JP2016004899A - Schottky barrier diode and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Schottky barrier diode which has high reverse breakdown voltage; and provide a Schottky barrier diode manufacturing method which achieves high efficiency and high yield.SOLUTION: A Schottky barrier diode 1 includes a semiconductor layer 20, a silicon nitride insulation film 30 having an opening 30w, a Schottky electrode 40s and a field plate electrode 40f, in which the silicon nitride insulation film 30 has a nitrogen atom concentration higher on the field plate electrode side than on the semiconductor layer side, and a lateral face 30s of the opening 30w of the silicon nitride insulation film 30 is formed in a manner such that a part 30p closer to the center of the opening is located on the semiconductor layer 30p side of the silicon nitride insulation film 30 and a part 30q farther from the center is located on the field plate electrode 40f side, and a thickness of the silicon nitride insulation film 30 at the farther part 30q is larger than a thickness of the silicon nitride insulation film 30 at the closer part 30p.

Description

  The present invention relates to a Schottky barrier diode and a manufacturing method thereof, and relates to a Schottky barrier diode having a high reverse withstand voltage including a Schottky electrode and a field plate electrode, and a Schottky via diode for manufacturing such a Schottky barrier diode with a high yield. It relates to the manufacturing method.

  A gallium nitride (GaN) semiconductor, which is one of group III nitride semiconductors, has a bandgap energy that is about three times larger than silicon (Si), a breakdown electric field strength that is about ten times higher, and a higher saturation electron velocity. It has various excellent characteristics such as. For this reason, group III nitride semiconductors such as GaN semiconductors can be expected to achieve both high breakdown voltage, which is difficult with conventional semiconductor materials, and low loss, that is, low on-resistance. Application to is expected.

For example, Japanese Patent Application Laid-Open No. 2009-077684 (Patent Document 1) has a semiconductor layer having a main surface and an opening formed on the main surface from the viewpoint of improving the reverse withstand voltage by the field plate structure. A nitride insulating film, a Schottky electrode formed in contact with the main surface inside the opening, and a field plate electrode connected to the Schottky electrode and formed to overlap the nitride insulating film And a Schottky barrier diode in which the hydrogen concentration in the nitride insulating film is less than 3.8 × 10 ²² cm ⁻³ .

  Japanese Patent Laying-Open No. 2013-258251 (Patent Document 2) is a Schottky barrier diode including a Schottky contact between a III-V semiconductor and a metal electrode from the viewpoint of further improving the breakdown voltage performance. A lower insulating film that is in contact with the surface and has an opening so that the semiconductor is exposed, and an upper insulating film that is in contact with the lower insulating film and has an enlarged opening so that the peripheral edge of the opening of the semiconductor and the lower insulating film is exposed And a field plate electrode including a metal electrode located in contact with the lower insulating film and the upper insulating film, and the lower insulating film from the upper insulating film side in the enlarged opening. Disclosed is a Schottky barrier diode that is inclined so that its thickness decreases toward the end of the opening.

JP 2009-077684 A JP2013-258251A

  The Schottky barrier diode disclosed in Japanese Patent Laying-Open No. 2009-077684 (Patent Document 1) forms an opening whose side surface is inclined by side etching by controlling the adhesion of the resist mask to the nitride insulating film. doing. For this reason, it is not easy to control the adhesion of the resist mask and the accompanying side etching, and the inclination of the side surface of the opening varies, which makes it difficult to increase the yield of the Schottky barrier diode. It was.

  The Schottky barrier diode disclosed in Japanese Patent Application Laid-Open No. 2013-258251 (Patent Document 2) is formed by tilting the side surface of the opening by forming two layers of insulating films having different types of lower insulating films and upper insulating films. And the like, and the yield of the Schottky barrier diode can be increased. However, since it is necessary to form two types of insulating films of different types, there is a problem that manufacturing efficiency is lowered and manufacturing cost is increased.

  Accordingly, an object of the present invention is to provide a Schottky barrier diode having a high reverse withstand voltage and a Schottky barrier diode manufacturing method for efficiently manufacturing such a Schottky barrier diode with a high yield by solving the above problems.

  A Schottky barrier diode according to an aspect of the present invention includes a semiconductor layer, a silicon nitride insulating film disposed on the semiconductor layer and having an opening, and a Schottky contact with the semiconductor layer disposed on the semiconductor layer inside the opening. And a field plate electrode connected to the Schottky electrode and disposed on a part of the silicon nitride insulating film. Here, the silicon nitride insulating film has a higher nitrogen atom concentration on the field plate electrode side than on the semiconductor layer side. The side surface of the opening of the silicon nitride insulating film has a portion near and far from the center of the opening, and the near portion is located on the semiconductor layer side of the silicon nitride insulating film and the far portion is a field plate of the silicon nitride insulating film. The silicon nitride insulating film is formed on the electrode side so that the thickness of the silicon nitride insulating film in the portion far from the thickness of the silicon nitride insulating film in the near portion is larger.

  A method for manufacturing a Schottky barrier diode according to another aspect of the present invention includes a step of forming a semiconductor layer, and nitridation having a higher nitrogen atom concentration on the semiconductor layer on the opposite side of the semiconductor layer than on the semiconductor layer A step of forming a silicon insulating film, and a side surface of the opening of the silicon nitride insulating film on the silicon nitride insulating film has a portion near and far from the center of the opening, and the close portion is a semiconductor of the silicon nitride insulating film The portion located on the layer side and far away is located on the opposite side of the semiconductor layer side of the silicon nitride insulating film, so that the thickness of the silicon nitride insulating film in the portion far from the thickness of the silicon nitride insulating film in the near portion is larger. Forming a portion, and forming a Schottky electrode in Schottky contact with the semiconductor layer on the semiconductor layer inside the opening, and connecting to the Schottky electrode on a part of the silicon nitride insulating film And forming a I over field plate electrode.

  According to the above aspect, it is possible to provide a Schottky barrier diode having a high reverse withstand voltage and a Schottky barrier diode manufacturing method for manufacturing such a Schottky barrier diode efficiently and with a high yield.

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 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.

<Description of Embodiment of the Present Invention>
A Schottky barrier diode 1 according to an embodiment of the present invention includes a semiconductor layer 20, a silicon nitride insulating film 30 disposed on the semiconductor layer 20 and having an opening 30w, and the semiconductor layer 20 inside the opening 30w. A Schottky electrode 40s disposed in Schottky contact with the semiconductor layer 20 and a field plate electrode 40f connected to the Schottky electrode 40s and disposed on a part of the silicon nitride insulating film 30 are included. Here, the silicon nitride insulating film 30 has a higher nitrogen atom concentration on the field plate electrode side 30q than on the semiconductor layer side 30p. The side surface 30s of the opening 30w of the silicon nitride insulating film 30 has a portion 30sn and a portion 30sf that are close to the center of the opening 30w, and the portion 30sn that is close is located on the semiconductor layer side 30p of the silicon nitride insulating film 30 and is far from it. The portion 30sf is located on the field plate electrode side 30q of the silicon nitride insulating film 30, and is formed such that the thickness of the silicon nitride insulating film 30 in the portion 30sf far from the thickness of the silicon nitride insulating film 30 in the near portion 30sn is larger. Yes.

  Since the Schottky barrier diode 1 of the present embodiment has a field plate structure with small variations, the reverse withstand voltage is high and the yield is also high.

  In the Schottky barrier diode 1 of the present embodiment, the side surface 30s of the opening 30w of the silicon nitride insulating film 30 can include two or more stepped surfaces and at least one of inclined surfaces. As a result, a Schottky barrier diode having a higher reverse breakdown voltage and a higher yield is obtained.

  In the Schottky barrier diode 1 of the present embodiment, the semiconductor layer 20 can be a group III nitride semiconductor layer. Thereby, a Schottky barrier diode having a very high reverse withstand voltage is obtained.

  The manufacturing method of the Schottky barrier diode 1, which is another embodiment of the present invention, includes the step of forming the semiconductor layer 20, and on the semiconductor layer 20, on the side opposite to the semiconductor layer side 30p rather than the semiconductor layer side 30p. The step of forming the silicon nitride insulating film 30 having a high nitrogen atom concentration, and the side 30s of the opening 30w of the silicon nitride insulating film 30 on the silicon nitride insulating film 30 are a portion 30sn and a portion 30sf far from the center of the opening 30w. The near portion 30 sn is located on the semiconductor layer side 30 p of the silicon nitride insulating film 30 and the far portion 30 sf is located on the opposite side of the semiconductor layer side 30 p of the silicon nitride insulating film 30, and the silicon nitride insulation in the near portion 30 sn A step of forming the opening 30w so that the thickness of the silicon nitride insulating film 30 in the portion 30sf far from the thickness of the film 30 is increased, and the opening 3 A Schottky electrode 40 s that is in Schottky contact with the semiconductor layer 20 is formed on the semiconductor layer 20 inside w, and a field plate electrode 40 f that is connected to the Schottky electrode 40 s is formed on a part of the silicon nitride insulating film 30. And a process.

  Since the manufacturing method of the Schottky barrier diode 1 of this embodiment can form a field plate structure with small variations, the Schottky barrier diode 1 having a high reverse withstand voltage can be obtained efficiently and with a high yield.

  In the method for manufacturing the Schottky barrier diode 1 of the present embodiment, in the step of forming the silicon nitride insulating film 30, the source nitrogen gas flow rate is increased stepwise or continuously by two or more by electron cyclone resonance sputtering. A silicon nitride insulating film 30 can be formed. As a result, a field plate structure with small variations can be formed, so that the Schottky barrier diode 1 having a high reverse withstand voltage can be obtained efficiently and with a high yield.

<Details of Embodiment of the Present Invention>
[Embodiment 1: Schottky barrier diode]
1 to 3, a Schottky barrier diode 1 according to the present embodiment includes a semiconductor layer 20, a silicon nitride insulating film 30 disposed on the semiconductor layer 20 and having an opening 30w, and the inside of the opening 30w. A Schottky electrode 40s disposed on the semiconductor layer 20 and in Schottky contact with the semiconductor layer 20, and a field plate electrode 40f connected to the Schottky electrode 40s and disposed on a part of the silicon nitride insulating film 30. Including. As described above, in the Schottky barrier diode 1 of the present embodiment, the field plate electrode 40f connected to the Schottky electrode 40s in Schottky contact with the semiconductor layer 20 inside the opening 30w of the silicon nitride insulating film 30 has silicon nitride insulation. Since the field plate structure is disposed on a part of the film 30 (the opening 30w and the vicinity thereof), the reverse withstand voltage is high.

  Here, the silicon nitride insulating film 30 has a higher nitrogen atom concentration on the field plate electrode side 30q than on the semiconductor layer side 30p. The silicon nitride insulating film 30 is not particularly limited, but from the viewpoint of forming a field plate structure having a high reverse withstand voltage and a small variation, two or more layers having different nitrogen atom concentrations are formed on the field plate from the semiconductor layer side 30p. It is preferable that the electrode side 30q is arranged so that a layer having a low nitrogen atom concentration is changed to a layer having a higher nitrogen atom concentration, and the nitrogen atom concentration is changed from the semiconductor layer side 30p to the field plate electrode side 30q. It is preferable to be configured to be continuously high.

  For example, the silicon nitride insulating film 30 of the Schottky barrier diode 1 shown in FIG. 1 is lower than the first layer 30a and the first layer 30a that are arranged in order from the semiconductor layer side 30p to the field plate electrode side 30q and have a lower nitrogen atom concentration. The second layer 30b has a high nitrogen atom concentration. The silicon nitride insulating film 30 of the second Schottky barrier diode 1 has nitrogen atoms lower than the first layer 30a and the first layer 30a, which are arranged in order from the semiconductor layer side 30p to the field plate electrode side 30q and have a lower nitrogen atom concentration. The second layer 30b has a higher concentration and the third layer 30c has a higher nitrogen atom concentration than the second layer 30b. The silicon nitride insulating film 30 of the Schottky barrier diode 1 shown in FIG. 3 is configured such that the nitrogen atom concentration continuously increases from the semiconductor layer side 30p to the field plate electrode side 30q.

  Here, the concentration of nitrogen atoms in the silicon nitride insulating film is measured by a secondary ion mass spectrometry (SIMS) method or the like.

  Such a silicon nitride insulating film 30 has a higher nitrogen atom concentration on the field plate electrode side 30q than on the semiconductor layer side 30p, and is more easily etched as the nitrogen atom concentration is higher. Also, an opening 30w is formed that extends toward the field plate electrode side 30q (that is, the field plate electrode side 30q has a larger area parallel to the main surface than the semiconductor layer side 30p).

  That is, the side surface 30 s of the opening 30 w of the silicon nitride insulating film 30 has a portion 30 sn near and a portion 30 sf far from the center of the opening 30 w, and the close portion 30 sn is located on the semiconductor layer side 30 p of the silicon nitride insulating film 30. The far portion 30sf is located on the field plate electrode side 30q of the silicon nitride insulating film 30 and is formed so that the thickness of the silicon nitride insulating film 30 in the portion 30sf farther than the thickness of the silicon nitride insulating film 30 in the near portion 30sn is larger. Has been. In such a field plate structure, the electric field concentration at the end of the Schottky electrode 40s is well relaxed and the variation in the structure during etching is small, so that the reverse withstand voltage is high and the yield is also high.

  Further, the side surface 30s of the opening 30w of the silicon nitride insulating film 30 is not particularly limited, but two or more stepped surfaces and inclined surfaces are formed from the viewpoint of forming a field plate structure with high reverse withstand voltage and small variation. It is preferable to include at least one surface.

  For example, the side surface 30s of the opening 30w of the silicon nitride insulating film 30 of the Schottky barrier diode 1 shown in FIG. 1 includes two stepped surfaces (two step surfaces and one terrace surface connecting them). The side surface 30s of the opening 30w of the silicon nitride insulating film 30 of the Schottky barrier diode 1 shown in FIG. 2 includes three stepped surfaces (three step surfaces and two terrace surfaces connecting them). Side surface 30s of opening 30w of silicon nitride insulating film 30 of Schottky barrier diode 1 shown in FIG. 3 includes a slope.

  The semiconductor layer 20 is not particularly limited, but is preferably a group III nitride semiconductor layer having a high dielectric breakdown field strength from the viewpoint of increasing the reverse breakdown voltage of the Schottky barrier diode 1.

  The semiconductor layer side electrode 40 composed of the Schottky electrode 40s and the field plate electrode 40f is not particularly limited as long as it is an electrode that is in Schottky contact with the semiconductor layer 20, but increases the barrier height with respect to the group III nitride semiconductor. From the viewpoint, nickel (Ni), gold (Au), platinum (Pt), palladium (Pd), cobalt (Co), copper (Cu), silver (Ag), tungsten (W), molybdenum (Mo), niobium ( Nb) and at least one metal selected from the group consisting of titanium tungsten (TiW) is preferable. For example, Ni electrode, Au electrode, Pd electrode, Pt electrode, Ni / Au electrode, Ni / W / Au electrode, etc. Is preferred.

  The Schottky barrier diode 1 of the present embodiment is not particularly limited, but can include the substrate 10 from the viewpoint of increasing mechanical strength. The substrate 10 is preferably a conductive substrate from the viewpoint of configuring the vertical structure Schottky barrier diode 1, for example, a metal substrate including a conductive group III nitride semiconductor substrate and a conductive group III nitride layer. A conductive semiconductor substrate including a conductive group III nitride layer is preferable.

  When the Schottky barrier diode 1 of the present embodiment includes a conductive substrate as the substrate 10, the vertical structure may include the substrate-side electrode 50 on the substrate 10 from the viewpoint of obtaining high breakdown voltage and large current density. it can. The substrate-side electrode 50 is preferably an ohmic electrode that is in ohmic contact with the substrate 10 from the viewpoint of reducing the on-resistance by reducing the contact resistance. Titanium (Ti), aluminum (Al), platinum (Pt), It is preferable to include at least one metal selected from the group consisting of molybdenum (Mo), niobium (Nb), tungsten (W), and titanium tungsten (TiW). For example, Ti electrode, Al electrode, Ti / Al electrode, Al / Mo / Au electrode, Ti / Al / Ti / Au electrode, Ti / Al / Mo / Au electrode and the like are preferable.

[Embodiment 2: Manufacturing Method of Schottky Barrier Diode]
1 to 4, in the manufacturing method of the Schottky barrier diode 1 of the first embodiment, the semiconductor layer side 30p is formed on the semiconductor layer 20 rather than the semiconductor layer side 30p on the semiconductor layer 20 in step S20. The side 30s of the opening 30w of the silicon nitride insulating film 30 is closer to the center of the opening in the step S30 of forming the silicon nitride insulating film 30 having a higher nitrogen atom concentration on the opposite side of the silicon nitride insulating film 30 It has a portion 30 sn and a distant portion 30 sf, a close portion 30 sn is located on the semiconductor layer side 30 p of the silicon nitride insulating film 30, and a distant portion 30 sf is located on the opposite side of the silicon nitride insulating film 30 on the semiconductor layer side 30 p and close A process for forming the opening 30w so that the thickness of the silicon nitride insulating film 30 in the portion 30sf far from the thickness of the silicon nitride insulating film 30 in the portion 30sn becomes larger. S50 and a Schottky electrode 40s that is in Schottky contact with the semiconductor layer 20 on the semiconductor layer 20 inside the opening 30w, and a field plate that is connected to the Schottky electrode 40s on a part of the silicon nitride insulating film 30 Forming the electrode 40f.

  Since the manufacturing method of the Schottky barrier diode 1 of this embodiment can form a field plate structure with small variations, the Schottky barrier diode 1 having a high reverse withstand voltage can be obtained efficiently and with a high yield.

  Although the manufacturing method of the Schottky barrier diode 1 of this embodiment is not particularly limited, it is preferable to include the following steps from the viewpoint of manufacturing efficiently and with high yield.

(Process for preparing the substrate)
1 to 4, the method for manufacturing the Schottky barrier diode 1 of the present embodiment preferably includes a step S <b> 10 for preparing the substrate 10. Thereby, the Schottky barrier diode 1 with high mechanical strength is obtained.

  The method for preparing the substrate 10 is not particularly limited when a conductive group III nitride semiconductor substrate is prepared as the substrate 10, but from the viewpoint of obtaining a high-quality conductive group III nitride semiconductor substrate, HVPE ( (Hydride vapor phase epitaxy) method, MBE (molecular beam vapor phase epitaxy) method, MOVPE (organic metal vapor phase epitaxy) method, vapor phase method such as sublimation method, liquid phase method such as flux method, high nitrogen pressure solution method, etc. preferable.

(Process for forming a semiconductor layer)
1 to 4, the method for manufacturing the Schottky barrier diode 1 of the present embodiment includes a step S <b> 20 of forming the semiconductor layer 20 on the substrate 10. Thereby, the Schottky barrier diode 1 is obtained. The semiconductor layer 20 is preferably a group III nitride semiconductor layer from the viewpoint of increasing the reverse withstand voltage. When forming the group III nitride semiconductor layer, the semiconductor layer 20 is formed from a gas phase such as MOVPE, MBE, HVPE, and sublimation from the viewpoint of forming a high-quality group III nitride semiconductor layer. A liquid phase method such as a method, a flux method or a high nitrogen pressure solution method is preferable.

(Process of forming a silicon nitride insulating film)
1 to 4, in the manufacturing method of the Schottky barrier diode 1 of the present embodiment, the nitrogen atom concentration is higher on the semiconductor layer 20 on the opposite side of the semiconductor layer side 30p than on the semiconductor layer side 30p. A step S30 of forming a high silicon nitride insulating film 30 is included. Thereby, a field plate structure having a high reverse withstand voltage and small variations can be formed.

  The method for forming the silicon nitride insulating film 30 having a higher nitrogen atom concentration on the opposite side of the semiconductor layer side 30p than on the semiconductor layer side 30p is not particularly limited, but the film can be easily adjusted to have a high quality. From the viewpoint that can be formed, the electron cyclone resonance sputtering method is preferable.

  The electron cyclone resonance (ECR) sputtering method uses a plasma (ECR plasma) generated by ECR, applies a voltage to a target arranged around the plasma, and causes the plasma to be accelerated and incident on the target. It refers to a method of forming a thin film by causing a phenomenon and depositing released target particles on a nearby substrate. The ECR plasma is generated by introducing a gas into the vacuum vessel, maintaining the pressure at about 0.01 Pa to 0.2 Pa, and applying a magnetic field of about 50 mT to 100 mT and a microwave of about 1 GHz to 5 GHz. Can do. Discharge at a pressure 1 to 2 digits lower than that of general plasma is possible, and a thin film can be formed on a substrate under low energy and high density ion irradiation of about 10 to 30 eV. Such ion irradiation can form a dense and smooth high-quality thin film with low temperature and low damage, and can also form oxides and nitrides without heating by utilizing the reactivity of oxygen gas and nitrogen gas.

  In the method of forming the silicon nitride insulating film 30 on the semiconductor layer 20 by the ECR sputtering method, the silicon nitride particles emitted by accelerating incidence of nitrogen plasma generated in the raw material nitrogen gas by ECR to the solid silicon target are made into the semiconductor. It is a method of depositing on the layer 20.

  The process of forming the silicon nitride insulating film 30 having a higher nitrogen atom concentration on the opposite side of the semiconductor layer side 30p than on the semiconductor layer side 30p is not particularly limited, but efficiently forms a high-quality silicon nitride insulating film. From the viewpoint, it is preferable to form the silicon nitride insulating film 30 while increasing the raw material nitrogen gas flow rate stepwise or continuously by two or more.

  For example, referring to FIG. 1, by increasing the raw material nitrogen gas flow rate stepwise in two steps, the first layer 30a having a low nitrogen atom concentration disposed on the opposite side from the semiconductor layer side 30p, A silicon nitride insulating film 30 constituted by the second layer 30b having a higher nitrogen atom concentration than the first layer 30a is obtained. Referring to FIG. 2, by increasing the raw material nitrogen gas flow rate in three stages, a first layer 30a having a low nitrogen atom concentration, which is disposed from the semiconductor layer side 30p to the opposite side, and a first layer A silicon nitride insulating film 30 constituted by the second layer 30b having a higher nitrogen atom concentration than 30a and the third layer 30c having a higher nitrogen atom concentration than the second layer is obtained. Referring to FIG. 3, by continuously increasing the raw material nitrogen gas flow rate, silicon nitride insulating film 30 in which the nitrogen atom concentration continuously increases in the thickness direction from semiconductor layer side 30p to the opposite side is obtained. .

(Process of forming substrate side electrode)
1 to 4, the manufacturing method of the Schottky barrier diode 1 of the present embodiment includes a step S <b> 40 of forming the substrate-side electrode 50 on the substrate 10 when the substrate 10 is a conductive substrate. Is preferred. Thereby, the vertical Schottky barrier diode 1 can be configured.

  The method for forming the substrate-side electrode 50 is not particularly limited, and examples include electron beam (EB) vapor deposition, resistance heating vapor deposition, and sputtering.

(Process for forming an opening in a silicon nitride insulating film)
1 to 4, the method for manufacturing the Schottky barrier diode 1 of the present embodiment includes a step S <b> 50 of forming an opening 30 w in the silicon nitride insulating film 30. Here, from the viewpoint of increasing the reverse withstand voltage of the Schottky barrier diode 1, the opening 30 w has a portion 30 sf far from a portion 30 sn that is closer to the side 30 s of the opening 30 w of the silicon nitride insulating film 30 than the center of the opening 30 w. The near portion 30 sn is located on the semiconductor layer side 30 p of the silicon nitride insulating film 30, and the far portion 30 sn is located on the opposite side of the semiconductor layer side 30 p of the silicon nitride insulating film 30, and the silicon nitride in the near portion 30 sn The silicon nitride insulating film 30 is formed so that the thickness in the portion 30 sf far from the thickness of the insulating film 30 is large.

  The method for forming the opening 30w in the silicon nitride insulating film 30 is not particularly limited, but a resist pattern is formed on the silicon nitride insulating film 30 by photolithography from the viewpoint of forming the opening 30w in the desired form. A method of removing the resist pattern after etching is preferable. Etching is not particularly limited, but wet etching with hydrofluoric acid, buffered hydrofluoric acid, or the like is preferable from the viewpoint of forming the opening 30w in the desired form.

  For example, referring to FIG. 1, when silicon nitride insulating film 30 composed of first layer 30a having a low nitrogen atom concentration and second layer 30b having a higher nitrogen atom concentration than first layer 30a is wet etched. Since the etching rate of the second layer 30b is higher than that of the first layer 30a, the opening of the second layer 30b is wider than the opening of the first layer 30a, and the side surface 30s of the opening 30w of the silicon nitride insulating film 30 Includes two stepped surfaces (two step surfaces and one terrace surface connecting them).

  Referring to FIG. 2, a first layer 30a having a low nitrogen atom concentration, a second layer 30b having a higher nitrogen atom concentration than the first layer 30a, and a third layer 30c having a higher nitrogen atom concentration than the second layer, When the silicon nitride insulating film 30 composed of and is wet-etched, the second layer 30b has a higher etching rate than the first layer 30a, and the third layer 30c has a higher etching rate than the second layer 30b. The opening of the second layer 30b is wider than the opening of the first layer 30a, the opening of the third layer 30c is wider than the opening of the second layer 30b, and the side surface 30s of the opening 30w of the silicon nitride insulating film 30 is It includes three stepped surfaces (three step surfaces and two terrace surfaces connecting them).

  Referring to FIG. 3, when the silicon nitride insulating film 30 whose nitrogen atom concentration is continuously increased in the thickness direction from the semiconductor layer side 30 p to the opposite side is wet-etched, the silicon nitride insulating film 30 is formed on the semiconductor layer side 30 p. Since the etching rate on the side opposite to the semiconductor layer side 30p is higher than that on the semiconductor layer side 30p, the opening on the side opposite to the semiconductor layer side 30p is wider than the opening on the semiconductor layer side 30p. The side surface 30s of the opening 30w includes a slope.

(Step of forming Schottky electrode and field plate electrode)
1 to 4, the manufacturing method of the Schottky barrier diode 1 according to the present embodiment is a step S60 of forming the Schottky electrode 40s and the field plate electrode 40f, specifically, the opening of the silicon nitride insulating film 30. A Schottky electrode 40s that is in Schottky contact with the semiconductor layer 20 is formed on the semiconductor layer 20 inside the portion 30w, and a field plate electrode 40f that is connected to the Schottky electrode 40s is formed on a part of the silicon nitride insulating film 30. Step S60 to include. Through this process, the Schottky barrier diode 1 having a high reverse withstand voltage is obtained.

  The method for forming the Schottky electrode 40s and the field plate electrode 40f is not particularly limited. From the viewpoint of efficiently forming a high-quality electrode, the opening 30w of the silicon nitride insulating film 30 and the vicinity thereof are formed by photolithography. A resist pattern having an opening is formed on the semiconductor layer 20 and the semiconductor layer side electrode 40 is formed on the semiconductor layer 20 and the silicon nitride insulating film 30 in the opening of the resist pattern by EB vapor deposition, resistance heating vapor deposition, sputtering, or the like. There is a lift-off method in which the resist pattern is lifted off after the formation.

  From the same point of view, the semiconductor layer side electrode 40 is formed on the entire main surface including the opening 30w of the silicon nitride insulating film 30 by EB vapor deposition, resistance heating vapor deposition, sputtering, etc., and the opening 30w and its vicinity An etching method may be mentioned in which after forming a resist pattern that protects the regions where the Schottky electrode 40s and the field plate electrode 40f are to be formed, the semiconductor layer side electrodes other than the protected regions are removed by wet etching, and further the resist is removed. .

  In this manner, the Schottky electrode 40 s in Schottky contact with the semiconductor layer 20 is formed on the semiconductor layer 20 inside the opening 30 w of the silicon nitride insulating film 30, and the side surface 30 s of the opening 30 w of the silicon nitride insulating film 30. And the field plate electrode 40f is formed on the vicinity thereof. Here, the semiconductor layer side electrode 40 includes the Schottky electrode 40s and the field plate electrode 40f connected thereto.

(Example 1)
1. Preparation of Substrate With reference to FIGS. 1 and 4, an n-type GaN free-standing substrate having a diameter of 50 mm, a thickness of 400 μm, and a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ prepared by HVPE was prepared as a substrate 10. .

2. Formation of Semiconductor Layer Next, an n-type GaN layer having a thickness of 5 μm and a carrier concentration of 1 × 10 ¹⁶ cm ⁻³ was formed as the semiconductor layer 20 on the substrate 10 by the MOVPE method.

3. Formation of Silicon Nitride Insulating Film Next, a silicon nitride insulating film 30 having a thickness of 500 nm was formed on the semiconductor layer 20 by ECR sputtering. When forming the silicon nitride insulating film 30, the flow rate of the raw material nitrogen gas was initially 10 sccm and then 50 sccm. Thus, the silicon nitride insulating film constituted by the first layer 30a having a thickness of 250 nm and a nitrogen atom concentration of 10 atomic% and the second layer 30b having a thickness of 250 nm and a nitrogen atom concentration of 50 atomic%. 30 was obtained. Here, the nitrogen atom concentration in the silicon nitride insulating film 30 was measured by the SIMS (secondary ion mass spectrometry) method.

4). Next, an ohmic electrode composed of a Ti layer having a thickness of 10 nm and an Al layer having a thickness of 200 nm is formed as the substrate side electrode 50 on the substrate 10 by the EB vapor deposition method. did.

5. Step of forming an opening in the silicon nitride insulating film Next, a resist pattern is formed on the silicon nitride insulating film 30 by photolithography, etched using buffered hydrofluoric acid (BHF110 manufactured by Daikin), and then the resist pattern is removed. Thus, the opening 30w of the silicon nitride insulating film 30 was formed. The width of the obtained opening 30w was 800 μm × 800 μm square at the first layer 30a portion where the semiconductor layer 20 was exposed, and 820 μm × 820 μm square at the second layer 30b portion.

6). Formation of Schottky Electrode and Field Plate Electrode Next, a resist pattern having an opening in an area of 850 μm × 850 μm square from the periphery of the opening 30w of the silicon nitride insulating film 30 to 50 μm is formed by photolithography. On the semiconductor layer 20 and the silicon nitride insulating film 30 in the opening of the resist pattern, a semiconductor layer side electrode 40 composed of a 50 nm thick Ni layer and a 300 nm thick Au layer is formed by EB vapor deposition. After forming, the Schottky electrode 40s and the field plate electrode 40f were formed by a lift-off method of lifting off the resist pattern.

7). Characteristic Evaluation 100 Schottky barrier diodes having the same structure were manufactured by the same procedure. The yield rate was 90% when the reverse breakdown voltage was 600 V or higher. Moreover, the average reverse withstand voltage in non-defective products was 650V.

(Example 2)
1. Preparation of Substrate With reference to FIGS. 2 and 4, an n-type GaN free-standing substrate similar to that of Example 1 was prepared as the substrate 10.

2. Formation of Semiconductor Layer Next, the same n-type GaN layer as in Example 1 was formed on the substrate 10 as the semiconductor layer 20.

3. Formation of Silicon Nitride Insulating Film Next, a silicon nitride insulating film 30 having a thickness of 500 nm was formed on the semiconductor layer 20 by ECR sputtering. When forming the silicon nitride insulating film 30, the flow rate of the raw material nitrogen gas was initially 10 sccm, then 25 sccm, and further 50 sccm. Thus, the first layer 30a having a thickness of 167 nm and a nitrogen atom concentration of 10 atomic%, the second layer 30b having a thickness of 166 nm and a nitrogen atom concentration of 25 atomic%, and a nitrogen atom concentration of 167 nm and a nitrogen atom concentration of 50 A silicon nitride insulating film 30 composed of the third layer 30c of atomic% was obtained.

4). Formation of Substrate Side Electrode Next, the same ohmic electrode as in Example 1 was formed on the substrate 10 as the substrate side electrode 50.

5. Step of Forming Opening in Silicon Nitride Insulating Film Next, the opening 30 w was formed in the silicon nitride insulating film 30 in the same manner as in Example 1. The width of the obtained opening 30w is 800 μm × 800 μm square in the first layer 30a portion where the semiconductor layer 20 is exposed, 810 μm × 810 μm square in the second layer 30b portion, and 820 μm in the third layer 30c portion. × 820 μm square.

6). Formation of Schottky Electrode and Field Plate Electrode Next, a Schottky electrode 40s and a field plate electrode 40f were formed in the same manner as in Example 1.

7). Characteristic Evaluation 100 Schottky barrier diodes having the same structure were manufactured by the same procedure. The yield rate was 90% when the reverse breakdown voltage was 600 V or higher. Moreover, the average reverse withstand voltage in non-defective products was 650V.

(Example 3)
1. Preparation of Substrate With reference to FIGS. 3 and 4, an n-type GaN free-standing substrate similar to that of Example 1 was prepared as the substrate 10.

2. Formation of Semiconductor Layer Next, the same n-type GaN layer as in Example 1 was formed on the substrate 10 as the semiconductor layer 20.

3. Formation of Silicon Nitride Insulating Film Next, a silicon nitride insulating film 30 having a thickness of 500 nm was formed on the semiconductor layer 20 by ECR sputtering. When the silicon nitride insulating film 30 was formed, the flow rate of the source nitrogen gas was continuously changed from the first 10 sccm to the last 50 sccm. Thus, a silicon nitride insulating film 30 was obtained in which the nitrogen atom concentration increased from 10 atomic% to 50 atomic% in the thickness direction from the semiconductor layer side 30p to the opposite side of the semiconductor layer side 30p.

4). Formation of Substrate Side Electrode Next, the same ohmic electrode as in Example 1 was formed on the substrate 10 as the substrate side electrode 50.

5. Step of Forming Opening in Silicon Nitride Insulating Film Next, the opening 30 w was formed in the silicon nitride insulating film 30 in the same manner as in Example 1. The width of the obtained opening 30w was 800 μm × 800 μm square on the semiconductor layer side 30p where the semiconductor layer 20 was exposed, and 820 μm × 820 μm square on the opposite side of the semiconductor layer side 30p.

6). Formation of Schottky Electrode and Field Plate Electrode Next, a Schottky electrode 40s and a field plate electrode 40f were formed in the same manner as in Example 1.

7). Characteristic Evaluation 100 Schottky barrier diodes having the same structure were manufactured by the same procedure. The yield rate was 90% when the reverse breakdown voltage was 600 V or higher. Moreover, the average reverse withstand voltage in non-defective products was 650V.

Example 4
In the formation of the Schottky electrode and the field plate electrode, the entire main surface including the opening 30w of the silicon nitride insulating film 30 is composed of a Ni layer having a thickness of 50 nm and an Au layer having a thickness of 300 nm by EB vapor deposition. The semiconductor layer side electrode 40 is formed, and the opening 30w of the silicon nitride insulating film 30 and the region for forming the 850 μm × 850 μm square Schottky electrode 40s and the field plate electrode 40f from the periphery of the opening 30w to 50 μm are protected. After the resist pattern to be formed is formed, the semiconductor layer side electrode other than the protected region is removed by wet etching, and the Schottky electrode 40s and the field plate electrode 40f are formed by an etching method for removing the resist. A shot having the same structure as in Example 1. The over barrier diode was produced 100 pieces. The yield rate was 90% when the reverse breakdown voltage was 600 V or higher. Moreover, the average reverse withstand voltage in non-defective products was 650V.

(Example 5)
In the formation of the Schottky electrode and the field plate electrode, the entire main surface including the opening 30w of the silicon nitride insulating film 30 is composed of a Ni layer having a thickness of 50 nm and an Au layer having a thickness of 300 nm by EB vapor deposition. The semiconductor layer side electrode 40 is formed, and the opening 30w of the silicon nitride insulating film 30 and the region for forming the 850 μm × 850 μm square Schottky electrode 40s and the field plate electrode 40f from the periphery of the opening 30w to 50 μm are protected. After the resist pattern to be formed is formed, the semiconductor layer side electrode other than the protected region is removed by wet etching, and the Schottky electrode 40s and the field plate electrode 40f are formed by an etching method for removing the resist. Similar to Example 2, shots with similar structure The over barrier diode was produced 100 pieces. The yield rate was 90% when the reverse breakdown voltage was 600 V or higher. Moreover, the average reverse withstand voltage in non-defective products was 650V.

(Example 6)
In the formation of the Schottky electrode and the field plate electrode, the entire main surface including the opening 30w of the silicon nitride insulating film 30 is composed of a Ni layer having a thickness of 50 nm and an Au layer having a thickness of 300 nm by EB vapor deposition. The semiconductor layer side electrode 40 is formed, and the opening 30w of the silicon nitride insulating film 30 and the region for forming the 850 μm × 850 μm square Schottky electrode 40s and the field plate electrode 40f from the periphery of the opening 30w to 50 μm are protected. After the resist pattern to be formed is formed, the semiconductor layer side electrode other than the protected region is removed by wet etching, and the Schottky electrode 40s and the field plate electrode 40f are formed by an etching method for removing the resist. Similar to Example 3, shots with similar structure The over barrier diode was produced 100 pieces. The yield rate was 90% when the reverse breakdown voltage was 600 V or higher. Moreover, the average reverse withstand voltage in non-defective products was 650V.

(Comparative Example 1)
1. Preparation of substrate As a substrate, an n-type GaN free-standing substrate similar to that of Example 1 was prepared.

2. Formation of Semiconductor Layer Next, an n-type GaN layer similar to that of Example 1 was formed as a semiconductor layer on the substrate.

3. Formation of Silicon Nitride Insulating Film Next, a silicon nitride insulating film having a thickness of 500 nm was formed on the semiconductor layer by ECR sputtering. When forming the silicon nitride insulating film, the flow rate of the raw material nitrogen gas was kept constant at 10 sccm. Thus, a silicon nitride insulating film having a constant nitrogen atom concentration of 10 atomic% in the thickness direction from the semiconductor layer side to the opposite side of the semiconductor layer side was obtained.

4). Formation of Substrate Side Electrode Next, the same ohmic electrode as in Example 1 was formed on the above substrate as the substrate side electrode.

5. Step of forming openings in silicon nitride insulating film Next, openings were formed in the silicon nitride insulating film in the same manner as in Example 1. The width of the obtained opening was 800 μm × 800 μm square where the semiconductor layer was exposed.

6). Formation of Schottky Electrode and Field Plate Electrode Next, a Schottky electrode and a field plate electrode were formed in the same manner as in Example 1.

7). Characteristic Evaluation 100 Schottky barrier diodes having the same structure were manufactured by the same procedure. The yield rate was 50% when the reverse breakdown voltage was 600 V or higher. Moreover, the average reverse withstand voltage in non-defective products was 650V.

  Comparing Comparative Example 1 and Examples 1 to 3, compared with the conventional Schottky barrier diode, the yield rate of each of Examples 1 to 3 Schottky barrier diodes shown in FIGS. As the value increased, the average reverse withstand voltage in non-defective products also increased.

  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 Board | substrate 20 Semiconductor layer 30 Silicon nitride insulating film 30a 1st layer 30b 2nd layer 30c 3rd layer 30p Semiconductor layer side 30q Field plate electrode side 30s Side surface 30sf Far part 30sn Near part 30w Opening part 40 Semiconductor layer Side electrode 40f Field plate electrode 40s Schottky electrode 50 Substrate side electrode S10 Step of preparing substrate S20 Step of forming semiconductor layer S30 Step of forming silicon nitride insulating film S40 Step of forming substrate side electrode S50 Silicon nitride insulating film Step S60 for Forming Openings Step for Forming Schottky Electrode and Field Plate Electrode (Semiconductor Layer Side Electrode)

Claims (5)

A semiconductor layer, a silicon nitride insulating film disposed on the semiconductor layer and having an opening, a Schottky electrode disposed on the semiconductor layer inside the opening and in Schottky contact with the semiconductor layer, and the Schottky A field plate electrode connected to the electrode and disposed on a part of the silicon nitride insulating film,
The silicon nitride insulating film has a higher nitrogen atom concentration on the field plate electrode side than on the semiconductor layer side,
The side surface of the opening of the silicon nitride insulating film has a portion near and far from the center of the opening, and the close portion is located on the semiconductor layer side of the silicon nitride insulating film and the far portion is The Schottky is located on the field plate electrode side of the silicon nitride insulating film and is formed such that the thickness of the silicon nitride insulating film in the far portion is larger than the thickness of the silicon nitride insulating film in the near portion. Barrier diode.   2. The Schottky barrier diode according to claim 1, wherein a side surface of the opening of the silicon nitride insulating film includes at least one of two or more stepped surfaces and a slope.   The Schottky barrier diode according to claim 1, wherein the semiconductor layer is a group III nitride semiconductor layer. Forming a semiconductor layer;
Forming a silicon nitride insulating film having a higher nitrogen atom concentration on the semiconductor layer on the opposite side of the semiconductor layer than on the semiconductor layer; and
The side surface of the opening of the silicon nitride insulating film has a portion near and far from the center of the opening in the silicon nitride insulating film, and the close portion is on the semiconductor layer side of the silicon nitride insulating film. The located and far portion is located on the opposite side of the silicon nitride insulating film to the semiconductor layer side, and the thickness of the silicon nitride insulating film in the far portion is larger than the thickness of the silicon nitride insulating film in the near portion. Forming the opening,
A Schottky electrode that is in Schottky contact with the semiconductor layer is formed on the semiconductor layer inside the opening, and a field plate electrode that is connected to the Schottky electrode is formed on a part of the silicon nitride insulating film. And a Schottky barrier diode manufacturing method.   5. The shot according to claim 4, wherein in the step of forming the silicon nitride insulating film, the silicon nitride insulating film is formed while increasing a raw material nitrogen gas flow rate stepwise or continuously by two or more by an electron cyclone resonance sputtering method. Manufacturing method of key barrier diode.

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