Method for detecting metal impurities in polysilicon

Abstract

The application discloses a method for detecting metal impurities in polysilicon and relates to the technical field of polysilicon metal detection. The method comprises the following steps: cleaning a plurality of containers, randomly selecting one or more first containers from the plurality of containers, adding a constant volume liquid into the first containers, detecting the impurity content of the constant volume liquid in the first containers, so that the content of each metal impurity in the constant volume liquid in the first containers meets the requirements, using the containers to weigh polysilicon samples, and in the weighing process, randomly selecting one or more second containers from the plurality of containers, using the second containers to monitor the metal impurities in the open environment, and after the weighing is completed, adding a constant volume liquid into the second containers, detecting the impurity content of the constant volume liquid in the second containers, so that the content of each metal impurity in the constant volume liquid in the second containers meets the requirements.

Description

Technical Field

[0001] This invention relates to the field of polycrystalline silicon metal detection technology, and more particularly to a method for detecting metal impurities in polycrystalline silicon. Background Technology

[0002] The current standard for testing metals on the surface of polycrystalline silicon is GB / T 24582-2023, and the standard for testing metals in the matrix is ​​GB / T 37049-2018. However, there are currently no monitoring measures in the testing process, making it impossible to trace the source of contamination during the testing process or to effectively control the source of contamination in the sample. This results in inaccurate test results that cannot accurately reflect the impurity content of the sample. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a method for detecting metallic impurities in polycrystalline silicon to solve the technical problems of being unable to trace the source of contamination during the sample detection process and being unable to effectively control the source of contamination in the sample.

[0004] To achieve the above objectives, an embodiment of the present invention provides a method for detecting metallic impurities in polycrystalline silicon, comprising:

[0005] Step A: Clean each area to ensure that the cleanliness level of each area meets the requirements;

[0006] Step B: Clean several containers, randomly select one or more first containers from the several containers, add a volume-fixing solution to the first container, and test the impurity content of the volume-fixing solution in the first container so that the content of each metal impurity in the volume-fixing solution in the first container meets the requirements.

[0007] Step C: Weigh the polycrystalline silicon sample using the container, and during the weighing process, randomly select one or more second containers from the plurality of containers, and use the second containers to monitor metal impurities in the environment by keeping them open; after the weighing is completed, add a volumetric liquid to the second container, and detect the impurity content of the volumetric liquid in the second container, so that the content of each metal impurity in the volumetric liquid in the second container meets the requirements.

[0008] Step D: Clean the surface of the polycrystalline silicon sample;

[0009] Step E: Dissolve and volatilize the polycrystalline silicon sample. During the dissolution and volatilization process, one or more third containers are randomly selected from the plurality of containers and the third containers are left open to monitor for metal impurities in the environment. After the dissolution and volatilization is completed, a volumetric liquid is added to the third container, and the impurity content of the volumetric liquid in the third container is detected to ensure that the content of each metal impurity in the volumetric liquid in the third container meets the requirements.

[0010] Step F involves adding a volumetric liquid to the container containing the polycrystalline silicon sample, detecting the impurity content of the volumetric liquid in the container, and randomly selecting one or more fourth containers from the plurality of containers during the detection process, using the fourth container to monitor metal impurities in the environment by opening it up; after the detection is completed, adding a volumetric liquid to the fourth container, detecting the impurity content of the volumetric liquid in the fourth container, so that the content of each metal impurity in the volumetric liquid in the fourth container meets the requirements.

[0011] Optionally, step A includes:

[0012] First, wipe and clean each area with water, then wipe and clean each area with isopropyl alcohol, and then wipe and clean each area with water again.

[0013] After standing for 2 to 10 hours, the number of dust particles in each area is detected to determine whether the cleanliness level of each area meets the requirements.

[0014] If so, proceed with the following steps;

[0015] If not, then each area shall be cleaned again until the cleanliness level of each area meets the requirements.

[0016] Optionally, step B includes:

[0017] Clean several containers, and randomly select at least one first container from the several containers at a ratio of more than 5%;

[0018] Add a volumetric liquid to the first container, and use an inductively coupled plasma mass spectrometer to detect the impurity content of the volumetric liquid in the first container, and determine whether the content of each metal impurity in the volumetric liquid in the first container is less than 10 ppt.

[0019] If so, proceed with the following steps;

[0020] If not, start again from step A until the content of each metal impurity in the volumetric liquid in the first container is less than 10 ppt.

[0021] Optionally, step D includes:

[0022] Add the cleaning solution to the container containing the polycrystalline silicon sample and heat at 50–90°C for 40–80 minutes.

[0023] The polycrystalline silicon sample was rinsed with ultrapure water and then dried.

[0024] Optionally, the cleaning solution is prepared by mixing 69% nitric acid, 49% hydrofluoric acid, and water in a volume ratio of 1-3:1-3:8-14.

[0025] Optionally, step E includes:

[0026] The polycrystalline silicon sample is dissolved and volatilized, and during the dissolution and volatilization process, one or more third containers are randomly selected from the plurality of containers at a ratio of more than 5%, and a volume-fixing solution is added to the third container. The third container is then left open to monitor metal impurities in the environment.

[0027] After dissolution and evaporation, inductively coupled plasma mass spectrometry was used to detect the impurity content of the final volume liquid in the third container, and to determine whether each metal impurity in the final volume liquid in the third container was less than 10 ppt.

[0028] If so, proceed with the following steps;

[0029] If not, start again from step A until the content of each metal impurity in the volumetric liquid in the third container is less than 10 ppt.

[0030] Optionally, step F includes:

[0031] A volumetric liquid is added to a container containing the polycrystalline silicon sample. The impurity content of the volumetric liquid in the container is detected by an inductively coupled plasma mass spectrometer. During the detection process, one or more fourth containers are randomly selected from the plurality of containers at a ratio of more than 5%. A volumetric liquid is added to the fourth container, and the metal impurities in the environment are monitored by opening the fourth container.

[0032] After the test, inductively coupled plasma mass spectrometry was used to detect the impurity content of the volumetric liquid in the fourth container, and to determine whether each metal impurity in the volumetric liquid in the fourth container was less than 10 ppt.

[0033] If so, then the process ends;

[0034] If not, start again from step A until the content of each metal impurity in the volumetric liquid in the fourth container is less than 10 ppt.

[0035] Optionally, before step B, the method further includes:

[0036] The content of each metal impurity in the volumetric solution is tested to see if it is less than 10 ppt;

[0037] If so, proceed to step B;

[0038] If not, the volumetric liquid is reconstituted until the content of each metal impurity in the volumetric liquid is less than 10 ppt.

[0039] Optionally, the volumetric liquid is nitric acid with a mass fraction of 5%.

[0040] Optionally, the various areas include a cleaning room, a weighing room, a dissolving room, and a testing room.

[0041] One embodiment of the above invention has the following advantages or beneficial effects: the embodiment of the present invention can add monitoring samples for each operation step while detecting the content of metal impurities in polycrystalline silicon, to monitor the content of various impurities introduced due to external factors, analyze the accuracy of the detection results based on the detection results of the monitoring samples, and when an abnormality occurs, it can promptly point to the specific operation step, and clean the environment and equipment of the specific step in a targeted manner, avoiding the introduction of pollution sources without affecting normal detection, thereby reflecting the impurity content of the sample more accurately.

[0042] The further effects of the aforementioned unconventional alternative methods will be explained below in conjunction with specific implementation methods. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0044] Figure 1 This is a schematic diagram of the main process of a method for detecting metallic impurities in polycrystalline silicon according to an embodiment of the present invention. Detailed Implementation

[0045] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of the present invention, including various details to aid understanding. These details should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0046] To address the technical problems existing in the prior art, this invention provides a method for detecting metal impurities in polycrystalline silicon. The purpose of this method is to monitor the process of detecting metal impurities in polycrystalline silicon, trace the pollution sources introduced during the detection process, clean up the pollution sources in a timely manner, and avoid the introduction of pollution sources, thereby more accurately reflecting the impurity content of the sample.

[0047] Figure 1 This is a schematic diagram of the main flow of a method for detecting metallic impurities in polycrystalline silicon according to an embodiment of the present invention. As one embodiment of the present invention, such as... Figure 1As shown, the method for detecting metallic impurities in polycrystalline silicon may include the following steps:

[0048] Step A: Clean each area to ensure that the cleanliness level of each area meets the requirements;

[0049] Step B: Clean several containers, randomly select one or more first containers from the several containers, add a volumetric liquid to the first container, and test the impurity content of the volumetric liquid in the first container so that the content of each metal impurity in the volumetric liquid in the first container meets the requirements.

[0050] Step C: Weigh the polycrystalline silicon sample using a container. During the weighing process, randomly select one or more second containers from several containers and use the open second containers to monitor metal impurities in the environment. After weighing, add a volumetric liquid to the second container and test the impurity content of the volumetric liquid in the second container to ensure that the content of each metal impurity in the volumetric liquid in the second container meets the requirements.

[0051] Step D: Clean the surface of the polycrystalline silicon sample;

[0052] Step E: Dissolve and volatilize the polycrystalline silicon sample. During the dissolution and volatilization process, one or more third containers are randomly selected from several containers and the third containers are left open to monitor metal impurities in the environment. After the dissolution and volatilization is completed, a volumetric liquid is added to the third container, and the impurity content of the volumetric liquid in the third container is detected to ensure that the content of each metal impurity in the volumetric liquid in the third container meets the requirements.

[0053] Step F: Add a volumetric liquid to the container containing the polycrystalline silicon sample, detect the impurity content of the volumetric liquid in the container, and during the detection process, randomly select one or more fourth containers from several containers and use the fourth container to monitor metal impurities in the environment by opening it up; after the detection is completed, add a volumetric liquid to the fourth container and detect the impurity content of the volumetric liquid in the fourth container to ensure that the content of each metal impurity in the volumetric liquid in the fourth container meets the requirements.

[0054] This invention enables the detection of metal impurities in polycrystalline silicon while simultaneously adding monitoring samples for each operational step. These samples monitor the content of various impurities introduced due to external factors. The accuracy of the detection results is analyzed based on the results from the monitoring samples. When an anomaly is detected, the specific operational step can be identified, allowing for targeted cleaning of the environment and equipment at that step. This avoids the introduction of contamination sources without affecting normal detection, thereby more accurately reflecting the impurity content of the sample.

[0055] Optionally, step A includes: first wiping and cleaning each area with water, then wiping and cleaning each area with isopropyl alcohol, followed by wiping and cleaning each area again with water; after standing for 2-10 hours, detecting the number of dust particles in each area to determine whether the cleanliness level of each area meets the requirements; if yes, proceeding to the next step; if not, cleaning each area again until the cleanliness level of each area meets the requirements. Optionally, each area includes a cleaning room, a weighing room, a dissolving room, and a testing room. The cleanliness level requirement for the cleaning room is less than or equal to level 5 (ISO cleanliness level), the cleanliness level requirement for the weighing room is less than or equal to level 6 (ISO cleanliness level), the cleanliness level requirement for the dissolving room is less than or equal to level 5 (ISO cleanliness level), and the cleanliness level requirement for the testing room is less than or equal to level 5 (ISO cleanliness level). If any one of the cleaning room, weighing room, dissolving room, and testing room does not meet the cleanliness level requirements, the area that does not meet the cleanliness level requirements is re-cleaned until the cleanliness level of that area meets the requirements. Compared to other alcohols, isopropanol is less toxic and less corrosive to certain plastics or coatings.

[0056] Optionally, before step B, the method further includes: detecting whether the content of each metal impurity in the volumetric liquid is less than <10 ppt; if yes, proceed to step B; if no, re-prepare the volumetric liquid until the content of each metal impurity in the volumetric liquid is less than <10 ppt. Inductively coupled plasma mass spectrometry (ICP-MS) can be used to detect whether the content of each metal impurity in the volumetric liquid is less than <10 ppt. If yes, it indicates that the volumetric liquid meets the requirements, and step B continues; if no, it indicates that the volumetric liquid contains impurities and does not meet the requirements, and the volumetric liquid needs to be re-prepared. The re-prepared volumetric liquid is then tested again until the content of each metal impurity in the volumetric liquid is less than <10 ppt. Optionally, the volumetric liquid is 5% nitric acid by mass.

[0057] Optionally, step B includes: cleaning several containers, randomly selecting at least one first container from the several containers at a ratio of 5% or more; adding a volumetric liquid to the first container, and using an inductively coupled plasma mass spectrometer to detect the impurity content of the volumetric liquid in the first container, determining whether the content of each metal impurity in the volumetric liquid in the first container is less than <10ppt; if yes, then proceed to the next step; if no, then start again from step A until the content of each metal impurity in the volumetric liquid in the first container is less than <10ppt. In an embodiment of the present invention, the container can be a sample cup. First, a pickling solution is prepared by mixing 49% hydrofluoric acid, 69% nitric acid, and water in a volume ratio of 1:4:15. The container is placed in the pickling solution and heated to 130°C. After heating for 5 hours, the pickling solution is discarded. The container is then rinsed with water at least three times. The container cap is then tightened, and the outer wall of the container is dried. Next, at least one first container is randomly selected from several containers at a ratio of at least 5%. Approximately 20 ml of a volume-stabilizing solution is added to the first container. The impurity content of the volume-stabilizing solution in the first container is then detected using an inductively coupled plasma mass spectrometer (ICP-MS). It is determined whether the content of each metal impurity in the volume-stabilizing solution in the first container is less than or equal to 10 ppt. If yes, the container meets the requirements, and the subsequent steps are performed. If no, the container does not meet the requirements, and step A is restarted until the content of each metal impurity in the volume-stabilizing solution in the first container is less than or equal to 10 ppt.

[0058] In step C, wipe the inside and outside of the balance and the tabletop, clean the spatula, cut open the sample bag, and assign the same number to all sample bags, both inside and out. Weigh approximately 0.5g of polycrystalline silicon sample into a container, tighten the container lid, seal the weighed sample, and place it into a sample bag.

[0059] Optionally, step D includes: adding the cleaning solution to a container holding the polycrystalline silicon sample, heating at 50–90°C for 40–80 minutes; rinsing the polycrystalline silicon sample with ultrapure water and draining off the water. Optionally, the cleaning solution is prepared by mixing 69% nitric acid, 49% hydrofluoric acid, and water in a volume ratio of 1–3:1–3:8–14. For example, the container holding the polycrystalline silicon sample is filled with the cleaning solution, then placed on a heating plate for heating. After heating, the polycrystalline silicon sample is rinsed three times with 18 megohm ultrapure water and drained off the water.

[0060] Optionally, step E includes: dissolving and volatilizing the polycrystalline silicon sample, and during the dissolution and volatilization process, randomly selecting one or more third containers from several containers at a ratio of more than 5%, adding a volumetric liquid to the third container, and monitoring metal impurities in the environment using an open third container; after the dissolution and volatilization is completed, using an inductively coupled plasma mass spectrometer to detect the impurity content of the volumetric liquid in the third container, and determining whether each metal impurity in the volumetric liquid in the third container is less than <10 ppt; if yes, then proceed to step F; if not, then restart from step A until the content of each metal impurity in the volumetric liquid in the third container is less than <10 ppt. In step E, the dropper is cleaned, and a dissolving acid (69% HNO3: 49% HF = 1:1 by mass) is prepared and the polycrystalline silicon sample is dissolved and volatilized on a fume hood workbench. Specifically, 12 mL of dissolving acid was added to the polycrystalline silicon sample. When the sample was evaporated to 1 drop, 2 mL of dissolving acid was added. When the sample was evaporated to 1 drop again, 2 mL of dissolving acid was added. When only the size of a mung bean remained in the container, the bottle was removed and the dissolving acid in the container was evaporated to dryness using the residual heat.

[0061] Optionally, step F includes: adding a volumetric liquid to a container containing a polycrystalline silicon sample; detecting the impurity content of the volumetric liquid in the container using an inductively coupled plasma mass spectrometer (ICP-MS); and during the detection process, randomly selecting one or more fourth containers from a pool of containers at a ratio of 5% or higher, adding a volumetric liquid to the fourth container, and monitoring for metal impurities in the environment using the open fourth container; after the detection is completed, detecting the impurity content of the volumetric liquid in the fourth container using an ICP-MS to determine whether each metal impurity in the volumetric liquid in the fourth container is less than or equal to 10 ppt; if yes, the process ends; if not, the process restarts from step A until the content of each metal impurity in the volumetric liquid in the fourth container is less than or equal to 10 ppt. In step F, approximately 20 mL of volumetric liquid is added to each container containing a polycrystalline silicon sample, and the container cap is tightened. The ICP-MS is tuned and calibrated as required, and the processed samples are detected. The injection needle is rinsed in 5% HNO3 solution between each sample. One or more fourth containers are randomly selected from several containers at a rate of 5% or more. Approximately 20 ml of diluent is added to the fourth container. During the testing process, the fourth container is placed open next to the instrument. After the polycrystalline silicon sample testing is completed, the impurity content of the diluent in the fourth container is detected using inductively coupled plasma mass spectrometry (ICP-MS) to determine whether each metal impurity in the diluent is less than or equal to 10 ppt. If so, the test results for the polycrystalline silicon sample are valid. If not, the process restarts from step A until the content of each metal impurity in the diluent in the fourth container is less than or equal to 10 ppt.

[0062] This invention provides comprehensive monitoring of the detection process for metallic impurities in polycrystalline silicon. During detection, it promptly identifies specific operational steps when abnormal data is encountered, allowing for targeted cleaning of the environment and equipment at those steps. This avoids introducing contaminants without affecting normal detection, thus providing a more accurate reflection of the sample's impurity content. This invention is applicable to industries such as photovoltaics, semiconductors, integrated circuits, and chips that have strict requirements regarding silicon metal impurities.

[0063] To help understand the solution of the present invention, several specific embodiments are given below for detailed description.

[0064] Example 1

[0065] Step 1): First, wipe and clean each area with water, then wipe and clean each area with isopropyl alcohol, and then wipe and clean each area with water again. After standing for 6 hours, test the dust particles in each area to determine whether the cleanliness level of each area meets the requirements. If yes, proceed to step 2); if no, repeat step 1) until the cleanliness level of each area meets the requirements.

[0066] The areas include a cleaning room, a weighing room, a dissolving room, and a testing room. The cleanliness level requirement for the cleaning room is ≤5 (ISO cleanliness level), for the weighing room it is ≤6 (ISO cleanliness level), for the dissolving room it is ≤5 (ISO cleanliness level), and for the testing room it is ≤5 (ISO cleanliness level). If any of these areas fails to meet the cleanliness level requirements, the area must be re-cleaned until the required cleanliness level is met.

[0067] Step 2): Use inductively coupled plasma mass spectrometry (ICP-MS) to check whether the content of each metal impurity in the volumetric liquid is less than 10 ppt; if yes, proceed to step 3); if no, prepare the volumetric liquid again until the content of each metal impurity in the volumetric liquid is less than 10 ppt. The volumetric liquid is 5% nitric acid by mass.

[0068] Step 3): Clean several containers, and randomly select at least one first container from the containers at a ratio of more than 5%; add about 20 ml of dilution solution to the first container, and use inductively coupled plasma mass spectrometry to detect the impurity content of the dilution solution in the first container, and determine whether the content of each metal impurity in the dilution solution in the first container is less than <10 ppt; if yes, proceed to step 4); if no, start from step 1) again until the content of each metal impurity in the dilution solution in the first container is less than <10 ppt.

[0069] Step 4): Weigh the polycrystalline silicon sample using a container. Specifically, wipe the inside and outside of the balance and the tabletop, clean the spatula, cut open the sample bag, and assign the same number to all sample bags, both inside and out. Weigh approximately 0.5g of polycrystalline silicon sample into the container, tighten the lid, seal the weighed sample, and place it into a sample bag. During the weighing process, randomly select one or more second containers from several containers at a ratio of 5% or more, and use the open second containers to monitor for metal impurities in the environment. After weighing, add approximately 20ml of a dilution solution to the second container and use an inductively coupled plasma mass spectrometer to detect the impurity content in the dilution solution. Determine whether the content of each metal impurity in the dilution solution is less than or equal to 10ppt. If yes, proceed to step 5); if not, start again from step 1) until the content of each metal impurity in the dilution solution in the second container is less than or equal to 10ppt.

[0070] Step 5): Add the cleaning solution to the container holding the polycrystalline silicon sample and heat at 70°C for 60 minutes; rinse the polycrystalline silicon sample with ultrapure water and drain. The cleaning solution is prepared by mixing 69% nitric acid, 49% hydrofluoric acid, and water in a volume ratio of 1:1:14.

[0071] Step 6): Clean the dropper and prepare the dissolving acid (69% HNO3: 49% HF = 1:1). Dissolve the volatile polycrystalline silicon sample in the fume hood. Specifically, add 12 mL of dissolving acid to the polycrystalline silicon sample. When only 1 drop remains after evaporation, add 2 mL of dissolving acid. Evaporate again until only 1 drop remains, then add another 2 mL of dissolving acid. When only the size of a mung bean remains in the container, remove the bottle and use the residual heat to evaporate the remaining dissolving acid.

[0072] During the dissolution and evaporation of the polycrystalline silicon sample, one or more third containers are randomly selected from several containers at a ratio of more than 5%. Approximately 20 ml of diluent is added to the third container. The entire operation is conducted in an open fume hood under monitoring. After dissolution and evaporation, the impurity content of the diluent in the third container is detected using inductively coupled plasma mass spectrometry (ICP-MS) to determine whether the content of each metal impurity in the diluent in the third container is less than or equal to 10 ppt. If yes, the operation meets the requirements, and step 7) is executed. If no, the operation does not meet the requirements, and step 1) is restarted until the content of each metal impurity in the diluent in the third container is less than or equal to 10 ppt.

[0073] Step 7): Add approximately 20 mL of volume-stabilizing solution to each container containing a polycrystalline silicon sample and tighten the container cap. Tune the inductively coupled plasma mass spectrometer (ICP-MS) as required and mark the lines. Analyze the processed samples, rinsing the injection needle in a 5% (w / w) HNO3 solution between each sample. During the analysis, randomly select one or more fourth containers from a pool of containers at a ratio of 5% or higher, and add approximately 20 mL of volume-stabilizing solution to each fourth container. Keep the fourth container open next to the instrument during the analysis. After the polycrystalline silicon sample analysis is completed, use the ICP-MS to analyze the impurity content of the volume-stabilizing solution in the fourth container, determining whether each metal impurity in the volume-stabilizing solution is less than or equal to 10 ppt. If yes, the polycrystalline silicon sample analysis result is valid; if not, start again from step 1) until the content of each metal impurity in the volume-stabilizing solution in the fourth container is less than or equal to 10 ppt.

[0074] Example 2

[0075] The difference between this method and the detection method in Example 1 is that in step 1), each area is first wiped clean with water, then each area is wiped clean with isopropyl alcohol, and then each area is wiped clean with water again; after standing for 8 hours, the dust particles in each area are detected to determine whether the cleanliness level of each area meets the requirements.

[0076] Example 3

[0077] The difference between this method and the detection method in Example 1 is that in step 1), each area is first wiped clean with water, then each area is wiped clean with isopropyl alcohol, and then each area is wiped clean with water again; after standing for 5 hours, the dust particles in each area are detected to determine whether the cleanliness level of each area meets the requirements.

[0078] Example 4

[0079] The difference between this method and the detection method in Example 1 is that in step 1), each area is first wiped clean with water, then each area is wiped clean with isopropyl alcohol, and then each area is wiped clean with water again; after standing for 9 hours, the dust particles in each area are detected to determine whether the cleanliness level of each area meets the requirements.

[0080] Example 5

[0081] The difference between this method and the detection method in Example 1 is that in step 3), at least one first container is randomly selected from several containers at a ratio of 8% or more.

[0082] Example 6

[0083] The difference between this method and the detection method in Example 1 is that in step 3), at least one first container is randomly selected from several containers at a ratio of more than 10%.

[0084] Example 7

[0085] The difference between this method and the detection method in Example 1 is that in step 4), one or more second containers are randomly selected from several containers at a ratio of 7% or more.

[0086] Example 8

[0087] The difference between this method and the detection method in Example 1 is that in step 4), one or more second containers are randomly selected from several containers at a ratio of more than 9%.

[0088] Example 9

[0089] The difference between this method and the detection method in Example 1 is that in step 5), the cleaning solution is added to the container containing the polycrystalline silicon sample and heated at 60°C for 65 minutes; the polycrystalline silicon sample is rinsed with ultrapure water and the water is drained. The cleaning solution is prepared by mixing 69% nitric acid, 49% hydrofluoric acid, and water in a volume ratio of 2:2:10.

[0090] Example 10

[0091] The difference between this method and the detection method in Example 1 is that in step 5), the cleaning solution is added to the container containing the polycrystalline silicon sample and heated at 75°C for 50 minutes; the polycrystalline silicon sample is then rinsed with ultrapure water and the water is drained. The cleaning solution is prepared by mixing 69% nitric acid, 49% hydrofluoric acid, and water in a volume ratio of 1:3:9.

[0092] Example 11

[0093] The difference between this method and the detection method in Example 1 is that in step 5), the cleaning solution is added to the container holding the polycrystalline silicon sample and heated at 80°C for 45 minutes; the polycrystalline silicon sample is rinsed with ultrapure water and the water is drained. The cleaning solution is prepared by mixing 69% nitric acid, 49% hydrofluoric acid, and water in a volume ratio of 3:1.5:12.

[0094] Example 12

[0095] The difference between this method and the detection method in Example 1 is that in step 6), one or more third containers are randomly selected from several containers at a ratio of 7.5% or higher.

[0096] Example 13

[0097] The difference between this method and the detection method in Example 1 is that in step 6), one or more third containers are randomly selected from several containers at a ratio of 5.5% or higher.

[0098] Example 14

[0099] The difference between this method and the detection method in Example 1 is that in step 6), one or more third containers are randomly selected from several containers at a ratio of 8.2% or higher.

[0100] Example 15

[0101] The difference between this method and the detection method in Example 1 is that in step 7), one or more fourth containers are randomly selected from several containers at a ratio of 6.3% or higher.

[0102] Example 16

[0103] The difference between this method and the detection method in Example 1 is that in step 7), one or more fourth containers are randomly selected from several containers at a ratio of 7.2% or higher.

[0104] Example 17

[0105] The difference between this method and the detection method in Example 1 is that in step 7), one or more fourth containers are randomly selected from several containers at a ratio of 8.6% or higher.

[0106] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for detecting metallic impurities in polycrystalline silicon, characterized in that, Includes the following steps: Step A: Clean each area to ensure that the cleanliness level of each area meets the requirements; Step B: Clean several containers, randomly select one or more first containers from the several containers, add a volume-fixing solution to the first container, and test the impurity content of the volume-fixing solution in the first container so that the content of each metal impurity in the volume-fixing solution in the first container meets the requirements. Step C: Weigh the polycrystalline silicon sample using the container, and during the weighing process, randomly select one or more second containers from the plurality of containers, and use the second containers to monitor metal impurities in the environment by keeping them open; after the weighing is completed, add a volumetric liquid to the second container, and detect the impurity content of the volumetric liquid in the second container, so that the content of each metal impurity in the volumetric liquid in the second container meets the requirements. Step D: Clean the surface of the polycrystalline silicon sample; Step E: Dissolve and volatilize the polycrystalline silicon sample. During the dissolution and volatilization process, one or more third containers are randomly selected from the plurality of containers and the third containers are left open to monitor for metal impurities in the environment. After the dissolution and volatilization is completed, a volumetric liquid is added to the third container, and the impurity content of the volumetric liquid in the third container is detected to ensure that the content of each metal impurity in the volumetric liquid in the third container meets the requirements. Step F involves adding a volumetric liquid to the container containing the polycrystalline silicon sample, detecting the impurity content of the volumetric liquid in the container, and randomly selecting one or more fourth containers from the plurality of containers during the detection process, using the fourth container to monitor metal impurities in the environment by opening it up; after the detection is completed, adding a volumetric liquid to the fourth container, detecting the impurity content of the volumetric liquid in the fourth container, so that the content of each metal impurity in the volumetric liquid in the fourth container meets the requirements.

2. The method according to claim 1, characterized in that, Step A includes: First, wipe and clean each area with water, then wipe and clean each area with isopropyl alcohol, and then wipe and clean each area with water again. After standing for 2 to 10 hours, the number of dust particles in each area is detected to determine whether the cleanliness level of each area meets the requirements. If so, proceed with the following steps; If not, then each area shall be cleaned again until the cleanliness level of each area meets the requirements.

3. The method according to claim 1, characterized in that, Step B includes: Clean several containers, and randomly select at least one first container from the several containers at a ratio of more than 5%; Add a volumetric liquid to the first container, and use an inductively coupled plasma mass spectrometer to detect the impurity content of the volumetric liquid in the first container, and determine whether the content of each metal impurity in the volumetric liquid in the first container is less than 10 ppt. If so, proceed with the following steps; If not, start again from step A until the content of each metal impurity in the volumetric liquid in the first container is less than 10 ppt.

4. The method according to claim 1, characterized in that, Step D includes: Add the cleaning solution to the container containing the polycrystalline silicon sample and heat at 50–90°C for 40–80 minutes. The polycrystalline silicon sample was rinsed with ultrapure water and then dried.

5. The method according to claim 4, characterized in that, The cleaning solution is prepared by mixing 69% nitric acid, 49% hydrofluoric acid and water in a volume ratio of 1-3:1-3:8-14.

6. The method according to claim 1, characterized in that, Step E includes: The polycrystalline silicon sample is dissolved and volatilized, and during the dissolution and volatilization process, one or more third containers are randomly selected from the plurality of containers at a ratio of more than 5%, and a volume-fixing solution is added to the third container. The third container is then left open to monitor metal impurities in the environment. After dissolution and evaporation, inductively coupled plasma mass spectrometry was used to detect the impurity content of the final volume liquid in the third container, and to determine whether each metal impurity in the final volume liquid in the third container was less than 10 ppt. If so, proceed with the following steps; If not, start again from step A until the content of each metal impurity in the volumetric liquid in the third container is less than 10 ppt.

7. The method according to claim 1, characterized in that, Step F includes: A volumetric liquid is added to a container containing the polycrystalline silicon sample. The impurity content of the volumetric liquid in the container is detected by an inductively coupled plasma mass spectrometer. During the detection process, one or more fourth containers are randomly selected from the plurality of containers at a ratio of more than 5%. A volumetric liquid is added to the fourth container, and the metal impurities in the environment are monitored by opening the fourth container. After the test, inductively coupled plasma mass spectrometry was used to detect the impurity content of the volumetric liquid in the fourth container, and to determine whether each metal impurity in the volumetric liquid in the fourth container was less than 10 ppt. If so, then the process ends; If not, start again from step A until the content of each metal impurity in the volumetric liquid in the fourth container is less than 10 ppt.

8. The method according to claim 1, characterized in that, Before step B, the following is also included: The content of each metal impurity in the volumetric solution is tested to see if it is less than 10 ppt; If so, proceed to step B; If not, the volumetric liquid is reconstituted until the content of each metal impurity in the volumetric liquid is less than 10 ppt.

9. The method according to claim 1, characterized in that, The volumetric liquid is nitric acid with a mass fraction of 5%.

10. The method according to claim 1, characterized in that, The various areas include a cleaning room, a weighing room, a dissolving room, and a testing room.

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