Method for reducing the content of silicon in a silane gas impurity absorbing liquid

Abstract

The application discloses a method for reducing the content of silicon element in a silane gas impurity element absorption liquid in the technical field of silicon polycrystal and silane gas preparation, and comprises the following steps: adding a digestion liquid and mannitol into the silane gas impurity element absorption liquid which has absorbed silane gas; wherein the digestion liquid is prepared by mixing nitric acid and hydrofluoric acid. By adding the mixed acid of hydrofluoric acid and nitric acid into the silane gas absorption liquid, silicon or silicon compounds which are not easy to volatilize in the solution are converted into the form of silicon tetrafluoride and volatilize, and at the same time, the mannitol is added to make the boron element compounds in the form of compounds in the solution react to generate a complex, so that volatilization loss in the heating reaction process is avoided, the content of silicon element in the silane gas impurity element absorption liquid which has absorbed silane gas can be effectively reduced, signal rapid attenuation in the detection process of an inductively coupled plasma mass spectrometer is avoided, and at the same time, the content of silicon element in the absorption liquid is reduced, so that the accuracy of phosphorus element detection can be effectively improved.

Description

Technical Field

[0001] This invention relates to the fields of polycrystalline silicon and silane gas preparation technology, and specifically to a method for reducing the silicon content in a silane gas impurity element absorption liquid. Background Technology

[0002] Silane gas, as a specialty electronic gas, is a core raw material for high-tech industries such as semiconductors, photovoltaics, and display panels. It can also be used as a raw material to produce granular silicon or rod-shaped polycrystalline silicon. Therefore, accurately quantifying the impurity content in silane gas can not only effectively ensure the quality of granular silicon, but also provide downstream users of silane gas with accurate data on the content of impurity elements.

[0003] In actual production, silane gas is analyzed according to GB / T 15909-2017 "Silane Gases for Electronic Industry" to detect that the molar fractions of B and P in silane gas are less than 0.2E-9 (scientific counting method). However, when measuring the resistivity of granular silicon produced by fluidized bed method using zone melting method, it can be seen that the analysis of B and P impurity content is inaccurate and there are differences. Therefore, for special gases used in the electronics industry, some companies additionally require the epitaxial wafer resistivity, which will inevitably lead to an increase in product cost.

[0004] After silane gas is absorbed according to GB / T 15909-2017 "Silanes for Electronic Industry", the silicon element in the absorption liquid mainly exists in the form of silicic acid, metasilicic acid or silicate ions. These silicon compounds are difficult to completely volatilize during the subsequent evaporation process, resulting in a high silicon content in the absorption liquid. During the detection process of inductively coupled plasma mass spectrometry, the signal attenuates rapidly, making it impossible to complete the detection of trace impurities in the sample. At the same time, silicon and phosphorus have similar mass numbers, and a high silicon content will affect the accuracy of phosphorus detection. Therefore, eliminating silicon in the silane gas absorption liquid is the difficulty of this detection method. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies, such as the rapid attenuation of instrument signal values ​​due to high silicon content in silane gas absorption liquid, which leads to the inability to complete sample detection, and the fact that silicon and phosphorus have similar mass numbers, with higher silicon content affecting the accuracy of phosphorus detection. This invention provides a method for reducing the silicon content in silane gas impurity element absorption liquid, which can reduce the silicon content in silane gas impurity element absorption liquid and improve the accuracy of phosphorus detection.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0007] This invention provides a method for reducing the silicon content in a silane gas impurity element absorption liquid, characterized by comprising:

[0008] Add digestion solution to the impurity element absorption solution that has absorbed silane gas, mix thoroughly after adding digestion solution, and then add D-mannitol aqueous solution; heat to dryness; dissolve the residue with nitric acid solution and make up to volume, and determine the content of impurity elements in the solution.

[0009] The digestion solution is a mixture of nitric acid and hydrofluoric acid, wherein the mass concentration of hydrofluoric acid is 19.0 wt%-28.5 wt% and the mass concentration of nitric acid is 13.7 wt%-27.5 wt%; the volume ratio of the silane gas impurity element absorption liquid to the digestion solution is 5:1-5:2; the added digestion solution converts silicon or non-volatile silicon compounds in the solution into volatile silicon compounds, such as volatile silicon tetrafluoride.

[0010] After adding the digestion solution, D-mannitol is added to react with the boron compounds in the solution to form a complex. The stable complex formed by the boron compounds and D-mannitol ensures that when volatile silicon compounds (such as volatile silicon tetrafluoride) are volatilized, boron impurities are retained in the solution to be analyzed, thus ensuring the accuracy of boron impurity detection and analysis.

[0011] The D-mannitol has a mass concentration ≥99.0%, the D-mannitol concentration in the aqueous solution is 0.8 wt%-1.2 wt%, and the volume ratio of D-mannitol to the silane gas impurity element absorption liquid with reduced silicon content is 100:1-25:1.

[0012] When evaporating silicon compounds that have been converted into volatile silicon compounds in the solution, such as silicon tetrafluoride, the evaporation temperature range is 100-160℃. This ensures that the stable complex formed by the boron compound and D-mannitol will not be volatilized from the solution, and also ensures that the stable complex formed by the boron compound and D-mannitol will not decompose into boron compound and D-mannitol, causing the boron compound to volatilize simultaneously. This ensures the accuracy of boron impurity detection and analysis.

[0013] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0014] The present invention provides a method for reducing the silicon content in a silane gas impurity element absorption liquid. This method involves adding a digestion solution to the silane gas absorption liquid, causing the silicon in the solution, particularly silicon in solution or non-volatile silicon compounds such as silicic acid, metasilicic acid, silicates, and silicon dioxide, to volatilize in the form of more volatile silicon compounds, specifically silicon tetrafluoride. This solves the problem of rapid signal attenuation during inductively coupled plasma mass spectrometry (ICP-MS) detection, thus improving the accuracy of trace element detection. Specifically, the digestion solution is a mixture of hydrofluoric acid and nitric acid, which volatilizes the silicon in the solution as silicon tetrafluoride. Simultaneously, mannitol is added to react with boron in the solution to form a complex, avoiding boron loss during the heating reaction and ensuring the accuracy of boron analysis. Furthermore, by effectively reducing the silicon content in the silane gas impurity element absorption liquid that has absorbed silane gas, the accuracy of detecting phosphorus (P) and other elements is improved. Detailed Implementation

[0015] The present invention will now be further described. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0016] The materials used in the embodiments of the present invention, wherein:

[0017] Hydrofluoric acid: purchased from Tama Chemical Industry Co., Ltd., TAMAPURE AA-10 grade, mass concentration 38%;

[0018] Nitric acid: purchased from Tama Chemical Industry Co., Ltd., TAMAPURE AA-10 grade, 55% by mass;

[0019] D-Mannitol: Purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with ultrapure grade purity and a mass concentration ≥99.0% (HPLC).

[0020] Water: resistivity greater than 18.2 MΩ·cm, and the content of each metal impurity is less than 20 ng / L.

[0021] In this embodiment of the invention, the absorption operation of the silane gas impurity element absorption liquid is carried out in accordance with GB / T 15909-2017 "Silane Gases for Electronic Industry".

[0022] Example 1

[0023] This embodiment provides a method for reducing the silicon content in a silane gas impurity element absorption liquid, comprising: accurately transferring 10 ml of the silane gas impurity element absorption liquid that has absorbed silane gas into a clean PFA beaker, and adding 3 ml of digestion solution, wherein the digestion solution is composed of 1 ml of HNO3 and 2 ml of HF.

[0024] The absorbent solutions before and after reducing the silicon content were tested separately. For the silane gas impurity element absorbent solution after reducing the silicon content, the entire solution was used; for the silane gas impurity element absorbent solution after reducing the silicon content, an equal volume was used. The testing steps included:

[0025] Step 1: Add 0.2 ml of 1% mannitol to the silane gas impurity element absorption solution after reducing the silicon content;

[0026] Step 2: Place the beaker containing the sample on a heating plate set at 140°C, evaporate to dryness, and then dilute to 5 ml with 1% nitric acid.

[0027] Step 3: Perform detection on an inductively coupled plasma mass spectrometer.

[0028] The test results are shown in Table 1.

[0029] Table 1

[0030]

[0031] As shown in Table 1, the method provided by the present invention can effectively reduce the silicon content in the silane gas impurity element absorption liquid that has absorbed silane gas, thereby improving the accuracy of phosphorus detection.

[0032] Example 2

[0033] This embodiment provides a method for reducing the silicon content in a silane gas impurity element absorption liquid, comprising: accurately transferring 10 ml of the silane gas impurity element absorption liquid that has absorbed silane gas into a clean PFA beaker, and adding 2 ml of digestion solution, wherein the digestion solution is composed of 1 ml of HNO3 and 1 ml of HF.

[0034] The absorbent solutions before and after reducing the silicon content were tested separately. For the silane gas impurity element absorbent solution after reducing the silicon content, the entire solution was used; for the silane gas impurity element absorbent solution after reducing the silicon content, an equal volume was used. The testing steps included:

[0035] Step 1: Add 0.1 ml of 1% mannitol to the silane gas impurity element absorption solution after reducing the silicon content;

[0036] Step 2: Place the beaker containing the sample on a heating plate set to 100°C, evaporate to dryness, and then dilute to 5 ml with 1% nitric acid.

[0037] Step 3: Perform detection on an inductively coupled plasma mass spectrometer.

[0038] The test results are shown in Table 1.

[0039] Table 2

[0040]

[0041] As shown in Table 2, the method provided by the present invention can effectively reduce the silicon content in the silane gas impurity element absorption liquid that has absorbed silane gas, thereby improving the accuracy of phosphorus detection, while not affecting the accuracy of boron detection.

[0042] Example 3

[0043] This embodiment provides a method for reducing the silicon content in a silane gas impurity element absorption liquid, comprising: accurately transferring 10 ml of the silane gas impurity element absorption liquid that has absorbed silane gas into a clean PFA beaker, and adding 4 ml of digestion solution, wherein the digestion solution is composed of 1 ml of HNO3 and 3 ml of HF.

[0044] The absorbent solutions before and after reducing the silicon content were tested separately. For the silane gas impurity element absorbent solution after reducing the silicon content, the entire solution was used; for the silane gas impurity element absorbent solution after reducing the silicon content, an equal volume was used. The testing steps included:

[0045] Step 1: Add 0.4 ml of 1% mannitol to the silane gas impurity element absorption solution after reducing the silicon content;

[0046] Step 2: Place the beaker containing the sample on a heating plate set at 160°C, evaporate to dryness, and then dilute to 5 ml with 3% nitric acid.

[0047] Step 3: Perform detection on an inductively coupled plasma mass spectrometer.

[0048] The test results are shown in Table 1.

[0049] Table 3

[0050]

[0051] As shown in Table 3, the method provided by the present invention can effectively reduce the silicon content in the silane gas impurity element absorption liquid that has absorbed silane gas, thereby improving the accuracy of phosphorus and other metal element detection.

[0052] The above embodiments have provided a detailed description of the present invention. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other modifications under the guidance of the present invention without departing from the spirit and scope of the claims. All of these modifications are within the protection scope of the present invention.

Claims

1. A method for reducing the content of silicon in a silane gas impurity element absorption solution, characterized by, include: Add digestion solution to the impurity element absorption solution that has absorbed silane gas, mix well after adding digestion solution, and then add D-mannitol aqueous solution. Heat and evaporate to dryness; The residue was dissolved using nitric acid solution, and the content of impurity elements in the solution was determined.

2. The method for reducing the silicon content in the silane gas impurity element absorption liquid according to claim 1, characterized in that: The digestion solution is a mixture of nitric acid and hydrofluoric acid, wherein the mass concentration of hydrofluoric acid is 19.0 wt%-28.5 wt% and the mass concentration of nitric acid is 13.7 wt%-27.5 wt%.

3. The method for reducing the silicon content in the silane gas impurity element absorption liquid according to claim 1, characterized in that: The volume ratio of the silane gas impurity element absorption liquid to the digestion liquid is 5:1-5:

2.

4. The method for reducing the silicon content in the silane gas impurity element absorption liquid according to claim 1, characterized in that: Add digestion solution to convert the silicon in the solution into silicon compounds.

5. The method for reducing the silicon content in the silane gas impurity element absorption liquid according to claim 4, characterized in that: D-Mannitol was added after the digestion solution was added, so that it reacted with the boron compounds in the solution to form a complex.

6. The method for reducing the silicon content in the silane gas impurity element absorption liquid according to claim 5, characterized in that: The volume ratio of D-mannitol to the silane gas impurity element absorption liquid with reduced silicon content is 100:1-25:

1.

7. The method for reducing the silicon content in the silane gas impurity element absorption liquid according to claim 6, characterized in that: The concentration of D-mannitol in the aqueous solution is 0.8 wt%-1.2 wt%.

8. The method for reducing the silicon content in the silane gas impurity element absorption liquid according to claim 7, characterized in that: The mass concentration of D-mannitol is ≥99.0%.

9. The method for reducing the silicon content in the silane gas impurity element absorption liquid according to claim 1, characterized in that: The temperature range for evaporation is 100-160℃.

10. The method for reducing the silicon content in the silane gas impurity element absorption liquid according to claim 1, characterized in that: The concentration of the nitric acid solution is 0.5 vol% - 3 vol.

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