JP2000022177A - Schottky barrier diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Schottky barrier diode(SBD) element with low forward voltage VF by providing levels on the silicon surface for enlarging the Schottky contact area. SOLUTION: An n-type epitaxial layer 12 is formed on a substrate 11, and a ring-shaped p+ guard ring region 15 is formed on the surface of the epitaxial layer 12. An aperture 14 is formed in the oxide film on the surface of the epitaxial layer 12. Steps 18 are formed on the surface of the epitaxial layer 12 in the aperture 14. A barrier metal layer 16 is formed in the aperture 14 to obtain Schottky contact with silicon. Furthermore, an aluminum electrode layer 17 is formed as an external electrode. The barrier metal layer 16 is brought into contact silicon at the sidewall and the bottom of the steps 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Schottky Barrier Diode (SBD).
Specifically, the present invention is to provide an SBD element that can obtain a larger current capacity in the same area.

[0002]

2. Description of the Related Art An SBD is a semiconductor device using a Schottky barrier formed when a predetermined metal layer is brought into contact with a semiconductor layer. It has characteristics of higher speed and smaller forward voltage drop than general PN junction diodes (for example, Japanese Patent Application Laid-Open No. 5-152562).

[0003] Referring to FIG. 4, in the conventional SBD, an N− type epitaxial layer 2 is formed on an N + type semiconductor substrate 1, and a silicon oxide film 3 on the epitaxial layer 2 is opened to open a silicon surface. And the barrier metal layer 4 is brought into contact with the exposed silicon surface. in addition,
An annular P + guard ring region 5 is formed on the surface of the N− type epitaxial layer 2, and the barrier metal layer 3 is covered with an aluminum electrode 6.

In manufacturing a semiconductor device, nickel (Ni), titanium (Ti),
Molybdenum (Mo) is a preferred material. Since each has a unique work function Φ B, most of the SBD characteristics (forward voltage VF, reverse current IR) can be determined by selecting a suitable metal as the barrier metal layer 4. In addition, the impurity concentration of the epitaxial layer 2 and
The diode characteristics of the SBD element are determined by factors such as the area of the Schottky contact surface.

[0005]

In view of the recent trend for lower power consumption, it is particularly desired that the SBD element reduce the forward voltage VF. As a method of reducing the forward voltage VF, there are a method of changing the barrier metal layer 4 to a material having a small work function ΦB, a method of increasing the impurity concentration of the epitaxial layer 2, and the like. If it can flow, it is equivalent to forward current VF
Is reduced. Therefore, it can be said that increasing the Schottky contact area is also an effective means. However, increasing the contact area, that is, increasing the chip area, has the disadvantage of immediately increasing costs.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has provided a metal layer for forming a Schottky barrier on the surface of a silicon layer and covering the surface of the metal with an electrode material. In the Schottky barrier diode, a plurality of steps are provided on the surface of the silicon layer to increase the area of the Schottky contact.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing an SBD according to the present invention. An N− type epitaxial layer 12 is formed on a N + type silicon semiconductor substrate 11 by a vapor phase growth method, and an opening 14 is formed in a silicon oxide film 13 covering the surface of the epitaxial layer 12. An annular P + type guard ring region 15 is formed on the surface of the epitaxial layer 12 near the peripheral end, and a titanium (Ti) layer, for example, is formed as a barrier metal layer 16 on the surface of the epitaxial layer 12 exposed at the opening 14. An aluminum electrode 17 is formed so as to cover 16.

[0009] A plurality of steps 18 are provided on the surface of the epitaxial layer 12 exposed in the opening 14. The step 18 is a silicon step after removing the LOCOS oxide film formed by the selective oxidation method.
It is concave about 1.0μ. Alternatively, a step formed by shaving the silicon surface by anisotropic etching may be used. A large number of steps 18 are provided inside the opening 14,
It is drawn in a pattern such as an island shape or a stripe shape. The barrier metal layer 16 is formed not only on the flat surface of the epitaxial layer 12 but also on the side wall and the bottom of the step 18 to form a Schottky barrier with silicon.

With such a configuration, the contact area between the silicon and the barrier metal layer 16 can be increased by the side wall of the step 18, so that the area of the Schottky barrier can be substantially increased. In the above example, the area of the opening 14 (excluding the portion of the guard ring region 15) is reduced by the step 18
The contact area could be increased by about 20%. Therefore, the value of the forward current IF per unit area can be increased, and the current capacity of the element can be increased. This means that the chip area is increased, so that the forward voltage VF when a certain forward current IF flows can be reduced, and the chip area does not increase.

FIGS. 2 and 3 are cross-sectional views for explaining an example of the manufacturing method.

First, referring to FIG. 2A, an N + type semiconductor substrate 11 on which an epitaxial layer 12 having a specific resistance ρ of 0.5 to 2.0 Ω · cm and a thickness of 2 to 10 μm is prepared. An annular P + guard ring region 15 is formed on the surface of the epitaxial layer 12 by selective diffusion.

Referring to FIG. 2B, after removing the oxide film covering the surface of epitaxial layer 12, initial oxide film 2 is removed.
0 is formed, a silicon nitride film is formed on the initial oxide film 20, and the silicon nitride film is patterned to form an oxidation resistant film 21.

Referring to FIG. 2C, by selectively oxidizing the entire substrate, a thick LOC having a thickness of 1.0 to 2.0 μm is formed on the surface of epitaxial layer 12 not covered with oxidation-resistant film 21.
An OS oxide film 22 is formed.

Referring to FIG. 3D, a resist mask for covering the area other than the opening 14 is formed, and the LOCOS oxide film 22 in the opening 14 is removed by a wet etchant. Thus, the LOCOS oxide film 2 is formed on the surface of the opening 14.
A step 18 can be formed having a depth corresponding to the depth of the oxide layer 2 oxidized downward from the surface of the epitaxial layer 12.

Referring to FIG. 3A, a film thickness of 300 to 20 is formed in the opening 14 in which the step 18 is formed by the sputter deposition method.
A Ti layer of 00 ° is deposited, and the deposited Ti layer is patterned by a known photoetching method to form a barrier metal layer 16.

Referring to FIG. 3B, an aluminum layer having a thickness of 1.0 to 3.0 .mu.m is deposited again by the sputter deposition method, and the barrier metal layer 16 is covered by photoetching and pads for external connection are formed. An aluminum layer 17 is formed to obtain the structure shown in FIG.

In the above-described embodiment, the barrier metal layer 16 has been described with Ti, but it is needless to say that the present invention can be implemented with other barrier metals, such as Ni and Mo.

[0019]

As described above, according to the present invention, by providing the step 18 in the opening 14, the Schottky contact area between the barrier metal layer 16 and silicon can be increased. As a result, when the openings 14 have the same area and are compared, a large amount of forward current IF can flow even with the same forward voltage VF. As a result, the forward voltage VF
This has the advantage that an SBD device with a small value can be obtained.
Further, since the area of the opening 14 is not increased, an element having a larger current capacity can be obtained without increasing the pellet size.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining the present invention.

FIG. 2 is a cross-sectional view for explaining a manufacturing method.

FIG. 3 is a cross-sectional view for explaining a manufacturing method.

FIG. 4 is a cross-sectional view for explaining a conventional example.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Rimaro Koike 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. F-term (reference) 4M104 AA01 BB02 BB05 BB14 BB16 CC03 FF17 FF22 GG03

Claims (2)

[Claims] 1. A Schottky barrier diode in which a barrier metal layer for forming a Schottky barrier with the silicon layer is provided on the surface of the silicon layer, and the metal layer is covered with an electrode material. A Schottky barrier diode characterized in that the area of Schottky contact is increased by providing a plurality of steps. 2. The Schottky barrier diode according to claim 1, wherein said step is obtained by removing a LOCOS oxide film.