KR101998138B1 - Analyzing Method of Polytypes of Crystals Using Ultraviolet Photoluminescence - Google Patents

Abstract

The present invention relates to a method for analyzing a polytype of crystals using ultraviolet photoluminescence, the method comprising: an ultraviolet ray irradiation step in which ultraviolet light emitted from a light source is irradiated onto a surface side of a sample; A photoluminescence image information acquiring step of acquiring photoluminescence image information by receiving a photoluminescence emitted from a surface side of the sample irradiated with the ultraviolet light in the ultraviolet light irradiation step; The photoluminescence image information obtained in the camera device is transferred from the camera device side to the data processing device side in the photoluminescence image acquiring step and the polytype of the sample can be determined. A data processing step of converting the photoluminescence image information into at least one or more color points that can be displayed on a predetermined color space; A polycrystalline type crystal such as silicon carbide can be grasped quickly and precisely. Thus, a technique capable of suppressing deterioration in quality in manufacturing an LED or a laser diode and further increasing production yield is disclosed.

Description

[0001] The present invention relates to a method of analyzing crystals using ultraviolet photoluminescence,

The present invention relates to a method of polytype analysis of crystals such as silicon carbide.

Silicon carbide (SiC) with a closed packed crystal structure is a material with a wide bandgap and is a promising material that can be applied to laser diodes, LEDs, or power electronic devices.

Thus, the polytypes generated during silicon carbide growth have been a common issue.

During crystal growth, various types can be generated in the bulk of a single sample depending on the stacking order of the silicon carbide due to temperature variations in the sample. And, these other types of stacking sequences are called polytypes.

The polytypes have distinct dense planes, but the order of accumulation in the three axes perpendicular to these planes is different. At least 170 poly types of silicon carbide are known, but most of them are rare except for 2H, 4H, 6H, 15R and 3C types.

These polytypes of silicon carbide have equal density and Gibbs free energy, but the electronic band structures are different. The difference in band structure causes emission of luminescence at different wavelengths when ultraviolet light is incident on silicon carbide.

Silicon carbide can be grown through several crystal growth techniques such as physical vapor deposition (PVD), high temperature chemical vapor deposition (HT-CVD), or top seeded solution growth (TSSG)

Production of two or more polytypes in the production process is one of the drawbacks of bulk silicon carbide.

For example, in the fabrication of an LED template using 4H-silicon carbide, a polytype such as 6H-silicon carbide or 15R-silicon carbide is present in a silicon carbide wafer, and using such a silicon carbide wafer, an LED or a laser diode The lattice constant of 6H-SiC or 15R-SiC is very different from the lattice constant of gallium nitride (GaN), so that the quality of the LED or the laser diode is inevitably lowered.

Therefore, there is a need for a rapid test method capable of distinguishing polytypes in producing silicon carbide crystals.

Korean Patent No. 10-1607907

The object of the present invention is to solve the conventional problems as described above, and it is an object of the present invention to provide a polytype analysis method of crystals capable of judging whether crystals are properly manufactured by judging quickly and accurately whether a polytype of a produced crystal is a polytype .

According to another aspect of the present invention, there is provided a method for analyzing a polytype of crystals using ultraviolet photoluminescence, comprising the steps of: irradiating ultraviolet light emitted from a light source onto a surface side of a sample; A photoluminescence image information acquiring step of acquiring photoluminescence image information by receiving a photoluminescence emitted from a surface side of the sample irradiated with the ultraviolet light in the ultraviolet light irradiation step; The photoluminescence image information obtained in the camera device is transferred from the camera device side to the data processing device side in the photoluminescence image acquiring step and the polytype of the sample can be determined. A data processing step of converting the photoluminescence image information into at least one or more color points that can be displayed on a predetermined color space; May be included as one feature.

Here, the sample may also be characterized by being silicon carbide (SiC).

Here, the step prior to the ultraviolet ray irradiation step may include: a preparation step of cleaning the sample; May be further included.

Here, in the photoluminescence image information acquisition step, the photoluminescence image information may be stored in the camera device as information of RGB (Red, Green, Blue) format have.

A display step in which the display device displays the color space and the color point so that the color point converted and processed in the data processing step can be recognized from outside; May be further included.

Further comprising a determining step of determining the polytype of the sample by comparing the information on the polytypes of the determinations stored in the database with the data processing apparatus after the data processing step, In the display step, the determination result information on the polytype of the sample determined in the determination step may be transmitted to the display device by the data processing device and displayed by the display device.

Here, the color space in the data processing step may be a color space defined according to the CIE 1931 standard colorimetry system.

Here, a beam expender for diffusing the ultraviolet light is located between the light source and the sample, and the ultraviolet light is irradiated to the surface side of the sample through the beam expander in the ultraviolet light irradiation step. .

Here, the ultraviolet ray emitted from the light source side may be filtered by a first optical bandpass filter and irradiated to the sample side in the ultraviolet ray irradiation step.

Furthermore, the wavelength of the ultraviolet light that is filtered by the first optical band-pass filter and is incident on the sample side may be a characteristic of between 300 nm and 400 nm.

In the photoluminescence image information obtaining step, the photoluminescence emitted from the sample side is filtered by the second optical band-pass filter before being incident on the camera apparatus It is possible.

Further, in the photoluminescence image information acquiring step, the wavelength of the photoluminescence that is filtered by the second optical bandpass filter and is incident on the camera apparatus side may be another feature that is larger than 450 nm .

The method for analyzing the polytype of crystals using ultraviolet photoluminescence according to the present invention can quickly and accurately grasp the polytype of a crystal such as silicon carbide and thus can prevent deterioration of quality in manufacturing an LED or a laser diode, There is an effect that the yield can be increased.

FIG. 1 schematically shows a comparison between a polytype analysis of crystals using ultraviolet photoluminescence and an analysis using a photoluminescence spectrometer.
FIG. 2 is a schematic view of a system for analyzing a polytype of crystals using ultraviolet photoluminescence capable of conducting a method for analyzing a polytype of crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
3 is a flowchart schematically illustrating a method of analyzing a polytype of crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
4 is a view schematically showing a transmittance distribution according to wavelength of a first optical bandpass filter in a method of analyzing a polytype of crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
5 is a diagram schematically showing a transmittance distribution according to a wavelength of a second optical bandpass filter in a method of analyzing crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
6 is a diagram schematically illustrating a color space according to a CIE 1931 format in a method of analyzing crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
FIG. 7 is a diagram schematically illustrating poly type boundaries and band gap boundaries in a color space in a method of analyzing crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
8 is a diagram schematically illustrating conversion of monochromatic light into color points in a color space in a method of analyzing crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
FIG. 9 is a graph schematically showing a temperature-dependent Gaussian distribution in a method of analyzing crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
FIG. 10 is a graph illustrating a method of analyzing crystals using ultraviolet photoluminescence according to an embodiment of the present invention. In order to determine polytype lines in a color space, a tristimuli normalized spectral distribution, a Gaussian distribution of photoluminescence And xyz color space.
FIG. 11 schematically shows the boundaries between the respective polytypes in the method of analyzing crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
FIG. 12 is a schematic diagram of a polytype line and boundaries in a color space in a method of analyzing crystals using ultraviolet photoluminescence according to an embodiment of the present invention.
13 schematically shows an example of an ultraviolet photoluminescence image.
14 schematically shows a photoluminescence peak in which 4H-SiC and 6H-SiC are mixed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

According to the method for analyzing the polytype of crystals using the ultraviolet photoluminescence of the present invention, it is possible to determine the bulk state or the polytype of crystals in the wafer state using an ultraviolet photoluminescence image.

As a preferred embodiment of the present invention, a polytype determination method for silicon carbide crystal will be described. For convenience of explanation, the bulk or wafer state is simply referred to as a sample.

A brief description of the theoretical principles related to the present invention follows.

When the photon's energy is greater than the bandgap energy of silicon carbide when ultraviolet photons are incident on the silicon carbide crystal surface, the photon excites the electrons of the balanced band to the conduction band. The excited electrons can emit heat to move to a lower energy state or relax in a balance band while emitting photons of longer wavelengths than incident light.

A phenomenon in which a wavelength shifts to a long wavelength due to the interaction between a silicon carbide material and a photon is called photoluminescence.

Since the silicon carbide polytypes have different band gaps, the polytypes can be identified by the photoluminescence color.

For example, the band gap of 4H-SiC is 2.44 eV and the luminescence color is green. The band gap of 6H-SiC is 2.12 eV, the luminescence color is yellow, the band gap of 15R-SiC is 1.6 eV, and the luminescent color is orange.

Due to these properties, it can be determined by analyzing the polytype of the silicon carbide sample using ultraviolet photoluminescence.

Symbols which can be referred to in explaining the embodiments of the present invention are briefly shown in Table 1 below.

Symbol Designation Unit λ Wavelength nm T Temperature K ρ Resistivity Ω.cm E Bandgap energy eV I Intensity of the light source W / cm ² h Plank's constant 6.626070040 (81) x 10 ^-34 J · s c Velocity of light 299,792,458m / s

The following is a brief description of the difference between the ultraviolet photoluminescence (PL) imaging test, that is, the polytype analysis of crystals using ultraviolet photoluminescence and the photoluminescence spectrometer.

In the case of a photoluminescence spectrometer, the polytype crystal of silicon carbide is performed using a microscope such as a diffraction system such as a photoluminescence spectrometer, a Raman spectrometer or a high resolution XRD (HR-XRD) or a transmission electron microscope (TEM) .

In addition to the additional material properties that can be measured, this method can be used precisely to measure the polytype but can only be used for pint detection, and it is difficult to utilize because it takes a lot of time and cost to prepare the sample.

FIG. 1 schematically shows a polytype analysis of crystals using ultraviolet photoluminescence and an analysis using a PL spectrometer. Both methods are identical in that the photoluminescence beam is emitted from the sample, but the detailed method of analyzing it is completely different.

Fig. 1 (a) schematically shows the spectrum of light.

When a photoluminescence light that emits a wave of a certain waveform is emitted from a silicon carbide sample, as shown in Fig. 1 (b), a monochromator capable of dividing the photoluminescence light into monochromatic light, Is used as a photoluminescence spectrometer, and the wavelength is determined by measuring the intensity of light with a photodetector as shown in Fig. 1 (c).

On the other hand, the analysis of the polytype of crystals using ultraviolet photoluminescence is very different from the method of PL spectrometer.

As shown in Fig. 1 (d), there is a retina in the human eye, which can be referred to as a sensor for detecting brightness. The retina consists of three cones that detect red, green, and blue (RGB: red, green, blue), respectively.

The normalized spectral sensitivity of the RGB color of human cone cells is as shown in Fig. 1 (e). This is a weight function of the cone sensitivity along the wavelength.

When light enters the cone cell, the cone cell senses the total intensity. This intensity is weighted with normalized spectral sensitivity.

The following relationships (A.1.1 to A.1.3) are the total intensity of RGB colors recognized by the retina. Here, X, Y, and Z mean RGB colors. The total intensity can be expressed as an integral of the intensity distribution of the light times the normalized spectral density for a wavelength of 450 nm to 850 nm.

(A.1.1)

(A.1.1)

(A.1.2)

(A.1.2)

(A.1.3)

(A.1.3)

Thereafter, the total intensity of XYZ is normalized again according to the relational expressions (A.1.4 to A.1.6), and the color point (x, y, z) is drawn in the color space .

(A.1.4)

(A.1.4)

(A.1.5)

(A.1.5)

(A.1.6)

(A.1.6)

Next, with reference to FIG. 2, a description will be given of a polytype analysis system for crystals using ultraviolet photoluminescence capable of performing a method of analyzing a polytype of crystals using ultraviolet photoluminescence according to an embodiment of the present invention .

The silicon carbide crystal 10 can be grown according to various techniques. The method for analyzing the polytype of crystals using ultraviolet photoluminescence according to the present invention can be applied to any sample regardless of various growth techniques. In addition, the sample can be applied regardless of wafer state or ingot state.

The surface of the silicon carbide sample 10 is polished flat so that the ultraviolet rays are not scattered on the surface of the sample 10 and the photoluminescence light can be directly incident on the camera device 200 such as a digital camera It is also desirable to improve the accuracy of the measurement.

The stage (not shown) in which the silicon carbide sample 10 is placed supports the silicon carbide sample to be stably placed. The use of a stage in a non-vibration state or an anti-vibration state is preferable because the occurrence of noise due to vibration can be prevented.

The light source 100 is preferably capable of emitting visible light as well as ultraviolet light.

The wavelength of the ultraviolet light emitted from the light source 100 preferably falls within a non-visible range or a monochromatic range corresponding to a range of 150 nm to 400 nm.

The intensity of the ultraviolet rays emitted from the light source 100 is preferably 600 mW / cm ² or more.

The distance between the silicon carbide sample 10 and the light source 100 may be about 10 to 30 centimeters, and it is also possible to set the distance as required.

A lens (not shown) of the light source 100 may be used to focus the incident ultraviolet beam onto the silicon carbide sample 10. The position and the focal distance of the lens are preferably selected or set in advance so that the ultraviolet beam can be incident on the silicon carbide sample 10 with uniform intensity.

The angle (0 to 360 degrees) between the light source 100 and the silicon carbide sample 10 in the reflectance mode prevents the light emitted from the ultraviolet light source 100 from being directly incident on the camera device 200 side It is preferable that the arrangement is such that only the photoluminescence beam emitted from the silicon carbide sample 10 can be measured by the camera device 200.

In the transmission mode, the beam emitted from the silicon carbide sample 10 side can be measured using the camera device 200.

It is also preferable to diffuse the ultraviolet light using a beam expander 110 so that the ultraviolet beam emitted from the light source 100 can be sufficiently illuminated over the entire surface area of the silicon carbide sample 10.

The beam expander 110 may be disposed in front of the light source 100 so as to be positioned on the optical path between the light source 100 and the silicon carbide sample 10. [

If light other than photoluminescence is incident on the camera device 200 side, the measurement may be interrupted. Therefore, it is preferable to use a first optical bandpass filer 120 capable of passing only ultraviolet rays.

The first optical band-pass filter 120 may be positioned in front of the light source 100 or in front of the beam expander 110 in order to filter light of wavelengths other than the ultraviolet range. It is preferable that the transmittance distribution according to the wavelength of the first optical band-pass filter 120 can pass only the objective ultraviolet light as shown in FIG.

The second optical bandpass filter 130 filters the beam reflected from the silicon carbide sample 10 and transmits the photoluminescence beam emitted from the silicon carbide sample 10 to the camera device 200 and the silicon carbide It is preferable to be disposed between the samples 10.

A digital camera may be used as the camera device 200 for receiving image information from the photoluminescence emitted from the silicon carbide sample 10. As such a digital camera, a CCD camera may be more preferably used.

And, it is preferable to set the preferable camera condition so that photoluminescence emitted from the silicon carbide sample 10 can be photographed.

As an example of specific camera conditions, ISO exposure is 500 ± 100, f (f / #) is f / 1.8 to f / 3.2, exposure compensation is zero, shutter speed is 1 / 30-50, The white balance can be set to 6500K. This may be referred to as a standard condition for ultraviolet photoluminescence, and may be changed as necessary.

From the photoluminescence emitted from the silicon carbide sample 10 side, the camera device 200 acquires image information. Here, the photoluminescence image information acquired by the camera device 200 is preferably in RGB format and is stored in the camera device.

Then, the image information acquired by the camera device 200 is transmitted to the data processing device 300 side.

The data processing apparatus 300 receives the photoluminescence image information from the camera apparatus 200. Then, the converted photoluminescence image information is converted into at least one color point so as to be displayed in a predetermined color space.

Then, the data processing apparatus 300 transmits the information on the predetermined color space and the converted color point to the display device 400 so that the color space can be recognized from the outside.

The data processing apparatus 300 preferably includes a database (not shown) in which information about various polytypes of decisions is stored.

If such a database is provided, the data processing apparatus 300 determines which coordinates in the color space correspond to the converted color points, and compares the converted color points with information about the various polytypes stored in the database, It is possible to determine which polytype corresponds to which polytype, and to obtain the judgment result information.

The determination result information obtained by the data processing apparatus 300 may be transmitted to the display apparatus 400 and the display apparatus 400 may display the determination result information from the outside.

The display device 400 displays a color space and a color point so that the color point converted and processed in the data processing apparatus 300 can be recognized from the outside.

More preferably, judgment result information determined by the data processing apparatus 300 on the polytype of the silicon carbide sample is also transmitted from the data processing apparatus 300 to the display apparatus 400 side, The result of the determination is also displayed.

FIG. 2 is a view schematically showing a system for analyzing a polytype of crystals using ultraviolet photoluminescence capable of conducting a method of analyzing a polytype of crystals using ultraviolet photoluminescence according to an embodiment of the present invention, and FIG.

3 is a flowchart schematically illustrating a method of analyzing a polytype of crystals using ultraviolet photoluminescence according to an embodiment of the present invention.

2 to 3, a method for analyzing a polytype of crystals using ultraviolet photoluminescence according to an embodiment of the present invention includes an ultraviolet ray irradiation step, a photoluminescence image information acquisition step, and a data processing step And more preferably includes a preparation step and a display step, and more preferably, the determination step may be further included.

<< S010 >>

The preparing step S010 is a step prior to the ultraviolet ray irradiation step of irradiating the silicon carbide sample 10 with ultraviolet rays and is a step of cleaning the silicon carbide sample 10. [

Cleaning is performed on the silicon carbide sample 10 so that occurrence of unnecessary noise or the like can be suppressed.

For example, the surface of a silicon carbide wafer is cleaned by wiping with a clean tissue moistened with an appropriate solvent such as acetone or ethanol to remove foreign matter such as dust and moisture. During the cleaning process, the solvent on the surface is evaporated.

<< S100 >>

The ultraviolet ray irradiation step (S100) is a step in which ultraviolet light emitted from a light source is irradiated to the surface side of the silicon carbide sample (10).

It is desirable to be done in a dark place to prevent other light which may interfere with the ultraviolet photoluminescence beam.

The stage (not shown) where the silicon carbide sample 10 is placed supports the silicon carbide sample 10 so that it can be stably placed. The use of a stage in a non-vibration state or an anti-vibration state is preferable because the occurrence of noise due to vibration can be prevented.

It is preferable that the optical axis of the CCD camera, which is the camera device 200, is arranged so as to coincide with the silicon carbide sample 10 to maximize the intensity of ultraviolet photoluminescence incident on the CCD camera.

The ultraviolet light emitted from the light source 100 is incident on the beam expander 110 to diffuse the beam, and ultraviolet light is incident on the first optical band-pass filter 120 and then filtered. And the filtered ultraviolet radiation is irradiated to the surface of the silicon carbide sample 10.

Here, the wavelength of ultraviolet light that is filtered and transmitted by the first optical band-pass filter 120 is preferably between 300 nm and 400 nm as shown in FIG.

<< S200 >>

In the photoluminescence image information acquiring step S200, the photoluminescence emitted from the surface side of the sample 10 irradiated with the ultraviolet rays in the ultraviolet ray irradiation step S100 is received by the camera device 200, And acquiring luminescence image information.

Ultraviolet ray photoluminescence is emitted from the silicon carbide sample 10 by the ultraviolet ray irradiated to the silicon carbide sample 10 in the ultraviolet ray irradiation step S100.

Here, it is preferable that the photoluminescence emitted from the silicon carbide sample 10 side is filtered by the second optical band-pass filter 130 before it is incident on the camera device 200.

The beam reflected from the silicon carbide sample 10 is blocked by the second optical bandpass filter 130 and only the photoluminescence beam emitted from the silicon carbide sample 10 is incident on the CCD camera 200 And therefore it is preferable.

As described above, it is preferable that only the ultraviolet photoluminescence filtered by the second optical band-pass filter 130 is incident on the CCD camera 200. Here, the transmittance distribution according to the wavelength of the second optical band-pass filter 130 is as shown in FIG.

As shown in FIG. 5, it is preferable that the wavelength of the filtered photoluminescence that is filtered by the second optical bandpass filter 130 and incident on the CCD camera 200 side is larger than 450 nm.

When the ultraviolet photoluminescence transmitted through the second optical bandpass filter 130 is incident on the camera device 200, the camera device acquires ultraviolet photoluminescence image information by capturing the ultraviolet photoluminescence image information.

The ultraviolet photoluminescence image information is stored in the camera device 200 such as a CCD camera as information of RGB (Red, Green, Blue) format.

<< S300 >>

In the data processing step S300, the photoluminescence image information obtained in the photoluminescence image acquiring step S200 is transmitted from the camera device 200 side to the data processing device 300 side, The data processing apparatus 300 may include at least one color point capable of displaying the photoluminescence image information on a predetermined color space so that the polytype of the silicon carbide sample 10 can be determined. .

The ultraviolet photoluminescence image information taken by the CCD camera 200 is preferably converted into a predetermined color space.

Wherein the predetermined color space is a color space defined according to the CIE 1931 standard colorimetry system.

6 is a diagram schematically showing a color space according to the CIE 1931 format. 6, an RGB image stored by the camera device is converted to at least one color point so that it can be displayed on the color space according to the CIE 1931 format.

Then, it can be displayed as a color point on the color space as shown in FIG. 6, and the polytype can be determined by the color point position on the color space and can be determined.

Explains the conversion of image information obtained by ultraviolet photoluminescence to color space.

The boundaries of the polytype can be represented as shown in the left graph of FIG. The red line represents the polytype line. The black line in the left graph of FIG. 7 is the boundary line between the polytype lines and helps to determine what the major polytypes are.

The bandgap boundaries are shown in the right graph of FIG. The wavelength displayed at the edge of the color space means its bandgap. Therefore, if the band gap of the sample is not known, the bandgap can be predicted using this graph.

The ultraviolet photoluminescence image information is preferably converted to a CIE 1931 color space with a polytype boundary for poly type identification of silicon carbide.

Each poly type has a different band gap energy, indicating that each poly type has a different color.

Thus, when an ultraviolet photoluminescence image is converted to a CIE 1931 color space, each poly type has a different position in the color space.

The coordinates of each polytype in the color space in 0 kelvin are described below.

Each poly type has a unique bandgap, so it emits a monochromatic photoluminescence beam at 0 Kelvin when irradiated with ultraviolet light. The band gap energy of the polytype is different from that of the polytype so that it can be a reference for the polytype determination.

Table 2 shows the band gap energy calculated by the relation between the wavelength of the polytype measured by the photoluminescence spectrometer and Planck's relation (A.1.7).

Polytype Bandgap (eV) Wavelength (nm) 4H-SiC 2.2959 540 6H-SiC 2.0325 610 15R-SiC 1.604 770 3C-SiC 1.59 780

(A.1.7)

(A.1.7)

Such a band gap or wavelength can be converted into one color point in the color space as mentioned above.

Figure 8 schematically shows the conversion of monochromatic light into color points in the color space.

8 (a) is a spectral density distribution normalized according to the tri-stimuli defined in CIE 1931, and FIG. 8 (b) shows the monochromatic distribution of each polytype shown at the last lowest point of Table 2 light intensity distribution, and has the shape of a delta function.

XYZ can be calculated by multiplying the two distributions of Figs. 8 (a) and (b) and integrating the wavelength as in the following equations (A.1.1 to A.1.3). The intensity of XYZ is schematically shown in Fig. 8 (c).

(A.1.1)

(A.1.1)

(A.1.2)

(A.1.2)

(A.1.3)

(A.1.3)

Then, the normalized xyz is calculated as the following equations (A.1.4 to A.1.6), and can be shown as in Fig.

(A.1.4)

(A.1.4)

(A.1.5)

(A.1.5)

(A.1.6)

(A.1.6)

As shown in FIG. 6, 4H-SiC, 6H-SiC, 15R-SiC and 3C-SiC are indicated by black dots at the edge of the color space.

The monochromatic light is always arranged at the edge of the color space. In the case of white RGB, since the coordinates are (1/3, 1/3, 1/3), the center black dot indicates a white point. Since the monochromatic wavelengths of 15R-SiC and 3C-SiC are too close to 770nm and 780nm, the converted points are superimposed as shown in Fig.

In this manner, the data processing step S300 converts the photoluminescence image information into at least one color point that can be represented in the color space.

Then, the display device 400 displays the color space and the color point so that the color point converted in the data processing step S300 can be recognized from the outside.

Accordingly, it is also preferable to proceed to the display step S400 after the data processing step S300, but it is also preferable that the display step S400 is performed after the determination step S310.

<< S310 >>

The determination step S310 is a step after the data processing step S300 in which the data processing apparatus 300 compares the information about the polytypes of the determinations stored in the database to the poly And determining the type.

At very low temperatures, the photoluminescence beam is monochromatic because it has a delta function form. However, when the temperature rises, the photoluminescence beam has a Gaussian distribution.

This property of the photoluminescence beam can be modeled by the Gaussian function shown in Eq. (B.2.1), and when β changes, the shape parameters change.

When β is 0 in equation (B.2.1), it becomes a delta function as in equation (B.2.2), and maximum and half width maximum (FWHM) are given by equations (B.2.3) and .

(B.2.1)

(B.2.1)

(B.2.2)

(B.2.2)

(B.2.3)

(B.2.3)

(B.2.4)

(B.2.4)

In equation (B.2.1), β varies with the material but increases with increasing temperature.

Using these properties, polytype lines can be calculated.

In 0 kelvin, the coordinates of each polytype in the color space are first calculated and plotted. All of these color dots are drawn at the edge of the color space.

As the temperature increases, β increases and the maximum height of the photoluminescence distribution decreases as shown in (B.2.3) and increases as in (B.2.4).

As can be seen from Fig. 9, the distribution becomes uniform as beta goes to infinity.

The polytype line can be calculated using the Gaussian distribution at various temperatures in equation (B.2.1).

Fig. 10 shows a procedure substantially the same as Fig. 8 except for Fig. 10 (b), and is extended to various shape parameters [beta] as shown in Fig. Figure 10 (c) shows the results.

Although Figure 6 depicts all single points at the corners of the color space by way of illustration, all points are drawn as lines when the temperature changes, as shown in Figure 10 (c).

These lines are uniformly distributed when the temperature is infinite, and as the intensity of the RGB color becomes the same, the final luminance (1/3, 1/3, 1/3), that is, converging to the white point. Therefore, all the lines converge to white as shown in Fig. 10 (c).

For reference, the polytype line in Fig. 10 (c) is not a straight line because the CIE 1931 distribution in Fig. 10 (a) is not uniform or is not symmetrical.

Further, the lines of 15R-SiC and 3C-SiC are too close to distinguish. If there is only one poly type, the points converted from the ultraviolet photoluminescence image of the silicon carbide into the color space are in one of these lines.

Even if the silicon carbide single crystal is well formed, there is a poly type different from the defect. Thus, the color points converted to the color space are dispersed around the lines, rather than being arranged on one polytype line. Therefore, a boundary that defines a region of a particular polytype is needed.

Table 3 shows that the arithmetic mean of the band gap energies between adjacent polytypes is added to Table 2.

Polytype Bandgap Wavelength (eV) (λ) Upper boundary 2.4276 510 4H-SiC 2.2959 540 Boundary between 4H & 6H-SiC 2.1642 575 6H-SiC 2.0325 610 Boundary between 6H & 15R-SiC 1.81825 680 15R-SiC 1.604 770 Boundary between 15R & 3H-SiC 1.597 775 3C-SiC 1.59 780 Lower boundary 1.583 785

As can be seen from equation (B.1.1), the band gap energy (E) and the wavelength (λ) are inversely proportional, so that the arithmetic mean is not made in the bandgap energy domain and is transformed into the wavelength domain using equation (B.1.1) .

The procedure for obtaining polytype boundary lines is as described above.

Figure 11 shows the boundaries between each polytype.

For reference, the area of 3C-SiC is excluded because of insufficient color space.

Such a boundary serves as a benchmark for determining the polytype of the sample or may be a criterion for judging whether or not the target sample is successfully manufactured.

12, which also includes a border and a polytype line, can also be used to determine the polytype.

If the silicon carbide sample is a perfect single crystal, then the color point converted from the image to the color space should be in one of the polytype lines drawn in the form of a curve, as referenced in Figure 10 (c) .

However, there may be a defect in the sample or two or more polytypes in the sample. In this case, color points may be distributed around the lines of the polytype.

The polytype can be determined qualitatively. That is, if the color points of the sample are distributed only on one polytype line among the many typical polytype lines. It is judged that the polytype of the sample corresponds to one of them.

When the color points of the sample are widely distributed in the regions of the plurality of polytypes, the number of color points included in each polytype region is counted and the major polytype region is selected and determined.

When the type of the polytype or the band gap energy is ambiguous, the band gap energy can be evaluated using Fig.

<< S400 >>

In the display step S400, the display device 400 displays the color space and the color point so that the color point converted in the data processing step S300 can be recognized from the outside.

Therefore, the manager can directly determine the polytype by looking at the color space and color point expressed in the display device 400. [

It is also preferable that the determination result information on the polytype of the silicon carbide sample 10 determined in the determination step is transmitted to the display device 400 by the data processing device 300 and displayed by the display device 400 Do.

If the color point, the color space, and the determination result information regarding the silicon carbide sample 10 are all displayed in the display device 400 through the determination step S310, the user can more easily grasp the polytype of the silicon carbide sample 10 It is preferable.

As described above, it is also possible to determine the types of polytypes by using the polytype analysis method of crystals using ultraviolet photoluminescence according to the embodiment of the present invention.

13 schematically shows an example of an ultraviolet photoluminescence image.

Figure 13 shows the conversion of various types of SiC wafers into ultraviolet photoluminescence images and color spaces. 13 (a) shows the case of 4H-SiC. The converted data is distributed around the 4H-SiC line, and the other is distributed in the blue region where noises can be neglected in the ultraviolet light source.

And Fig. 13 (b) shows the case of 6H-SiC. The color dots are mainly distributed around the 6H-SiC line as shown in Fig. 13 (a), and others are distributed in the blue region. In Figs. 13 (a) and 13 (b), the polytype can be correctly identified.

However, in FIG. 13 (c) and FIG. 13 (d), since the color points are distributed in various regions, it is difficult to determine the main polytype of the silicon carbide sample, but their characteristics can be evaluated.

14 schematically shows a photoluminescence peak in which 4H-SiC and 6H-SiC are mixed.

When the polytype is mixed in the same place, the color point distribution in the color space will have different properties depending on the sample.

13 (c) and (d) are SiC wafers having mixed polytypes. Figure 13 (c) is better than Figure 13 (d) because the figure 13 (d) shows many types of colors that can be seen in visual inspection at first glance.

In Fig. 13 (c), the hue points are distributed over the 4H-SiC line, the 6H-SiC line, and the 2 lines. 13 (d), the hue points are mainly distributed in the 4H-SiC line and the 6H-SiC line.

These may be interpreted as follows.

14 (a) is a photoluminescence peak in which 4H-SiC and 6H-SiC having the same strength are mixed.

Figure 14 (b) shows the color points converted from the color space with the color points of 4H-SiC and 6H-SiC. 4H-SiC and 6H-SiC mixed color points are not the same as pure 4H-SiC or 6H-SiC lines. The pattern is placed on the middle line between the two lines. The final color is the integration of all monochromatic waves to wavelength.

In the same mechanism, if the intensity of 4H-SiC is higher than that of 6H-SiC, the mixed color point is bent toward the 4H-SiC line side as shown in Fig. 14 (c) The same is true.

Thus, the color points distributed over the 4H and 6H lines can mean that they are mixed with two types of poly types at the same location.

Also, the relative intensity, i.e., the relative density of the polytype, can be calculated according to its position.

Figure 14 (c) shows better quality than Figure 14 (d), which is seen as the naked eye. However, ultraviolet photoluminescence imaging methods show different analytical results. There are many intermediate color points in Figure 14 (c), which means that there are many mixed color points. In Fig. 14 (d), there are only two groups of 4H-SiC polytype lines and 6H-SiC polytype lines, with no intermediate distribution. This means that there are no mixed color points. Therefore, the sample of Fig. 14 (d) has better quality.

For reference, the depth of penetration of silicon carbide is described as follows.

In fact, the naked eye is detected as a mixed poly type polytype because the photoluminescence beam can penetrate the silicon carbide sample through the penetration depth. The penetration depth of the wavelength for silicon carbide is about 100 to 250 nm at 266 nm and about 50 to 100 nm at 244 nm.

Thus, all the polytypes within this depth can be measured according to the ultraviolet wavelength of the light source.

As described above, the method of analyzing the polytype of crystals using ultraviolet photoluminescence according to the embodiment of the present invention can quickly and accurately grasp the polytype of crystals such as silicon carbide. Therefore, in manufacturing LEDs or laser diodes, And the production yield can be increased.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is to be understood that the scope of the present invention is to be construed as being limited only by the embodiments, and the scope of the present invention should be understood as the following claims and their equivalents.

10: Sample
100: Light source
110: beam expender &lt; RTI ID = 0.0 &gt;
120: a first optical band pass filter;
130: second optical bandpass filter
200: camera device
300: Data processing device
400: display device

Claims (12)

An ultraviolet light irradiation step in which ultraviolet light emitted from a light source is irradiated to the surface side of the sample;
A photoluminescence image information acquiring step of acquiring photoluminescence image information by receiving a photoluminescence emitted from a surface side of the sample irradiated with the ultraviolet light in the ultraviolet light irradiation step; And
Wherein the photoluminescence image information acquired in the camera device is transferred from the camera device side to the data processing device in the photoluminescence image acquisition step and the polytype of the sample is determined, A data processing step of converting the photoluminescence image information into at least one color point capable of being displayed on a predetermined color space; , &Lt; / RTI &
The sample is silicon carbide (SiC)
A beam expander for diffusing the ultraviolet light is positioned between the light source and the sample,
In the ultraviolet ray irradiation step,
The ultraviolet rays are irradiated to the surface side of the sample through the beam expander,
In the photoluminescence image information acquiring step,
The photoluminescence image information is stored in the camera device as RGB (Red, Green, Blue) format information. The photoluminescence image information is in the form of a delta function at 0 Kelvin or a Gaussian function at a temperature greater than 0 Kelvin Respectively,
The data processing step includes:
Integrating the product of the photoluminescence image information and the standardized spectral density with the wavelength of the visible light using the data processing device to obtain XYZ of the triplet value,
(X / Y + Z)) and y = (Y / (X + Y + Z)) and z = xy to convert xy to the color point in the color space,
Wherein the data processing apparatus determines whether the color point corresponding to the transformed color point corresponds to which coordinates in the color space, and the data processing apparatus determines whether the color point corresponding to the polytype of the decision stored in the database Determining a polytype of the sample in comparison with the information; And
A display step in which the display device displays the color space and the color point so that the color point converted and processed in the data processing step can be recognized from the outside; Further comprising:
In the display step, determination result information on the polytype of the sample determined in the determination step is transmitted to the display device by the data processing device and displayed by the display device,
Characterized in that the color space in the data processing step is a color space defined according to the CIE 1931 standard colorimetry system.
Method for analyzing polytypes of crystals using ultraviolet photoluminescence.
delete The method according to claim 1,
A step before the ultraviolet ray irradiation step, comprising: a preparation step of cleaning the sample; Lt; RTI ID = 0.0 &gt; 1, &lt; / RTI &
Method for analyzing polytypes of crystals using ultraviolet photoluminescence.
delete delete delete delete delete The method according to claim 1,
In the ultraviolet ray irradiation step,
Wherein the ultraviolet light emitted from the light source side is filtered by a first optical band pass filter and irradiated to the sample side.
Method for analyzing polytypes of crystals using ultraviolet photoluminescence.
10. The method of claim 9,
Wherein a wavelength of the ultraviolet light that is filtered by the first optical band-pass filter and is incident on the sample side is between 300 nm and 400 nm.
Method for analyzing polytypes of crystals using ultraviolet photoluminescence.
The method according to claim 1,
In the photoluminescence image information acquiring step,
Characterized in that the photoluminescence emitted from the sample side is filtered by a second optical band-pass filter before being incident on the camera device.
Method for analyzing polytypes of crystals using ultraviolet photoluminescence.
12. The method of claim 11,
In the photoluminescence image information acquiring step,
And the wavelength of the photoluminescence filtered by the second optical band-pass filter and incident on the camera device side is larger than 450 nm.
Method for analyzing polytypes of crystals using ultraviolet photoluminescence.

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