KR20080088971A - Method evaluating for crystallization structure of silicon wafer - Google Patents

Abstract

The crystal structure analysis method of a silicon wafer includes a laser beam that excites electrons of a sample, a band pass filter that transforms the laser beam into a laser beam having a wavelength of a specific band, and a photodetector that detects an output intensity of the modified laser beam. A crystal structure analysis method of a silicon wafer performed by measuring a minority carrier lifetime of a sample using a photoluminescence device including a Nd: YVO4 laser beam used as an excitation source. Passing a band pass filter of the photo luminescence device into a laser beam having a wavelength of a band for irradiating a silicon wafer; Irradiating the modified laser beam onto a silicon wafer and detecting an output intensity of the irradiated laser beam with a photodetector of the photoluminescence device; And a band edge filter that converts the output intensity of the laser beam detected from the photodetector into a digital signal by converting the output intensity into a digital signal and narrows the range of the peak based on the highest peak intensity among the peaks. And converting the entire crystal structure of the silicon wafer by converting the digital signal into a digital signal.

Description

Method for analyzing crystal structure of silicon wafer {Method evaluating for crystallization structure of silicon wafer}

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram for explaining a peak represented by a band-edge filter.

2 is a photograph showing a crystal structure of a silicon wafer mapped using a conventional u-PCD method.

3 is a photograph showing a crystal structure of a silicon wafer mapped using a photoluminescence method and a band-edge filter according to an embodiment of the present invention.

4 is a photograph showing a crystal structure of a silicon wafer finely mapped using a photoluminescence method and a band-edge filter according to an embodiment of the present invention.

The present invention relates to a method for analyzing a crystal structure of a silicon wafer, and more particularly, to a method for analyzing a crystal structure of a silicon wafer capable of accurately analyzing the crystal structure inside the silicon wafer by a photoluminescence method. .

BACKGROUND OF THE INVENTION Silicon wafers are widely used for the manufacture of semiconductor devices and substrates for solar cells. However, pure monocrystalline silicon wafers have low efficiency when manufacturing solar cells, and recently, porous silicon or polycrystalline silicon is formed on the surface of pure single crystal silicon wafers for high quality solar cell manufacturing.

The polycrystalline silicon used in the fabrication of high quality solar cell substrates is also required to be of high quality, so that the grain size of the polycrystalline silicon formed on the wafer to ensure uniform quality characteristics and increase the solar cell effect of the single crystal silicon wafer using the polycrystalline silicon. Is increasing.

On the other hand, the crystal structure analysis of the silicon wafer having a polycrystalline silicon structure described above is characterized in that the silicon wafer is characterized by the destruction inspection method using a mixed solution using nitric acid and hydrofluoric acid, the entire wafer without destruction of the silicon wafer There is no way to check for defects or grain size mapping.

The present invention provides a method for analyzing a crystal structure of a silicon wafer capable of accurately analyzing the crystal structure inside the silicon wafer by a photoluminescence method.

The crystal structure analysis method of a silicon wafer according to the present invention includes a laser beam for exciting electrons in a sample, a band pass filter for transforming the laser beam into a laser beam having a wavelength of a specific band, and an output intensity of the modified laser beam. A crystal structure analysis method of a silicon wafer which is performed by measuring a minority carrier lifetime of a sample using a photoluminescence device including a photodetector for detecting a light source. Transforming a Nd: YVO 4 laser beam into a laser beam having a wavelength of a band for irradiating a silicon wafer through a band pass filter of the photoluminescence device; Irradiating the modified laser beam onto a silicon wafer and detecting an output intensity of the irradiated laser beam with a photodetector of the photoluminescence device; And a band edge filter that converts the output intensity of the laser beam detected from the photodetector into a digital signal by converting the output intensity into a digital signal and narrows the range of the peak based on the highest peak intensity among the peaks. And converting the entire crystal structure of the silicon wafer by converting the digital signal into a digital signal.

The Nd: YVO 4 laser beam has a wavelength of 532 nm.

The laser beam for irradiating the silicon wafer has a wavelength of 1050 ~ 1230nm band.

The modified laser beam is characterized in that to irradiate the silicon wafer with a power of 0.1 ~ 10mW.

The mapping resolution of the silicon wafer crystal structure is changed by changing the power of the laser beam.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention provides a method for accurate crystal structure analysis of silicon wafers used in the manufacture of solar cells and semiconductor devices. In detail, the present invention measures the crystal structure of a sample by measuring the minority carrier lifetime. The photoluminescence method of analysis is used.

The output intensity of the digital signal is converted into a digital signal using a band edge filter which converts the output intensity of the irradiated laser into a digital signal to express the shape of the peak and narrows the range of the peak based on the peak of the highest intensity. To clearly map the entire crystal structure of the silicon wafer.

Therefore, the size and shape of the grains formed on the silicon wafer can be clearly determined and analyzed, and the crystal uniformity of the entire silicon wafer can be accurately measured.

On the other hand, a brief analysis of the analysis method using photoluminescence, by scanning a laser beam in the visible or ultraviolet region to the semiconductor sample to determine the electron (Electron) in the low energy state (Valence band) of the system Exciting to a high energy band (Conduction band).

The electrons that are excited and present in a high energy state are then generally at a high energy level and soon descend to the edge of the high energy state by vibration relaxation, of which many electrons fall back into the low energy state To form a recombination with.

Part of the energy emitted by the excited electrons and the recombination process appears as a light spectrum having a specific wavelength, and by analyzing the light spectrum, it is possible to analyze not only structural characteristics of the sample but also defect characteristics and emission characteristics. have.

On the other hand, the crystal structure analysis of a silicon wafer used for fabricating a semiconductor device or a solar cell by the photoluminescence method described above proceeds as a method of measuring the minority carrier lifetime of the silicon wafer. In detail, in the N-type semiconductor and the P-type semiconductor, the number of holes and electrons, that is, the small number of carriers, as the carriers, respectively, is excited.

Conventional microwave photoconductivity decay (u-PCD) method can be used as the optical luminescence method for measuring the minority carrier lifetime of the silicon wafer, the u-PCD method is a microwave region It is a method of scanning a laser source into a sample and measuring it as the information about the change of the wavelength.

However, in the crystal structure analysis of the silicon wafer using the u-PCD method, the measurement sample must be passivated before the measurement and removed after the measurement.

Therefore, in the present invention, the passivation process in the u-PCD method is omitted, the laser is directly irradiated onto the silicon wafer, the output intensity of the irradiated laser is converted into a digital signal, and the peak shape is expressed. Analyze the size and shape of the silicon wafer crystal structure by converting the output intensity into a digital signal and clearly mapping the entire crystal structure of the silicon wafer by using a band edge filter that narrows the range of the peak based on the intensity peak. do.

On the other hand, the crystal structure analysis method of the silicon wafer using the photoluminescence method according to the present invention includes a laser beam for exciting the electrons of the sample, a band pad filter for transforming the laser beam into a laser beam having a wavelength of a specific band Using an optical luminescence device comprising a special filter and a photodetector for detecting the output intensity of the modified laser beam is as follows.

First, a special filter for modifying the shape of the required laser beam, including a band-pass filter, for an ND: YVO4 laser beam having a wavelength of 532 nm used as an excitation source for exciting electrons. ) Into a laser beam with a wavelength in the band 1050-1230 nm.

Then, while irradiating a laser beam having a wavelength of the modified 1050 ~ 1230nm band to the silicon wafer, the output intensity of the irradiated laser beam is detected by a photodetector.

Subsequently, the output intensity of the laser beam detected by the photodetector is converted into a digital signal using a band-edge filter to map the entire crystal structure of the silicon wafer.

Here, the band-edge filter converts the output intensity into a digital signal and expresses it in the form of a peak, and serves to narrow the range of the peak based on the peak of the highest intensity.

1 is a diagram for explaining the peak represented by the band-edge filter.

As shown, the band-edge filter serves to narrow the range of peaks based on the highest intensity peaks from the wide range of peaks formed, and the area of the peaks spread in a large area based on the highest intensity peaks. By reducing the peak shape to form a sharp shape serves to clearly represent the crystal structure.

On the other hand, the mapping picture for the silicon wafer crystal structure using the photoluminescence method according to the present invention can obtain a clear picture than the mapping picture using the μ-PCD method.

2 is a photograph showing a crystal structure of a silicon wafer mapped using a conventional u-PCD method, and FIG. 3 is a silicon mapped using a photoluminescence method and a band-edge filter according to an embodiment of the present invention. 4 is a photograph showing a crystal structure of a wafer, and FIG. 4 is a photograph showing a crystal structure of a silicon wafer finely mapped using a photoluminescence method and a band-edge filter according to an embodiment of the present invention.

2 and 3, the photo of the crystal structure of the silicon wafer mapped using the photoluminescence method and the band-edge filter according to an embodiment of the present invention is silicon mapped using the conventional u-PCD method The resolution is superior to that of the photo of the crystal structure of the wafer. Accordingly, the photo mapped using the photoluminescence method and the band-edge filter clearly represents the crystal structure of the silicon wafer.

Here, the low photoluminescence intensity region corresponds to a region with a short minority carrier lifetime, and in particular, in FIG. 2, corresponding to the minority carrier lifetime distribution in a photograph mapped using a band-edge filter according to the invention, ie In addition, the grain boundary region having low photoluminescence intensity can be clearly identified, and the grain size and shape of the silicon wafer can be analyzed.

In addition, the photo mapped using the photoluminescence method and the band-edge filter according to the present invention has a resolution of about 10 times or more with a resolution of about 10 to 100 times that of the photo mapped using the conventional μ-PCD method. In this case, the crystal structure of the silicon wafer can be obtained more clearly than the etching method or the µ-PCD method, which has been used for the crystal structure analysis of the conventional silicon wafer.

In addition, referring to Figure 4, by adjusting the power (Power) of the laser beam to 0.1 to 10mV, it is possible to adjust the resolution of the mapped picture using the photoluminescence method and the band-edge filter according to the power change. Therefore, an appropriate magnification effect can be obtained and fine mapping is possible.

In addition, according to the present invention, the method of mapping the entire silicon wafer using the photoluminescence method and the band-edge filter can be used not only for inspecting the polycrystalline silicon wafer but also for defect inspection of the single crystal silicon wafer.

As mentioned above, although the present invention has been illustrated and described with reference to specific embodiments, the present invention is not limited thereto, and the following claims are not limited to the scope of the present invention without departing from the spirit and scope of the present invention. It can be easily understood by those skilled in the art that can be modified and modified.

The present invention provides a method for accurate crystal structure analysis of a silicon wafer, and in detail, the present invention measures the crystal structure of a sample by measuring the minority carrier lifetime (Photoluminescence) method Use

At this time, the output intensity of the irradiated laser is converted into a digital signal to express the shape of the peak, and the output intensity is converted into a digital signal by using a band edge filter which narrows the range of the peak based on the peak of the highest intensity. The crystal structure maps the entire crystal structure of the silicon wafer clearly.

Therefore, the size and shape of the grains formed on the silicon wafer can be clearly determined and analyzed, and the crystal uniformity of the entire silicon wafer can be accurately measured.

Claims (5)

Photoluminescence comprising a laser beam for exciting electrons in a sample, a band pass filter for transforming the laser beam into a laser beam having a wavelength of a specific band, and a photodetector for detecting the output intensity of the modified laser beam. A method of analyzing the crystal structure of a silicon wafer performed by measuring a minority carrier lifetime of a sample using a device, Converting an Nd: YVO 4 laser beam used as an excitation source into a laser beam having a wavelength of a band for irradiating a silicon wafer through a band pass filter of the photoluminescence device; Irradiating the modified laser beam onto a silicon wafer and detecting an output intensity of the irradiated laser beam with a photodetector of the photoluminescence device; And A band edge filter which converts the output intensity of the laser beam detected from the photodetector into a digital signal, converting the output intensity into a digital signal, and narrows the range of the peak based on the highest peak intensity among the peaks; Converting into a digital signal to map the entire crystal structure of the silicon wafer; Crystal structure analysis method of a silicon wafer comprising a. The method of claim 1, The Nd: YVO 4 laser beam has a wavelength of 532nm, the crystal structure analysis method of a silicon wafer. The method of claim 1, The laser beam for irradiating the silicon wafer has a wavelength of 1050 ~ 1230nm band, the crystal structure analysis method of the silicon wafer. The method of claim 1, The modified laser beam is irradiated to the silicon wafer with a power of 0.1 ~ 10mW crystal structure analysis method of the silicon wafer. The method of claim 4, wherein And a mapping resolution of the silicon wafer crystal structure by changing the power of the laser beam.

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