JPH0563184A - Rectifying semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a rectifying semiconductor device having a high efficiency and a high speed by holding an electron potential in the reverse characteristic high without increasing a channel series resistance of forward characteristics and eliminating voltage dependency of a reverse leakage current. CONSTITUTION:A Schottky contact surface (e) is formed on the upper surface of a protrusion on the surface of a one conductivity type semiconductor formed with trench grooves 8, an opposite conductivity type semiconductor 5 is formed in the bottom of the groove, and an insulator layer is formed on the sidewall of a protrusion. The semiconductor 5 and a Schottky contact metal layer are electrically connected to the same potential, and so constituted that at least two depleted layers 12, 13 at the time of zero voltage bias are not connected.

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 rectifying semiconductor device.

[0002]

2. Description of the Related Art Conventionally, as a highly efficient rectifying semiconductor device, for example, Japanese Patent Application No. 3-115341 filed by the present inventors.
There is a “Schottky barrier semiconductor device”. It is shown in the cross-sectional structure diagram of FIG. 1, where 1 is a low resistance one conductivity type semiconductor (eg N +), 2 is a one conductivity type semiconductor (eg
N), 3 is a guarding region of a reverse conductivity type semiconductor (for example, P +), 4 is an insulating film, and 5 is a reverse conductivity type semiconductor (for example, P +).
P +), 6 is a metal layer in Schottky contact, 7 is an ohmic electrode, 8 is a recess of a trench groove, 9 is a channel in a semiconductor of one conductivity type, and 11 is a depletion layer region.

The forward characteristic of the rectifying semiconductor device of FIG. 1 will be described. When A is an anode and C is a cathode and a zero voltage bias is applied, the distance WN, the depth D, and the angle .theta. Of the opposite conductivity type semiconductors 5 facing each other (the depth Wbi of the depletion layer extending at the zero voltage bias ( By appropriately selecting the angle formed by the tangent line at the boundary between the opposite conductivity type semiconductor 5 and the one conductivity type semiconductor 2 at the position 2) between the contact surface e),
To form electron energy-potential hills. As long as the maximum height of this potential hill is lower than the height of the Schottky contact barrier formed by the metal layer 6, the forward characteristic is determined by the barrier height (φB). VF determined by Schottky barrier height
The VF value is larger than the value.

On the other hand, a well-known formula for the reverse leakage current JR of the Schottky contact barrier is given by JR = JS · exp {(q / kT) (qE / 4πE) 1/2}, and when the electric field strength E = 0, JR = JS, which is the minimum. Further, even if the reverse voltage is increased, JR has a substantially constant value. However, JS is a saturation current. 2 (a) is an electron potential distribution map of the conventional structure, in which the anode A and cathode in the central part of the channel 9 are shown.
The electron potential distribution between C is shown. That is, the potential gradient near the Schottky contact barrier is large,
The potential gradually decreases as the reverse voltage increases. Particularly, when the depth D of the opposite conductivity type semiconductor 5 is shallow, the channel width WN is wide, and the angle θ is large, this tendency is intensified.

Therefore, as shown by the curve of "conventional structure" of the JR-VR (reverse leakage current-reverse voltage) characteristic of FIG. 5, the reverse leakage current gradually increases depending on the voltage.

The inventors of the present invention filed a patent application on July 18, 1991 as a structure for maintaining a high potential even when a high voltage is applied in the reverse direction and minimizing the voltage dependence of the reverse leakage current. Invented "rectifying semiconductor device". Therefore, in the structure proposed hitherto, including the above-mentioned Japanese Patent Application No. 3-115341, it is necessary to make the depth D extremely deep so as to maintain the maximum potential formed at the time of zero voltage bias even under a high voltage. Further, as the forward characteristic, there is a defect that the forward voltage drop is increased such that the channel series resistance is increased. (3)

[0007]

An object of the present invention is to increase the channel series resistance of the forward characteristic in a rectifying semiconductor device in which a metal layer in Schottky contact is formed on the upper surface of a convex portion of the surface of one conductivity type semiconductor having a plurality of trench grooves. It is an object of the present invention to obtain a high-efficiency and high-speed rectifying semiconductor device that does not have a high electron potential in the reverse direction characteristic and eliminates the voltage dependence of the reverse leakage current.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a sectional structural view of an embodiment of the device of the present invention, and the same reference numerals represent the same parts. Further, 10 is an insulator layer, 12 is a first depletion layer from the Schottky contact surface e extending to the one conductivity type semiconductor 2 side, and 13 is a second depletion layer from the opposite conductivity type semiconductor region 5 extending to the 2 side. is there. In addition,
Reference numerals 12 and 13 are depletion layers when the anode A and the cathode C are set to a zero voltage bias.

A feature of the present invention is that the trench groove 8
The Schottky contact surface e is formed on the upper surface of the convex portion of the surface of the one-conductivity-type semiconductor 2 provided with, the reverse conductivity type semiconductor 5 is formed on the bottom of the concave portion, and the insulator layer 10 is formed on the side wall of the convex portion. And 5 and the metal layer 6 forming the Schottky contact surface e are electrically connected to the same potential, and further, the first depletion layer 12 and the second depletion layer 13 are not connected at least at a zero voltage bias. Is.

Next, a specific production example of the device of the present invention shown in FIG. 3 will be described. 3Ωcm 6μm epitaxial wafer is used for high resistance N type silicon 2, trench groove 8, depth 3μ
The width of the protrusion having a vertical groove shape of m and a width of 1 μm was 1.8 μm. Boron atoms are vertically implanted at a accelerating voltage of 40 keV and a dose of 1 × 10 15 atoms by a known ion implantation method, and then activation heat treatment is performed at 950 ° C. to obtain a surface depth of about 0.5 to 0.8 μm. Concentration 5-10x
A P + region (4) 5 of 10 18 atoms / cm 3 was formed at the bottom of the trench groove 8. Next, a pyrogenic steam oxide film SiO210 formed by an oxyhydrogen flame is formed on the inner surface of the concave trench groove 8.
Of about 2000 angstroms. A photoresist is applied to fill the trench groove 8 so that only a thin resist of 3000 angstroms or less remains on the upper surface of the convex portion to protect the concave oxide film 10. Then, an RF-REACTIVE ION ETCHER output of about 2 KW was used to etch for 60 seconds with CF4 gas and a small amount of O2 gas to form a thin photoresist film and SiO on the upper surface of the convex portion.
2 Membrane is removed. Similarly, the thin SiO2 film on the bottom of the recess is
The P + layer is exposed by etching away with a vertical ion shower. Next, a titanium Schottky metal film 6 is formed on the bottom surface and the side surface of the trench groove 8 to a thickness of about 2000 angstroms by using a planetary-type vacuum vapor deposition device, and the upper surface of the convex portion is formed of the high resistance N-type silicon 2. Forms a Schottky contact surface e.

The device of the present invention obtained as described above shows an electronic potential distribution chart in FIG. 2 (b), and also has JR-VR (reverse leakage current-reverse voltage) characteristic charts 4 and J as electric characteristics.
F-VF (Forward current-Forward voltage) characteristic This is improved as shown in FIG.

Further, the conventional structure of FIG. 1 and the structure of the present invention of FIG. 3 will be described by comparing the depletion layer regions. In the conventional structure of FIG. 1, when the zero voltage bias is applied, the Schottky contact surfaces e and P
When the depletion layer extends from the + layer 5 junction, P + / N and the narrow depletion layer of the Schottky contact junction are formed at the corners of the upper surface and the side surface of the convex portion.
A depletion layer with a wide junction is in contact. As a result, in order to match the Fermi level, the charges in the high resistance N layer 2 at the junction are ejected and depleted to a distance satisfying the charge neutrality condition. At this time, the narrow depletion layer and the wide depletion layer are Are almost orthogonal to each other and maintain continuity, and the Schottky metal layer 6 and P
Under the condition that the + layer 5 is at the same potential, charge rearrangement occurs more than the width depleted to satisfy the neutral condition of each junction and between the adjacent depleted regions. The narrow depletion layer changes to a slightly wide depletion layer, and (5) the wide depletion layer changes to a slightly narrow depletion layer. In particular, at the corners, because the electric field vectors that intersect at right angles overlap,
The composite vector becomes larger and the depletion becomes wider. That is, the width of the depletion layer of the P + / N junction is affected by the narrow depletion layer of the low Schottky contact junction and becomes narrow. Since the depletion layer region has a high electron potential, in order to form a high potential in the central portion of the channel 9, not only the channel width WN is narrowed but also the depletion layer extending from the P + / N junction is formed. Since increasing the width is also effective for maintaining high potential hills even at high voltage, the depletion layer of the Schottky contact junction and the depletion of the P + / N junction as in the conventional structure of FIG. The fact that the layers are connected like the depletion layer region 11 is not an optimum structure for the purpose of maintaining a high potential in the channel 9 region sandwiched by the P + / N junctions.

On the other hand, in the structure of the present invention shown in FIG. 3, the depletion layer 12 from the Schottky contact junction and the depletion layer 13 from the P + / N junction are arranged so as not to contact each other at the zero voltage bias. A depletion layer that satisfies the conditions unique to each of these junctions develops, and the depletion layer extending from the P + / N junction does not become narrow as in the conventional structure, and the electron potential of the channel 9 is as shown in FIG. 2 (b). The potential is higher than that in FIG. 2A, which is improved. Further, even if a reverse bias voltage is applied between the anode A and the cathode C, the above phenomenon is the same, so that the ability to hold a high potential at the time of reverse voltage bias is enhanced.

In the structure of the present invention shown in FIG. 3, since the insulator layer 10 is formed on the side wall of the convex portion, the depletion layer does not develop in the channel 9 sandwiched by the insulator layer 10. Therefore, the channel current during forward voltage bias does not have the current path limitation in the forward depletion layer unlike the conventional structure, and a wide current path can be secured, so the channel series resistance against the forward voltage becomes small and the forward direction is reduced. Significant improvement was also achieved in the characteristics.

(6) The above-described embodiment of the present invention can be modified, modified, changed, etc. within the scope of the present invention. For example, the depressions can be filled with a suitable layer of solid material to prevent mechanical damage to the elevations.

[0016]

As described above, according to the present invention, the electron potential is kept high in the reverse direction without increasing the channel series resistance in the forward direction, and the voltage dependence of the reverse leakage current is eliminated. As a result, it is possible to obtain a high-efficiency and high-speed rectifying semiconductor device, which can be used in a wide range including power supply devices, and the industrial effect is extremely great.

[Brief description of drawings]

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

2A and 2B are electron potential distribution charts, where FIG. 2A shows a conventional structure and FIG. 2B shows a structure of the present invention.

FIG. 3 is a sectional structural view of one embodiment of the present invention.

FIG. 4 is a JR-VR (reverse leakage current-reverse voltage) characteristic diagram.

FIG. 5 is a JF-VF (forward current-forward voltage) characteristic diagram.

[Explanation of symbols]

 1 low resistance one conductivity type semiconductor (eg N +) 2 one conductivity type semiconductor (eg N) 3 guarding region 4 insulating film 5 reverse conductivity type semiconductor (eg P +) (7) 6 metal layer 7 oh Mic electrode 8 Recess of trench groove 9 Channel 10 Insulator layer 11 Depletion layer region 12 First depletion layer 13 Second depletion layer A Anode C Cathode e Schottky contact surface θ angle D depth

Claims (1)

[Claims] 1. A rectifying semiconductor device in which a metal layer in Schottky contact is formed on the upper surface of a projection of a surface of one conductivity type semiconductor having a plurality of trench grooves, and a reverse conductivity type semiconductor region is formed on the bottom of the recess. An insulating layer is formed on the side wall portion, and the opposite conductivity type semiconductor region and the metal layer on the upper surface of the convex portion are electrically connected to the same potential, the metal layer is an anode, and the one conductivity type semiconductor is a cathode. The rectification is characterized in that the depletion layer from the opposite conductivity type semiconductor region extending to the one conductivity type semiconductor side and the depletion layer from the Schottky contact on the upper surface of the convex portion are not connected at least at the time of zero voltage bias. Semiconductor device.