JP2016174070A - Schottky barrier diode and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a Schottky barrier diode which is small in leak current when a backward voltage is applied thereto, and high in opposite direction withstand voltage; and a method for manufacturing such a Schottky barrier diode.SOLUTION: A Schottky barrier diode 1 comprises a first electrode 40, an insulation film 30 with an opening 30w, a group III oxide layer 20a, and at least one group III nitride layer 20 in this order. The group III oxide layer 20a is in Schottky contact with the first electrode 40 in the opening 30w, and is in contact with the insulation film 30 in a position out of the opening 30w. The thickness Tof a part of the group III oxide layer 20a, which is in contact with the first electrode 40 is smaller than the thickness Tof a part of the group III oxide layer 20a, which is in contact with the insulation film 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a Schottky barrier diode having a small leakage current and a high reverse withstand voltage, and a method for manufacturing the same.

  Group III nitrides, such as GaN (gallium nitride), have various excellent characteristics such as about 3 times the band gap, about 10 times higher breakdown electric field strength, and larger saturation electron velocity than Si (silicon). Therefore, application to power devices (power devices) such as Schottky barrier diodes is expected.

Japanese Unexamined Patent Publication No. 2009-077684 (Patent Document 1) includes a semiconductor layer having a main surface and an opening formed on the main surface in order to provide a Schottky barrier diode having a high reverse breakdown voltage. A nitride insulating film; a Schottky electrode formed so as to be in contact with the main surface; and a field plate electrode connected to the Schottky electrode and formed so as to overlap the nitride insulating film. Disclosed is a Schottky barrier diode having a hydrogen concentration of less than 3.8 × 10 ²² cm ⁻³ .

JP 2009-077684 A

  A Schottky barrier diode disclosed in Japanese Patent Application Laid-Open No. 2009-077684 (Patent Document 1) includes a semiconductor layer formed when a nitride insulating film is formed on a main surface of a semiconductor layer by a plasma CVD (plasma chemical vapor deposition) method. Since the main surface side of the semiconductor layer is damaged by plasma, a defect level is generated on the main surface side of the semiconductor layer in contact with the Schottky electrode, which is damaged by the plasma, so that a large leakage current occurs when a reverse voltage is applied. As a result, the reverse withstand voltage is low.

  Accordingly, an object of the present invention is to solve the above problems and provide a Schottky barrier diode having a small leakage current when a reverse voltage is applied and a high reverse withstand voltage and a method for manufacturing the same.

  A Schottky barrier diode according to an aspect of the present invention includes a first electrode, an insulating film having an opening, a group III oxide layer, and at least one group III nitride layer in this order, The group III oxide layer is in Schottky contact with and in contact with the first electrode at the opening, and is in contact with the insulating film at other than the opening, and the thickness of the portion of the group III oxide layer in contact with the first electrode is The thickness of the portion of the group III oxide layer in contact with the insulating film is smaller.

  A method for manufacturing a Schottky barrier diode according to another aspect of the present invention includes a step of forming a group III oxide layer on at least one group III nitride layer, and forming an insulating film on the group III oxide layer. A step of forming an opening by removing a part of the insulating film, and a thickness of the group III oxide layer under the opening by removing at least a part of the group III oxide layer under the opening. And a step of forming a first electrode in contact with the group III oxide layer under the opening by Schottky contact, and a thickness of a portion of the group III oxide layer in contact with the first electrode Is smaller than the thickness of the portion of the group III oxide layer in contact with the insulating film.

  According to the above, it is possible to provide a Schottky barrier diode having a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and a method for manufacturing the same.

It is a schematic sectional drawing which shows a certain example of the Schottky barrier diode concerning a certain aspect of this invention. It is a schematic sectional drawing which shows another example of the Schottky barrier diode concerning a certain aspect of this invention. It is a schematic sectional drawing which shows a certain example of the manufacturing method of the Schottky barrier diode concerning another aspect of this invention. It is a schematic sectional drawing which shows another example of the manufacturing method of the Schottky barrier diode concerning another aspect of this invention. It is a schematic sectional drawing which shows the first half process part of another example of the manufacturing method of the Schottky barrier diode concerning another aspect of this invention. It is a schematic sectional drawing which shows the latter half process part of another example of the manufacturing method of the Schottky barrier diode concerning another aspect of this invention. It is a schematic sectional drawing which shows an example with the conventional Schottky barrier diode. It is a graph which shows the relationship between the reverse voltage and leakage current density in the Schottky barrier diode of an Example and a comparative example. It is a graph which shows the relationship between the forward voltage and the forward current density in the Schottky barrier diode of an Example and a comparative example.

<Description of Embodiment of the Present Invention>
A Schottky barrier diode according to an embodiment of the present invention includes a first electrode, an insulating film having an opening, a group III oxide layer, and at least one group III nitride layer in this order. The Group III oxide layer is in Schottky contact with and in contact with the first electrode at the opening, and is in contact with the insulating film at the portion other than the opening, and the thickness of the portion in contact with the first electrode of the Group III oxide layer Is smaller than the thickness of the portion of the group III oxide layer in contact with the insulating film. In the Schottky barrier diode of this embodiment, the damage received on the main surface side of the group III oxide layer during the formation of the insulating film is removed in the portion of the group III oxide layer in contact with the first electrode. Therefore, the leak current when applying the reverse voltage is small and the reverse withstand voltage is high.

  In the Schottky barrier diode of this embodiment, the thickness of the portion of the group III oxide layer in contact with the first electrode is less than 3 nm, and the thickness of the portion of the group III oxide layer in contact with the insulating film is less than 5 nm. be able to. Such a Schottky barrier diode has a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and also has a high forward current and a low on-resistance when a forward voltage is applied.

  In the Schottky barrier diode of the present embodiment, the group III oxide layer and the group III nitride layer may be the same in at least one group III element contained. Such a Schottky barrier diode has a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and a small variation in on-resistance and reverse withstand voltage.

  In the Schottky barrier diode of the present embodiment, the group III nitride layer includes a first n-type group III nitride layer and a second n-type group III nitride layer, and the first n-type group III nitride is included. The carrier concentration of the physical layer can be made higher than the carrier concentration of the second n-type group III nitride layer. Such a Schottky barrier diode has a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and a small variation in on-resistance and reverse withstand voltage.

  The Schottky barrier diode of this embodiment can further include a conductive support on the group III nitride layer side. Such a Schottky barrier diode has a small leakage current when a reverse voltage is applied, a high reverse withstand voltage, and a high mechanical strength.

  The Schottky barrier diode of the present embodiment can further include a conductive support on the first electrode side. Such a Schottky barrier diode has a small leakage current when a reverse voltage is applied, a high reverse withstand voltage, and a high mechanical strength.

  A method of manufacturing a Schottky barrier diode according to another embodiment of the present invention includes a step of forming a group III oxide layer on at least one group III nitride layer, and an insulating film on the group III oxide layer. Forming the opening by removing a part of the insulating film, removing at least a part of the group III oxide layer under the opening, and removing the group III oxide layer under the opening. Reducing the thickness, and forming a first electrode in contact with the group III oxide layer under the opening by Schottky contact, and the thickness of the portion of the group III oxide layer in contact with the first electrode The thickness is smaller than the thickness of the portion of the group III oxide layer in contact with the insulating film. Since the manufacturing method of the Schottky barrier diode of this embodiment reduces the thickness of the group III oxide layer under the opening by removing at least a part of the group III oxide layer under the opening, the group III In the portion of the oxide layer in contact with the first electrode, the damage received on the main surface side of the group III oxide layer during the formation of the insulating film is removed, so that the leakage current when the reverse voltage is applied is A small Schottky barrier diode with a high reverse withstand voltage can be manufactured.

  In the method for manufacturing a Schottky barrier diode according to another embodiment of the present invention, the thickness of the portion in contact with the first electrode of the group III oxide layer is less than 3 nm, and the portion in contact with the insulating film of the group III oxide layer Can be less than 5 nm. Such a Schottky barrier diode manufacturing method is such that when the reverse voltage is applied, the leakage current is small and the reverse withstand voltage is high, and the forward direction when the forward voltage is applied. A Schottky barrier diode with high current and low on-resistance can be manufactured.

  In the method for manufacturing a Schottky barrier diode according to another embodiment of the present invention, the group III oxide layer and the group III nitride layer may have the same at least one group III element contained therein. Such a Schottky barrier diode manufacturing method can manufacture a Schottky barrier diode having a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and a small variation in on-resistance and reverse withstand voltage.

  In the method for manufacturing a Schottky barrier diode according to another embodiment of the present invention, the group III nitride layer includes a first n-type group III nitride layer and a second n-type group III nitride layer, The carrier concentration of the first n-type group III nitride layer can be higher than the carrier concentration of the second n-type group III nitride layer. Such a Schottky barrier diode manufacturing method can manufacture a Schottky barrier diode having a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and a small variation in on-resistance and reverse withstand voltage.

  In the method for manufacturing a Schottky barrier diode according to another embodiment of the present invention, the group III nitride layer is formed on the conductive support before the step of forming the group III oxide layer on the group III nitride layer. A forming step may be further included. Such a Schottky barrier diode manufacturing method can manufacture a Schottky barrier diode having a small leakage current when a reverse voltage is applied and a high reverse breakdown voltage and a high mechanical strength.

  In the method for manufacturing a Schottky barrier diode according to another embodiment of the present invention, after the step of forming the first electrode in contact with the group III oxide layer in the opening by Schottky contact, the first electrode side is electrically conductive. A step of forming a conductive support. Such a Schottky barrier diode manufacturing method can manufacture a Schottky barrier diode having a small leakage current when a reverse voltage is applied and a high reverse breakdown voltage and a high mechanical strength.

<Details of Embodiment of the Present Invention>
Hereinafter, details of embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1: Schottky barrier diode]
As shown in FIGS. 1 and 2, the Schottky barrier diode 1 of the present embodiment includes a first electrode 40, an insulating film 30 having an opening 30w, a group III oxide layer 20a, and at least one layer. A group III nitride layer 20 in this order, and the group III oxide layer 20a is in Schottky contact with and in contact with the first electrode 40 at the opening 30w, and is in contact with the insulating film 30 at other than the opening 30w. The thickness T _{1 of the} portion in contact with the first electrode 40 of the group III oxide layer 20a is smaller than the thickness T _{0 of the} portion in contact with the insulating film 30 of the group III oxide layer 20a. Here, the thickness T ₀ of the portion in contact with the insulating film 30 of the group III oxide layer 20a and the thickness T _{1 of the} portion in contact with the first electrode 40 are measured by a spectroscopic ellipso method.

The Schottky barrier diode 1 of the present embodiment has a group III, because the thickness T ₁ of the group III oxide layer 20 a in contact with the first electrode 40 is smaller than the thickness T _{0 of the} part in contact with the insulating film 30. In the portion of the oxide layer 20a that is in contact with the first electrode 40, the damage 20ad received on the main surface side of the group III oxide layer 20a during the formation of the insulating film 30 is removed, so that a reverse voltage is applied. The leakage current is small and the reverse withstand voltage is high. Here, the reverse voltage and the leakage current are measured by a curve tracer.

In the Schottky barrier diode 1 of the present embodiment, the thickness T _{1 of the} portion in contact with the first electrode 40 of the group III oxide layer 20a is less than 3 nm, and the portion of the group III oxide layer in contact with the insulating film 30 is less than 3 nm. The thickness T ₀ is preferably less than 10 nm. The Schottky barrier diode 1 has a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and a high forward current and a low on-resistance when a forward voltage is applied. Here, the forward voltage and the forward current are measured by a curve tracer.

The thickness T _{1 of the} portion in contact with the first electrode 40 of the group III oxide layer 20a is such that the forward current when the forward voltage is applied to the Schottky barrier diode 1 is increased and the on-resistance is decreased. Desirably, it is preferably less than 3.0 nm, more preferably less than 1.0 nm, and there is no portion in contact with the first electrode 40 of the group III oxide layer 20a. Although it is more preferable to be in contact with the electrode 40, it is difficult to completely remove the group III oxide layer 20a formed while maintaining the shape of the opening 30w of the insulating film 30.

Further, the thickness T _{0 of the} portion of the group III oxide layer 20a in contact with the insulating film 30 is such that the forward current when the forward voltage is applied to the Schottky barrier diode 1 is increased and the on-resistance is decreased. From the viewpoint of easily forming the thickness T _{1 of the} portion in contact with the first electrode 40 of the group III oxide layer 20a, it is larger than the thickness T ₁ , preferably less than 10.0 nm, and more preferably less than 6.0 nm. . In addition, the thickness T _{0 of the} portion of the group III oxide layer 20a that is in contact with the insulating film 30 is the same as that when the insulating film 30 is formed on the group III oxide layer 20a formed on the group III nitride layer 20. From the viewpoint of preventing damage 20ad received on the main surface side of group oxide layer 20a from reaching group III nitride layer 20, it is preferably 1.0 nm or more, more preferably 2.0 nm or more, and 4.0 nm or more. Further preferred.

In the Schottky barrier diode 1 of this embodiment, from the viewpoint of reliably removing the damage 20ad received on the main surface side of the group III oxide layer 20a during the formation of the insulating film 30, the group III oxide layer 20a the difference T ₀ -T ₁ of the thickness T ₁ of the thickness T ₀ and the portion in contact with the first electrode 40 of the group III oxide layer 20a of the portion in contact with the insulating film 30, over 1.0nm preferably, 3 More preferably, it is 0.0 nm or more, and further preferably 5.0 nm or more.

  As shown in FIGS. 1 and 2, in the Schottky barrier diode 1 of the present embodiment, the group III oxide layer 20a and the group III nitride layer 20 are the same in at least one group III element contained. It is preferable. Such a Schottky barrier diode 1 has a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and a small variation in on-resistance and reverse withstand voltage.

  As shown in FIGS. 1 and 2, in the Schottky barrier diode 1 of this embodiment, the group III nitride layer 20 includes a first n-type group III nitride layer 21 and a second n-type group III nitride. The carrier concentration of the first n-type group III nitride layer 21 is preferably higher than the carrier concentration of the second n-type group III nitride layer 22. Such a Schottky barrier diode 1 has a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and a small variation in on-resistance and reverse withstand voltage. Here, the carrier concentration of the first n-type group III nitride layer 21 and the second n-type group III nitride layer 22 is CV (capacitance-voltage) method, SIMS (secondary ion mass spectrometry) method. It is measured by.

The first electrode 40, the insulating film 30 having the opening 30w, the group III oxide layer 20a, and at least one group III nitride layer 20 in the Schottky barrier diode 1 of the present embodiment will be described below. In the specific names of the electrodes and metal layers in this specification, the notation “M ₁ / M ₂ /... / M _n ” indicates an n-layer structure of n metals, and “M ₁ − The notation “M ₂ −... −M _n ” indicates an alloy structure of n metals.

(First electrode)
The first electrode 40 is shot on the group III oxide layer 20a (or the group III nitride layer 20 when the thickness T _{1 of the} portion in contact with the first electrode 40 of the group III oxide layer 20a is 0 nm). If it contacts by key contact, there will be no restriction | limiting in particular, A Ni / Au electrode, a Ti / Au electrode, and a Pt electrode are mentioned.

(Insulating film having an opening)
The insulating film 30 having the opening 30w is not particularly limited as long as it can form a field plate structure, but a SiN _x (silicon nitride) film, a SiO ₂ (silicon oxide) film, or the like is used from the viewpoint of high insulation. Preferably mentioned.

(Group III oxide layer)
The group III oxide layer 20a is not particularly limited, but between the metal element included in the first electrode 40 that is in Schottky contact with the group III oxide layer 20a and the element included in the group III nitride layer 20. From the viewpoint of not generating a product other than the product to be generated and from the viewpoint of preventing an element contained in the group III oxide layer 20a from being diffused into the group III nitride layer 20, the group III oxide layer 20a and About the group III nitride layer 20, it is preferable that at least one kind of the group III element to be contained is the same, more preferably all kinds of the group III element to be contained are the same. More preferably, all types of composition ratios are the same. Here, the chemical composition of the group III oxide layer 20a is measured by XPS (X-ray photoelectron spectroscopy).

(Group III nitride layer)
The group III nitride layer 20 is not particularly limited, but from the viewpoint of preventing the elements contained in the group III oxide layer 20a from atom diffusing into the group III nitride layer 20, the group III nitride layer 20 and the group III Regarding group oxide layer 20a, it is preferable that at least one kind of group III element to be contained is the same, more preferably all kinds of group III elements to be contained are the same, and all of group III elements to be contained More preferably, the composition ratios of the types are the same. Here, the chemical composition of the group III nitride layer 20 is measured by an XPS method, a SIMS method, or the like.

The group III nitride layer 20 includes a first n-type group III nitride layer 21 and a second n-type group III nitride layer 22, and the second n-type group III nitride layer 22 is the first n-type group III nitride layer 22. Located on the electrode 40 side, the carrier concentration of the first n-type group III nitride layer 21 is higher than the carrier concentration of the second n-type group III nitride layer 22. The carrier concentration of the first n-type group III nitride layer 21 is preferably 5 × 10 ¹⁶ cm ⁻³ or more and 1 × 10 ²² cm ⁻³ or less from the viewpoint of reducing on-resistance and not impairing crystallinity. It is more preferably 5 × 10 ¹⁷ cm ⁻³ or more and 1 × 10 ¹⁹ cm ⁻³ or less. The carrier concentration of the second n-type group III nitride layer 22 is 1 × 10 ¹⁵ cm ⁻³ or more and 3 × 10 ¹⁶ cm ⁻³ or less from the viewpoint of increasing the reverse withstand voltage and maintaining low on-resistance. Is preferably 4 × 10 ¹⁵ cm ⁻³ or more and 1 × 10 ¹⁶ cm ⁻³ or less.

  As shown in FIG. 1, in the Schottky barrier diode 1 of the present embodiment, it is preferable that a conductive support 13 is further included on the group III nitride layer 20 side. Such a Schottky barrier diode 1 has a small leakage current when a reverse voltage is applied, a high reverse breakdown voltage, and a high mechanical strength.

(Conductive support)
The conductive support 13 is not particularly limited as long as it is a conductive support from the viewpoint of forming the vertical Schottky barrier diode 1, and is not limited to a Si (silicon) substrate, a group III nitride substrate, or a group III-V compound. A substrate, a II-VI group compound substrate, a metal substrate, etc. are mentioned. The conductive support 13 is preferably a group III nitride substrate or a group III nitride film 13 s from the viewpoint of forming a high-quality group III nitride layer 20 on the conductive support 13. In the case where the conductive support 13 is a metal substrate, the Mo (in ohmic contact with the group III nitride layer 20 from the viewpoint that the linear thermal expansion coefficient is close to that of the Schottky barrier diode 1 and the thermal conductivity is high. Preferable examples include a molybdenum substrate and a W (tungsten) substrate.

  As shown in FIG. 2, in the Schottky barrier diode 1 of this embodiment, it is preferable to further include a conductive support 80 on the first electrode 40 side. Such a Schottky barrier diode has a small leakage current when a reverse voltage is applied, a high reverse withstand voltage, and a high mechanical strength.

(Conductive support)
The conductive support 80 is not particularly limited as long as it is a conductive support from the viewpoint of forming the vertical Schottky barrier diode 1, and is not limited to a Si substrate, a group III nitride substrate, a group III-V compound substrate, II -Group VI compound substrates, metal substrates and the like.

(First example of Schottky barrier diode)
As shown in FIG. 1, the first example of the Schottky barrier diode 1 of this embodiment includes a pad electrode 50, a first electrode 40, an insulating film 30 having an opening 30w, a group III oxide layer 20a, a group III. The second n-type group III nitride layer 22 and the first n-type group III nitride layer 21, which are the nitride layer 20, the conductive support 13, and the second electrode 60 are arranged in this order. That is, the Schottky barrier diode 1 of the first example is one in which the conductive support 13 is disposed on the group III nitride layer 20 side.

  First electrode 40, insulating film 30 having opening 30w, group III oxide layer 20a, group III nitride layer 20, second n-type group III nitride layer 22, and first n-type group III nitride Since the physical layer 21 and the conductive support 13 are the same as described above, they are not repeated here.

(Pad electrode)
There is no restriction | limiting in particular in the pad electrode 50, A Ti / Au electrode, a Ni / Pt / Au electrode, etc. are mentioned.

(Second electrode)
The second electrode 60 is not particularly limited, but from the viewpoint of reducing the on-resistance of the Schottky barrier diode 1, when the conductive support 13 is a semiconductor, an electrode that is in ohmic contact with the conductive support 13 is preferable. . When the conductive support 13 is a group III nitride substrate or group III nitride film 13s, the second electrode 60 is preferably an Al / Ti / Au electrode, an Al / Ti / Pt / Au electrode, or the like. When the conductive support 13 is a metal substrate, the second electrode 60 can be omitted.

(Second example of Schottky barrier diode)
As shown in FIG. 2, the second example of the Schottky barrier diode 1 according to the present embodiment includes a conductive support electrode 80e, a conductive support 80, a conductive support electrode 80e, a bonding metal layer 80b, a pad metal layer. 70p, spacer metal layer 70s, first electrode 40, insulating film 30 having opening 30w, second n-type group III nitride layer 22 which is group III nitride layer 20, and first n-type group III nitride The physical layer 21 and the second electrode 60 are arranged in this order. That is, in the second example of the Schottky barrier diode 1 of the present embodiment, the conductive support 80 is disposed on the first electrode 40 side.

  The conductive support 80, the first electrode 40, the insulating film 30 having the opening 30w, the group III oxide layer 20a, the second n-type group III nitride layer 22 which is the group III nitride layer 20, and the first Since the n-type group III nitride layer 21 and the second electrode 60 are the same as described above, they are not repeated here.

(Conductive support electrode)
The conductive support electrode 80e is not particularly limited, but from the viewpoint of reducing the on-resistance of the Schottky barrier diode 1, when the conductive support 80 is a semiconductor, an electrode that makes ohmic contact with the conductive support 80 is not provided. preferable. When the conductive support 80 is a Si substrate, the conductive support electrode 80e is preferably a Ti / Au electrode, an Al electrode, or the like. When the conductive support 80 is a metal substrate, the conductive support electrode 80e can be omitted.

(Junction metal layer)
The bonding metal layer 80b includes a conductive support electrode 80e (or a conductive support 80 when the conductive support electrode is omitted when the conductive support 80 is a metal) and a pad metal layer 70p described later. There is no particular limitation as long as it is suitable for bonding, and an Au—Sn metal layer, a Sn—Ag—Cu metal layer, and the like can be given.

(Pad metal layer)
The pad metal layer 70p is not particularly limited, and examples thereof include a Ti / Pt / Au metal layer and a Ni / Pd / Au metal layer.

(Spacer metal layer)
The spacer metal layer 70s has irregularities when the first electrode 40 is formed on the opening 30w of the insulating film 30 having the opening 30w and its vicinity (for example, a range of a distance of 10 μm or less from the edge of the opening 30w). If it is suitable for planarization, there will be no restriction | limiting in particular, A Ti / Au metal layer, a Ni / Au metal layer, etc. are mentioned.

[Embodiment 2: Manufacturing Method of Schottky Barrier Diode]
As shown in FIGS. 3 to 6, the manufacturing method of the Schottky barrier diode 1 of the present embodiment is a step of forming a group III oxide layer 20 a on the group III nitride layer 20 (FIG. 3A, FIG. 4 (A) and FIG. 5 (A)), the step of forming the insulating film 30 on the group III oxide layer 20a (FIG. 3A, FIG. 4A and FIG. 5A), insulation The step of forming the opening 30w by removing a part of the film 30 (FIG. 3B, FIG. 4B and FIG. 5B), and the group III oxide layer 20a under the opening 30w The step of reducing the thickness of the group III oxide layer 20a under the opening 30w by removing at least a part (FIGS. 3B, 4B, and 5B), and the opening Step of forming first electrode 40 in contact with group III oxide layer 20a under 30w by Schottky contact (FIG. (C), and FIG. 4 (C) and FIG. 5 (C)), wherein the part in contact with the first electrode 40 of the Group III oxide layer 20a thickness T ₁ is the group III oxide layer 20a It is smaller than the thickness T _{0 of the} portion in contact with the insulating film 30.

In the manufacturing method of the Schottky barrier diode 1 of this embodiment, the thickness of the group III oxide layer 20a under the opening 30w is reduced by removing at least a part of the group III oxide layer 20a under the opening 30w. Since the thickness T ₀ is reduced to the thickness T ₁ , the main surface side of the group III oxide layer 20a is formed in the portion of the group III oxide layer 20a in contact with the first electrode 40 when the insulating film 30 is formed. Since the damage 20ad received is removed, a Schottky barrier diode with a small leakage current when a reverse voltage is applied and a high reverse withstand voltage can be manufactured. Below, each said process is demonstrated in detail.

(Step of forming a group III oxide layer on the group III nitride layer)
As shown in FIG. 3A, FIG. 4A, and FIG. 5A, in the step of forming the group III oxide layer 20a on the group III nitride layer 20, the group III oxide layer 20a is formed. Although there is no particular limitation on the method to be performed, the main surface layer of the group III nitride layer 20 is preferably in an oxygen-containing atmosphere from the viewpoint of efficiently producing a thin group III oxide layer 20a preferably having a thickness of 1 nm or more and less than 5 nm as described later. The method of annealing below is preferred. The annealing temperature is preferably 400 ° C. or higher and 1000 ° C. or lower, and more preferably 850 ° C. or higher and 950 ° C. or lower. The thickness of group III oxide layer 20a can be adjusted by the annealing temperature and annealing time. In this way, a group III oxide layer 20a having a thickness T ₀ is formed.

(Step of forming an insulating film on the group III oxide layer)
As shown in FIGS. 3A, 4A, and 5A, in the step of forming the insulating film 30 over the group III oxide layer 20a, the method of forming the insulating film 30 is particularly limited. However, from the viewpoint of efficiently forming a high-quality insulating film 30, a plasma CVD (plasma chemical vapor deposition) method, a thermal CVD method, a sputtering method, or the like is preferable, and a plasma CVD method is particularly preferable.

  In the step of forming the insulating film 30 on the group III oxide layer 20a, when the insulating film 30 is formed on the group III oxide layer 20a by the plasma CVD method, the main surface layer side of the group III oxide layer 20a is formed. Receives damage 20ad from plasma. The depth of the damage 20ad from the main surface of the group III oxide layer 20a is about 1 nm to 5 nm, although it depends on the intensity of the plasma.

(Process of forming an opening by removing a part of the insulating film)
As shown in FIGS. 3B, 4B, and 5B, part of the insulating film 30 is removed in the step of forming the opening 30w by removing part of the insulating film 30. Although there is no particular limitation on the method of performing, from the viewpoint of efficiently forming the opening 30w, a resist mask (not shown) having an opening is formed by photolithography, and the insulating film 30 under the opening of the resist mask is formed. A method of etching by wet etching using hydrofluoric acid is preferable.

(Step of reducing the thickness of the group III oxide layer under the opening by removing at least part of the group III oxide layer under the opening)
As shown in FIGS. 3B, 4B, and 5B, at least part of the group III oxide layer 20a under the opening 30w is removed to remove the group III under the opening 30w. In the step of reducing the thickness of the oxide layer 20a, a method for removing at least a part of the group III oxide layer 20a under the opening 30w is not particularly limited, but the group III oxide layer under the opening 30w is not particularly limited. From the viewpoint of efficiently reducing the thickness of the portion 20a, after removing a part of the insulating film 30, the at least a part of the group III oxide layer 20a under the opening of the resist mask is subsequently subjected to hydrogen fluoride. A method of etching by wet etching using an acid is preferable.

  Further, from the viewpoint of removing metal contamination on the surface of the group III oxide layer 20a and securing a good Schottky junction interface, the portion of the group III oxide layer 20a under the opening 30w is washed with hydrochloric acid. Is preferred.

As described above, reducing the thickness of the portion of the Group III oxide layer 20a under the opening 30w thick T ₀ to a thickness T _1. Therefore, the damage 20ad received on the main surface side of the group III oxide layer 20a having the thickness T ₀ when the insulating film 30 is formed in the portion below the opening 30w of the group III oxide layer 20a is It is removed by etching. From the viewpoint of surely removing the damage 20ad, the difference T ₀ -T ₁ between the thickness T ₀ before etching and the thickness T ₁ after etching in the portion below the opening 30w of the group III oxide layer 20a is: 1 nm or more is preferable, 3 nm or more is more preferable, and 5 nm or more is more preferable.

(Process for forming first electrode in contact with group III oxide layer under opening by Schottky contact)
As shown in FIG. 3C, FIG. 4C, and FIG. 5C, in the step of forming the first electrode 40 in contact with the group III oxide layer 20a under the opening 30w by Schottky contact, The method for forming the first electrode 40 is not particularly limited, and examples include EB (electron beam) vapor deposition, resistance heating vapor deposition, and sputtering.

In this manner, the thickness T _{1 of the} portion in contact with the first electrode 40 of the group III oxide layer 20a is smaller than the thickness T _{0 of the} portion of the group III oxide layer 20a in contact with the insulating film 30. 1 Schottky barrier diode 1 is obtained.

As shown in FIG. 3 to FIG. 6, in the method for manufacturing the Schottky barrier diode 1 according to another embodiment of the present invention, the thickness T _{1 of the} portion in contact with the first electrode 40 of the group III oxide layer 20 a is The thickness T _{0 of the} portion in contact with the insulating film 30 of the group III oxide layer 20a is preferably less than 10 nm. The manufacturing method of such a Schottky barrier diode 1 is a Schottky that has a small leakage current when a reverse voltage is applied and a high reverse withstand voltage, and a high forward current and a low on-resistance when a forward voltage is applied. Barrier diodes can be manufactured.

The thickness T _{1 of the} portion in contact with the first electrode 40 of the group III oxide layer 20a is desirably small from the viewpoint of increasing the forward current and decreasing the on-resistance when a forward voltage is applied. Less than .0 nm, more preferably less than 1.0 nm, and there is no portion in contact with the first electrode 40 of the group III oxide layer 20a, ie, the group III nitride layer 20 is in direct contact with the first electrode 40. Although it is more preferable, it is difficult to completely remove the group III oxide layer 20a formed while maintaining the shape of the opening 30w of the insulating film 30.

Further, the thickness T _{0 of the} portion of the group III oxide layer 20a in contact with the insulating film 30 is such that the forward current when the forward voltage is applied to the Schottky barrier diode 1 is increased and the on-resistance is decreased. From the viewpoint of easily forming the thickness T _{1 of the} portion in contact with the first electrode 40 of the group III oxide layer 20a, it is larger than the thickness T ₁ , preferably less than 10.0 nm, and more preferably less than 6.0 nm. . In addition, the thickness T _{0 of the} portion of the group III oxide layer 20a that is in contact with the insulating film 30 is the same as that when the insulating film 30 is formed on the group III oxide layer 20a formed on the group III nitride layer 20. From the viewpoint of preventing damage 20ad received on the main surface side of group oxide layer 20a from reaching group III nitride layer 20, it is preferably 1 nm or more, more preferably 2 nm or more, and further preferably 4 nm or more.

  As shown in FIGS. 3 to 6, in the method for manufacturing the Schottky barrier diode 1 according to another embodiment of the present invention, the group III oxide layer 20 a and the group III nitride layer 20 include a group III element contained therein. It is preferable that at least one of the same is the same. Such a manufacturing method of the Schottky barrier diode 1 can manufacture a Schottky barrier diode that has a small leakage current when a reverse voltage is applied and a high reverse withstand voltage and a small variation in on-resistance and reverse withstand voltage.

  As shown in FIGS. 3 to 6, in the method for manufacturing the Schottky barrier diode 1 according to another embodiment of the present invention, the group III nitride layer 20 includes the first n-type group III nitride layer 21 and 2, and the carrier concentration of the first n-type group III nitride layer 21 can be higher than the carrier concentration of the second n-type group III nitride layer 22. . Such a manufacturing method of the Schottky barrier diode 1 can manufacture a Schottky barrier diode that has a small leakage current when a reverse voltage is applied and a high reverse withstand voltage and a small variation in on-resistance and reverse withstand voltage.

  As shown in FIGS. 3 and 4, in the method for manufacturing the Schottky barrier diode 1 according to another embodiment of the present invention, a step of forming a group III oxide layer 20a on the group III nitride layer 20 (FIG. 3). Before (A) and FIG. 4 (A)), the process (FIG. 3 (A) and FIG. 4 (A)) of forming the group III nitride layer 20 on the electroconductive support body 13 can be further included. . Such a Schottky barrier diode 1 is manufactured by forming the Schottky barrier diode 1 further including the conductive support 13 on the group III nitride layer 20 side, thereby reducing a leakage current when a reverse voltage is applied. A Schottky barrier diode with high reverse breakdown voltage and high mechanical strength can be manufactured.

(Step of forming a group III nitride layer on a conductive support)
As shown in FIGS. 3A and 4A, the group III nitride layer 20 on the conductive support 13 before the step of forming the group III oxide layer 20a on the group III nitride layer 20 is formed. In the step of forming the layer III, the method of forming the group III nitride layer 20 is not particularly limited, but from the viewpoint of forming the high-quality group III nitride layer 20, a MOCVD (metal organic chemical vapor deposition) method, MBE (molecular beam growth) method, HVPE (hydride vapor phase growth) method, vapor phase method such as sublimation method, liquid phase method such as high nitrogen pressure solution method and flux method are preferable.

  As shown in FIG. 5 and FIG. 6, in the method for manufacturing the Schottky barrier diode 1 according to another embodiment of the present invention, the first electrode is in contact with the group III oxide layer 20 a under the opening 30 w by Schottky contact. After the step of forming 40 (FIG. 5C), a step of forming the conductive support 80 on the first electrode 40 side (FIGS. 5D to 5F) can be further included. Such a Schottky barrier diode 1 manufacturing method can manufacture a Schottky barrier diode that has a small leakage current when a reverse voltage is applied, a high reverse withstand voltage, and a high mechanical strength.

(Step of forming a conductive support on the first electrode side)
As shown in FIGS. 5D to 5F, on the first electrode 40 side after the step of forming the first electrode 40 in contact with the group III oxide layer 20a under the opening 30w by Schottky contact. In the step of forming the conductive support 80, the method for forming the conductive support 80 on the first electrode 40 side is not particularly limited, and examples thereof include the following methods.

  First, as shown in FIGS. 5D and 5E, a spacer metal layer 70s and a pad metal layer 70p are formed in this order on the first electrode 40 side. The method for forming the spacer metal layer 70s and the pad metal layer 70p is not particularly limited, and examples include EB (electron beam) vapor deposition, resistance heating vapor deposition, and sputtering.

  Next, as shown in FIG. 5F, a conductive support electrode 80e and a bonding metal layer 80b are formed in this order on the conductive support 80. The method for forming the conductive support electrode 80e is not particularly limited, and examples thereof include EB vapor deposition, resistance heating vapor deposition, and sputtering. The method for forming the bonding metal layer 80b is not particularly limited, and examples thereof include EB vapor deposition, resistance heating vapor deposition, and sputtering.

  Next, the conductive support 80 is formed on the first electrode 40 side by bonding the pad metal layer 70p and the bonding metal layer 80b. The method for bonding the pad metal layer 70p and the bonding metal layer 80b is not particularly limited, and examples thereof include a eutectic bonding method, a metal diffusion method, and a surface activation method.

(First example of manufacturing method of Schottky barrier diode)
As shown in FIGS. 1 and 3, the first example of the manufacturing method of the Schottky barrier diode of the present embodiment uses a group III nitride substrate as the conductive support 13, and the group III nitride layer 20 side is provided. 3 is an example of a method for manufacturing the first example Schottky barrier diode 1 of Embodiment 1 including a conductive support 13.

As shown in FIG. 3, the first example of the manufacturing method of the Schottky barrier diode of the present embodiment includes a first n-type group III nitride layer 21 as a group III nitride layer 20 on the conductive support 13 and A step of forming the second group III nitride layer 22 in this order (FIG. 3A), and a group III oxide layer 20 a on the second group III nitride layer 22 of the group III nitride layer 20. A step of forming (FIG. 3A), a step of forming the insulating film 30 having a thickness T ₀ on the group III oxide layer 20a (FIG. 3A), and a part of the insulating film 30 are removed. Thus, the step of forming the opening 30w (FIG. 3B) and the removal of at least a part of the group III oxide layer 20a under the opening 30w of the group III oxide layer 20a under the opening 30w step of reducing the thickness from the thickness T ₀ to a thickness T ₁ (to FIG. 3 (B)) and an opening A step of forming the first electrode 40 in contact with the group III oxide layer 30 w below by Schottky contact (FIG. 3C), and a step of forming the pad electrode 50 on the first electrode 40 (FIG. 3 ( D)) and reducing the thickness of the conductive support 13 by grinding and polishing a part of the conductive support 13 and removing the damage 13d received by the conductive support 13 by etching. A step of adjusting (FIGS. 3E to 3G) and a step of forming the second electrode 60 on the conductive support 13 (FIG. 3H).

  Since the method performed in the steps shown in FIGS. 3A to 3C is the same as the above method, it is not repeated here. A method for forming the pad electrode 50 in the step of forming the pad electrode 50 over the first electrode 40 shown in FIG. 3D is not particularly limited, and an EB (electron beam) vapor deposition method, a resistance heating vapor deposition method, and a sputtering method. Etc. In the process of reducing and adjusting the thickness of the conductive support 13 shown in FIGS. 3E to 3G, the method for grinding and polishing a part of the conductive support 13 is not particularly limited. General methods such as mechanical grinding, mechanical polishing, and CMP (Chemical Mechanical Polishing) can be used, and the method for removing the damage 13d received by the conductive support 13 by etching is not particularly limited. Reactive ion etching). The method for forming the second electrode 60 in the step of forming the second electrode 60 on the conductive support 13 shown in FIG. 3H is not particularly limited, and an EB vapor deposition method, a resistance heating vapor deposition method, a sputtering method, or the like. Is mentioned.

(Second example of manufacturing method of Schottky barrier diode)
As shown in FIGS. 1 and 4, the second example of the manufacturing method of the Schottky barrier diode of the present embodiment uses a composite substrate 10 including a group III nitride film 13 s to be a conductive support 13, and III 2 is an example of a method for manufacturing the first example Schottky barrier diode 1 of Embodiment 1 including a conductive support 13 on the group nitride layer 20 side. Here, from the viewpoint of the group III nitride film 13s becoming the conductive support 13, the thickness of the group III nitride film 13s is preferably 10 μm or more, more preferably 20 μm or more, and further preferably 50 μm or more. Further, from the viewpoint of reducing the amount of expensive group III nitride used in order to reduce cost, the thickness of group III nitride film 13s is preferably 250 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. .

  The composite substrate 10 used in the second example of the manufacturing method of the Schottky barrier diode of the present embodiment is a substrate obtained by bonding the relatively thick group III nitride film 13 s to the support substrate 11. The form of bonding is not particularly limited, and the support substrate 11 and the group III nitride film 13s may be indirectly bonded with the bonding film 12 interposed therebetween as shown in FIG. The substrate 11 and the group III nitride film 13s may be directly bonded without the bonding film 12 interposed. Although the manufacturing method of the composite substrate 10 is not particularly limited, from the viewpoint of efficient manufacturing, the support substrate 11 and the group III nitride substrate serving as the donor of the group III nitride film 13s are bonded together, and then the group III nitride is formed. It is preferable to manufacture by cutting or grinding and / or polishing to a predetermined position at a predetermined depth from the bonded main surface of the substrate.

As shown in FIG. 4, the second example of the manufacturing method of the Schottky barrier diode of the present embodiment is the first n-type as the group III nitride layer 20 on the group III nitride film 13 s of the composite substrate 10. The step of forming group III nitride layer 21 and second group III nitride layer 22 in this order (FIG. 4A), and on group III nitride layer 22 of group III nitride layer 20 A step of forming the group III oxide layer 20a (FIG. 4A), a step of forming the insulating film 30 having a thickness T ₀ on the group III oxide layer 20a (FIG. 4A), an insulating film, The step of forming the opening 30w by removing a part of 30 (FIG. 4B) and the removal of at least a part of the group III oxide layer 20a under the opening 30w under the opening 30w reducing the thickness of the group III oxide layer 20a having a thickness of T ₀ to a thickness T ₁ (FIG. 4B), a step of forming the first electrode 40 in contact with the group III oxide layer under the opening 30w by Schottky contact (FIG. 4C), and on the first electrode 40 And forming a pad electrode 50 on the substrate (FIG. 4D), grinding part of the support substrate 11 of the composite substrate 10, and polishing the remaining part of the support substrate 11 and the bonding film 12, thereby forming III The process of reducing and adjusting the thickness of the group III nitride film 13s as the conductive support 13 by removing the damage 13sd received by the group nitride film 13s by etching (FIGS. 4E to 4G) And a step of forming the second electrode 60 on the group III nitride film 13s (FIG. 4H).

  Since the method performed in the steps shown in FIGS. 4A to 4D is the same as the above method, it is not repeated here. In the step of reducing and adjusting the thickness of the group III nitride film 13s shown in FIGS. 4E to 4G, a method for grinding a part of the support substrate 11 of the composite substrate 10 is not particularly limited. A general method such as mechanical grinding may be used, and a method for polishing the remaining part of the support substrate 11 and the bonding film 12 is not particularly limited, and is a general method such as mechanical polishing or CMP (chemical mechanical polishing). There are no particular restrictions on the method of removing the damage 13sd received by the group III nitride film 13s by etching, and examples thereof include RIE (reactive ion etching). The method of forming the second electrode 60 in the step of forming the second electrode 60 on the group III nitride film 13s shown in FIG. 4 (H) is not particularly limited, and is an EB (electron beam) evaporation method, resistance heating evaporation. Method, sputtering method and the like.

(Third example of manufacturing method of Schottky barrier diode)
As shown in FIGS. 2 and 5 to 6, the third example of the manufacturing method of the Schottky barrier diode according to the present embodiment uses the composite substrate 10 including the group III nitride film 13 t to use the first electrode 40. 4 is an example of a method for manufacturing a second example Schottky barrier diode 1 of Embodiment 1 including a conductive support 80 on the side. Here, the group III nitride film 13t does not need to be a conductive support, and the thickness of the group III nitride film 13t is reduced from the viewpoint of reducing the amount of expensive group III nitride used in order to reduce costs. Is preferably less than 10 μm, more preferably 1 μm or less, and even more preferably 0.5 μm or less. Further, from the viewpoint of forming a high-quality group III nitride layer 20 on the group III nitride film 13t, the thickness of the group III nitride film 13t is preferably 0.05 μm or more, and more preferably 0.08 μm or more. More preferably, it is 0.1 μm or more.

  The composite substrate 10 used in the third example of the manufacturing method of the Schottky barrier diode of this embodiment is a substrate in which the relatively thin group III nitride film 13t is bonded to the support substrate 11. The form of bonding is not particularly limited, and the support substrate 11 and the group III nitride film 13t may be indirectly bonded with the bonding film 12 interposed therebetween as shown in FIG. The substrate 11 and the group III nitride film 13t may be bonded directly without interposing the bonding film 12. The manufacturing method of the composite substrate 10 is not particularly limited. From the viewpoint of efficient manufacturing, the composite substrate 10 is bonded to a group III nitride substrate serving as a donor of the group III nitride film 13t and is ionized at a predetermined depth from the main surface. After the implantation region is formed and the group III nitride substrate on which the ion implantation region is formed and the support substrate 11 are bonded together, they are separated from the bonded main surface of the group III nitride substrate at a predetermined depth. It is preferable to manufacture by.

As shown in FIGS. 5 to 6, the third example of the manufacturing method of the Schottky barrier diode of the present embodiment is a first group III nitride layer 20 on the group III nitride film 13 t of the composite substrate 10. Forming the n-type group III nitride layer 21 and the second group III nitride layer 22 in this order (FIG. 5A), and the second group III nitride layer of the group III nitride layer 20 A step of forming a group III oxide layer 20a on the layer 22 (FIG. 5A), a step of forming an insulating film 30 having a thickness T ₀ on the group III oxide layer 20a (FIG. 5A), The step of forming the opening 30w by removing a part of the insulating film 30 (FIG. 5B) and the opening by removing at least a part of the group III oxide layer 20a under the opening 30w. low to a thickness T ₁ the thickness of the group III oxide layer 20a under 30w thick T ₀ A step (FIG. 5B) of forming, a step of forming the first electrode 40 in contact with the group III oxide layer under the opening 30w by Schottky contact (FIG. 5C), and the first electrode 40 Step of forming the conductive support 80 on the side (FIGS. 5D to 5F), a part of the support substrate 11 of the composite substrate 10 is ground, the remaining part of the support substrate 11 and the bonding film 12 And removing the group III nitride film 13t damaged by them by etching, thereby exposing the first n-type group III nitride layer 21 of the group III nitride layer 20 (FIG. G) to (I)), a step of forming the second electrode 60 on the first n-type group III nitride layer 21 of the group III nitride layer 20 (FIG. 6J), and a conductive support. 80, forming a conductive support electrode 80e (FIG. 6K).

  Since the method performed in the steps shown in FIGS. 5A to 5F is the same as the above method, it is not repeated here. In the step of exposing the first n-type group III nitride layer 21 of the group III nitride layer 20 shown in FIGS. 6G to 6I, a method of grinding a part of the support substrate 11 of the composite substrate 10 is as follows. Without limitation, a general method such as mechanical grinding may be used, and the remaining part of the support substrate 11 and the bonding film 12 may be removed without any particular limitation, such as etching using hydrofluoric acid. The method of removing the group III nitride film 13t damaged by them by etching is not particularly limited, and examples include RIE (reactive ion etching). A method for forming the second electrode 60 in the step of forming the second electrode 60 illustrated in FIG. 6J is not particularly limited, and examples thereof include an EB (electron beam) evaporation method, a resistance heating evaporation method, and a sputtering method. It is done. The method for forming the conductive support electrode 80e in the step of forming the conductive support electrode 80e on the conductive support 80 shown in FIG. 6 (K) is not particularly limited, and EB (electron beam) evaporation, resistance heating A vapor deposition method, a sputtering method, etc. are mentioned.

Example 1
1. Formation of Group III Nitride Layer on Conductive Support As shown in FIG. 3 (A), Si atom is added as a dopant with a thickness of 500 μm which is a group III nitride substrate as conductive support 13 and the dopant. The first n-type group III nitride layer 21 is formed as the group III nitride layer 20 on the conductive support 13 by the MOCVD method using an n-type GaN substrate having a concentration of 1 × 10 ¹⁸ cm ^−3. Si atom is added as a dopant at a thickness of 0.5 μm, and the dopant concentration is 1 × 10 ¹⁸ cm ^{−3 of} an n ⁺ -type GaN layer and a second n-type group III nitride layer 22. Si atoms were added to form an n ⁻ -type GaN layer having a dopant concentration of 6 × 10 ¹⁵ cm ⁻³ .

2. Formation of Group III Oxide Layer on Group III Nitride Layer Next, the wafer on which the group III nitride layer 20 is formed on the conductive support 13 is placed in a 10% by mass hydrofluoric acid aqueous solution for 10 minutes. After cleaning, annealing is performed in an RTA (rapid annealing furnace) at 900 ° C. in an oxygen atmosphere for a period of time, whereby the thickness of the group III nitride layer 20 on the second n-type group III nitride layer 22 is increased. A 5.0 nm Group III oxide layer 20a was formed. The thickness of the group III oxide layer 20a was measured by a spectroscopic ellipso method. Further, III-group oxide layer 20a from analysis by the XPS method, was Ga ₂ O ₃ layer.

3. Formation of Insulating Film on Group III Oxide Layer Next, on the group III oxide layer 20a, SiH ₄ (silane) gas and NH ₃ (ammonia) gas are used as source gases by plasma CVD, An SiN _x layer having a thickness of 500 nm was formed as the insulating film 30. Subsequently, annealing was performed for 3 minutes at 600 ° C. in a nitrogen atmosphere in an RTA (rapid annealing furnace).

4). Next, as shown in FIG. 3B, a resist mask (not shown) having an opening is formed on the insulating film 30 by photolithography, as shown in FIG. The insulating film 30 was wet-etched using buffered hydrofluoric acid (BHF-110 manufactured by Daikin) to form an opening 30w having a diameter of 200 μm in the insulating film 30.

5. Reduction of thickness of group III oxide layer under opening Next, the above-described wet etching was continued, and so-called over-etching was performed to remove a part of group III oxide layer 20a under opening 30w. Next, the group III oxide layer 20a under the opening 30w was washed with a 10% by mass hydrochloric acid aqueous solution. Next, the resist mask was removed using acetone. When the thickness of the group III oxide layer 20a under the opening 30w was measured by a spectroscopic ellipso method, it was reduced to 2.9 nm.

6). Formation of First Electrode Next, as shown in FIG. 3C, a resist mask (not shown) having an opening is formed on the insulating film 30 by a photolithography method, and is formed under the opening of the resist mask. Then, on the group III oxide layer 20a below the opening 30w of the insulating film 30 and on the insulating film 30 in a range of 20 μm or less from the edge of the opening 30w, a Ni layer having a thickness of 50 nm and A 300 nm thick Au layer is formed and annealed in an RTA at 400 ° C. for 3 minutes in a nitrogen atmosphere to form a Ni / Au electrode that is in Schottky contact with the group III oxide layer 20a as the first electrode 40. did.

7). Formation of Pad Electrode Next, as shown in FIG. 3 (D), a 20 nm-thick Ti layer and a 600 nm-thick Au layer are formed on the first electrode 40 by EB vapor deposition. A Ti / Au electrode was formed as the electrode 50. Next, the resist mask was removed using acetone.

8). Next, as shown in FIGS. 3E to 3G, a part of the conductive support 13 is mechanically ground, mechanically polished, and CMP (chemical machine). Then, the damage received was removed by ICP-RIE (inductively coupled plasma-reactive ion etching). The thickness of the conductive support 13 after CMP and ICP-RIE was 200 μm.

9. Formation of Second Electrode Next, as shown in FIG. 3 (H), a 20 nm thick Al layer, a 20 nm thick Ti layer, and a 600 nm thick Au layer are formed on the conductive support 13 by EB vapor deposition. By forming the layer, an Al / Ti / Au electrode was formed as the second electrode 60.

10. Next, chipping was made into a size of 1000 μm × 1000 μm by forming a marking line by laser scribing and cleaving along the marking line by a break. Thus, as shown in FIG. 1, a Schottky barrier diode 1 made into a chip was obtained.

11. Mounting to Stem Chip-on-chip Schottky barrier diode 1 is die-bonded with second electrode 60 to the stem, and pad electrode 50 electrically connected to first electrode 40 is stemmed with Au (gold) wire. It was mounted on the stem by wire bonding.

12 Evaluation of electrical characteristics The electrical characteristics of the Schottky barrier diode 1 that was made into a chip and mounted on the stem were evaluated by a car's tracer. The relationship between the reverse voltage and the leakage current density in this example is shown by a two-dot chain line in FIG. The relationship between the forward voltage and the forward current density in this example is shown by a two-dot chain line in FIG.

(Example 2)
Example 1 except that the thickness of the group III oxide layer 20a under the opening 30w was reduced from 5 nm to 1.5 nm in reducing the thickness of the group III oxide layer 20a under the opening 30w. Similarly, a Schottky barrier diode 1 made into a chip was manufactured, mounted on a stem, and its electrical characteristics were evaluated. The relationship between the reverse voltage and the leakage current density in this example is shown by a one-dot chain line in FIG. The relationship between the forward voltage and the forward current density in this example is shown by a one-dot chain line in FIG.

(Example 3)
In the reduction of the thickness of the group III oxide layer 20a under the opening 30w, the same as in Example 1 except that the thickness of the group III oxide layer 20a under the opening 30w was reduced from 5 nm to less than 1 nm. Thus, a Schottky barrier diode 1 made into a chip was manufactured, mounted on a stem, and its electrical characteristics were evaluated. The relationship between the reverse voltage and the leakage current density in this example is shown by a solid line in FIG. The relationship between the forward voltage and the forward current density in this example is shown by a solid line in FIG.

(Comparative Example 1)
As shown in FIG. 7, the wafer having the group III nitride layer 20 formed on the conductive support 13 is washed with a 10% by mass hydrofluoric acid aqueous solution for 10 minutes, and then the group III nitride layer 20 is formed. In addition, a Schottky barrier diode 1R formed as a chip in the same manner as in Example 1 except that the insulating film 30 is directly formed without forming the group III oxide layer 20a, is mounted on the stem, Its electrical characteristics were evaluated. The relationship between the reverse voltage and the leakage current density in this comparative example is shown by a broken line in FIG. The relationship between the forward voltage and the forward current density in this comparative example is shown by a broken line in FIG.

  As shown in FIG. 8, the Schottky barrier diodes of Examples 1 to 3 are less likely to have a large leakage current even when the reverse voltage increases, compared to the Schottky barrier diode of Comparative Example 1. Became high. In the Schottky barrier diode 1R of Comparative Example 1 shown in FIG. 7, the insulating film 30 is formed on the group III nitride layer 20 without interposing the group III oxide layer, and an opening is formed in the insulating film 30. Since 30w is formed, the damage 20d received during the formation of the insulating film 30 remains on the main surface side of the group III nitride layer 20 in Schottky contact with and in contact with the first electrode 40 in the opening 30w. Furthermore, it is considered that the leakage current when the reverse voltage is increased is increased, and the reverse withstand voltage is decreased. On the other hand, in the Schottky barrier diodes 1 of Examples 1 to 3 shown in FIG. 1, the insulating film 30 is formed on the group III nitride layer 20 with the group III oxide layer 20a interposed, and the insulating film Since the opening 30w is formed at 30 and at least a part of the group III oxide layer 20a under the opening 30w is removed, the group III is in contact with the first electrode 40 through the Schottky contact at the opening 30w. Since the damage 20ad received during the formation of the insulating film 30 on the main surface side of the oxide layer 20a has been removed, the leakage current when the reverse voltage is increased is reduced and the reverse withstand voltage is increased. It is considered a thing.

  Moreover, there was almost no difference in the magnitude of the leakage current between the Schottky barrier diodes of Examples 1 to 3. From this, since the damage 20ad received at the time of forming the insulating film 30 on the main surface side of the group III oxide layer 20a in Schottky contact with and in contact with the first electrode 40 in the opening 30w is removed, the opening If the thickness of the group III oxide layer 20a that is in Schottky contact with the first electrode 40 at 30w is less than 3 nm, there is almost no difference in the magnitude of the leakage current, and a high reverse withstand voltage can be obtained. I understood.

As shown in FIG. 9, between the Schottky barrier diodes of Examples 1 to 3, the forward current when a forward voltage is applied increases and the on-resistance decreases as the thickness of the group III oxide layer decreases. It became low. This is because a Ga ₂ O ₃ layer, which is a group III oxide layer, exists between the first electrode and the group III nitride layer, and therefore, at the Schottky interface between the first electrode and the group III oxide layer. This is presumably due to the change in the electron injection process and the high resistivity of the Ga ₂ O ₃ layer which is a group III oxide layer. Further, from the results of Examples 1 to 3, if the thickness of the group III oxide layer 20a that is in Schottky contact with and in contact with the first electrode 40 in the opening 30w is less than 3 nm, it is sufficiently low for practical use. It was found that on-resistance can be obtained.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Schottky barrier diode 10 Composite substrate 11 Support substrate 12 Bonding film | membrane 13, 80 Conductive support body 13d, 13sd, 20ad, 20d Damage 13s, 13t Group III nitride film 20 Group III nitride layer 20a Group III oxide layer 21 First n-type group III nitride layer 22 Second n-type group III nitride layer 30 Insulating film 40 First electrode 50 Pad electrode 60 Second electrode 70s Spacer metal layer 70p Pad metal layer 80b Junction metal layer 80e Conductive support electrode

Claims (12)

A first electrode, an insulating film having an opening, a group III oxide layer, and at least one group III nitride layer in this order;
The group III oxide layer is in Schottky contact with and in contact with the first electrode at the opening, and is in contact with the insulating film at other than the opening,
The Schottky barrier diode, wherein a thickness of a portion of the group III oxide layer in contact with the first electrode is smaller than a thickness of a portion of the group III oxide layer in contact with the insulating film.   2. The thickness of a portion of the group III oxide layer in contact with the first electrode is less than 3 nm, and a thickness of a portion of the group III oxide layer in contact with the insulating film is less than 10 nm. The Schottky barrier diode described.   3. The Schottky barrier diode according to claim 1, wherein the group III oxide layer and the group III nitride layer contain the same group III element.   The group III nitride layer includes a first n-type group III nitride layer and a second n-type group III nitride layer, and the carrier concentration of the first n-type group III nitride layer is 4. The Schottky barrier diode according to claim 1, wherein the Schottky barrier diode is higher than a carrier concentration of the second n-type group III nitride layer. 5.   The Schottky barrier diode according to any one of claims 1 to 4, further comprising a conductive support on the group III nitride layer side.   The Schottky barrier diode according to any one of claims 1 to 4, further comprising a conductive support on the first electrode side. Forming a Group III oxide layer on at least one Group III nitride layer;
Forming an insulating film on the group III oxide layer;
Forming an opening by removing a portion of the insulating film;
Reducing the thickness of the group III oxide layer under the opening by removing at least a portion of the group III oxide layer under the opening; and
Forming a first electrode in contact with the group III oxide layer under the opening by Schottky contact,
A method for manufacturing a Schottky barrier diode, wherein a thickness of a portion of the group III oxide layer in contact with the first electrode is smaller than a thickness of a portion of the group III oxide layer in contact with the insulating film.   The thickness of a portion of the group III oxide layer in contact with the first electrode is less than 3 nm, and a thickness of a portion of the group III oxide layer in contact with the insulating film is less than 10 nm. The manufacturing method of the Schottky barrier diode of description.   The method for producing a Schottky barrier diode according to claim 7 or 8, wherein the group III oxide layer and the group III nitride layer are the same in at least one group III element contained therein.   The group III nitride layer includes a first n-type group III nitride layer and a second n-type group III nitride layer, and the carrier concentration of the first n-type group III nitride layer is 10. The method for manufacturing a Schottky barrier diode according to claim 7, wherein the Schottky barrier diode is higher than a carrier concentration of the second n-type group III nitride layer. 11.   11. The method according to claim 7, further comprising a step of forming the group III nitride layer on a conductive support before the step of forming the group III oxide layer on the group III nitride layer. A method for manufacturing the Schottky barrier diode according to claim 1.   8. The method according to claim 7, further comprising a step of forming a conductive support on the first electrode side after the step of forming the first electrode in contact with the group III oxide layer in the opening by Schottky contact. Item 11. A method for manufacturing a Schottky barrier diode according to any one of Items 10.

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