Method of fabricating epitaxial structures and epitaxial structures

Abstract

To provide a method for manufacturing an epitaxial structure, capable of providing an epitaxial structure that has a good withstand voltage performance and that is suppressed in formation of defects.SOLUTION: A method for manufacturing an epitaxial structure includes: providing a substrate; forming a first buffer layer above the substrate; forming a roughened layer above the first buffer layer, a process of forming the roughened layer including performing a first low-temperature growth step and a high-temperature growth step, the first low-temperature growth step including forming a first intrinsically doped structure at a first low-temperature, the high-temperature growth step including forming an extrinsically doped structure at a high-temperature, the process of forming the roughened layer including performing the first low-temperature growth step and the high-temperature growth step in sequence at least one time to form the roughened layer, the high-temperature being greater than the first low-temperature; forming a second buffer layer above the roughened layer; and forming a channel layer above the second buffer layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an epitaxial structure, and more particularly to an epitaxial structure having doping. [Background technology]

[0002] Known high-electron-mobility transistors (HEMTs) are transistors that have a two-dimensional electron gas (2-DEG), which is adjacent to a heterojunction surface located between two types of materials with different band gaps. Because high-electron-mobility transistors use a two-dimensional electron gas with high electron mobility as the carrier channel of the transistor, without using a doping region as the transistor's carrier channel, high-electron-mobility transistors have characteristics such as a high decay voltage, a high electron transition rate, low resistance during conduction, and low input capacitance, and are widely applied to high-power semiconductor devices.

[0003] High electron-mobility transistors (TRPs) typically have their voltage withstand capability enhanced through doping configurations. However, commonly used doping configurations have drawbacks, such as a tendency to form defects. Therefore, providing an epitaxial configuration that enhances voltage withstand capability while being less prone to defect formation is a problem that needs to be addressed as soon as possible. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In view of this, the present invention aims to provide a method for manufacturing an epitaxial structure that has excellent voltage resistance and is not prone to forming defects. [Means for solving the problem]

[0005] To achieve the above objective, the present invention provides a method for manufacturing an epitaxial structure, comprising the steps of providing a substrate, forming a first buffer layer on the substrate, and forming a roughened layer on the first buffer layer, wherein the step of forming the roughened layer includes performing a first low-temperature growth step and a high-temperature growth step, of which the first low-temperature growth step includes forming a first essential doping structure at a first low temperature, and the high-temperature growth step includes forming an external impurity doping structure at a high temperature, wherein the step of forming the roughened layer includes performing the first low-temperature growth step and the high-temperature growth step sequentially at least once to form the roughened layer, and further includes a step in which the high temperature is greater than the first low temperature, forming a second buffer layer on the roughened layer, and forming a channel layer on the second buffer layer.

[0006] In one embodiment, the difference between the high temperature and the first low temperature is 50 degrees Celsius or more.

[0007] In one embodiment, the high temperature is 1000 degrees Celsius or higher, and the first low temperature is 980 degrees Celsius or lower.

[0008] In one embodiment, the first low-temperature growth step includes forming the first essential doping configuration at a first low-temperature process pressure, and the high-temperature growth step includes forming the external impurity doping configuration at a high-temperature process pressure, wherein the high-temperature process pressure is greater than the first low-temperature process pressure.

[0009] In one embodiment, the high-temperature process pressure is twice or more the first low-temperature process pressure.

[0010] In one embodiment, the high-temperature process pressure is 150 torr or higher, and the first low-temperature process pressure is 75 torr or lower.

[0011] In one embodiment, the thickness of the first essential doping configuration is greater than the thickness of the external impurity doping configuration.

[0012] In one embodiment, the thickness of the first essential doping structure is 2 to 6 times the thickness of the external impurity doping structure.

[0013] In one embodiment, the total thickness of the first essential doping structure in the roughened layer is 60% or more of the thickness of the roughened layer, and the thickness of the roughened layer is greater than 600 nm, or equal to 600 nm and less than 1000 nm, or equal to 1000 nm.

[0014] In one embodiment, the aluminum content in the portion of the first buffer layer in contact with the roughened layer is 20% or less, and the roughened layer is controlled to not contain aluminum.

[0015] In one embodiment, the carbon doping concentration in the first essential doping configuration and the external impurity doping configuration is 1E19 cm⁻¹. -3 That's all.

[0016] In one embodiment, the step of forming the roughened layer includes a second low-temperature growth step, the step of forming the roughened layer includes forming the roughened layer by performing the first low-temperature growth step, the high-temperature growth step, and the second low-temperature growth step in order at least once, the second low-temperature growth step includes forming the second essential doping structure at a second low temperature, and the high temperature is greater than the second low temperature.

[0017] In one embodiment, the second low-temperature growth step includes forming the second essential doping configuration at a second low-temperature process pressure, wherein the high-temperature process pressure is greater than the second low-temperature process pressure.

[0018] In one embodiment, the first low temperature is equal to the second low temperature, and the first low-temperature process pressure is equal to the second low-temperature process pressure.

[0019] In one embodiment, the total thickness of the first intrinsic doping structure and the second intrinsic doping structure in the roughening layer is 80% or more of the thickness of the roughening layer, and the thickness of the roughening layer is greater than or equal to 600 nm and less than or equal to 1000 nm.

[0020] In one embodiment, the thickness of the second intrinsic doping structure is greater than or equal to the thickness of the external impurity doping structure, and the thickness of the first intrinsic doping structure is greater than or equal to the thickness of the second intrinsic doping structure.

[0021] In one embodiment, the carbon doping concentration in the second intrinsic doping structure is 1E19cm -3 or more.

[0022] An epitaxial structure further provided by the present invention comprises a substrate, a first buffer layer, a roughening layer, a second buffer layer and a channel layer, wherein the first buffer layer is located above the substrate, the roughening layer is located above the first buffer layer, the roughening layer comprises at least one doping structure, the at least one doping structure comprises a first intrinsic doping structure and an external impurity doping structure stacked on each other, the second buffer layer is located above the roughening layer, the channel layer is located above the second buffer layer, wherein the aluminum content at a position of the first buffer layer in contact with the roughening layer is 20% or less, the roughening layer does not contain aluminum, and the doping concentration of the first intrinsic doping structure is greater than or equal to that of the external impurity doping structure.

[0023] In one embodiment, the carbon doping concentration in the first intrinsic doping structure and the external impurity doping structure is 1E19cm -3 or more.

[0024] In one embodiment, the thickness of the first intrinsic doping structure is greater than the thickness of the external impurity doping structure.

[0025] In one embodiment, the thickness of the first intrinsic doping structure is 2 to 6 times the thickness of the external impurity doping structure.

[0026] In one embodiment, the total thickness of the first intrinsic doping structures in the roughened layer is 60% or more of the thickness of the roughened layer, and the thickness of the roughened layer is greater than 600 nm, or equal to 600 nm and less than 1000 nm, or equal to 1000 nm.

[0027] In one embodiment, at least one of the doping structures comprises a second intrinsic doping structure, the first intrinsic doping structure, the external impurity doping structure and the second intrinsic doping structure are stacked in sequence, the carbon doping concentration in the second intrinsic doping structure is greater than or equal to that in the external impurity doping structure, and the carbon doping concentration in the second intrinsic doping structure is 1E19cm -3 or more.

[0028] In one embodiment, the total thickness of the first intrinsic doping structure and the second intrinsic doping structure in the roughened layer is 80% or more of the thickness of the roughened layer, and the thickness of the roughened layer is greater than 600 nm, or equal to 600 nm and less than 1000 nm, or equal to 1000 nm.

[0029] In one embodiment, the thickness of the second intrinsic doping structure is greater than or equal to the thickness of the external impurity doping structure, and the thickness of the first intrinsic doping structure is greater than or equal to the thickness of the second intrinsic doping structure. Effects of the Invention

[0030] The effect of the present invention is that by performing the first low-temperature growth step and the high-temperature growth step sequentially at least once to form the roughened layer, an epitaxial structure with excellent epitaxial quality can be provided, which can not only effectively improve the voltage withstand capability of the epitaxial structure, but also makes it difficult for defects to form on the surface of the epitaxial structure. [Brief explanation of the drawing]

[0031] [Figure 1] This flowchart shows a method for manufacturing an epitaxial structure according to a preferred embodiment of the present invention. [Figure 2] This is an epitaxial configuration according to a preferred first embodiment of the present invention. [Figure 3] This is an epitaxial configuration according to another preferred embodiment of the present invention. [Figure 4] This is an epitaxial configuration according to a preferred second embodiment of the present invention. [Figure 5] This is an epitaxial configuration according to another preferred embodiment of the present invention. [Modes for carrying out the invention]

[0032] To explain the present invention more clearly, preferred embodiments will be described in detail below with reference to the drawings. Figure 1 is a flowchart of a method for manufacturing an epitaxial structure 1 according to a preferred first embodiment of the present invention, and the method for manufacturing the epitaxial structure 1 includes the following steps.

[0033] Step S02 provides a substrate 10, which may be, for example, a silicon substrate or a carbonized silicon substrate.

[0034] Step S04 involves forming a first buffer layer 20 on top of the substrate 10, and the first buffer layer 20 may be an aluminum-containing nitride layer, such as aluminum gallium nitride (AlGaN). Step S04 further includes controlling the surface aluminum content of the first buffer layer 20 to be 20 at% or less.

[0035] In this embodiment, the aluminum content on the surface of the first buffer layer 20 is described as equal to 10 at%, but the thickness T1 of the first buffer layer 20 is preferably 3 μm or more. This increases the dielectric strength. The aluminum content in the first buffer layer 20 may decrease gradually in a stepwise or linear manner from the surface in contact with the substrate 10 towards the surface of the first buffer layer 20. Furthermore, the first buffer layer 20 may be composed of a single layer, multiple layers, or a superlattice layer.

[0036] Step S06 involves forming a roughened layer 30 above the first buffer layer 20, and the process of forming the roughened layer 30 includes performing a first low-temperature growth step and a high-temperature growth step, of which the first low-temperature growth step includes forming a first essential doping structure 32 at a first low temperature, and the high-temperature growth step includes forming an external impurity doping structure 34 at a high temperature, and the process of forming the roughened layer 30 includes performing the first low-temperature growth step and the high-temperature growth step sequentially at least once to form the roughened layer 30, wherein the high temperature is greater than the first low temperature. In this embodiment, the roughened layer 30 does not contain aluminum, and the roughened layer 30 is a gallium nitride (GaN) layer.

[0037] Of these, the difference between the high temperature and the first low temperature is 50 degrees Celsius or more. The high temperature is 1000 degrees Celsius or more. The first low temperature is 980 degrees Celsius or less. Preferably, the first low temperature is 925 degrees Celsius or more and 975 degrees Celsius or less.

[0038] The first low-temperature growth step includes forming the first essential doping structure 32 at the first low-temperature process pressure, and the high-temperature growth step includes forming the external impurity doping structure 34 at the high-temperature process pressure, wherein the high-temperature process pressure is greater than the first low-temperature process pressure. Of these, the high-temperature process pressure is more than twice the first low-temperature process pressure. The high-temperature process pressure is 150 torr or more. The first low-temperature process pressure is 75 torr or less.

[0039] Among them, the thickness T2 of the first intrinsic doping structure 32 is larger than the thickness T3 of the external impurity doping structure 34. The thickness T2 of the first intrinsic doping structure 32 is 2 to 6 times the thickness T3 of the external impurity doping structure 34. In this embodiment, the case where the multiple is 5 is taken as an example for description. The total thickness of the first intrinsic doping structures 32 in the roughened layer 30 accounts for 60% or more of the thickness T of the roughened layer 30, and the thickness T of the roughened layer 30 is greater than or equal to 600 nm and less than or equal to 1000 nm.

[0040] In this embodiment, the doped element in the first intrinsic doping structure 32 and the external impurity doping structure 34 is carbon. When forming the first intrinsic doping structure 32, no additional carbon source is provided, while when forming the external impurity doping structure 34, a carbon source Provide is provided. The carbon doping concentration in each of the first intrinsic doping structure 32 and the external impurity doping structure 34 is 1E19 cm -3 or more. In this embodiment, it is exemplarily described that the carbon doping concentration in the first intrinsic doping structure 32 is 3E19 cm -3 and the carbon doping concentration in the external impurity doping structure 34 is 1E19 cm -3 .

[0041] Step S08 is forming a second buffer layer 40 above the roughened layer 30. In this embodiment, the second buffer layer 40 is an aluminum-free gallium nitride (GaN) layer, the thickness T4 of the second buffer layer 40 is 1.5 um or more, the second buffer layer 40 is formed in a high-temperature environment higher than 1000 degrees Celsius and a high-pressure environment of 150 torr to 200 torr, and the external impurity doped carbon concentration in the second buffer layer 40 is 1E19 cm -3 or more and 3E19 cm -3 or less.

[0042] Step S10 involves forming a channel layer 50 above the second buffer layer 40, and the channel layer 50 may be a nitride channel layer, for example, gallium nitride (GaN).

[0043] In this embodiment, the first low-temperature growth step and the high-temperature growth step are performed sequentially at least once to form the roughened layer 30 formed by superimposing the first essential doping configuration 32 and the external impurity doping configuration 34 (see Figure 2). In other embodiments, the epitaxial configuration 1' shown in Figure 3 may be used. The first low-temperature growth step and the high-temperature growth step are performed sequentially multiple times to form the roughened layer 30 formed by superimposing the first essential doping configuration 32 and the external impurity doping configuration 34. In the roughened layer 30, the total thickness of the first essential doping configuration 32 is 60% or more of the thickness T of the roughened layer 30. Preferably, the first low-temperature growth step and the high-temperature growth step are performed sequentially 2 to 4 times.

[0044] In a preferred second embodiment, there is a method for producing an epitaxial structure that is substantially the same as in the preferred first embodiment described above, but with the following differences: The step of forming the roughened layer 30 further includes a second low-temperature growth step. The step of forming the roughened layer 30 includes forming the roughened layer 30 by performing the first low-temperature growth step, the high-temperature growth step, and the second low-temperature growth step in order only once, wherein the second low-temperature growth step includes forming the second essential doping structure 32' at a second low-temperature temperature, and the high-temperature temperature is greater than the second low-temperature temperature. Of these, the second low-temperature growth step includes forming the second essential doping structure 32' at a second low-temperature process pressure, and the high-temperature process pressure is greater than the second low-temperature process pressure. The first low-temperature temperature is equal to the second low-temperature temperature, and the first low-temperature process pressure is equal to the second low-temperature process pressure.

[0045] In the roughened layer 30, the sum of the thicknesses of the first essential doping configuration 32 and the second essential doping configuration 32' is 80% or more of the thickness of the roughened layer T, and the thickness T of the roughened layer 30 is greater than or equal to 600 nm and less than or equal to 1000 nm. In the roughened layer 30, the thickness T1' of the second essential doping configuration 32' is greater than or equal to the thickness T2 of the external impurity doping configuration 34, the thickness T2 of the first essential doping configuration 32 is greater than or equal to the thickness T2' of the second essential doping configuration 32', and the carbon doping concentration in the second essential doping configuration 32' is 1E19cm³. -3 That's all.

[0046] In the preferred second embodiment described above, the first low-temperature growth step, the high-temperature growth step, and the second low-temperature growth step are performed in order only once to form the roughened layer 30 formed by superimposing the first essential doping configuration 32, the external impurity doping configuration 34, and the second essential doping configuration 32' (see Figure 4). In other embodiments, the epitaxial configuration 2' shown in Figure 5 may be used. The roughened layer 30 is formed by superimposing the first essential doping configuration 32, the external impurity doping configuration 34, and the second essential doping configuration 32' onto each other by performing the first low-temperature growth step, the high-temperature growth step, and the second low-temperature growth step multiple times in order. The total thickness of the first essential doping configuration 32 and the second essential doping configuration 32' is 80% or more of the thickness of the roughened layer T. Of these, the number of times the first low-temperature growth step, the high-temperature growth step, and the second low-temperature growth step are performed in sequence is preferably 1 to 2 times.

[0047] Figure 2 shows epitaxial structure 1, which was fabricated by the method for fabricating the epitaxial structure according to the preferred first embodiment described above. The epitaxial configuration 1 includes the substrate 10, the first buffer layer 20, the roughening layer 30, the second buffer layer 40, and the channel layer 50, wherein the first buffer layer 20 is located above the substrate 10, the roughening layer 30 is located above the first buffer layer 20, the roughening layer 30 includes a doping configuration, the doping configuration includes a first essential doping configuration 32 and an external impurity doping configuration 34 which are superimposed on each other, the second buffer layer 40 is located above the roughening layer 30, and the channel layer 50 is located above the second buffer layer 40, wherein the aluminum content in the portion of the first buffer layer 20 in contact with the roughening layer 30 is 20% or less, the roughening layer 30 does not contain aluminum, and the doping concentration in the first essential doping configuration 32 is greater than or equal to that of the external impurity doping configuration 34.

[0048] As shown in Figure 3, in other embodiments, the roughened layer 30 may include multiple doping configurations, that is, it may include the first essential doping configuration 32 and the external impurity doping configuration 34, which are stacked in multiple layers, and preferably a configuration doped with 2 to 4 layers.

[0049] Figure 4 shows an epitaxial structure 2 manufactured by the method for manufacturing an epitaxial structure according to the preferred second embodiment described above. The epitaxial structure 2 includes the substrate 10, the first buffer layer 20, the roughening layer 30, the second buffer layer 40, and the channel layer 50, wherein the first buffer layer 20 is located above the substrate 10, the roughening layer 30 is located above the first buffer layer 20, and the roughening layer 30 includes the doping configuration. The doping configuration includes the first essential doping configuration 32 and the external impurity doping configuration 34 which are superimposed on each other, and further includes the second essential doping configuration 32' which is superimposed on the external impurity doping configuration 34. The second buffer layer 40 is located above the roughening layer 30. The channel layer 50 is located above the second buffer layer 40. Of these, the aluminum content in the portion of the first buffer layer 20 in contact with the roughened layer 30 is 20% or less, the roughened layer 30 does not contain aluminum, the doping concentration in the first essential doping configuration 32 is greater than or equal to that of the external impurity doping configuration 34, and the carbon doping concentration in the second essential doping configuration 32' is greater than or equal to that of the external impurity doping configuration 34.

[0050] As shown in Figure 5, in other embodiments, the roughened layer may include multiple doping configurations, that is, it may include the first essential doping configuration 32, the external impurity doping configuration 34, and the second essential doping configuration 32', which consist of only multiple layers stacked together, with a configuration doped with one to two layers being preferred.

[0051] In the epitaxial structures 1, 1', 2, and 2' manufactured by the epitaxial structure manufacturing method described above, the average number of defects with a diameter of 0.3 μm or less per square centimeter on the surface of the channel layer 50 is 2 or less, the average number of defects with a diameter of 0.2 μm or less per square centimeter is 1 or less, and the average number of defects with a diameter of 0.1 μm or less per square centimeter is 0.5 or less. Examples of these defects include hexagonal defects, stacked defects, and hole-shaped defects, which are common defects in epitaxial processes, but these defects do not include defects formed by external forces such as dust or scratches. Furthermore, when a forward voltage of 650 V is applied to the epitaxial structures 1, 1', 2, and 2', the leakage current of the epitaxial structures 1, 1', 2, and 2' is 3E-7 A / cm². -2 It is smaller than that.

[0052] In short, the effects of the present invention are as follows: By performing the first low-temperature growth step and the high-temperature growth step in order at least once to form the roughened layer 30, it is possible to provide an epitaxial structure with excellent epitaxial quality, effectively increase the dielectric strength of the epitaxial structure, and make it less likely to form defects on the surface of the epitaxial structure.

[0053] The above description is merely a preferred embodiment of the present invention, and any equivalent substitutions made by applying the claims together with the specification of the present invention should be included within the scope of the claims of the present invention. [Explanation of Symbols]

[0054] 1. Epitaxial configuration 1' Epitaxial configuration 2. Epitaxial configuration 2' Epitaxial configuration 10 circuit boards 20 First buffer layer 30 Roughening layer 32 Essential Doping Composition 34 External impurity doping configuration 32' Second Essential Doping Composition T thickness T1 Thickness T2 thickness T2' Thickness T3 thickness T4 thickness 40 Second buffer layer 50 channel layers S02 Step S04 Step S06 Step S08 Step S10 Step

Claims

1. To provide a substrate, A first buffer layer is formed above the substrate. A roughening layer is formed above the first buffer layer, and the process of forming the roughening layer includes performing a first low-temperature growth step and a high-temperature growth step, the first low-temperature growth step includes forming a first essential doping configuration at a first low temperature, the high-temperature growth step includes forming an external impurity doping configuration at a high temperature, and the process of forming the roughening layer includes performing the first low-temperature growth step and the high-temperature growth step in order at least once to form the roughening layer, wherein the high temperature is higher than the first low temperature. Forming a second buffer layer above the roughened layer, and This includes forming a channel layer above the second buffer layer. The aforementioned high temperature is 1000 degrees Celsius or higher. A method for manufacturing an epitaxial structure, characterized in that the first low temperature is 980 degrees Celsius or lower.

2. The method for manufacturing an epitaxial structure according to claim 1, characterized in that the difference between the high temperature and the first low temperature is 50 degrees Celsius or more.

3. The first low-temperature growth step includes forming the first essential doping configuration at the first low-temperature process pressure, and the high-temperature growth step includes forming the external impurity doping configuration at the high-temperature process pressure. The method for manufacturing an epitaxial structure according to claim 1, characterized in that the high-temperature process pressure is greater than the first low-temperature process pressure.

4. The method for manufacturing an epitaxial structure according to claim 3, characterized in that the high-temperature process pressure is twice or more the first low-temperature process pressure.

5. The process of forming the roughened layer includes a second low-temperature growth step, The process of forming the roughened layer includes performing the first low-temperature growth step, the high-temperature growth step, and the second low-temperature growth step in order at least once to form the roughened layer. The aforementioned second low-temperature growth step includes forming a second essential doping structure at a second low-temperature temperature, The method for manufacturing an epitaxial structure according to claim 3, characterized in that the high temperature is greater than the second low temperature.

6. The method for producing an epitaxial structure according to claim 5, characterized in that the second low-temperature growth step includes forming the second essential doping structure at a second low-temperature process pressure, wherein the high-temperature process pressure is greater than the second low-temperature process pressure.

7. The first low temperature is equal to the second low temperature, The method for manufacturing an epitaxial structure according to claim 6, characterized in that the first low-temperature process pressure is equal to the second low-temperature process pressure.

8. circuit board and A first buffer layer located above the substrate, A roughening layer located above the first buffer layer, comprising at least one doping configuration, wherein at least one of the doping configurations includes a first essential doping configuration and an external impurity doping configuration superimposed on each other, A second buffer layer located above the aforementioned roughened layer, It includes a channel layer located above the second buffer layer, An epitaxial configuration characterized by having an aluminum content of 20% or less in the portion of the first buffer layer in contact with the roughened layer, no aluminum in the roughened layer, and a doping concentration of the first essential doping configuration that is greater than or equal to that of the external impurity doping configuration.

9. The first essential doping configuration and the external impurity doping configuration have a carbon doping concentration of 1E19cm². -3 The epitaxial configuration according to feature 8 is as described above.

10. The epitaxial configuration according to claim 8, characterized in that the thickness of the first essential doping configuration is greater than the thickness of the external impurity doping configuration.

11. The epitaxial configuration according to claim 8, characterized in that the thickness of the first essential doping configuration is 2 to 6 times the thickness of the external impurity doping configuration.

12. The epitaxial structure according to claim 8, characterized in that the total thickness of the first essential doping structure in the roughened layer is 60% or more of the thickness of the roughened layer, and the thickness of the roughened layer is greater than 600 nm, or equal to 600 nm and less than 1000 nm, or equal to 1000 nm.

13. At least one of the doping configurations includes a second essential doping configuration, and the first essential doping configuration, the external impurity doping configuration, and the second essential doping configuration are superimposed in order. The carbon doping concentration in the second essential doping configuration is greater than or equal to that of the external impurity doping configuration, and the carbon doping concentration in the second essential doping configuration is 1E19cm². -3 The epitaxial configuration according to feature 8 is as described above.

14. The epitaxial configuration according to claim 13, characterized in that the total thickness of the first essential doping configuration and the second essential doping configuration in the roughened layer is 80% or more of the thickness of the roughened layer, and the thickness of the roughened layer is greater than 600 nm, or equal to 600 nm and less than 1000 nm, or equal to 1000 nm.

15. The thickness of the second essential doping structure is greater than or equal to the thickness of the external impurity doping structure. The epitaxial configuration according to claim 13, characterized in that the thickness of the first essential doping configuration is greater than or equal to the thickness of the second essential doping configuration.

16. When a forward voltage of 650V is applied to the epitaxial configuration, the leakage current of the epitaxial configuration is 3E-7A / cm. -2 The epitaxial configuration according to claim 8, characterized in that it is smaller than [a certain value].

Images