JP5435922B2 - Manufacturing method of Schottky barrier diode - Google Patents

Description

The present invention relates to the production how the Schottky barrier diode thereby reducing the leakage current when a reverse voltage is applied.

When an oxide film is used as an insulating film of a device such as a Schottky barrier diode, the reliability of the oxide film when a reverse voltage is applied depends on the interface state between the oxide film and the semiconductor layer. For example, in a SiC (silicon carbide) oxide film, the interface state density is high, and a leakage current flows through the interface state, so that the reliability is poor. On the other hand, in an oxide film containing N (nitrogen) as a constituent element (hereinafter referred to as a NO oxide film), N atoms terminate at dangling bonds present at the interface, so the density of interface states is low. High reliability. As an example of applying this NO oxide film to a device, Patent Document 1 describes a TFT (Thin Film Transistor) using an NO oxide film as a gate insulating film.
JP-A-8-78693

  However, when a NO oxide film is applied to a SiC Schottky barrier diode having a semiconductor layer made of SiC, there is a problem that leakage current at the time of applying a reverse voltage is higher than when an oxygen oxide film is applied. Hereinafter, the cause of this problem will be described.

  As shown in FIG. 4, in the manufacturing process of the conventional SiC Schottky barrier diode, a guard ring 101 made of SiC containing P-type impurities is formed on the surface of a semiconductor layer 100 made of SiC containing low-concentration N-type impurities. Further, an NO oxide film 102 is formed on the semiconductor layer 100 and the guard ring 101 (FIG. 4A). N atoms 103 are accumulated on the surface of the semiconductor layer 100 after the NO oxide film 102 is formed.

  Subsequently, the NO oxide film 102 corresponding to the position where the electrode is to be formed is removed, and a contact hole is formed (FIG. 4B). An electrode 104 is formed on the semiconductor layer 100 and the guard ring 101 exposed by this process (FIG. 4C). A Schottky junction is formed between the semiconductor layer 100 and the electrode 104.

  N atoms 103 remain on the surface of the semiconductor layer exposed after the contact holes for electrodes are formed in the NO oxide film 102. When the reverse voltage is applied, the N atom 103 acts as an N-type dopant, and current flows easily. Therefore, it is considered that the leakage current when the reverse voltage is applied increases. As described above, the NO oxide film has the property that the density of the interface state is low and the reliability when the reverse voltage is applied can be improved, but the conventional SiC Schottky barrier diode can exhibit the property. Not.

  The present invention has been made in view of the above, and an object of the present invention is to provide a Schottky barrier diode manufacturing method and a Schottky barrier diode that can reduce a leakage current when a reverse voltage is applied.

The present invention has been made to solve the above-described problems. A first step of forming an oxide film containing silicon carbide, oxygen, and nitrogen on a semiconductor layer made of silicon carbide; and A second step of forming a through-hole, a third step of removing nitrogen atoms by treating the surface of the semiconductor layer exposed in the second step with oxygen plasma, and the third step. A fourth step of forming an electrode for forming a Schottky junction with the semiconductor layer on the semiconductor layer from which nitrogen atoms on the surface have been removed, and a method for manufacturing a Schottky barrier diode, comprising: is there.

  According to the method for manufacturing a Schottky barrier diode of the present invention, since nitrogen atoms on the surface of the semiconductor layer located in contact with the electrode are removed, leakage current when a reverse voltage is applied can be reduced.

In addition, in the first method, the Schottky barrier diode manufacturing method of the present invention includes annealing in a gas atmosphere containing N atoms and O atoms after forming an oxide film by dry oxidation, so that silicon carbide, oxygen, And an oxide film containing nitrogen is formed.

  According to the method for manufacturing a Schottky barrier diode of the present invention, by treating the surface of the semiconductor layer with oxygen plasma, the leakage current when applying a reverse voltage can be greatly reduced.

Further, in the method for manufacturing a Schottky barrier diode of the present invention, in the first step, after forming an oxide film by dry oxidation, reoxidation annealing is performed in a gas atmosphere containing N atoms and O atoms, An oxide film containing oxygen and nitrogen is formed.

According to the method for manufacturing a Schottky barrier diode of the present invention, since the nitrogen atoms on the surface of the semiconductor layer located in contact with the electrode are removed, it is possible to reduce the leakage current when a reverse voltage is applied.

  According to the present invention, it is possible to reduce the leakage current when a reverse voltage is applied.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a method of manufacturing a SiC Schottky barrier diode according to an embodiment of the present invention. The following manufacturing method is an example, and it is not necessary to limit to this.

  First, a substrate constituting the semiconductor layer 1 made of SiC containing an N-type impurity is prepared (FIG. 1A). A guard ring 2 is formed by injecting a P-type impurity into the surface of the semiconductor layer 1 and performing annealing (FIG. 1B). Further, an NO oxide film 3 is formed on the semiconductor layer 1 and the guard ring 2 (FIG. 1C). The NO oxide film 3 contains SiC, O, and N as constituent elements. As a method for forming the NO oxide film 3, for example, after dry oxidation is performed in an oxygen atmosphere, annealing may be performed in an atmosphere of nitrogen monoxide containing N and O as constituent elements. Alternatively, the NO oxide film 3 may be formed by performing oxidation in an atmosphere such as nitrogen monoxide. N atoms 4 accumulate on the surface of the semiconductor layer 1 after the formation of the NO oxide film 3.

  When the NO oxide film 3 is formed, an NO oxide film is also formed on the back surface of the semiconductor layer 1, but the illustration is omitted in FIG. 1. After the formation of the NO oxide film 3, a protective resist is deposited on the NO oxide film 3, and the NO oxide film on the back surface of the semiconductor layer 1 can be removed by BHF (Buffered HF). The process of removing the NO oxide film on the back surface of the semiconductor layer 1 is not shown in FIG. Subsequently, a metal material such as Ni (nickel) is deposited on the back surface of the semiconductor layer 1 by vapor deposition or the like to form the electrode 5 (FIG. 1D). After the formation of the electrode 5, heat treatment may be performed in order to improve the ohmic contact between the semiconductor layer 1 and the electrode 5.

  Subsequently, the NO oxide film 3 corresponding to the position where the electrode is formed is removed by BHF, and a contact hole (hole) penetrating the NO oxide film 3 is formed (FIG. 2A). N atoms 4 remain on the surface of the semiconductor layer 1 exposed by forming the contact holes. The surface of the semiconductor layer 1 is treated with the oxygen plasma 6 and reacted with the N atoms 4 remaining on the surface of the semiconductor layer 1 to remove the N atoms 4 (FIG. 2B). Subsequently, a metal material such as Ni or Ti (titanium) is deposited by vapor deposition or the like on the semiconductor layer 1 and the guard ring 2 exposed by forming the contact hole to form the electrode 7 (FIG. 2C). . A Schottky junction is formed between the semiconductor layer 1 and the electrode 7. The electrode 7 may have a single layer structure or a structure composed of a plurality of layers.

  FIG. 3 shows the leakage current with respect to the reverse voltage. When the treatment with oxygen plasma is performed after the NO oxide film 3 is removed, the value of the leakage current is reduced by about one digit compared with the case where the treatment with oxygen plasma is not performed.

  As another method of removing the N atoms 4 on the surface of the semiconductor layer 1, the surface of the semiconductor layer 1 is oxidized for a short time at 900 ° C. to 1100 ° C. after the NO oxide film 3 is removed. Sacrificial oxidation removed by BHF may be performed.

  As described above, according to the present embodiment, it is possible to reduce a leakage current when a reverse voltage is applied. In particular, after removing the NO oxide film, the leakage current can be greatly reduced by treating the surface of the semiconductor layer with oxygen plasma and removing N atoms on the surface of the semiconductor layer. Therefore, high reliability at the time of applying the reverse voltage inherent to the NO oxide film can be exhibited.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the above-described embodiments, and includes design changes and the like without departing from the gist of the present invention. .

It is a schematic cross section for demonstrating the manufacturing method of the Schottky barrier diode by one Embodiment of this invention. It is a schematic cross section for demonstrating the manufacturing method of the Schottky barrier diode by one Embodiment of this invention. 4 is a graph for explaining leakage current characteristics of a Schottky barrier diode according to an embodiment of the present invention. It is a schematic cross section for demonstrating the manufacturing method of the conventional Schottky barrier diode.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,100 ... Semiconductor layer, 2,101 ... Guard ring, 3,102 ... NO oxide film, 4,103 ... N atom, 5, 7, 104 ... Electrode, 6 ...・ Oxygen plasma

Claims (3)

A first step of forming an oxide film containing silicon carbide, oxygen, and nitrogen on a semiconductor layer made of silicon carbide;
A second step of forming a hole penetrating the oxide film;
A third step of removing nitrogen atoms by treating the surface of the semiconductor layer exposed in the second step with oxygen plasma;
A fourth step of forming an electrode for forming a Schottky junction with the semiconductor layer on the semiconductor layer from which nitrogen atoms on the surface have been removed by the third step;
A method for manufacturing a Schottky barrier diode, comprising: In the first step, an oxide film containing silicon carbide, oxygen, and nitrogen is formed by annealing in a gas atmosphere containing N atoms and O atoms after forming the oxide film by dry oxidation.
The method of manufacturing a Schottky barrier diode according to claim 1. In the first step, after forming an oxide film by dry oxidation, re-oxidation annealing is performed in a gas atmosphere containing N atoms and O atoms, thereby forming an oxide film containing silicon carbide, oxygen, and nitrogen.
The method of manufacturing a Schottky barrier diode according to claim 1.

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