JP2014160719A - Diamond semiconductor element - Google Patents

Abstract

Disclosed is a diamond semiconductor element suitable for a power device under high output / high withstand voltage or high withstand environment.
A diamond semiconductor device having p + single crystal diamond, a p-layer made of a diamond semiconductor formed on the p + single crystal diamond, and an electrode formed on an electrode formation region of the p- layer. In the p-layer of the electrode formation region, the number of first dislocations that can be observed with the X-ray topography image of the diffraction vector [−404] but cannot be observed with the X-ray topography image of the diffraction vector [113]. Is 0, and second dislocations other than the first dislocation exist at a dislocation density of 1.0 × 10 ^{2 to} 2.0 × 10 ⁴ / cm ² .
[Selection] Figure 6

Description

  The present invention relates to diamond semiconductor elements such as diodes, transistors, FETs, and thyristors.

  In recent years, a diamond semiconductor element is expected as an element that can be practically operated under a large band gap, a high avalanche breakdown electric field, a high saturation carrier mobility, a high thermal conductivity, a high temperature and a radiation exposure environment. Development of high-power diamond semiconductor elements such as diamond Schottky barrier diodes, diamond field effect transistors, diamond pn diodes, diamond thyristors, and diamond transistors has been promoted as semiconductor elements utilizing these characteristics.

  The present inventors have conducted research and development of high-quality diamond semiconductor elements (see Patent Documents 1, 4, and 5).

  Conventionally, as a diamond semiconductor element, a Schottky barrier diode having a structure including a Schottky electrode as a cathode, an ohmic electrode as an anode, a Schottky electrode, a diamond p-drift layer, a diamond p + contact layer, and an ohmic electrode (see Patent Document 5) The research and development has been promoted for the present inventors. Research and development have been conducted on diamond transistors having a structure comprising a diamond p-layer, a non-doped diamond layer, a source electrode, a drain electrode, and a gate electrode.

  A conventional diamond semiconductor device structure is shown in FIGS. As shown in FIG. 1A, a p + diamond layer 2 is grown on a semi-insulating diamond substrate 1 and a p-diamond layer 3 is grown thereon to produce a laminated structure. In the laminated structure, the ohmic electrode 5 is provided on the p-diamond layer 3 and the Schottky electrode 4 is provided on the p-diamond layer 3 to produce a lateral Schottky barrier diode element. As shown in FIG. 1B, a p + diamond layer 2 is grown on a semi-insulating diamond substrate 1, and a p-diamond layer 3 is grown on a part of the p + diamond layer 2 to produce a laminated structure. In the laminated structure, the ohmic electrode 5 is provided on the p-diamond layer 3 and the Schottky electrode 4 is provided on the p + diamond layer 2 to produce a pseudo vertical Schottky barrier diode element. Further, as shown in FIG. 1C, a p-diamond layer 3 is grown on a p + diamond substrate 6 to produce a laminated structure, and an ohmic electrode 5 is provided on the p + diamond substrate 6 to form the Schottky. The electrode 4 was provided on the p-diamond layer 3 to produce a vertical Schottky barrier diode element. Further, a semiconductor diamond layer is used as an operating layer, and a laminated structure in which a non-doped layer made of diamond is formed only between the gate electrode for controlling the transistor operation and the operating layer is formed. A transistor element having a source / drain electrode on the surface and a gate electrode on a non-doped layer was produced.

  X-ray topography is known as a defect analysis method for crystal layers (see Patent Documents 1 and 3). X-ray topography is a technique for photographing the intensity distribution of X-ray diffraction over the entire crystal. The normal vector of the X-ray diffraction plane (crystal plane S) is referred to as g vector (see Patent Document 1).

  A schematic configuration of a reflection X-ray topography apparatus is shown in FIG. 7 (see Patent Document 3). The apparatus includes a measurement sample 11, an X-ray source 12, a monochromator 13, a recording medium 14, and an X-ray diffraction recording computer 10. A topography image can be obtained by irradiating the measurement sample 11 with X-rays emitted from the X-ray source 12 and detecting the diffracted light reflected from the sample. The topography image recorded on the recording medium 14 is photographed in the state of a defect enlarged image using an optical microscope, and is taken into the X-ray diffraction recording computer 10 (see Patent Document 3).

Research and development has been advanced on crystal defects and device withstand voltage in diamond semiconductor elements (see Patent Documents 1, 2, and 4). For example, a diamond semiconductor element in which an electrode is provided on a region of a diamond epitaxial layer having a composite dislocation with a surface density of 3 × 10 ⁴ / cm ² or less has been proposed (see Patent Document 1).

JP 2010-98262 A Special table 2010-517263 JP 2009-44083 A JP 2007-95975 A Japanese Patent No. 5051835 JP 2009-59798 A

  A diamond semiconductor element having high crystallinity is expected as a power device under high output / high withstand voltage or high environment resistance, but it is not easy to produce a defect-free / strain-free diamond. Therefore, it is necessary to investigate defects that hinder device characteristics and to realize high-quality diamond semiconductor elements as devices.

  In an existing device structure, in order to achieve a withstand voltage of 1 kV or more and further increase in current, it is necessary to expand the electrode size to about 1 mm square by a scaling rule. In the prior art, for example, when the element size of a diamond Schottky barrier diode (see FIG. 1) is increased, a phenomenon that device characteristics, particularly withstand voltage characteristics, deteriorates is observed. The cause of this problem is considered to be that the number of dislocations in the element increases as the element size increases, and the effect of lowering the breakdown voltage characteristics due to dislocations exceeds the breakdown voltage characteristics derived from the material.

For example, when producing a diamond Schottky barrier diode, a p + diamond layer is grown on a semi-insulating diamond substrate to a thickness of 0.5 to 50 μm, and a p-diamond layer is grown on the p-diamond layer 1 to 20 μm (see FIG. 1 (a) (b)). Alternatively, a p-diamond layer is grown on the p + diamond substrate by 1 to 20 μm (see FIG. 1C). The p + diamond layer serves as a contact layer, and is doped with a very high impurity concentration of about 10 ²⁰ to 10 ²¹ atoms / cm ^{3 in} order to reduce parasitic resistance. Impurities and carbon differ in ion radius and number of outermost electrons. For this reason, lattice mismatch with the diamond substrate occurs, and the p + diamond layer is likely to undergo lattice distortion during crystal growth. On the other hand, the p-diamond layer functioning as a drift layer is required to maintain a voltage with a low leakage current even in a high electric field by extending the depletion layer when a reverse bias is applied, and therefore requires high crystallinity.

  In the case of a device structure in which a p-diamond layer is formed on a p + diamond layer, if the element size is increased from 200 μm to several mm square, the device characteristics are improved due to crystallinity in the p− layer, particularly dislocations. to degrade. The cause of the occurrence of dislocation is crystal distortion inside the p-layer. Since the p + layer has a higher dopant concentration than the p− layer, the crystal lattice is large. The crystal distortion inside the p− layer is considered to be due to the difference in lattice constant from the p + layer having a high dopant concentration. For this reason, distortion is likely to occur in the p-layer, and the occurrence of dislocations cannot be avoided. Thus, it has been difficult to use a diamond Schottky barrier diode as a high voltage power device.

  An object of the present invention is to solve these problems, and an object of the present invention is to provide a diamond semiconductor element having an optimized dislocation density, which is suitable for a power device under a high output, high withstand voltage or high withstand environment.

In the present invention, a diamond semiconductor element suitable for a power device under a high output, high withstand voltage or high withstand environment is realized by optimizing dislocations that cause characteristic deterioration and the density of dislocations that do not affect the characteristics.
In order to achieve the above object, the present invention has the following features.

The present invention relates to a diamond semiconductor device having p + single crystal diamond, a p− layer made of a diamond semiconductor formed on the p + single crystal diamond, and an electrode formed on an electrode formation region of the p− layer. In the p-layer of the electrode formation region, the first dislocation that can be observed in the X-ray topography image of the diffraction vector [-404] but cannot be observed in the X-ray topography image of the diffraction vector [113]. The number is 0, and the second dislocation other than the first dislocation is present at a dislocation density of 1.0 × 10 ^{2 to} 2.0 × 10 ⁴ / cm ² .

  In the present invention, the electrode is preferably either a Schottky electrode or an ohmic electrode, for example. In the present invention, the p + single crystal diamond is preferably a p + layer made of conductive diamond formed on a semi-insulating single crystal diamond substrate or a p + substrate made of conductive diamond. In the present invention, it is preferable that the p + single crystal diamond is a contact layer and the p− layer is a drift layer. In the present invention, the diamond semiconductor element is preferably a Schottky diode, a pn junction diode, or a pin junction diode.

  Here, the region where the electrode is formed on the surface of the p-diamond layer is referred to as an electrode formation region.

According to the present invention, a diamond semiconductor element such as a diamond Schottky barrier diode having a high withstand voltage, for example, a withstand voltage of 1 kV or more can be realized. According to the present invention, even when a reverse bias of 1 kV is applied, a diamond Schottky barrier diode having a performance with a leakage current density of 1 mA / cm ² or less can be realized. According to the present invention, a laminated structure in which a p + diamond layer and a p-diamond layer are epitaxially grown in this order on a high-quality semi-insulating single crystal diamond substrate, or p-diamond on a p + substrate made of conductive diamond. In a laminated structure in which layers are formed by epitaxial growth, focusing on the types of dislocations present in the p-diamond layer film, the region for forming the electrode of the element is determined. Can be obtained. A high-performance element can be obtained by paying attention to the density of specific dislocations without requiring a conventional technique for reducing the density of all dislocations.

Moreover, according to the present invention, a diamond Schottky barrier diode having a performance with a leakage current density of 1 mA / cm ² or less can be obtained even when a reverse bias of 1 kV is applied at 250 ° C.

Sectional drawing which shows the laminated structure of a Schottky barrier diode diamond semiconductor element. (A) is a horizontal type, (b) is a pseudo vertical type, and (c) is a diagram showing a vertical type. The figure explaining the correlation with a reverse bias and a leakage current density about the quality goods of an Example, and the inferior goods of a comparative example. The figure which shows the relationship between the density of all the dislocations, and a device operating characteristic about the quality goods of an Example, and the inferior goods of a comparative example. The figure which shows the relationship between the density of a 1st dislocation, and a device operating characteristic about the quality goods of an Example, and the inferior goods of a comparative example. The figure which shows the relationship between the density of the 2nd dislocation, and a device operating characteristic about the quality goods of an Example, and the inferior goods of a comparative example. The figure explaining the structure of the Schottky barrier diode diamond semiconductor element of a horizontal type | mold, and the kind of dislocation of an electrode formation area. (1) is an electrode formation region viewed from above, (2) is an X-ray topography image (g = −404), and (3) is an X-ray topography image (g = 113). The figure which shows the apparatus of reflection X-ray topography.

  Embodiments of the present invention will be described below.

  A typical example of the laminated structure of the diamond semiconductor element of the present invention has the structure shown in FIG. The diamond semiconductor element of FIG. 1A has a laminated structure of diamond in which a diamond single crystal substrate 1, a p + diamond layer 2, and a p- diamond layer 3 are sequentially formed. The diamond semiconductor element of FIG. 1A is provided with an electrode (Schottky electrode 4) in contact with the p-diamond layer 3 on the surface of the p-diamond layer 3, and spaced apart from the electrode by a predetermined distance. The p-diamond layer 3 has a structure in which an electrode (ohmic electrode 5) is provided on the surface thereof.

  As the substrate, a high-quality single crystal diamond substrate having a controlled low off-angle and off-direction and a low surface defect density is used. As the substrate, for example, an Ib type diamond substrate is used.

  The substrate is preferably polished with high accuracy by Skyf polishing. Skyf polishing is a method of polishing by applying diamond powder and oil as abrasives to a horizontally rotating cast iron disk. The substrate off angle control is preferably such that the <001> vector has an off angle of 1 ° to 5 ° with respect to the surface normal vector in the <110> ± 5 ° direction (see Patent Document 6). Further, the substrate can be polished by UV-assisted polishing instead of or in combination with Skyf polishing. The polished substrate preferably has a surface roughness of Ra of 0.1 nm or less.

The average dislocation density in the substrate is preferably, for example, 1.0 × 10 ^{2 to} 1.0 × 10 ⁶ / cm ² .

A p + diamond layer is epitaxially grown on the substrate by chemical vapor deposition (CVD). It is preferable that the p + diamond layer has a boron concentration for imparting electrical conductivity. Moreover, it is preferable that the thickness is such that a uniform doping concentration can be ensured inside the layer and a layer without distortion can be grown. Therefore, specifically, the thickness is preferably 0.5 μm or more and 50 μm or less, and the p + diamond layer has a boron concentration of 1.0 × 10 ²⁰ / cm ³ or more and 1.0 × 10 ²¹ / cm ³ or less. .

A p-diamond layer is epitaxially grown on the p + diamond layer by a chemical vapor synthesis method (CVD method). The p-diamond layer preferably has a thickness of 1 μm or more and 20 μm or less, and the boron concentration in the p-layer is 1.0 × 10 ¹⁶ or more and 1.0 × 10 ¹⁷ / cm ³ or less. This is because it is necessary to control the doping concentration and film thickness in order to reduce the leakage current density even when the Schottky barrier diode is operated at a high voltage.

  An ohmic electrode is provided on the surface of the p-diamond layer, and a Schottky electrode is provided at a predetermined distance from the ohmic electrode. The electrode forming method can be performed by vapor deposition.

Ti, Mo, Au, Pt, Al, or the like can be used as the material for the ohmic electrode. For example, Ti / Pt / Al can be used from the side closer to the surface of the p-diamond layer in a conventionally known laminated structure electrode. The size of the ohmic electrode is about 3 × 10 ^{4 to} 1.3 × 10 ⁵ μm ² .

As a material for the Schottky electrode, a metal such as Al, Au, Mo, or Pt, a tungsten carbide compound, or the like can be used. The size of the Schottky electrode is about 2 × 10 ⁴ to 1 × 10 ⁶ μm ² .

In the present invention, an X-ray topography image (g = 113) can be observed in an X-ray topography image (g = −404) under asymmetric Bragg reflection conditions in a region where a Schottky electrode or the like is formed on the surface of the p-diamond layer. Then, the electrodes are formed so that there are no dislocations that cannot be observed. The electrode formation region is a region on the p-surface (under the electrode) corresponding to the electrode installation position. In the electrode formation region, dislocations exist for dislocations other than dislocations that can be observed in an X-ray topography image (g = −404) under asymmetric Bragg reflection conditions but cannot be observed in an X-ray topography image (g = 113). However, since the device characteristics are not affected as will be described later, the dislocation density is preferably 1.0 × 10 ^{2 to} 2.0 × 10 ⁴ / cm ² .

  In the present invention, the crystal plane of the element substrate is {001} and does not depend on the presence or absence of the off angle and the magnitude relationship.

(Example)
The diamond semiconductor element of the Example of this invention is demonstrated below with reference to FIGS.
First, the manufacturing process of the diamond semiconductor element of a present Example and a comparative example is demonstrated.

(Preparation process of substrate)
A high-quality semi-insulating Ib type diamond single crystal (001) substrate with low surface defect density and controlled off-angle and off-direction was prepared as follows. Here, in the substrate off-angle control, the <001> vector has an off-angle of 3 ° with respect to the surface normal vector in the <110> direction. The average dislocation density in the substrate was about 1.0 × 10 ⁴ / cm ³ . The substrate was polished by Skyf polishing so that Ra (average roughness) was 0.1 nm or less.

(P + diamond layer forming process)
On the prepared Ib-type diamond single crystal (001) substrate, first, only hydrogen gas was introduced at 50 Torr and a total flow rate of 400 sccm, and the substrate surface was formed by plasma generated by microwave at a microwave power of 1200 W and a substrate temperature of 900 ° C. For 15 minutes. Next, the p + diamond layer 2 was epitaxially grown to a thickness of 1 μm by a chemical vapor synthesis method using plasma (microwave plasma CVD method) (see FIG. 1). As the source gas, methane and diborane were used, and the p + diamond layer 2 was synthesized by adjusting the ratio of boron to carbon (B / C) and the methane concentration in the source gas. B / C was 16000 ppm and the methane concentration was 0.6%. The boron concentration of the p + diamond layer was 1.0 × 10 ²⁰ / cm ³ .

(P-diamond layer forming step)
Next, the p-diamond layer 3 was epitaxially grown to a thickness of 17 μm by a chemical vapor synthesis method (microwave plasma CVD method) (see FIG. 1). In the p-diamond layer forming step, as in the p + diamond layer forming step, the source gas uses methane and diborane, and the ratio of boron to carbon (B / C) and the methane concentration in the source gas are adjusted. A p-diamond layer was synthesized. B / C was 150 ppm and the methane concentration was 0.1%. The boron concentration of the p-diamond layer was 1.0 × 10 ¹⁶ / cm ³ .

(Electrode formation process)
The prepared p-diamond layer was a device having no abnormally grown particles or hillocks and having a flat surface. A Schottky electrode 4 having a diameter of 200 μm and an ohmic electrode 5 having a diameter of 400 μm were deposited on the surface of the p-diamond layer. Pt was used as the Schottky electrode, and Ti / Pt / Al was used as the ohmic electrode. In the p-diamond layer, a region where the dislocation density satisfies the following conditions (1) and (2) was selected to form a Schottky electrode.

An electrode formation region in which a Schottky electrode is formed in contact with the layer in the p-diamond layer satisfies the following conditions (1) and (2).
(1) Dislocations that can be observed with an X-ray topography image of the diffraction vector [−404] under asymmetric Bragg reflection conditions but cannot be observed with an X-ray topography image of the diffraction vector [113] 1 ”) is not included in the p-diamond layer, that is, the first dislocation is zero.
(2) Dislocations other than dislocations that can be observed in the X-ray topography image of the diffraction vector [−404] under the asymmetric Bragg reflection condition and cannot be observed in the X-ray topography image of the diffraction vector [113] (hereinafter referred to as “No. The density of the “dislocation of 2” is 1.0 × 10 ^{2 to} 2.0 × 10 ⁴ / cm ² .

  Hereinafter, the conditions (1) and (2) will be described in detail.

In order to quantify the degree of achievement of the target value of the operating characteristics of the fabricated device, the leakage current density when reverse bias was applied was measured. The diamond semiconductor element of the present invention has a performance with a leakage current density of 1 mA / cm ² or less even when a reverse bias of 1 kV is applied.

FIG. 2 is a diagram showing the correlation between the reverse bias and the leakage current density in the non-defective product of the example and the defective product of the comparative example for explaining the diamond semiconductor element of the present example. A non-defective product has a performance with a leakage current density of 1 mA / cm ² or less even when a reverse bias of 1 kV is applied. What shows the correlation as shown by the solid line in FIG. 2 is a non-defective product. On the other hand, as shown by the broken line in FIG. 2, an element whose leakage current density exceeds 1 mA / cm ² before the reverse bias reaches 1 kV is regarded as a defective product.

  In the present invention, in order to evaluate only dislocations in the p-diamond layer, an X-ray topography image was taken under the condition of small-angle incident X-ray and Bragg reflection. Images can be taken with the apparatus illustrated in FIG. The wavelength of the X-ray used is 0.7 to 1.0 mm. {113} and {404} having a diamond structure and relatively high diffraction intensity and satisfying the Bragg reflection condition within the wavelength range used were used as diffraction surfaces of X-ray topography.

  In order to understand the present invention, FIG. 6 shows the structure of a diamond Schottky barrier diode and the types of dislocations present in the p-diamond layer. FIG. 6A is a schematic view of the electrode as viewed from above. FIG. 6B is an observation with an X-ray topography image (also referred to as “X-ray topography image (g = −404)”) of the diffraction vector [−404] corresponding to the region of FIG. It is an image that can be. FIG. 6 (3) can be observed with an X-ray topography image (also referred to as “X-ray topography image (g = 113)”) of the diffraction vector [113] corresponding to the region of FIG. 6 (1). It is a statue. As shown in FIG. 6, dislocations that can be observed with an X-ray topography image (g = −404) (see FIG. 6 (2)), dislocations that can be observed with an X-ray topography image (g = 113) ( 6 (3)), there are dislocations (see FIGS. 6 (2) and 6 (3)) that can be observed in both X-ray topography images, and the type of dislocation can be distinguished by the X-ray topography images. . In the present invention, a dislocation that can be observed in an X-ray topography image (g = −404) but cannot be observed in an X-ray topography image (g = 113) is referred to as a first dislocation. Further, other dislocations are referred to as second dislocations. In FIG. 6, the first dislocation is represented as A, and the second dislocation is represented as B. As will be described later, the first dislocation is a dislocation that affects the device characteristics, and the second dislocation is a dislocation that does not affect the device characteristics.

  The dislocation species and dislocation density of good and defective products were analyzed. The number of sample points analyzed is a total of 10 points including 3 non-defective products and 7 defective products. Table 1 shows the withstand voltage value and quality determination result of each sample.

  From the X-ray topograph, the dislocation density in the electrode formation region in contact with the Schottky electrode in the p-diamond layer of the device was determined.

FIG. 3 shows a graph comparing the dislocation density of the electrode formation region in contact with the Schottky electrode in the p-layer and the withstand voltage characteristics of the devices for the non-defective and defective products in Table 1. The horizontal axis in FIG. 3 represents the dislocation density in the electrode formation region in contact with the Schottky electrode in the p− layer. In FIG. 3, the dislocation density on the horizontal axis is “total number of dislocations / Schottky electrode area” (range 0.6 × 10 ⁴ / cm ^{2 to} 3.0 × 10 ⁴ / cm ² ). The vertical axis represents the withstand voltage (V) of the device, and more specifically, the reverse bias value when the leakage current density reaches 1 mA / cm ² . According to FIG. 3, the dislocation density is 1.3 × 10 ⁴ / cm ^{2 to} 1.9 × 10 ⁴ / cm ^{2 for} the non-defective product and 0.6 × 10 ⁴ / cm ^{2 to} 3 for the defective product. It was 2 × 10 ⁴ / cm ² . Referring to FIG. 3, one of the two electrodes having a dislocation density of 1.85 × 10 ⁴ / cm ² is a non-defective product, and the other is a defective product having a withstand voltage of 1 kV or less. From this, it is considered that dislocations can be divided into two types. That is, a dislocation (first dislocation) that adversely affects the device and a dislocation (second dislocation) that can ignore the influence on the operation.

FIG. 4 shows the density and device of the first dislocation (represented as a killer dislocation in the figure) in the Schottky electrode (electrode formation region in contact with the Schottky electrode in the p-layer) for the non-defective / defective products in Table 1. The graph which compared the withstand voltage characteristic of was shown. The horizontal axis in FIG. 4 represents the density of first dislocations in the Schottky electrode (electrode formation region in contact with the Schottky electrode in the p− layer). In FIG. 4, unlike FIG. 3, the dislocation density on the horizontal axis is “first number of dislocations / Schottky electrode area” (range 0 to 2.0 × 10 ⁴ / cm ² ). The vertical axis in FIG. 4 represents the withstand voltage (V) of the device, and more specifically, the reverse bias value when the leakage current density reaches 1 mA / cm ² . In addition, since the withstand voltage of 2 points out of 3 non-defective products is almost the same, circles are displayed overlapping in the graph. Here, the first dislocation is a dislocation that can be observed in the X-ray topography image of the diffraction vector [−404] and cannot be observed in the X-ray topography image of the diffraction vector [113]. Referring to FIG. 4, it can be seen that the non-defective products are distributed at positions where the dislocation density is zero, that is, “first dislocation number / Schottky electrode area” is zero. From this, it can be seen that if even one first dislocation exists, the withstand voltage characteristic of 1 kV cannot be achieved.

FIG. 5 shows the density of second dislocations (represented as non-killer dislocations in the figure) in the Schottky electrode (electrode formation region in contact with the Schottky electrode in the p-layer) for the non-defective / defective products in Table 1. The graph which compares the withstand voltage characteristic of the device is shown. The horizontal axis in FIG. 5 represents the density of second dislocations in the Schottky electrode (the electrode formation region in contact with the Schottky electrode in the p− layer). In FIG. 5, unlike FIG. 3 and FIG. 4, the dislocation density on the horizontal axis is “second dislocation number / Schottky electrode area” (range 0.3 × 10 ⁴ / cm ^{2 to} 1.9 × 10 ⁴ / cm ² ). The vertical axis in FIG. 5 represents the withstand voltage (V) of the device, and more specifically, the reverse bias value when the leakage current density reaches 1 mA / cm ² . Here, the second dislocation refers to a dislocation other than the first dislocation. FIG. 5 suggests that there is no positive correlation between the high dislocation density and the device operating characteristics. Further, in the non-defective product, the density of the second dislocation is about 1.4 × 10 ⁴ / cm ^{2 to} 2.0 × 10 ⁴ / cm ² , and even if the density is higher than that of the defective product, It can be seen that the withstand voltage is 1 kV or more. The distinction between a good product and a defective product does not greatly depend on the density of the second dislocations, but since the total dislocation density is preferably low, the density of the second dislocations in the good product is 1.0 × 10 ² / The range of cm ^{2 to} 2.0 × 10 ⁴ / cm ² is desirable.

From the above analysis results, in order to realize a diamond Schottky barrier diode with a withstand voltage of 1 kV, (a) the first dislocation can be observed by X-ray topography of the diffraction plane (−404), (b) the first If a dislocation of 1 exists in the Schottky electrode, a withstand voltage of 1 kV cannot be realized, and (c) the second dislocation does not disturb the withstand voltage operating characteristic of 1 kV, and its density is 1.0 × 10 ⁴ / It is derived that it is within the range of cm ^{2 to} 2.0 × 10 ⁴ / cm ² .

As in this example, the first dislocation that the electrode formation region in the p-diamond layer can be observed by X-ray topography (g = −404) but cannot be observed by the X-ray topography image (g = 113). The diamond Schottky barrier diode has no breakdown voltage and the second dislocation density is within the range of about 1.0 × 10 ² / cm ^{2 to} 2.0 × 10 ⁴ / cm ^2. Excellent characteristics of 1 kV or higher.

  In the above embodiments, a Schottky barrier diode having a lateral structure has been described as an example. However, in the diamond semiconductor device of the present invention, the withstand voltage characteristics depend on the crystal structure of the drift layer, and therefore FIG. Similar results can be obtained also in the pseudo-vertical / vertical structure as shown in (c).

  In the embodiment, an example using a Schottky electrode is shown, but the same effect can be obtained also in the ohmic electrode formation region. Further, although the example of the Schottky barrier diode has been described, the same effect can be obtained also in an electrode formation region in a semiconductor element such as various diodes such as a pn junction diode and a pin junction diode, a thyristor, and an FET.

  The examples shown in the embodiment and the like are described for easy understanding of the invention, and are not limited to this embodiment.

  The diamond semiconductor element of the present invention can be used as semiconductor elements such as various diodes such as Schottky diodes, pn junction diodes, and pin junction diodes, thyristors, and FETs. The diamond semiconductor element of the present invention has a withstand voltage characteristic of 1 kV or higher, or exhibits excellent characteristics under a high withstand environment. Therefore, the diamond semiconductor element has a medium withstand voltage and configuration such as an inverter mounted on a power device, for example, a home appliance. Useful for required devices.

DESCRIPTION OF SYMBOLS 1 Diamond substrate 2 p + diamond layer 3 p- diamond layer 4 Schottky electrode 5 Ohmic electrode 6 p + diamond substrate 10 X-ray diffraction recording computer 11 Sample 12 X-ray source 13 Monochromator

Claims (5)

A diamond semiconductor element comprising p + single crystal diamond, a p− layer made of a diamond semiconductor formed on the p + single crystal diamond, and an electrode formed on an electrode formation region of the p− layer,
In the p-layer of the electrode formation region, the number of first dislocations that can be observed in the X-ray topography image of the diffraction vector [−404] but cannot be observed in the X-ray topography image of the diffraction vector [113] is zero. And a second dislocation other than the first dislocation is present at a dislocation density of 1.0 × 10 ^{2 to} 2.0 × 10 ⁴ / cm ² .   The diamond semiconductor element according to claim 1, wherein the electrode is a Schottky electrode or an ohmic electrode.   2. The diamond semiconductor according to claim 1, wherein the p + single crystal diamond is a p + layer made of conductive diamond formed on a semi-insulating single crystal diamond substrate or a p + substrate made of conductive diamond. element.   2. The diamond semiconductor device according to claim 1, wherein the p + single crystal diamond is a contact layer, and the p− layer is a drift layer.   The diamond semiconductor element according to any one of claims 1 to 4, wherein the diamond semiconductor element is a Schottky diode, a pn junction diode, or a pin junction diode.

Images