CN113899600A - Preparation method and detection method of polycrystalline silicon surface metal detection sample - Google Patents
Preparation method and detection method of polycrystalline silicon surface metal detection sample Download PDFInfo
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- 229910021420 polycrystalline silicon Inorganic materials 0.000 title claims abstract description 131
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 102
- 239000002184 metal Substances 0.000 title claims abstract description 101
- 238000001514 detection method Methods 0.000 title claims abstract description 85
- 238000002360 preparation method Methods 0.000 title claims abstract description 34
- 239000002253 acid Substances 0.000 claims abstract description 62
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 62
- 229910001868 water Inorganic materials 0.000 claims abstract description 54
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 50
- 238000005406 washing Methods 0.000 claims abstract description 41
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 40
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 40
- 238000002386 leaching Methods 0.000 claims abstract description 34
- 238000005554 pickling Methods 0.000 claims abstract description 29
- 239000007788 liquid Substances 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 16
- 238000001704 evaporation Methods 0.000 claims abstract description 15
- 230000008020 evaporation Effects 0.000 claims abstract description 14
- 238000005464 sample preparation method Methods 0.000 claims abstract description 5
- 238000005303 weighing Methods 0.000 claims abstract description 5
- 239000012535 impurity Substances 0.000 claims description 42
- 238000000034 method Methods 0.000 claims description 39
- 229920005591 polysilicon Polymers 0.000 claims description 30
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- 238000009616 inductively coupled plasma Methods 0.000 claims description 8
- 230000003749 cleanliness Effects 0.000 claims description 7
- 238000005070 sampling Methods 0.000 claims description 4
- 239000000243 solution Substances 0.000 description 76
- 238000005507 spraying Methods 0.000 description 12
- 229910052742 iron Inorganic materials 0.000 description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 7
- 229910052782 aluminium Inorganic materials 0.000 description 7
- 229910052791 calcium Inorganic materials 0.000 description 7
- 229910052710 silicon Inorganic materials 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 description 4
- 229910021642 ultra pure water Inorganic materials 0.000 description 4
- 239000012498 ultrapure water Substances 0.000 description 4
- 239000003517 fume Substances 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 239000011259 mixed solution Substances 0.000 description 3
- -1 polytetrafluoroethylene Polymers 0.000 description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 description 3
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
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- 238000010248 power generation Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 1
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
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- 239000011863 silicon-based powder Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 235000012431 wafers Nutrition 0.000 description 1
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
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Abstract
The invention discloses a preparation method of a polycrystalline silicon surface metal detection sample, which comprises the following steps: weighing polycrystalline silicon; rapidly leaching the surface of the polycrystalline silicon by using a mixed acid solution of nitric acid and hydrofluoric acid to obtain a pickling solution; then, carrying out water leaching on the pickled polycrystalline silicon to obtain water washing liquid; heating the pickling solution and the water washing solution together until the pickling solution and the water washing solution are evaporated to dryness; and adding nitric acid into the residue after evaporation to dryness for dissolving, and then performing constant volume on the dissolved solution obtained by dissolving to obtain a sample for detecting the metal on the surface of the polycrystalline silicon. The invention also discloses a polycrystalline silicon surface metal detection method comprising the sample preparation method. The invention can greatly shorten the preparation time and the detection period of the detection sample and improve the detection accuracy.
Description
Technical Field
The invention belongs to the technical field of polycrystalline silicon, and particularly relates to a preparation method of a polycrystalline silicon surface metal detection sample and a polycrystalline silicon surface metal detection method.
Background
Polycrystalline silicon is a main raw material for manufacturing high-purity silicon products such as silicon polished wafers, solar cells, electronic chips and the like, and has very high purity requirement, and particularly for electronic-grade polycrystalline silicon, the purity requirement is over 99.9999%. Impurities in polycrystalline silicon are classified into surface metal impurities and matrix metal impurities according to the source and distribution. The matrix metal impurities are derived from materials such as raw material silicon powder for producing the polycrystalline silicon product, and can be basically removed through rectification, and the B, P content can be reduced to the order of magnitude of ppta. The surface metal impurities come from the external environment, for example, in the links of storage, crushing, packaging and the like of polycrystalline silicon products, metal, nonmetal, indoor dust are in contact with the polycrystalline silicon products, and metal elements such as Fe, Cr, Ni, Cu, Zn and the like are deposited on the surfaces of the polycrystalline silicon materials.
If the polycrystalline silicon with the surface containing the metal impurities is used for drawing monocrystalline silicon and manufacturing cell pieces, the crystal formation of the monocrystalline drawing and the minority carrier lifetime after ingot casting are directly influenced, and further the conversion efficiency of the manufactured cell pieces is influenced, so that the attenuation of a cell assembly in the power generation process is serious, and the power generation quantity is influenced. Therefore, the surface metal impurity content of polysilicon needs to be strictly controlled.
At present, the detection process of metal impurities on the surface of polycrystalline silicon comprises the following steps: the method comprises the steps of putting a polycrystalline silicon sample into a mixed solution of nitric acid, hydrofluoric acid, hydrogen peroxide and water, leaching for a period of time (about 1h) at a certain temperature to deposit impurities on the surface of the polycrystalline silicon into a leaching solution, evaporating to dryness (about 2h), and measuring the content of metal impurities in the polycrystalline silicon sample by using an inductively coupled plasma mass spectrometer after constant volume. In the process of preparing the detection sample, because a leaching mode is adopted, the detection sample needs a longer time to be prepared, and the leaching solution is exposed in the environment for a long time, so that impurities such as K, Ca, Al, Fe and the like in the environment can be precipitated into the leaching solution, and the problems that the detection result cannot accurately reflect the content of surface metal impurities of a polycrystalline silicon product, the detection period is long and the like are caused; in addition, because the mixed solution has low acidity (the volume ratio of nitric acid to hydrofluoric acid to hydrogen peroxide to water is 1:1:1:50), the metal impurities on the surface of the polycrystalline silicon can react with the mixed solution and are deposited in the leaching solution only by adopting a leaching mode and even heating during leaching, and the operation difficulty is increased.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art, and provides a preparation method and a detection method of a polycrystalline silicon surface metal detection sample, which can greatly shorten the preparation time and the detection period of the detection sample and improve the detection accuracy.
According to one aspect of the invention, a preparation method of a polycrystalline silicon surface metal detection sample is provided, and the technical scheme is as follows:
a preparation method of a polycrystalline silicon surface metal detection sample comprises the following steps:
s101, sampling: weighing polycrystalline silicon;
s102 acid washing: rapidly leaching the surface of the polycrystalline silicon by using a mixed acid solution of nitric acid and hydrofluoric acid to obtain a pickling solution;
s103, water washing: then, carrying out water leaching on the pickled polycrystalline silicon to obtain water washing liquid;
s104, evaporation: heating the pickling solution and the water washing solution together until the pickling solution and the water washing solution are evaporated to dryness;
s105, constant volume: and adding a nitric acid solution into the residue after evaporation to dryness for dissolving, and then performing constant volume on the solution obtained by dissolving to obtain the polysilicon surface metal detection sample.
Preferably, the use amount of the mixed acid solution is as follows: when the using amount of the polycrystalline silicon is 30-50 g, the mixed acid liquid is 10-15 ml.
Preferably, in the mixed acid solution, the volume ratio of the nitric acid to the hydrofluoric acid is (0.5-5): 1.
Preferably, the nitric acid and the hydrofluoric acid are both electronic grade, the mass fraction of the nitric acid is 55-68%, and the mass fraction of the hydrofluoric acid is 38-44%.
Preferably, in step S102, the cleanliness of the rinsed environment is at least ten grades (national standard GB50073-2001), and the rinsing speed is 2-3 drops/second.
Preferably, in the step S103, the grade of water used for rinsing with water is at least laboratory first-grade water, and the amount of water is 0.5 to 1 time of the volume of the mixed acid solution.
Preferably, in the step S104, the heating temperature is 170 to 210 ℃.
Preferably, in the step S105, the amount of the nitric acid is 2% to 5% of the volume of the polysilicon surface metal detection sample obtained by constant volume.
Preferably, in the step S105, deionized water is used for the constant volume.
According to another aspect of the invention, a method for detecting a polysilicon surface metal detection sample is provided, which has the following technical scheme:
a method for detecting metal on the surface of polycrystalline silicon comprises the following steps:
s201, preparing a polycrystalline silicon surface metal detection sample by adopting the polycrystalline silicon surface metal detection sample preparation method;
s202, detecting the content of metal impurities in the prepared polycrystalline silicon surface metal detection sample by using an inductively coupled plasma mass spectrometer.
The invention has the following beneficial effects:
the method has the advantages that the metal impurities on the surface of the polycrystalline silicon can be quickly dissolved by leaching the surface of the polycrystalline silicon with the acid solution with higher acidity, compared with the traditional method of leaching with the acid solution with lower acidity, the leaching process is omitted, the sample preparation speed is higher, the preparation time of a detection sample can be greatly shortened, the detection period is shortened, the introduction of impurity elements such as K, Ca, Al and Fe from the environment can be reduced or avoided, the detection efficiency and the detection accuracy are improved, in addition, the heating is not needed in the acid pickling process, and the operation is simpler.
Drawings
FIG. 1 is a flow chart of a method for preparing a polysilicon surface metal detection sample according to an embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention will be further clearly and completely described below with reference to the accompanying drawings and specific examples of the present invention.
The method aims at the problems that in the prior art, a polycrystalline silicon surface metal detection sample is long in leaching time in a preparation process, and impurities such as K, Ca, Al and Fe are easily introduced from an introduction environment, so that the detection period is long, the detection accuracy is not high, and the like. Therefore, the invention discloses a preparation method of a polycrystalline silicon surface metal detection sample, which comprises the following steps:
s101, sampling: weighing polycrystalline silicon;
s102 acid washing: rapidly leaching the surface of the polycrystalline silicon by using a mixed acid solution of nitric acid and hydrofluoric acid to obtain a pickling solution;
s103, water washing: leaching the pickled polycrystalline silicon with water to obtain water scrubbing liquid;
s104, evaporation: heating the pickling solution and the water washing solution together until the pickling solution and the water washing solution are evaporated to dryness;
s105, constant volume: and adding nitric acid into the residue after evaporation to dryness for dissolving, and then performing constant volume on the dissolved solution obtained by dissolving to obtain a sample for detecting the metal on the surface of the polycrystalline silicon.
Correspondingly, the invention also provides a polycrystalline silicon surface metal detection method, which comprises the following steps:
s201, preparing a polycrystalline silicon surface metal detection sample by adopting the polycrystalline silicon surface metal detection sample preparation method;
s202, detecting the content of metal impurities in the prepared polycrystalline silicon surface metal detection sample by using an inductively coupled plasma mass spectrometer.
Example 1
As shown in fig. 1, the embodiment discloses a method for preparing a polysilicon surface metal detection sample, which comprises the following steps:
s101, sampling: and weighing the polycrystalline silicon.
The amount of acid liquor and water needed by subsequent acid washing and water washing is increased by considering too much polysilicon, the time required by the subsequent processes of drying by distillation and the like is prolonged, the sample preparation speed is reduced, the operation difficulty is increased by considering too little polysilicon, and the operation error is increased. Therefore, after a large number of tests, the amount of the polysilicon in the embodiment is preferably 30-50 g, and the mass of the weighed polysilicon is accurate to 0.0001g because the metal content of the polysilicon surface is in ppbw level.
S102 acid washing: and (3) rapidly leaching the surface of the polycrystalline silicon by adopting the mixture of nitric acid and hydrofluoric acid to obtain a pickling solution.
The nitric acid and the hydrofluoric acid for preparing the mixed acid liquid are both in electronic grade, so that the influence of metal ions possibly contained in the mixed acid liquid on the subsequent sample detection result is reduced. And the mass fraction of the electronic grade nitric acid is 55-68%, preferably 55% nitric acid, the mass fraction of the electronic grade hydrofluoric acid is 38-44%, preferably 38% hydrofluoric acid, the volume ratio of the nitric acid to the hydrofluoric acid is (0.5-5): 1, more preferably, the volume ratio of the nitric acid to the hydrofluoric acid is (2-3): 1, so that the prepared mixed acid has higher acidity and can react with metal on the surface of polycrystalline silicon in the leaching process to dissolve and deposit metal impurities on the surface of the polycrystalline silicon into acid liquor, and the acid liquor containing the metal impurities, namely the pickling liquor, has the advantages of short time compared with the traditional acid liquor leaching mode, greatly shortened preparation time of a detection sample, improved detection efficiency, no need of heating and simpler operation. The main reaction formula of the acid washing process is as follows:
X+H++NO3→X++NO+H2O
in the formula: x represents Cu, Fe, Zn, Ni, K, Ca, Al, Fe and other metals.
In the embodiment, the amount of the mixed acid solution is mainly determined according to the weighed polysilicon sample, and when the amount of the polysilicon is 30-50 g, the amount of the mixed acid solution is 10-15ml, so that the surface metal of the polysilicon can be completely dissolved in the pickling solution as far as possible.
In this embodiment, the cleanliness of the environment eluted by the mixed acid solution is at least ten levels (national standard GB50073-2001), so as to avoid introducing impurity elements such as K, Ca, Al, Fe, and the like from the environment. During acid washing, the leaching speed is 2-3 drops/second (counted by a commercially available liquid transfer device) so as to ensure that the acid solution and the metal impurities on the surface of the polycrystalline silicon completely react.
S103, water washing: and (4) leaching the pickled polycrystalline silicon with water to obtain water washing liquid.
In this embodiment, the water used in the water rinsing process is at least laboratory grade water, such as deionized water, ultrapure water, and the like, and the amount of water is 0.5 to 1.0 times the volume of the mixed acid solution in the acid washing process.
It should be noted that, because the mixed acid solution in this embodiment has strong corrosiveness, the container used in the pickling, washing, etc. process is preferably made of an acid-corrosive material, such as a beaker made of teflon.
S104, evaporation: heating the pickling solution and the water washing solution together until the pickling solution and the water washing solution are evaporated to dryness;
in the embodiment, the heating temperature in the evaporation process is 170-210 ℃, so that silicon in the pickling solution and the water washing solution is silicon tetrafluoride (SiF)4) The method can completely volatilize so as to reduce the influence of matrix effect on the subsequent detection of the content of the metal impurities and improve the detection accuracy. Furthermore, impurities in the polytetrafluoroethylene beaker can be ensured not to be precipitated under the condition of 170-210 ℃ (the precipitation temperature is about 250 ℃).
S105, constant volume: and adding nitric acid into the residue after evaporation to dryness for dissolving, and then performing constant volume on the dissolved solution obtained by dissolving to obtain a sample for detecting the metal on the surface of the polycrystalline silicon.
In this embodiment, the residue after evaporation is preferably dissolved by using nitric acid, the mass fraction of the nitric acid is 55% to 68%, preferably 55% nitric acid, and the usage amount of the nitric acid is 2% to 5% of the volume of the polysilicon surface metal detection sample obtained by constant volume, that is, when the volume of the polysilicon surface metal detection sample after constant volume is 10ml, the usage amount of the nitric acid is 0.2ml to 0.5 ml. And (3) after the residue is completely dissolved, adopting water without metal impurities, such as deionized water, ultrapure water and the like, to perform constant volume, and transferring the residue dissolved solution to a 10ml volumetric flask to perform constant volume to obtain the sample for detecting the metal on the surface of the polycrystalline silicon.
It should be noted that, because the content of the metal on the polysilicon surface is ppbw grade, the whole process in the embodiment is preferably performed in an environment with a cleanliness of at least ten grades, so as to reduce the introduction of metal impurities from the environment.
In the method for preparing the metal detection sample on the surface of the polycrystalline silicon, the acidity (as H) prepared by using the nitric acid and the hydrofluoric acid is higher+The mass percentage of (A) is as follows: the mixed acid solution with the acidity of 1.82% -1.91%) leaches the surface of the polycrystalline silicon, so that metal impurities on the surface of the polycrystalline silicon can be quickly dissolved, compared with the traditional method of leaching by adopting the acid solution with lower acidity, the method omits the leaching process, has higher sample preparation speed, not only can greatly shorten the preparation time of a detection sample, but also can reduce or avoid introducing impurity elements such as K, Ca, Al, Fe and the like from the environment, and has no need of heating in the acid washing process and simpler operation.
Several groups of preparation examples for preparing polysilicon surface metal detection samples by using the above preparation method for polysilicon surface metal detection samples are disclosed below, and it should be noted that the following preparation examples are only a limited number of examples, and are not limited thereto.
Preparation example 1
The preparation embodiment discloses a preparation method of a polycrystalline silicon surface metal detection sample, which comprises the following steps:
(1) 30.0000g of polysilicon was weighed and placed in a polytetrafluoroethylene beaker.
(2) Placing the beaker filled with the polycrystalline silicon in a fume hood with the cleanliness reaching ten levels; preparing mixed acid liquid by using 55% by mass of nitric acid solution and 38% by mass of hydrofluoric acid solution according to the volume ratio of 2: 1; and taking 10ml of the mixed acid liquid by using a liquid transfer device, and quickly spraying the mixed acid liquid onto the surface of the polycrystalline silicon (namely acid leaching) at the speed of 2-3 drops/second (the amount of each drop is controlled to be about 0.2 ml), so that the metal impurities on the surface of the polycrystalline silicon are quickly dissolved, and the pickling solution containing the metal impurities is obtained.
(3) And slowly spraying 5ml of deionized water onto the surface of the polycrystalline silicon subjected to the mixed acid solution spraying (namely water spraying) to obtain water washing liquid.
(4) And merging the pickling solution and the water washing solution, heating to dryness at 170 ℃, and volatilizing silicon in the pickling solution and the water washing solution in the form of silicon tetrafluoride.
(5) And adding 0.2ml of nitric acid with the mass fraction of 68% into the residue obtained after evaporation to dryness to fully dissolve the residue, and adding 9.8ml of deionized water to a constant volume to obtain a sample for detecting the metal on the surface of the polycrystalline silicon.
Preparation example 2
The embodiment discloses a preparation method of a polycrystalline silicon surface metal detection sample, which comprises the following steps:
(1) 40.0000g of polycrystalline silicon was weighed and placed in a teflon beaker.
(2) Placing the beaker filled with the polycrystalline silicon in a fume hood with the cleanliness reaching ten levels; preparing mixed acid liquid by using a nitric acid solution with the mass fraction of 60% and a hydrofluoric acid solution with the mass fraction of 40% according to the volume ratio of 3: 1; and taking 15ml of the mixed acid solution by using a liquid transfer device, and quickly spraying the mixed acid solution onto the surface of the polycrystalline silicon at a speed of 2-3 drops/second (namely acid leaching), so that the metal impurities on the surface of the polycrystalline silicon are quickly dissolved, and the pickling solution containing the metal impurities is obtained.
(3) And slowly spraying 15ml of ultrapure water onto the surface of the polycrystalline silicon subjected to the mixed acid solution spraying (namely water spraying) to obtain a water washing solution.
(4) And merging the pickling solution and the water washing solution, heating to be dried by distillation at 180 ℃, and volatilizing silicon in the pickling solution and the water washing solution in a form of silicon tetrafluoride.
(5) And adding 0.4ml of nitric acid with the mass fraction of 60% into the residue obtained after evaporation to dryness to fully dissolve the residue, and adding 9.6ml of ultrapure water to a constant volume to obtain a sample for detecting the metal on the surface of the polycrystalline silicon.
Preparation example 3
The embodiment discloses a preparation method of a polycrystalline silicon surface metal detection sample, which comprises the following steps:
(1) 50.0000g of polysilicon was weighed and placed in a polytetrafluoroethylene beaker.
(2) Placing the beaker filled with the polycrystalline silicon in a fume hood with the cleanliness reaching ten levels; preparing a mixed acid solution by using a nitric acid solution with the mass fraction of 65% and a hydrofluoric acid solution with the mass fraction of 42% according to the volume ratio of 4: 1; and taking 12ml of the mixed acid liquor by using a liquid transfer device, and quickly spraying the mixed acid liquor onto the surface of the polycrystalline silicon at the speed of 2-3 drops/second (namely acid leaching), so that the metal impurities on the surface of the polycrystalline silicon are quickly dissolved, and the pickling liquor containing the metal impurities is obtained.
(3) And slowly spraying 18ml of deionized water onto the surface of the polycrystalline silicon subjected to the mixed acid solution spraying (namely water spraying) to obtain a water washing solution.
(4) And merging the pickling solution and the water washing solution, heating to be dried at 190 ℃, and volatilizing silicon in the pickling solution and the water washing solution in the form of silicon tetrafluoride.
(5) And adding 0.5ml of nitric acid with the mass fraction of 55% into the residue obtained after evaporation to dryness to fully dissolve the residue, and adding 9.5ml of deionized water to a constant volume to obtain a sample for detecting the metal on the surface of the polycrystalline silicon.
Example 2
The embodiment also discloses a polysilicon surface metal detection method, which comprises the following steps:
s201 sample preparation: the polycrystalline silicon surface metal detection sample is prepared by the polycrystalline silicon surface metal detection sample preparation method described in example 1.
S202, detection: and detecting the content of metal impurities in the prepared polycrystalline silicon surface metal detection sample by using an inductively coupled plasma mass spectrometer.
It should be noted that, in the detection process in this embodiment, the content of the metal impurities may also be detected by a method other than the ICP-MS method using an inductively coupled plasma mass spectrometer (e.g., the ICP-AES method using an inductively coupled plasma atomic emission spectrometer), and this embodiment is not limited further.
In this embodiment, six groups of mixed acid solutions are prepared according to the volume ratio of nitric acid to hydrofluoric acid of 0.5:1, 1:1, 2:1, 3:1, 4:1 and 5:1 in sequence, six groups of polycrystalline silicon surface metal detection samples are prepared by the preparation method of the polycrystalline silicon surface metal detection sample described in preparation example 1 in embodiment 1, and then the metal impurity content of the prepared six groups of polycrystalline silicon surface metal detection samples is detected by using an inductively coupled plasma mass spectrometer under the same conditions, and the obtained detection results are shown in table 1:
TABLE 1 content of metallic impurities detected on the surface of polycrystalline silicon in mixed acid solution with different proportions
As can be seen from table 1, the volume ratio of nitric acid to hydrofluoric acid was 2:1 and 3:1, the detected content data of the metal on the surface of the polycrystalline silicon is relatively stable and is also relatively close to each other, and at this time, basically, the mixed acid solution prepared at the volume ratio can be considered to be just capable of dissolving the metal impurities on the surface of the polycrystalline silicon, so that the mixed acid solution prepared at the volume ratio of (2-3): 1 of nitric acid and hydrofluoric acid is preferably used as the rinse solution in the acid washing process in the embodiment.
According to the method for detecting the metal on the surface of the polycrystalline silicon, the surface of the polycrystalline silicon is leached by the acid liquor with high acidity, so that the metal impurities on the surface of the polycrystalline silicon can be quickly dissolved, compared with the traditional method of leaching by the acid liquor with low acidity, the leaching process is omitted, the sample preparation speed is higher, the preparation time of a detection sample can be greatly shortened, the detection period is shortened, the introduction of impurity elements such as K, Ca, Al and Fe from the environment can be reduced or avoided, the detection efficiency and the detection accuracy are improved, in addition, the acid washing process does not need heating, and the operation is simpler.
It will be understood that the foregoing is only a preferred embodiment of the invention, and that the invention is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention, and these changes and modifications are to be considered as within the scope of the invention.
Claims (10)
1. A preparation method of a polycrystalline silicon surface metal detection sample comprises the following steps:
s101, sampling: weighing polycrystalline silicon;
s102 acid washing: rapidly leaching the surface of the polycrystalline silicon by using a mixed acid solution of nitric acid and hydrofluoric acid to obtain a pickling solution;
s103, water washing: then, carrying out water leaching on the pickled polycrystalline silicon to obtain water washing liquid;
s104, evaporation: heating the pickling solution and the water washing solution together until the pickling solution and the water washing solution are evaporated to dryness;
s105, constant volume: and adding nitric acid into the residue after evaporation to dryness for dissolving, and then carrying out constant volume on the dissolved solution obtained by dissolving to obtain the polysilicon surface metal detection sample.
2. The method for preparing the polycrystalline silicon surface metal detection sample as claimed in claim 1, wherein the amount of the mixed acid solution is as follows: when the using amount of the polycrystalline silicon is 30-50 g, the mixed acid liquid is 10-15 ml.
3. The method for preparing the polycrystalline silicon surface metal detection sample as claimed in claim 1, wherein the volume ratio of the nitric acid to the hydrofluoric acid in the mixed acid solution is (0.5-5): 1.
4. The preparation method of the polysilicon surface metal detection sample according to claim 3, wherein the nitric acid and the hydrofluoric acid are both at an electronic level, and the mass fraction of the nitric acid is 55-68% and the mass fraction of the hydrofluoric acid is 38-44%.
5. The method for preparing a polysilicon surface metal detection sample according to claim 1, wherein in the step S102,
the cleanliness of the leaching environment is at least ten grades, and the leaching speed is 2-3 drops/second.
6. The method for preparing the polysilicon surface metal detection sample according to claim 1, wherein in the step S103, the water used for rinsing is at least laboratory first-grade water, and the amount of the water is 0.5-1 times of the volume of the mixed acid solution.
7. The method for preparing a polysilicon surface metal detection sample according to claim 1, wherein in the step S104, the heating temperature is 170-210 ℃.
8. The method for preparing the polysilicon surface metal detection sample according to claim 1, wherein in the step S105, the amount of the nitric acid is 2-5% of the volume of the polysilicon surface metal detection sample obtained by constant volume.
9. The method for preparing a polysilicon surface metal detection sample according to claim 1, wherein in the step S105, deionized water is used for the constant volume.
10. A method for detecting metal on the surface of polycrystalline silicon is characterized by comprising the following steps:
s201, preparing a polycrystalline silicon surface metal detection sample by using the polycrystalline silicon surface metal detection sample preparation method of any one of claims 1 to 9;
s202, detecting the content of metal impurities in the prepared polycrystalline silicon surface metal detection sample by using an inductively coupled plasma mass spectrometer.
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