Oxide semiconductor device and method for manufacturing oxide semiconductor device

文档序号：1449574 发布日期：2020-02-18 浏览：30次中文

阅读说明：本技术 氧化物半导体装置以及氧化物半导体装置的制造方法 (Oxide semiconductor device and method for manufacturing oxide semiconductor device ) 是由汤田洋平绵引达郎古川彰彦于 2018-06-08 设计创作，主要内容包括：在抑制异种材料向肖特基界面扩散的同时,提高被施加反向电压时的耐压。氧化物半导体装置具备：n型的氧化镓外延层(2)；p型的氧化物半导体层(5),是与氧化镓外延层的材料不同的材料的氧化物；电介体层(7),以覆盖氧化物半导体层的侧面的至少一部分的方式形成；阳极电极(4)；以及阴极电极(3),在氧化物半导体层的下表面与氧化镓基板(1)之间或者氧化物半导体层(5a)的下表面与氧化镓外延层(2)之间形成异质pn结。(The diffusion of a different material to a Schottky interface is suppressed, and the withstand voltage when a reverse voltage is applied is improved. The oxide semiconductor device includes: an n-type gallium oxide epitaxial layer (2); a p-type oxide semiconductor layer (5) which is an oxide of a material different from that of the gallium oxide epitaxial layer; a dielectric layer (7) formed so as to cover at least a part of a side surface of the oxide semiconductor layer; an anode electrode (4); and a cathode electrode (3) that forms a hetero-pn junction between the lower surface of the oxide semiconductor layer and the gallium oxide substrate (1) or between the lower surface of the oxide semiconductor layer (5a) and the gallium oxide epitaxial layer (2).)

1. An oxide semiconductor device includes:

an n-type gallium oxide epitaxial layer (2) formed on the upper surface of the n-type gallium oxide substrate (1);

a p-type oxide semiconductor layer (5, 5a) which is formed at least from the upper surface to the inside of the gallium oxide epitaxial layer (2) and is an oxide of a material different from that of the gallium oxide epitaxial layer (2);

a dielectric layer (7, 7a, 7b) that is formed so as to cover at least a part of a side surface of the oxide semiconductor layer (5, 5a) and is made of a material having a dielectric constant lower than that of the material constituting the oxide semiconductor layer (5, 5 a);

an anode electrode (4) which is formed on the upper surface of the gallium oxide epitaxial layer (2) and forms a Schottky junction with the gallium oxide epitaxial layer (2); and

a cathode electrode (3) formed on the lower surface of the gallium oxide substrate (1) and in ohmic contact with the gallium oxide substrate (1),

a hetero pn junction is formed between the lower surface of the oxide semiconductor layer (5) and the gallium oxide substrate (1) or between the lower surface of the oxide semiconductor layer (5a) and the gallium oxide epitaxial layer (2).

2. The oxide semiconductor device according to claim 1,

the side surfaces of the oxide semiconductor layers (5, 5a) are surfaces along a current flow direction that is a direction connecting the anode electrode (4) and the cathode electrode (3).

3. The oxide semiconductor device according to claim 1 or 2, wherein,

the lower surfaces of the dielectric layers (7a, 7b) are located shallower than the lower surfaces of the oxide semiconductor layers (5, 5 a).

4. The oxide semiconductor device according to claim 1 or 2, wherein,

the dielectric layers (7, 7a) are formed so as to cover the entire side surfaces of the oxide semiconductor layers (5, 5 a).

5. The oxide semiconductor device according to any one of claims 1 to 4,

the oxide semiconductor layer (5a) is formed from the upper surface to the inside of the gallium oxide epitaxial layer (2),

a hetero pn junction is formed between the lower surface of the oxide semiconductor layer (5a) and the gallium oxide epitaxial layer (2).

6. The oxide semiconductor device according to any one of claims 1 to 4,

the oxide semiconductor layer (5) is formed from the upper surface to the lower surface of the gallium oxide epitaxial layer (2),

a hetero pn junction is formed between the lower surface of the oxide semiconductor layer (5) and the gallium oxide substrate (1).

7. The oxide semiconductor device according to any one of claims 1 to 6,

the impurity concentration of the gallium oxide epitaxial layer (2) is lower than that of the gallium oxide substrate (1).

8. The oxide semiconductor device according to any one of claims 1 to 7,

the oxide semiconductor layer (5, 5a) is a metal oxide containing Cu or Ni.

9. A method for manufacturing an oxide semiconductor device, wherein,

a cathode electrode (3) which is ohmically bonded to the gallium oxide substrate (1) is formed on the lower surface of the n-type gallium oxide substrate (1),

epitaxially growing an n-type gallium oxide epitaxial layer (2) on the upper surface of the gallium oxide substrate (1),

forming a groove portion (10) extending from the upper surface of the gallium oxide epitaxial layer (2) to at least the inside,

forming dielectric layers (7, 7a, 7b) on at least a part of side surfaces of the groove (10),

forming p-type oxide semiconductor layers (5, 5a) which are oxides of a material different from the material of the gallium oxide epitaxial layer (2) and are made of a material having a higher dielectric constant than the dielectric layers (7, 7a, 7b) in the groove portions (10) in a state in which the dielectric layers (7, 7a, 7b) are formed on the side surfaces thereof,

an anode electrode (4) which is in Schottky junction with the gallium oxide epitaxial layer (2) is formed on the upper surface of the gallium oxide epitaxial layer (2),

10. The method for manufacturing an oxide semiconductor device according to claim 9,

the oxide semiconductor layer (5, 5a) is formed at a formation temperature of 200 ℃ or lower.

11. The method for manufacturing an oxide semiconductor device according to claim 9 or 10,

forming a groove portion (10) reaching the inside from the upper surface of the gallium oxide epitaxial layer (2),

a hetero pn junction is formed between the lower surface of the oxide semiconductor layer (5a) and the gallium oxide epitaxial layer (2).

12. The method for manufacturing an oxide semiconductor device according to claim 9 or 10,

forming a groove portion (10) extending from the upper surface to the lower surface of the gallium oxide epitaxial layer (2),

a hetero pn junction is formed between the lower surface of the oxide semiconductor layer (5) and the gallium oxide substrate (1).

13. A method for manufacturing an oxide semiconductor device, wherein,

a cathode electrode (3) which is ohmically bonded to the gallium oxide substrate (1) is formed on the lower surface of the n-type gallium oxide substrate (1),

epitaxially growing an n-type 1 st gallium oxide epitaxial layer (2a) on the upper surface of the gallium oxide substrate (1),

a p-type oxide semiconductor layer (5a) which is an oxide of a material different from that of the 1 st gallium oxide epitaxial layer (2a) is partially formed on the upper surface of the 1 st gallium oxide epitaxial layer (2a),

forming a dielectric layer (7, 7a, 7b) made of a material having a dielectric constant smaller than that of the material constituting the oxide semiconductor layer (5a) on at least a part of a side surface of the oxide semiconductor layer (5a),

epitaxially growing an n-type 2 nd gallium oxide epitaxial layer (2b) so as to cover the 1 st gallium oxide epitaxial layer (2a), the oxide semiconductor layer (5a), and the dielectric layers (7, 7a, 7b),

an anode electrode (4) which is in Schottky junction with the 2 nd gallium oxide epitaxial layer (2b) is formed on the upper surface of the 2 nd gallium oxide epitaxial layer (2b),

a hetero pn junction is formed between the lower surface of the oxide semiconductor layer (5a) and the upper surface of the 1 st gallium oxide epitaxial layer (2 a).

14. An oxide semiconductor device includes:

an n-type gallium oxide epitaxial layer (2c) formed on the upper surface of the n-type gallium oxide substrate (1);

a p-type oxide semiconductor layer (5c) which is formed at least from the upper surface to the inside of the gallium oxide epitaxial layer (2c) and is an oxide of a material different from that of the gallium oxide epitaxial layer (2 c);

a dielectric layer (7c) that is formed so as to cover at least a part of a side surface of the oxide semiconductor layer (5c) and is made of a material having a dielectric constant lower than that of the material that constitutes the oxide semiconductor layer (5 c);

a source electrode (11) which is formed on the upper surface of the gallium oxide epitaxial layer (2c) and is directly bonded to the gallium oxide epitaxial layer (2c) and the oxide semiconductor layer (5 c);

a gate electrode (12) in contact with the gallium oxide epitaxial layer (2c) and the oxide semiconductor layer (5c) through the dielectric layer (7 c); and

a drain electrode (13) formed on the lower surface of the gallium oxide substrate (1) and directly bonded to the gallium oxide substrate (1),

a hetero pn junction is formed between the lower surface of the gallium oxide epitaxial layer (2c) and the gallium oxide substrate (1).

Technical Field

The technology disclosed in the present specification relates to an oxide semiconductor device and a method for manufacturing the oxide semiconductor device.

Background

Power Electronics (PE) is a technology for rapidly and efficiently converting dc, ac, or frequency, and is a term representing a technology that integrates recent semiconductor-based electronic engineering (electronic engineering) and control engineering (control engineering) in addition to conventional power engineering (power engineering).

PE is a technology that is currently applied to power utilization, industrial utilization, transportation, household utilization, and other power utilization scenarios.

In recent years, the percentage of electric energy in the total energy consumption, that is, the power factor, has been increasing in japan as well as in the world. In recent years, devices excellent in convenience and energy saving have been developed for use of electric power, and the utilization rate of electric power has been improved. The technology that underlies these foundations is PE technology.

In addition, the PE technology can also be said to be the following technology: the electric state (for example, the magnitude of frequency, current, or voltage) to be converted is converted into an electric state suitable for the device to be used, regardless of the state. The basic elements in PE technology are a rectifier and an inverter. These elements are based on semiconductors, and are semiconductor elements such as diodes and transistors using semiconductors.

In the PE field, diodes as semiconductor rectifier devices are currently used for various applications including electrical devices. Also, the diode is applied to a wide range of frequency bands.

In recent years, switching elements which can operate at high frequencies with low loss have been developed and put to practical use for applications with high withstand voltage and large capacity. In addition, the material used is also changed to a wide band gap material, and high withstand voltage of the device is achieved.

Typical examples of such diodes include Schottky Barrier Diodes (SBDs) and pn diodes (PNDs), and these diodes are widely used for various applications.

For example, a semiconductor device having a merged P-i-n/schottky diode (MPS, hybrid P-i-n schottky diode) structure in which a schottky junction and a pn junction are provided as exemplified in patent document 1 has been developed.

In the MPS structure, a surge current larger than a rated value can be caused to flow with a small voltage drop as compared with the case of the SBD alone by bipolar operation of the PND. Thus, in the MPS configuration, the forward surge tolerance is improved. Thus, a semiconductor device having a rectifying function with high forward surge tolerance while suppressing an increase in forward voltage drop has been developed.

Further, as exemplified in patent document 2, the concentration of the electric field in the bottom of the trench can be alleviated by a depletion layer generated from the pn junction at the interface between the termination structure and the drift layer. Thus, a semiconductor device has been developed which can reduce the forward voltage and reverse leakage current of the semiconductor device and can easily perform a rectifying operation.

Disclosure of Invention

In the semiconductor device exemplified in patent document 1, grooves reaching from the interface between the pn materials constituting the MPS structure to the lower side are formed between the pn materials. With such a configuration, an increase in voltage drop in the forward direction is suppressed, while there is a problem that the withstand voltage when a reverse voltage is applied is lowered.

In the semiconductor device using SiC exemplified in patent document 2, it is assumed that a pn junction is formed using the same material, and the material used in the semiconductor layer is not assumed to be an oxide. In the case of using an oxide material, it is necessary to prevent diffusion of metal atoms and the like to the schottky interface. In addition, the p-type oxide semiconductor has a problem that a countermeasure against the loss of p-type conductivity due to oxidation is insufficient.

The technology disclosed in the present specification has been made to solve the above-described problems, and an object thereof is to provide a technology for improving a withstand voltage when a reverse voltage is applied while suppressing diffusion of a dissimilar material to a schottky interface in an oxide semiconductor device formed of an oxide semiconductor material.

The technology disclosed in the present specification, according to claim 1, comprises: an n-type gallium oxide epitaxial layer formed on the upper surface of the n-type gallium oxide substrate; a p-type oxide semiconductor layer which is formed at least from the upper surface to the inside of the gallium oxide epitaxial layer and is an oxide of a material different from that of the gallium oxide epitaxial layer; a dielectric layer formed so as to cover at least a part of a side surface of the oxide semiconductor layer, and made of a material having a dielectric constant lower than that of the material constituting the oxide semiconductor layer; an anode electrode formed on the upper surface of the gallium oxide epitaxial layer and forming a Schottky junction with the gallium oxide epitaxial layer; and a cathode electrode formed on a lower surface of the gallium oxide substrate and ohmic-bonded to the gallium oxide substrate, wherein a hetero-pn junction is formed between the lower surface of the oxide semiconductor layer and the gallium oxide substrate or between the lower surface of the oxide semiconductor layer and the gallium oxide epitaxial layer.

In addition, according to the 2 nd aspect of the technology disclosed in the present specification, a cathode electrode that is ohmically bonded to an n-type gallium oxide substrate is formed on a lower surface of the n-type gallium oxide substrate, an n-type gallium oxide epitaxial layer is epitaxially grown on an upper surface of the gallium oxide substrate to form a groove portion that extends from the upper surface of the gallium oxide epitaxial layer to at least an inner portion, a dielectric layer is formed on at least a part of a side surface of the groove portion, a p-type oxide semiconductor layer that is an oxide of a material different from the material of the gallium oxide epitaxial layer and is made of a material having a higher dielectric constant than the dielectric layer is formed in the groove portion in a state in which the dielectric layer is formed on the side surface, and an anode electrode that is schottky-bonded to the gallium oxide epitaxial layer is formed on the upper surface of the gallium oxide epitaxial layer, and forming a hetero pn junction between the lower surface of the oxide semiconductor layer and the gallium oxide substrate or between the lower surface of the oxide semiconductor layer and the gallium oxide epitaxial layer.

In addition, the 4 th aspect of the technology disclosed in the present specification includes: an n-type gallium oxide epitaxial layer formed on the upper surface of the n-type gallium oxide substrate; a p-type oxide semiconductor layer which is formed at least from the upper surface to the inside of the gallium oxide epitaxial layer and is an oxide of a material different from that of the gallium oxide epitaxial layer; a dielectric layer formed so as to cover at least a part of a side surface of the oxide semiconductor layer, and made of a material having a dielectric constant lower than that of the material constituting the oxide semiconductor layer; a source electrode formed on an upper surface of the gallium oxide epitaxial layer and directly bonded to the gallium oxide epitaxial layer and the oxide semiconductor layer; a gate electrode in contact with the gallium oxide epitaxial layer and the oxide semiconductor layer through the dielectric layer; and a drain electrode formed on a lower surface of the gallium oxide substrate and directly bonded to the gallium oxide substrate, wherein a hetero-pn junction is formed between the lower surface of the gallium oxide epitaxial layer and the gallium oxide substrate.

In addition, according to the 3 rd aspect of the technology disclosed in the present specification, a cathode electrode that is ohmically bonded to an n-type gallium oxide substrate is formed on a lower surface of the n-type gallium oxide substrate, an n-type 1 st gallium oxide epitaxial layer is epitaxially grown on an upper surface of the gallium oxide substrate, a p-type oxide semiconductor layer that is an oxide of a material different from that of the 1 st gallium oxide epitaxial layer is partially formed on the upper surface of the 1 st gallium oxide epitaxial layer, a dielectric layer made of a material having a lower dielectric constant than the material constituting the oxide semiconductor layer is formed on at least a part of a side surface of the oxide semiconductor layer, an n-type 2 nd gallium oxide epitaxial layer is epitaxially grown so as to cover the 1 st gallium oxide epitaxial layer, the oxide semiconductor layer, and the dielectric layer, and an n-type 2 nd gallium oxide epitaxial layer is epitaxially grown on an upper surface of the 2 nd gallium oxide epitaxial layer, an anode electrode is formed to be schottky-bonded to the 2 nd gallium oxide epitaxial layer, and a hetero pn junction is formed between a lower surface of the oxide semiconductor layer and an upper surface of the 1 st gallium oxide epitaxial layer. With this structure, in the manufacture of an oxide semiconductor device in which a heterogeneous pn junction is formed from different oxide semiconductor materials, a p-type semiconductor layer can be formed without performing p-type carrier concentration control by adding a p-type impurity. Specifically, the above structure can be realized by partially forming a p-type oxide semiconductor layer and a dielectric layer on the upper surface of an n-type gallium oxide epitaxial layer and epitaxially growing the n-type gallium oxide epitaxial layer again so as to fill the gap between the oxide semiconductor layers.

Objects, features, aspects and advantages related to the technology disclosed in the present specification will become more apparent from the detailed description and the accompanying drawings shown below.

Drawings

Fig. 1 is a plan view schematically illustrating a structure for realizing a semiconductor device according to an embodiment.

Fig. 2 is a cross-sectional view schematically illustrating the structure of the semiconductor device in section I-I' of fig. 1.

Fig. 3 is a sectional view schematically illustrating the structure of the semiconductor device according to the embodiment.

Fig. 4 is a sectional view schematically illustrating the structure of the semiconductor device according to the embodiment.

Fig. 5 is a sectional view illustrating a manufacturing process of a semiconductor device according to an embodiment.

Fig. 6 is a sectional view illustrating a manufacturing process of a semiconductor device according to an embodiment.

Fig. 7 is a sectional view illustrating a manufacturing process of a semiconductor device according to an embodiment.

Fig. 8 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 9 is a sectional view illustrating a manufacturing process of a semiconductor device according to an embodiment.

Fig. 10 is a sectional view illustrating a manufacturing process of a semiconductor device according to an embodiment.

Fig. 11 is a sectional view illustrating a manufacturing process of a semiconductor device according to an embodiment.

Fig. 12 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 13 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 14 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 15 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 16 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 17 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 18 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 19 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 20 is a sectional view illustrating a manufacturing process of a semiconductor device according to the embodiment.

Fig. 21 is a sectional view schematically illustrating the structure of the semiconductor device according to the embodiment.

Fig. 22 is a sectional view schematically illustrating the structure of the semiconductor device according to the embodiment.

(symbol description)

1: an n-type gallium oxide substrate; 2. 2a, 2b, 2 c: an n-type gallium oxide epitaxial layer; 3: a cathode electrode; 4: an anode electrode; 5. 5a, 5 c: a p-type oxide semiconductor layer; 6: a dielectric layer for a field plate (field plate); 7. 7a, 7b, 7 c: a dielectric layer; 10: a groove part; 11: a source electrode; 12: a gate electrode; 13: and a drain electrode.

Detailed Description

Hereinafter, embodiments will be described with reference to the accompanying drawings.

The drawings are schematically illustrated, and the configuration is omitted or simplified as appropriate for the convenience of explanation. The mutual relationship between the size and the position of the structures and the like shown in the different drawings is not necessarily described correctly, and may be appropriately changed.

In the following description, the same components are denoted by the same reference numerals, and the same names and functions are assumed. Therefore, detailed descriptions thereof may be omitted to avoid redundancy.

In the following description, terms such as "upper", "lower", "left", "right", "side", "bottom", "table", and "back" may be used to indicate specific positions and directions, but these terms are used for ease of understanding the contents of the embodiments and are used for convenience of description, and are not related to the directions in actual implementation.

In the following description, ordinal numbers such as "1 st" and "2 nd" may be used, but these terms are used for ease of understanding the contents of the embodiments and are not limited to the order in which the ordinal numbers can be generated.

< embodiment 1 >

The following describes an oxide semiconductor device and a method for manufacturing the oxide semiconductor device according to this embodiment.

< Structure of oxide semiconductor device >

First, the structure of the semiconductor device according to this embodiment will be described.

Fig. 1 is a plan view schematically illustrating a structure for realizing a semiconductor device according to this embodiment. Fig. 2 is a cross-sectional view schematically illustrating the structure of the semiconductor device in section I-I' of fig. 1.

As illustrated in fig. 1 and 2, the semiconductor device according to the present embodiment is provided with a Schottky Barrier Diode (SBD) and a MPS of a pn junction diode (PND) at the same time.

In this embodiment, a schottky barrier diode in which the 1 st electrode is an anode electrode and the 2 nd electrode is a cathode electrode is described as a semiconductor device, but the semiconductor device is not limited to the schottky barrier diode and may be a semiconductor device constituting another switching element.

As illustrated in fig. 2, an n-type gallium oxide substrate 1, which is a single crystal of an n-type oxide semiconductor, has a 1 st principal surface (i.e., an upper surface) and a 2 nd principal surface (i.e., a lower surface) provided on the back side of the 1 st principal surface. The semiconductor device includes an n-type gallium oxide epitaxial layer 2 on a 1 st main surface of an n-type gallium oxide substrate 1. The semiconductor device includes a cathode electrode 3 that is ohmically bonded to the n-type gallium oxide substrate 1 on the 2 nd principal surface of the n-type gallium oxide substrate 1, and an anode electrode 4 that is schottky-bonded to the n-type gallium oxide epitaxial layer 2 on the upper surface of the n-type gallium oxide epitaxial layer 2.

The semiconductor device further includes a plurality of p-type oxide semiconductor layers 5, and the plurality of p-type oxide semiconductor layers 5 are formed from the upper surface of the n-type gallium oxide epitaxial layer 2 to the lower surface of the n-type gallium oxide epitaxial layer 2. The p-type oxide semiconductor layer 5 and the anode electrode 4 form an ohmic junction.

The semiconductor device further includes a field plate dielectric layer 6 between the n-type gallium oxide epitaxial layer 2 and the anode electrode 4. The part formed by laminating the field plate dielectric layer 6 and the anode electrode 4 constitutes a field plate structure, and the withstand voltage of the semiconductor device when a reverse voltage is applied is improved.

The semiconductor device further includes a dielectric layer 7, and the dielectric layer 7 is formed on the entire surface of the contact surface between the n-type gallium oxide epitaxial layer 2 and the p-type oxide semiconductor layer 5. By providing the dielectric layer 7, diffusion of atoms is prevented between the n-type gallium oxide epitaxial layer 2 and the p-type oxide semiconductor layer 5. As a result, the influence of diffusion of atoms into the schottky interface formed between n-type gallium oxide epitaxial layer 2 and anode electrode 4 can be suppressed, and a normal schottky interface can be maintained.

The n-type gallium oxide substrate 1 is made of Ga₂O₃More preferably β -Ga, in the presence of a single crystal of (A)₂O₃An n-type oxide semiconductor composed of the single crystal of (3). The n-type gallium oxide substrate 1 may not contain an n-type impurity because it exhibits n-type conductivity due to lack of oxygen in the crystal, but may contain an n-type impurity such as silicon (Si) or tin (Sn).

That is, the n-type gallium oxide substrate 1 may be any of a substrate exhibiting n-type conductivity due to oxygen deficiency only, a substrate exhibiting n-type conductivity due to n-type impurities only, and a substrate exhibiting n-type conductivity due to both oxygen deficiency and n-type impurities.

The n-type carrier concentration of the n-type gallium oxide substrate 1 is the total concentration of oxygen deficiency and n-type impurity, and may be, for example, 1 × 10¹⁷cm^-3Above and 1 × 10¹⁸cm^-3The following. In addition, the impurity concentration may be higher in order to reduce the contact resistance between the n-type gallium oxide substrate 1 and the anode electrode 4.

An n-type gallium oxide epitaxial layer 2 is formed on the upper surface of the n-type gallium oxide substrate 1. The n-type gallium oxide epitaxial layer 2 is formed of Ga₂O₃More preferably β -Ga, in the presence of a single crystal of (A)₂O₃An n-type oxide semiconductor composed of the single crystal of (3). The n-type carrier concentration of the n-type gallium oxide epitaxial layer 2 is preferably lower than that of the n-type gallium oxide substrate1 Low concentration, for example, 1X 10¹⁵cm^-3Above and 1 × 10¹⁷cm^-3The following.

The cathode electrode 3 is formed on the lower surface of the n-type gallium oxide substrate 1. The cathode electrode 3 is preferably made of a metal material having a work function smaller than that of the n-type gallium oxide substrate 1 so as to be ohmically bonded to the n-type gallium oxide substrate 1. It is preferable that the n-type gallium oxide substrate 1 is made of a metal material whose contact resistance between the n-type gallium oxide substrate 1 and the cathode electrode 3 is small by heat treatment after the cathode electrode 3 is formed on the 2 nd principal surface of the n-type gallium oxide substrate 1.

Such a metal material may be, for example, titanium (Ti). The cathode electrode 3 may be formed by laminating a plurality of metal materials, and for example, when the metal material in contact with the 2 nd main surface of the n-type gallium oxide substrate 1 is a metal material that is easily oxidized, the cathode electrode 3 having a laminated structure may be formed by forming a metal material that is not easily oxidized on the lower surface of the metal material. For example, Ti may be used as the 1 st layer in contact with the n-type gallium oxide substrate 1, and a 2 nd layer made of gold (Au) or silver (Ag) may be formed on the lower surface of Ti as the 1 st layer to form the cathode electrode 3. The cathode electrode 3 may be formed on the entire 2 nd main surface of the n-type gallium oxide substrate 1, or may be formed on a part of the 2 nd main surface of the n-type gallium oxide substrate 1.

The anode electrode 4 is formed on the upper surface of the n-type gallium oxide epitaxial layer 2. The anode electrode 4 is made of a metal material having a work function larger than that of the n-type gallium oxide epitaxial layer 2 so as to be schottky-bonded to the n-type gallium oxide epitaxial layer 2. Further, the anode electrode 4 is preferably made of a metal material having a work function smaller than that of the p-type oxide semiconductor material constituting the p-type oxide semiconductor layer 5 so as to be ohmically joined to the p-type oxide semiconductor layer 5.

Examples of such a metal material include platinum (Pt), nickel (Ni), gold (Au), and palladium (Pd). The anode electrode 4 may have a laminated structure as in the cathode electrode 3, and for example, a metal material suitable for schottky junction with the n-type gallium oxide epitaxial layer 2 may be formed as a 1 st layer in contact with the n-type gallium oxide epitaxial layer 2, and a metal material to be the 2 nd layer may be formed as the anode electrode 4 on the upper surface of the 1 st layer.

The p-type oxide semiconductor layer 5 is formed from the upper surface to the lower surface of the n-type gallium oxide epitaxial layer 2. The p-type oxide semiconductor layer 5 is directly bonded to the n-type gallium oxide substrate 1. A hetero pn junction is formed between the lower surface of the p-type oxide semiconductor layer 5 and the n-type gallium oxide substrate 1. The p-type oxide semiconductor layer 5 is made of copper oxide (Cu)₂O), silver oxide (Ag)₂O), nickel oxide (NiO), tin oxide (SnO), or the like, and exhibits p-type conductivity even without the addition of p-type impurities. For example, in Cu as the metal oxide₂In O, the 3d orbital of Cu forms the upper end of the valence band for shoulder hole conduction, and holes appear due to Cu deficiency, so that p-type conductivity is exhibited. And, Cu₂Since O is changed to CuO by oxidation, the 3d orbital of Cu does not form the upper end of the valence band. Therefore, the p-type conductivity disappears. The p-type oxide semiconductor layer 5 is formed of a p-type oxide semiconductor made of a metal oxide having such properties, and generally exhibits p-type conductivity even without addition of a p-type impurity.

In addition, the p-type oxide semiconductor layer 5 may be made of Cu₂O、Ag₂O, NiO or SnO containing indium oxide (In)₂O₃) Gallium oxide (Ga)₂O₃) Or a p-type oxide semiconductor of zinc oxide (ZoN). The p-type oxide semiconductor layer 5 is formed of a p-type oxide semiconductor which exhibits p-type conductivity without adding a p-type impurity as described above, but a p-type impurity may be added.

For example, in Cu₂In O, nitrogen (N) can be used as a p-type impurity. When a p-type impurity is added, the total of the absence of metal atoms in the p-type oxide semiconductor and the p-type impurity becomes the p-type carrier concentration. Therefore, the p-type oxide semiconductor layer 5 contains a p-type impurity, and even if the metal oxide of the p-type oxide semiconductor is oxidized to lose the p-type conductivity, the p-type oxide semiconductor may exhibit the p-type conductivity as a wholeSince the p-type conductivity of the entire oxide semiconductor is reduced, it is important not to oxidize the metal oxide of the p-type oxide semiconductor.

The field plate dielectric layer 6 is made of, for example, silicon dioxide (SiO)₂) Or aluminum oxide (Al)₂O₃) Etc. of Ga having a dielectric breakdown field strength ratio of Ga constituting the n-type gallium oxide epitaxial layer 2₂O₃Large materials. The thickness of the field plate dielectric layer 6 may be about several hundred nm, and may be, for example, 100nm or more and 200nm or less.

The dielectric layer 7 is made of, for example, silicon dioxide (SiO)₂) Silicon nitride (SiN), gallium nitride (GaN) or aluminum oxide (Al)₂O₃) And the like. The dielectric layer 7 is formed so as to cover the entire side surface of the p-type oxide semiconductor layer 5, that is, the entire surface along the current direction which is the direction connecting the anode electrode 4 and the cathode electrode 3. The dielectric constant of the material constituting the dielectric layer 7 is smaller than the dielectric constant of the material constituting the p-type oxide semiconductor layer 5. The dielectric layer 7 is provided to prevent diffusion of metal atoms from the p-type oxide semiconductor layer 5 to the schottky interface. Therefore, the dielectric layer 7 is not limited to the insulating layer as long as it can prevent diffusion of metal atoms from the p-type oxide semiconductor layer 5 to the schottky interface.

In addition, the thickness of the dielectric layer 7 is preferably 3nm or more, and may be 3nm or more and 300nm or less, for example, particularly when the metal oxide included in the p-type oxide semiconductor layer 5 and the metal oxide forming the mixed crystal material are included.

< method for manufacturing oxide semiconductor device >

Next, a method for manufacturing a semiconductor device according to this embodiment will be described.

First, cathode electrode 3 is formed on the 2 nd principal surface of n-type gallium oxide substrate 1.β -Ga prepared by melt growth (melt growth method) can be used as n-type gallium oxide substrate 1₂O₃The single crystal ingot of (2) is cut into a substrate in the form of a substrate.

Next, an n-type gallium oxide epitaxial layer 2 is deposited by epitaxial growth on the 1 st principal surface of the n-type gallium oxide substrate 1. The n-type gallium oxide epitaxial layer 2 can be formed on the 1 st principal surface of the n-type gallium oxide substrate 1 by a method such as a Metal Organic Chemical Vapor Deposition (MOCVD) method, a Molecular Beam Epitaxy (MBE) method, or a Halide Vapor Phase Epitaxy (HVPE) method.

Next, a metal material to be the cathode electrode 3 is deposited on the 2 nd main surface of the n-type gallium oxide substrate 1 by a vapor deposition method or a sputtering method. For example, Ti is deposited on the 2 nd main surface of the n-type gallium oxide substrate 1 by electron beam evaporation (EB evaporation) to a thickness of 100nm, and then Ag is deposited on the Ti by electron beam evaporation to a thickness of 300nm, thereby forming the cathode electrode 3 having a 2-layer structure.

Thereafter, a heat treatment is performed at 550 ℃ for 5 minutes, for example, in a nitrogen atmosphere or an oxygen atmosphere. As a result, cathode electrode 3 ohmically bonded to n-type gallium oxide substrate 1 is formed on the 2 nd principal surface of n-type gallium oxide substrate 1.

As a method for reducing the contact resistance between the n-type gallium oxide substrate 1 and the cathode electrode 3, there is a method of: boron trichloride (BCl) was applied to the 2 nd main surface of the n-type gallium oxide substrate 1 before the cathode electrode 3 was formed₃) Etc. of the RIE process of the gas.

Here, as a method for forming the p-type oxide semiconductor layer 5 and the dielectric layer 7, there are 2 methods. The 1 st method is as follows: a groove portion is formed in the n-type gallium oxide epitaxial layer 2, and the p-type oxide semiconductor layer 5 and the dielectric layer 7 are embedded in the groove portion. The 2 nd method is as follows: after the p-type oxide semiconductor layer 5 and the dielectric layer 7 are formed on the 1 st principal surface of the n-type gallium oxide substrate 1, the n-type gallium oxide epitaxial layer 2 is formed so as to embed them.

For example, in the 2 nd method, in the reaction of Cu₂In the case where O forms the p-type oxide semiconductor layer 5, argon (Ar) gas and nitrogen (N)₂) In the mixed gas of gases, by mixing Cu₂O is used for sputtering of a target (target), and Cu is deposited on the 1 st principal surface of the n-type gallium oxide substrate 1₂O, thereby enabling p to be formedAnd a type oxide semiconductor layer 5.

By increasing the N of the gas mixture₂The carrier concentration of the p-type oxide semiconductor layer 5 can be increased to increase the p-type conductivity. In addition, by reducing the N of the mixed gas₂The carrier concentration of the p-type oxide semiconductor layer 5 can be reduced to reduce the p-type conductivity.

In addition, in the 1 st method, as a method of forming a groove portion in the n-type gallium oxide epitaxial layer 2, it is effective to use BCl₃And the like.

The method for forming the dielectric layer 7 is not particularly limited, and an existing method such as a sputtering method or a CVD method can be used. The thickness of the dielectric layer 7 in the horizontal direction of the device is preferably a thickness that can prevent diffusion of metal atoms from the p-type oxide semiconductor layer 5 and that does not suppress the expansion of the depletion layer as much as possible.

< embodiment 2 >

An oxide semiconductor device and a method for manufacturing the oxide semiconductor device according to this embodiment will be described. In the following description, the same components as those described in the above-described embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted as appropriate.

< Structure of oxide semiconductor device >

Fig. 3 is a sectional view schematically illustrating the structure of the semiconductor device according to this embodiment. In the semiconductor device illustrated in fig. 3, the length of the dielectric layer 7a extending parallel to the current direction, i.e., the vertical direction in fig. 3, is different from that in the embodiment illustrated in embodiment 1.

As illustrated in fig. 3, the length of the dielectric layer 7a in the current flow direction is shorter than the length of the adjacent p-type oxide semiconductor layer 5 in the current flow direction. That is, the lower surface of the dielectric layer 7a is located shallower than the lower surface of the p-type oxide semiconductor layer 5. As compared with the structure exemplified in embodiment 1, the following structure is obtained: a portion where the n-type gallium oxide epitaxial layer 2 and the p-type oxide semiconductor layer 5 are directly bonded exists in the vicinity of the n-type gallium oxide substrate 1, and a depletion layer is likely to spread in a direction perpendicular to the current direction of the device. Therefore, the withstand voltage of the semiconductor device when a reverse voltage is applied is improved.

< embodiment 3 >

< Structure of oxide semiconductor device >

Fig. 4 is a sectional view schematically illustrating the structure of the semiconductor device according to this embodiment. In the semiconductor device illustrated in fig. 4, the length of the p-type oxide semiconductor layer 5a and the length of the dielectric layer 7a extending in parallel to the vertical direction in fig. 4, which is the current direction, are different from those in the embodiment illustrated in fig. 1. Specifically, the p-type oxide semiconductor layer 5a is formed from the upper surface to the inside of the n-type gallium oxide epitaxial layer 2. The dielectric layer 7a is formed to cover the entire side surface of the p-type oxide semiconductor layer 5 a. Here, the lengths of the p-type oxide semiconductor layer 5a and the dielectric layer 7a in the direction parallel to the current direction of the device are the same.

As illustrated in fig. 4, the length of the dielectric layer 7a in the current flow direction is equal to the length of the adjacent p-type oxide semiconductor layer 5a in the current flow direction, but is different from the structure illustrated in embodiment 1 in that the dielectric layer 7a and the p-type oxide semiconductor layer 5a are not in direct contact with the n-type gallium oxide substrate 1. The p-type oxide semiconductor layer 5a is directly bonded to the n-type gallium oxide epitaxial layer 2. Further, a hetero pn junction is formed between the lower surface of the p-type oxide semiconductor layer 5a and the n-type gallium oxide epitaxial layer 2. The depletion layer is easily expanded by direct contact between the lower surface of the p-type oxide semiconductor layer 5a, which is a surface perpendicular to the direction of current flow of the device in the p-type oxide semiconductor layer 5a, and the n-type gallium oxide epitaxial layer 2. Therefore, the withstand voltage of the semiconductor device when a reverse voltage is applied is improved.

< method for manufacturing oxide semiconductor device >

Next, a method for manufacturing a semiconductor device according to the present embodiment will be described with reference to fig. 5 to 20. Fig. 5 to 20 are sectional views illustrating a manufacturing process of the semiconductor device according to the present embodiment.

As described above, there are 2 methods as methods for forming the p-type oxide semiconductor layer 5a and the dielectric layer 7a, and therefore, the respective methods will be described.

First, as for the method 1, an n-type gallium oxide substrate 1 is prepared as illustrated in fig. 5. Then, as illustrated in fig. 6, a metal material to be the cathode electrode 3 is deposited on the 2 nd main surface of the n-type gallium oxide substrate 1 by a vapor deposition method or a sputtering method.

Next, as illustrated in fig. 7, an n-type gallium oxide epitaxial layer 2 is deposited by epitaxial growth on the 1 st principal surface of the n-type gallium oxide substrate 1.

Next, as illustrated in fig. 8, a groove 10 is formed in the surface layer of the n-type gallium oxide epitaxial layer 2. The groove portion 10 is a depth not reaching the n-type gallium oxide substrate 1, but may reach the n-type gallium oxide substrate 1. As a method for forming the groove portion 10, it is effective to use BCl₃And the like.

Next, as illustrated in fig. 9, dielectric layer 7a is formed on n-type gallium oxide epitaxial layer 2 except for the bottom surface of groove 10. The dielectric layer 7a is formed by, for example, stripping by photolithography. Specifically, a resist having an opening is formed on the side surface of the groove portion 10, and the material of the dielectric layer 7a is formed and then peeled off. In the case of forming a structure in which the lower surface of the dielectric layer 7a is located shallower than the lower surface of the p-type oxide semiconductor layer 5 as illustrated in fig. 3 and 21, a resist covering a portion of the side surface of the groove 10 close to the bottom surface of the groove 10 may be formed, and the material of the dielectric layer 7a may be removed after film formation. Next, as illustrated in fig. 10, the p-type oxide semiconductor layer 5a is formed in the groove portion 10.

Next, as illustrated in fig. 11, a field plate dielectric layer 6 is partially formed on the upper surface of the n-type gallium oxide epitaxial layer 2 including the groove portion 10 in which the p-type oxide semiconductor layer 5a is embedded.

Next, as illustrated in fig. 12, the anode electrode 4 is formed across a part of the field plate dielectric layer 6 and the upper surface of the n-type gallium oxide epitaxial layer 2 not covered with the field plate dielectric layer 6.

According to the above manufacturing method, the p-type oxide semiconductor layer 5a can be formed without being affected by the temperature required for forming the n-type gallium oxide epitaxial layer 2, and therefore the p-type oxide semiconductor layer 5a can be formed at a relatively low temperature, for example, 200 ℃. Therefore, crystallization of the p-type oxide semiconductor layer 5a is suppressed, and the withstand voltage and the leakage current can be improved when a reverse voltage is applied to the device.

In the above-described manufacturing method, the n-type gallium oxide epitaxial layer 2 illustrated in fig. 7 may be formed before the cathode electrode 3 illustrated in fig. 6 is formed.

Next, the 2 nd method is explained. First, as illustrated in fig. 13, an n-type gallium oxide substrate 1 is prepared. Then, as illustrated in fig. 14, a metal material to be the cathode electrode 3 is deposited on the 2 nd main surface of the n-type gallium oxide substrate 1 by a vapor deposition method or a sputtering method.

Next, as illustrated in fig. 15, an n-type gallium oxide epitaxial layer 2a is deposited on the 1 st principal surface of the n-type gallium oxide substrate 1 in a relatively thin thickness by epitaxial growth.

Next, as illustrated in fig. 16, a p-type oxide semiconductor layer 5a is partially deposited on the upper surface of the n-type gallium oxide epitaxial layer 2a by sputtering.

Next, as illustrated in fig. 17, a dielectric layer 7a is formed on the side surface of the p-type oxide semiconductor layer 5 a. The dielectric layer 7a is formed by, for example, stripping by photolithography. Specifically, a resist having an opening is formed on the side surface of the p-type oxide semiconductor layer 5a, and the material of the dielectric layer 7a is formed and then peeled off. In the case of forming a structure in which the lower surface of the dielectric layer 7a is located shallower than the lower surface of the p-type oxide semiconductor layer 5 as illustrated in fig. 3 and 21, a resist covering a portion of the side surface of the p-type oxide semiconductor layer 5a close to the upper surface of the n-type gallium oxide epitaxial layer 2a may be formed, and the material of the dielectric layer 7a may be removed after the film formation. Next, as illustrated in fig. 18, the region where the p-type oxide semiconductor layer 5a is not formed is epitaxially grown again to form an n-type gallium oxide epitaxial layer 2 b. Here, the n-type gallium oxide epitaxial layer 2 is formed by adding the n-type gallium oxide epitaxial layer 2a and the n-type gallium oxide epitaxial layer 2 b.

Next, as illustrated in fig. 19, a field plate dielectric layer 6 is partially formed on the upper surface of the p-type oxide semiconductor layer 5a and the upper surface of the n-type gallium oxide epitaxial layer 2.

Next, as illustrated in fig. 20, the anode electrode 4 is formed across a part of the field plate dielectric layer 6 and the upper surface of the n-type gallium oxide epitaxial layer 2 not covered with the field plate dielectric layer 6.

By the above manufacturing method, a semiconductor device having a structure similar to that shown in fig. 12 can be obtained.

In addition, in the method for manufacturing the semiconductor device illustrated in fig. 5 to 20, for example, photolithography may be used.

< embodiment 4 >

< Structure of oxide semiconductor device >

Fig. 21 is a sectional view schematically illustrating the structure of the semiconductor device according to this embodiment. In the semiconductor device illustrated in fig. 21, the length of the dielectric layer 7b extending parallel to the current direction, i.e., the vertical direction in fig. 21, is different from that in the embodiment illustrated in embodiment 3.

As illustrated in fig. 21, the length of the dielectric layer 7b in the current flow direction is shorter than the length of the adjacent p-type oxide semiconductor layer 5a in the current flow direction. When compared with the structure exemplified in embodiment 3, the structure is as follows: the portion where the n-type gallium oxide epitaxial layer 2 and the p-type oxide semiconductor layer 5a are directly joined exists in the p-type oxide semiconductor layer 5a at a position close to the n-type gallium oxide substrate 1, and the depletion layer is likely to spread in a direction perpendicular to the current direction of the device. Therefore, the withstand voltage of the semiconductor device when a reverse voltage is applied is improved.

< operation of oxide semiconductor device >

Next, the operation of the semiconductor device according to this embodiment will be described.

A voltage is applied between the anode electrode 4 and the cathode electrode 3 of the semiconductor device from a circuit provided outside the semiconductor device. The case where a voltage higher than the potential of the cathode electrode 3 is applied to the anode electrode 4 is referred to as a positive bias, and the case where a voltage lower than the potential of the cathode electrode 3 is applied to the anode electrode 4 is referred to as a reverse bias.

In the semiconductor device according to the present embodiment, when a forward bias is applied, a forward current flows from the anode electrode 4 to the cathode electrode 3, and when a reverse bias is applied, a current flowing between the anode electrode 4 and the cathode electrode 3 is interrupted.

Since the p-type oxide semiconductor layer 5a is ohmically bonded to the anode electrode 4 and the n-type gallium oxide epitaxial layer 2 is ohmically bonded to the cathode electrode 3 via the n-type gallium oxide substrate 1, the potential of the p-type oxide semiconductor layer 5a is lower than the potential of the n-type gallium oxide epitaxial layer 2 when a reverse bias is applied to the semiconductor device.

As a result, the depletion layer that has spread toward n-type gallium oxide epitaxial layer 2 becomes thicker, and becomes pinch-off. The depletion layer covers the entire schottky junction between the n-type gallium oxide epitaxial layer 2 and the anode electrode 4.

Since the depletion layer is an insulator, most of the reverse bias voltage applied between the anode electrode 4 and the cathode electrode 3 is applied to the depletion layer, and the voltage applied to the schottky junction between the n-type gallium oxide epitaxial layer 2 and the anode electrode 4 is significantly lower than that in the case where there is no depletion layer. As a result, the withstand voltage of the semiconductor device when a reverse voltage is applied can be increased.

Regarding the gallium oxide semiconductor, it is possible to easily control the n-type carrier concentration by adding an n-type impurity such as Si or Sn, but on the other hand, it is extremely difficult to control the p-type carrier concentration by adding a p-type impurity, and there has been no report that clear hole conduction is observed by adding a p-type impurity.

Therefore, it is difficult to form a p-type semiconductor by adding a p-type impurity into the n-type gallium oxide epitaxial layer 2 as in a semiconductor device formed of Si or SiC to improve the withstand voltage of the schottky junction when a reverse voltage is applied.

The semiconductor device according to this embodiment mode has the following structure: by forming the p-type oxide semiconductor layer 5a of a material different from gallium oxide inside the n-type gallium oxide epitaxial layer 2, a depletion layer is formed within the n-type gallium oxide epitaxial layer 2 by means of a hetero pn junction.

In the semiconductor device according to the present embodiment, since the dielectric layer 7b is provided on a part of the surface parallel to the current direction of the device between the n-type gallium oxide epitaxial layer 2 and the p-type oxide semiconductor layer 5a, the influence of the metal atoms diffused from the p-type oxide semiconductor layer 5a on the schottky interface can be suppressed.

< embodiment 5 >

< Structure of oxide semiconductor device >

Fig. 22 is a sectional view schematically illustrating the structure of the semiconductor device according to this embodiment. The semiconductor device illustrated in fig. 22 is a field effect transistor in which the vertical direction in fig. 22 is the current direction.

As shown in fig. 22, an n-type gallium oxide epitaxial layer 2c is formed on the upper surface of the n-type gallium oxide substrate 1. Then, a p-type oxide semiconductor layer 5c is formed on the surface layer of the n-type gallium oxide epitaxial layer 2 c.

Further, a gate electrode 12 is formed on the surface layer of the p-type oxide semiconductor layer 5 c. Then, the dielectric layer 7c is formed so as to sandwich the gate electrode 12 in a plan view. In addition, the dielectric layer 7c is formed in contact with a part of the lower surface of the gate electrode 12 in addition to the side surface of the gate electrode 12. Then, the dielectric layer 7c and the p-type oxide semiconductor layer 5c are directly bonded.

Further, a source electrode 11 is formed on the upper surface of the n-type gallium oxide epitaxial layer 2 c. Then, the source electrode 11 is directly bonded to the n-type gallium oxide epitaxial layer 2 c. Further, a drain electrode 13 is formed on the lower surface of the n-type gallium oxide substrate 1.

The p-type oxide semiconductor layer 5c is directly bonded to the source electrode 11 at a certain position in the depth direction in fig. 22. In this case, the p-type oxide semiconductor layer 5c is formed to extend directly below the source electrode 11, or the source electrode 11 is formed to extend directly above the p-type oxide semiconductor layer 5 c.

Fig. 22 shows a case where the source electrode 11 in contact with the p-type oxide semiconductor layer 5c is extracted. A dielectric layer 7c is inserted into the interface between the upper portion of the p-type oxide semiconductor layer 5c and the n-type gallium oxide epitaxial layer 2 c. Therefore, in the present structure, similarly to the structure shown in the above embodiment, by forming the dielectric layer 7c on the side surface of the p-type oxide semiconductor layer 5c, diffusion of atoms between the p-type oxide semiconductor layer and the n-type gallium oxide epitaxial layer 2c can be suppressed. Therefore, threshold shift at the interface between the electrode and the semiconductor layer is suppressed.

The present structure is a field effect transistor that controls the amount of current flowing between the source electrode 11 and the drain electrode 13 by applying a voltage to the gate electrode 12.

The semiconductor device according to this embodiment mode has the following structure: by forming the p-type oxide semiconductor layer 5c of a material different from gallium oxide inside the n-type gallium oxide epitaxial layer 2c, a depletion layer is formed within the n-type gallium oxide epitaxial layer 2c by a hetero pn junction.

That is, when a reverse voltage is applied to the source electrode 11 and the drain electrode 13, the p-type oxide semiconductor layer 5c disposed directly below the gate electrode 12 has an electric field relaxing effect and has an effect of improving the withstand voltage.

In the semiconductor device according to the present embodiment, since the dielectric layer 7c is provided in a part of the surface parallel to the current direction of the device between the n-type gallium oxide epitaxial layer 2c and the p-type oxide semiconductor layer 5c, the metal atoms diffused from the p-type oxide semiconductor layer 5c can suppress the threshold shift in the interface between the source electrode 11 and the n-type gallium oxide epitaxial layer 2 c.

According to such a structure, in an oxide semiconductor device in which a heterogeneous pn junction is formed of a different oxide semiconductor material, diffusion of the different material to the interface between the electrode and the semiconductor can be suppressed, and the withstand voltage when a reverse voltage is applied can be improved.

< effects produced by the above-described embodiments >

Next, the effects produced by the above-described embodiments will be exemplified. In the following description, the effects are described based on the specific configurations exemplified in the above-described embodiments, but may be replaced with other specific configurations exemplified in the present specification within the range where the similar effects are produced.

In addition, the permutation may be performed across a plurality of embodiments. That is, the same effects may be produced by combining the respective configurations illustrated in the different embodiments.

According to the above-described embodiment, the oxide semiconductor device includes the n-type gallium oxide epitaxial layer, the p-type oxide semiconductor layer, the dielectric layer 7, the anode electrode 4, and the cathode electrode 3. Here, the gallium oxide epitaxial layer corresponds to, for example, the n-type gallium oxide epitaxial layer 2. The oxide semiconductor layer corresponds to, for example, at least 1 of the p-type oxide semiconductor layer 5 and the p-type oxide semiconductor layer 5 a. An n-type gallium oxide epitaxial layer 2 is formed on the upper surface of the n-type gallium oxide substrate 1. The oxide semiconductor layer is formed at least from the upper surface to the inside of the n-type gallium oxide epitaxial layer 2. In addition, the oxide semiconductor layer is an oxide of a material different from that of the n-type gallium oxide epitaxial layer 2. The dielectric layer 7 is formed to cover at least a part of the side surface of the oxide semiconductor layer. The dielectric layer 7 is made of a material having a dielectric constant smaller than that of the material constituting the oxide semiconductor layer. The anode electrode 4 is formed on the upper surface of the n-type gallium oxide epitaxial layer 2. In addition, the anode electrode 4 forms a schottky junction with the n-type gallium oxide epitaxial layer 2. The cathode electrode 3 is formed on the lower surface of the n-type gallium oxide substrate 1. Further, the cathode electrode 3 is ohmic-bonded to the n-type gallium oxide substrate 1. A hetero pn junction is formed between the lower surface of the p-type oxide semiconductor layer 5 and the n-type gallium oxide substrate 1, or between the lower surface of the p-type oxide semiconductor layer 5a and the n-type gallium oxide epitaxial layer 2.

With such a configuration, in an oxide semiconductor device in which a heterogeneous pn junction is formed of a different oxide semiconductor material, diffusion of the different material to a schottky interface is suppressed, and a withstand voltage when a reverse voltage is applied can be improved. Specifically, by forming the dielectric layer 7 on the side surface of the p-type oxide semiconductor layer, diffusion of atoms between the p-type oxide semiconductor layer and the n-type gallium oxide epitaxial layer 2 can be suppressed.

In addition, other structures than these structures exemplified in the present specification may be appropriately omitted. That is, the above-described effects can be produced by providing at least these structures.

However, the above-described effects can be similarly produced even when at least 1 of the other configurations exemplified in the present specification is appropriately added to the above-described configurations, that is, when the other configurations exemplified in the present specification that are not described as the above-described configurations are added to the above-described configurations.

In addition, according to the above-described embodiment, the side surface of the p-type oxide semiconductor layer 5 is a surface along the current direction which is the direction connecting the anode electrode 4 and the cathode electrode 3, that is, for example, the vertical direction in fig. 2. With such a configuration, the dielectric layer 7 formed on the side surface of the p-type oxide semiconductor layer 5 can suppress diffusion of atoms to the schottky interface without suppressing expansion of the depletion layer.

In addition, according to the above-described embodiment, the lower surface of the dielectric layer 7a is located shallower than the lower surface of the p-type oxide semiconductor layer 5. According to such a configuration, since the p-type oxide semiconductor layer 5 is formed to extend in a direction closer to the cathode electrode 3 than the dielectric layer 7a, it is possible to provide a semiconductor device which suppresses diffusion of atoms to the schottky interface, has a low reverse leakage current, and has a high withstand voltage when a reverse voltage is applied.

In addition, according to the above-described embodiment, the dielectric layer 7 is formed so as to cover the entire side surface of the p-type oxide semiconductor layer 5. With such a structure, diffusion of atoms to the schottky interface can be suppressed.

In addition, according to the above-described embodiment, the p-type oxide semiconductor layer 5a is formed from the upper surface to the inside of the n-type gallium oxide epitaxial layer 2. A hetero pn junction is formed between the lower surface of the p-type oxide semiconductor layer 5a and the n-type gallium oxide epitaxial layer 2. According to such a configuration, the lower surface of the p-type oxide semiconductor layer 5a is directly bonded to the n-type gallium oxide epitaxial layer 2, and the entire side surface of the p-type oxide semiconductor layer 5a is covered with the dielectric layer 7a, whereby the withstand voltage when a reverse voltage is applied can be improved and the leakage current can be reduced.

In addition, according to the above-described embodiment, the p-type oxide semiconductor layer 5 is formed from the upper surface to the lower surface of the n-type gallium oxide epitaxial layer 2. A hetero pn junction is formed between the lower surface of the p-type oxide semiconductor layer 5 and the n-type gallium oxide substrate 1. According to such a configuration, the lower surface of the p-type oxide semiconductor layer 5 is directly bonded to the n-type gallium oxide substrate 1, and the entire side surface of the p-type oxide semiconductor layer 5 is covered with the dielectric layer 7, so that the withstand voltage when a reverse voltage is applied can be improved, and the leakage current can be reduced.

In addition, according to the above-described embodiment, the impurity concentration of the n-type gallium oxide epitaxial layer 2 is lower than the impurity concentration of the n-type gallium oxide substrate 1. According to such a configuration, the concentration of the drift layer is reduced, and the leakage current can be reduced while the withstand voltage when a reverse voltage is applied is increased.

In addition, according to the above-described embodiment, the p-type oxide semiconductor layer 5 is a metal oxide containing Cu or Ni. According to such a structure, Cu is added₂O or NiO is used for the p-type oxide semiconductor layer 5, and can improve withstand voltage when a reverse voltage is applied and reduce leakage current.

According to the above-described embodiments, in the method for manufacturing an oxide semiconductor device, the cathode electrode 3 that is ohmically bonded to the n-type gallium oxide substrate 1 is formed on the lower surface of the n-type gallium oxide substrate 1. Then, an n-type gallium oxide epitaxial layer 2 is epitaxially grown on the upper surface of the n-type gallium oxide substrate 1. Then, a trench 10 is formed to reach at least the inside from the upper surface of the n-type gallium oxide epitaxial layer 2. Then, dielectric layer 7 is formed on at least a part of the side surface of groove 10. Then, in the groove portion 10 with the dielectric layer 7 formed on the side surface, a p-type oxide semiconductor layer made of a material having a higher dielectric constant than the dielectric layer 7 and made of an oxide of a material different from the material of the n-type gallium oxide epitaxial layer 2 is formed. Then, an anode electrode 4 schottky-bonded to the n-type gallium oxide epitaxial layer 2 is formed on the upper surface of the n-type gallium oxide epitaxial layer 2. Here, a hetero pn junction is formed between the lower surface of the p-type oxide semiconductor layer 5 and the n-type gallium oxide substrate 1, or between the lower surface of the p-type oxide semiconductor layer 5a and the n-type gallium oxide epitaxial layer 2.

According to such a structure, when an oxide semiconductor device in which a hetero pn junction is formed of a different oxide semiconductor material is manufactured, a p-type semiconductor layer can be formed without performing p-type carrier concentration control by adding a p-type impurity. Specifically, the above structure can be realized by forming a groove portion in the n-type gallium oxide epitaxial layer 2 and forming the dielectric layer 7 and the p-type oxide semiconductor layer in the groove portion.

In addition, the order of executing the respective processes can be changed without particular limitation.

In addition, according to the above-described embodiment, the p-type oxide semiconductor layer 5a is formed at a formation temperature of 200 ℃. With such a structure, by forming the p-type oxide semiconductor layer 5a at a formation temperature of 200 ℃ or lower, crystallization of the p-type oxide semiconductor layer 5a can be suppressed. Therefore, the leakage current can be reduced while the withstand voltage of the device when a reverse voltage is applied is increased.

In addition, according to the above-described embodiment, the groove portion 10 is formed to extend from the upper surface of the n-type gallium oxide epitaxial layer 2 to the inside. Then, a hetero pn junction is formed between the lower surface of the p-type oxide semiconductor layer 5a and the n-type gallium oxide epitaxial layer 2. With this structure, the lower surface of the p-type oxide semiconductor layer 5a is directly bonded to the n-type gallium oxide epitaxial layer 2, and thus the breakdown voltage when a reverse voltage is applied can be increased and the leakage current can be reduced.

In addition, according to the above-described embodiment, the groove portion 10 is formed from the upper surface to the lower surface of the n-type gallium oxide epitaxial layer 2. Then, a hetero pn junction is formed between the lower surface of the p-type oxide semiconductor layer 5 and the n-type gallium oxide substrate 1. According to such a structure, the lower surface of the p-type oxide semiconductor layer 5 is directly bonded to the n-type gallium oxide substrate 1, and thus the withstand voltage when a reverse voltage is applied can be improved and the leakage current can be reduced.

In addition, according to the above-described embodiment, the cathode electrode 3 that is ohmically bonded to the n-type gallium oxide substrate 1 is formed on the lower surface of the n-type gallium oxide substrate 1. Then, an n-type 1 st gallium oxide epitaxial layer is epitaxially grown on the upper surface of the n-type gallium oxide substrate 1. Here, the 1 st gallium oxide epitaxial layer corresponds to, for example, the n-type gallium oxide epitaxial layer 2 a. Then, on the upper surface of the n-type gallium oxide epitaxial layer 2a, a p-type oxide semiconductor layer 5a is partially formed, the p-type oxide semiconductor layer 5a being an oxide of a material different from that of the n-type gallium oxide epitaxial layer 2 a. Then, a dielectric layer 7 made of a material having a dielectric constant smaller than that of the material constituting the p-type oxide semiconductor layer 5a is formed on at least a part of the side surface of the p-type oxide semiconductor layer 5 a. Then, an n-type 2 nd gallium oxide epitaxial layer is epitaxially grown so as to cover the n-type gallium oxide epitaxial layer 2a, the p-type oxide semiconductor layer 5a, and the dielectric layer 7. Here, the 2 nd gallium oxide epitaxial layer corresponds to, for example, the n-type gallium oxide epitaxial layer 2 b. Then, an anode electrode 4 schottky-bonded to the n-type gallium oxide epitaxial layer 2b is formed on the upper surface of the n-type gallium oxide epitaxial layer 2 b. Here, a hetero pn junction is formed between the lower surface of the p-type oxide semiconductor layer 5a and the upper surface of the n-type gallium oxide epitaxial layer 2 a.

According to such a structure, when an oxide semiconductor device in which a hetero pn junction is formed of a different oxide semiconductor material is manufactured, a p-type semiconductor layer can be formed without performing p-type carrier concentration control by adding a p-type impurity. Specifically, the above structure can be realized by forming a p-type oxide semiconductor layer and a dielectric layer 7 partially on the upper surface of the n-type gallium oxide epitaxial layer 2a, and epitaxially growing the n-type gallium oxide epitaxial layer again so as to fill the gap between the oxide semiconductor layers.

In addition, the order of executing the respective processes can be changed without particular limitation.

< modification of the above-described embodiment >

In the above-described embodiments, materials, dimensions, shapes, relative arrangement, conditions for implementation, and the like of the respective constituent elements are described in some cases, but these are merely examples in all respects and are not limited to the examples described in the present specification.

Therefore, a myriad of modifications and equivalents not illustrated are assumed to be within the scope of the technology disclosed in the present specification. For example, the case where at least 1 component is modified, added, or omitted, and the case where at least 1 component in at least 1 embodiment is extracted and combined with the components of other embodiments are included.

In addition, the constituent elements described as being provided with "1" in the above-described embodiments may be provided with "1 or more" as long as no contradiction occurs.

Each of the components in the above-described embodiments is a conceptual unit, and includes a case where 1 component is configured by a plurality of structural members, a case where 1 component corresponds to a part of a certain structural member, and a case where a plurality of components are provided in 1 structural member within the scope of the technology disclosed in the present specification.

In addition, each component in the above-described embodiments may include a structural object having another structure or shape as long as the same function is exerted.

In addition, the description in the specification of the present application is referred to for all purposes related to the present technology, and should not be construed as a prior art.

In the above-described embodiments, when a material name or the like is described without being particularly specified, an alloy or the like containing another additive in the material is included as long as no contradiction occurs.

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