JPH065842A - Semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a semiconductor device having a Schottky barrier diode (hereinafter referred to as SBD), and it is possible to reduce the series resistance between the anode and the cathode by making the current distribution uniform. An object is to provide a semiconductor device having a possible SBD. A semiconductor substrate 11 having at least one conductivity type surface layer, and a doughnut-shaped first electrode 18 in contact with the semiconductor substrate 11 to form a Schottky junction with the semiconductor substrate 11. A second electrode 19 formed so as to surround an outer peripheral portion of the first electrode 18 and in contact with the semiconductor substrate 11 to form an ohmic contact with the semiconductor substrate 11, The third electrode 20 is formed inside the inner peripheral edge of the first electrode 18 and is in contact with the semiconductor substrate 11 to form an ohmic contact with the semiconductor substrate 11.

Description

Detailed Description of the Invention

(Table of contents) -Industrial application field-Conventional technology (Fig. 5) -Problems to be solved by the invention-Means for solving the problem-Action-Examples (Figs. 1 to 4) -Invention Effect of

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device having a Schottky barrier diode.

[0003]

2. Description of the Related Art Schottky barrier diodes (hereinafter referred to as S
It is called BD. ) Has a small rising voltage and is a majority carrier element, and therefore has a high speed. Therefore, it is often used as a rectifying element such as a highly efficient power supply rectifying circuit with little loss. In recent years, to reduce the number of parts,
A linear IC incorporating a power supply rectifying circuit composed of such an SBD has come to be produced. Even in this case, it is desired to maintain high efficiency.

5 (a) and 5 (b) are views for explaining the SBD of a power supply rectifying circuit incorporated in a linear IC or the like of a conventional example. FIG. 5 (a) is a plan view and FIG. 5 (b). Figure 5
It is the sectional view on the AA line of (a).

In FIGS. 5A and 5B, 1 is a silicon substrate, 2 is a field insulating film selectively formed on the surface of the silicon substrate 1, and is a rectangular region 3a for forming a Schottky junction 7 of the SBD. A field insulating film is not formed in the annular region 3b surrounding the rectangular region 3a. However, the field insulating film 2 is formed in the annular region 3b where the wiring 6a formed integrally with the anode electrode 5a passes. Reference numeral 4 denotes a contact region layer formed by introducing a high concentration of n-type impurities into the silicon substrate 1 in the annular region, which surrounds the outer peripheral edge of the rectangular region 3a and passes through the wiring 6a. Even in the region to be formed, it is formed seamlessly.

Reference numeral 5a includes a two-layer conductor film of a titanium (Ti) film / aluminum (Al) film, and has a rectangular region 3
The wiring 6a for connecting to another SBD or the like is integrally formed with the anode electrode which is in contact with the silicon substrate 1 of a to form a Ti / silicon Schottky junction.
5b connects with the contact region layer 4 of the annular region 3b,
The cathode electrode is formed so as to surround the outer peripheral portion of the rectangular region 3a, and the wiring 6b for connecting to another SBD or the like is integrally formed. Since the cathode electrode 5b is in the same layer as the wiring 6a, the wiring 6
It is not formed in the region where a passes, and is interrupted in this region.

Such an SBD operates as follows. That is, when a positive voltage is applied to the anode electrode 5a and a negative voltage is applied to the cathode electrode 5b, a current flows through the path of the anode electrode 5a / Schottky junction 7 / silicon substrate 1 / contact region layer 4 / cathode electrode 5b. Flows. When a voltage is applied with the opposite polarity, no current flows due to the barrier of the Schottky junction 7. As a result, the rectifying operation is performed.

[0008]

By the way, the above SB
In D, when the current to be flown becomes large, the area of the anode electrode is made large. However, the current path from the central part of the anode electrode to the cathode electrode is longer than the current path from the peripheral part of the anode electrode to the cathode electrode. The series resistance between them will be different. Therefore, the current distribution becomes non-uniform and the series resistance does not decrease so much. For this reason, the current to be flown cannot be increased despite the increase in the area of the anode electrode.

The present invention was created in view of the problems of the prior art, and a semiconductor device having an SBD capable of reducing the series resistance between the anode and the cathode by making the current distribution uniform. For the purpose of providing.

[0010]

The first object of the present invention is to provide a semiconductor layer of one conductivity type and an annular first contact with the semiconductor layer to form a Schottky junction. The second electrode, which is formed so as to surround the outer peripheral portion of the first electrode, and which is in contact with the semiconductor layer to form an ohmic contact with the semiconductor layer; A third electrode which is formed inside the inner peripheral edge of the first electrode and which is in contact with the semiconductor layer to form an ohmic contact with the semiconductor layer and is electrically connected to the second electrode; And a second semiconductor layer, the second semiconductor layer being formed on a semiconductor substrate of opposite conductivity type.
Achieved by the semiconductor device according to the invention, and thirdly,
A contact portion between the annular first electrode and the semiconductor layer, the contact portion at the outer peripheral edge portion and the contact portion at the inner peripheral edge portion of the first electrode being opposite to the semiconductor layer having the one conductivity type. This is achieved by the semiconductor device according to the first or second invention, wherein the conductivity type region layer is selectively formed.

[0011]

[Operation] In the semiconductor device of the present invention, the second electrode is formed so as to surround the first electrode as in the conventional case, and the shape of the first electrode is different from the conventional case, for example, the outer peripheral portion is circular. A third electrode is formed in a donut shape having a shape or a polygonal shape, and in a region corresponding to the central portion of the conventional first electrode formation region.

Therefore, for example, the first as the anode electrode
The current flowing from the electrode of the second electrode is a second electrode as a cathode electrode surrounding the outer peripheral edge of the first electrode and the third electrode as a cathode electrode existing inside the inner peripheral edge of the first electrode. Disperse in and flow. As a result, compared with the conventional case, the current distribution is made uniform, so that the series resistance between the first electrode / the second and third electrodes, that is, the anode / cathode can be reduced.
Note that the reduction in the series resistance due to the averaging of the current can sufficiently compensate for the reduction in the area of the first electrode for forming the third electrode.

Further, since the semiconductor layer having one conductivity type is formed on the semiconductor substrate of the opposite conductivity type, the SBD is formed on the semiconductor layer, and the opposite conductivity type region layer and the like are formed to form the device. Element isolation can be performed. This makes it possible to create a semiconductor integrated circuit device or the like including the SBD.

Further, the opposite conductivity type region layer is selectively formed on the semiconductor layer having one conductivity type in the contact portion of the outer peripheral edge portion and the contact portion of the inner peripheral edge portion of the first electrode. Therefore,
Since the electric field is easily concentrated and the peripheral portion of the Schottky junction of the first electrode is protected by the opposite conductivity type region layer so as not to operate, the reverse leakage current is reduced and the reverse breakdown voltage is improved. You can

[0015]

Embodiments of the present invention will now be described with reference to the drawings. 1A and 1B show the first embodiment of the present invention.
FIG. 5 is an explanatory diagram of a semiconductor device including an SBD according to the embodiment of the present invention, for example, an SBD forming a power supply rectifier circuit of a linear IC.
2 shows one of the SBDs and its peripheral portion.
1A is a plan view, and FIG. 1B is BB of FIG.
It is a line sectional view.

In FIGS. 1A and 1B, 11 is an n-type silicon substrate (semiconductor layer), 12 is a field insulating film made of a silicon oxide film selectively formed by thermal oxidation, and an outer peripheral edge portion. Donut-shaped with a square shape,
A first cathode electrode (second electrode) 1 formed so as to surround the Schottky junction formation region 13a of the anode electrode (first electrode) 18 and the outer peripheral edge of the anode electrode 18.
The ohmic contact forming region 14 and the second cathode electrode (third electrode) 20 formed inside the inner peripheral edge portion of the anode electrode 18 are formed in regions other than the ohmic contact forming region 15. .

Reference numerals 16 and 17 denote strip-shaped n ⁺ -type contact region layers formed on the surface layer of the silicon substrate 11 which are in contact with the first cathode electrode 19 and the second cathode electrode 20, respectively. The anode electrode 18 is formed in a rectangular shape without gaps at appropriate intervals from the outer peripheral edge portion and along the outer peripheral edge portion.

18 is a titanium film (Ti) having a film thickness of 1500 to 3000Å
Film) / aluminum film (Al film) with a film thickness of 5000 to 10000Å
It consists of two layers of conductive film, and the outer peripheral edge is 140 × 140 μ.
An annular anode electrode having a square shape of m and an inner peripheral edge portion of a square shape of 50 × 50, the lower Ti film is in contact with the silicon substrate 11, and the contact surface is between the silicon substrate 11 and the silicon substrate 11. Schottky junction is formed. In addition, the width formed integrally with the anode electrode 18 is about 80 μm.
m wiring 21 is drawn out and connected to another SBD or the like (not shown) on the field insulating film 12.

Numeral 19 is formed so as to surround the outer peripheral edge of the anode electrode 18 and has a width of about 30 μm and a film thickness of 5000.
The contact region layer 1 formed on the silicon substrate 11 is the first cathode electrode made of a band-shaped Al film of about 10000 Å.
6, and an ohmic contact is formed between the contact surface 6 and the silicon substrate 11. In addition, an annular anode electrode 18 having a square outer peripheral edge portion
Is formed at an appropriate distance from the outer peripheral edge portion and along the outer peripheral edge portion. The first cathode electrode 19 is not formed in a region of the anode electrode 18 where the wiring 21 passes, and is interrupted. Further, it has a wiring 22 having a width of about 80 μm formed integrally with the first cathode electrode 19, and is drawn out onto the field insulating film 12 and connected to another SBD or the like not shown.

Reference numeral 20 has a 40 × 40 μm square shape formed inside the inner peripheral edge of the anode electrode 18.
The second cathode electrode made of an Al film having a film thickness of 5000 to 10000 Å is in contact with the contact region layer 17 formed on the silicon substrate 11, and an ohmic contact is formed between the contact region layer 17 and the silicon substrate 11 on the contact surface. There is.

Reference numeral 23 denotes a film thickness 5000 to 1000 formed on the entire surface.
Openings 24 and 25 are formed on the first cathode electrode 19 and the second cathode electrode 20, respectively, by an interlayer insulating film made of a 0 Å silicon oxide film.

A wiring 26 is provided on the interlayer insulating film 23 and connects the first cathode electrode 19 and the second cathode electrode 20 through the openings 24 and 25 of the interlayer insulating film 23. Is.

As described above, S in the first embodiment of the present invention
In the semiconductor device having the BD, the first cathode electrode 19 is formed so as to surround the anode electrode 18 as in the conventional case.
And the second cathode electrode 20 is formed in a region corresponding to the central portion of the conventional anode electrode 18 forming region, unlike the prior art.

Therefore, for example, the current flowing from the anode electrode 18 is the first cathode electrode 19 surrounding the outer peripheral edge portion of the anode electrode 18, and the second cathode electrode existing inside the inner peripheral edge portion of the anode electrode 18. It will be distributed to 20 and flow. As a result, the current distribution is made more uniform than in the conventional case, so that the series resistance between the anode and the cathode can be reduced. In addition, the reduction of the series resistance due to the averaging of the current is performed by the second cathode electrode 2
The area of the anode electrode 18 reduced to form 0 can be sufficiently compensated.

In the first embodiment, the anode electrode 1
8 has a rectangular ring shape, but is shown in FIG. 2 (a) which is a top view of the second embodiment and FIG. 2 (b) which is a sectional view taken along the line CC of FIG. 2 (a). As described above, the anode electrode (first electrode) 18a may have a circular ring shape. With such a change in shape, the shape of the first cathode electrode (second electrode) 19a surrounding the outer peripheral edge of the anode electrode 18a and the second cathode electrode inside the inner peripheral edge of the anode electrode 18a. (Third electrode) The shape of 20a is the anode electrode
It has a circular shape corresponding to 18a. Figure 2
Among the reference numerals of (a) and (b), the same reference numerals as those shown in FIGS. 1 (a) and 1 (b) indicate those corresponding to those shown in FIGS. 1 (a) and 1 (b). .

Further, as shown in FIG. 1B, since the anode electrode 18 and the first cathode electrode 19 are formed in the same plane, the first cathode is formed in the area where the wiring 21 of the anode electrode 18 is formed. Although the electrode 19 is interrupted, it is a top view of the third embodiment shown in FIG. 3A and D of FIG. 3A.
As shown in FIG. 3B, which is a cross-sectional view taken along the line D, the wiring 21b of the anode electrode 18b and the first cathode electrode 19b are multilayered so that the wiring 21b and the first cathode electrode 19b are formed.
It is also possible to intersect with and sandwiching the interlayer insulating film 23b so that the first cathode electrode 19b is not interrupted even in the formation region of the wiring 21b. In FIGS. 3A and 3B, 27 is an interlayer insulating film 23 connecting the anode electrode 18b and the wiring 21b.
For the openings of b and other reference numerals, see FIG.
The same numbers as those shown in (b) are shown in FIG.
Those corresponding to those shown in (a) and (b) are shown.

Further, although the n-type silicon substrate 11 is used as the semiconductor layer, as shown in FIG. 4A which is a sectional view of the fourth embodiment, a p-type silicon substrate (semiconductor substrate) is used. An n-type silicon layer (semiconductor layer) 29 formed by, for example, epitaxial growth may be used on the layer 28. As a result, the SBD can be formed in the silicon layer 29, and the p-type region layer and the like can be formed to perform element formation and element isolation. Therefore, it is possible to manufacture a semiconductor integrated circuit device including the SBD. Become. In addition, among the reference numerals of FIG. 4A, the same reference numerals as those shown in FIGS. 1A and 1B indicate those corresponding to those shown in FIGS. 1A and 1B. .

FIG. 4 is a sectional view of the fifth embodiment.
As shown in (b), the contact portion between the annular anode electrode (first electrode) 18d and the silicon substrate (semiconductor layer) 11c, that is, the contact portion at the outer peripheral edge portion and the inner peripheral edge portion of the anode electrode 18d. It is also possible to selectively form p-type region layers (opposite conductivity type region layers) 30a and 30b on the n-type silicon substrate 11c at the contact portions. Therefore, the peripheral portion of the Schottky junction of the anode electrode 18d where the electric field is easily concentrated is protected by the p-type region layers 30a and 30b so that the reverse leak current is reduced and the reverse breakdown voltage is reduced. Can be improved. In addition, among the reference numerals of FIG.
The same numerals as those shown in (a) and (b) indicate those corresponding to those shown in FIGS. 1 (a) and 1 (b).

[0029]

As described above, in the semiconductor device of the present invention, the second electrode is formed so as to surround the first electrode as in the conventional case.
In addition to forming the electrode, the shape of the first electrode is annular unlike the conventional one, and is inside the inner peripheral edge of the first electrode, that is, in the area corresponding to the central portion of the conventional first electrode forming area. A third electrode is formed.

Thus, when a current is passed between the first electrode / the second and third electrodes, that is, between the anode / cathode,
Since the current distribution is made uniform as compared with the conventional case, the series resistance between the anode and the cathode can be reduced.

Since the semiconductor layer of one conductivity type is formed on the semiconductor substrate of the opposite conductivity type, it is possible to manufacture a semiconductor integrated circuit device or the like including SBD. Further, the contact portion of the outer peripheral edge portion and the contact portion of the inner peripheral edge portion of the first electrode,
Since the opposite conductivity type region layer is selectively formed in the semiconductor layer having one conductivity type, an electric field is easily concentrated, and the opposite conductivity type region layer prevents the peripheral portion of the Schottky junction of the first electrode from operating. Protected, thereby reducing the leak current in the reverse direction and improving the breakdown voltage in the reverse direction.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a semiconductor device having an SBD according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a semiconductor device having an SBD according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a semiconductor device having an SBD according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a semiconductor device having an SBD according to fourth and fifth embodiments of the present invention.

FIG. 5 is an explanatory diagram of a semiconductor device having a conventional SBD.

[Explanation of symbols]

11, 11a to 11c Silicon substrate (semiconductor layer), 12, 12a to 12d Field insulating film, 13, 13a to 13d Schottky junction formation region, 14, 14a to 14d, 15, 15a to 15d Ohmic contact formation region, 16 , 16a to 16d, 17, 17a to 17d contact region layer, 18, 18a to 18d anode electrode (first electrode), 19, 19a to 19d first cathode electrode (second electrode), 20, 20a to 20d Second cathode electrode (third electrode), 21, 21a to 21d, 22, 22a to 22d, 26, 26a to 26
d wiring, 23, 23a to 23d interlayer insulating film, 24, 24a to 24d, 25, 25a to 25d, 27 opening, 28 silicon substrate (semiconductor substrate), 29 silicon layer (semiconductor layer), 30a, 30b p-type region Layer (opposite conductivity type area layer).

Claims (3)

[Claims] 1. A semiconductor layer of one conductivity type, an annular first electrode in contact with the semiconductor layer and forming a Schottky junction between the semiconductor layer, and an outer peripheral edge of the first electrode. A second electrode formed so as to surround the semiconductor layer and in contact with the semiconductor layer to form an ohmic contact with the semiconductor layer; and a second electrode formed inside the inner peripheral edge of the first electrode. And a third electrode which is in contact with the semiconductor layer and has an ohmic contact with the semiconductor layer and which is electrically connected to the second electrode. 2. The semiconductor device according to claim 1, wherein the semiconductor layer is formed on a semiconductor substrate of opposite conductivity type. 3. A contact portion between the annular first electrode and the semiconductor layer, wherein the contact portion at the outer peripheral edge portion and the contact portion at the inner peripheral edge portion of the first electrode has the one conductivity type. 3. The semiconductor device according to claim 1, wherein an opposite conductivity type region layer is selectively formed on the semiconductor layer that the semiconductor device has.