KR20130005748A - Apparatus and method for inspecting void of multi-junction semiconductor - Google Patents

Abstract

PURPOSE: An apparatus and a method for inspecting voids of a multi-junction semiconductor are provided to detect voids in real time by using terahertz wave having a short pulse width. CONSTITUTION: A light source(10) generates terahertz light. The light source irradiates the light to a multijunction semiconductor. A collimated light irradiation part(20) is arranged between the light source and the multijunction semiconductor to irradiate uniformly the light to the multijunction semiconductor. A light connection part(30) is arranged in the lower part of the multijunction semiconductor. [Reference numerals] (70) Image signal generating part; (80) Image signal analyzing part

Description

Apparatus and method for inspecting void of multi-junction semiconductor}

The present invention relates to a void inspection apparatus and method for a multi-junction semiconductor. More specifically, the present invention relates to a pore inspection apparatus and method for a multi-junction semiconductor capable of inspecting a pore for a multi-junction semiconductor in real time in the manufacturing process of the multi-junction semiconductor using electromagnetic waves.

Recently, the demand for multi-junction semiconductors, which are easy to implement, has been increasing rapidly according to the development of semiconductor technology. However, in the case of most multi-junction semiconductors, a plurality of wafers are bonded by an adhesive to form a laminated structure. In the manufacturing process, voids are generated in the bonding process between the wafers due to the use of the adhesive, thereby decreasing the adhesive strength between the wafers and causing a thermal problem of the multi-junction semiconductor due to the decrease in thermal conductivity.

Therefore, in order to respond quickly to these problems, various apparatuses for inspecting the presence of voids in a multi-junction semiconductor have been developed.

1 is a reference diagram of a conventional multi-junction semiconductor void inspection apparatus.

In general, the method of inspecting the voids of the multi-junction semiconductor may be classified into an ultrasonic method and an infrared method. In the case of the ultrasonic method, as shown in FIG. After the junction semiconductors are placed, the presence or absence of voids in the multi-junction semiconductors is inspected, and after the inspection, a separate drying process for the multi-junction semiconductors is required or the multi-junction semiconductors that have been inspected must be discarded. .

In addition, in the case of ultrasonic waves, it is impossible to inspect the air layer formed by the voids or the air layer formed due to the multi-junction semiconductor structure due to the absence of permeability to air. When the pore inspection is performed by the reflection method, which is not easy to locate and uses the ultrasonic waves reflected from the multi-junction semiconductor, the structure of the multi-junction semiconductor is hardly understood and thus there is an inefficient problem.

In addition, as shown in (b) of FIG. 1, the method using the infrared ray has an advantage that real-time inspection is possible when compared with the method using the ultrasonic wave, but the transmission using the amount of light transmitted through the multi-junction semiconductor as a sample. Since the inspection of the porosity of the multi-junction semiconductor can be performed only by the method, only the presence or absence of the pore of the multi-junction semiconductor can be confirmed, but the location of the pore is impossible.

The present invention has been made to solve the above problems, using a terahertz wave, which is a kind of electromagnetic wave having a short pulse width in real time, the inspection of the pore of the multi-junction semiconductor that can determine the presence or absence of the pore and the position of the pore for the multi-junction semiconductor It is an object to provide an apparatus and method.

In addition, an object of the present invention is to provide an apparatus and method for inspecting a pore of a multi-junction semiconductor capable of determining the presence or absence of a pore and the position of the pore with respect to the multi-junction semiconductor by a transmission method or a reflection method using the transmission and reflection characteristics of the terahertz wave. It is done.

In the pore inspection apparatus of a multi-junction semiconductor according to a preferred embodiment of the present invention for achieving the above object, in the pore inspection apparatus of a multi-junction semiconductor, a light source for generating terahertz light and irradiating to the multi-junction semiconductor side disposed below ; A parallel light irradiation unit disposed between the light source and the multi-junction semiconductor to uniformly irradiate terahertz light emitted from the light source to the multi-junction semiconductor side; An optical focusing unit disposed under the multi-junction semiconductor to focus terahertz light passing through the multi-junction semiconductor; And a first light detector configured to detect the terahertz light focused by the light focusing unit.

In addition, a method of inspecting a pore of a multi-junction semiconductor according to a preferred embodiment of the present invention, the method of inspecting a pore of a multi-junction semiconductor, comprising: (a) generating terahertz light and irradiating the multi-junction semiconductor side; (b) concentrating terahertz light passing through the multi-junction semiconductor; (c) detecting the focused terahertz light; And (d) using the detected terahertz optical signal to determine the presence or absence of pores of the multi-junction semiconductor and the position of the pores.

In addition, the method of inspecting the porosity of a multi-junction semiconductor according to another preferred embodiment of the present invention, comprising: (a) generating terahertz light and irradiating the multi-junction semiconductor side; (b) distributing terahertz light reflected from the multi-junction semiconductor; (c) detecting the distributed terahertz light; And (d) using the detected terahertz light to determine the presence or absence of pores of the multi-junction semiconductor and the location of the pores.

According to the present invention, since the inspection of the multi-junction semiconductor is performed using the terahertz wave, underwater inspection is not necessary, so that the inspection of the air gap is possible since the entire inspection of the multi-junction semiconductor is possible in real time and the permeation of air is possible. It also has a possible effect.

In addition, according to the present invention, since the inspection of the multi-junction semiconductor can be performed by using both the transmission method and the reflection method using the transmission and reflection properties of the terahertz wave medium, the presence or absence of air gaps and the positions of the gaps in the multi-junction semiconductor. It is easy to grasp the effect.

1 is a reference diagram for a conventional multi-junction semiconductor void inspection device,
2 is a reference diagram of an air gap inspection apparatus of a multi-junction semiconductor according to a preferred embodiment of the present invention;
3 is a reference diagram of a terahertz optical signal detected by the first photodetector of FIG. 2;
4 is a reference diagram for a terahertz optical signal detected by the second photodetector of FIG. 2;
5 is a reference diagram of an image signal for a multi-junction semiconductor generated by the image signal generator of FIG. 2;
6 is a reference graph of a terahertz optical signal collected in the image signal generator of FIG. 2;
7 is a comparison diagram of a multi-junction semiconductor image according to a conventional method and a multi-junction semiconductor image according to the present invention;
FIG. 8 is a comparison diagram of images of multiple junction semiconductors generated by the image signal generator of FIG. 2;
9 to 11 are reference diagrams for an air gap inspection apparatus of a multi-junction semiconductor according to still another preferred embodiment of the present invention.
12 is a flowchart of a method for inspecting voids in a multi-junction semiconductor according to a preferred embodiment of the present invention, and
13 is a flow chart of a method for inspecting voids in a multi-junction semiconductor according to another preferred embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, if it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, it will be described below in the preferred embodiment of the present invention, but the technical idea of the present invention is not limited to this or may be practiced by those skilled in the art.

2 is a reference diagram of an apparatus for inspecting a pore of a multi-junction semiconductor according to a preferred embodiment of the present invention.

As shown in FIG. 2, the air gap inspection apparatus 1 of the multi-junction semiconductor according to an exemplary embodiment of the present invention may include a light source 10, a parallel light irradiation unit 20, a light focusing unit 30, and a first light detection unit ( 40, a light distributor 50, a second light detector 60, an image signal generator 70, and an image signal analyzer 80.

The light source 10 generates terahertz light and emits the light toward the multi-junction semiconductor M disposed below.

At this time, the light source 10 is for generating terahertz light, that is, terahertz wave, means a electromagnetic wave that is located in the 0.1 ~ 10 THz region with a terahertz blue frequency and occupies a range of 3mm to 30μm as a wavelength.

In addition, terahertz waves are located in the middle region of lightwave and radiowave in the spectral distribution, so they have both linearity, absorbency and transmission of light waves. Therefore, various kinds of materials such as air, plastic, paper, fiber, ceramic, etc. It has excellent permeability to the field, has a resolution of several hundred μm, and obtains spectral information about the various kinds of materials, and enables real-time monitoring of the various kinds of materials using imaging technology. Have

In addition, the light source 10 may use a laser as an excitation light source or an incoherent light source using a coherent light source using a current injection or a blackbody radiation or a mercury lamp. ) May be a light source.

The parallel light irradiator 20 is disposed between the light source 10 and the multi-junction semiconductor M to irradiate terahertz light emitted from the light source 10 uniformly to the multi-junction semiconductor M side.

In this case, the reason for irradiating the terahertz light uniformly to the multi-junction semiconductor M side in the parallel light irradiation unit 20 is to allow the terahertz light to be irradiated to the multi-junction semiconductor M as a whole. 20 may be a cylindrical lens, an oval lens, a reflective optical system, an antenna, or the like capable of irradiating terahertz light emitted from the light source 10 uniformly to the multi-junction semiconductor M side in the form of plane light.

The light focusing unit 30 is disposed below the multi-junction semiconductor M to focus terahertz light transmitted through the multi-junction semiconductor M, and the light focusing unit 30 is a terrazzo that transmits the multi-junction semiconductor M. It may be a concave lens, a reflection mirror, an antenna, or the like capable of focusing Hertz light.

The first light detector 40 detects the terahertz light focused by the light focusing unit 30.

In this case, the first photodetector 40 converts the detected terahertz optical signal into an electrical signal having a waveform over time, and the terahertz optical signal detected by the first photodetector 40 is a multi-junction semiconductor (M). It may be a signal in which attenuation or time delay is caused by at least one or more voids included in the.

In addition, the first photodetector 40 may be configured as one, and the plurality of first photodetectors 40 may be arranged in a one-dimensional (1D) form or in a two-dimensional (2D) form to improve detection speed for terahertz light. It is possible to let.

The light distribution unit 50 is disposed between the light source 10 and the parallel light irradiation unit 20 to reflect the terahertz light passing through the parallel light irradiation unit 20 after being reflected from the multi-junction semiconductor M.

The second photodetector 60 detects terahertz light distributed by the light distribution unit 5.

In this case, the second photodetector 60 converts the detected terahertz optical signal into an electrical signal having a waveform over time, and the terahertz optical signal detected by the second photodetector 60 is a multi-junction semiconductor (M). It may be a signal in which a size change or a time delay occurs according to a difference in refractive indexes caused by at least one or more interfaces including voids among the plurality of interfaces included in the interface.

In addition, the second photodetector 60 may be configured as one, and the plurality of second photodetectors 60 may be arranged in a one-dimensional (1D) form or in a two-dimensional (2D) form to increase detection speed for terahertz light. It is possible to let.

The image signal generator 70 collects the terahertz optical signals detected by the first photodetector 40 or the second photodetector 60 to generate an image signal for the multi-junction semiconductor M.

In this case, the image signal generator 70 collects a signal which is detected by the first photodetector 40 or the second photodetector 60 and then converted into an electrical signal having a waveform over time, and then converted into a frequency domain. An image signal for the multi-junction semiconductor M may be generated using the magnitude and phase of the signal converted into the frequency domain.

The image signal analyzer 80 is an image of the multi-junction semiconductor M generated by the terahertz optical signal and the image signal generator 70 detected by the first photodetector 40 or the second photodetector 60. The signal is analyzed to determine the presence or absence of pores in the multi-junction semiconductor M and the positions of the pores.

In this case, the image signal analyzer 80 may use the attenuation or time delay of the terahertz optical signal detected by the first photodetector 40 or the magnitude change of the terahertz optical signal detected by the second photodetector 60. Alternatively, the presence or absence of voids in the multi-junction semiconductor M may be determined using the time delay.

Therefore, the pore inspection apparatus 1 of the multi-junction semiconductor according to the preferred embodiment of the present invention can determine the presence or absence of a pore with respect to the multi-junction semiconductor S and the position of the pore in the transmission method or the reflection method.

In addition, the detailed process of determining the presence or absence of the gap of the multi-junction semiconductor M and the position of the gap in the image signal analyzer 80 will be described in detail with reference to FIGS. 3 to 6.

In addition, the image signal analyzer 80 transmits the image signal for the multi-junction semiconductor M to the display D so that a user who uses the air gap inspection apparatus 1 of the multi-junction semiconductor M The presence or absence of the voids and the position of the pores can be directly confirmed, or the result of the determination of the presence or absence of the pores of the multi-junction semiconductor M and the position of the pores is transmitted to a separate processing system (S) so that the processing system (S) is the void. The multi-junction semiconductor M determined to be present may be separated or screened, or the manufacturing process of the multi-junction semiconductor S may be optimized.

3 is a reference diagram of the terahertz optical signal detected by the first photodetector of FIG. 2, FIG. 4 is a reference diagram of the terahertz optical signal detected by the second photodetector of FIG. 2, and FIG. 5 is FIG. A reference diagram of an image signal for a multi-junction semiconductor generated by the image signal generator of FIG.

First, as shown in FIG. 3A, in the case of the terahertz optical signal passing through the multi-junction semiconductor M, the plurality of media A1, A2, and A3 constituting the multi-junction semiconductor M are included. At least one void A 2 ′ causes attenuation or time delay to occur.

Therefore, as shown in FIG. 3B, when the terahertz light signal detected by the first photodetector 40 is converted into an electrical signal having a waveform over time, there are voids in the multi-junction semiconductor M. As shown in FIG. It can be seen that the attenuation or time delay Δt1 occurs when the electrical signal in the case (W / void) is compared with the electrical signal in the case where there is no void (W / O void) in the multi-junction semiconductor M.

Accordingly, the image signal analyzer 80 may determine whether the multi-junction semiconductor M is present using the terahertz optical signal detected by the first photodetector 40.

Next, as shown in FIG. 4A, in the case of the terahertz optical signal reflected from the multi-junction semiconductor M, a plurality of boundary surfaces L1, L2, L3, and L4 included in the multi-junction semiconductor M are next. A change in size or a time delay occurs according to a difference in refractive indexes caused by at least one of the boundary surfaces L2 and L3 including the voids.

Therefore, as shown in FIG. 4B, when the terahertz optical signal detected by the second photodetector 50 is converted into an electrical signal having a waveform over time, there are voids in the multi-junction semiconductor M. As shown in FIG. It can be seen that the electrical signal in the case (W / void) is caused to change in magnitude or time delay (Δt) when compared to the electrical signal in the case where there is no void in the multi-junction semiconductor (W / O void).

Therefore, the image signal analyzer 80 may determine whether the multi-junction semiconductor M is present using the terahertz optical signal detected by the second photodetector 40.

In addition, as illustrated in FIG. 5, the image signal generator 70 may generate an electrical signal having a waveform according to time generated for each of the plurality of regions P1, P2, P3, and P4 of the multi-junction semiconductor M in a frequency domain. After converting the signal to the signal of the multi-junction semiconductor (M) can be generated using the magnitude or phase of the signal converted to the frequency domain, the image signal analyzer 80 is a multi-junction semiconductor (M) By analyzing the image signal with respect to (e.g., analyzing the contrast ratio of the image signal), it becomes possible to determine the pore position inside the multi-junction semiconductor (M).

FIG. 6 is a reference graph of a terahertz optical signal collected in the image signal generator of FIG. 2, FIG. 7 is a comparison diagram of a multi-junction semiconductor image according to a conventional method, and a multi-junction semiconductor image according to the present invention, and FIG. 8 is FIG. 2 is a comparison diagram of images of multiple junction semiconductors generated by the image signal generator of FIG. 2.

As shown in FIG. 6, when the terahertz light signal detected by the first light detector 40 or the second light detector 40 is converted into an electrical signal, a signal having a waveform over time is generated. As shown in FIG. 7, the image of the multi-junction semiconductor (FIG. 7 (a)) generated by using ultrasonic waves as shown in FIG. 1 (a) and the multi-junction semiconductor according to the preferred embodiment of the present invention. Comparing the image (FIG. 7B) of the multi-junction semiconductor generated using the pore inspection device 1, it is generated using the pore inspection device 1 of the multi-junction semiconductor according to the preferred embodiment of the present invention. In the case of the image of the multi-junction semiconductor, it becomes possible to more clearly identify the structure of the multi-junction semiconductor.

In addition, as illustrated in FIG. 8, the image signal generator 70 generates an image signal for the multi-junction semiconductor M by using the magnitude of the signal converted into the frequency domain (FIG. 8A). Alternatively, the image signal for the multi-junction semiconductor M may be generated using the phase of the signal converted into the frequency domain ((b) of FIG. 8), and the image signal analyzer 80 may generate the multi-junction. By analyzing the image signal with respect to the semiconductor (M) it is possible to determine the location of the voids generated in the multi-junction semiconductor (M).

9 to 11 are reference diagrams for a pore inspection apparatus of a junction semiconductor according to still another exemplary embodiment of the present invention.

First, as shown in FIG. 9, the filter unit 90 having at least one pinhole 92 formed on the surface of the parallel light irradiator 20 and the multi-junction semiconductor M is disposed to provide a detailed inspection of a narrow region. 10, the plurality of light concentrators 30 may be arranged on the multi-junction semiconductor M in an array form A to form a multi-junction semiconductor M having a large area. It is possible to improve the void inspection speed of FIG. 9 (FIG. 9A) or to simultaneously perform the void inspection for a plurality of multiple junction semiconductors M (FIG. 9B).

In addition, as shown in FIG. 11, it is possible to determine the presence or absence of voids in a process flow in real time by applying the pore inspection apparatus of the multi-junction semiconductor of the present invention in the step of manufacturing the multi-junction semiconductor M, in particular. In the case of terahertz wave, the permeability to plastic is excellent, and thus the inspection of the presence or absence of voids in the molding m having the plastic material of the multi-junction semiconductor M is also possible.

12 is a flowchart illustrating a method for inspecting voids in a multi-junction semiconductor according to a preferred embodiment of the present invention.

As shown in FIG. 11, in S10, the light source 10 generates terahertz light and irradiates toward the multi-junction semiconductor M disposed below.

In this case, after S10, the parallel light radiator 20 disposed between the light source 10 and the multi-junction semiconductor M may further include uniformly radiating the terahertz light to the multi-junction semiconductor M side. .

In S20, the light focusing unit 30 focuses the terahertz light passing through the multi-junction semiconductor M.

In S30, the first light detector 40 detects the terahertz light focused in S20.

In this case, after S30, the image signal generator 80 may further include generating an image signal for the multi-junction semiconductor M using the terahertz light detected in S30.

In S40, the image signal analyzer 80 uses the terahertz optical signal detected in S30 and the image signal for the multi-junction semiconductor M generated by the image signal generator 80 to form a gap in the multi-junction semiconductor M. Knowing the presence and location of air gaps, the end is complete.

At this time, the image signal analyzer 80 uses the terahertz optical signal detected in S30 and the image signal for the multi-junction semiconductor M generated by the image signal generator 80 to form a gap in the multi-junction semiconductor M. Detailed processes for determining the presence and absence of air gaps have been described with reference to FIGS. 3 and 5, and thus will be omitted.

12 is a flowchart illustrating a method for inspecting voids of a multi-junction semiconductor according to another exemplary embodiment of the present invention.

As shown in FIG. 12, in S110, the light source 10 generates terahertz light and irradiates toward the multi-junction semiconductor M disposed below.

In this case, after S110, the parallel light radiator 20 disposed between the light source 10 and the multi-junction semiconductor M may further include uniformly radiating the terahertz light to the multi-junction semiconductor M side. .

In S120, after the light distribution unit 50 is reflected from the multi-junction semiconductor M, the terahertz light passing through the parallel light irradiation unit 20 is distributed.

In S130, the second light detector 60 detects the terahertz light distributed in S120.

At this time, subsequent to S130, the image signal generator 80 may further include generating an image signal for the multi-junction semiconductor M using the terahertz light detected in S130.

In S140, the image signal analyzer 80 uses the terahertz optical signal detected in S130 and the image signal for the multi-junction semiconductor M generated by the image signal generator 80 to form a gap in the multi-junction semiconductor M. If the presence and location of the gap is known, the termination is made.

At this time, the image signal analyzer 80 uses the terahertz optical signal detected in S130 and the image signal for the multi-junction semiconductor M generated by the image signal generator 80 to form a gap in the multi-junction semiconductor M. The detailed process of determining the presence and absence of air gaps has been described with reference to FIGS. 4 and 5, and thus will be omitted.

In the pore inspection apparatus and method of the multi-junction semiconductor of the present invention, the terahertz light signal transmitted through the multi-junction semiconductor M after generating terahertz light from the light source 10 and irradiating it to the side of the multi-junction semiconductor M disposed below. Alternatively, when the terahertz optical signal reflected from the multi-junction semiconductor M is detected by the first photodetector 40 or the second photodetector 60 and converted into an electrical signal having a waveform over time, the image signal generator The 70 generates an image signal for the multi-junction semiconductor M using this.

In addition, the image signal analyzer 80 may determine whether or not voids exist in the multi-junction semiconductor M by using an electrical signal having a waveform according to the converted time and an image signal for the generated multi-junction semiconductor M. I can figure out the location.

Therefore, since the multi-junction semiconductor M can be inspected by using both transmission and reflection properties, it is easy to grasp the presence or absence of the gap and the pore position of the multi-junction semiconductor M.

In addition, since the inspection of the multi-junction semiconductor is performed using terahertz waves, underwater inspection is not necessary, so that all inspection of the multi-junction semiconductor is possible in real time, and permeation of air is possible, so inspection after the air gap is also possible. Has an effect.

The above is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains various modifications, changes, and substitutions without departing from the essential characteristics of the present invention. will be. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical spirit of the present invention, but to explain, and the technical spirit of the present invention is not limited by the embodiments and the accompanying drawings. . The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the same scope should be interpreted as being included in the scope of the present invention.

(1): gap inspection apparatus of a multi-junction semiconductor (10): light source
20: parallel light irradiation part 30: light focusing part
40: first photodetector 50: light distributor
60: second photodetector 70: video signal generator
80: video signal analysis unit 90: filter unit
(92): pinhole

Claims (12)

In the void inspection apparatus of a multi-junction semiconductor,
A light source for generating terahertz light and irradiating the multi-junction semiconductor side disposed below;
A parallel light irradiation unit disposed between the light source and the multi-junction semiconductor to uniformly irradiate terahertz light emitted from the light source to the multi-junction semiconductor side;
An optical focusing unit disposed under the multi-junction semiconductor to focus terahertz light passing through the multi-junction semiconductor; And
And a first photodetector configured to detect the terahertz light focused at the optical focusing unit. The method of claim 1,
And a light distribution unit disposed between the light source and the parallel light irradiation unit to distribute terahertz light passing through the parallel light irradiation unit after being reflected from the multi-junction semiconductor. The method of claim 2,
And a second photodetector for detecting the terahertz light distributed by the light distribution unit. The method of claim 1,
And a filter unit disposed between the parallel light irradiating unit and the multi-junction semiconductor and having at least one pinhole formed on a surface thereof. The method of claim 1,
And a plurality of the parallel light irradiating portion or the light focusing portion arranged in an array form. The method of claim 3,
An image signal generator configured to collect terahertz optical signals detected by the first or second photodetector to generate an image signal for the multi-junction semiconductor, and the collected terahertz optical signal and the generated image And a video signal analyzer configured to analyze a signal to determine whether there is a gap in the semiconductor and a position of the gap. The method according to claim 6,
The terahertz optical signal detected by the first photodetector is a signal having attenuation or time delay caused by at least one or more voids included in the multi-junction semiconductor,
And the image signal analyzer detects the presence or absence of the voids and the positions of the pores using the attenuation or the time delay. The method according to claim 6,
The terahertz optical signal detected by the second photodetector is a signal in which a size change or a time delay occurs according to a difference in refractive index caused by at least one interface including voids among a plurality of interfaces included in the multi-junction semiconductor,
And the image signal analyzer detects the presence or absence of voids in the multi-junction semiconductor and the location of the pores using the size change or the time delay. In the void inspection method of a multi-junction semiconductor,
(a) generating terahertz light and irradiating the multi-junction semiconductor side;
(b) concentrating terahertz light passing through the multi-junction semiconductor;
(c) detecting the focused terahertz light; And
and (d) determining the presence or absence of the pore of the multi-junction semiconductor and the position of the pore by using the detected terahertz optical signal. The method of claim 9,
In the step (d)
The detected terahertz optical signal is a signal in which attenuation or time delay occurs due to at least one or more voids included in the multi-junction semiconductor,
The step (d)
And determining whether the multi-junction semiconductor is void by using the attenuation or the time delay. In the void inspection method of a multi-junction semiconductor,
(a) generating terahertz light and irradiating the multi-junction semiconductor side;
(b) distributing terahertz light reflected from the multi-junction semiconductor;
(c) detecting the distributed terahertz light; And
and (d) determining the presence or absence of the pore of the multi-junction semiconductor and the position of the pore by using the detected terahertz light. 12. The method of claim 11,
In the step (d)
The detected terahertz optical signal is a signal in which a magnitude change or a time delay occurs according to a difference in refractive index caused by at least one or more interfaces including voids among a plurality of interfaces included in the multi-junction semiconductor,
The step (d)
And determining the presence or absence of the pore of the multi-junction semiconductor and the position of the pore by using the change in size or the time delay.

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