JPS6188560A - High withstanding-voltage schottky-barrier-diode - Google Patents

Abstract

PURPOSE:To obtain a diode having high reverse-blocking voltage by constituting a plurality of P type regions in dense equilateral hexagons when a P type annular region is formed to the surface layer section of an N type Si layer, the outside of the annular region is surrounded by an SiO2 film, the P type regions shaped into an N type layer surrounded by the annular region and these P type regions are coated with a Schottky barrier electrode. CONSTITUTION:An N type layer 12 is grown on an N<+> type Si substrate 11, on the back thereof a cathode electrode 17 is applied, a P type annular region 14 is diffused and shaped onto the surface layer section of the layer 12, and the outside of the region 14 is surrounded by an SiO2 film 15. A plurality of P type regions 13 are diffused and formed onto the surface layer section of the layer 12 surrounded by the region 14, and a Schottky barrier electrode 16 as an anode electrode is applied onto the surface containing these regions 13, but the regions 13 are shaped as follows at that time. That is, all of these regions 13 take an equilateral hexagon, spaced among these regions are made shorter than twice of the length of a space region extending when reverse voltage is applied, and projecting sections are formed previously at the apices of several triangle. Accordingly, a space charge region on an application in the opposite direction is extended over the whole surface of the layer 12, and reverse withstanding voltage is increased.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is desirable for rectifying diodes used in low voltage, high current DC stabilized power supplies accompanying the conversion of terminal electronic devices such as conovulators to PC. This relates to a diode that has both low forward voltage drop characteristics and relatively high reverse blocking voltage characteristics.

[Prior art]

In a Schottky 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 Schottky contact, and the Schottky barrier Forming a high breakdown 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 developed, for example, in solid state electronics (5solid 5tate 1electro
nics) 26 ('83) P491-493.

[Problem that the invention seeks to solve]

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

In this SBD, the forward voltage is
When the electrode 3 is applied positively and the cathode electrode 4 is applied negatively,
The current mainly flows through the Schottky barrier region 5 which is in contact with the surface 8 of the n region 1 where the weir layer voltage is low, and flows through the Schottky barrier region 5 which is in contact with the surface 8 of the n region 1 where the weir layer voltage is high.
It does not flow into shadow area 2. When a voltage is applied in the reverse direction, as the voltage increases, the space charge region 7a, which is shown by a single dotted line, spreads toward the n region l side of Pn' 4 and 6 and completely covers the n region surface 8.
The overall breakdown voltage is determined by the breakdown at the space charge region edge 7b due to the P-shaped annular region 9 outside.

In such an integrated SBD, if emphasis is placed on the reverse breakdown voltage, it is necessary to arrange the P shadow regions 2 somewhat densely so that the space charge region ma covers the entire n region surface 8. In this case, the area ratio of the SBD conduction region 5 when applying a forward voltage becomes smaller, so that the weir layer voltage increases, and the advantage of the SBD of having a low forward voltage drop characteristic is lost. On the other hand, if too much emphasis is placed on low forward voltage drop characteristics and the P shadow region 2 is made sparse, the space charge region 7a will not completely cover the n region surface 8 when a reverse voltage is applied, and the purpose of providing the P shadow region 2 will be lost. It disappears.

Therefore, an object of the present invention is to improve the above-mentioned drawbacks and to develop a high-voltage SBD with as little exposure voltage drop and high reverse blocking voltage as possible.
The goal is to provide the following.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides five points in the P shadow area.
By devising the shape and arrangement, the space charge regions that spread from the Pni5 of each P shadow region when applied in the opposite direction do not overlap each other, and moreover, when a predetermined reverse voltage is applied, the entire surface of the n region surface 8 is covered. This is based on the discovery of dimensions and shapes that have a particularly remarkable effect in the midst of significant dimensional relationships.

According to the present invention, the P shadow region 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. is obtained by disposing the area under the Schottky barrier region.

[Function and Examples]

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

FIG. 1 shows wave distortion. FIG. 3 shows a high breakdown voltage Schottky barrier diode of the present invention. In these figures,
The same symbols indicate the same parts.

FIG. 1 is a top view of a high voltage SBD according to the present invention, looking through a Schottky barrier electrode 16, which is an anode electrode thereof. In the Schottky barrier region where the P-carved hexagonal region 13 provided on the surface of the n-type silicon substrate under the Schottky barrier electrode 16 contacts the Schottky barrier electrode and silicon, a space charge region extends when reverse voltages are applied to each other. are uniformly distributed at a distance of slightly less than twice the length and according to a predetermined arrangement as will be described later, and furthermore, a P-shaped annular region 14 is provided at the outer boundary of the Schottky barrier region. There is. The outer region 15 is a region of a surface peritoneal membrane such as a silicon oxide film. P carved hexagonal area 13 and P-shaped annular area 14
In order not to make the shape of the regular hexagonal regions 13 more complicated than necessary, the distance between the regular hexagonal regions 13 should be different from the distance between the regular hexagonal regions 13 within twice the length of the space charge region. can be set. This allows the space charge region to cover the entire Schottky barrier region when a reverse voltage is applied, and the reverse blocking voltage is determined by the breakdown at the edge of the space charge region extending outside the P-shaped annular region. It turns out.

Next, the shape and arrangement of the P carving hexagonal area will be described in more detail. FIG. 2 is a cross-sectional view of the high voltage Schottky barrier diode shown in FIG. 1. Reference numeral 16 is a Schottky rear electrode serving as an anode, and reference numeral 1
7 is a cathode electrode. In Figure 2, n of silicon
Let Vz be 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 low-resistivity substrate 11. However, the space charge region distance L (microns) extending from the Pn junction is L =
It is known that it is approximated as 0.53 r'7. Therefore, if the distance between the P carving hexagonal areas 13 suitable for the purpose of the present invention is 2L, L≦0.5367W, but in reality The safety factor is expected to be 0.95, and multiplied by this, L
-o, :a(fii), and this is preferable.

The upper surface shape of this P carved hexagonal area 13 is a regular hexagon 13b as shown in the enlarged view of FIG. 3, and moreover, as shown in FIG. The overlap of the space charge regions on the silicon surface can be expressed as the black center in Figure 3. can be minimized as shown in .

It is desirable that the size of the P carved hexagonal region 13b (where d is the radius of the circumscribed circle) is as small as possible. For example, from the dimensional accuracy achieved in the photo process required for manufacturing semi-dedicated elements, it is 3 to 5 microns. It is best to do so.

If the mutual center distance of the regular hexagonal regions is D (microns), and 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 upper surface shape of the maximum space charge region end of the regular hexagonal P shadow 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 dots do not overlap near the intersection E.

It has been found that in order to prevent this problem while still meeting the purpose of the present invention, it is effective to add a protrusion AB having a length t facing outward B to each corner Al of each regular hexagonal area 13a. It goes without saying that this projection AB must be formed not only at the regular hexagonal region i3a but also at the corner SV of all the regular hexagonal regions except the outermost periphery provided under the Schottky barrier region.

This protrusion AB is from the corner A of the regular hexagon to the tip g! jB
Letting the length up to t be t, it becomes. Actually, 0.16 L 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.

In an SBD having a P-carved hexagonal region having this shape, the entire region of the SBD portion is covered with a space charge region when a reverse voltage is applied. Therefore, a high reverse blocking voltage based on the Pn junction can be obtained. In addition, since the P shadow regions 13a are arranged so that the center of 01 is at the corner apex of an equilateral triangle that is tightly arranged in a hexagonal dense manner, there is almost no mutual overlap when the space charge regions are at their maximum wave. 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, in a Schottky barrier diode, the shape of the impurity diffusion region disposed in the barrier region is a regular hexagon having a center at each vertex of an equilateral triangle arranged in a close-packed hexagonal arrangement, and A Schottky barrier diode with a small forward voltage drop and high reverse blocking voltage because each vertex of the square has a protrusion so that the space charge region completely covers the Schottky barrier region when a breakdown voltage is applied. can be obtained.

[Brief explanation of drawings]

FIG. 1 is a top view showing one embodiment of the present invention, FIG. 2 is a sectional view of the same, FIG. 3 is an enlarged view of the regular hexagonal area of the same, and FIG.
The figure is a sectional view of essential parts of a conventional integrated seven-layer barrier diode. 13... Regular hexagonal area, 14... Annular area, 16.
Schottky barrier electrode, 17... cathode electrode, A
B...Protrusion.

Claims (1)

[Claims] A plurality of impurity diffusion regions of a conductivity type different from that of the semiconductor are provided on the semiconductor surface under the Schottky barrier region,
The distance between each region is P when the breakdown voltage is applied.
In the case where the length of the space charge region extending outside the n-junction is shorter than twice, the shape of the impurity diffusion region is at each vertex of an equilateral triangle that is densely laid out. It is a regular hexagon with a center,
A high-voltage Schottky barrier diode characterized in that each vertex of each regular hexagon has a protrusion such that a space charge region completely covers the Schottky barrier region when a breakdown voltage is applied.