JPS6086873A - Semiconductor device - Google Patents

Abstract

PURPOSE:To produce a semiconductor device of larger space with high reliability by a method wherein electrodes forming Schottky junctions are discontinuously formed. CONSTITUTION:An n<+> layer, an n layer and a p<+> layer are formed on a semiconductor substrate 1. A schottky electrodes 30 are discontinuously formed partially coming into contact with the n layer. Besides, these Schottky electrode 30 are short-circuited by an anode electrode 22 coming into ohmic contact with the n layer. When the anode electrode 22 and a cathode electrode 21 are respectively supplied with minus and plus potentials, the current flowing through an ohmic junction 200 may be reduced by a depletion layer of a Schottky junctions 300 to block the supplied voltage. When said electrodes are supplied with reverse potentials, they are made conductive. Through these procedures, a semiconductor of larger space with high reliability may be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a semiconductor device, particularly a diode having a Schottky junction.

[Background of the invention]

FIG. 1 shows a conventional Schottky diode, which is one of the semiconductor devices having a Schottky junction. In FIG. 1, a semiconductor substrate 1 includes, for example, an n-type conductive layer adjacent to an n-9-type conductive layer. On the main surface on the n-layer side, an electrode 30 forming a Schottky junction with the n-layer is laminated, and an anode electrode 22 is further adhered.

40 is an insulating film such as 810a. Generally, the insulating film 4
90 layers are provided at the boundary between Schottky electrode 30 and Schottky electrode 30, and the structure is such that the electric field distributed around the Schottky electrode 30 is relaxed. A cathode electrode 21 is formed on the other main surface on the n0 side of the base 1 and is in contact with the cathode electrode 21 with low resistance.

When such a Schottky diode is subjected to a thermal fatigue test, leakage current increases when a reverse voltage is applied over time, causing deterioration of reverse characteristics.

This is caused by thermal stress due to the difference in thermal expansion coefficient between the Schottky electrode 30 and silicon, which is one of the semiconductor substrates, and by this thermal stress, due to the cold heat cycle in the thermal fatigue test. peripheral area and 5fO
It is thought that as a result of the generation of stress in the vicinity of the boundary of the S film 40, the number of interface units increased and the leakage current increased. If the thermal fatigue test is continued further, cracks and peeling will occur.

In order to prevent such racking and peeling, a method has been adopted in which the Schottky electrode is made of MO or W, which is a substance having a coefficient of thermal expansion close to that of silicon. However, when increasing the junction area of the Schottky electrode in order to increase the current, this effect was not sufficient, and a highly reliable Schottky diode could not be obtained.

[Purpose of the invention]

An object of the present invention is to provide a semiconductor device having a Schottky junction that solves the above-mentioned conventional drawbacks and improves reliability. [Summary of the Invention] The present invention is characterized by This is due to the fact that it was formed discontinuously.

[Embodiments of the invention]

FIG. 2 shows an embodiment of the invention. On the semiconductor substrate 1, an n-layer and an n-%p'' layer are formed, and the Schottky electrode 30 is partially in contact with the n-layer.These Schottky electrodes are in ohmic contact with the n-layer. It is short-circuited by the anode electrode 22.Anode electrode 22
When a negative potential is applied to , and a positive potential is applied to cathode electrode 21 , the depletion layer of Schottky junction 300 can reduce the current flowing through ohmic junction 200 and block the applied voltage.

Conversely, if a positive potential is applied to the anode electrode 22 and a negative potential is applied to the cathode electrode 21, the ohmic junction 20
0 and Schottky junction, and becomes conductive. In order to provide such rectification characteristics, it is necessary to increase the distance between the Schottky electrodes.

FIG. 3 shows the preferred distance range necessary to obtain rectifying characteristics. The distance varies depending on the carrier concentration of the n-layer and the barrier height of the Schottky junction, but for example,
Carrier concentration in n layer 3x1015-3, barrier height 0
．． At 9 V, L needs to be less than 1.2 μm.

The structure is as shown in Fig. 2, and for example, A
Au-8b for t1 anode electrode, MO for Schottky electrode
When forming a Schottky junction, the strain caused by %Au-
Since it can be relaxed with an ohmic electrode made of soft metal such as 8B, it was possible to prevent cracking, peeling, and increase in leakage current even in thermal fatigue tests. As a result, the Schottky junction area can be increased, and the conventional 60A
Even with Schottky diodes, which had a limit of 200
We were able to obtain a large-area, highly reliable element that can rectify a current of more than A. Furthermore, Schottky electrodes include not only MO and W, which have a coefficient of thermal expansion almost equal to f3i, but also P'# P d m N i *Cr, which has a different coefficient of thermal expansion, etc.
Furthermore, a thermally stable metal silicide such as Ti5f2 can also be used. As a result, it is possible not only to obtain a Schottky diode that is resistant to thermal fatigue tests, but also to obtain a Schottky diode having an arbitrary Schottky barrier height other than Mo (0.67 V) or W (0.68 V). I can do it. For example, by selecting Mg as the Schottky metal, the height of the barrier can be made as low as 0.4V, and forward loss can be reduced. On the other hand, by using PT and setting the height of the barrier to 0.9V, leakage current in the reverse direction can also be reduced. In this way, the present invention has the advantage that any metal can be selected depending on the application. Furthermore, since the forward current also flows through an ohmic junction with low contact resistance, there is an effect that the voltage drop in the forward direction is reduced.

FIG. 4 is an example of a planar pattern diagram of the side surface having the Schottky junction and ohmic junction in FIG. 2. When the Schottky junctions 300 and the ohmic junctions 200 are arranged alternately in a stripe pattern, and an electric current is applied in the opposite direction, the depletion layer formed by the Schottky junctions can block the current that attempts to flow through the ohmic junctions. It has a structure.

FIG. 5 is another planar pattern diagram. Schottky junctions 300 and ohmic junctions 200 are alternately arranged within the grid-like frame. This makes it possible to further reduce the strain that occurs in the longitudinal direction of the striped shape in FIG.
Furthermore, it is advantageous for increasing the area.

FIG. 6 shows another embodiment of the invention. The difference from the embodiment shown in FIG. 2 is that the Schottky junction 300 is formed in a concave shape. As a result, the depletion layer of the Schottky junction becomes more effective in blocking the current that attempts to flow through the ohmic junction when a voltage is applied in the opposite direction, without sacrificing the high reliability associated with thermal fatigue tests. Furthermore, it was confirmed that the leakage current in the reverse direction could be reduced.

FIG. 7 shows another embodiment in which an ohmic junction region K n '' layer is provided. This makes it possible to obtain an ohmic junction with an even lower resistance, resulting in less loss.
By forming eight layers, inexpensive At could be used instead of the expensive Au-8b electrode. According to this example, it is possible to obtain a Schottky diode of the present invention in which a low-resistance and inexpensive ohmic junction is formed.

The present invention is applicable not only to Schottky diodes but also to all semiconductor devices having Schottky junctions.

〔Effect of the invention〕

As described above, according to the present invention, a highly reliable semiconductor device that can have a large area can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a conventional Schottky diode, FIG. 2 is a schematic sectional view of a Schottky diode of the present invention, FIG. 3 is a diagram showing the relationship between the distance between Schottky electrodes and the carrier concentration of the n-layer, and FIG. 5 and 5 are planar pattern diagrams of a Schottky junction and an ohmic junction surface, and FIGS. 6 and 7 are schematic sectional views showing other embodiments of the present invention. Figure 1 is also between 2 days and 3 figures 1/-3t N electric bottom. Positive high pressure, [Ipaku Prison 6th also q figure

Claims (1)

[Claims] 1. A semiconductor substrate in which a layer of one conductivity type is exposed on one main surface, a first electrode provided on one main surface to form a Schottky junction, and an ohmic layer separated from the first electrode and attached to the semiconductor substrate. A semiconductor device comprising a second electrode in contact with the Schottky junction, the Schottky junction being formed discontinuously.