Quantitative analysis method of elements

Abstract

The present invention provides a quantitative analysis method for an element, which does not use a solid standard sample, but quantitatively analyzes an element in a sample gas as LA-ICP-MS. The present invention is a method for quantitatively analyzing an element in a solid sample by introducing a sample gas into an inductively coupled plasma mass spectrometer, the method comprising: directly supplying a standard solution containing a specific element having a known concentration at a flow rate of 3 [mu] L / min or less (standard addition); the respective concentrations of the elements contained in the sample gas generated from the solid sample are measured using the signal intensity obtained by introducing the standard solution from the solution introduction means to the torch unit.

Description

Technical Field

[0001] The present invention relates to a quantitative analysis method of an element, and more particularly to a method for quantitatively analyzing an element of a measurement target from a sample gas containing the measurement target using an inductively coupled plasma mass spectrometer. Background Art

[0002] In recent years, it has become known to use an inductively coupled plasma mass spectrometer (hereinafter sometimes referred to as ICP-MS) in order to analyze metals, organic substances, etc. mixed in substrates such as semiconductor wafers, or to analyze metals, etc. in particles floating in a gas phase. Among such inductively coupled plasma mass spectrometers, one known type of analysis is laser ablation ICP-MS (hereinafter sometimes referred to as LA-ICP-MS), which directly analyzes a micronized sample by irradiating a solid sample with laser light to evaporate the sample and atomize it.

[0003] In this LA-ICP-MS, as a general quantitative analysis method, it is known that, for example, a method of using a glass containing multiple elements or a solid standard sample having a composition close to that of the solid sample to be measured, and calculating the concentration conversion coefficient of each measured element, and performing semi-quantitative analysis on each element of the solid sample is used. However, regarding this solid standard sample, only glass with a specific composition or a composition containing a specific metal is sold on the market, so there are few elements that are guaranteed to be used as solid standard samples. In addition, when the composition of the solid sample to be measured is different from that of the solid standard sample, the amount of particles released by laser irradiation is different, so it is sometimes difficult to perform accurate quantification.

[0004] In addition, among the elements contained in the solid sample, for elements that are not guaranteed as solid standard samples, there is a known method for quantitative determination using a relative sensitivity coefficient. In this case, the detection sensitivity obtained by using a standard solution in a general solution introduction method of ICP-MS is used for correction. Specifically, the relative sensitivity coefficient (A / A') is calculated from the sensitivity (A) of the guaranteed element obtained by irradiating the laser and the sensitivity (A') of the same element obtained by introducing the solution as a standard solution, and is applied to the sensitivity B' of the unguaranteed element to obtain the sensitivity B when irradiating the laser. By this method, the weight of all elements detected when the solid sample is irradiated with the laser is calculated, and the concentration of each element is calculated from the total value of the absolute amount. However, in the method of quantitative determination using this relative sensitivity coefficient, since the introduction of the sample gas generated by the irradiation of the laser and the introduction of the standard solution by the solution introduction are performed in different operations, the plasma conditions are also different, and the problem that all elements cannot have the same coefficient occurs.

[0005] Therefore, for the quantitative analysis of LA-ICP-MS, there has been a proposal for a method of using a standard solution for quantitative analysis instead of a solid standard sample (e.g., Patent Document 1). In this prior art, a standard solution containing a known amount of elements contained in a solid sample is electrothermally vaporized and introduced into the ICP-MS, and the weight of each element per count of the detection signal intensity of all elements is obtained from the detection signal intensity, and the element is used for quantitative analysis of the elements contained in the solid sample. Specifically, 3 to 10 μL of a standard solution is introduced into an electric furnace, and the water is first evaporated at about 100°C, and then the furnace temperature is rapidly raised to several thousand degrees (°C) to evaporate the elements. The evaporated elements are transported and introduced into the ICP-MS via the argon gas introduced into the furnace. As a result, the total amount of the elements contained in the standard solution introduced into the electric furnace is introduced into the plasma of the ICP-MS, and the weight of the elements per count of the detection signal intensity is obtained for the elements contained in the standard solution from the amount of the standard solution introduced and the detection signal intensity.

[0006] In the prior art described in the patent document 1, TOF (TIME OF FLGHT)-ICP-MS is used to analyze multiple elements simultaneously. Compared with the ICP-MS of the quadrupole mass spectrometer, the sensitivity of this TOF-ICP-MS is low, so it is difficult to analyze microparticles. In addition, if the temperature of the electric furnace is raised to thousands of degrees, the argon gas will expand, and there is a tendency to change the detection sensitivity of the ICP-MS. In addition, the element introduced into the ICP-MS by heating the furnace is a few seconds, and it is limited to analyzing a single element in the quadrupole ICP-MS without using TOF-ICP-MS. As a result, it is impossible to analyze all elements in the sample gas. In the method using the electric furnace, it becomes to analyze with the relative sensitivity obtained by the electric furnace. In this case, the detection sensitivity when the sample gas generated by irradiating the laser is introduced is different from the detection sensitivity when the element evaporated by heating the standard solution by the electric furnace is introduced. From this point of view, the prior art of Patent Document 1 is not sufficiently practical for quantitative analysis and is not currently used.

[0007] In addition, quantitative analysis of sample gas containing the object to be measured is difficult in some cases because there are almost no gaseous metal standard samples.

[0008] [Prior art literature]

[0009] [Patent Document]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2018-136190. Summary of the invention

[0011] [Problems to be solved by the invention]

[0012] With the above situation as the background, the purpose of the present invention is to provide an analytical technology that can perform quantitative analysis of elements in a sample gas without using a solid standard sample when performing quantitative analysis on a sample gas like LA-ICP-MS.

[0013] [Methods to solve the problem]

[0014] The inventors of the present application have developed a technology in which, if a standard solution of a known concentration of a specific element is directly supplied to a nebulizer at an extremely low flow rate, almost 100% (total amount) of the standard solution introduced from the spray chamber to the torch can be introduced into the plasma (refer to patent document; International Publication No. WO 2020 / 027345), and it was found that by utilizing this technology, it is possible to perform quantitative analysis of elements in the sample gas without using solid standard samples, which led to the present invention.

[0015] The present invention is a quantitative analysis method of elements, which uses an inductively coupled plasma mass analysis device.

[0016] The inductively coupled plasma mass spectrometer comprises:

[0017] a vaporized sample introduction section for introducing a sample gas generated by combining a laser ablation device for irradiating a solid sample to be measured with laser light to vaporize and atomize the sample, and a gas replacement device for replacing a gas component of a gas containing microparticles released by laser ablation with argon gas, or a sample gas composed of a gas containing the sample to be measured;

[0018] The torch forms plasma to ionize the sample;

[0019] An interface part, used for obtaining ions from the plasma;

[0020] Mass analysis unit, separating ions; and

[0021] A detection unit for detecting the separated ions;

[0022] The inductively coupled plasma mass analyzer is provided with a standard solution introduction device, which is composed of the following units:

[0023] A storage unit that stores standard solutions containing known concentrations of specific elements; and

[0024] A solution introduction unit, comprising a syringe pump and a standard solution spray chamber, wherein the syringe pump sucks and discharges the standard solution, and the standard solution spray chamber is combined with a standard solution nebulizer, and the standard solution nebulizer is supplied with the standard solution;

[0025] The inductively coupled plasma mass spectrometer is provided with a standard solution introduction path connected to a flow path connecting a gasified sample introduction part and a torch part, and the standard solution introduction path is used to introduce a standard solution flowing out of a standard solution spray chamber;

[0026] The standard solution contains all the elements present in the solid sample or gas containing the object of measurement as a specific element with a known concentration;

[0027] The quantitative analysis method for this element consists of the following steps:

[0028] Step 1, after detecting the device background signal intensity in a state where only argon gas is introduced, directly supplying a standard solution to a nebulizer for a standard solution at a flow rate of 3 μL / min or less in a state where argon gas has been introduced, thereby introducing the standard solution from a solution introduction unit into a torch, detecting the standard solution signal intensity obtained by a detector for all elements contained in the standard solution, subtracting the device background signal intensity of each element from the detected standard solution signal intensity of each element to calculate the specific element standard solution signal intensity respectively, and calculating the standard solution sensitivity value as the specific element weight per count of the specific element standard solution signal intensity for all elements contained in the standard solution based on the specific element standard solution signal intensity and the introduction amount of the specific element of the introduced standard solution, and the absolute amount of the device background standard solution calculated from the device background signal intensity and the standard solution sensitivity value; and

[0029] The second step is to directly supply the standard solution to the nebulizer for the standard solution at a flow rate of 3 μL / min or less in the state where the sample gas has been introduced, after detecting the signal intensity of the sample gas in the state where only the sample gas is introduced, thereby introducing the standard solution from the solution introduction unit into the torch part, detecting the mixed signal intensity obtained by the detector for all elements contained in the sample gas, subtracting the sample gas signal intensity of each element from the detected mixed signal intensity of each element to calculate the signal intensity of the specific element mixed standard solution respectively, and calculating the mixed standard solution sensitivity value as the specific element weight per count of the signal intensity of the specific element mixed standard solution for all elements contained in the sample gas based on the signal intensity of the specific element mixed standard solution and the introduction amount of the specific element of the introduced standard solution, and calculating the absolute amount of the specific element in the sample gas calculated from the sample gas signal intensity and the mixed standard solution sensitivity value;

[0030] For all elements contained in the sample gas, the absolute amount of the sample gas specific element of each element contained in the sample gas obtained in the second step is subtracted from the absolute amount of the device background standard solution of each element obtained in the first step to calculate the absolute amount of the sample gas specific element contained in the sample gas. The concentrations of the elements contained in the sample gas are measured from the sum of the absolute amounts of the sample gas specific elements of all elements contained in the sample gas and the absolute amount of the sample gas specific elements of each element.

[0031] In the present invention, the standard solution is directly supplied to the standard solution atomizer at a flow rate of less than 3 μL / min, and the standard solution is introduced from the solution introduction unit into the torch. In this case, the introduced standard solution is 100% (total amount) introduced into the plasma. This has been confirmed by the following 4 verifications (refer to International Publication No. WO 2020 / 027345). Verification 1: Even if the standard solution spray chamber is heated and the temperature is changed, the standard solution sensitivity value of the specific element weight per count of the standard solution signal intensity does not change. Verification 2: The sensitivity value obtained from Au metal microparticles of known particle size is almost the same as the standard solution sensitivity value. Verification 3: When the introduction amount of the standard solution is changed, the signal intensity will change linearly as long as the flow rate is up to 3 μL / min. If the flow rate exceeds 3 μL / min, a tendency of decreasing signal intensity will be observed, and it is confirmed that the standard solution begins to be captured in the standard solution spray chamber. Verification 4: Three nebulizers of the same type were used as nebulizers for standard solutions and the sensitivity values ​​of the standard solutions were compared. As a result, the relative standard deviation was within 1%.

[0032] In the present invention, for the standard solution, all elements contained in the solid sample containing the measurement object or the gas containing the measurement object are used as specific elements of known concentration. For such a standard solution, commercially available standard solutions can be mixed for use. For the elements contained in the mixed standard solution, for example, there are Al, As, Sb, Ba, B, Bi, Cd, Ca, Cs, Cr, Co, Cu, Ga, Ge, Fe, Pb, Li, Mg, Mn, Mo, Ni, P, K, Rb, Se, Si, Ag, Na, Sr, Sn, Ti, W, U, V, Zn, Zr, Au, Ir, Pd, Pt, Rh, Ru, Te, Hf, Sb, Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Sc, Tb, Tm, Yb, Y, etc.

[0033] In the present invention, first, in step 1, the device background noise of the CP-MS used is specified. That is, for all elements contained in the standard solution, the absolute amount of the device background standard solution in the state where only argon gas is introduced is calculated. Secondly, in step 2, for all elements contained in the sample gas, the absolute amount of the specific element in the sample gas is calculated. Then, for all elements contained in the sample gas, the absolute amount of the device background standard solution of each element obtained in step 1 is subtracted from the absolute amount of the sample gas specific element of each element contained in the sample gas obtained in step 2, and the absolute amount of the specific element contained in the sample gas is calculated. The sum of all elements containing the absolute amount of the specific element in the sample gas, such as the total amount of microparticles evaporated from the solid sample by laser irradiation and detected by ICP-MS, can be used to calculate the concentration of each element in the sample gas from the sum of the absolute amount of the specific element in the sample gas and the absolute amount of the specific element in the sample gas of each element. That is. The concentration of each element is the concentration of each element contained in fine particles evaporated from the solid sample by irradiation with laser light, and is the concentration of each element in the solid sample.

[0034] In the present invention, when the composition of a sample gas composed of a solid sample to be measured or a gas containing the sample gas to be measured contains an unmeasurable element that cannot be analyzed by an inductively coupled plasma mass spectrometer at a specific ratio a and contains a measurable element as a main known component at a ratio (1-a), as a standard solution, a specific element containing all elements contained in the sample gas composed of the solid sample to be measured or the sample gas containing the sample gas to be measured, except for the unmeasurable element, is used as a known concentration, and a concentration of the measurable element contained in the sample gas is determined. After calculating the absolute amount of specific elements in the sample gas from all elements detected, calculate the total absolute amounts of specific elements in the sample gas with main known components for the main known components, divide the total absolute amounts of specific elements in the sample gas with main known components by (1-a), and calculate the total absolute amounts of specific elements in the sample gas with 100% main known components. The individual concentrations of the elements contained in the sample gas can be measured from the total absolute amounts of specific elements in the sample gas with 100% main known components and the absolute amounts of specific elements in the sample gas of each element.

[0035] For example, when SiC or GaN is selected as a solid sample, the composition of the sample gas is changed to contain C (carbon) or N (nitrogen) and other unmeasurable elements that cannot be analyzed by the inductively coupled plasma mass spectrometer at a specific ratio a, and contain Si or Ga and other measurable main known component elements at a ratio (1-a). In this case, as for the standard solution, all elements contained in the solid sample of the measurement object or the sample gas containing the measurement object, except for the unmeasurable elements, are used as the specific elements with known concentrations, and the above-mentioned first and second steps are performed. Then, the absolute amount of the specific element contained in the sample gas is calculated for the measurable elements, and the absolute amount of the specific element contained in the sample gas related to the main known component element is extracted and summed up to calculate the total absolute amount of the specific element contained in the sample gas with the main known component. And, the total absolute amount of the specific element contained in the sample gas with the main known component is divided by (1-a), and the total absolute amount of the specific element contained in the sample gas with the main known component of 100% is calculated. The individual concentrations of the elements contained in the sample gas can be measured from the sum of the absolute amounts of the specific elements contained in the 100% main known component sample gas and the absolute amounts of the specific elements contained in the sample gas of each element other than the main known component element.

[0036] In the present invention, the signal strength detection is performed in the state of introducing argon gas in the first step, and the signal strength detection is performed in the state of introducing sample gas in the second step, so the detection sensitivity in each step is the same. Therefore, even if the sensitivity changes, correction can be made, and the concentration of each element in the sample gas can be accurately measured.

[0037] [Effects of the invention]

[0038] According to the present invention, it is possible to quantitatively analyze elements in a sample gas like LA-ICP-MS without using a solid standard sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of an inductively coupled plasma mass spectrometer for analyzing sample gas. DETAILED DESCRIPTION

[0040] Figure 1 A schematic diagram showing an inductively coupled plasma-mass spectrometer according to this embodiment. Figure 1The ICP-MS (Model 8900 manufactured by Agilent Technologies, Inc.) shown in the figure is provided with: a gasification sample introduction part 101; a torch part 102 for forming plasma to ionize the sample; an interface part 103 for obtaining ions from the plasma; a mass spectrometer part 104 for separating the ions; and a detection part 105 for detecting the separated ions. In addition, the ICP-MS is connected to a standard solution introduction device 2. The standard solution introduction device 2 is composed of: a standard solution storage container 201 for storing the standard solution; a syringe pump 202 for sucking and discharging the standard solution; a standard solution nebulizer 203 for supplying the standard solution; and a standard solution spray chamber 204. In addition, a waste container 205 for waste is also provided. The standard solution spray chamber 204 is connected to a standard solution introduction path 206 for introducing the outflowing standard solution into the torch part 102. In addition, the syringe pump 202 is used with a performance of being able to control a flow rate of 0.1 to 99.0 μL / min. The control flow rate of this injection pump is obtained by calculating the physical running amount of the ball screw used in the syringe constituting the injection pump. In addition, a gas displacer 301 is configured. This gas displacer 301 replaces the gas component of the sample gas containing the measurement object with argon gas. In addition, the gas displacer 301 is connected to the gasification sample introduction part 101 via the flow path 110. In addition, a laser ablation device 302 is connected to the gas displacer 301. This gas displacer 301 replaces the air component containing the microparticles released from the laser ablation device 302 with argon gas, and supplies the sample gas to the gasification sample introduction part 101 through the flow path 110. Under dry plasma conditions such as LA-ICP-MS, when a trace amount of solution is introduced from the standard solution introduction device 2, the plasma conditions sometimes change and the sensitivity of the ICP-MS also changes. In this case, if two standard solution introduction devices 2 are combined, the discharge volumes of the two devices are fixed at 3 μL / min, and the ratio of the two syringes is changed, it is effective to prepare a calibration curve.

[0041] Next, the quantitative analysis of elements of solid samples is described. Standard solutions used for analysis can be used with commercially available standard solutions. For example, if three ICP-MS universal mixed standard solutions (manufactured by SPEX, USA) XSTC-622, XSTC-7, and XSTC-1 are mixed, a standard solution containing 59 elements can be prepared.

[0042] In this embodiment, the quantitative analysis of elements is described by taking the case where a solid sample contains 26 elements as the measurement object as an example. The 26 elements of the measurement object are marked with letters A, B, C, D ... Z. The introduction amount of the standard solution when it is introduced at 3μL / min or less is set to N (ag / sec). The introduction amount of the standard solution of this introduction amount N is less than 3μL / min, so by directly supplying it to the atomizer for the standard solution, and from the spray chamber 204 for the standard solution through the standard solution introduction path 206 and introduced into the torch part 102, the introduced standard solution is 100% (total amount) introduced into the plasma.

[0043] First, in step 1, the device background signal intensity (Count / sec) in a state where only argon gas is introduced is detected. The detected device background signal intensity (Count / sec) for element A, element B, element C, element D ... element Z is expressed in the following manner.

[0044] Element A: A_Ar_BL

[0045] Element B: B_Ar_BL

[0046] Element C; C_Ar_BL

[0047] Element C; C_Ar_BL

[0048] ·

[0049] ·

[0050] ·

[0051] Element Z; Z_Ar_BL

[0052] After that, with argon gas introduced, the standard solution is directly supplied to the standard solution nebulizer at a flow rate of N (ag / sec) to detect the signal intensity (Count / sec) of the standard solution obtained by the detector. For element A, element B, element C, element D..., the detected signal intensity (Count / sec) of the standard solution is listed as follows.

[0053] Element A: A_Ar_STD

[0054] Element B: B_Ar_STD

[0055] Element C; C_Ar_STD

[0056] Element D; D_Ar_STD

[0057] ·

[0058] ·

[0059] ·

[0060] Element Z; Z_Ar_STD

[0061] The device background signal intensity of each element is subtracted from the detected signal intensity of the standard solution of each element to calculate the signal intensity of the specific element standard solution. Based on the signal intensity of the specific element standard solution and the amount of the introduced standard solution, the standard solution sensitivity value as the specific element weight per count of the signal intensity of the specific element standard solution is obtained. The standard solution sensitivity values ​​(ag / count) for element A, element B, element C, element D...element Z are listed as shown in the following notation.

[0062] Element A: A_Ar_S=N / (A_Ar_STD-A_Ar_BL)

[0063] Element B: B_Ar_S=N / (B_Ar_STD-B_Ar_BL)

[0064] Element C; C_Ar_S=N / (C_Ar_STD-C_Ar_BL)

[0065] Element D; D_Ar_S=N / (D_Ar_STD-D_Ar_BL)

[0066] ·

[0067] ·

[0068] ·

[0069] Element Z; Z_Ar_S=N / (Z_Ar_STD-Z_Ar_BL)

[0070] The absolute amount (ag) of the device background standard solution is calculated from the device background signal intensity of each element and the sensitivity value of the standard solution obtained above. The absolute amount (ag) of the device background standard solution of element A, element B, element C, element D ... element Z is listed as follows.

[0071] Element A: A_Ar=A_Ar_BL×A_Ar_S

[0072] Element B: B_Ar=B_Ar_BL×B_Ar_S

[0073] Element C; C_Ar=C_Ar_BL×C_Ar_S

[0074] Element D; D_Ar=D_Ar_BL×D_Ar_S

[0075] ·

[0076] ·

[0077] ·

[0078] Element Z; Z_Ar=Z_Ar_BL×Z_Ar_S

[0079] Next, in step 2, the sample gas signal intensity (Count / sec) is detected in a state where only the sample gas is introduced, the sample gas being the gas component containing the microparticles released from the laser ablation device 302 replaced with argon gas. The detected sample gas signal intensity (Count / sec) for element A, element B, element C, element D ... element Z is listed as shown in the following notation.

[0080] Element A: A_SAM_BL

[0081] Element B: B_SAM_BL

[0082] Element C; C_SAM_BL

[0083] Element C: C_SAM_BL

[0084] ·

[0085] ·

[0086] ·

[0087] Element Z; Z_SAM_BL

[0088] After that, with the sample gas introduced, the standard solution is directly supplied to the standard solution nebulizer at a flow rate of N (ag / sec) so that the standard solution introduction amount becomes N (ag / sec), and the mixed signal intensity (Count / sec) obtained by the detector is detected. For element A, element B, element C, element D ... element Z, the detected mixed signal intensity (Count / sec) is listed as follows.

[0089] Element A: A_SAM_STD

[0090] Element B: B_SAM_STD

[0091] Element C; C_SAM_STD

[0092] Element D; D_SAM_STD

[0093] ·

[0094] ·

[0095] ·

[0096] Element Z; Z_SAM_STD

[0097] The signal intensity of the sample gas of each element is subtracted from the mixed signal intensity of each element detected, and the signal intensity of the mixed standard solution of the specific element is calculated respectively. According to the signal intensity of the mixed standard solution of the specific element and the amount of the introduced standard solution, the sensitivity value of the mixed standard solution of the specific element weight per count of the signal intensity of the mixed standard solution of the specific element is calculated. The sensitivity values ​​(ag / count) of the mixed standard solution of element A, element B, element C, element D...element Z are listed as shown in the following symbols.

[0098] Element A: A_SAM_S=N / (A_SAM_STD-A_SAM_BL)

[0099] Element B: B_SAM_S=N / (B_SAM_STD-B_SAM_BL)

[0100] Element C; C_SAM_S=N / (C_SAM_STD-C_SAM_BL)

[0101] Element D; D_SAM_S=N / (D_SAM_STD-D_SAM_BL)

[0102] ·

[0103] ·

[0104] ·

[0105] Element Z; Z_SAM_S=N / (Z_SAM_STD-Z_SAM_BL)

[0106] The sample gas specific element absolute amount (ag) is calculated from the sample gas signal intensity of each element and the mixed standard solution sensitivity value obtained above. The sample gas specific element absolute amounts (ag) of element A, element B, element C, element D...element Z are listed as follows.

[0107] Element A: A_SAM=A_SAM_BL×A_SAM_S

[0108] Element B: B_SAM=B_SAM_BL×B_SAM_S

[0109] Element C; C_SAM=C_SAM_BL×C_SAM_S

[0110] Element D; D_SAM=D_SAM_BL×D_SAM_S

[0111] ·

[0112] ·

[0113] ·

[0114] Element Z; Z_SAM=Z_SAM_BL×Z_SAM_S

[0115] The absolute amount of the device background standard solution of each element obtained in step 1 is subtracted from the absolute amount of the sample gas specific element of each element contained in the sample gas obtained in step 2, and the absolute amount of the specific element contained in the sample gas (A", B", C", D"...Z") of each element contained in the sample gas is calculated. The absolute amounts of specific elements (ag) contained in the sample gas of element A, element B, element C, element D...element Z are listed as shown in the following notations.

[0116] Element A:A”=A_SAM-A_Ar

[0117] Element B: B" = B_SAM-B_Ar

[0118] Element C; C" = C_SAM-C_Ar

[0119] Element D; D" = D_SAM - D_Ar

[0120] ·

[0121] ·

[0122] ·

[0123] Element Z; Z" = Z_SAM-Z_Ar

[0124] The absolute amounts of the specific elements contained in the sample gas of all the elements contained in the sample gas obtained above are summed up, and the total amount of the elements contained in the sample gas to be measured is calculated. Then, the concentration of each element in the sample gas can be calculated by summing up the absolute amounts of the specific elements contained in the sample gas and the absolute amounts of the specific elements contained in the sample gas of each element. The element concentrations in the sample gas of element A, element B, element C, element D...element D are as follows.

[0125] Concentration of element A: A” / (A”+B”+C”+D”…Z”)

[0126] Concentration of element B: B” / (A”+B”+C”+D”…Z”)

[0127] Element C concentration: C” / (A”+B”+C”+D”…Z”)

[0128] Element D concentration: D” / (A”+B”+C”+D”…Z”)

[0129] ·

[0130] ·

[0131] ·

[0132] Element Z concentration: Z” / (A”+B”+C”+D”…Z”)

[0133] Next, the case where an unmeasurable element such as C (carbon) or N (nitrogen) that cannot be analyzed by an inductively coupled plasma mass spectrometer is contained in a specific ratio a in the sample gas is described. The unmeasurable element is set to Z, its specific ratio is set to a, and the measurable and main known component elements are set to X and Y, and their content ratios are set to (1-a). In this case, elements A, B, C to W other than elements X, Y, and Z become measurable trace impurities. In addition, as for the standard solution, a known concentration of measurable elements A, B, C...Y is used in addition to element Z.

[0134] If the above-mentioned first and second steps are performed, the data of each of the elements A, B, C ... Y other than the unmeasurable element Z can be obtained. In addition, the absolute amount of the specific element contained in the sample gas for the measurable elements A to Y is obtained, and the absolute amount of the specific element contained in the sample gas related to the main known component elements (X, Y) is extracted and summed up to obtain the total absolute amount of the specific element contained in the sample gas with the main known components.

[0135] Element X; X" = X_SAM - X_BL

[0136] Element Y; Y" = Y_SAM - Y_BL

[0137] Element (X, Y); (X+Y)”=X_SAM-X_BL+Y_SAM-Y_BL

[0138] In addition, the total absolute amount of specific elements contained in the main known component sample gas (X+Y)" is divided by (1-a), and the total absolute amount of specific elements contained in the 100% main known component sample gas is calculated based on this. From the total absolute amount of specific elements contained in the 100% main known component sample gas and the absolute amount of specific elements contained in the sample gas of each element (A to W) other than the main known component element, the concentrations of the elements contained in the sample gas can be calculated. The element concentration of elements A to W is the impurity concentration contained in the sample gas, and as long as the sample gas is generated from a solid sample, it is the impurity concentration in the solid sample.

[0139] Concentration of element A: A” / ((X+Y)” / (1-a))

[0140] Element B concentration: B” / ((X+Y)” / (1-a))

[0141] Element C concentration: C” / ((X+Y)” / (1-a))

[0142] Element D concentration: D” / ((X+Y)” / (1-a))

[0143] ·

[0144] ·

[0145] ·

[0146] Element W concentration: W” / ((X+Y)” / (1-a))

[0147] Next, the experimental results of quantitative analysis of impurities in solid samples of known impurity elements by LA-ICP-MS are described based on examples. The ICP-MS used is Model 8900 manufactured by Agilent Technologies, Inc.

[0148] [Example 1]

[0149] In Example 1, Si wafers were used as individual samples. The constituent elements of this solid sample include Si as the base material and four impurities of Na, Al, Mg, and Fe. In addition, the standard solution used in the quantitative analysis of this Example 1 has a Si concentration of 1 ppm and a concentration of 10 ppb for each element of Na, Al, Mg, and Fe. In addition, the device conditions of the ICP-MS are an argon gas flow rate of 1 L / min and a high-frequency output of 1300 W.

[0150] First, in the first step, the background signal intensity (Count / sec) of the device in the state where only argon gas is introduced is detected, and the standard solution is directly supplied to the standard solution nebulizer at a flow rate of 1μL / min in the state where argon gas has been introduced to detect the signal intensity (Count / sec) of the standard solution, and the sensitivity value of the standard solution as the weight of the specific element per count of the signal intensity of the specific element standard solution is obtained, and the absolute amount of the device background standard solution (ag) is measured. When the standard solution is introduced, the gas flow rate of the standard solution nebulizer is 0.3L / min. When the standard solution is introduced at a flow rate of 1μL / min, since the Si concentration of the standard solution is 1ppm, the Si introduction amount is 166,666,667ag / sec, and since the element concentrations of Na, Al, Mg, and Fe in the standard solution are 10ppb, the introduction amount of each element is 166,667ag / sec. The standard solution introduced with this introduction amount will be introduced into the plasma as 100% (total amount). The measurement results of the first step are shown in Table 1.

[0151] [Table 1]

[0152]

[0153] Then, the second step was performed using a sample gas in which the gas component of the gas containing the particles released from the Si wafer of the individual sample by the laser ablation was replaced with argon gas. The conditions of the laser ablation were a laser frequency of 257 nm, a laser irradiation frequency of 10,000 Hz, and a laser beam diameter of 13 μm.

[0154] In this second step, the signal intensity (Count / sec) of the sample gas in the state where only the sample gas containing the microparticles released from the laser ablation device is introduced and replaced with argon gas is detected, and the mixed signal intensity (Count / sec) obtained by directly supplying the standard solution to the standard solution atomizer at a flow rate of 1 μL / min while the sample gas is introduced is detected, and the mixed standard solution sensitivity value as the specific element weight per count of the signal intensity of the specific element mixed standard solution is obtained, and the absolute amount (ag) of the specific element in the sample gas is measured. The results are shown in Table 2.

[0155] [Table 2]

[0156]

[0157] The impurity concentration in the individual sample Si wafer was calculated from the absolute amount of the device background standard solution obtained in step 1 (Table 1) and the absolute amount of the specific element in the sample gas obtained in step 2 (Table 2). The results are shown in Table 3.

[0158] [Table 3]

[0159]

[0160] [Example 2]

[0161] In this Example 2, the results of analysis using Si-C wafers as individual samples are described. In this solid sample Si-C wafer, 50% of the solid sample is Si (main known component element) and 50% is C (unmeasurable element), and the impurities are 4 types of Na, Al, Mg, and Fe.

[0162] In the quantitative analysis of Example 2, the composition of the standard solution, the conditions of the ICP-MS apparatus, and the conditions of the laser ablation device are the same as those of Example 1. In addition, the first step in Example 2 is the same as the first step in Example 1. In addition, regarding C (carbon), it is contained as an impurity in the argon gas that generates the plasma of ICP-MS, and since the background is high and the ionization potential of carbon is high, the ionization efficiency in the plasma is not preferred, so it is excluded as an element to be analyzed.

[0163] In the second step of Example 2, the signal intensity (Count / sec) of the sample gas in the state where only the sample gas containing the microparticles released from the laser ablation device is introduced and replaced with argon gas is detected, and the mixed signal intensity (Count / sec) obtained by directly supplying the standard solution to the standard solution atomizer at a flow rate of 1 μL / min in the state where the sample gas has been introduced is detected, and the mixed standard solution sensitivity value as the specific element weight per count of the signal intensity of the specific element mixed standard solution is obtained, and the absolute amount (ag) of the specific element in the sample gas is measured. The results are shown in Table 4.

[0164] [Table 4]

[0165]

[0166] The impurity concentration in the individual sample Si-C wafer is calculated from the absolute amount of the device background standard solution obtained in step 1 (refer to Table 1 of Example 1) and the absolute amount of specific elements in the sample gas obtained in step 2 (Table 4), and the results are shown in Table 5.

[0167] [Table 5]

[0168]

[0169]

[0170] In the solid sample of this Example 2, since 50% of the individual sample is Si, the absolute amount of Si (175,456,887ag) in Table 5 corresponds to the 50% Si concentration of the solid sample, so the absolute amount in 100% of the Si-C wafer is 175,456,887ag / 0.5=350,913,773ag. The impurity concentration in the Si-C wafer shown in Table 5 is the result of dividing the absolute amount of each impurity element by the absolute amount of 100% of the Si-C wafer (350,913,773ag).

[0171] As shown in Tables 3 and 5, it can be seen that in the quantitative analysis of the impurity concentration of the individual sample, high-precision quantitative analysis can be performed without using an individual standard sample.

[0172] Description of Reference Numerals

[0173] 1 ICP-MS (main body)

[0174] 11 Gasification sample introduction section

[0175] 102 Torch

[0176] 103 Interface

[0177] 104 Quality Analysis Department

[0178] 105 Detector

[0179] 110 flow path

[0180] 2 Standard solution introduction device

[0181] 201 Standard solution storage container

[0182] 202 Syringe Pump

[0183] 203 Nebulizer for standard solution

[0184] 204 Spray chamber for standard solution

[0185] 205 Waste Container

[0186] 206 Standard solution introduction path

[0187] 301 Gas Displacer

[0188] 302 Laser ablation device.

Claims

1. A method for quantitative analysis of elements using an inductively coupled plasma mass spectrometer. in, The inductively coupled plasma mass spectrometer has: a vaporized sample introduction section for introducing a sample gas generated by combining a laser ablation device for irradiating a solid sample of the measurement object with laser light to vaporize and atomize the sample gas, or a sample gas composed of a gas containing a measurement object, wherein the laser ablation device irradiates a solid sample of the measurement object with laser light to vaporize and atomize the sample, and the gas displacer replaces a gas component of the gas containing the atomized particles released by the laser ablation with argon gas; The torch forms plasma to ionize the sample; An interface part, used for obtaining ions from the plasma; Mass analysis unit, separating ions; and A detection unit for detecting the separated ions; The inductively coupled plasma mass analyzer is provided with a standard solution introduction device, which is composed of the following units: A storage unit that stores standard solutions containing known concentrations of specific elements; and A solution introduction unit, comprising a syringe pump and a standard solution spray chamber, wherein the syringe pump sucks and discharges the standard solution, and the standard solution spray chamber is combined with a standard solution nebulizer, and the standard solution nebulizer is supplied with the standard solution; The inductively coupled plasma mass spectrometer is provided with a standard solution introduction path connected to a flow path connecting a vaporized sample introduction part and a torch part, and the standard solution introduction path is used to introduce a standard solution flowing out of a standard solution spray chamber; The standard solution contains all the elements present in the solid sample or gas containing the object of measurement as a specific element of known concentration; The quantitative analysis method for this element consists of the following steps: Step 1, after detecting the device background signal intensity in a state where only argon gas is introduced, directly supplying a standard solution to a nebulizer for a standard solution at a flow rate of 3 μL / min or less in a state where argon gas has been introduced, thereby introducing the standard solution from a solution introduction unit into a torch, detecting the standard solution signal intensity obtained by a detector for all elements contained in the standard solution, subtracting the device background signal intensity of each element from the detected standard solution signal intensity of each element to calculate the specific element standard solution signal intensity respectively, and calculating the standard solution sensitivity value as the specific element weight per count of the specific element standard solution signal intensity for all elements contained in the standard solution based on the specific element standard solution signal intensity and the introduction amount of the specific element of the introduced standard solution, and the absolute amount of the device background standard solution calculated from the device background signal intensity and the standard solution sensitivity value; and The second step is to directly supply the standard solution to the nebulizer for the standard solution at a flow rate of 3 μL / min or less in the state where the sample gas has been introduced, after detecting the signal intensity of the sample gas in the state where only the sample gas is introduced, thereby introducing the standard solution from the solution introduction unit into the torch, detecting the mixed signal intensity obtained by the detector for all elements contained in the sample gas, subtracting the sample gas signal intensity of each element from the detected mixed signal intensity of each element to calculate the signal intensity of the specific element mixed standard solution respectively, and calculating the mixed standard solution sensitivity value as the specific element weight per count of the signal intensity of the specific element mixed standard solution for all elements contained in the sample gas based on the signal intensity of the specific element mixed standard solution and the introduction amount of the specific element of the introduced standard solution, and calculating the absolute amount of the specific element in the sample gas calculated from the sample gas signal intensity and the mixed standard solution sensitivity value; For all elements contained in the sample gas, the absolute amount of the sample gas specific element contained in the sample gas obtained in the second step is subtracted from the absolute amount of the device background standard solution of each element obtained in the first step to calculate the absolute amount of the sample gas specific element contained in the sample gas. Each concentration of the element contained in the sample gas is measured from the total absolute amount of the specific element contained in the sample gas of all elements contained in the sample gas and the absolute amount of the specific element contained in the sample gas of each element.

2. The method for quantitative analysis of elements according to claim 1, wherein: When the composition of the sample gas composed of the solid sample to be measured or the gas containing the sample to be measured contains an unmeasurable element that cannot be analyzed by the inductively coupled plasma mass spectrometer at a specific ratio a, and contains a measurable and main known component element at a ratio (1-a), The standard solution contains all elements contained in the solid sample to be measured or the sample gas containing the gas to be measured, except for the elements that cannot be measured, as specific elements with known concentrations. After calculating the absolute amount of a specific element contained in the sample gas for all measurable elements contained in the sample gas, Calculate the absolute amount of specific elements contained in the main known component sample gas with respect to the main known component elements. Divide the absolute amount of specific elements contained in the main known component sample gas by (1-a) to calculate the absolute amount of specific elements contained in the main known component sample gas of 100%, The concentrations of the elements contained in the sample gas are measured from the sum of the absolute amounts of the specific elements contained in the sample gas containing 100% of the main known component and the absolute amounts of the specific elements contained in the sample gas containing each element other than the main known component.

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