JP2009200110A - Diamond electronic element, and manufacturing method of diamond electronic element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diamond electronic element capable of reducing loss and preventing a Schottky electrode layer from peeling, and a manufacturing method of such a diamond electronic element. <P>SOLUTION: The diamond electronic element 1 has an oxide insulating layer 12 disposed on one surface side of a drift layer 23 so as to enclose a circumference of the Schottky electrode layer 15. Consequently, graphiting of a surface of the drift layer 23 is suppressed even during use in a high-temperature environment, and the loss is reduced. Further, in the diamond electronic element 1, the adhesiveness between the drift layer 23 and Schottky electrode layer 15 is reinforced by compensated for by being covered with the oxide insulating layer 12 tightly bonded to the surface of the drift layer 23 through the intervention of an intermediate layer 13 made of Ti with excellent reactivity and an electrode pad layer 16 tightly bonded to a surface of the oxide insulating layer 12. Consequently, the Schottky electrode layer 15 is excellently prevented from peeling. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a diamond electronic device using a Schottky junction and a method for manufacturing the diamond electronic device.

Electronic devices such as diodes and transistors using Schottky junctions are expected to be applied as high-power electronic devices. In recent years, development of an electronic device using diamond that has a larger band gap than conventional silicon and has high thermal conductivity and heat resistance has been promoted (see, for example, Non-Patent Document 1). Diamond electronic devices have made further progress due to advances in vapor phase synthesis technology and doping technology.
H. Shiomi et al. Diamond Films and Technology. Vol. 6, No. 2 (1996), p95-120

  Diamond is chemically very stable and has the property that the reaction does not proceed easily between metals and non-metals. However, from the viewpoint of manufacturing a diamond electronic device, this property is a factor that decreases the adhesion between diamond and the Schottky electrode layer. For example, in the case of bonding between an oxide insulating layer and silicon, the reaction proceeds in the oxidation process, and a strong bond of silicon oxide is formed. However, in the case of diamond, oxidation of the outermost surface occurs, but the bond between oxygen and carbon is prioritized and the bond of silicon oxide does not proceed, and peeling frequently occurs.

  On the other hand, titanium is known as a material suitable for ohmic bonding. However, titanium has a property that adhesion is not sufficient with respect to a metal having good Schottky characteristics such as platinum. For these reasons, in the conventional diamond electronic device, when making contact with the Schottky electrode layer by wire bonding, the Schottky electrode layer is easily peeled off, which makes it difficult to mount packaging.

  Further, the outermost surface of diamond may be transformed into a graphite layer under a high temperature environment. For example, when Schottky characteristics are measured after heating a diamond electronic device to 500 ° C. or higher in a vacuum, it is confirmed that the reverse current increases through the outermost graphite layer. Therefore, the reduction of the loss of the diamond electronic element has been a problem.

  The present invention has been made in order to solve the above-mentioned problems, and a diamond electronic device capable of reducing loss and preventing peeling of a Schottky electrode layer, and a method for manufacturing such a diamond electronic device. The purpose is to provide.

  In order to solve the above problems, a diamond electronic device according to the present invention includes an oxide insulating layer formed on one side of a diamond substrate, and a Schottky electrode layer formed in a contact hole provided in the oxide insulating layer. And an electrode pad layer formed from the surface of the Schottky electrode layer to the surface of the oxide insulating layer, and an intermediate layer made of titanium is formed at least partially between the diamond substrate and the oxide insulating layer. It is characterized by having.

  In this diamond electronic device, since an oxide insulating layer is disposed around the Schottky electrode layer on one side of the diamond substrate, graphitization of the surface of the diamond substrate is suppressed even when used in a high temperature environment. . Therefore, the phenomenon in which the reverse current increases through the outermost graphite layer can be suppressed, and the loss can be reduced. In this diamond electronic device, an intermediate layer is interposed between the diamond substrate and the oxide insulating layer, and the Schottky electrode layer formed in the contact hole of the oxide insulating layer extends to the surface of the oxide insulating layer. Covered by an extending electrode pad layer. That is, in this diamond electronic device, it is covered with an oxide insulating layer that is firmly bonded to the diamond substrate through the presence of a reactive intermediate layer, and an electrode pad layer that is bonded to the surface of the oxide insulating layer. As a result, adhesion between the diamond substrate and the Schottky electrode layer is supplemented, and peeling of the Schottky electrode layer can be suitably prevented.

  Moreover, it is preferable that the distance of the area | region in which the intermediate | middle layer is not formed between a diamond substrate and an oxide insulating layer is 200 micrometers or less. In this way, the internal stress and thermal stress of the oxide insulating layer in the portion that is not fixed to the intermediate layer are alleviated, and the oxide insulating layer can be prevented from peeling from the diamond substrate.

  Further, the distance from the side surface of the diamond substrate to the edge of the intermediate layer is preferably 100 μm or less. Separation of the oxide insulating layer often occurs from the side surface of the diamond substrate. Therefore, the oxide insulating layer can be effectively prevented from peeling from the diamond substrate by extending the edge of the intermediate layer to the vicinity of the side surface of the diamond substrate.

  In addition, the thickness of the oxide insulating layer is preferably 1 μm or more. When the thickness of the oxide insulating layer is not sufficient, the oxide insulating layer is destroyed even if the withstand voltage of the Schottky voltage is improved. Therefore, by setting the thickness of the oxide insulating layer to 1 μm or more, it is possible to obtain a sufficient withstand voltage with Schottky characteristics.

  Further, the electrode pad layer preferably has a field plate portion on the surface of the oxide insulating layer, and the intermediate layer preferably extends inside the oxide insulating layer corresponding to the formation region of the field plate portion. . When the field plate portion is formed in the electrode pad layer, the electric field generated at the end on the Schottky electrode layer side is weakened, while the electric field concentration is likely to occur at the end of the field plate portion. Therefore, by forming the intermediate layer corresponding to the formation region of the field plate portion, the electric field concentration can be suppressed, and the dielectric breakdown in the oxide insulating layer can be prevented.

  Moreover, it is preferable that a marking portion made of any one heavy metal of Hf, Ta, W, Re, Ir, Pt, and Au is formed on the surface of the intermediate layer. In the production of diamond electronic elements, for example, when patterning is performed with an electron beam exposure machine, the oxide insulating layer may be charged up (a phenomenon in which the insulating layer becomes charged and cannot be measured). Therefore, by forming the marking portion on the surface of the intermediate layer, high contrast is maintained even when there is a charge-up, and the patterning accuracy can be maintained.

  The method for manufacturing a diamond electronic device according to the present invention includes a step of forming an intermediate layer made of titanium on one surface side of the diamond substrate, and a step of forming an oxide insulating layer on the one surface side of the diamond substrate so as to cover the intermediate layer. A step of forming a contact hole in the oxide insulating layer by wet etching using a predetermined mask, a step of forming a Schottky electrode layer in the contact hole, and a surface of the oxide insulating layer from the surface of the Schottky electrode layer. And a step of forming an electrode pad layer.

  In this method for manufacturing a diamond electronic device, an intermediate layer and an oxide insulating layer are formed on one side of a diamond substrate, and then a contact hole is formed at a desired position to form a Schottky electrode layer. Therefore, it is possible to easily pattern the Schottky electrode layer that easily peels from the diamond substrate. In addition, since wet etching is used in forming the contact hole, damage to the surface of the diamond substrate can be prevented and good Schottky characteristics can be obtained.

  According to the present invention, it is possible to reduce the loss and prevent the Schottky electrode layer from peeling off.

  Hereinafter, preferred embodiments of a diamond electronic device and a method for manufacturing the diamond electronic device according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an embodiment of a diamond electronic device according to the present invention. The diamond electronic device 1 shown in the figure is a so-called Schottky diode, and includes a diamond substrate 10, an ohmic electrode layer 11, an oxide insulating layer 12, an intermediate layer 13, a marking portion 14, and a Schottky electrode layer. 15 and an electrode pad layer 16.

  The diamond substrate 10 includes a base layer 21, a bulk layer 22, and a drift layer 23. The base layer 21 is a high-pressure synthetic substrate made of, for example, a diamond single crystal. The thickness of the base layer 21 is 10 μm. The bulk layer 22 and the drift layer 23 are sequentially formed on one surface side of the base layer 21 by, for example, a vapor phase synthesis method using a microwave plasma CVD apparatus.

The bulk layer 22 is made of, for example, a diamond semiconductor whose conductivity type is P ⁺ type, and is formed in the same shape as the base layer 21. The thickness of the bulk layer 22 is 1 μm, for example. The drift layer 23 is made of, for example, a diamond semiconductor having a conductivity type of P −, and is formed in a central portion on one surface side of the bulk layer 22. The thickness of the drift layer 23 is, for example, 10 μm. A contact hole (not shown) for ohmic junction is formed at a predetermined position of the drift layer 23.

  The ohmic electrode layer 11 has, for example, a three-layer structure of Ti / Pt / Au. The ohmic electrode layer 11 is formed in the contact hole of the drift layer 23 and extends to the surface of the bulk layer 22 that is not covered by the drift layer 23.

The oxide insulating layer 12 is made of, for example, SiO ₂ and is sequentially formed on one surface side of the base layer 21 by, for example, a vapor phase synthesis method using a microwave plasma CVD apparatus. A contact hole 24 for Schottky junction is formed in the center of the oxide insulating layer 12. The thickness of the oxide insulating layer 12 is, for example, 1 μm, and the withstand voltage of Schottky characteristics is improved.

  The intermediate layer 13 is made of titanium, for example, and is formed between the drift layer 23 and the oxide insulating layer 12. The thickness of the intermediate layer 13 is, for example, 200 mm. The intermediate layer 13 is disposed inside the oxide insulating layer 12 so as to correspond to a formation region of a field plate portion 32 (described later) of the electrode pad layer 16. The edge of the intermediate layer 13 is not exposed on the side surface 12 a of the oxide insulating layer 12 and the side surface 23 a of the drift layer 23.

  A distance L1 between the drift layer 23 and the oxide insulating layer 12 where the intermediate layer 13 is not formed is, for example, 200 μm or less. The distance L2 from the side surface 23a of the drift layer 23 to the edge of the intermediate layer 13 is 100 μm or less.

  The marking portion 14 is made of any one heavy metal of Hf, Ta, W, Re, Ir, Pt, and Au. In the marking unit 14 of the present embodiment, for example, Au is selected. The marking portion 14 is arranged at a position near the side surface 12 a of the oxide insulating layer 12 on the surface of the intermediate layer 13.

  The Schottky electrode layer 15 is made of, for example, Pt, and is formed in contact with the surface of the drift layer 23 at the bottom of the contact hole 24 of the oxide insulating layer 12. The thickness of the Schottky electrode layer 15 is 1000 mm, for example.

  The electrode pad layer 16 has, for example, a three-layer structure of Ti / Pt / Au, like the ohmic electrode layer 11. The electrode pad layer 16 is formed from the surface of the Schottky electrode layer 15 to the surface of the oxide insulating layer 12. That is, the electrode pad layer 16 is formed between the covering portion 31 covering the surface of the Schottky electrode layer 15, the field plate portion 32 extending on the surface of the oxide insulating layer 12, and the covering portion 31 and the field plate portion 32. And a wiring portion 33 disposed in the middle.

  The covering portion 31 covers the entire surface of the Schottky electrode layer 15 in the contact hole 24. The field plate portion 32 extends from the opening edge portion of the contact hole 24 to the substantially central portion of the oxide insulating layer 12. A wire bond (not shown) is connected to the field plate portion 32 when the diamond electronic element 1 is packaged. The wiring part 33 is formed so as to cover the inner wall of the contact hole 24, and connects the edge of the covering part 31 and the edge of the field plate part 32 on the contact hole 24 side.

  Then, the manufacturing method of the diamond electronic element 1 which has the structure mentioned above is demonstrated.

  First, as shown in FIG. 2, a high-pressure synthetic substrate made of a diamond single crystal is prepared as the base layer 21. Next, both surfaces of the base layer 21 are polished by using, for example, a Skyf board. After polishing, the base layer 21 is ultrasonically cleaned with an organic solvent such as acetone or isopropyl alcohol. Further, after immersing in hot concentrated sulfuric acid and hydrofluoric acid, rinsing is performed using pure water.

  Next, one surface of the base layer 21 is etched by dry etching. As a result, crystal defects and scratches caused by polishing are removed from one surface of the base layer 21. For dry etching, microwave plasma CVD using a gas containing hydrogen gas or oxygen may be used, or parallel plate plasma etching or inductive junction plasma etching using oxygen gas may be used.

  After dry etching, the base layer 21 is placed on a substrate holder on which molybdenum coating is applied, and as shown in FIG. 3, a bulk layer 22 is synthesized on one surface of the base layer 21 using a microwave plasma CVD apparatus. To do. In synthesizing the bulk layer 22, first, only hydrogen gas is introduced at 50 Torr and a total flow rate of 400 sccm, and processing is performed for 15 minutes at a microwave power of 1200 W and a substrate temperature of 900 ° C.

Next, the methane concentration in hydrogen gas is set to 0.6%, and B ₂ H ₆ is added so that the elemental composition ratio of boron to carbon is 10%, and the first layer is synthesized by treatment for 1 hour. To do. Subsequently, the methane concentration in the hydrogen gas is set to 0.6%, and B ₂ H ₆ is added so that the elemental composition ratio of boron to carbon is 1.6%, and the second layer is obtained by treatment for 5 hours. Is synthesized. As a result, as shown in FIG. 4, a bulk layer 22 made of a diamond semiconductor having a P ⁺ conductivity type is formed.

  Next, the base layer 21 is placed on the substrate holder on which the diamond coating is applied, and the drift layer 23 is synthesized on the surface of the bulk layer 22 using a microwave plasma CVD apparatus. In synthesizing the drift layer 23, first, only hydrogen gas is introduced at 120 Torr and a total flow rate of 400 sccm, and a treatment is performed at a microwave power of 1200 W and a substrate temperature of 900 ° C. for 15 minutes. Subsequently, the methane concentration in the hydrogen gas is set to 0.5%, and the treatment is performed for 16 hours. As a result, a drift layer 23 having a thickness of about 10 μm is formed on the surface of the bulk layer 22.

After forming the drift layer 23, the diamond substrate 10 is boiled and washed in a mixed acid of sulfuric acid and nitric acid. Next, a mask layer made of, for example, Al is formed on the surface of the drift layer 23. Further, after patterning the mask layer by photolithography, the mask layer is dry-etched by supplying, for example, Cl ₂ gas and BCl ₃ gas to the ICP plasma apparatus. Then, for example, by supplying O ₂ gas and CF ₄ gas to the ICP plasma apparatus, a contact hole for ohmic junction is formed in the drift layer 23. Thereafter, the mask layer is removed using a predetermined acid.

  Next, after patterning by photolithography, Ti / Pt / Au is deposited in a thickness of 1000% each and lifted off. Then, this is annealed under the conditions of 1 Torr and 400 ° C. in an atmosphere of Ar gas, so that an ohmic electrode extending in the contact hole of the drift layer 23 and the surface of the bulk layer 22 is formed as shown in FIG. Layer 11 is formed.

  After the formation of the ohmic electrode layer 11, patterning by photolithography is performed, and an intermediate layer made of Ti is formed on the surface of the drift layer 23 with a thickness of about 200 mm as shown in FIG. At this time, the distance L1 of the region where the intermediate layer 13 is not formed on the surface of the drift layer 23 is, for example, 200 μm or less, and the distance L2 from the side surface 23a of the drift layer 23 to the edge of the intermediate layer 13 is 100 μm or less. Furthermore, Au is vapor-deposited using photolithography, and the marking part 14 is formed on the surface of the intermediate layer 13.

Next, by using, for example, a microwave plasma CVD apparatus, the oxide insulating layer 12 made of SiO ₂ is formed on the surface of the drift layer 23 so as to cover the intermediate layer 13 and the marking portion 14 as shown in FIG. The thickness is about 1 μm. Then, patterning for the Schottky electrode layer 15 is performed on the oxide insulating layer 12 by, for example, an electron beam exposure machine.

  During the patterning, the oxide insulating layer 12 may be entirely charged up. However, since the marking portion 14 disposed inside the oxide insulating layer 12 has a function of sufficiently scattering electrons, it is possible to perform alignment with an electron microscope with high accuracy. After the patterning, a contact hole 24 is formed in the center of the oxide insulating layer 12 by, for example, wet etching using buffered hydrofluoric acid. Then, about 1000 liters of Pt is deposited on the bottom of the contact hole 24, and the Schottky electrode layer 15 is formed so as to be in contact with the surface of the drift layer 23 as shown in FIG.

  Finally, patterning by photolithography is performed to form a covering portion 31 that covers the surface of the Schottky electrode layer 15 as shown in FIG. Then, Ti / Pt / Au is evaporated and lifted off, and the field plate portion 32 and the wiring portion 33 are connected to the covering portion to form the electrode pad layer 16, thereby completing the diamond electronic device 1 shown in FIG. 1.

  In the diamond electronic device 1 described above, the oxide insulating layer 12 is disposed on one side of the drift layer 23 so as to surround the Schottky electrode layer 15. For this reason, graphitization of the surface of the drift layer 23 is suppressed even when used in a high temperature environment. Therefore, the phenomenon in which the reverse current increases through the outermost graphite layer can be suppressed, and the loss can be reduced.

  In the diamond electronic device 1, the intermediate layer 13 is interposed between the drift layer 23 and the oxide insulating layer 12, and the Schottky electrode layer 15 formed in the contact hole 24 of the oxide insulating layer 12 is oxidized. The electrode pad layer 16 extending to the surface of the material insulating layer 12 is covered. In other words, in this diamond electronic device 1, the oxide insulating layer 12 firmly bonded to the surface of the drift layer 23 through the intermediate layer 13 made of Ti having good reactivity, and the surface of the oxide insulating layer 12. By being covered with the strongly bonded electrode pad layer 16, adhesion between the drift layer 23 and the Schottky electrode layer 15 is supplemented. Thereby, peeling of the Schottky electrode layer 15 at the time of wire bonding can be suitably prevented.

  Here, regarding the arrangement configuration of the intermediate layer 13, the distance L1 between the drift layer 23 and the oxide insulating layer 12 where the intermediate layer 13 is not formed is 200 μm or less. For this reason, internal stress and thermal stress of the oxide insulating layer 12 in a portion that is not fixed to the intermediate layer 13 are relieved, and the oxide insulating layer 12 can be prevented from peeling from the drift layer 23. The distance L2 from the side surface of the drift layer 23 to the edge of the intermediate layer 13 is 100 μm or less. Since peeling of the oxide insulating layer 12 often occurs from the side surface 23a side of the drift layer 23, by extending the edge of the intermediate layer 13 to the vicinity of the side surface 23a of the drift layer 23, the oxide insulating layer 12 is Separation from the drift layer 23 can be effectively suppressed.

  Further, the intermediate layer 13 extends inside the oxide insulating layer 12 corresponding to the formation region of the field plate portion 32 in the electrode pad layer 16. When the field plate portion 32 is formed on the electrode pad layer 16, the electric field generated at the end on the Schottky electrode layer 15 side is weakened, while the electric field concentration tends to occur at the end of the field plate portion 32. Therefore, by forming the intermediate layer 13 corresponding to the formation region of the field plate portion 32, the electric field concentration can be suppressed, and the dielectric breakdown in the oxide insulating layer 12 can be prevented.

  Further, in the method of manufacturing the diamond electronic device 1, after forming the intermediate layer 13 and the oxide insulating layer 12 on one surface side of the drift layer 23, the contact hole 24 is formed at a desired position, and the Schottky electrode layer 15 is formed. Forming. By such a procedure, the Schottky electrode layer 15 that is easily peeled off from the drift layer 23 can be easily patterned. In addition, since wet etching using buffered hydrofluoric acid is performed in forming the contact hole 24, unlike the case of performing dry etching, damage to the surface of the drift layer 23 can be prevented, and good Schottky characteristics can be obtained. Is obtained.

  A marking portion 14 made of any one heavy metal of Hf, Ta, W, Re, Ir, Pt, and Au is formed on the surface of the intermediate layer 13. For this reason, even if the oxide insulating layer 12 is charged up when patterning the Schottky electrode layer 15 on the surface of the oxide insulating layer 12, electrons are sufficiently scattered by the marking portion 14. High contrast can be maintained and patterning accuracy can be maintained.

  Next, experimental results for confirming the effect of the diamond electronic device according to the present invention will be described.

  In this experiment, a sample (Example) having the same configuration as that of the diamond electronic element 1 and the oxide insulating layer 12 of the configuration of the diamond electronic element 1 were provided without forming the intermediate layer 13 and the marking portion 14. About the sample (comparative example), the presence or absence of the Schottky electrode layer 15 and the Schottky characteristics were verified.

In the comparative example, in the reverse direction characteristic, the leakage current in a state where a voltage of 2 MV / cm was applied was 13 to 3600 μA / cm ² . In the manufacturing process, when the surface of the oxide insulating layer 12 is patterned for the Schottky electrode layer 15, the oxide insulating layer 12 and the Schottky electrode layer are etched when the contact hole 24 is etched with buffered hydrofluoric acid. 15 peeling occurred, and the yield in all steps was 5% or less. In addition, when a probe was applied to the electrode pad layer 16 in order to measure the Schottky characteristics, there was a case where the flaking was generated. When electron beam exposure was performed using a substrate that did not peel off, alignment with the substrate was almost impossible due to charge-up of the oxide insulating layer 12.

On the other hand, in the example, in the reverse characteristics, the leakage current in a state where a voltage of 2 MV / cm was applied was 0.28 to 2.3 μA / cm ² . Further, when the sample was heated in vacuum at 500 ° C. for 100 hours and then returned to room temperature, and the Schottky characteristics were measured again, almost no change was observed from the above values. From this, it was confirmed in the Examples that even when used in a high temperature environment, graphitization of the surface of the diamond substrate is suppressed and a reduction in loss can be realized. Further, peeling of the oxide insulating layer 12 due to thermal stress did not occur.

  In the manufacturing process, when patterning for the Schottky electrode layer 15 is performed on the surface of the oxide insulating layer 12, the oxide insulating layer 12 and the Schottky electrode layer 15 are also etched when the contact hole 24 is etched with buffered hydrofluoric acid. Peeling did not occur and the yield in all steps was about 76%. In the electrode pad layer 16, even when Au wire bonding was performed, the oxide insulating layer 12 and the Schottky electrode layer 15 did not peel off. From these facts, it was confirmed that the diamond electronic device 1 and the manufacturing method thereof according to the present invention can reduce the loss and prevent the Schottky electrode layer from peeling off.

  The present invention is not limited to the above embodiment. For example, the electrode materials, synthesis conditions, and the like exemplified in the above-described embodiments may be appropriately changed according to the element specifications and the like. Further, the present invention can be applied not only to a diode but also to various power elements and transistors as long as it uses a Schottky junction.

It is sectional drawing which shows one Embodiment of the diamond electronic device which concerns on this invention. It is a figure which shows the manufacturing method of the diamond electronic element shown in FIG. FIG. 3 is a diagram showing a step subsequent to FIG. 2. FIG. 4 is a diagram showing a step subsequent to FIG. 3. FIG. 5 is a diagram showing a step subsequent to FIG. 4. FIG. 6 is a diagram showing a step subsequent to FIG. 5. FIG. 7 is a diagram showing a step subsequent to FIG. 6. FIG. 8 is a diagram showing a step subsequent to FIG. 7. FIG. 9 is a diagram showing a step subsequent to that in FIG. 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Diamond electronic element, 10 ... Diamond substrate, 12 ... Oxide insulating layer, 13 ... Intermediate layer, 14 ... Marking part, 15 ... Schottky electrode layer, 16 ... Electrode pad layer, 24 ... Contact hole, 32 ... Field plate Department.

Claims (7)

An oxide insulating layer formed on one side of the diamond substrate;
A Schottky electrode layer formed in a contact hole provided in the oxide insulating layer;
An electrode pad layer formed from the surface of the Schottky electrode layer to the surface of the oxide insulating layer,
A diamond electronic device, wherein an intermediate layer made of titanium is formed at least partly between the diamond substrate and the oxide insulating layer.   The diamond electronic device according to claim 1, wherein a distance between the diamond substrate and the oxide insulating layer in a region where the intermediate layer is not formed is 200 µm or less.   3. The diamond electronic device according to claim 1, wherein a distance from a side surface of the diamond substrate to an edge of the intermediate layer is 100 μm or less.   The diamond electronic device according to claim 1, wherein the oxide insulating layer has a thickness of 1 μm or more. The electrode pad layer has a field plate portion on the surface of the oxide insulating layer,
5. The diamond electronic device according to claim 1, wherein the intermediate layer extends inward of the oxide insulating layer corresponding to a region where the field plate portion is formed.   6. A marking portion made of any one heavy metal of Hf, Ta, W, Re, Ir, Pt, and Au is formed on the surface of the intermediate layer. The diamond electronic device according to Item. Forming an intermediate layer made of titanium on one side of the diamond substrate;
Forming an oxide insulating layer on the one surface side of the diamond substrate so as to cover the intermediate layer;
Forming a contact hole in the oxide insulating layer by wet etching using a predetermined mask;
Forming a Schottky electrode layer in the contact hole;
And a step of forming an electrode pad layer from the surface of the Schottky electrode layer to the surface of the oxide insulating layer.

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