Quantitative analysis of elements

Abstract

The present invention provides a method for quantitatively analyzing elements within a sample gas such as LA-ICP-MS without using a solid standard sample. The present invention is a method in which a sample gas is introduced into an inductively coupled plasma mass spectrometer and the elements of a solid sample are quantitatively analyzed, wherein the method is characterized in that a standard solution containing specific elements at known concentrations is directly supplied (by standard addition) at a flow rate of 3 μL / min or less, and the concentrations of the elements included in the sample gas generated from the solid sample are thereby measured using a signal strength obtained by introducing the standard solution to a torch section from a solution introduction means.

Description

[Technical Field]

[0001] The present invention relates to a method for quantitatively analyzing an element, and more particularly to a method for quantitatively analyzing an element to be measured from a sample gas containing the element to be measured using an inductively coupled plasma mass spectrometer. [Background technology]

[0002] In recent years, it has become common to use inductively coupled plasma mass spectrometry (hereinafter sometimes abbreviated as ICP-MS) to analyze metals, organic substances, etc. contaminated in substrates such as semiconductor wafers, and metals in particles suspended in the gas phase. In this inductively coupled plasma mass spectrometry, a type of analysis known as laser ablation ICP-MS (hereinafter sometimes abbreviated as LA-ICP-MS) is known, in which a solid sample is irradiated with laser light to vaporize and atomize the sample, and the atomized sample is then directly analyzed.

[0003] A common quantitative analysis method for LA-ICP-MS is to calculate the concentration conversion factor for each element in a solid sample using a multi-element glass or a solid standard sample with a composition similar to that of the target solid sample, and then perform semi-quantitative analysis of each element in the solid sample. However, since only glass of a specific composition or a composition containing a specific metal is commercially available, there are few elements that are guaranteed to be included in the solid standard sample. Furthermore, if the composition of the target solid sample and the solid standard sample are not the same, the amount of particles released by laser irradiation will differ, making accurate quantitation difficult.

[0004] For elements contained in solid samples that are not certified as solid standard samples, a method using relative response factors is known. In this case, the detection sensitivity obtained using a standard solution in the typical solution introduction method for ICP-MS is used for correction. Specifically, the relative response factor (A / A') is calculated from the sensitivity (A) of the certified element obtained by laser irradiation and the sensitivity (A') of the same element obtained by solution introduction using a standard solution. This is then applied to the sensitivity (B') of the uncertified element to determine the sensitivity (B) when irradiated with laser light. This method calculates the weights of all elements detected when the solid sample is irradiated with laser light, and the concentration of each element is calculated from the sum of the absolute amounts. However, this method of quantification using relative response factors involves separate operations for the introduction of the sample gas generated by laser irradiation and the introduction of the standard solution via solution introduction, which results in different plasma conditions and the problem of not obtaining the same coefficients for all elements.

[0005] For this reason, a method for quantitative analysis using LA-ICP-MS has been proposed that uses a standard solution rather than a solid standard sample (e.g., Patent Document 1). In this prior art, a standard solution containing known amounts of elements contained in a solid sample is electrically heated and vaporized, and then introduced into an ICP-MS. The detected signal intensity is used to determine the weight of each element per count of the detected signal intensity for all elements, and this is used to quantitatively analyze the elements contained in the solid sample. Specifically, 3 to 10 μL of the standard solution is introduced into an electrically heated furnace, and the water is first evaporated at approximately 100°C. The furnace temperature is then rapidly raised to several thousand degrees (°C) to vaporize the elements. The evaporated elements are transported by argon gas introduced into the furnace and introduced into the ICP-MS. As a result, the entire amount of elements contained in the standard solution introduced into the electrically heated furnace is introduced into the ICP-MS plasma. From the amount of standard solution introduced and the detected signal intensity, the element weight per count of the detected signal intensity for the elements contained in the standard solution can be determined.

[0006] The prior art described in Patent Document 1 uses TOF (Time of Flight)-ICP-MS to simultaneously analyze multiple elements. This TOF-ICP-MS has lower sensitivity than ICP-MS, a quadrupole mass spectrometer, making it difficult to analyze fine particles. Furthermore, when the temperature of an electric furnace is raised to several thousand degrees, argon gas expands, tending to change the detection sensitivity of the ICP-MS. Furthermore, elements introduced into the ICP-MS by heating the furnace take only a few seconds, and quadrupole ICP-MS without TOF-ICP-MS is limited to analyzing a single element. As a result, it is impossible to analyze all elements in a sample gas. Methods using an electric furnace require analysis based on a relative sensitivity to that obtained with the electric furnace. In this case, the detection sensitivity when introducing a sample gas generated by laser irradiation is not the same as the detection sensitivity when introducing elements vaporized by heating a standard solution in an electric furnace. For these reasons, the prior art described in Patent Document 1 is not sufficiently practical for quantitative analysis and is not currently used.

[0007] Furthermore, quantitative analysis of sample gases containing the target metals is difficult because there are almost no standard gaseous metal samples. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-136190 Summary of the Invention [Problem to be solved by the invention]

[0009] In light of the above-mentioned circumstances, the present invention aims to provide an analytical technique that enables quantitative analysis of elements in a sample gas without using a solid standard sample when quantitatively analyzing the sample gas using a method such as LA-ICP-MS. [Means for solving the problem]

[0010] The inventors have developed a technology (see patent document; International Publication No. WO2020 / 027345) that enables a standard solution containing a known concentration of a specific element to be directly supplied to a nebulizer at an extremely low flow rate, so that nearly 100% (the entire amount) of the standard solution introduced from the spray chamber to the torch section can be introduced into the plasma. They discovered that this technology can be used to quantitatively analyze elements in a sample gas without using a solid standard sample, and thus conceived the present invention.

[0011] The present invention provides a method for quantitatively analyzing an element using an inductively coupled plasma mass spectrometer in which a standard solution introducing device is provided, the device comprising: a gasification sample introducing section for introducing a sample gas generated by combining a laser ablation device that irradiates a solid sample to be measured with a laser beam to vaporize and atomize it, or a gas replacing device that replaces gas components of a gas containing fine particles emitted by laser ablation with argon gas, or a sample gas consisting of a gas containing the object to be measured; a torch section that forms a plasma to ionize the sample; an interface section for introducing ions from the plasma; a mass spectrometry section that separates ions; and a detection section that detects the separated ions, the standard solution introducing device comprising: storage means for storing a standard solution containing a known concentration of a specific element; a syringe pump that draws in and discharges the standard solution; and a standard solution spray chamber combined with a standard solution nebulizer to which the standard solution is supplied; and a standard solution introducing path connected to a flow path connecting the gasification sample introducing section and the torch section for introducing the standard solution flowing out from the standard solution spray chamber, the standard solution containing a specific element contained in the solid sample to be measured or the gas containing the object to be measured. The standard solution contains all elements in the sample as specific elements with known concentrations. After detecting the instrument background signal intensity when only argon gas is introduced, the standard solution is introduced into the torch section from the solution introduction means by supplying the standard solution directly to the standard solution nebulizer at a flow rate of 3 μL / min or less while argon gas is being introduced. The standard solution signal intensity obtained from the detector is detected for all elements contained in the standard solution. The specific element standard solution signal intensity is calculated by subtracting the instrument background signal intensity of each element from the standard solution signal intensity of each element detected. a first step of calculating, for all elements contained in the standard solution, a standard solution sensitivity value, which is the weight of a specific element per count of the standard solution signal intensity of a specific element, based on the solution signal intensity and the amount of the specific element introduced in the introduced standard solution, and an absolute amount of the instrument background standard solution calculated from the instrument background signal intensity and the standard solution sensitivity value; and a step of detecting the sample gas signal intensity in a state where only the sample gas has been introduced, and then introducing the standard solution into the torch section from the solution introducing means by directly supplying the standard solution to the standard solution nebulizer at a flow rate of 3 μL / min or less in a state where the sample gas has been introduced.a second step of detecting the mixed signal intensity obtained from the detector for all elements contained in the sample gas, calculating the signal intensity of each specific element mixed standard solution by subtracting the sample gas signal intensity of each element from the mixed signal intensity of each detected element, and calculating the mixed standard solution sensitivity value, which is the weight of the specific element per count of the signal intensity of the specific element mixed standard solution, based on the signal intensity of the specific element mixed standard solution and the amount of the specific element introduced in the standard solution introduced, and 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; calculating the absolute amount of the specific element contained in the sample gas for all elements contained in the sample gas by subtracting the absolute amount of the instrument background standard solution for each element obtained in the first step from the absolute amount of the specific element contained in the sample gas for each element obtained in the second step, and measuring the concentration of each element contained in the sample gas from the total absolute amount of the specific element contained in the sample gas for all elements contained in the sample gas and the absolute amount of the specific element contained in the sample gas for each element.

[0012] In the present invention, the standard solution is introduced into the torch section from the solution introduction means by directly supplying the standard solution to the standard solution nebulizer at a flow rate of 3 μL / min or less. In this case, 100% (the entire amount) of the introduced standard solution is introduced into the plasma. This has been demonstrated by the following four verifications (see International Publication No. WO2020 / 027345). Verification 1: Even when the temperature of the standard solution spray chamber was changed by heating, there was no change in the standard solution sensitivity value, which is the weight of a specific element per count of standard solution signal intensity. Verification 2: The sensitivity value obtained using Au metal microparticles of known particle size was nearly identical to the standard solution sensitivity value. Verification 3: When the amount of standard solution introduced was changed, the signal intensity changed linearly up to a flow rate of 3 μL / min. A tendency for signal intensity to decrease was observed when the flow rate exceeded 3 μL / min, and the phenomenon of the standard solution beginning to be trapped in the standard solution spray chamber was observed. Verification 4: Three nebulizers of the same type were used as nebulizers for the standard solution, and the standard solution sensitivity values ​​were compared. The relative standard deviation was within 1%.

[0013] The present invention uses a standard solution containing all elements present in the solid sample or gas containing the target substance as specific elements at known concentrations. This standard solution can be prepared by mixing commercially available standard solutions. Examples of elements contained in the standard solution obtained by mixing include 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, and Y.

[0014] In the present invention, the instrument background noise of the ICP-MS used is first identified in the first step. That is, the absolute amount of instrument background standard solution when only argon gas is introduced is calculated for all elements contained in the standard solution. Next, in the second step, the absolute amount of specific element in the sample gas is calculated for all elements contained in the sample gas. Then, the absolute amount of specific element contained in the sample gas is calculated for all elements contained in the sample gas by subtracting the absolute amount of instrument background standard solution for each element obtained in the first step from the absolute amount of specific element in the sample gas for each element contained in the sample gas obtained in the second step. The sum of all elements in this absolute amount of specific element contained in the sample gas is, for example, the total amount of particulates evaporated from the solid sample by laser irradiation and detected by ICP-MS. The concentration of each element in the sample gas can be calculated from this total absolute amount of specific element contained in the sample gas and the absolute amount of each element in the sample gas. In other words, the concentration of each element is the concentration of each element contained in the particulates evaporated from the solid sample by laser irradiation, and is the concentration of each element in the solid sample.

[0015] In the present invention, when a sample gas consisting of a solid sample to be measured or a gas containing the sample to be measured contains unmeasurable elements that cannot be analyzed by an inductively coupled plasma mass spectrometer at a specific ratio a, and measurable elements and known major component elements at a ratio (1-a), a standard solution is used that contains all elements contained in the sample gas consisting of the solid sample to be measured or the gas containing the sample to be measured, excluding the unmeasurable elements, as known concentrations of specific elements.The absolute amounts of the specific elements contained in the sample gas are then calculated for all measurable elements contained in the sample gas, and the total absolute amounts of the specific elements contained in the major known component sample gas for the major known component elements are calculated.This total absolute amount of the specific elements contained in the major known component sample gas is then divided by (1-a) to calculate the 100% total absolute amount of the specific elements contained in the major known component sample gas.The concentrations of the elements contained in the sample gas can then be measured from the total absolute amount of the specific elements contained in the 100% major known component sample gas and the absolute amount of each element in the sample gas.

[0016] For example, if a solid sample such as SiC or GaN is used, the sample gas will contain unmeasurable elements, such as C (carbon) and N (nitrogen), at a specific ratio a, which cannot be analyzed by an inductively coupled plasma mass spectrometer, and measurable major known component elements, such as Si and Ga, at a ratio (1-a). In such cases, a standard solution containing all elements, except the unmeasurable elements, present in the sample gas (solid sample or gas containing the target substance) as known concentrations of specific elements is used, and the first and second steps described above are performed. The absolute amounts of the specific elements contained in the sample gas for the measurable elements are then calculated. The absolute amounts of the specific elements contained in the sample gas for the major known component elements are then extracted and summed to determine the total absolute amount of the specific elements contained in the major known component sample gas. This total absolute amount of the specific elements contained in the major known component sample gas is then divided by (1-a) to calculate the 100% total absolute amount of the specific elements contained in the major known component sample gas. The concentration of each element contained in the sample gas can be determined from the total absolute amount of specific elements contained in the 100% major known component sample gas and the absolute amount of specific elements contained in the sample gas for each element other than the major known component elements.

[0017] In the present invention, the signal intensity is detected with argon gas introduced in the first step, and with sample gas introduced in the second step, so the detection sensitivity is the same in each step. Therefore, even if sensitivity changes, they can be corrected, and the concentration of each element in the sample gas can be accurately measured. [Effects of the Invention]

[0018] According to the present invention, quantitative analysis of elements in a sample gas such as LA-ICP-MS is possible without using a solid standard sample. [Brief explanation of the drawings]

[0019] [Figure 1] Schematic diagram of an inductively coupled plasma mass spectrometer for analyzing sample gases. DETAILED DESCRIPTION OF THE INVENTION

[0020] FIG. 1 shows a schematic diagram of an inductively coupled plasma mass spectrometer according to this embodiment. The ICP-MS (Model 8900, manufactured by Agilent Technologies, Inc.) shown in FIG. 1 includes a gasified sample introduction section 101, a torch section 102 that generates plasma and ionizes the sample, an interface section 103 that introduces ions from the plasma, a mass analysis section 104 that separates the ions, and a detection section 105 that detects the separated ions. A standard solution introduction device 2 is connected to the ICP-MS. The standard solution introduction device 2 is composed of a standard solution storage container 201 that stores the standard solution, a syringe pump 202 that draws and discharges the standard solution, a standard solution nebulizer 203 to which the standard solution is supplied, and a standard solution spray chamber 204. A waste container 205 is also provided. A standard solution introduction path 206 is connected to the standard solution spray chamber 204, which guides the standard solution flowing out to the torch section 102. The syringe pump 202 was capable of controlling a flow rate of 0.1 to 99.0 μL / min. The control flow rate of this syringe pump was calculated from the physical operating amount of the ball screw used in the syringe constituting the syringe pump. A gas replacement device 301 was also installed. This gas replacement device 301 replaces the gas components of the sample gas containing the measurement target with argon gas. This gas replacement device 301 is also connected to the gasification sample introduction section 101 via a flow path 110. This gas replacement device 301 is connected to a laser ablation device 302. This gas replacement device 301 replaces the air components, including the fine particles released from the laser ablation device 302, with argon gas, and supplies the sample gas to the gasification sample introduction section 101 through the flow path 110. When a small amount of solution is introduced from the standard solution introduction device 2 under dry plasma conditions such as LA-ICP-MS, the plasma conditions may change, causing fluctuations in the sensitivity of the ICP-MS. In this case, it is effective to combine two standard liquid introducing devices 2, fix the discharge rates of the two devices to 3 μL / min, and vary the ratio of the two syringes to create a calibration curve.

[0021] Next, we will explain the quantitative analysis of elements in solid samples. The standard solutions used for analysis can be commercially available. For example, by mixing three types of ICP-MS general-purpose mixed standard solutions (manufactured by SPEX, USA): XSTC-622, XSTC-7, and XSTC-1, a standard solution containing 59 elements can be prepared.

[0022] In this embodiment, quantitative analysis of elements will be described using an example in which a solid sample contains 26 elements to be measured. The 26 elements to be measured are represented by the letters A, B, C, D,..., Z. The amount of standard solution introduced when introduced at 3 μL / min or less is defined as N (ag / sec). Since this amount of standard solution, N, is introduced at 3 μL / min or less, it is supplied directly to the standard solution nebulizer, passes from the standard solution spray chamber 204 through the standard solution introduction path 206, and is introduced into the torch unit 102, and 100% (total amount) of the introduced standard solution is introduced into the plasma.

[0023] First, in the first step, the instrument background signal intensity (Count / sec) is detected when only argon gas is introduced. The detected instrument background signal intensity (Count / sec) for element A, element B, element C, element D, and element Z is shown in the following notation. Element A: A_Ar_BL Element B:B_Ar_BL Element C;C_Ar_BL Element C;C_Ar_BL · · · Element Z; Z_Ar_BL

[0024] Then, with argon gas introduced, the standard solution is directly supplied to the nebulizer for the standard solution at a flow rate of N (ag / sec), and the signal intensity (counts / sec) of the standard solution obtained from the detector is detected. The detected signal intensities (counts / sec) of the standard solutions for element A, element B, element C, element D, and element Z are shown in the following notation. Element A: A_Ar_STD Element B:B_Ar_STD Element C;C_Ar_STD Element D;D_Ar_STD · · · Element Z; Z_Ar_STD

[0025] The signal intensity of each specific element standard solution is calculated by subtracting the instrument background signal intensity of each element from the standard solution signal intensity of each detected element, and the standard solution sensitivity value, which is the weight of a specific element per 1 count of the specific element standard solution signal intensity, is calculated based on this specific element standard solution signal intensity and the amount of standard solution introduced.The standard solution sensitivity values ​​(ag / count) for element A, element B, element C, element D,...element Z are shown in the following notation. Element A:A_Ar_S=N / (A_Ar_STD - A_Ar_BL) Element B:B_Ar_S=N / (B_Ar_STD - B_Ar_BL) Element C;C_Ar_S=N / (C_Ar_STD - C_Ar_BL) Element D;D_Ar_S=N / (D_Ar_STD - D_Ar_BL) · · · Element Z;Z_Ar_S=N / (Z_Ar_STD - Z_Ar_BL)

[0026] The absolute amount (ag) of the instrument background standard solution is calculated from the instrument background signal intensity of each element and the standard solution sensitivity value obtained above. The absolute amount (ag) of the instrument background standard solution for element A, element B, element C, element D, element Z is shown in the following notation. Element A:A_Ar=A_Ar_BL × A_Ar_S Element B: B_Ar = B_Ar_BL × B_Ar_S Element C;C_Ar=C_Ar_BL × C_Ar_S Element D;D_Ar=D_Ar_BL × D_Ar_S · · · Element Z;Z_Ar=Z_Ar_BL × Z_Ar_S

[0027] Next, in the second step, the signal intensity (count / sec) of the sample gas is detected when only the sample gas in which the gas components of the gas containing the particles emitted from the laser ablation device 302 have been replaced with argon gas is introduced. The detected signal intensities (count / sec) of the sample gas for element A, element B, element C, element D, ..., element Z are shown in the following notation. Element A:A_SAM_BL Element B:B_SAM_BL Element C;C_SAM_BL Element C;C_SAM_BL · · · Element Z;Z_SAM_BL

[0028] Then, while the sample gas is being introduced, the standard solution is directly supplied to the nebulizer for the standard solution at a flow rate of N (ag / sec), and the mixed signal intensity (Count / sec) obtained from the detector is detected. The detected mixed signal intensity (Count / sec) for element A, element B, element C, element D,...element Z is expressed as follows: Element A: A_SAM_STD Element B:B_SAM_STD Element C;C_SAM_STD Element D;D_SAM_STD · · · Element Z;Z_SAM_STD

[0029] The signal intensity of each specific element mixed standard solution is calculated by subtracting the sample gas signal intensity of each element from the mixed signal intensity of each element detected, and the mixed standard solution sensitivity value, which is the weight of a specific element per 1 count of the specific element mixed standard solution signal intensity, is calculated based on this specific element mixed standard solution signal intensity and the amount of standard solution introduced. The mixed standard solution sensitivity values ​​(ag / count) for element A, element B, element C, element D,...element Z are shown in the following notation. Element A:A_SAM_S=N / (A_SAM_STD-A_SAM_BL) Element B:B_SAM_S=N / (B_SAM_STD-B_SAM_BL) Element C;C_SAM_S=N / (C_SAM_STD-C_SAM_BL) Element D;D_SAM_S=N / (D_SAM_STD-D_SAM_BL) · · · Element Z;Z_SAM_S=N / (Z_SAM_STD-Z_SAM_BL)

[0030] The absolute amount (ag) of a specific element in the sample gas is calculated from the signal intensity of each element in the sample gas and the sensitivity value of the mixed standard solution obtained above. The absolute amount (ag) of a specific element in the sample gas for element A, element B, element C, element D, ..., element Z is shown in the following notation. Element A:A_SAM=A_SAM_BL × A_SAM_S Element B:B_SAM=B_SAM_BL × B_SAM_S Element C;C_SAM=C_SAM_BL × C_SAM_S Element D;D_SAM=D_SAM_BL × D_SAM_S · · · Element Z;Z_SAM=Z_SAM_BL × Z_SAM_S

[0031] The absolute amount of the specific element contained in the sample gas (A", B", C", D",...Z") is calculated for each element contained in the sample gas by subtracting the absolute amount of the instrument background standard solution for each element obtained in the first step from the absolute amount of the specific element contained in the sample gas for each element contained in the sample gas obtained in the second step. The absolute amount (ag) of the specific element contained in the sample gas for element A, element B, element C, element D...element Z is expressed as follows. Element A: A” = A_SAM - A_Ar Element B:B”=B_SAM - B_Ar Element C;C”=C_SAM - C_Ar Element D;D”=D_SAM - D_Ar · · · Element Z; Z” = Z_SAM - Z_Ar

[0032] The total amount of the target element contained in the sample gas can be calculated by adding up the absolute amounts of all elements contained in the sample gas obtained above.The concentration of each element in the sample gas can then be calculated using this total absolute amount of the target element contained in the sample gas and the absolute amount of each element contained in the sample gas.The element concentrations in the sample gas for element A, element B, element C, element D...element D are as follows: Element A concentration: A” / (A”+B”+C”+D”...Z”) Element B concentration: B” / (A”+B”+C”+D”...Z”) Element C concentration: C” / (A”+B”+C”+D”...Z”) Element D concentration: D” / (A”+B”+C”+D”...Z”) · · · Element Z concentration: Z” / (A”+B”+C”+D”...Z”)

[0033] Next, we will explain the case where the sample gas contains unmeasurable elements such as C (carbon) and N (nitrogen) at a specific ratio a that cannot be analyzed using an inductively coupled plasma mass spectrometer. Let Z be the unmeasurable element, its specific ratio be a, and let X and Y be measurable, known major component elements, whose content ratio is (1-a). In this case, elements A, B, C to W other than elements X, Y, and Z are measurable trace impurities. A standard solution containing known concentrations of measurable elements A, B, C, and Y other than element Z is used.

[0034] By carrying out the above-described first and second steps, data on elements A, B, C,...Y other than the unmeasurable element Z is obtained. Then, the absolute amounts of specific elements contained in the sample gas for the measurable elements A to Y are determined, and from these, the absolute amounts of specific elements contained in the sample gas for the major known component elements (X, Y) are extracted and summed to determine the total absolute amounts of specific elements contained in the major known component sample gas.

[0035] Element X;X”=X_SAM-X_BL Element Y; Y” = Y_SAM-Y_BL Element(X, Y);(X+Y)”=X_SAM-X_BL + Y_SAM-Y_BL

[0036] Then, by dividing this total absolute amount of specific elements contained in the major known component sample gas (X+Y)" by (1-a), the total absolute amount of specific elements contained in the 100% major known component sample gas is calculated. The concentration of each element contained in the sample gas can be determined from this total absolute amount of specific elements contained in the 100% major known component sample gas and the absolute amount of specific elements contained in the sample gas of each element (A-W) other than the major known component elements. The element concentrations of elements A-W are the impurity concentrations contained in the sample gas, and if the sample gas is generated from a solid sample, they will be the impurity concentrations in the solid sample.

[0037] Element A concentration: A” / ((X+Y)” / (1-a)) Element B concentration: B” / ((X+Y)” / (1-a)) Element C concentration: C” / ((X+Y)” / (1-a)) Element D concentration: D” / ((X+Y)” / (1-a)) · · · Element W concentration: W” / ((X+Y)” / (1-a))

[0038] Next, we will explain the results of quantitative analysis of impurities by LA-ICP-MS for solid samples with known impurity elements using an Agilent Technologies Model 8900 ICP-MS. [Example]

[0039] In Example 1, a Si wafer was used as the solid sample. The constituent elements of this solid sample were a base material of Si and four types of impurities: Na, Al, Mg, and Fe. The standard solution used in the quantitative analysis of Example 1 had a Si concentration of 1 ppm and concentrations of Na, Al, Mg, and Fe of 10 ppb each. The ICP-MS instrument conditions were an Ar gas flow rate of 1 L / min and a high-frequency output of 1300 W.

[0040] In the first step, the instrument background signal intensity (counts / sec) was measured with only argon gas introduced. With argon gas introduced, the standard solution was directly supplied to the standard solution nebulizer at a flow rate of 1 μL / min. The standard solution signal intensity (counts / sec) was then detected. The standard solution sensitivity value, which is the weight of a specific element per count of the standard solution signal intensity, was calculated, and the absolute amount (ag) of the instrument background standard solution was measured. The gas flow rate of the standard solution nebulizer was 0.3 L / min when the standard solution was introduced. When the standard solution was introduced at a flow rate of 1 μL / min, the Si concentration of the standard solution was 1 ppm, resulting in a Si introduction rate of 166,666,667 ag / sec. Since the concentrations of Na, Al, Mg, and Fe in the standard solution were each 10 ppb, the introduction rate of each element was 166,667 ag / sec. 100% (total amount) of the standard solution introduced at this introduction rate was introduced into the plasma. The measurement results for the first step are shown in Table 1.

[0041] [Table 1]

[0042] Next, the second step was carried out using a laser ablation device in which the gas components of the gas containing the particles emitted from the solid sample Si wafer were replaced with argon gas. The laser ablation conditions were a laser frequency of 257 nm, a laser irradiation frequency of 10,000 Hz, and a laser beam diameter of 13 μm.

[0043] In this second step, the signal intensity (counts / sec) of the sample gas was measured when only the sample gas, in which the gas components of the gas containing the particles emitted from the laser ablation device had been replaced with argon gas, was introduced, and the mixed signal intensity (counts / sec) was measured when the standard solution was supplied directly to the standard solution nebulizer at a flow rate of 1 μL / min while the sample gas was being introduced.The mixed standard solution sensitivity value, which is the weight of a specific element per 1 count of the signal intensity of the specific element mixed standard solution, was calculated, and the absolute amount (ag) of the specific element in the sample gas was measured.The results are shown in Table 2.

[0044] [Table 2]

[0045] The impurity concentration in the individual sample Si wafer was calculated from the absolute amount of the instrument background standard solution obtained in the first step (Table 1) and the absolute amount of the specific elements in the sample gas obtained in the second step (Table 2). The results are shown in Table 3.

[0046] [Table 3] [Example]

[0047] In Example 2, we will explain the results of an analysis using a Si-C wafer as a solid sample. This solid sample Si-C wafer is 50% Si (a major known component element) and 50% C (an unmeasurable element), and contains four types of impurities: Na, Al, Mg, and Fe.

[0048] In the quantitative analysis of Example 2, the standard solution composition, ICP-MS device conditions, and laser ablation device conditions were the same as those in Example 1. The first step in Example 2 was the same as that in Example 1. Note that C (carbon) was excluded as an element to be analyzed because it is contained as an impurity in the argon gas used to generate the plasma in ICP-MS, resulting in a high background, and because carbon has a high ionization potential and therefore poor ionization efficiency in the plasma.

[0049] In the second step of Example 2, the signal intensity (counts / sec) of the sample gas was measured when only the sample gas, in which the gas components of the gas containing the particles emitted from the laser ablation device had been replaced with argon gas, was introduced, and the mixed signal intensity (counts / sec) was measured when the standard solution was directly supplied to the standard solution nebulizer at a flow rate of 1 μL / min while the sample gas was being introduced.The mixed standard solution sensitivity value, which is the weight of the specific element per 1 count of the signal intensity of the specific element mixed standard solution, was calculated, and the absolute amount (ag) of the specific element in the sample gas was measured.The results are shown in Table 4.

[0050] [Table 4]

[0051] The impurity concentrations in the individual sample Si-C wafers were calculated from the absolute amounts of the instrument background standard solution obtained in the first step (see Table 1 in Example 1) and the absolute amounts of the specific elements in the sample gas obtained in the second step (Table 4). The results are shown in Table 5.

[0052] [Table 5]

[0053] In the solid sample of Example 2, 50% of the solid sample is Si, Since the absolute amount of Si (175,456,887ag) in Table 5 corresponds to the 50% Si concentration of the solid sample, the absolute amount in a 100% Si-C wafer is 175,456,887ag / 0.5=350,913,773ag. The impurity concentrations in the Si-C wafers shown in Table 5 were calculated by dividing the absolute amount of each impurity element by the absolute amount in a 100% Si-C wafer (350,913,773ag).

[0054] As shown in Tables 3 and 5, it was found that highly accurate quantitative analysis of the impurity concentration of a solid sample was possible without using a solid standard sample. [Explanation of symbols]

[0055] 1 ICP-MS (main unit) 11 Gasification sample introduction section 102 Torch section 103 Interface section 104 Mass Spectrometry Department 105 detector 110 Flow path 2. Standard solution introduction device 201 Standard solution storage container 202 Syringe Pump 203 Nebulizer for standard solution 204 Spray chamber for standard solutions 205 Waste containers 206 Standard solution inlet 301 Gas Replacer 302 Laser ablation device

Claims

1. a gasification sample introduction unit that introduces a sample gas generated by combining a laser ablation device that irradiates a solid sample to be measured with a laser beam to vaporize and atomize it, or a gas replacement device that replaces the gas components of a gas containing fine particles released by laser ablation with argon gas, or a sample gas containing a gas containing the sample to be measured; The apparatus comprises a torch section for forming plasma and ionizing a sample, an interface section for taking in ions from the plasma, a mass spectrometry section for separating the ions, and a detection section for detecting the separated ions; A method for quantitatively analyzing an element using an inductively coupled plasma mass spectrometer, comprising: a standard solution introducing device comprising: storage means for storing a standard solution containing a specific element of a known concentration; a syringe pump for drawing in and discharging the standard solution; and solution introducing means having a standard solution spray chamber combined with a standard solution nebulizer to which the standard solution is supplied; and a standard solution introducing path for introducing the standard solution flowing out from the standard solution spray chamber into a flow path connecting a gasification sample introducing section and a torch section, The standard solution contains all elements contained in the solid sample or gas containing the target substance as specific elements with known concentrations. a first step of detecting the instrument background signal intensity when only argon gas is introduced, and then, while argon gas is being introduced, directly supplying the standard solution to the standard solution nebulizer at a flow rate of 3 μL / min or less to introduce the standard solution from the solution introducing means into the torch section, detecting the standard solution signal intensities obtained from the detector for all elements contained in the standard solution, calculating specific element standard solution signal intensities by subtracting the instrument background signal intensity of each element from the standard solution signal intensity of each detected element, and calculating, for all elements contained in the standard solution, a standard solution sensitivity value, which is the weight of the specific element per 1 count of the specific element standard solution signal intensity, and an absolute instrument background standard solution amount calculated from the instrument background signal intensity and the standard solution sensitivity value, based on the specific element standard solution signal intensity and the amount of the specific element introduced in the standard solution; After detecting the signal intensity of the sample gas when only the sample gas is introduced, the standard solution is introduced into the torch section from the solution introducing means by directly supplying the standard solution to the standard solution nebulizer at a flow rate of 3 μL / min or less while the sample gas is being introduced, and the mixed signal intensities obtained from the detector are detected for all elements contained in the sample gas, and the signal intensities of the specific element mixed standard solution are calculated by subtracting the sample gas signal intensities of each element from the mixed signal intensities of each element detected, a second step of calculating, based on the signal intensity of the specific element mixed standard solution and the amount of the specific element introduced in the introduced standard solution, a mixed standard solution sensitivity value, which is the weight of the specific element per 1 count of the signal intensity of the specific element mixed standard solution, and an absolute amount of the specific element in the sample gas calculated from the signal intensity of the sample gas and the mixed standard solution sensitivity value, for all elements contained in the sample gas; Calculating the absolute amounts of specific elements contained in the sample gas for all elements contained in the sample gas by subtracting the absolute amounts of the instrument background standard solutions for each element obtained in the first step from the absolute amounts of specific elements contained in the sample gas for each element contained in the sample gas obtained in the second step; A method for quantitatively analyzing elements, characterized in that the concentration of each element contained in a sample gas is measured from the total absolute amount of a specific element contained in the sample gas for all elements contained in the sample gas and the absolute amount of a specific element contained in the sample gas for each element.

2. When a sample gas consisting of a solid sample to be measured or a gas containing a sample 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 measurable elements and major known component elements at a ratio of (1-a), The standard solution contains all elements, except for unmeasurable elements, contained in a solid sample to be measured or a sample gas made of a gas containing the sample to be measured, as specific elements of known concentrations; After calculating the absolute amount of the specific element contained in the sample gas for all measurable elements contained in the sample gas, Calculating the total absolute amount of specific elements contained in the major known component sample gas for the major known component elements; The total absolute amount of the specific elements contained in the major known component sample gas is divided by (1-a) to calculate the 100% total absolute amount of the specific elements contained in the major known component sample gas; The quantitative analysis method of claim 1, wherein the concentration of each element contained in the sample gas is measured from the total absolute amount of specific elements contained in the 100% major known component sample gas and the absolute amount of specific elements contained in the sample gas of each element other than the major known component elements.

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