JPH04321274A - Schottky barrier semiconductor device - Google Patents

Abstract

PURPOSE:To rapidly minimize the loss in inverse leakage current by a method wherein the relations between the angle of the tangential line of the inverse conductivity type semiconductor regions with the depth of a space charge layer during the zero bias time, the nearest distance of multiple inverse conductivity type semiconductor regions and the width and the depth of the space charge layer during the insulation breakdown time are specified to reduce the current and the voltage decline in the normal direction. CONSTITUTION:Multiple inverse conductivity type semiconductor diode regions 2' are arrayed on the surface of one conductivity type semiconductor 1 furthermore, one electrode metal 4 is in Schottky barrier contact with the semiconductor 1 but in ohmic contact or Schottky barrier contact with said region 2'. At this time, the angle theta deg. of the tangential line of the regions 2' on the positions in the space charge layer depth of Wbi during the zero bias time extending from the contact surface (e) of the one electrode metal 4 and the one conductivity type semiconductor 1 making with the central side of the contact surface (e) is specified to be 0<theta deg.<=135 deg. while the relations between the nearest distance W of the regions 2', said depth Wbi and the space charge layer width WB during the insulation breakdown time are specified to be 3Wbi<=W<=2WB.

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 Schottky barrier semiconductor device.

0002

[Prior Art] As is well known, improving the characteristics of semiconductor devices,
In particular, development is progressing and various structures have been proposed to improve switching speed and forward and reverse characteristics.

FIG. 1 shows a cross-sectional structural diagram of a conventional Schottky barrier semiconductor device. 1 is a semiconductor of one conductivity type, for example, N
type semiconductor, 1' is a low resistance one conductivity type semiconductor, for example, N
+ type semiconductor, 2 is a guard ring region of an opposite conductivity type semiconductor (for example, P type semiconductor), 3 is an insulating film, for example, SiO
Reference numerals 2 and 4 are metal electrodes forming Schottky barrier contact, 5 is an ohmic electrode metal, A is an anode electrode, and C is a cathode electrode.

The Schottky barrier semiconductor device shown in FIG. 1 is well known as a structure that improves breakdown voltage, but on the other hand,
In the rectifying action, there is a drawback that the leakage current in the reverse direction is large, so the loss in the reverse direction is large, and the efficiency as a rectifying element is poor.

[0005]

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

[0006]

Embodiment An embodiment of the present invention is shown in cross-sectional structural views in FIGS. 3, 4, and 5. FIGS. 3, 4, and 5 each show the structure of an example obtained by changing the manufacturing method. Also, FIG. 6 shows Y-Y in FIG.
'It is a plan view of the structure.

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

The most important requirement for the structure of the present invention is that θ should be 0<0.
θ≦135° and 3Wbi≦W≦2WB
It is to form a relationship.

[0009] Also, 0<θ≦135° and 3Wbi≦W≦
In addition to the requirement of 2WB, further improved electrical characteristics can be obtained by forming the relationship D≧0.5W.

Furthermore, a recess 6 is formed on the surface of the semiconductor 1 of one conductivity type, and a deposited layer or an internal formation layer of the semiconductor region 2' of the opposite conductivity type is provided along all or part of the inner surface of the semiconductor 1. 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, 400μ
N type 5Ω・cm, 14μ on m-thick silicon semiconductor substrate
1.6×1 with m-thick epitaxial silicon layer deposited
．． A 6 mm tip was used. First, after forming a SiO2 film, a P-type guard ring region 2 (not shown) was formed. Next, in order to form a plurality of recesses 6 inside the guard ring region 2, windows are opened in the SiO2 film using a stepper exposure device and an RIE etching device.
Furthermore, using the SiO2 film as a mask and adjusting the etching gas of the RIE etching apparatus, the Si etching side surface shape was processed to be almost vertical. After that, the opposite conductivity type semiconductor region 2
To form ', BN deposition and diffusion were performed. Therefore, 2' is provided as an internal forming layer on the inner surface of the recess 6. Next, the SiO2 film on the convex portion is removed, titanium metal is vapor-deposited as one electrode metal 4 on the required portion, and N
i was formed as an ohmic electrode metal 5.

The dimensions of each designation symbol in the structure of FIG. 3 obtained through experiments are as follows: θ is approximately 110°, W is 3.5 μm,
D is 3.0 μm, L (opening width of recess 6) is 2.0 μm,
T (depth of concave portion 6) is 2.0 μm, M (upper width of convex portion)
is 6.0 μm, B (width of opposite conductivity type semiconductor region 2') is 4.4 μm, XB (2'
(bottom dimension) is 1.0 μm, XT (top dimension of 2′) is 1.2 μm, each cell size CW is 8.0 μm x 8.0 μm.
It was set as m.

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

For comparison, the forward and reverse characteristics of a conventional Schottky barrier rectifier diode are shown by curves A in FIGS. 2(a) and 2(b), respectively. Therefore, it has been verified through experiments that the semiconductor device of the present invention has significantly improved reverse leakage current. It should be noted that the curved line C shows an ohmic junction between the one electrode metal 4 and the opposite conductivity type semiconductor region 2', and the curve C shows a Schottky barrier junction.

In the structure of the present application, a space charge layer extending from a Schottky barrier junction formed by one conductivity type semiconductor 1 and one electrode metal 4 during reverse bias is formed by a space charge layer extending from a PN junction formed by an opposite conductivity type semiconductor region 2'. By arranging them so as to sandwich them from both sides at The electric field strength EJ can be weakened to EJ=V/d. This is a result based on the confirmation of the phenomenon that the electric field strength EJ decreases as the depth d of the merged space charge region increases.

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

The relationship between the above angle θ and the electric field strength EJ of the Schottky barrier junction formed by the one conductivity type semiconductor 1 and the one electrode metal 4 is shown in the EJ-θ (electric field strength-angle) characteristic diagram of FIG. Further, 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. W=2WB and W=3Wbi, respectively.
The curve represents a practically preferable range of W.

It can be seen from FIG. 7 that the electric field relaxation effect is maximum when the angle θ is about 90 degrees. That is, the electric field strength E
J is minimum at about 90 degrees, and EJ increases whether it is smaller or larger than that, and when the angle θ exceeds 135 degrees, the EJ value approximates that of a conventional Schottky barrier semiconductor device.

In addition, the reverse leakage current JR in FIG. 8 is determined by the electric field strength EJ
7, it shows a tendency almost similar to that shown in 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 region 2' of the opposite conductivity type semiconductor region 2' is shown in the JR-W characteristic diagram in FIG. 9, and in FIG. This is shown in the VFW characteristic diagram.

In FIG. 9, the angle θ is 90 degrees and the reverse voltage is 10
Depths 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 the JR tends to become smaller in the regions of D≧0.5W and W≦2WB.

FIG. 10 shows the forward current JF150Amp/c
The relationship between forward voltage VF and W at m2 is 3Wbi≦
W≦2WB can be said to be a preferable range with a 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.

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

In FIG. 11, the reverse recovery time trr becomes significantly longer when the nearest distance W becomes smaller than 3Wbi, and shows the same tendency as the VFW characteristic diagram in FIG.

Note that at the junction between 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
When the concentration is lower than Atoms/cm3, a Schottky barrier junction is formed. In this way, 2
'-4 and 1-4 using Schottky barrier junctions, as shown by the line S in FIG.
Unlike the case where ohmic contact is made between ' and 4 and Schottky barrier junction is made between 1 and 4, trr does not increase even in the region of W≦3Wbi.

However, as shown in curve C of the JF-VF characteristic in FIG. 2(a), the series ohmic resistance remains at a high resistance that is not modulated by minority carriers; The disadvantage is that the VF becomes large.

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

The manufacturing method for forming the structure shown in FIG. 4 is to form a recess 6 having a desired depth D, angle θ, and width W from the surface of a semiconductor 1 of one conductivity type by RIE method in the same manner as described above. Thereafter, a deposited layer containing opposite conductivity type impurities at a required concentration is provided to form a reverse 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. Opposite conductivity type semiconductor region 2' produced by such a manufacturing method
The area is about 1
/2 or less, and the Schottky barrier junction area of the main junction can be increased, making it possible to realize a large current Schottky barrier diode with a small chip area.

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

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

After forming the recess 6, impurity atoms of the opposite conductivity type are deposited only on the bottom of the recess 6 by ion implantation from a substantially vertical direction, and further, by high temperature diffusion, the angle θ
can be easily selectively formed up to 90 degrees or less.

The planar structure of the present invention is not limited to the Y-Y′ planar structure diagram in FIG. The pattern shape can be selected.

Further, one electrode metal 4 is shown in FIGS. 3, 4, and 5.
As seen from above, it is not necessary to provide it covering the entire surface, but it is sufficient to provide it covering at least 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.

Furthermore, 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.

[0034] In addition, any modifications, additions, changes in materials, etc., are included within the scope of the present invention, as long as the constituent requirements of the present invention are satisfied.

[0035]

As explained above, by carrying out the present invention, a Schottky barrier semiconductor device with excellent reverse direction characteristics and switching characteristics, high speed, and low loss can be obtained, especially for various applications including power applications. It can be applied to rectifying elements used in industrial equipment, and its effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of a conventional Schottky barrier.

FIG. 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 cross-sectional structural diagram showing an embodiment of the present invention.

FIG. 4 is a cross-sectional structural diagram showing another embodiment of the present invention.

FIG. 5 is a cross-sectional structural diagram showing another embodiment of the present invention.

FIG. 6 is a YY' plane structural diagram of FIG. 5;

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

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

FIG. 9 is a JR-W (reverse leakage current-nearest distance) characteristic diagram.

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

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

[Explanation of symbols]

1 One conductivity type semiconductor 1' Low resistance one conductivity type semiconductor 2 Guard ring region of opposite conductivity type semiconductor 2'
Opposite conductivity type semiconductor region 3 Insulating film 4 One electrode metal 5 Ohmic electrode metal 6 Recess A Anode electrode B Width of 2' C Cathode electrode D Depth of 2' from contact surface e 1 and 4 Contact surface f Contact point L Opening width M of 6 Upper width of convex portion T Depth CW of 6 Cell size XB Bottom dimension of 2' XT Upper dimension of 2' W Closest distance Wbi of 2' at 1 4 and 1 Depth WB of the space charge layer at zero bias extending from e of space charge layer width θ at dielectric breakdown Angle JF formed by the tangent of 2' at the position Wbi from the center of the contact surface e Forward current JR Reverse leakage Current VF Forward voltage VR Reverse voltage trr Reverse recovery time EJ Electric field strength

Claims (3)

[Claims] 1. A plurality of semiconductor regions of opposite conductivity type are arranged on the surface of a semiconductor of one conductivity type, further, one electrode metal is in Schottky barrier contact with the semiconductor of one conductivity type, and the semiconductor regions of opposite conductivity type are in ohmic contact. , or in a Schottky barrier semiconductor device formed by Schottky barrier contact, the tangent to the opposite conductivity type semiconductor region at the position of the space charge layer depth Wbi at zero bias extending from the contact surface of one electrode metal and one conductivity type semiconductor is as described above. The angle θ formed from the center side of the contact surface is 0<θ≦1
35°, and the relationship between the closest distance W, Wbi of a plurality of opposite conductivity type semiconductor regions, and the space charge layer width WB at the time of dielectric breakdown is 3Wbi≦W≦2WB. Device. 2. The relationship between the depth D and W of the opposite conductivity type semiconductor region from the contact surface of one electrode metal and one conductivity type semiconductor is D≧0.
．． 2. The Schottky barrier semiconductor device according to claim 1, wherein the Schottky barrier semiconductor device has a power of 5W. 3. A claim characterized in that a recess is formed on the surface of a semiconductor of one conductivity type, and a deposited layer or an internal formation layer of a semiconductor region of an opposite conductivity type is provided along all or part of the recess. The Schottky barrier semiconductor device according to claim 1 or claim 2.