A sample preparation device for detecting silicon material

Abstract

The utility model discloses a kind of for detecting silicon material's sample preparation device, it is related to crystal growth technical field, the device includes: furnace body;The furnace body is intermediate frequency furnace, including furnace cavity and heating device, the furnace cavity is formed with the volume V1 containing space, the heating device is used to heat the furnace cavity, the power of the heating device is 30-80KW;Graphite crucible;The graphite crucible is the container of top opening;The graphite crucible is set in the furnace cavity;Ceramic crucible;The ceramic crucible is the container of top opening;The ceramic crucible is set in the graphite crucible.This device can greatly reduce the detection time, and cost is low, accuracy is high.

Description

Technical Field

[0001] This utility model relates to the field of polycrystalline silicon ingot technology, and in particular to a sample preparation device for testing silicon materials. Background Technology

[0002] Cost is one of the main performance indicators for polycrystalline silicon ingots. In the preparation process, polycrystalline silicon ingots are generally not made using virgin polycrystalline silicon powder (purity greater than 99.9999%). Instead, they are made using various complex silicon raw materials (e.g., fragments of virgin polycrystalline silicon powder, silicon powder, broken silicon wafers, and scrapped silicon ingots). However, current incoming material inspection mainly focuses on the performance of the silicon raw materials, using resistivity meters and minority carrier lifetime meters. But because these silicon raw materials are mostly powders with small sizes, typically 0.1-5 cm, resistivity meters and minority carrier lifetime meters are very difficult to use, resulting in inaccurate test results. While using ICP-OES or ICP-MS equipment to test each batch of silicon powder would yield relatively accurate results, these devices can only analyze a few grams of sample at a time and require chemical decomposition, taking at least 1-2 days for each analysis. Furthermore, these testing devices are expensive, leading to excessively high costs.

[0003] Therefore, there is an urgent need for a new sample preparation device for detecting silicon materials. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a sample preparation device for testing silicon material. The device can quickly and conveniently prepare samples to determine the quality of silicon material, and is low in cost and highly accurate.

[0005] This utility model discloses a sample preparation device for detecting silicon material, comprising:

[0006] Furnace body; the furnace body is a medium-frequency furnace, including a furnace cavity and a heating device. The furnace cavity forms a accommodating space with a volume of V1. The heating device is used to heat the furnace cavity, and the power of the heating device is 30-80KW.

[0007] Graphite crucible; the graphite crucible is a container with an open top; the graphite crucible is disposed inside the furnace cavity;

[0008] A ceramic crucible; the ceramic crucible is a container with an open top; the ceramic crucible is disposed inside the graphite crucible.

[0009] In one alternative embodiment, the graphite crucible has an inner surface and an outer surface, the outer surface defining an outer volume V2 of the graphite crucible, and the inner surface defining an inner volume of the graphite crucible; wherein the outer volume V2 of the graphite crucible accounts for more than 80% of the volume V1 of the furnace cavity.

[0010] In one alternative embodiment, the ceramic crucible has an inner surface that defines the inner diameter or inner side length of the ceramic crucible, wherein the inner diameter or inner side length of the ceramic crucible is 5% to 30% of the inner diameter or inner side length of the graphite crucible; and / or, the height of the ceramic crucible is 1 / 3 to 1 / 2 the height of the graphite crucible.

[0011] In one alternative embodiment, the intermediate frequency furnace includes a cooling device.

[0012] In one alternative embodiment, the inner diameter or inner side length of the ceramic crucible is 5-30 cm.

[0013] In one alternative embodiment, the height of the ceramic crucible is 5-30 cm.

[0014] In one alternative embodiment, the purity of the silica in the ceramic crucible is greater than or equal to 99.9%.

[0015] In one alternative embodiment, a cover plate is provided above the graphite crucible.

[0016] In one alternative embodiment, the cover plate is made of carbon or graphite.

[0017] In one alternative embodiment, the inner and outer surfaces of the graphite crucible are coated with a silicon nitride or silicon carbide coating.

[0018] In one alternative embodiment, the inner surface of the ceramic crucible is coated with a silicon nitride coating.

[0019] Compared with the prior art, the present invention provides a sample preparation device for testing silicon material, which completes the melting of silicon material within 30-60 minutes, thereby significantly reducing the testing time. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the present invention and constitute a part of this invention, illustrate exemplary embodiments of the present application and are used to explain the present invention, but do not constitute an undue limitation of the present invention. In the drawings:

[0021] Figure 1 A front cross-sectional schematic view of one embodiment of the apparatus of this application is shown;

[0022] Figure 2It shows Figure 1 A top-view cross-sectional diagram of the device shown.

[0023] Figure labels;

[0024] 10 - Medium frequency furnace; 20 - Graphite crucible; 30 - Ceramic crucible; 40 - Cover plate Detailed Implementation

[0025] Embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise expressly specified. "Several" means one or more, unless otherwise expressly specified.

[0027] like Figure 1-2 As shown, this utility model provides a sample preparation device for detecting silicon material, comprising:

[0028] Furnace body 10; Furnace body 10 is a medium-frequency furnace, which is an electromagnetic induction medium-frequency induction furnace. The medium-frequency furnace is equipped with a heating device, which is located below the furnace body 10. The power of the heating device is set between 30-80KW. The medium-frequency furnace includes a furnace cavity, and a receiving space is formed inside the furnace cavity. The volume of the receiving space is V1.

[0029] Graphite crucible 20; Graphite crucible 20 is a container with an open top, having an inner surface and an outer surface. Graphite crucible 20 can be round or square. The dimensions of a round graphite crucible 20 include its inner diameter, outer diameter, and height; a square graphite crucible 20 has its inner side length, outer side length, and height; the inner diameter or inner side length and height form the inner volume of the graphite crucible 20; the outer diameter or outer side length and height form the outer volume of the graphite crucible 20, which is V2.

[0030] In one alternative configuration, the outer volume of the graphite crucible 20 occupies more than 80% of the furnace cavity volume, such as 80%, 85%, or 90%. This allows the graphite crucible 20 to be heated rapidly and transfers heat to the ceramic crucible 30, accelerating the melting time of the silicon material and thus saving the silicon material testing time.

[0031] In one alternative embodiment, the inner diameter (diameter of the graphite crucible defined by the inner surface) or the inner side length (side length of the graphite crucible defined by the inner surface) of the graphite crucible 20 is 100-200 cm; for example, it can be 100 cm, 110 cm, 120 cm, 150 cm or 200 cm.

[0032] In one alternative embodiment, the outer diameter (diameter of the graphite crucible defined by the outer surface) or the outer side length (side length of the graphite crucible defined by the outer surface) of the graphite crucible 20 is 140-240 cm; for example, it can be 140 cm, 150 cm, 160 cm, 170 cm, 180 cm, 190 cm, 200 cm, 210 cm, 220 cm, 230 cm or 240 cm.

[0033] In one alternative configuration, the height of the graphite crucible 20 is 5-35cm; for example, it can be 5cm, 10cm, 15cm, 20cm, 25cm, 28cm, 30cm or 35cm.

[0034] In one alternative approach, the inner and outer surfaces of the graphite crucible 20 are coated with a silicon nitride or silicon carbide coating, which can slow down the decomposition rate of graphite in the air atmosphere, prevent the silicon powder from being contaminated, and avoid inaccurate test results.

[0035] A ceramic crucible 30; the ceramic crucible 30 is a container with an open top, specifically a silicon dioxide ceramic crucible 30. The ceramic crucible 30 has an inner surface and an outer surface. The ceramic crucible 30 can be round or square. The dimensions of a round ceramic crucible 30 include its inner diameter, outer diameter, and height; the dimensions of a square ceramic crucible 30 include its inner side length, outer side length, and height; the inner diameter or inner side length and the height form the inner volume of the ceramic crucible 30; the outer diameter or outer side length and the height form the outer volume of the ceramic crucible 30.

[0036] In one alternative embodiment, the inner diameter or inner side length of the ceramic crucible 30 is 5% to 30% of the inner diameter or inner side length of the graphite crucible 20; for example, it can be 5%, 10%, 15%, 20%, 25%, or 30%; thus, multiple ceramic crucibles 30 can be placed in one graphite crucible 20, allowing the quality of multiple batches of silicon raw materials to be tested at one time.

[0037] In one alternative, the height of the ceramic crucible 30 is 1 / 3 to 1 / 2 of the height of the graphite crucible 20, for example, it can be 1 / 3, 1 / 2, 3 / 3 or 1; this allows the ceramic crucible 30 to be better heat-transferred and to melt the silicon material.

[0038] In one alternative embodiment, the inner diameter (diameter of the ceramic crucible 30 defined by the inner surface) or the inner side length (side length of the ceramic crucible 30 defined by the inner surface) of the ceramic crucible 30 is 5-30 cm; for example, it can be 5 cm, 10 cm, 15 cm, 20 cm, 25 cm or 30 cm.

[0039] In one alternative embodiment, the outer diameter (diameter of the ceramic crucible defined by the outer surface) or outer side length (side length of the ceramic crucible defined by the outer surface) of the ceramic crucible 30 is 10-45 cm; for example, it can be 5 cm, 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, 35 cm, 40 cm or 45 cm.

[0040] In one alternative configuration, the height of the ceramic crucible 30 is 5-30cm; for example, it can be 5cm, 10cm, 15cm, 20cm, 25cm or 30cm.

[0041] In one alternative embodiment, the ceramic crucible 30 is a silicon dioxide ceramic crucible 30, and the purity of the silicon dioxide is greater than or equal to 99.9%. This allows for more accurate test results.

[0042] In an alternative embodiment, a cover plate 40 is provided above the graphite crucible 20; the cover plate 40 can be made of carbon or graphite, which allows the heat to be more concentrated to melt the silicon material, thereby further shortening the detection time.

[0043] In one alternative approach, the intermediate frequency furnace includes a cooling device, such as a cold water pipe, a cold air pipe, or a separate cold air and cold water pipeline installed inside the furnace casing. This allows the cooling device to be turned on after the heating device of the intermediate frequency furnace is turned off, enabling the silicon material to cool down rapidly. This not only saves testing time but also makes the judgment results more accurate.

[0044] This utility model provides a specific method for using a sample preparation device for detecting silicon material, the steps of which include:

[0045] Step 1: Load silicon powder into a ceramic crucible; place the ceramic crucible into a graphite crucible; place the graphite crucible inside the furnace cavity of the medium-frequency furnace;

[0046] Step 2: Turn on the heating device of the medium frequency furnace and raise the heating device to above 45kW within a certain period of time to melt the silicon powder; and during the melting process, keep the power of the medium frequency furnace above 45kW.

[0047] Step 3: After the silicon powder melts, turn off the heating device of the medium frequency furnace and allow the silicon powder to cool to room temperature to obtain a small silicon ingot prepared using the silicon powder;

[0048] Step 4: Remove the cooled small silicon ingot and cut off the middle position. Measure the resistivity value R and / or minority carrier lifetime value τ of the small silicon ingot; compare it with the threshold values ​​of the resistivity value and / or minority carrier lifetime value to determine the quality of the silicon powder.

[0049] In one alternative approach, the silicon material is deemed to be of acceptable quality when the resistivity R is within the threshold range of the resistivity.

[0050] In one specific embodiment, the resistivity threshold range is 1~3 Ω·cm. When the resistivity R value is within 1~3 Ω·cm, the quality of the silicon material is deemed to be qualified.

[0051] In one alternative approach, the minority carrier lifetime value τ is converted into a true minority carrier lifetime value τ1 using a formula. When the true minority carrier lifetime value τ1 is greater than the threshold value of the minority carrier lifetime value, the silicon material is deemed to be of qualified quality.

[0052] Because minority carrier lifetime is affected by oxygen atom diffusion, there is a deviation between the measured and actual values. Since oxygen atom diffusion is related to the melting time of silicon, this application aims to complete silicon melting within 30-60 minutes. Through extensive experiments, the inventors discovered a relationship between the actual and measured minority carrier lifetime values ​​of silicon powder: τ1 = τ + A / t, where τ is the measured minority carrier lifetime value of silicon powder (in μs); τ1 is the actual minority carrier lifetime value of silicon powder (in μs); t is the melting time, which is between 30 and 60 minutes (e.g., 30, 40, or 60 minutes); and A is a fixed value that is strongly correlated with the melting time t. Through numerous experiments, the inventors found that A = (200-180) × (t-30) / 30 + 180. When the melting time t equals 30 minutes, A = 180; as time increases, A gradually increases; when t equals 60 minutes, A = 200; when the melting time t is any value between 30 and 60, A = (200-180) × (t-30) / 30 + 180.

[0053] In a specific embodiment, the threshold for minority carrier lifetime is 1 μs. Substituting τ into the formula τ1=τ+A / t, where τ is the tested minority carrier lifetime value of silicon powder, τ1 is the actual minority carrier lifetime value of silicon powder, t is the melting time, and A is a fixed value between 180 and 200, the value of τ1 is obtained. When the value of τ1 is greater than 1 μs, the silicon powder is determined to be of qualified quality.

[0054] In a specific embodiment, such as Figure 1-2As shown, seven ceramic crucibles 30 with a silicon dioxide purity of 99.9% were selected. The inner diameter of each crucible 30 was 5 cm, the outer diameter was 13 cm, and the height was 30 cm. Silicon powder from batches 1-7 was loaded into the ceramic crucibles 30. The ceramic crucibles 30 with the silicon powder were then placed into a graphite crucible 20 located in the furnace cavity of a medium-frequency furnace 10. The medium-frequency furnace 10 was a medium-frequency induction furnace. The graphite crucible 20 had an inner diameter of 100 cm, an outer diameter of 140 cm, and a height of 35 cm. The outer volume of the graphite crucible occupied more than 80% of the furnace cavity volume. The graphite crucible was then covered with a carbon-carbon cover plate 40.

[0055] The heating device of the intermediate frequency furnace 10 is turned on, and the temperature inside the furnace cavity is stabilized at around 1430℃ by adjusting the power. The power of the intermediate frequency furnace is then increased to 45kW within 4 minutes. After the silicon powder melts, the heating device of the intermediate frequency furnace 10 is turned off, and the silicon powder is allowed to cool to room temperature. The temperature of the intermediate frequency furnace is controlled by a thermocouple, and the heating time of the furnace is recorded. The melting time t of the silicon powder is found to be 42 minutes. Using this application, the melting time of silicon powder is within 35-60 minutes, significantly reducing the testing and evaluation time of the silicon powder.

[0056] Analysis of the physical image of the small silicon ingot prepared in batch 1 of this application embodiment shows that the small silicon ingot has a complete structure and can be used for subsequent resistivity and minority carrier lifetime testing. A sample block with a length of 3cm, a width of 3cm, and a thickness of 5mm was made from the middle position of the cooled small silicon ingot. The resistivity value R and the minority carrier lifetime value τ of the sample block were measured. The threshold range for resistivity was set to 1~3Ω·cm; the threshold for minority carrier lifetime was set to 1μs. The batch's qualification was determined based on the R and τ data. It is understood that due to the high impurity content in the original silicon material, impurity points may appear in the edge area of ​​the small silicon ingot; simultaneously, due to the rapid heating rate, cracks may exist in some areas of the small silicon ingot. However, the aforementioned edge impurity points and local cracks are all located in non-detection areas and will not affect the test results of the subsequently cut middle area sample block.

[0057] The minority carrier lifetime value τ is converted into the actual minority carrier lifetime value τ1, and the quality of each batch is determined based on the data of τ1.

[0058] Other silicon powder materials from batches 1-7 were cast into polycrystalline silicon ingots, and the center position of the central region of the polycrystalline silicon ingot was cut out to make a sample block with a length of 3cm, a width of 3cm and a thickness of 5mm. The resistivity value R1 of the sample block and the minority carrier lifetime value τ2 of the sample were measured.

[0059] The resistivity was measured using an RT100 resistivity meter, which averaged the values ​​at four points on the edge of the sample surface and at the center. The minority carrier lifetime was measured using a SemilabWT2000 minority carrier lifetime meter, which averaged the minority carrier lifetime values ​​across the entire surface.

[0060] Table 1-2 below shows the final judgment results of different batches of silicon powder in the examples. As can be seen from the table:

[0061] (1) The resistivity of silicon powder tested by this application is highly accurate, with an accuracy rate of up to 100%. As shown in the seven batches of this embodiment, for products in the range of 1-3Ω·cm, the resistivity R of the sample prepared by this application is in the same range as the resistivity R1 of the cast polycrystalline silicon ingot. For products that exceed the range of 1-3Ω·cm (e.g., batch 3 and batch 7), this application can also accurately determine the resistivity.

[0062] (2) The accuracy of minority carrier lifetime determination of silicon powder tested using this application is 80%. τ can basically characterize the minority carrier lifetime τ2 of cast polycrystalline silicon ingots. The converted minority carrier lifetime τ1 (A=188) is closer to the minority carrier lifetime τ2 of cast polycrystalline silicon ingots, with an accuracy of up to 100%. For example, for batch 6, the data τ after testing according to this application is 0.95μs, which is not a qualified product compared to the threshold of 1μs. However, after conversion, τ1 is 5.40μs, which is a qualified product. The result is also closer to the minority carrier lifetime τ2 of cast polycrystalline silicon ingots of 6.75μs. The result shows that it is a qualified product.

[0063] Therefore, the sample preparation device for testing silicon material provided in this application can quickly determine the quality of silicon powder and accurately determine the quality of the original silicon powder before the preparation of polycrystalline silicon ingots. Moreover, this application is simple and convenient and easy to promote in large quantities.

[0064] Table 1 Resistivity determination results

[0065]

[0066] Table 2 Results of minority birth rate lifespan determination

[0067]

[0068] Although this application has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the accompanying drawings, disclosure, and appended claims, will understand and implement other variations of the disclosed embodiments in carrying out the claimed application. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple instances. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0069] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of this application as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from the spirit and scope of this application. Thus, if such modifications and modifications of this application fall within the scope of the claims of this application and their equivalents, this application is also intended to include such modifications and modifications.

Claims

1. A sample preparation apparatus for detecting silicon material, characterized in that, The device includes: Furnace body; the furnace body is a medium-frequency furnace, including a furnace cavity and a heating device. The furnace cavity forms a accommodating space with a volume of V1. The heating device is used to heat the furnace cavity, and the power of the heating device is 30-80KW. Graphite crucible; the graphite crucible is a container with an open top; the graphite crucible is disposed inside the furnace cavity; A ceramic crucible; the ceramic crucible is a container with an open top; the ceramic crucible is disposed inside the graphite crucible.

2. The apparatus as claimed in claim 1, characterized in that, The graphite crucible has an inner surface and an outer surface. The outer surface of the graphite crucible defines the outer volume V2 of the graphite crucible, and the inner surface of the graphite crucible defines the inner volume of the graphite crucible. The outer volume V2 of the graphite crucible accounts for more than 80% of the volume V1 of the furnace cavity.

3. The apparatus as described in claim 1, characterized in that, The ceramic crucible has an inner surface that defines the inner diameter or inner side length of the ceramic crucible, wherein the inner diameter or inner side length of the ceramic crucible is 5% to 30% of the inner diameter or inner side length of the graphite crucible; and / or, the height of the ceramic crucible is 1 / 3 to 1 / 2 of the height of the graphite crucible.

4. The apparatus as claimed in claim 1, characterized in that, The medium-frequency furnace includes a cooling device.

5. The apparatus as described in claim 3, characterized in that, The inner diameter or inner side length of the ceramic crucible is 5-30 cm, and / or the height of the ceramic crucible is 5-30 cm.

6. The apparatus as claimed in claim 1, characterized in that, The purity of silicon dioxide in the ceramic crucible is greater than or equal to 99.9%.

7. The apparatus as claimed in claim 1, characterized in that, A cover plate is provided on top of the graphite crucible.

8. The apparatus as claimed in claim 7, characterized in that, The cover plate is made of carbon or graphite.

9. The apparatus as claimed in claim 1, characterized in that, The inner and outer surfaces of the graphite crucible are coated with silicon nitride or silicon carbide coatings.

10. The apparatus as claimed in claim 1, characterized in that, The inner surface of the ceramic crucible is coated with silicon nitride.

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