JPH0474478A - Diode - Google Patents

Abstract

PURPOSE:To increase dielectric strength in the reverse direction, and to eliminate the parasitic movement by forming a high-concentration P-type diffusion layer region to wrap the first low-concentration N-type epitaxial layer, and then by forming the second N-type epitaxial layer to wrap the P-type diffusion region, electrically connecting, and making it into an anode. CONSTITUTION:By connecting a P-type diffusion region 16 with an N-type diffusion region 17, a wiring electrode 19 is made. By connecting a N-type diffusion region 18 with a wiring region 20, a cathode electrode is made. The dielectric strength of a diode equals to the dielectric strength of PN junction of an N-type diffusion epitaxial layer 14, a P-type furied diffusion region 11, and the P-type diffusion region 16. When a diode is made to move to the forward direction, most of electrons are injected from the N-type epitaxial layer 14 in the highly concentrated P-type buried diffusion region 11, and in the P-type diffusion region 16. These electrons are re-coupled there, and are eliminated, and then they make anode current. It never occurs that the electric current flowing in a diode generates the parasitic effect of flowing into other portions.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a diode used in a semiconductor device.

BACKGROUND OF THE INVENTION FIG. 2 shows a cross-sectional view of a diode conventionally used in semiconductor devices.

In FIG. 2, 1 is a P-type semiconductor substrate, 2 is an N-type buried diffusion region formed on the P-type semiconductor substrate 1, 3 is an N-type epitaxial layer formed on the N-type buried diffusion region 2, and 4 is an N-type buried diffusion region formed on the N-type buried diffusion region 2. is N
A P-type isolation diffusion region 5 penetrates the type epitaxial layer 3 and reaches the P-type semiconductor substrate 1; 6 is a P-type diffusion region which becomes the base of the formed transistor; 6 is an N-type diffusion region which becomes the emitter of the transistor formed in the P-type diffusion region 5;
7 is an N-type diffusion region that connects the collector contact of the transistor, which is usually formed at the same time as the N-type diffusion region 6; 8 is a silicon oxide film; 9 and 10 are wiring electrodes; the wiring electrode 10 is connected to the N-type diffusion region 6; , the wiring electrode 9 is a P-type expanded area 5
and the N-type diffusion region 7. The P-type diffusion region 5, which becomes the base of the transistor, the N-type buried diffusion region 2, which becomes the collector, and the N-type epitaxial layer 3 form the anode of the diode, and the N-type diffusion region 6, which becomes the emitter of the transistor, forms the diode's anode. It becomes a cathode. The wiring electrodes 9 and 10 serve as the anode and cathode wiring electrodes of the diode, respectively.

The breakdown voltage of this type of integrated circuit diode is the same as the base-emitter breakdown voltage of a transistor, and in a normal semiconductor integrated circuit, it is about 6 to 8V, although it depends on the process.

Problems to be Solved by the Invention In terms of circuit design, a diode having a withstand voltage higher than that obtained with conventionally used diodes is sometimes required. By the way, it is possible to construct a diode if there is a PN junction, but suppose that in an attempt to construct a diode with a high breakdown voltage, for example, the P-type diffusion region 5 in FIG. 2 is used as an anode and the N-type epitaxial layer 3 is used as a cathode.

Since the withstand voltage of this junction is determined by the withstand voltage between the base and collector of the transistor, a voltage of 30 V or more can usually be easily secured.

However, in this type of diode, when operated in the forward direction, holes injected into the N-type epitaxial layer 3 from the P-type diffusion region 5 flow into the grounded P-type semiconductor substrate 1, which is a so-called parasitic operation. exist. This has the disadvantage that the cathode current is less than the anode current.

Means for Solving the Problem In order to solve this problem, the diode of the present invention is provided by forming a highly doped P-type diffusion region surrounding a first low-concentration N-type epitaxial layer serving as a cathode;
A second N-type epitaxial layer is formed to surround the type diffusion region, and the P-type diffusion region and the second N-type epitaxial layer are electrically connected to form an anode.

Effect By adopting this configuration, electrons injected from the N-type region that becomes the cathode into the P-type head region will either disappear in the P-type head region with high concentration, or even if they reach the second N-type region. Since it is an anode current, there is no undesirable parasitic operation.
It becomes possible to increase the withstand voltage of the first N-type diffusion region and the P-type diffusion region that form the PN junction of the diode.

Embodiment FIG. 1 shows an embodiment of a diode used in a semiconductor device according to the present invention. In FIG. 1, ■ is a P-type semiconductor substrate, 2 is an N-type buried diffusion region formed on the P-type semiconductor substrate 1, and 11 is a P-type buried diffusion region formed on the N-type buried diffusion region 2. A region 12 is a P-type semiconductor substrate 1 formed on the P-type semiconductor substrate 1.
This is a P-type buried isolation diffusion region similar to type buried diffusion region 11.

After the above regions are formed, the N-type epitaxial layer 13
．． 14 will be grown. The P type isolation diffusion region 15 formed from the surface is in contact with the P type buried isolation diffusion region 12, and the N type buried diffusion region 2 and the N type epitaxial layer 13.14 are in contact with the P type semiconductor substrate 1. P-type isolation diffusion region 15. They are separated into islands by P-type buried isolation and diffusion regions 12. The P-type diffusion region 16 is a deep diffusion region extending from the surface of the N-type epitaxial layer 13 to the P-type buried diffusion region 11, and is formed to surround the N-type epitaxial region 14. It can be formed simultaneously with the P-type isolation diffusion region 15. N
Type diffusion regions 17 and 18 are diffusion layers for ohmically extracting resistance from N type epitaxial layers 13 and 14, respectively.

The diode in this embodiment has a P type diffusion region 16 and an N
The type diffusion region 17 is connected with a wiring electrode 19 to serve as an anode electrode, and the N type diffusion region 18 is connected with a wiring electrode 20 to serve as a cathode electrode.

In such a configuration, the breakdown voltage of the diode is determined by the N-type epitaxial layer 14 and the P-type buried diffusion region 11. This is the breakdown voltage of the PN junction formed by the P-type diffusion region 16. The impurity concentration of the N-type epitaxial layer 14 is usually 5×10 14 cm −3 to 5 due to the requirement of forming the collector of a transistor.
Since approximately ×10150ITl-3 is used, 5
A breakdown voltage of 0 to 100V can be easily obtained. Further, when the diode is operated in the forward direction, the highly doped P-type buried diffusion region 11 . Most of the electrons injected into the P-type diffusion region 16 recombine and disappear, becoming an anode current. Electrons that have survived to the N-type buried diffusion region 2 and the N-type epitaxial layer 13 also become an anode current because these regions are connected to the wiring electrode 19 which is an anode electrode.

On the other hand, as a matter of course, all the holes injected into the N-type epitaxial layer 14 from the P-type buried diffusion region 11° and the P-type diffusion region 16 become cathode current. In this way, the current flowing through the diode does not have the parasitic effect of escaping to other parts.

Effects of the Invention According to the present invention, a diode having a high reverse breakdown voltage and good characteristics without parasitic operation can be provided without using a complicated manufacturing process.

[Brief explanation of the drawing]

FIG. 1 is a perspective sectional view of a diode according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional diode. 1... P-type semiconductor substrate, 2... N-type buried diffusion region, 11... P-type buried diffusion region, 12
...P-type buried isolation diffusion region, 13.14...
...N type epitaxial layer, 15...P type isolation diffusion region, 16...P type diffusion region, 17.1
8...N-type diffusion region, 19.20...
Wiring electrode.

Claims (1)

[Claims] a P-type semiconductor substrate; an N-type buried diffusion region formed on the P-type semiconductor substrate; a P-type buried isolation diffusion region formed on the N-type buried diffusion region and in the N-type buried diffusion region; The grown N-type epitaxial layer and the P-type diffusion that penetrates the N-type epitaxial layer, reaches the P-type buried diffusion region, and becomes an anode formed by surrounding a part of the N-type epitaxial layer. a P-type isolation diffusion region penetrating the N-type epitaxial layer to reach the P-type buried isolation diffusion region and surrounding the N-type epitaxial layer; A first epitaxial region separated by the P-type diffusion region, and a second N-type epitaxial region sandwiched between the P-type isolation diffusion region and the P-type diffusion region, and the P-type diffusion region and the second N-type epitaxial region are electrically connected to each other to serve as an anode, and the first N-type epitaxial region is used as a cathode.