JPH09211084A - Method and device for inspecting semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and nondestructively judge whether or not the pn joint is at the specified position by detecting a photoelectric current flowing between both terminals of the pn joint when the surface of a semiconductor substrate is irradiated with a light. SOLUTION: A laser light 27 emitted from a laser 26 is reflected on a rotatable mirror 28 such as galvano-mirror or polygon mirror, etc., and further it is directed to a semiconductor device on a rotary stage 21 which is controlled by a controlle 22, through an f-θlens 29 and is reflected on the surface thereof, then it passes through an optical fiber guide line 30 where a number of optical fibers are arranged one-dimensionally and their linear tip end parts are all parallel to the scanning direction of the laser light 27, and it enters a photomultiplier 31. The output electric signal from the photomultiplier 31 and the output signal from an ammeter 25 are supplied to a computer 32 for signal processing, thereby inspecting the position of the pn joint on a bevel 10 of the semiconductor device to be inspected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device inspection method and inspection device, and is suitable for application to inspection of thyristors and various other semiconductor devices.

[0002]

2. Description of the Related Art A thyristor, which is widely used as a power semiconductor device, is conventionally manufactured by a method shown in FIG. That is, in this conventional method of manufacturing a thyristor, as shown in FIGS. 18A and 18B, first, for example, boron (B), gallium (Ga), aluminum (on the both main surfaces of the n-type silicon (Si) substrate 101. By diffusing a p-type impurity such as Al), a p-type Si layer 102 serving as an anode layer and a p-type Si layer 103 forming a part of the base layer are formed.

Next, as shown in FIG. 18C, by selectively diffusing an n-type impurity such as phosphorus (P) into the p-type Si layer 103, an n-type Si that is a cathode layer is formed.
The layer 104 is formed. Next, after forming a metal film such as an aluminum (Al) film on the entire surface by a vacuum deposition method or a sputtering method, the metal film is patterned into a predetermined shape by etching, and as shown in FIG.
A cathode electrode 105 having a ring-shaped planar shape is formed on the type Si layer 104, and a gate electrode 106 having a circular planar shape is formed on the p-type Si layer 103 in a portion surrounded by the n-type Si layer 104. To do. Similarly, the anode electrode 107 is formed on the p-type Si layer 102.

Next, as shown in FIG. 18E, the molybdenum (Mo) plate 108, which serves as a support, is formed on the anode electrode 107.
Weld to. Next, as shown in FIG. 18F, the end faces of the n-type Si substrate 101 and the p-type Si layers 102 and 103 are processed by a sandblast method, a polishing method, or the like, so that the main surface of the n-type Si substrate 101 is processed. To form an inclined surface. Reference numerals 109 and 110 are thus p
An inclined surface (hereinafter referred to as “bevel surface”) formed on the mold Si layer 103 and the like is shown.

Next, the bevel surface 109 is wet-etched using a mixed solution of hydrofluoric acid and nitric acid to remove the surface layer of the bevel surface 109 having defects introduced during processing. Next, in order to stabilize the bevel surface 109, silicone rubber (not shown) is applied onto the bevel surface 109. After that, the thyristor pellet manufactured as described above is inserted into, for example, a flat package (not shown),
The package is sealed to complete the desired thyristor.

In the thyristor as described above, in order to secure the breakdown voltage, the pn junction between the p-type Si layer 103 and the n-type Si substrate 101 is located on the bevel surface 109, and the n-type Si substrate 101 is located. And p-type Si layer 10
The pn junction with 2 must be located on the bevel surface 110. Therefore, after manufacturing the thyristor, the bevel surface 10
It is necessary to check whether this pn junction is located on 9,110. Conventionally, the position of the pn junction has been detected by forming the bevel surfaces 109 and 110 and then chemically treating the thyristor pellet.
That is, after forming the beveled surfaces 109 and 110, the thyristor pellets are cut, and the cut surfaces are polished,
By performing a chemical treatment with hydrofluoric acid or the like to color the pn junction of the cut surface, the pn on the bevel surface 109, 110 is colored.
I was checking the position of the joint.

[0007]

However, in the above-described conventional method for inspecting the position of the pn junction, since it is necessary to cut the thyristor pellet, it goes without saying that the bevel surface 109,
It was not possible to check whether the pn junction was located on 110. Therefore, the bevel surfaces 109 and 110
A defective thyristor pellet without a pn junction on top may be sent to the assembly process, resulting in a poor thyristor manufacturing yield. Therefore, an object of the present invention is to provide a semiconductor device inspection method capable of non-destructively and simply inspecting whether or not a pn junction is located at a predetermined position, and a semiconductor device which can be used for such an inspection. To provide an inspection device.

[0008]

In order to achieve the above object, the first invention of the present invention is a semiconductor having a pn junction in a semiconductor substrate, and the pn junction is located on the surface of the semiconductor substrate. A method of inspecting a device, wherein the position of the pn junction is inspected by detecting a photocurrent flowing between both terminals of the pn junction when the surface of the semiconductor substrate is irradiated with light. Is.

In the first aspect of the present invention, typically, the semiconductor substrate has an inclined surface inclined with respect to its main surface, and the inclined surface is irradiated with light by irradiating the inclined surface. It is inspected whether or not the pn junction is located at. More specifically, the photocurrent generated by irradiating the inclined surface with light is detected to detect the pn on the inclined surface.
Inspect to see if the splice is in place. A typical example of such a semiconductor device is a thyristor having a beveled surface. In the first aspect of the present invention, the light with which the surface of the semiconductor substrate is irradiated may have basically any wavelength as long as it can generate electron-hole pairs in the semiconductor substrate. It is typically infrared light. Further, this light is preferably laser light.

A semiconductor device inspection apparatus according to a second aspect of the present invention irradiates a sample table on which a semiconductor device to be inspected is mounted and a semiconductor device mounted on the sample table with light. Of the light source, a photocurrent detecting unit for detecting a photocurrent flowing when the light is applied to the semiconductor device, and a light detecting unit for detecting a reflected light when the light is applied to the semiconductor device. It is characterized by having.

In the second aspect of the present invention, the semiconductor device inspection apparatus preferably further comprises a scanning means for scanning the light on the semiconductor device mounted on the sample stage. In the second aspect of the present invention, preferably, the semiconductor device inspection apparatus further includes a signal processing unit that is supplied with the output signal of the photocurrent detection unit and the output signal of the photodetection unit and performs predetermined signal processing. Have. In the second aspect of the present invention, typically, the sample stage is configured to be rotatable about its central axis. In the second aspect of the present invention, the light source is preferably a laser. For this laser,
For example, an infrared laser such as a helium (He) -neon (Ne) laser is used.

In the second aspect of the present invention, the photocurrent detecting means typically comprises a constant voltage source and an ammeter.
In the second aspect of the present invention, the photodetector is, for example, a one-dimensional photodetector. As the one-dimensional photodetector, specifically, a CCD line sensor, a one-dimensional photodiode array, or the like is used. In the second aspect of the present invention, the photodetector means may be a photomultiplier tube in which reflected light is introduced through a plurality of optical transmission lines that are one-dimensionally arranged so that their one end faces are adjacent to each other. Good.
This optical transmission line is specifically an optical fiber, for example.

In the second aspect of the present invention, the scanning means typically comprises a rotatable reflecting mirror and a lens. As the reflecting mirror, specifically, a galvano mirror, a polygon mirror, or the like is used. Further, as the lens, a so-called f-θ lens is preferably used.
In the second aspect of the present invention, the signal processing means is a computer. In one embodiment of the second invention of the present invention, the light source and the light detection means are integrally formed.

In the present invention, the semiconductor device may be basically any device as long as the pn junction is located on the surface of the semiconductor substrate. In addition, static induction transistor (SI
T) or the like. The thyristor includes various types, including a gate turn-off thyristor (GTO).

[0015]

Embodiments of the present invention will be described below with reference to the drawings. First, a thyristor which is an inspection target in the following embodiments will be described. This thyristor is manufactured in the same manner as the conventional thyristor manufacturing method shown in FIG. 1 and 2 show this thyristor, which shows a state immediately after the end of processing for forming the bevel surface. Here, FIG. 1 is a sectional view and FIG. 2 is a perspective view. 1 and 2, reference numeral 1 is an n-type Si substrate, 2 and 3 are p-type Si layers formed in the n-type Si substrate 1, and 4 is n formed in the p-type Si layer 3.
Type Si layer, 5 is a cathode electrode formed on the n type Si layer 4, and 6 is p type Si in a portion surrounded by the n type Si layer 4.
A gate electrode formed on the layer 3, 7 is an anode electrode formed on the p-type Si layer 2, and 8 is a Mo plate welded to the anode electrode 7. Reference numerals 9 and 10 indicate bevel surfaces.

Next, the principle of the present invention will be described.
As shown in FIG. 3, a constant voltage source 11 and an ammeter 12 are connected between the gate electrode 6 and the Mo plate 8 of the thyristor shown in FIGS. 1 and 2. At this time, the positive terminal of the constant voltage source 11 is connected to the Mo plate 8 and the negative terminal is connected to the gate electrode 6. As a result, the pn junction between the p-type Si layer 3 and the n-type Si substrate 1 is reversely biased. Sign 1
Reference numeral 3 indicates a depletion layer of this pn junction. As shown in FIG.
Now, a DC voltage of, for example, about several tens of volts is applied between the gate electrode 6 of the thyristor and the Mo plate 8 by the constant voltage source 11, and in this state, the bevel surface 9 is irradiated with, for example, infrared laser light 14. At this time, it is assumed that the bevel surface 9 has a pn
If the junction is located, an electron-hole pair is generated in the depletion layer 13 of the pn junction (in FIG. 3, electrons are indicated by black circles, holes are indicated by white circles). The electrons of the electron-hole pairs flow to the Mo plate 8 and the holes flow to the gate electrode 6, and the current resulting from this, that is, the photocurrent, flows to the ammeter 12 for detection. On the other hand, if the pn junction is not located on the bevel surface 9, no electron-hole pair is generated in the depletion layer 13 of the pn junction, and thus no photocurrent flows in the ammeter 12.

From the above, whether the pn junction is located on the bevel surface 9 depends on whether the bevel surface 9 is irradiated with the laser light 14 and the photocurrent is detected by the ammeter 12 at that time. It turns out that it can be inspected. Similarly, for the bevel surface 10 as well, the negative terminal of the constant voltage source 11 is connected to the Mo plate 8, the positive terminal is connected to the gate electrode 6, and the photocurrent is measured by the same method as above. It is possible to inspect whether or not the pn junction is located on the bevel surface 10. Since the inspection is performed by the photocurrent flowing by the irradiation of the laser light 14 as described above, it is desirable to perform the irradiation of the laser light 14 in a box where other light does not enter.

It has been experimentally confirmed that a photocurrent flows by the irradiation of the laser light 14 as described above. That is, as shown in FIG. 4, a voltage of 5 V is applied between the p-type Si layer 2 and the p-type Si layer 3 so that the p-type Si layer 2 side becomes positive, and both ends of the resistance of 1 kΩ at that time are applied. While measuring the voltage between them with the voltmeter 15, the He-Ne laser 16
When the laser light 14 according to Example 1 was shaken before and after the pn junction on the bevel surface 9, a waveform as shown in FIG. 5 was obtained (however, this waveform is a differential waveform of the obtained voltage).
This shows that a photocurrent flows by the irradiation of the laser light 14. Based on the above, the embodiment of the present invention will be specifically described.

FIG. 6 shows a semiconductor device inspection apparatus according to the first embodiment of the present invention. As shown in FIG. 6, in the semiconductor device inspection apparatus according to the first embodiment,
A semiconductor device to be inspected is mounted on a rotary stage 21 which is rotatable around its central axis. The rotation of the rotary stage 21 is controlled by the rotary stage controller 22. The semiconductor device mounted on the rotary stage 21 includes an electrode 2
3 are connected. A constant voltage source 24 and an ammeter 2 are provided between the electrode 23 and the rotary stage 21.
5 is connected. Then, the constant voltage source 24 can apply a DC voltage to the semiconductor device, and
The ammeter 25 can detect the photocurrent flowing in this circuit.

This semiconductor device inspection apparatus has a laser 26 for generating infrared laser light. As the laser 26, specifically, for example, a He-Ne laser is used. A laser beam 27 emitted from the laser 26 is reflected by a rotatable mirror 28 such as a galvano mirror or a polygon mirror, and then, a semiconductor device mounted on the rotary stage 21 via an f-θ lens 29. It is designed to be illuminated. The laser light 27 can be linearly scanned on the semiconductor device by the rotation of the mirror 28.

The laser light 27 applied to the semiconductor device on the rotary stage 21 as described above is reflected by the surface thereof and then enters the photomultiplier tube 31 through the optical fiber guide line 30. here,
The optical fiber guide line 30 is formed by arranging a large number of optical fibers one-dimensionally so that their one end surfaces are adjacent to each other. This optical fiber guideline 30
The linear tip portion of is preferably arranged so as to be substantially parallel to the scanning direction of the laser light 27 on the semiconductor device. As described below, this fiber optic guideline 30
Is for measuring the profile of the surface shape of the thyristor. The output electric signal of the photomultiplier tube 31 and the output electric signal of the ammeter 25 are supplied to the signal processing computer 32. Then, the signal processing computer 32 performs signal processing as described later.

Next, a method of inspecting a semiconductor device by using the semiconductor device inspection device configured as described above will be described. Here, considering the case of inspecting the thyristor pellet shown in FIGS. 1 and 2, it is inspected whether or not the pn junction is located on the bevel surfaces 9 and 10 of the thyristor pellet. First, the thyristor pellet shown in FIGS. 1 and 2 in which the bevel surfaces 9 and 10 have been formed is placed on the rotary stage 21 of the semiconductor device inspection apparatus shown in FIG. Next, the electrode 23 is connected to the gate electrode 6 of this thyristor pellet. As a result, the pn junction between the p-type Si layer 3 and the n-type Si substrate 1 is reverse biased.

Next, in this state, the laser beam 27 emitted from the laser 26 is irradiated onto the bevel surface 9 of the thyristor pellet through the mirror 28 and the f-θ lens 29, and the radius of the thyristor is rotated by the rotation of the mirror 28. Scan in the direction. At this time, according to the principle described above, the bevel surface 9
Depending on whether or not the pn junction is located above, the ammeter 2
Photocurrent may or may not flow in 5. On the other hand, the reflected light when the laser light 27 is incident on the surface of the thyristor pellet is incident on the photomultiplier tube 31 through the optical fiber guideline 30.

The scanning of the laser beam 27 in the radial direction of the thyristor pellet as described above is performed by the rotary stage 21.
Is performed 360 times in total, for example, while rotating by 1 ° (see FIG. 7). Now, as shown in FIG. 8, the X axis is parallel to the bevel surface 9 in the radial direction of the thyristor pellet.
FIG. 9 shows changes in the X-axis direction of the photocurrent detected by the ammeter 25 at this time for each scanning of the laser light 27. In FIG. 9, n is a number indicating how many times the laser light 27 is scanned, and takes a value of 1 to 360. Further, FIG. 10 illustrates changes in the output of the photomultiplier tube 31 in the x-axis direction for each scanning of the laser light 27.

As shown in FIG. 9, when the bevel surface 9 is irradiated with the laser light 27, the photocurrent flowing through the ammeter 25 is
It takes a maximum value near the interface of the pn junction. On the other hand, FIG.
As shown in 0, the output obtained from the photomultiplier tube 31 when the bevel surface 9 is irradiated with the laser light 27 is X = 0.
From X to some value of X is almost constant, but beyond that, it begins to decrease. Here, X = 0 corresponds to the uppermost portion of the bevel surface 9, and the place where the output starts to decrease corresponds to the lowermost portion of the bevel surface 9 or the uppermost portion of the bevel surface 10, that is, the corner C shown in FIG.

In the signal processing computer 32,
The X coordinate of the pn junction in FIG. 9 and the X coordinate of the corner C in FIG. 10 are compared, and as a result, the p coordinate in FIG.
If the X-coordinate of the n-junction is smaller than the X-coordinate of the corner C in FIG. 10, that is, if the position of the pn-junction in FIG. 9 is in front of the position of the corner C in FIG. Is determined to be located. Conversely, if the X coordinate of the pn junction in FIG. 9 is larger than the X coordinate of the corner C in FIG. 10, that is,
If the position of the pn junction in FIG. 9 is not in front of the position of the corner C in FIG.
It is determined that it is not located above. The result is stored in a memory (not shown) in the signal processing computer 32 for each angular direction of the rotary stage 21.

As described above, the X coordinate of the pn junction in FIG. 9 and the X coordinate of the corner C in FIG. 10 are compared for each scanning of the laser light 27. At the same time,
The position of the pn junction on the bevel surface 10 is determined by the same method. And as a result, one of the thyristor pellets is
When it is determined that the pn junction is located on the bevel surfaces 9 and 10 for 360 angular directions that differ by °, the thyristor pellet is regarded as a non-defective product and is sent to the next process to bevel surfaces 9 and 10. Silicone rubber is applied for stabilization, insertion into a flat package, encapsulation, etc. to complete the desired thyristor. In contrast,
If it is determined that the pn junction is not located on the bevel surfaces 9 and 10 even with respect to one of the 360 thyristor pellets in the angular direction, the thyristor pellet is regarded as a defective product, and the subsequent inspection is performed. No, collect it.

As described above, according to the first embodiment, whether or not the pn junction is located on the bevel surfaces 9 and 10 of the thyristor pellet can be inspected nondestructively and easily. Since the inspection can be performed nondestructively in this way, all the thyristor pellets can be inspected. Therefore, the manufacturing yield of the thyristor can be significantly improved as compared with the conventional one.

Next, a second embodiment of the present invention will be described. In the second embodiment, the thyristor pellets are inspected using a semiconductor device inspection apparatus different from that shown in FIG. FIG. 11 shows a semiconductor device inspection apparatus according to the second embodiment. As shown in FIG. 11, in the semiconductor device inspection apparatus according to the second embodiment, instead of the optical fiber guide line 30 and the photomultiplier tube 31 in the semiconductor device inspection apparatus according to the first embodiment, a lens 33 and The CCD line sensor 34 is used. In this case, the light reflected by the surface of the thyristor pellet placed on the rotary stage 21 passes through the lens 33 and the CCD line sensor 34.
Has been introduced.

Since the semiconductor device inspection apparatus according to the second embodiment is the same as the semiconductor device inspection apparatus according to the first embodiment except for the above, the description thereof will be omitted.
The thyristor inspection method using the semiconductor device inspection apparatus according to the second embodiment is also the same as the thyristor inspection method using the semiconductor device inspection apparatus according to the first embodiment, and a description thereof will be omitted. To do. Also in the second embodiment, the same advantages as in the first embodiment can be obtained.

Next explained is the third embodiment of the invention. As shown in FIG. 12, in the third embodiment, the thyristor pellet is inspected using the displacement sensor 35 in which the laser 26, the CCD line sensor 34 and the lens 33 are integrated. That is, the thyristor pellet is placed on a rotary stage (not shown),
1 and 2 while irradiating the laser beam 27 emitted from the laser 26 of the displacement sensor 35 in a state where the pn junction between the p-type Si layer 3 and the n-type Si substrate 1 is reverse biased.
3 and FIG. 14, the displacement sensor 35 is moved in parallel to the bevel surface 9 in the radial direction of the thyristor pellet. The reflected light obtained at this time is reflected by the lens 33.
It is made incident on the CCD line sensor 34 via the and detected.

FIGS. 15A and 15B show changes in the height (Y-axis direction) in the direction perpendicular to the bevel surface 9 at this time in the X-axis direction and the second-order differential value of this height in the X-axis direction. Show changes. Further, FIG. 15C shows that at this time, the ammeter 2
5 shows a change in the photocurrent detected in No. 5 in the X-axis direction. However, here, the coordinate axes are arranged as shown in FIG. Areas I, II, and III in FIG. 15 correspond to the states shown in FIGS. 12, 13, and 14, respectively. As shown in FIG. 15B, the second derivative of height is X = X
Take a peak at ₁ . This peak position corresponds to the corner C shown in FIG. On the other hand, as shown in FIG. 15C, the photocurrent detected by the ammeter 25 has a peak at X = X ₂ . This peak position corresponds to the position of the pn junction.

In this case, the position of the peak of the photocurrent in FIG. 15C, that is, the X coordinate X ₂ of the position of the pn junction is the peak position of the second derivative of the height in FIG. 15B, that is, the X coordinate of the position of the corner C. If it is larger than X ₁ , it means that the pn junction is located on the bevel surface 9. On the contrary, if X ₂ is smaller than X ₁ , the pn on the bevel surface 9
The joint is not located. Then, for example, as in the first embodiment, the rotary stage is
Bevel surface 9 in each angle direction while rotating by °
Determine if the pn junction is located above. Also,
By the same method, it is determined whether or not the pn junction is located on the bevel surface 10. Thus, it is determined whether or not the thyristor pellet is a good product as in the first embodiment. Also according to this third embodiment, the first
The same advantages as those of the embodiment can be obtained.

The embodiments of the present invention have been specifically described above, but the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the technical idea of the present invention. For example, in the above-described first, second, and third embodiments, the thyristor pellets are inspected in 360 angular directions while rotating the rotary stage by 1 °, but the present invention is not limited to this. Alternatively, the inspection may be performed for a different number of angular directions. In addition, the above-mentioned first, second and third
In the embodiment described above, the case where the present invention is applied to the inspection of thyristor pellets has been described. However, the present invention can be applied to a semiconductor substrate 51 such as a Si substrate as shown in FIGS. In a semiconductor device in which the conductive type diffusion layer 52 is formed, it can be applied when inspecting whether or not the pn junction between the semiconductor substrate 51 and the diffusion layer 52 is located at a predetermined position.

[0035]

As described above, according to the method for inspecting a semiconductor device of the present invention, the pn is detected by detecting the photocurrent flowing between both terminals of the pn junction when the surface of the semiconductor substrate is irradiated with light. Since the position of the junction is inspected, whether or not the pn junction is located at a predetermined position can be inspected nondestructively and easily. Further, according to the semiconductor device inspection apparatus of the present invention, such a semiconductor device can be easily inspected.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a thyristor which is an object of inspection in an embodiment of the present invention.

FIG. 2 is a perspective view showing a thyristor which is an object to be inspected in the embodiment of the present invention.

FIG. 3 is a schematic diagram for explaining the principle of the present invention.

FIG. 4 is a schematic diagram for explaining that a photocurrent flows by irradiating a thyristor pellet with laser light.

FIG. 5 is a graph showing measurement results of photocurrent.

FIG. 6 is a schematic diagram showing a semiconductor device inspection apparatus used in the first embodiment of the present invention.

FIG. 7 is a schematic diagram for explaining the thyristor inspection method according to the first embodiment of the present invention.

FIG. 8 is a schematic diagram for explaining the thyristor inspection method according to the first embodiment of the present invention.

FIG. 9 is a schematic diagram for explaining the thyristor inspection method according to the first embodiment of the present invention.

FIG. 10 is a schematic diagram for explaining the thyristor inspection method according to the first embodiment of the present invention.

FIG. 11 is a schematic diagram showing a semiconductor device inspection apparatus used in a second embodiment of the present invention.

FIG. 12 is a schematic diagram for explaining a thyristor inspection method according to a third embodiment of the present invention.

FIG. 13 is a schematic diagram for explaining the thyristor inspection method according to the third embodiment of the present invention.

FIG. 14 is a schematic diagram for explaining a thyristor inspection method according to a third embodiment of the present invention.

FIG. 15 is a schematic diagram for explaining a thyristor inspection method according to a third embodiment of the present invention.

FIG. 16 is a plan view for explaining another embodiment of the present invention.

17 is a sectional view taken along the line AA of FIG.

FIG. 18 is a cross-sectional view for explaining the method of manufacturing a thyristor.

[Explanation of symbols]

 1 n-type Si substrate 2, 3 p-type Si layer 4 n-type Si layer 5 cathode electrode 6 gate electrode 7 anode electrode 9, 10 bevel surface 11, 24 constant voltage source 12, 25 ammeter 13 depletion layer 14, 27 laser light 29 f-θ lens 30 optical fiber guide line 31 photomultiplier tube 34 CCD line sensor 35 displacement sensor

Claims (17)

[Claims] 1. A semiconductor substrate having a pn junction,
A method for inspecting a semiconductor device in which an n-junction is located on the surface of the semiconductor substrate, wherein the p
A method of inspecting a semiconductor device, wherein the position of the pn junction is inspected by detecting a photocurrent flowing between both terminals of the n junction. 2. The semiconductor substrate has an inclined surface inclined with respect to its main surface, and whether the pn junction is located on this inclined surface by irradiating the inclined surface with the light. 2. The method for inspecting a semiconductor device according to claim 1, wherein the inspection is performed. 3. The method for inspecting a semiconductor device according to claim 1, wherein the light is infrared light. 4. The method for inspecting a semiconductor device according to claim 1, wherein the light is laser light. 5. The method for inspecting a semiconductor device according to claim 1, wherein the semiconductor device is a thyristor. 6. A sample table for mounting a semiconductor device to be inspected, a light source for irradiating the semiconductor device mounted on the sample table with light, and the light for the semiconductor device. A semiconductor having photocurrent detection means for detecting a photocurrent flowing when irradiated, and light detection means for detecting reflected light when the light is applied to the semiconductor device. Equipment inspection equipment. 7. The semiconductor device inspection apparatus according to claim 6, further comprising scanning means for scanning the light on the semiconductor device mounted on the sample stage. 8. The semiconductor device according to claim 6, further comprising a signal processing unit that is supplied with the output signal of the photocurrent detecting unit and the output signal of the photodetecting unit and performs predetermined signal processing. Inspection equipment. 9. The inspection apparatus for a semiconductor device according to claim 6, wherein the sample stage is configured to be rotatable around its center axis. 10. The semiconductor device inspection apparatus according to claim 6, wherein the light source is a laser. 11. The semiconductor device inspection apparatus according to claim 6, wherein said photocurrent detection means comprises a constant voltage source and an ammeter. 12. The inspection apparatus for a semiconductor device according to claim 6, wherein the photodetection means is a one-dimensional photodetector. 13. The photodetector means is a photomultiplier tube into which the reflected light is introduced through a plurality of optical transmission lines which are one-dimensionally arranged so that one end faces thereof are adjacent to each other. 7. The semiconductor device inspection apparatus according to claim 6. 14. The semiconductor device inspection apparatus according to claim 13, wherein the optical transmission line is an optical fiber. 15. The inspection apparatus for a semiconductor device according to claim 7, wherein said scanning means comprises a rotatable reflecting mirror and a lens. 16. The semiconductor device inspection apparatus according to claim 8, wherein said signal processing means is a computer. 17. The semiconductor device inspection apparatus according to claim 6, wherein the light source and the light detection means are integrally formed.