JP2826914B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a semiconductor device according to the present invention.

[0002]

2. Description of the Related Art As is well known, the characteristics of semiconductor devices have been improved.
Particularly, in order to improve forward characteristics, reverse characteristics, and switching characteristics, development has been promoted and various structures have been proposed.

FIG. 1 is a sectional structural view of a conventional semiconductor device. FIG. 1 shows that the present inventors have filed Japanese Patent Application No. Hei 3-11534.
1 is a structure invented by a "Schottky barrier semiconductor device", wherein 1 is a one conductivity type semiconductor region, for example, an N-type silicon semiconductor, 1 'is a low resistance one conductivity type semiconductor region, for example, an N + type silicon semiconductor, 2 Is a reverse conductivity type semiconductor region,
For example, a P + type silicon semiconductor, 3 is a one-electrode metal, 4 is an ohmic electrode metal, 5 is a concave portion formed by a trench, 6 is a convex portion, A is an anode, and C is a cathode.

In the above-mentioned Japanese Patent Application No. 3-115341, a well-known metal that forms a Schottky barrier contact is selected as the one-electrode metal 3 to improve the forward characteristics, and at the time of reverse bias (2) assault, use one conductivity type semiconductor. Region 1 and one electrode metal 3
Is formed by sandwiching the space charge layer extending from the Schottky barrier contact surface e formed by the space charge layer from the PN junction formed by the opposite conductivity type semiconductor region 2 from both sides. As a result, the electric field strength E applied to the contact surface e is suppressed to a low value, and the reverse leakage current is improved. Note that such an effect is not limited to the case where the contact surface e forms a Schottky barrier contact, and the same applies to the case of ohmic contact.

[0005] Assuming that the closest distance W between adjacent opposite conductivity type semiconductor regions 2 that determines an effective channel width within the cell size CW, in the current semiconductor manufacturing technology, the forward current effective region ratio α = W /CW<0.2-0.4. Therefore, the cell size CW becomes extremely large in order to secure the closest distance W for determining the required forward current. That is, even if the semiconductor chip is excellent in characteristics, the shape of the semiconductor chip becomes large, and the semiconductor device becomes expensive.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional device, and realizes a high-speed, low-loss semiconductor device having a small reverse leakage current and a forward voltage drop with a structure having a large forward current effective area ratio α. The purpose is to gain.

[0007]

An embodiment of the present invention is shown in the sectional structural view of FIG.
1 denote the same parts. Reference numeral 2a denotes a first reverse conductivity type semiconductor region formed above the convex portion 6, and 2b denotes a second reverse conductivity type semiconductor region formed below the bottom portion and the side portion of the convex portion 6; A single electrode metal 3 forms a Schottky or ohmic contact surface e 'on the side of the convex portion 6 between the region 2a and the second region 2b.

More specifically, a trench is formed in an N-type silicon semiconductor substrate by a known method, a concave portion 5 and a convex portion 6 are provided, and a first reverse conductivity type semiconductor region 2a and a second reverse conductive type are formed. 3) A boron atom is formed as a P + region at the position of the conductive semiconductor region 2b by ion implantation or vapor phase diffusion. Next, one-electrode metal 3 was formed by an evaporation method.

The second opposite conductivity type semiconductor region 2b is desirably formed over a part of the bottom and side portions of the projection 6, but it is necessary to form it at least at a corner of the bottom.

Regarding the shape of each part, the closest distance WL between the first area 2a and the second area 2b, the closest distance L between each adjacent second area 2b, and the zero extending from the contact surface e '. Assuming that the depth Wbi of the space charge layer at the time of bias, the space charge layer WB at the time of breakdown, and the angle θ between the tangent at the point f of Wbi in the second region 2b and the contact surface e ′, WL and L are 2Wb
smaller than i or at least within 2WB, θ
Is preferably formed such that 60 degrees ≦ θ ≦ 180 degrees. Thus, between the anode A and the cathode C, one conductive layer having a first region 2a and two metal-semiconductor contact surfaces e 'sandwiched by the respective second regions 2b. A semiconductor device having the mold semiconductor 1 as a base is formed. That is, it is possible to form a semiconductor device having a contact surface e 'on each of the right and left sides of the convex portion 6 in FIG.

When the contact surface e in FIG. 1 and the contact surface e ′ in FIG. 2 have the same area, the forward current effective area ratio α can be doubled in the structure of the present invention in FIG. 2 as compared with the conventional structure in FIG.

In the formation of a trench having a one-conductivity-type semiconductor surface with irregularities, the forward current effective area ratio α can be doubled by a plurality of strip-shaped trenches. By forming a plurality of island-shaped trench grooves as shown in the plan view of FIG. 7, the effective area ratio α can be made four times or more by devising the three-dimensional dimensions of the cell.

As described above, according to the structure of the present invention, the contact surface e 'can be enlarged, that is, the effective area in the cell can be increased without exerting the effect of suppressing the reverse leakage current described in FIG. it can. For the same forward current, the current density at the contact surface e 'can be reduced, and when e' is a Schottky contact, the forward voltage drop can be reduced. When the current density is made equal to that of the conventional structure shown in FIG. 1, the chip size can be reduced, so that an inexpensive semiconductor device can be obtained.

When the contact surface e 'is in ohmic contact, the electrical characteristics corresponding to the electron potential height in the one conductivity type semiconductor region based on the formation of the first region 2a and the second region 2b. And the same rectifying characteristics in the forward and reverse directions as in the case where the contact surface e ′ was in Schottky contact were observed.

In the sectional structure of FIG. 2, the shape of the trench groove, that is, the shape of the concave portion 5 is not limited to a trapezoid or a rectangle, and the shape of the second region 2b, the distance of each part, and the dimensional relationship are also limited to the embodiment. Not something. Other modifications, conversions, additions, and other changes are also included in the rights of the present application within the scope of the present invention.

[0016]

As described above, a semiconductor device having excellent forward characteristics, reverse characteristics, and switching characteristics can be obtained with a structure in which the effective area ratio of the forward current is increased, and the Schottky or ohmic contact can be obtained. It is possible to achieve economy by reducing the current density on the surface or reducing the chip size, and it is very effective when applied to semiconductor devices used for various industrial equipment including power.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a conventional semiconductor device.

FIG. 2 is a sectional structural view showing an embodiment of the present invention.

FIG. 3 is a plan view showing an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 one conductivity type semiconductor region 1 ′ low resistance one conductivity type semiconductor region 2 reverse conductivity type semiconductor region 2 a first reverse conductivity type semiconductor region 2 b second reverse conductivity type semiconductor region 3 one electrode metal 4 ohmic electrode metal 5 Concave part 6 Convex part A Anode C Cathode e, e 'Contact surface f Contact CW Cell size W Closest distance between two neighboring WLs Closest distance between 2a and 2b Wbi Space charge layer at zero bias Depth WB Space charge layer width at the time of dielectric breakdown L Closest distance of adjacent 2b θ angle

Claims (1)

(57) [Claims] 1. A semiconductor device in which a trench having a one-conductivity-type semiconductor surface with irregularities is formed, wherein a first reverse-conductivity-type semiconductor region, a bottom of the protrusion, or a part of a side portion is included above the protrusion. A second reverse conductivity type semiconductor region is formed at the bottom, and a metal layer for forming a Schottky or ohmic contact is provided on both sides of the projection sandwiching the first and second reverse conductivity type semiconductor regions. Semiconductor device.