CN106526015A - Apparatus for detecting trace phosphor impurity in hydrogen and detection method thereof - Google Patents

Abstract

The invention discloses a detection device and detection method for trace phosphorus impurities in hydrogen gas. Firstly, a temperature-variable concentration device is used to concentrate phosphorus impurities in hydrogen gas, and then the phosphorus impurities are detected by a gas chromatograph FPD detector after desorption. The peak area is quantified by external standard method, and the detection limit is as low as sub-ppb level, which can meet the quality requirements of electronic grade polysilicon for hydrogen. The invention has low detection limit, simple operation, the detection process can be completed in half an hour, and the detection result has good repeatability. The ability to accurately detect the content of trace phosphorus impurities in hydrogen used for polysilicon production is of great significance to the quality control of polysilicon products.

Description

Detection device and method for trace phosphorus impurity in hydrogen

technical field

The invention belongs to the technical field of polysilicon production, in particular to the detection field of trace phosphorus in hydrogen gas for polysilicon production, and specifically relates to a concentration device and detection method for trace phosphorus impurities in hydrogen gas used for polysilicon.

Background technique

Hydrogen is an important raw material in polysilicon production. Its quality control is generally carried out in accordance with "Hydrogen" GB/T 3634.2-2011. Only the content of impurities such as nitrogen, oxygen, argon, carbon monoxide, carbon dioxide, methane, and moisture is detected, which has the greatest impact on polysilicon production. Impurity phosphorus has no corresponding index requirements and detection methods.

As the intrinsic quality of polysilicon increases to electronic-grade levels, the production system becomes particularly sensitive to fluctuations in the quality of hydrogen. The content of phosphorus impurities in hydrogen is one of the main factors that directly restrict the intrinsic quality of polysilicon. The establishment of a detection method for trace phosphorus impurities in hydrogen can provide reliable data support for production quality control and ensure the stability and improvement of the intrinsic quality of polysilicon.

After reviewing relevant information and conducting experiments, phosphorus mainly exists in the form of phosphine in hydrogen gas, and the content requirement is less than ppbv. Phosphine, a colorless gas, has the peculiar smell of mustard and garlic, but industrial products have a rotten fish-like smell, highly flammable, highly toxic, corrosive, and harmful to the environment. Inhalation of phosphine can harm the heart, Respiratory system, kidney, stomach, nervous system and liver are affected, exposure limit: 0.3mg/m ³ , boiling point -87.7℃, slightly soluble in water, easily soluble in ethanol.

At present, there is basically no detection of phosphorus impurities in hydrogen in the industry, and only the detection methods of phosphorus impurities in the air can be found. The conventional methods are mainly ammonium molybdate colorimetry and gas chromatography. The former ammonium molybdate colorimetric method needs to absorb phosphine and a strong oxidant to generate orthophosphate, and then use a spectrophotometer to indirectly detect the content of phosphine. This method is only suitable for high-concentration occasions. Phosphate in hydrogen Hydrogen was below its detection limit and could not be detected. The latter gas chromatographic detection method, such as FPD detector, can only detect PH3 of about 0.1ppmv, which cannot meet the requirements of polysilicon, especially electronic grade polysilicon production, for phosphorus impurity content less than ppbv.

Contents of the invention

The technical problem to be solved by the present invention is to provide a detection device and detection method for trace phosphorus impurities in hydrogen, which have simple structure, convenient operation, short analysis time and high sensitivity.

In order to solve the above technical problems, the technical solution adopted in the present invention is: a detection device for trace phosphorus impurities in hydrogen, including a first cut-off valve, a mass flow controller, a first six-way valve, a second cut-off valve connected in sequence valve and vent pipe; the first six-way valve is connected with the concentration column to form a closed loop; the first six-way valve is also connected with carrier gas pipeline and chromatographic column respectively, and the chromatographic column is also connected with FPD detector; Or desorbing phosphorus impurities are respectively equipped with a cooling device or a heating device.

The cooling device is a container containing liquid nitrogen, and the heating device is a container containing hot water.

An electronic flow control system is also provided on the carrier gas pipeline.

The detection device is also provided with a second six-way valve, which is connected with the quantitative loop to form a closed loop, and the second six-way valve is also connected with the sample inlet, the sample outlet, the carrier gas inlet and the carrier gas outlet respectively.

The concentration column is an SE-30 column, which is a Φ3mm×0.6m stainless steel column, filled with 100% dimethyl polysiloxane, and has a column capacity of 1mL-1.5mL. It has a good adsorption and desorption effect on phosphorus, and the capacity of 1-1.5mL can not only achieve a good concentration effect, but also control the injection volume, which will not cause chromatographic peak tailing.

The present invention also relates to a method for detecting trace phosphorus impurities in hydrogen, comprising the following steps:

1) During the concentration process, the first six-way valve is set on the sampling position, and the sample gas first passes through the concentration device. Under low temperature conditions, the trace phosphorus impurities in the sample gas are absorbed in the concentration column, and the hydrogen in the sample gas is discharged. And record the volume of sample gas passing through the concentration column to determine the concentration multiple;

2) Cancel the low temperature condition of the concentration device during the detection process, discharge the excess hydrogen in the concentration column, heat the concentration column to desorb the phosphorus impurities adsorbed in the concentration column, turn the first six-way valve to the sample injection position, and pass the The phosphorus impurities are brought into the chromatographic column by the gas for separation, and the peak area of phosphorus is measured with an FPD detector; the content of phosphorus impurities in the sample gas is calculated according to the concentrated volume.

The flow rate during concentration of the sample gas is 300mL-500mL/min, which can effectively ensure the analysis efficiency and the recovery rate during concentration. The concentration time is between 3 minutes and 5 minutes, and the volume of the concentrated gas is less than 2500mL, which meets the recovery requirement.

The low temperature condition is achieved by immersing the concentrating device in a container filled with liquid nitrogen, and a hot water bath is used for heating. Further, the temperature of the hot water is 60°C-70°C, which can effectively decompose the phosphorus-containing impurities in the hydrogen, and prevent impurities such as chlorosilanes that may exist in the hydrogen for polysilicon production from depositing in the concentration column.

The present invention detects trace phosphorus impurities in hydrogen by combining a concentration device with a gas chromatograph FPD; the principle is: the hydrogen is sampled from a pipeline or steel cylinder, and enters the concentration device after decompression, and the phosphorus impurities are removed at low temperature (liquid nitrogen temperature). Adsorption, the hydrogen cannot be adsorbed and continuously vented through the vent port, the concentrated volume of hydrogen is accurately measured, and then the temperature is raised for desorption, and the concentrated phosphorus impurities are brought into the gas chromatograph with the carrier gas, separated by the chromatographic column and detected by the FPD detector. Calculate the total amount of phosphorus in the sample by comparing the peak area of the sample with the peak area of the phosphorus chromatogram in the standard gas, and convert the concentration of phosphorus in the hydrogen gas into the sample according to the hydrogen concentration volume.

The device and detection method of the present invention have the following advantages and beneficial effects:

1) The device of the present invention is continuously vented through the vent pipe, and the concentration ratio of 0.1ppm (v/v) phosphine standard gas can theoretically be more than ¹⁰⁷ , because the actual gas contains other impurity gases and the concentration ratio is high and the chromatographic peak Due to factors such as tailing, it is determined through experiments that the concentration ratio can basically reach more than 1000-3000 times, with good linearity and repeatability, so that the detection limit of phosphine in hydrogen is as low as 0.1ppb (v/v).

2) the device of the present invention can accurately control the gas flow and the calculated volume through the mass flow controller, and the pressure in the reaction concentration device can be used and cooperated with the gas chromatograph preferably, so that the detection method has a good weight performance and stability.

3) The device and detection method of the present invention have the advantages of simple structure, convenient operation, short analysis time and high sensitivity.

Description of drawings

Fig. 1 is a schematic structural diagram of the device provided by the present invention.

In the figure: 1. The first stop valve, 2. The mass flow controller, 3. The first six-way valve, 4. The concentration column, 5. The second stop valve, 6. Cooling device or heating device, 7. Vent pipe , 8, the second six-way valve, 9, quantitative loop, 10, electronic flow control, 11, chromatographic column, 12, FPD detector.

detailed description

Below in conjunction with embodiment, further illustrate the present invention. These examples should be understood as only for illustrating the present invention but not for limiting the protection scope of the present invention. After reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

A detection device for trace phosphorus impurities in hydrogen, comprising a first stop valve 1, a mass flow controller 2, a first six-way valve 3, a second stop valve 5, and a vent pipe 7 connected in sequence; the first six-way Valve 3 is connected with concentration column 4 to form a closed loop; the first six-way valve 3 is also connected with carrier gas pipeline 13 and chromatographic column 11 respectively, and chromatographic column 11 is also connected with FPD detector; Phosphorous impurities are respectively provided with a cooling device or a heating device 6 .

Further, the cooling device is a container containing liquid nitrogen, and the heating device is a container containing hot water.

Further, an electronic flow control system 10 is also provided on the carrier gas pipeline 13 .

Further, the detection device is also provided with a second six-way valve 8, the second six-way valve 8 is connected with the quantitative loop 9 to form a closed circuit, and the second six-way valve 8 is also connected with a sample inlet, a sample outlet and a carrier gas inlet respectively. and carrier gas outlet.

Further, the said concentration column is an SE-30 column, which is a Φ3mm×0.6m stainless steel column, filled with 100% dimethylpolysiloxane, and the column capacity is 1mL-1.5mL.

Comparative example 1:

0.1ppm (v/v) phosphine standard gas C ₀ direct sampling experiment

1) Experimental steps: After the standard gas is decompressed, it is connected to the second six-way valve, and the second six-way valve is set to the sampling position, and replaced for 1 minute, then the second six-way valve is set to the sampling position, and the standard gas After entering the gas chromatograph, it is detected by the FPD detector, and the peak area A ₀ of phosphine in the standard gas is measured.

2) Experimental conditions: Chromatographic column: DC550, 1/8in×3m, 17.5%, DB-1, 0.53mm*30m*1um; instrument: Agilent7890A, equipped with FPD detector; inlet temperature: 150°C; column temperature: The initial temperature is 45°C, hold for 3min, rise to 150°C at 15°C/min, hold for 3min; carrier gas flow rate: 15mL/min; FPD detector temperature: 220°C; volume of quantitative loop V ₀ : 1mL.

3) The above experiment was repeated 6 times, and the experimental results are shown in Table 1. The relative standard deviations of retention time, peak area, peak height, and noise were all less than 5%, meeting the reproducibility requirements of the method:

Table 1 Experimental data of 1mL standard gas

4) Calculation of method detection limit DL when not concentrated:

DL＝3Nc/h (N: noise; c: standard gas concentration; h: standard gas peak height)

=3*9.13*0.1/74.87

＝0.036ppm(v/v)

Embodiment 1: 0.1ppm (v/v) phosphine standard gas carries out concentration detection experiment as sample gas

Experimental procedure: Two steps are used: the concentration process and the analysis and detection process. During the concentration process, the sample gas is decompressed and connected to the first six-way valve. The first six-way valve is placed on the sampling position, and the first cut-off valve is opened. Valve and the second shut-off valve, replace for 1 minute, close the second shut-off valve, cushion the gas for 30 seconds, raise the liquid nitrogen cup, so that the concentration column is completely submerged in the liquid nitrogen, open the second shut-off valve after the flow is stable, and the phosphine Adsorbed by the concentration column at liquid nitrogen temperature, hydrogen cannot be absorbed, and the second stop valve is continuously emptied, and the gas volume passing through the concentration column is accurately recorded by the mass flow controller, and concentrated to the required volume V (1000mL, 1500mL, 2000mL) , close the first cut-off valve; then carry out the detection and analysis step, put down the liquid nitrogen, vent the excess hydrogen in the concentration column through the second stop valve, close the second stop valve, and immerse the concentration column with a 60°C-70°C water bath to make the phosphorus The hydrogen hydride is desorbed, and after 1 minute, the first six-way valve is turned to the sampling position, and the phosphorus impurities are brought into the chromatographic column through the carrier gas for separation, and the FPD detector measures the peak area A of the phosphine in the sample gas.

1. Experimental conditions: Concentration column: SE-30 column, Φ3mm×0.6m stainless steel column; Concentration flow rate: 500mL/min.

2. Calculation of results: the concentration C of phosphine in the sample gas is

C ------ PH ₃ content (volume fraction) in the sample gas;

A------Peak area of PH ₃ in the sample gas;

C ₀ ------ the content of PH ₃ in the standard gas (volume fraction);

V ₀ ------- standard gas volume (mL), this experiment uses a 1mL quantitative loop;

A ₀ ------ peak area of PH ₃ in standard gas;

V-------concentrated volume of sample gas (mL).

3. According to the above-mentioned experimental steps, experimental conditions and calculation results, the PH3 standard gas volume of 0.1ppmv was concentrated to 500mL, 1000mL, 1500mL, and 2000mL as the sample gas for testing, and the experiment was repeated 6 times. Analysis, the analysis results are shown in Table 2-Table 5 below:

Table 2 Experimental data of concentrated 500mL

Table 3 Concentrated 1000mL experimental data

Table 4 Concentrated 1500mL experimental data

Table 5 Concentrated 2000mL experimental data

4. It can be seen from the above table that the relative standard deviations of the peak area, unit peak area, and calculated concentration under various concentration multiples are all less than 5%, which meets the repeatability requirements of the method; the recovery rate is between 84.08% and 101.51%, achieving relatively Good recycling effect.

5, according to the concentration volume of above-mentioned 500,1000,1500,2000 times, with the peak area of phosphine and the concentration multiple fitting linear equation: y=685.66x, y is the peak area (pA*s) of phosphine, x is the concentrated volume (mL), the fitting coefficient R=0.9963, and the detection limit of the method is calculated by 2000 times the concentrated volume=DL/2000=0.018ppb (v/v).

Example 2: Concentration and detection of polysilicon with hydrogen

According to the experimental procedures, experimental conditions, and result calculations of Example 1, the sample hydrogen in polysilicon production was taken to concentrate 1000mL, and the concentration experiment was repeated 6 times. The experimental results are shown in Table 6:

Table 6 Experimental data of sample gas enriched 1000 times

From the above results, its relative standard deviation is 4.42-6.15%, which has good repeatability, and the circulating hydrogen and phosphorus content has large fluctuations, so it is the key monitoring object in production.

The above description is not intended to limit the present invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. A detection device for trace phosphorus impurities in hydrogen, characterized in that it includes a first cut-off valve (1), a mass flow controller (2), a first six-way valve (3), and a second cut-off valve connected in sequence. valve (5) and vent pipe (7); the first six-way valve (3) is connected to the enrichment column (4) to form a closed loop; the first six-way valve (3) is also connected to the carrier gas pipeline (13) and The chromatographic column (11), the chromatographic column (11) is also connected with an FPD detector; the concentration column (4) is respectively equipped with a cooling device or a heating device (6) according to adsorption or desorption of phosphorus impurities. 2. The detection device according to claim 1, wherein the cooling device is a container filled with liquid nitrogen, and the heating device is a container filled with hot water. 3. The detection device according to claim 1, characterized in that: the carrier gas pipeline (13) is also provided with an electronic flow control system (10). 4. The detection device according to claim 1 or 3, characterized in that: the detection device is also provided with a second six-way valve (8), and the second six-way valve (8) is connected with the quantitative loop (9) to form a closed loop , the second six-way valve (8) is also connected with sample inlet, sample outlet, carrier gas inlet and carrier gas outlet respectively. 5. The detection device according to claim 1, characterized in that: the concentration column is an SE-30 column, which is a Φ3mm×0.6m stainless steel column, and the packing is 100% dimethylpolysiloxane. The column capacity is 1mL~ 1.5mL. 6. A detection method for trace phosphorus impurities in hydrogen, characterized in that, comprising the following steps: 1) During the concentration process, the first six-way valve is set on the sampling position, and the sample gas first passes through the concentration device. Under low temperature conditions, the trace phosphorus impurities in the sample gas are adsorbed in the concentration column, and the hydrogen in the sample gas is discharged. And record the volume of sample gas passing through the concentration column to determine the concentration multiple; 2) Cancel the low temperature condition of the concentration device during the detection process, discharge the excess hydrogen in the concentration column, heat the concentration column to desorb the phosphorus impurities adsorbed in the concentration column, turn the first six-way valve to the sample injection position, and pass the loading The phosphorus impurities are brought into the chromatographic column by the gas for separation, and the peak area of phosphorus is measured with an FPD detector; the content of phosphorus impurities in the sample gas is calculated according to the concentrated volume. 7. The detection method according to claim 5, characterized in that: the flow rate when the sample gas is concentrated is 300mL/min-500mL/min, and the concentration time is 3min-5min. 8. The detection method according to claim 5, characterized in that: the low temperature condition is achieved by immersing the concentrating device in a container filled with liquid nitrogen, and heating is carried out in a hot water bath. 9. The detection method according to claim 8, characterized in that: the temperature of the hot water is 60°C-70°C.