Method for testing content of ppq-grade metal in hydrofluoric acid

Abstract

The method comprises the following steps: after a sample bottle is soaked in HF, the content of ppq-level key metals in hydrofluoric acid is detected by adopting inductively coupled plasma mass spectrometry (ICP-MS), the key metals are 13 key elements of sodium, magnesium, aluminum, potassium, calcium, cadmium, iron, cobalt, nickel, copper, zinc, silver and lead, and the MDL of each of the 13 key elements is less than 0.5 ppt.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic-grade hydrofluoric acid trace detection, and specifically is a detection method that improves the limit capability that can be achieved by the world's most advanced production detection technology for metal content in hydrofluoric acid from 1ppt to ppq level. Background Art

[0002] As one of the key basic chemical materials in the microelectronics industry, electronic-grade hydrochloric acid can be used in combination with nitric acid, glacial acetic acid, hydrogen peroxide and ferric hydroxide, and is widely used in large-scale integrated circuits. It is mainly used for cleaning and etching chips, and can also be used as an analytical reagent and for preparing high-purity fluorine-containing chemicals. Its purity and cleanliness have a very important impact on the yield, electrical properties and reliability of integrated circuits. With the rapid development of the semiconductor industry, the industry is constantly updating, and the quality demand for electronic-grade hydrofluoric acid is also increasing year by year. At present, the world's most advanced hydrofluoric acid production and inspection technology can achieve a limit capacity of 1ppt (1ppt=1000ppq). In order to ensure the continuous improvement of product quality, higher-precision hydrofluoric acid inspection technology is particularly important. Summary of the invention

[0003] In view of the above problems, the present invention provides a ppq-level metal content inspection technology in hydrofluoric acid, which adopts a unique sampling process and specific instrument parameters to increase the detection limit of 13 key cations of sodium, magnesium, aluminum, potassium, calcium, cadmium, iron, cobalt, nickel, copper, zinc, silver and lead in electronic grade hydrofluoric acid from ppt level to ppq level.

[0004] A method for testing the ppq level metal content in hydrofluoric acid adopts inductively coupled plasma mass spectrometry (ICP-MS) to detect the ppq level key metal content in hydrofluoric acid, wherein the key metals are 13 key elements including sodium, magnesium, aluminum, potassium, calcium, cadmium, iron, cobalt, nickel, copper, zinc, silver and lead, and the MDLs of the 13 key elements are all less than 0.5ppt.

[0005] The specific steps include: A. Sample vial preparation: A1. Place the sample bottle completely in SG-grade HF, soak it in a warm room, take out the sample bottle, shake the bottle, pour out the HF in the bottle, and clean the water seal with ultrapure water; A2. Fill the sample bottle treated in A1 with SG-grade HF, test it on the machine, and get the 0-hour test result; after leaving it for 144 hours, test it again on the machine and get the 144-hour test result; after the test is qualified, wash the sample bottle with ultrapure water, and seal it with ultrapure water until it is put into sampling operation; If the test fails, repeat steps A1 and A2 until the test passes, clean the sample bottle, and seal it with ultrapure water until it is ready for sampling. Among them, the test qualification standard: metal content test result <5ppt; B. Sampling: B1. Fill the sample bottle 2 to 4 parts full with SG grade hydrofluoric acid; B2. With the bottle mouth facing downward, shake the bottle up and down; then rotate it 120°, 240° and 360° in sequence, shaking the bottle after each rotation; B3. With the bottle mouth facing upwards, shake the bottle up and down; then rotate it 120°, 240° and 360° in sequence, shaking the bottle after each rotation; B4. With the bottle mouth facing downwards and the bottle body tilted, pour and rotate until the hydrofluoric acid is emptied; B5. Repeat steps B1 to B4 three times; C. ICP-MS injection: C1. Use the standard addition method to draw a standard curve; C2. Inject the sample to be tested and obtain the test results of 13 elements including sodium, magnesium, aluminum, potassium, calcium, cadmium, iron, cobalt, nickel, copper, zinc, silver and lead through the standard curve.

[0006] The sample injection system, atomization system, platinum cone and rectangular tube of the platinum center tube of the ICP-MS are all made of hydrofluoric acid resistant materials.

[0007] The shaking time of the bottle is 20 to 40 seconds.

[0008] The SG grade hydrofluoric acid is 10ppt grade hydrofluoric acid.

[0009] The step A1 of soaking in a greenhouse is specifically soaking in a greenhouse at 50-60° C. for 3-4 months.

[0010] The instrument parameters for the ICP-MS injection test were set as follows: Mode: Cool RF power: 650~850W Sampling depth: 16.5~19.0mm Atomizing gas: 0.75~0.90L / min Compensation gas: 0.80~0.90L / min Extraction lens 1: -70~-80V Extraction lens 2: -5.5V Omega deflection voltage: -46V Omega lens voltage: 1.9V Helium flow rate: 0.5~1.5ml / min Ammonia-helium mixed gas flow rate: 20% Octopole deflection voltage: -6.0~-7.0V Octopole RF: 140~160V Energy discrimination: -4.0~-5.0V Torch horizontal position: -0.6mm Torch vertical position: -1.6mm; The ammonia-helium mixture includes 10% NH3 and 90% He.

[0011] Preferably, the instrument parameters of the ICP-MS injection test are set as follows: Mode: Cool RF power: 750W Sampling depth: 18.0mm Atomizing gas: 0.75L / min Make-up gas: 0.90L / min Extraction lens 1: -78.4V Extraction lens 2: -5.5V Omega deflection voltage: -46V Omega lens voltage: 1.9V Helium flow rate: 1.0ml / min Ammonia-helium mixed gas flow rate: 20% Octopole deflection voltage: -7.0V Octopole RF: 150V Energy Discrimination: -5.0V Torch horizontal position: -0.6mm Torch vertical position: -1.6mm; The ammonia-helium mixture includes 10% NH3 and 90% He.

[0012] The on-machine test described in step A2 is ICP-MS detection.

[0013] The standard curve described in step C1 is established by using 49% HF sample to be tested without dilution as the base, using the standard addition method, and establishing a standard curve with 0 / 10 / 20 / 30 / 50 ppt. The specific establishment steps are as follows: 1) Spike 0ppt: Take a pre-treated 100ml sample bottle and place it on a balance to peel it. Pour clean 49% HF sample into the bottle in an ultra-clean bench. Do not return the balance to zero and test it on the machine. 2) Add 10ppt: After adding 0ppt, accurately weigh the remaining sample weight in the sample bottle, calculate the weight of the 1ppb standard solution to be added, add the standard solution to the remaining sample, and test on the machine; 3) According to the method in step 2), perform 20, 30, and 50 ppt spike tests in turn, and obtain a standard curve based on the test results; the R value of the standard curve must be >0.995 before it can be used.

[0014] The sample bottle is a PFA sample bottle.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The test method provided by the present invention can accurately and stably detect 13 ppq-level key metal elements in hydrofluoric acid, the MDL of the 13 metal elements are all less than 0.5ppt, and the spiked recovery rate is between 89.5% and 110.5%. The more accurate hydrofluoric acid test technology provided by the present invention is conducive to ensuring the continuous improvement of the quality of ultra-high purity hydrofluoric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The standard curves of 13 key elements obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0017] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0018] Example 1 In the embodiment, SG grade hydrofluoric acid is 10ppt grade hydrofluoric acid.

[0019] The instrument parameters for the ICP-MS injection test were set as follows: Mode: Cool RF power: 750W Sampling depth: 18.0mm Atomizing gas: 0.75L / min Make-up gas: 0.90L / min Extraction lens 1: -78.4V Extraction lens 2: -5.5V Omega deflection voltage: -46V Omega lens voltage: 1.9V Helium flow rate: 1.0ml / min Ammonia-helium mixed gas flow rate: 20% (ammonia-helium ratio: 10% NH3 + 90% He) Octopole deflection voltage: -7.0V Octopole RF: 150V Energy Discrimination: -5.0V Torch horizontal position: -0.6mm Torch vertical position: -1.6mm.

[0020] A. Sample vial preparation: A1. Place the PFA bottle completely in SG-grade HF and soak it in a 55°C warm room for 4 months. Take out the PFA bottle, shake it for 30 seconds, pour out the HF in the bottle, and clean the water seal with ultrapure water. A2. The PFA bottle treated by A1 is filled with SG-grade HF, and the machine is tested to obtain the 0-hour test result; after 144 hours of storage, the machine is tested again to obtain the 144-hour test result; after the test is qualified, the sample bottle is cleaned with ultrapure water and sealed with ultrapure water until it is put into sampling operation; the machine test is ICP-MS detection; If the test fails, repeat steps A1 and A2 until the test passes, clean the PFA bottle and seal it with ultrapure water until it is ready for sampling; The test qualification standard: metal content test result <5ppt; B. Sampling: B1. The sample bottle is 30% full of SG grade hydrofluoric acid; B2. With the bottle mouth facing downward, shake the bottle up and down; then rotate it 120°, 240° and 360° in sequence, shaking the bottle for 30 seconds after each rotation; B3. With the bottle mouth facing upwards, shake the bottle up and down; then rotate it 120°, 240° and 360° in sequence, shaking the bottle for 30 seconds after each rotation; B4. With the bottle mouth facing downwards and the bottle body tilted, pour and rotate until the hydrofluoric acid is emptied; B5. Repeat steps B1 to B4 three times; C. ICP-MS injection: C1. Use the standard addition method to draw a standard curve; The standard curve is established by using 49% HF sample to be tested without dilution as the base, and using the standard addition method to establish a standard curve with spikes of 0 / 10 / 20 / 30 / 50ppt. The specific establishment steps are as follows: 1) Spike 0ppt: Take a pre-treated 100ml sample bottle and place it on a balance to peel it. Pour clean 49% HF sample into the bottle in an ultra-clean bench. Do not return the balance to zero and test it on the machine. 2) Add 10ppt: After adding 0ppt, accurately weigh the remaining sample weight in the sample bottle, calculate the weight of the 1ppb standard solution to be added, use a pipette to draw the standard solution and add it to the remaining sample, and then test on the machine; 3) According to the method in step 2), perform the 20, 30, and 50 ppt spike point tests in turn, and obtain the standard curve based on the test results; the standard curve can only be used if the R value is >0.995. The standard curves of the 13 key elements are shown in Figure 1 .

[0021] C2. The sample to be tested is injected, and the test results of 13 key elements including sodium, magnesium, aluminum, potassium, calcium, cadmium, iron, cobalt, nickel, copper, zinc, silver and lead are obtained through the standard curve.

[0022] MDL Test: (1) Select about 50g of SG-grade HF in a 100ml PFA bottle and test it on ICP-MS. If the 13 elements Na, Mg, Al, K, Ca, Cr, Fe, Co, Ni, Cu, Zn, Ag, and Pb are all <3ppt, then the next step can be carried out; (2) Add 200 ppb standard solution to the above SG grade HF sample to make its concentration 1 ppt; (3) The solution in (2) was tested by ICP-MS for 7 consecutive times; (4) Calculation results: MDL = 3 * standard deviation of blank solution. The results are shown in Table 1.

[0023] Spike recovery test (spiking 20ppt): Take a pre-treated 100ml PFA bottle and place it on a balance to peel it. Pour clean 49% HF sample to be tested into the sample bottle in an ultra-clean bench. The balance is not reset to zero. Test on the machine. After the test, accurately weigh the remaining sample weight, calculate the weight of the 1ppb standard solution to be added, use a pipette to draw the standard solution and add it to the remaining sample. Test on the machine again and calculate the spike recovery rate. The results are shown in Table 2.

[0024] Table 1 MDL test results of 13 key elements in hydrofluoric acid

[0025] Table 2 Spike recovery test results

[0026] It can be seen from the above data that the MDLs of the 13 metal elements are all less than 0.5ppt, and the spiked recoveries are between 89.5% and 110.5%, which indicates that the test method provided by the present invention can accurately and stably detect key metal elements at the ppq level in hydrofluoric acid.

Claims

1. A method for testing ppq-level metal content in hydrofluoric acid, characterized in that: The sample bottles were pretreated by immersion, and then inductively coupled plasma mass spectrometry (ICP-MS) was used to detect the ppq level key metal content in hydrofluoric acid using the standard addition method; the key metals were 13 key elements: sodium, magnesium, aluminum, potassium, calcium, cadmium, iron, cobalt, nickel, copper, zinc, silver and lead, and the MDLs of the 13 key elements were all <0.5 ppt.

2. The ppq level metal content testing method according to claim 1, characterized in that: The following steps are involved: A. Sample vial preparation: A1. Place the sample bottle completely in SG-grade HF, soak it in a warm room, take out the sample bottle, shake the bottle, pour out the HF in the bottle, and clean the water seal with ultrapure water; A2. Fill the sample bottle treated in A1 with SG-grade HF, test it on the machine, and get the 0-hour test result; after leaving it for 144 hours, test it again on the machine and get the 144-hour test result; after the test is qualified, wash the sample bottle with ultrapure water, and seal it with ultrapure water until it is put into sampling operation; If the test fails, repeat steps A1 and A2 until the test passes, clean the sample bottle, and seal it with ultrapure water until it is ready for sampling. Among them, the test qualification standard: metal content test result <5ppt; B. Sampling: B1. Fill the sample bottle 2 to 4 parts full with SG grade hydrofluoric acid; B2. With the bottle mouth facing downward, shake the bottle up and down; then rotate it 120°, 240° and 360° in sequence, shaking the bottle after each rotation; B3. With the bottle mouth facing upwards, shake the bottle up and down; then rotate it 120°, 240° and 360° in sequence, shaking the bottle after each rotation; B4. With the bottle mouth facing downwards and the bottle body tilted, pour and rotate until the hydrofluoric acid is emptied; B5. Repeat steps B1 to B4 three times; C. ICP-MS injection: C1. Use the standard addition method to draw a standard curve; C2. The sample to be tested is injected, and the test results of 13 elements including sodium, magnesium, aluminum, potassium, calcium, cadmium, iron, cobalt, nickel, copper, zinc, silver and lead are obtained through the standard curve.

3. The ppq level metal content testing method according to claim 1, characterized in that: The sample injection system, the atomization system, the platinum cone and the rectangular tube of the platinum center tube of the ICP-MS are all made of hydrofluoric acid resistant materials.

4. The ppq level metal content testing method according to claim 2, characterized in that: The shaking time of the bottle is 20 to 40 seconds.

5. The ppq level metal content testing method according to claim 2, characterized in that: The SG grade hydrofluoric acid is 10ppt grade hydrofluoric acid.

6. The ppq level metal content testing method according to claim 2, characterized in that: The step A1 of soaking in a greenhouse specifically involves soaking in a greenhouse at 50-60° C. for 3-4 months.

7. The ppq level metal content testing method according to claim 2, characterized in that: The instrument parameters for the ICP-MS injection test were set as follows: Mode: Cool RF power: 650~850W Sampling depth: 16.5~19.0mm Atomizing gas: 0.75~0.90L / min Compensation gas: 0.80~0.90L / min Extraction lens 1: -70~-80V Extraction lens 2: -5.5V Omega deflection voltage: -46V Omega lens voltage: 1.9V Helium flow rate: 0.5~1.5ml / min Ammonia-helium mixed gas flow rate: 20% Octopole deflection voltage: -6.0~-7.0V Octopole RF: 140~160V Energy discrimination: -4.0~-5.0V Torch horizontal position: -0.6mm Torch vertical position: -1.6mm; The ammonia-helium mixture includes 10% NH3 and 90% He.

8. The ppq level metal content testing method according to claim 2, characterized in that: The instrument parameters for the ICP-MS injection test were set as follows: Mode: Cool RF power: 750W Sampling depth: 18.0mm Atomizing gas: 0.75L / min Make-up gas: 0.90L / min Extraction lens 1: -78.4V Extraction lens 2: -5.5V Omega deflection voltage: -46V Omega lens voltage: 1.9V Helium flow rate: 1.0ml / min Ammonia-helium mixed gas flow rate: 20% Octopole deflection voltage: -7.0V Octopole RF: 150V Energy Discrimination: -5.0V Torch horizontal position: -0.6mm Torch vertical position: -1.6mm; The ammonia-helium mixture includes 10% NH3 and 90% He.

9. The ppq level metal content testing method according to claim 2, characterized in that: The standard curve described in step C1 is established by using 49% HF sample to be tested without dilution as the base, using the standard addition method, and establishing a standard curve with 0 / 10 / 20 / 30 / 50 ppt. The specific establishment steps are as follows: 1) Spike 0ppt: Take a pre-treated 100ml sample bottle and place it on a balance to peel it. Pour clean 49% HF sample into the bottle in an ultra-clean bench. Do not return the balance to zero and test it on the machine. 2) Add 10ppt: After adding 0ppt, accurately weigh the remaining sample weight in the sample bottle, calculate the weight of the 1ppb standard solution to be added, add the standard solution to the remaining sample, and test on the machine; 3) According to the method in step 2), perform 20, 30, and 50 ppt spike tests in turn, and obtain a standard curve based on the test results; the standard curve can only be used if its R value is >0.

995.

10. The ppq level metal content testing method according to claim 2, characterized in that: The sample bottle is a PFA sample bottle; the on-machine test in step A2 is ICP-MS detection.

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