A method for evaluating the existence forms of hydrogen and determining its relative content in silicon materials.

Abstract

This invention discloses a method for evaluating the existing forms of hydrogen and determining its relative content in silicon materials. The method utilizes diffuse reflectance Fourier transform infrared spectroscopy combined with a hydrogen content analyzer. The annealing temperature range is selected as 450-1000℃, with a difference of 150℃ or 200℃ between different target annealing temperatures. The holding time is 0.5, 1, 2, 3, or 6 hours, and the heating rate is 10℃ / min. The wavenumber range for diffuse reflectance Fourier transform infrared spectroscopy is 500-2500 cm⁻¹. ‑1 The resolution is 4cm. ‑1 Select 630 cm ‑1 900cm ‑1 2000 cm ‑1 And 2100cm ‑1 As a silicon material, SiH x The invention provides a rough determination of the form and relative content of hydrogen in silicon materials, offering theoretical and practical reference for designing annealing and dehydrogenation conditions for silicon materials. The DRIFTS characteristic absorption peak is observed.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen content analysis and testing technology, specifically relating to a method for evaluating the existing forms of hydrogen and determining its relative content in silicon materials. Background Technology

[0002] In the preparation and application of silicon materials, hydrogen, as a key impurity element, exhibits complex and dual effects. Specifically, in granular polycrystalline silicon materials prepared using silane fluidized bed technology, the hydrogen content is high. This hydrogen is rapidly released during the silicon melting stage, triggering the so-called "hydrogen jump" phenomenon, which causes silicon melt sputtering, thereby disrupting the stability of the crystal growth process and reducing the service life of the thermal field. On the other hand, in the manufacturing process of silicon-based solar cells, hydrogen can be introduced into the silicon material through plasma-assisted hydrogen-rich thin film deposition or hydrogen ion implantation, effectively passivating dangling bonds on the surface of the solar cell, thus significantly improving minority carrier lifetime and positively impacting cell performance.

[0003] Previous studies have shown that hydrogen in silicon materials escapes during annealing, and the efficiency of this escape process is significantly affected by annealing temperature and time. However, to date, the specific forms and relative content of hydrogen in particulate silicon, as well as the fundamental mechanism by which the hydrogen removal rate changes with temperature and time during annealing dehydrogenation, have not been fully and thoroughly investigated. This lack of scientific understanding greatly hinders further optimization of process design, making it difficult to effectively mitigate the adverse effects of hydrogen in silicon materials, while also preventing the full amplification of its beneficial effects. Therefore, in-depth exploration of the forms of hydrogen in particulate silicon and its annealing dehydrogenation mechanism is of crucial scientific significance and application value for improving the growth quality of Czochralski silicon crystals and optimizing the hydrogen passivation process for solar cells.

[0004] A diffuse reflectance Fourier transform infrared spectrometer is an advanced infrared spectroscopy analysis device that operates in reflectance mode. It can accurately convert the light signal reflected from a sample into an infrared spectrum, thereby revealing key information such as the sample's molecular structure and chemical bonds. This instrument is renowned for its non-destructive testing capabilities and high-precision measurement performance, and is particularly suitable for direct and accurate measurement of solid powders and complex multi-component samples. A hydrogen content analyzer employs high-temperature melting technology to ensure that all forms of hydrogen in the sample are completely released and converted into hydrogen gas. By accurately measuring changes in thermal conductivity, the total hydrogen content in the sample can be accurately determined. Based on these two methods, this invention addresses the aforementioned technical problems. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a method for evaluating the existence forms of hydrogen and determining its relative content in silicon materials. This method involves annealing silicon materials at different temperatures, measuring the hydrogen content, and performing diffuse reflectance Fourier transform infrared spectroscopy (DFT) measurements. The changes in hydrogen content are compared with the Si-H content in the DFT DFT spectrum. x The changes in bond absorption intensity were analyzed, and the removal temperatures and relative contents of different forms of hydrogen in silicon materials were determined. This was achieved through the following technical solutions:

[0006] A method for evaluating the existing forms of hydrogen and determining its relative content in silicon materials, comprising the following steps:

[0007] Step 1: Take a sample of virgin silicon material and measure its hydrogen content using a hydrogen content analyzer. Perform the test twice, record the hydrogen content, and take the average value, which is denoted as [H]0.

[0008] Step 2: Take a sample of virgin silicon material, crush and grind it into 0.15-0.25mm fragments using a mortar and pestle, and perform DRIFTS testing under vacuum; the wavenumber range of the test is 2500-500cm⁻¹. -1 , with a resolution of 4cm -1 .

[0009] Step 3: Take another batch of virgin silicon material samples from the same batch, divide them into multiple groups, and heat them to different target annealing temperatures at a heating rate of 10℃ / min, with different holding times, and then cool them in the furnace. The annealing temperature range is 450-1000℃, the difference between different target annealing temperatures is 150℃ or 200℃, and the holding time is 0.5, 1, 2, 3 or 6 hours.

[0010] Step 4: Divide each group of annealed silicon material samples from Step 3 into two parts. Test the hydrogen content of one part, following the same procedure as in Step 1. Test the other part using DRIFTS, following the same procedure and parameters as in Step 2.

[0011] Step 5: Plot the curve of hydrogen content as a function of annealing temperature and time based on the average hydrogen content of each group of samples measured in Step 4.

[0012] Step Six: Based on the data obtained in Step Four, plot the DRIFTS stacking diagrams of silicon materials annealed at the same annealing temperature but different annealing times, as well as the DRIFTS stacking diagrams of silicon materials annealed at the same annealing time but different annealing temperatures; compare the SiH values ​​in the DRIFTS diagrams. x The intensity variation of the characteristic peak, with the characteristic peak located at 630 cm⁻¹. -1 , 900cm -1 2000cm -1 and 2100cm -1 about.

[0013] Step 7: Compare the temperature and time at which the hydrogen content changes significantly in the curve described in Step 5 with the temperature and time at which the SiHx absorption intensity changes significantly in the diffuse reflectance Fourier transform infrared spectrum described in Step 6, and analyze the state of hydrogen in silicon materials.

[0014] Step 8: Calculate the proportion of hydrogen in a certain form relative to all forms of hydrogen based on the ratio of the amount of hydrogen removed in that form to the initial content of [H]0. Calculate the percentage content of each form of hydrogen using the following formula:

[0015] H 1p = [H]1 / [H]0 × 100%

[0016] In the formula, H 1p [H]1 represents the percentage of hydrogen existing in the H1 form out of all hydrogen forms; when [H]1 in this formula refers to the content of hydrogen removed in a certain stage, [H]1... 1p This represents the dehydrogenation rate.

[0017] This invention combines DRIFTS technology with a hydrogen content analyzer to accurately determine the existing forms and relative content of hydrogen in silicon materials. Specifically, this method utilizes DRIFTS testing and hydrogen content analysis techniques to systematically measure the hydrogen content in both virgin and annealed silicon material samples, focusing on SiH. x The absorption intensity of the relevant characteristic peaks and the hydrogen content were also analyzed. Furthermore, this invention analyzed the correlation between these measurement results and annealing temperature and time, thereby clearly revealing the specific forms of hydrogen and their relative proportions in silicon materials.

[0018] The implementation of this method not only contributes to a deeper understanding of the annealing behavior of hydrogen in silicon materials, but also provides valuable insights into the underlying scientific mechanisms. Therefore, this invention provides a solid theoretical basis and practical guidance for the optimized design of dehydrogenation temperature and time during the annealing process of silicon materials. Attached Figure Description

[0019] Figure 1 The figure shows the DRIFTS spectrum of the native silicon material sample in the example, with the wave values ​​of each absorption peak and their assignments marked.

[0020] Figure 2 The figure shows the curves of hydrogen content versus annealing time for silicon material samples annealed at different temperatures in the examples.

[0021] Figure 3 The diagram shows the DRIFTS of silicon materials annealed at different temperatures and times in the examples. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments in order to better understand the technical solution.

[0023] This invention provides a method for evaluating the existing forms of hydrogen and determining its relative content in silicon materials, comprising the following steps:

[0024] S1: Hydrogen content test of virgin silicon material sample: Take 0.5g of virgin silicon material sample and place it in a graphite crucible. After rapid melting in a hydrogen content analyzer, obtain the hydrogen content value. Perform the test twice and calculate the average value.

[0025] S2: DRIFTTS test of virgin sample: Take 1g of virgin silicon material sample and grind it into fragments of about 0.2mm in a quartz mortar to expose the internal structure of the silicon material as much as possible. Perform a DRIFTTS test on the fragments, with a wavenumber range of 2500-500cm⁻¹. -1 , with a resolution of 4cm -1 .

[0026] S3: Silicon Material Annealing: Weigh 18g of silicon material and place it in a corundum ceramic boat. Starting from room temperature, heat the material in an argon atmosphere at a rate of 10℃ / min to different target annealing temperatures, hold at these temperatures for different times, and then cool with the furnace. The annealing temperature range is 450-1000℃, with a difference of 150℃ or 200℃ between different target annealing temperatures, and holding times of 0.5, 1, 2, 3, or 6 hours.

[0027] S4: Hydrogen content test of annealed silicon material: Test and record the hydrogen content of the annealed silicon material according to the steps described in S1.

[0028] S5: DRIFTS test of annealed silicon material: Perform DRIFTS test on the annealed silicon material according to the steps described in S2.

[0029] S6: Plotting and Analysis: Plot the hydrogen content in silicon materials annealed at different temperatures as a function of annealing time, and plot the DRIFTS spectra of silicon material samples annealed at different temperatures and for different times. Analyze the hydrogen content and the SiH content in the DRIFTS spectra. x The relationship between the absorption intensity of the relevant peaks and the annealing temperature and time reveals the form in which hydrogen exists in silicon materials.

[0030] S7: Calculate the relative content of a certain form of hydrogen: Calculate the percentage content of each form of hydrogen according to the following formula:

[0031] H 1p = [H]1 / [H]0 × 100%

[0032] In the formula, H 1p[H]1 represents the percentage of hydrogen existing in the H1 form out of all hydrogen forms. When [H]1 in this formula refers to the amount of hydrogen removed in a certain stage, [H]1... 1p This represents the dehydrogenation rate.

[0033] Example

[0034] A method for determining the existing forms and relative content of hydrogen in silicon materials using diffuse reflectance Fourier transform infrared spectroscopy and a hydrogen content analyzer is described below:

[0035] 1) Take a 0.5g sample of native granular polycrystalline silicon material and perform two hydrogen content measurements using a hydrogen content analyzer to ensure instrument accuracy. The first measurement showed a hydrogen content of 21.6 ppmw (parts per million by weight), and the second measurement showed 22.5 ppmw. The calculated average value was 22.1 ppmw.

[0036] 2) Take another 1 gram of native granular polycrystalline silicon material sample, crush and refine it into fragments of approximately 0.2 mm in a quartz mill. Subsequently, the infrared spectrum of the fragments was measured using a diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) instrument. The results are shown in the appendix. Figure 1 .

[0037] 3) Sixteen annealing experiments were designed and executed, each using 18 grams of virgin granular polycrystalline silicon material from the same batch. The samples were placed in corundum ceramic boats. Eight groups of samples were heated to 450 or 650°C at a rate of 10°C / min under an argon atmosphere from room temperature, held for 1, 2, 3, and 6 hours respectively, and then cooled in the furnace. The other eight groups were heated to 800 or 1000°C at a rate of 10°C / min under an argon atmosphere from room temperature, held for 0.5, 1, 2, and 3 hours respectively, and then cooled in the furnace.

[0038] 4) Repeat the hydrogen content test in step 1) and the DRIFTS spectrum determination in step 2) for all annealed samples to ensure that the test conditions are consistent with those of the original samples. The hydrogen content data from the test results are summarized in Table 1.

[0039] Table 1

[0040]

[0041] 5) Calculate the dehydrogenation rate according to the aforementioned formula based on the test data, and plot the curves of hydrogen content and dehydrogenation rate in granular polycrystalline silicon material as a function of annealing temperature and time. The results are as follows: Figure 2 .

[0042] 6) Summarize and analyze the DRIFTS spectra of all samples, and plot a comprehensive spectrum to demonstrate the infrared spectral characteristics of granular polycrystalline silicon materials under different annealing conditions. The results are attached. Figure 3 As shown in the figure. The first row of data shows the effect of temperature when the annealing time is the same, and the second row shows the effect of annealing time when the annealing temperature is the same.

[0043] 7) Combining hydrogen content test data and curves with the SiH content in the DRIFTS spectrum x Analysis of the changes in absorption peak intensity revealed the presence of hydrogen in the particles. From 450 to 800℃, the hydrogen content in the granular polycrystalline silicon material gradually decreased. After annealing at 650℃ for 6 hours, the dehydrogenation rate reached 45%. However, within this temperature range, the SiH content in the DRIFTS spectrum remained relatively low. x The intensity of the absorption peak did not decrease significantly, indicating that the main hydrogen removed in this temperature range is non-infrared reactive hydrogen, such as hydrogen molecules (H2) or hydrogen atoms (H). These types of hydrogen are relatively easy to remove due to their poor thermal stability. When the annealing temperature is increased to 1000℃, annealing for only 0.5 hours can cause a sharp decrease in the hydrogen content of granular polycrystalline silicon materials, with a dehydrogenation rate as high as 51%. However, even in granular polycrystalline silicon materials annealed at 1000℃ for 1 hour, the SiH content in the DRIFTTS spectrum... x The intensity of the absorption peak decreased only slightly compared to the sample annealed at 800℃ for 1 hour. This result indicates that in the initial stage of annealing at 1000℃, the main hydrogen removed are still non-infrared reactive hydrogen molecules or atoms. Furthermore, the dehydrogenation rate after annealing at 1000℃ for 0.5 hours is similar to that after annealing at 650℃ for 6 hours, further confirming that this type of hydrogen accounts for between 45% and 51% of the total hydrogen content, and its thermal stability at high temperatures is significantly reduced, making it very easy to remove. However, when the treatment time at 1000℃ exceeds 0.5 hours, the dehydrogenation rate decreases significantly. Meanwhile, the SiH concentration in the DRIFTTS spectrum... x The intensity of the absorption peak, however, showed a significant decrease. This change indicates that the SiH+ ions that began to be removed during prolonged annealing at high temperatures are actually SiH+. x The hydrogen in this part is more thermally stable and more difficult to remove, accounting for approximately 50% of the total hydrogen content.

Claims

1. A method for evaluating the existing forms of hydrogen and determining its relative content in silicon materials, characterized in that... This method utilizes diffuse reflectance Fourier transform infrared spectroscopy in conjunction with a hydrogen content analyzer, and specifically includes the following steps: 1) Take a sample of native silicon material, measure the hydrogen content using a hydrogen content analyzer, perform the test twice, record the hydrogen content and take the average value, which is recorded as [H]0; 2) Take a sample of raw silicon material, crush and grind it into fragments with a particle size of 0.15-0.25 mm using a mortar and pestle, and perform DRIFTS test under vacuum; 3) Take additional samples of virgin silicon material from the same batch, and divide them into the following groups: The samples were heated from room temperature to 450°C in an argon atmosphere at a heating rate of 10°C / min, held at that temperature for 1, 2, 3, and 6 hours respectively, and then cooled with the furnace. The samples were heated from room temperature to 650°C in an argon atmosphere at a heating rate of 10°C / min, held at that temperature for 1, 2, 3, and 6 hours respectively, and then cooled with the furnace. The sample was heated from room temperature to 800°C at a heating rate of 10°C / min under an argon atmosphere. Keep warm for 0.5, 1, 2, and 3 hours respectively, then cool with the furnace; The sample was heated from room temperature to 1000℃ in an argon atmosphere at a heating rate of 10℃ / min. Keep warm for 0.5, 1, 2, and 3 hours respectively, then cool with the furnace; 4) Divide each group of annealed silicon material samples from step 3) into two parts. One part is tested for hydrogen content, and the testing procedure is the same as in step 1. The other part is tested for DRIFTS, and the testing procedure and parameters are the same as in step 2. 5) Based on the average hydrogen content of each group of samples measured in step 4), plot the curve of hydrogen content change with annealing temperature and time. 6) Based on the data obtained in step 4), draw the DRIFTS stack diagrams of silicon materials annealed for different times at the same annealing temperature, and the DRIFTS stack diagrams of silicon materials annealed at different temperatures for the same annealing time. 7) Compare the temperature and time at which the hydrogen content changes significantly in the curve described in step 5) with the SiH content in the DRIFTS stacked diagram described in step 6). x The temperature and time at which the absorption intensity changes significantly were analyzed to determine the state of hydrogen in silicon materials. 8) Calculate the proportion of hydrogen in a certain form relative to all forms of hydrogen based on the ratio of the amount of hydrogen removed in that form to the initial content of [H]0, and calculate the percentage content of each form of hydrogen using the following formula: H 1p =[H]1 / [H]0×100% In the formula, H 1p [H]1 represents the percentage of hydrogen existing in the H1 form out of all hydrogen forms; when [H]1 in this formula refers to the content of hydrogen removed in a certain stage, [H]1... 1p This represents the dehydrogenation rate.

2. The method for evaluating the existence form and determining the relative content of hydrogen in silicon materials as described in claim 1, characterized in that... The wavenumber range for DRIFTS testing is 2500-500 cm⁻¹. -1 , with a resolution of 4cm -1 .

3. The method for evaluating the existence forms and determining the relative content of hydrogen in silicon materials as described in claim 1, characterized in that... Select 630 cm -1 900cm -1 2000 cm -1 And 2100cm -1 As a silicon material, SiH x The characteristic absorption peak of DRIFTS.

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