity type near the junction surface between the diffusion region 3 of the first conductivity type and the diffusion region 5 of the second conductivity type. A low-concentration region 11 of the first conductivity type having the same conductivity type as that of 3 and a low impurity concentration is provided.

The low concentration region 11 of the first conductivity type is in contact with the diffusion region 5 of the second conductivity type at the first bonding surface 13. On the other hand, the diffusion region 3 of the first conductivity type having a high impurity concentration is in contact with the diffusion region 5 of the second conductivity type at the second bonding surface 14.

Since the reverse breakdown of the PN junction occurs at a lower voltage as the impurity concentration increases, in the PN junction diode of this configuration, when the applied voltage increases, the second junction surface 14 Breakdown occurs. After the breakdown occurs on the second bonding surface 14, no breakdown occurs on the first bonding surface 13 even if the voltage further increases.

The reason is that when a breakdown occurs at the second junction surface 14 and current starts flowing, a voltage drop is caused by the internal resistance between the diffusion region 3 of the first conductivity type and the diffusion region 5 of the second conductivity type. As a result, the voltage mainly applied to the second bonding surface 14 and the first bonding surface 13 until then is changed to the diffusion region 3 of the first conductivity type and the diffusion region 5 of the second conductivity type. This is because a voltage causing a breakdown is not applied to the first bonding surface 13 because of the dispersion inside.

As described above, if the breakdown surface of the reverse breakdown is separated from the protective film 9 on the surface, the hot carrier is not trapped by the protective film 9, and thus the diode characteristics do not change with time.

In the PN junction diode with the configuration shown in Fig. 1, the break The down surface is a second bonding surface 14, and the second bonding surface 14 is not in contact with the protective film 9 and is separated therefrom. Therefore, the PN junction diode thus configured does not change its diode characteristics even when the breakdown operation is repeated.

Next, an embodiment of a method for manufacturing the PN junction diode will be described. 2 to 7 are cross-sectional views showing each step in the method for manufacturing a PN junction diode according to the present invention. However, these figures also show only the vicinity of the junction surface of the PN junction diode, and the illustration of the connection portion with the metal wiring is omitted.

First, as shown in FIG. 2, a masking material 15 such as a resist, which is a photosensitive material, is selectively formed on the surface of the semiconductor substrate 1. Then, the first conductivity type impurity 17 is introduced into the semiconductor substrate 1 by an ion implantation method using the masking material 15 as a blocking film for ion implantation.

Thereafter, the masking material 15 is removed, and a resist is formed on the surface of the semiconductor substrate 1 so that a region adjacent to the region into which the impurity 17 of the first conductivity type is introduced becomes an opening as shown in FIG. The masking material 15 is selectively formed.

Then, an impurity 19 of the second conductivity type is introduced into the semiconductor substrate 1 by an ion implantation method.

After that, the masking material 15 used as a blocking film for the ion implantation is removed and a heat treatment is performed. As shown in FIG. 4, impurities 17 of the first conductivity type and impurities 19 of the second conductivity type are removed. To form a first conductivity type diffusion region 3 and a second conductivity type diffusion region 5 that are in contact with each other.

At this stage, the bonding surface 7 between the diffusion region 3 of the first conductivity type and the diffusion region 5 of the second conductivity type has reached the surface of the semiconductor substrate 1.

Next, as shown in FIG. 5, a masking material 15 such as a resist is selectively formed on the surface of the semiconductor substrate 1 so that a region including the bonding surface 7 becomes an opening. Then, a small amount of the second conductivity type impurity 21, which is the first conductivity type impurity 17 previously implanted by the ion implantation method, is introduced into the semiconductor substrate 1 in the opening of the masking material 15. Thereafter, the masking material 15 used as the ion implantation blocking film is removed and a heat treatment is performed to diffuse this small amount of the second conductivity type impurity 21. As a result, as shown in FIG. 6, a low concentration region 11 of the first conductivity type having a lower impurity concentration than the diffusion region 3 of the first conductivity type is formed on the surface side of the diffusion region 3 of the first conductivity type. I do.

As a result, the second bonding surface 14 between the diffusion region 3 of the first conductivity type and the diffusion region 5 of the second conductivity type is only inside the semiconductor substrate 1, and the surface portion is the first conductivity type. The first junction surface 13 is a junction surface between the low-concentration region 11 and the diffusion region of the second conductivity type.

Although a small amount of the second conductivity type impurity 21 is also introduced into the diffusion region 5 of the second conductivity type, it can be neglected because it is small and of the same conductivity type.

Next, as shown in FIG. 7, the surface of the semiconductor substrate 1 is covered with a protective film 9 such as silicon dioxide to complete a PN junction diode. Description of subsequent steps such as connection with metal wiring is omitted.

By such a manufacturing method, the PN junction diode according to the present invention can be easily manufactured.

A slight change was made, such as forming a silicon dioxide film with a thickness of several tens of nm on the surface of the semiconductor substrate 1 in advance, and using the silicon dioxide film as a buffer for ion implantation. It goes without saying that the PN junction diode of the present invention can be manufactured even if it is carried out. . Industrial Applicability

The PN junction diode according to the present invention prevents the hot carrier from being trapped in the protective film by separating the break-down surface of the PN junction from the protective film on the surface of the semiconductor substrate. Can be eliminated. Therefore, if it is used for a reference voltage source such as a regulator or a limiter of a booster circuit, stable operation can be performed for a long time, and the effect is extremely large.

Claims

The scope of the claims

1. A first conductivity type diffusion region formed on the semiconductor substrate, a second conductivity type diffusion region formed on the semiconductor substrate so as to be in contact with the first conductivity type diffusion region, and a surface of the semiconductor substrate. A protective film, and a low concentration of the first conductivity type on a surface side of the first conductivity type diffusion region which is in contact with a bonding surface between the first conductivity type diffusion region and the second conductivity type diffusion region. A PN junction diode characterized by having a region.

2. a step of selectively introducing an impurity of the first conductivity type into the semiconductor substrate, and selectively introducing an impurity of the second conductivity type so as to be in contact with the region into which the impurity of the first conductivity type has been introduced;

Diffusing the first conductivity type impurity and the second conductivity type impurity introduced into the semiconductor substrate to form a first conductivity type diffusion region and a second conductivity type diffusion region which are in contact with each other;

An impurity of the second conductivity type, which is smaller than the impurity of the first conductivity type, is selectively introduced into a region including a junction surface between the diffusion region of the first conductivity type and the diffusion region of the second conductivity type. The process of

Forming a low concentration region of the first conductivity type on the surface of the diffusion region of the first conductivity type by diffusing the small amount of impurities of the second conductivity type; and covering the semiconductor substrate surface with a protective film. When

A method for producing a PN junction diode, comprising: