JP2879479B2 - Schottky barrier 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 a Schottky barrier semiconductor device.

[0002]

2. Description of the Related Art As is well known, the characteristics of semiconductor devices have been improved.
In particular, developments have been made to improve the switching speed, forward and reverse characteristics, and various structures have been proposed.

FIG. 1 shows a cross-sectional structure diagram of a conventional Schottky barrier semiconductor device. 1 is a semiconductor of one conductivity type, for example, N
Semiconductor 1 ′ is a low-conductivity one-conductivity semiconductor such as N
⁺ Type semiconductor, 2 is a guarding region of a semiconductor of the opposite conductivity type (for example, P type semiconductor), 3 is an insulating film, for example, Si
O2 and 4 are one-electrode metals forming a Schottky barrier contact, 5
Is an ohmic electrode metal, A is an anode electrode, C is a cathode.
Electrode.

The Schottky barrier semiconductor device shown in FIG. 1 is well known as a structure for improving the breakdown voltage.
In the rectifying operation, there is a disadvantage that the reverse leakage current is large, the reverse loss is large, and the efficiency as a rectifying element is low.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional device and to provide a high-speed, low-loss Schottky barrier semiconductor device having a small reverse leakage current and a forward voltage drop.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is shown in the sectional structural views of FIGS. 3, 4 and 5. FIG. FIGS. 3, 4 and 5 show the structure of the embodiment obtained by changing the manufacturing method, respectively. FIG. 6 is a cross-sectional view of FIG.
It is a Y 'plane structural view.

In FIGS. 1, 3, 4, 5 and 6, the same reference numerals indicate the same parts. Further, 2 ′ is a semiconductor region of the opposite conductivity type, for example, a P-type semiconductor, 6 is a concave portion, W is a closest distance in the semiconductor 1 of one conductivity type of the semiconductor region 2 ′ of the opposite conductivity type, and Wbi is one conductivity type with the one electrode metal 4. Is the space charge layer width at zero bias extending from the contact surface e of the type semiconductor 1, and θ is W
The angle formed by the 2 'tangent at the position bi from the center of the contact surface e, f is the contact point, and D is the depth 2' from the contact surface e. Although not shown, the width of the space charge layer extending toward the one conductivity type semiconductor 1 at the time of insulation breakdown at the junction between the one conductivity type semiconductor 1 and the opposite conductivity type semiconductor 2 ′ is represented by WB.

The most important requirement in the structure of the present invention is that θ is 0 <
θ ≦ 135 ° and 3Wbi ≦ W ≦ 2WB.

Also, 0 <θ ≦ 135 ° and 3Wbi ≦ W ≦ 2
By forming the relation of D ≧ 0.5 W in addition to the requirement of WB, further improved electric characteristics can be obtained.

A recess 6 is formed in the surface of the one-conductivity-type semiconductor 1, and a deposition layer of an opposite-conductivity-type semiconductor region 2 'or an internal formation layer is provided along the whole or a part of the inner surface of the semiconductor 6. By doing so, excellent electrical characteristics can be obtained.

Next, an embodiment of the structure of the present invention shown in FIG. 3 will be described in detail. N + type 0.003Ω · cm, 400μm
N-type 5 Ω · cm, 14 μm on a thick silicon semiconductor substrate
1.6 × 1.6 deposited thick epitaxial silicon layer
mm chips were used. First, after forming a SiO2 film, a P-type guarding region 2 (not shown) was formed. Next, in order to form a plurality of recesses 6 inside the guard ring 2, a stepper exposure apparatus and R
A window was opened in the SiO2 film using an IE etching apparatus, and the etching gas of the RIE etching apparatus was adjusted using the SiO2 film as a mask to process the Si etching side surface substantially vertically. Thereafter, the reverse conductivity type semiconductor region 2 '
Was formed by BN deposition and diffusion. Therefore, 2 'is provided as an internal formation layer on the inner surface of the concave portion 6. Next, the SiO2 film on the convex portion is removed, and titanium metal is deposited as a one-electrode metal 4 on a required portion.
i was formed as the ohmic electrode metal 5.

The dimensions of each designated code in the structure of FIG. 3 obtained by experiments are as follows: θ is about 110 °, W is 3.5 μm,
D is 3.0 μm, L (opening width of recess 6) is 2.0 μm, T
(The depth of the concave portion 6) is 2.0 μm, M (the upper width of the convex portion) is 6.0 μm, B (the width of the reverse conductivity type semiconductor region 2 ′) is 4.4 μm, and XB (the bottom dimension of the 2 ′). Is 1.0 μm and XT (upper dimension of 2 ′) is 1.0 μm.
2 μm, and each cell size CW was 8.0 μm × 8.0 μm.

The forward / backward characteristics of the Schottky barrier rectifier diode of the present invention thus obtained are shown in FIG.
F-VF (forward current-forward voltage) characteristic diagram and JR in FIG. 2 (b)
Each of the -VR (reverse leakage current-reverse voltage) characteristic diagrams is shown by a curve b.

For comparison, forward and reverse characteristics of a Schottky barrier type rectifier diode having a conventional structure are shown by curves a in FIGS. 2A and 2B, respectively. Therefore, experiments have proved that the semiconductor device of the present invention has a remarkable improvement in reverse leakage current. An ohmic junction between the one electrode metal 4 and the opposite conductivity type semiconductor region 2 'is shown in a curved line, and a Schottky barrier junction is shown in a curved line C.

In the structure of the present invention, the space charge layer extending from the Schottky barrier junction formed by the one conductivity type semiconductor 1 and the one electrode metal 4 at the time of reverse bias is formed by the space charge layer formed by the PN junction formed by the reverse conductivity type semiconductor region 2 '. And the space charge layers in the three directions are merged from the contact surface e to the depth of d at a certain reverse voltage or more, so that the voltage V applied to the contact surface e, which is a Schottky barrier junction, is reduced. The electric field intensity EJ can be reduced to EJ = V / d. This is based on the confirmation that the electric field intensity EJ decreases as the depth d of the merged space charge region increases.

It can be derived from a known general formula that the electric field strength EJ applied to the Schottky barrier junction should be reduced in order to improve the reverse leakage current of the Schottky barrier semiconductor device.

The relationship between the angle θ and the electric field intensity EJ of the Schottky barrier junction formed by the one conductivity type semiconductor 1 and the one electrode metal 4 is shown in an EJ-θ (electric field intensity-angle) characteristic diagram of FIG. The relationship between the angle θ and the reverse leakage current JR of the Schottky barrier junction is shown in the JR-θ (reverse leakage current-angle) characteristic diagram of FIG. Curves at W = 2WB and W = 3Wbi are shown, respectively, and indicate the range of W which is practically preferable.

FIG. 7 shows that the maximum electric field relaxation effect is exhibited when the angle θ is about 90 degrees. That is, the electric field intensity E
J is the minimum at about 90 degrees, and EJ increases when it is smaller or larger than it. When the angle θ exceeds 135 degrees, it approaches the value of EJ of the conventional Schottky barrier semiconductor device.

Also, the reverse leakage current JR in FIG. 8 depends on the strength of the electric field intensity EJ, and thus shows a tendency substantially similar to FIG.

Next, the relationship between the closest distance W, the reverse leakage current JR, and the forward voltage VF in the one conductivity type semiconductor 1 in the reverse conductivity type semiconductor region 2 'will be described with reference to the JR-W characteristic diagram of FIG. Is shown in FIG.

FIG. 9 shows that the angle θ is 90 degrees and the reverse voltage 10
The depth D and JR of the opposite conductivity type semiconductor region 2 'from the contact surface e (Schottky barrier junction surface) when V is applied are shown. Therefore, it was confirmed that JR tended to decrease in the range of D ≧ 0.5 W and W ≦ 2 WB.

FIG. 10 shows a forward current JF150 Amp / cm.
² is a relationship between forward voltage VF and W, and 3Wbi ≦ W ≦ 2
WB is a preferable range of low VF. Curve 2 shows an ohmic junction between the one electrode metal 4 and the opposite conductivity type semiconductor region 2 ', and curve E shows a Schottky barrier junction.

FIG. 11 shows a trr-W (reverse recovery time-closest distance) characteristic diagram showing switching characteristics of the semiconductor device of the present invention.

In FIG. 11, the reverse recovery time trr becomes remarkably large when the closest distance W is smaller than 3 Wbi, and shows the same tendency as the VF-W characteristic diagram of FIG.

In the junction of the opposite conductivity type semiconductor region 2 'and the one-electrode metal 4, the surface concentration of 2' is set to about 5 × 10 18 A
When the concentration is as low as toms / cm3 or less, a Schottky barrier junction is formed. Thus, 2'-
In the case where each of the regions 4 and 1-4 is formed by a Schottky barrier junction, as shown by the line S in FIG.
Unlike the case where ohmic contact is made between layers 4 and Schottky barrier junction is made between layers 1-4, even in the region of W ≦ 3Wbi, tr
r does not increase.

However, as shown by the curve C of the JF-VF characteristic in FIG. However, the disadvantage that VF becomes large occurs.

Although the manufacturing method for obtaining the structure of the apparatus of the present invention as shown in FIG. 3 has been described above, FIGS. 4 and 5, which are other embodiments of the apparatus of the present invention, will be briefly described.

The method of forming the structure shown in FIG. 4 is to form a recess 6 suitable for the desired depth D, angle θ, and width W by RIE from the surface of the one-conductivity type semiconductor 1 in the same manner as described above. After that, a deposition layer containing a necessary concentration of the impurity of the opposite conductivity type is provided to form the opposite conductivity type semiconductor region 2 '. The deposited layer is formed by forming an epitaxial semiconductor layer or by depositing a polycrystalline semiconductor by a CVD method. The area of the opposite conductivity type semiconductor region 2 'formed by such a manufacturing method is characterized in that it can be reduced to about 1/2 or less as compared with that of a manufacturing method formed by a normal thermal diffusion method. Therefore, a Schottky barrier diode with a large current can be realized with a small area chip.

In the structure of FIG. 5, as shown in FIGS. 3 and 4, a reverse conductivity type semiconductor region 2 'is formed by a diffusion method without forming a concave portion. In the structure of FIG.
Although it is difficult to set the angle to about 90 degrees, which is the most preferable angle as described above, it is an economical manufacturing method, and it is easy to obtain an inexpensive semiconductor device.

In the structure shown in FIGS. 3 and 4 in which the concave portion 6 is formed on the surface of the one-conductivity type semiconductor 1, the desired shape of the concave portion 6 can be arbitrarily adjusted by adjusting the composition, temperature, pressure, etc. of the etching gas of the RIE method. Make sure you can get it.

After the recess 6 is formed, an impurity atom of the opposite conductivity type is deposited only at the bottom of the recess 6 by ion implantation from a substantially vertical direction.
Can be easily selected and formed up to 90 degrees or less.

The plane structure of the present invention is not limited to the YY 'plane structure diagram of FIG. 6, and for example, various shapes such as a stripe shape, a circle shape, a polygon shape, etc. may be applied to the shape of the one conductivity type semiconductor 1. The pattern shape can be selected.

The one-electrode metal 4 is shown in FIGS. 3, 4 and 5.
As seen from above, it is not necessary to cover the entire surface as viewed from above, but it is sufficient if the cover is provided over at least a part of the contact surfaces e and 2 'with 1. Further, the recess 6 in FIGS. 3 and 4 may be filled with the metal material 4.

The Schottky barrier semiconductor device of the present invention is not limited to a rectifier diode, but can be used as another semiconductor device or a partial structure thereof.

In addition, any modifications, additions, changes in material conversion, and the like are included in the scope of the present invention as long as the constituent requirements of the present invention are satisfied.

[0035]

As described above, according to the present invention, a high-speed, low-loss Schottky barrier semiconductor device having excellent reverse characteristics and switching characteristics, particularly,
The present invention can be applied to rectifiers and the like used for various industrial equipments including power use, and the effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a conventional Schottky barrier.

2A is a JF-VF (forward current-forward voltage) characteristic diagram, and FIG. 2B is a JR-VR (reverse leakage current-reverse voltage) characteristic diagram.

FIG. 3 is a sectional area diagram showing an embodiment of the present invention.

FIG. 4 is a sectional structural view showing another embodiment of the present invention.

FIG. 5 is a sectional structural view showing another embodiment of the present invention.

FIG. 6 is a plan structural view taken along the line Y-Y ′ of FIG. 5;

FIG. 7 is an EJ-θ (electric field intensity-angle) characteristic diagram.

FIG. 8 is a characteristic diagram of JR-θ (reverse leakage current-angle).

FIG. 9 is a characteristic diagram of JR-W (reverse wetting current—closest distance).

FIG. 10 is a VF-W (forward voltage-nearest distance) characteristic diagram.

FIG. 11 is a trr-W (reverse recovery time-closest distance) characteristic diagram.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 One conductivity type semiconductor 1 'Low resistance one conductivity type semiconductor 2 Guard ring region of reverse conductivity type semiconductor 2' Reverse conductivity type semiconductor region 3 Insulating coating 4 One electrode metal 5 Ohmic electrode metal 6 Concave part A Anode electrode B 2 ' Width C Cathode electrode D Depth of 2 'from contact surface e e Contact surface of 1 and 4 f Opening width of contact L6 M Top width of convex portion T Depth of 6 CW Cell size XB 2' bottom dimension XT The top dimension of 2 ′ The closest distance at 1 of W 2 ′ Wbi 4 and the space charge layer width at zero bias extending from e of 1 WB 1 and 1 of the space charge layer width at breakdown of the junction formed by WB 1 and 2 ′ Space charge layer width spread to the side. The angle formed by the tangent line 2 ′ at the position of θ Wbi from the center of the contact surface e JF forward current JR reverse leakage current VF forward voltage VR reverse voltage trr reverse recovery time EJ electric field strength

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/28-21/288 H01L 21/44-21/445 H01L 29/40-29/51 H01L 29/872

Claims (3)

(57) [Claims] A plurality of opposite conductivity type semiconductor regions arranged on a surface of the one conductivity type semiconductor, further, one electrode metal makes Schottky barrier contact with the one conductivity type semiconductor, and ohmic contact with the opposite conductivity type semiconductor region; or In the Schottky barrier semiconductor device formed by Schottky barrier contact, the tangent of the opposite conductivity type semiconductor region at the depth position of the space charge layer width Wbi at zero bias extending from the contact surface between the one electrode metal and the one conductivity type semiconductor is in contact with the first contact. The angle θ formed from the center of the surface is 0 <θ ≦ 1
35 °, and the relationship between the closest distances W and Wbi of the plurality of opposite conductivity type semiconductor regions and the space charge layer width WB extending to the one conductivity type semiconductor at the time of dielectric breakdown is 3Wbi ≦ W ≦ 2WB.
A Schottky barrier semiconductor device characterized by being formed on a substrate. 2. The relationship between the depth D and the width W of the opposite conductivity type semiconductor region from the contact surface between the one electrode metal and the one conductivity type semiconductor is D ≧ 0.
2. The Schottky barrier semiconductor device according to claim 1, wherein the power is 5 W. 3. A concave portion is formed on a surface of the one conductivity type semiconductor,
3. The Schottky barrier semiconductor device according to claim 1, wherein a deposition layer of an opposite conductivity type semiconductor region or an internal formation layer is provided along all or a part of the recess.