JPH0370908B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to terminal electronic devices such as computers.
The present invention relates to a diode that has both low forward voltage drop characteristics and relatively high reverse blocking voltage characteristics, which are desired for rectifier diodes used in low voltage, high current stabilized DC power supplies accompanying the use of ICs.

[Prior art]

In a shot barrier diode (hereinafter abbreviated as SBD) using an N-type silicon substrate as a diode structure, a P-type impurity diffusion region is provided on the silicon substrate surface below the shot contact, and the shot barrier diode is Forming a high voltage SBD that has both low forward voltage drop characteristics based on PN junctions and high reverse blocking voltage characteristics based on PN junctions has already been proposed, for example, in Solid State Electronics 26 ('83).
It is known from the literature P491-493.

[Problem that the invention seeks to solve]

As mentioned above, it can be called an integrated type.
The SBD has a structure as shown in the cross-sectional view of the main part in FIG.

In this SBD, when a forward voltage is applied, that is, positive to the anode electrode 3 and negative to the cathode electrode 4, the current mainly flows to the n region 1 where the weir layer voltage is low.
It flows through the shot barrier region 5 which is in contact with the surface 8 of the pump, and does not flow into the P-type region 2 where the weir layer voltage is high. When reverse voltage is applied, the Pn junction 6 increases as the voltage increases.
A space charge region 7a shown by a dotted line completely covers the n region surface 8, and the overall breakdown voltage is due to breakdown at the space charge region edge 7b due to the P-shaped annular region 9 outside the space charge region 7a. It becomes decided.

In such an integrated SBD, if reverse breakdown voltage is important, the P-type regions 2 must be arranged densely to some extent so that the space charge region 7a completely covers the n-region surface 8.
In this case, the area ratio of the SBD conduction region 5 when applying a forward voltage becomes smaller, resulting in a higher weir layer voltage and a lower forward voltage drop characteristic.
The advantages of SBD are diminished. On the other hand, if we place too much emphasis on low forward voltage drop characteristics and make the P-type region 2 sparse,
When a reverse voltage is applied, the space charge region 7a becomes the n region surface 8.
Since the P-type region 2 is not completely covered, there is no point in providing the P-type region 2.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the above-mentioned drawbacks and provide a high breakdown voltage SBD with a forward voltage drop as small as possible and a reverse blocking voltage as high as possible.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention devises the shape and arrangement of the P-type regions, so that the space charge regions that spread out from the Pn junction of each P-type region when applied in opposite directions do not overlap each other. Moreover, this is based on the discovery of a dimensional shape that has a particularly remarkable effect among the dimensional relationships that cover the entire surface of the n-region surface 8 when a predetermined reverse voltage is applied.

According to the present invention, it is a P-shaped region that is a regular hexagon having a center at each vertex of an equilateral triangle arranged in a hexagonal dense (or equilateral triangular dense) manner, and has a protrusion at each vertex of each regular hexagon. This is obtained by disposing it under the shot barrier area.

[Function and Examples]

An embodiment of the present invention will be described in detail below with reference to the drawings.

1 to 3 are diagrams showing a high voltage shot barrier diode of the present invention. In these figures, the same reference numerals indicate the same parts.

FIG. 1 shows a high voltage SBD according to the present invention,
FIG. 2 is a top view of the shot barrier electrode 16, which is the anode electrode, seen through from above. In the shot barrier region where the P-type regular hexagonal region 13 provided on the surface of the n-type silicon substrate below the shot barrier electrode 16 is in contact with the shot barrier electrode and silicon, space charges extend when opposite voltages are applied to each other. The distance is slightly shorter than twice the length of the area, and as will be described later, it is uniformly distributed according to a predetermined arrangement, and furthermore, the shot spot
A P-shaped annular region 14 is provided at the outer boundary of the barrier region. The outer region 15 is a region of a surface protection film such as a silicon oxide film. The distance between the P-shaped regular hexagonal region 13 and the P-shaped annular region 14 is
In order not to make the shape of the regular hexagonal regions 13 unnecessarily complicated, the spacing between the regular hexagonal regions 13 can be varied within a range of twice the length of the space charge region. This allows the space charge region to cover the entire shot barrier region when a reverse voltage is applied, and the reverse blocking voltage is due to breakdown at the edge of the space charge region extending outside the P-shaped annular region. It will be decided in due course.

Next, the shape and arrangement of the P-shaped regular hexagonal area will be described in more detail. FIG. 2 is a cross-sectional view of the high voltage shot barrier diode shown in FIG. 1. Reference numeral 16 is a shot barrier electrode serving as an anode, and reference numeral 17 is a cathode electrode. In FIG. 2, if the avalanche breakdown voltage or Zener breakdown voltage of the Pn junction determined by the resistivity ρ of the n-type high-resistivity silicon layer 12 laminated on the silicon n-type low-resistivity substrate 11 is Vz,
When a reverse voltage is applied, the P-type regular hexagonal area 13
It is known that the space charge region distance L (microns) extending from the Pn junction is approximated as L=0.53√·. Therefore, if the distance between the P-shaped regular hexagonal areas 13 suitable for the purpose of the present invention is 2L, then L≦
Although it is 0.53√・, the safety factor is actually expected to be 0.95, and by multiplying this, it is possible to make L=0.50√・, and this is preferable. The upper surface shape of this P-shaped regular hexagonal region 13 is a regular hexagonal shape 13b as shown in the enlarged view of FIG.
As shown in the figure, the centers are arranged at the vertices K ₁ , K ₂ , and K ₃ of the equilateral triangles K arranged in a hexagonal dense (or equilateral triangular dense) arrangement obtained by densely arranging equilateral triangles. Therefore, the mutual overlap of the space charge regions on the silicon surface can be minimized as shown by the dotted line in FIG. It is desirable that the size of the P-shaped regular hexagonal region 13b (the radius of the circumscribed circle is d) be as small as possible. For example, from the viewpoint of dimensional accuracy achieved in the photo process in the manufacture of semiconductor devices, it is optimal to set it to 3 to 5 microns. It is.

The mutual center distance of regular hexagonal areas is D (microns)
Then, D can be determined as follows. For example, D=2L+2d×√3/2=2×0.50√·Vz+2×3×√3/2, and if the resistivity ρ and breakdown voltage Vz of silicon are determined, D can be found.
By the way, if the maximum space charge regions are arranged so that the overlap of the maximum space charge regions is reduced in this way, the top surface shape of the maximum space charge region end of the regular hexagonal P-shaped region will be as shown by the dotted line in FIG. As shown in the figure, it has been found that there are areas where the three dotted lines do not overlap near the intersection E. It has been found that in order to still prevent this while still meeting the purpose of the present invention, it is effective to add a protrusion AB of length l facing outward B to each corner A of each regular hexagonal area 13a. It goes without saying that this protrusion AB must be formed not only at the corners of the regular hexagonal area 13a but also at all corners of the regular hexagonal area except for the outermost periphery provided under the shot barrier area.

If the length of this protrusion AB from the corner A of the regular hexagon to the tip B of the protrusion is l, then l≧AE−BE=AE−L=2/√3L−L≒0.155L. Actually, l≈0.16L is preferable. The width of the protrusion may be as small as possible, for example 1 micron can be selected.

The protrusion shape determined in this way is shown in the regular hexagonal area 13a in FIG.

It has a P-shaped regular hexagonal area with this shape.
When a reverse voltage is applied to the SBD, the entire area of the SBD section is covered with a space charge area. Accordingly
A high reverse blocking voltage can be obtained based on the Pn junction. In addition, since the P-type regions 13a are arranged so that the center of _C1 is located at each vertex of an equilateral triangle that is tightly packed into a hexagonal shape, there is almost no mutual overlap when the space charge regions are expanded to their maximum. As a result, the total area of the regular hexagonal region is minimized for a given reverse voltage, so that the weir layer voltage when a forward voltage is applied is also minimized.

〔Effect of the invention〕

According to the present invention, the shape of the impurity diffusion region disposed in the barrier region in the shot barrier diode is a regular hexagon having a center at each vertex of an equilateral triangle arranged in a dense hexagonal arrangement, and Since each vertex of the diode is provided with a protrusion such that the space charge region completely covers the shot barrier region when a breakdown voltage is applied, a shot barrier diode with a small forward voltage drop and a high reverse blocking voltage can be obtained. I can do it.

[Brief explanation of drawings]

Figure 1 is a top view showing one embodiment of the present invention, Figure 2 is a top view showing one embodiment of the present invention;
This figure is a sectional view of the same as above, FIG. 3 is an enlarged view of the regular hexagonal area of the same as above, and FIG. 4 is a sectional view of a main part of a conventional integrated shot barrier diode. 13... regular hexagonal area, 14... annular area, 16...
Shotki barrier electrode, 17... cathode electrode,
AB...protrusion.

Claims (1)

[Claims] 1. A plurality of impurity diffusion regions of a conductivity type different from that of the semiconductor are provided on the semiconductor surface under the shot barrier region, and the mutual spacing between each region is equal to the space charge region extending outside the Pn junction when a breakdown voltage is applied. In the impurity diffusion region arranged so as to be shorter than twice the length, the shape of the impurity diffusion region is a regular hexagon having a center at each point of an equilateral triangle arranged densely,
A high voltage shot barrier diode, characterized in that each point of each regular hexagon is provided with a protrusion such that a space charge region completely covers the shot barrier region when a breakdown voltage is applied.