JPS5821865A - Constant-current diode - Google Patents

Abstract

PURPOSE:To increase the distance between both electrode metals of a constant-current diode by isolating and forming part of a diffused layer becoming a gate region and a diffused layer becoming a source region so as to alternately intrude in a circumferential direction to each other and forming a stepwise difference between a connecting electrode metal on the region and a drain electrode metal. CONSTITUTION:On a P type semiconductor substrate 21 is grown an N type epitaxial layer 22 having a flat raised top shape, in the layer 22 are further formed an annular P type diffused layer 23 becoming a gate region and an N type diffused layer 24 becoming a source region, and at the center is formed an N type diffused layer 24 becoming a drain region. A plurality of rectangular P type diffused layers 23a are formed at the prescribed interval circumferentially on the layer 23, thereby forming a P type diffused layer 23b passing through the substrate 21 connected to the layer 23a. An N type diffused layer 25 formed in the adjacent region formed with the layers 23, 23a and 23b is formed of an N type diffused layer 24a corresponding to the layers 23a, 23b and an N type diffused layer 24b extending to the substrate 21. In this manner, an electrode metal 27 and an annular connecting metal 28 are formed through an insulating layer 26 such as an SiO2 on the substrate 21, the layers 24b, 23b, thereby completing a constant- current diode having stepwise difference between both electrodes.

Description

[Detailed description of the invention] This invention relates to an electrode structure that can prevent short-circuit accidents between polar metals.

FIG. 1 shows a schematic configuration of a constant current diode.

In the figure, an N epitaxial layer 2 is grown on a P semiconductor substrate 1, and in this epitaxial layer 2, a P diffusion layer becomes a gate region, and an N diffusion layer 4 becomes a source region.
And an N+4- diffusion layer 5, which becomes a drain region, is formed by a generally well-known selective diffusion method. Then, diffusion is performed from one main surface of the substrate 1 to form an isolation diffusion layer 6, which is separated into islands.

An electrode metal 7 is formed on one main surface of the substrate 1, and an insulating layer 8 made of a SiO2 film or the like on the P diffusion layer 3 is formed on the other main surface.
An electrode metal 9 is placed on the N diffusion layer 5 overlapping with one end, and the P diffusion layer 6, the N++ diffusion layer and the P diffusion layer 3 are also placed on the N diffusion layer 5.
Connecting electrode metals 10 for short-circuiting are respectively provided.

In the above configuration, in order to obtain predetermined electrical characteristics as a constant current diode, the channel length directly under the P+ diffusion layer 3 reaching the gate region is inevitably restricted, and the electrode metal on the N diffusion layer 5 is restricted. 9 and the connecting electrode metal 10 are 100
The distance was extremely close to about 150 μm, which caused short circuit accidents and other problems in terms of reliability. In particular, from the viewpoint of improving productivity, it is desirable to make the leads 11 and 12 axial as shown in FIG. 2, but in this case, the electrode metals 9 and 10 formed on the semiconductor pellet 13 are close to each other. In order to do so, the lead 11 must be precisely positioned and fixed at a predetermined position with strict dimensional accuracy, which is one of the problems in improving productivity.

The present invention has been made based on the above-mentioned circumstances, and has a pattern shape in which a part of the P diffusion layer that will become the gate region and the N++ diffusion layer that will become the source region are interwoven with each other. It is an object of the present invention to provide a constant current diode in which a step is provided between an electrode metal and an electrode metal on a drain region, so that the distance between both electrode metals can be made larger than in the past.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a perspective view showing the first embodiment of the present invention, and FIG. 4 is a sectional view taken along the X-Y-Z line in FIG. 3.

In the figure, a mountain-shaped N- epitaxial layer 22 with a flat top surface is grown on a P semiconductor substrate 21, and within this epitaxial layer 22 are formed an annular P diffusion layer 23 that will become a gate region and an N++ diffusion layer that will become a source region. A plurality of strip-shaped P diffusion layers 23a are formed in the center of the layer 24 at predetermined intervals in the circumferential direction of the drain annular P diffusion layer 23, and the P diffusion layers 23a are further formed in series with the diffusion layer 23a. A P diffusion layer 23b communicating with the semiconductor substrate 21 is formed.

The annular P diffusion layer 23, the strip-shaped P diffusion layers 23a and 2
The N diffusion layer 25 formed in the adjacent region formed by the N diffusion layer 3b corresponds to the P diffusion layer 23a and 23b.
Diffusion layer 2'4a and P N extending by 21 dimensions of semiconductor substrate
Therefore, the electrode metal 27 and the annular connection metal 28 are connected to the semiconductor substrate 21, N through the insulating layer 26 such as 5i02, and the diffusion layer 24b.
By providing the diffusion layer 24b% on the P diffusion layer 23b, a constant current diode with a step between both electrodes is completed as shown in the figure.

With the above configuration, the electrode metal 27 and the annular connection metal 28
Since a step is provided between the two electrodes, it is possible to maintain a relatively large distance between the two electrodes, thereby avoiding the possibility of a short circuit accident or the like. Therefore, the productivity of axial type constant current diodes can be improved. Furthermore, it is not necessary to form a P isolation diffusion layer as in the past, and the channel width (radius from the center of the drain region to the gate region IJ12t) can be selected relatively freely, which greatly contributes to the realization of an axial type constant current diode. It is.

FIG. 5 is a perspective view showing a second embodiment of the invention.

In this embodiment, the P++ semiconductor substrate 2 corresponds to the strip-shaped P+ diffusion layers 23a and 23b extending from the annular P diffusion layer 23.
The corner part of 1 is cut out to form a short circuit part 29,
It can be expected to have the same effects as the first embodiment and to simplify the manufacturing process.

In the figure, the same parts as in the first embodiment are given the same reference numerals, and detailed explanation thereof will be omitted.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of the structure of a conventional constant current diode, FIG. 2 is a schematic configuration diagram of a constant current diode formed in an axial type using a semiconductor pellet with the above configuration, and FIG. 3 is a schematic configuration diagram showing an example of the structure of a conventional constant current diode. , FIG. 4 is a perspective view of a semiconductor pellet of a constant current diode showing the first embodiment of the present invention, FIG. 4 is a sectional view taken along the x-y-z line of FIG. 3, and FIG. 2
FIG. 3 is a perspective view of a semiconductor pellet similar to that shown in FIG. 3, showing an embodiment of the present invention. 21...P semiconductor substrate, 22°...N-epitaxial layer, 23...annular P diffusion layer, 24...N diffusion layer, 25...N diffusion layer, 2
6... Insulating layer, 27... Electrode metal, 28...
... Electrode metal for annular connection, 29 ... Short circuit part.

Claims (1)

[Claims] A part of the diffusion layer that will become the gate region and a diffusion layer that will become the source region are formed separately so as to intersect alternately in the circumferential direction, and a part of the diffusion layer that will become the gate region and a diffusion layer that will become the source region are formed separately so that they intersect with each other in the circumferential direction, and between the connecting electrode metal on the gate region and the source region and the electrode metal on the drain region. A constant current diode characterized by having a step.