Inductively coupled plasma mass spectrometry method

Abstract

To provide an inductively coupled plasma mass spectrometry capable of performing measurement with higher accuracy and in a shorter time than before by using only a more stable hot plasma condition and collectively measuring elements to be measured in trace metal impurity measurement in a semiconductor material.SOLUTION: In the inductively coupled plasma mass spectrometry for measuring a plurality of trace metal elements contained in a semiconductor material, pure ammonia gas or helium / ammonia mixed gas and hydrogen gas are used together as reaction gas, and a plurality of trace metal elements are measured with a plasma condition as hot plasma. It is preferable that the flow rates of the pure ammonia gas and the helium / ammonia gas mixture are in the range of 0. 5mL / min to 1mL / min, and the flow rates of the hydrogen gas are in the range of 2mL / min to 6mL.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to inductively coupled plasma mass spectrometry for measuring trace metal elements contained in semiconductor materials. [Background technology]

[0002] Inductively coupled plasma mass spectrometry (hereinafter sometimes referred to as ICP-MS) uses inductively coupled plasma as the ionization source introduced into a mass spectrometer, and is one of the analytical methods currently known for elemental analysis that allows for the most sensitive quantitative and qualitative analysis.

[0003] In ICP-MS, a sample solution is sprayed into a carrier gas such as argon to generate a mist containing the sample, and the constituent components are ionized by thermal excitation using a plasma device. The ionized constituents, including the target analyte, are then introduced into a vacuum mass analyzer using a sampler with a fine hole at the tip of a conical metal. The mass analyzer is equipped with a focusing lens, a mass separator such as a double-focusing mass separator or a quadrupole filter, and a detector, and measures ions as an electrical charge corresponding to their mass number. The target component in the sample solution is quantified based on the relationship between this electrical charge and the concentration of the sample.

[0004] When analyzing trace metal impurities, the sample contains high concentrations of elements that are not the target of measurement, which causes various interferences and makes accurate analysis impossible. For this reason, as described in Patent Document 1 and Non-Patent Document 1, interferences have been removed and reduced by combining various plasma modes (cool plasma, medium hot plasma, hot plasma) and various reactive gases (hydrogen, ammonia, oxygen, etc.) and using multiple modes for measuring one sample. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-165625 [Non-patent literature]

[0006] [Non-Patent Document 1] Kazuo Yamanaka, Agilent application note, 5991-7701EN, 2016. Summary of the Invention [Problem to be solved by the invention]

[0007] However, using multiple modes can lead to issues such as longer measurement times, an accompanying increase in the amount of sample solution, a rise in the detection limit, and reduced instrument stability due to the use of cool plasma and medium-hot plasma. Therefore, there is a need for faster, more stable measurements that allow more samples to be measured at once.

[0008] The present invention has been made in view of the above-mentioned problems, and aims to provide an inductively coupled plasma mass spectrometry method that uses only more stable hot plasma to simultaneously measure target elements in the measurement of trace metal impurities in semiconductor materials, thereby enabling measurements to be made more accurately and in a shorter time than conventional methods. [Means for solving the problem]

[0009] In order to solve the above problems, the present inventors have conducted extensive research and have come to the following findings. Normally, hot plasma alone provides high sensitivity but is prone to interference, so by using it in combination with cool plasma, which is less prone to interference, it is possible to measure more elements. Even in the case of hot plasma, by using hydrogen gas and ammonia gas simultaneously, the hydrogen gas can efficiently remove interference from argon, and the ammonia gas can efficiently remove interference from silicon when measuring silicon materials for semiconductors.

[0010] The present invention has been made based on the above-mentioned findings, and an inductively coupled plasma mass spectrometry method according to a first aspect of the present invention is an inductively coupled plasma mass spectrometry method for measuring a plurality of trace metal elements contained in a semiconductor material, characterized in that the method measures a plurality of trace metal elements by using pure ammonia gas or a helium / ammonia mixed gas in combination with hydrogen gas as reactive gases and by using hot plasma as plasma conditions.

[0011] According to the inductively coupled plasma mass spectrometry method of the first aspect of the present invention, pure ammonia gas or a helium / ammonia mixed gas is used in combination with hydrogen gas as the reactive gas. Therefore, even if the plasma conditions are hot plasma only, interferences derived from argon and silicon can be suppressed, and multiple trace metal elements can be measured accurately and in a short time.

[0012] The inductively coupled plasma mass spectrometry method of aspect 2 of the present invention is characterized in that, in the inductively coupled plasma mass spectrometry method of aspect 1 of the present invention, the flow rate of the pure ammonia gas or the helium / ammonia mixed gas is set within the range of 0.5 mL / min to 1 mL / min, and the flow rate of the hydrogen gas is set within the range of 2 mL / min to 6 mL / min.

[0013] According to the inductively coupled plasma mass spectrometry method of the second aspect of the present invention, the flow rate of pure ammonia gas or helium / ammonia mixed gas is set within the range of 0.5 mL / min to 1 mL / min, and the flow rate of hydrogen gas is set within the range of 2 mL / min to 6 mL / min. This makes it possible to fully utilize the effect of hydrogen gas in suppressing interference from argon and the effect of ammonia gas in suppressing interference from silicon, and enables accurate measurement of multiple trace metal elements even when the plasma conditions are limited to hot plasma only.

[0014] The inductively coupled plasma mass spectrometry method of embodiment 3 of the present invention is characterized in that, in the inductively coupled plasma mass spectrometry method of embodiment 1 or 2 of the present invention, the octopole bias voltage is in the range of -25V or more and -15V or less, the extraction electrode 1 voltage is in the range of +2V or more and +5V or less, the extraction electrode 2 voltage is in the range of -70V or more and -20V or less, the omega bias voltage is in the range of -70V or more and -20V or less, the omega lens voltage is in the range of +2V or more and +8V or less, and the Q-pole 1 incident voltage is in the range of -50V or more and -15V or less.

[0015] According to the inductively coupled plasma mass spectrometry method of aspect 3 of the present invention, the octopole bias voltage, extraction electrode 1 voltage, extraction electrode 2 voltage, omega bias voltage, omega lens voltage, and Q-pole 1 incident voltage are each specified as described above, so that even if the plasma conditions are hot plasma only, multiple trace metal elements can be measured stably and accurately.

[0016] The inductively coupled plasma mass spectrometry method of aspect 4 of the present invention is characterized in that, in the inductively coupled plasma mass spectrometry method of any one of aspects 1 to 3 of the present invention, at least two elements selected from Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Zr, Sr, Mo, Ag, Cd, Ba, W, and Pb are measured for each measurement sample.

[0017] According to the inductively coupled plasma mass spectrometry method of aspect 4 of the present invention, at least two elements selected from Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Zr, Sr, Mo, Ag, Cd, Ba, W, and Pb are measured for each measurement sample, making it possible to efficiently measure these trace metal elements contained in semiconductor materials in a short period of time. [Effects of the Invention]

[0018] According to the present invention, an inductively coupled plasma mass spectrometry method can be provided that uses only more stable hot plasma conditions and measures all elements to be measured in a batch in the measurement of trace metal impurities in semiconductor materials, thereby enabling measurements to be made more accurately and in a shorter time than conventional methods. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing an example of an inductively coupled plasma mass spectrometry apparatus for carrying out an inductively coupled plasma mass spectrometry method according to one embodiment of the present invention. [Figure 2] 2 is a cross-sectional view showing a plasma torch and a sampler of the inductively coupled plasma mass spectrometer shown in FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] An inductively coupled plasma mass spectrometry method according to an embodiment of the present invention will be described below. First, an example of an inductively coupled plasma mass spectrometer that can be used in the inductively coupled plasma mass spectrometry method of the present invention will be described.

[0021] FIG. 1 is a diagram showing the configuration of an example of an inductively coupled plasma mass spectrometer. The inductively coupled plasma mass spectrometer 10 includes a sample solution introduction section 11, an ICP generation section 12, a mass separation section 13, and a sampler 14 disposed between the ICP generation section 12 and the mass separation section 13.

[0022] The sample solution introduction section 11 is composed of a sample solution table 21, a liquid supply pump 22, a sprayer 23, a spray chamber 24, a carrier gas supply section 25, an additive gas supply section 26, and a plurality of pipes 27 connecting these. The sample solution table 21 can hold a plurality of types of sample solutions R contained in containers, and an aspirating tube 28 is introduced into any of the sample solutions R.

[0023] The liquid supply pump 22 sucks the sample solution R through a suction tube 28 inserted into the sample solution R, and supplies the sample solution R to the sprayer 23. As the liquid supply pump 22, a peristaltic pump, a syringe pump, or the like can be used. Alternatively, a method of supplying the liquid to the sprayer 23 by negative pressure suction utilizing the pressure difference generated from the vacuum inside the device and the atmospheric pressure without using a pump can also be used.

[0024] The sprayer 23 is supplied with the sample solution R and a carrier gas for generating an aerosol of the sample solution R from a carrier gas supply unit 25. An inert gas is preferably used as the carrier gas. The sprayer 23 aerosolizes the sample solution R. This aerosolized sample solution R (hereinafter sometimes referred to as sample mist) is carried by the carrier gas flow and introduced into the ICP generation unit 12. The gas introduced to make up for a shortage of carrier gas is called make-up gas.

[0025] The sprayer 23 is positioned so that its tip is exposed inside the spray chamber 24. The spray chamber 24 has a cylindrical wall through which droplets of the sample mist can circulate. The sample mist is supplied to the ICP generation unit 12 together with a carrier gas flow and a makeup gas flow. Meanwhile, droplets with a relatively large diameter are discharged from a wastewater drain 29 connected to the bottom of the spray chamber 24. An additive gas supply unit 26 that introduces an additive gas into the sample mist is connected between the spray chamber 24 and the ICP generation unit 12.

[0026] The ICP generating unit 12 is composed of a plasma torch 31 and a plasma gas supply unit 39 . 2 is a cross-sectional view showing an example of a plasma torch and a sampler. Plasma torch 31 includes a plasma generator cylinder 32 having an open end 32a, a sample mist inlet 33 connected to plasma generator cylinder 32, a plasma gas inlet 34, and a high-frequency induction coil 35. A cooling gas flow path (not shown) for passing a cooling gas to cool plasma generator cylinder 32 may be further formed on the outer periphery of plasma generator cylinder 32.

[0027] The plasma generating cylinder 32 is a cylindrical member, the inside of which serves as a plasma generating chamber 36 for generating plasma of an inert gas and ions of elements that constitute the sample solution. The sample mist introduction section 33 introduces the sample mist supplied from the spray chamber 24 into the plasma generation chamber 36 . One end of the plasma gas inlet is connected to a plasma gas supply unit 39 (see FIG. 1), and the plasma gas is introduced into the plasma generation chamber from the plasma gas inlet .

[0028] The high-frequency induction coil 35 is a conductor wound around the outer circumferential surface of the plasma generating cylinder 32, and a high-frequency current, which is the energy for generating the plasma 2, is applied to the plasma generating chamber 36. By applying a high-frequency current to the high-frequency induction coil 35 with a reactive gas introduced into the plasma generating chamber 36, the plasma 2 can be brought into an ignition state.

[0029] Thereafter, for analysis of the sample solution R, sample mist is introduced from the sample mist inlet 33. As a result, each element constituting the sample solution is ionized in the plasma 2. The plasma 2 is emitted from the open surface 32a of the plasma generating cylinder 32 toward the sampler 14. These are supported by a plasma torch moving device 43.

[0030] The plasma torch moving device 43 horizontally moves the unitized high-frequency induction coil 35 and plasma generating cylinder 32. This allows the distance between the open surface 32a of the plasma generating cylinder 32 and the sampling cone 41 that constitutes the sampler 14 to be increased or decreased, thereby making it possible to vary the sampling depth D, which will be described later, to any desired depth.

[0031] The sampler 14 is composed of a sampling cone 41 and a skimmer cone 42. The sampling cone 41 is a conical member with an opening 41a formed at the tip of the cone. The skimmer cone 42 is a conical member with a smaller diameter than the sampling cone 41 and is arranged so that a portion of it overlaps with the sampling cone 41. The skimmer cone 42 has an opening 42a formed at the tip of the cone so as to overlap coaxially with the opening 41a of the sampling cone 41.

[0032] The distance between the plasma torch 31 and the opening 41a of the sampling cone 41 is generally referred to as the sampling depth. More precisely, the sampling depth D is the distance between the position of the opening 41a of the sampling cone 41 and the outermost edge of the high-frequency induction coil 35 on the sampler 14 side.

[0033] Generally, if the sampling depth D is small, the number of ions passing through the opening 41a of the sampling cone 41 and the opening 42a of the skimmer cone 42 increases, and conversely, if the sampling depth D is large, the number of passing ions tends to decrease. Therefore, by adjusting the sampling depth D, which indicates the distance between the plasma torch 31 and the sampling cone 41, the number of ions passing through the sampler 14 can be changed.

[0034] Furthermore, plasma has a temperature distribution, and changing the sampling depth D makes it possible to control the temperature region of the plasma that is in close contact with the opening 41a of the sampling cone 41. In other words, by setting the sampling depth D to match the ionization potential of the element to be measured, it is possible to select a temperature region that provides optimal ionization efficiency for analysis.

[0035] In the case of hot plasma, where the plasma temperature is high, the sampling depth may be small because it takes a short time for the aerosol to be ionized. On the other hand, in cool plasma, where the plasma temperature is low, it takes time for the aerosol to be ionized, so the sampling depth needs to be increased.

[0036] Referring again to FIG. 1, the mass separation section 13 is composed of a focusing lens 51, a mass separator 52, a reaction cell 53, and a detector . The focusing lens 51 focuses the ions that have passed through the sampler 14 toward the mass separator 52. As the focusing lens 51, an ion lens is used.

[0037] The mass separator 52 separates the ions introduced through the focusing lens 51 according to their mass-to-charge ratio. The mass separator 52 may be a quadrupole separator, a magnetic deflection separator, or an ion trap separator. Among these, a quadrupole separator passes ions through four electrodes, applying a high-frequency current to each electrode to perturb the ions and allow only specific ions to pass through. By changing the voltage value of each electrode as the ions pass through the four electrodes, the mass-to-charge ratio of the ions that can pass through can be changed, thereby obtaining a mass spectrum. In this embodiment, a quadrupole separator is used as the mass separator 52.

[0038] The reaction cell 53 is a mechanism designed to reduce spectral interference caused by ions other than those of the element being analyzed. The interaction between the gas introduced into the cell and the ions passing through the cell separates the ions of the element being analyzed from the interfering ions, thereby reducing the interfering ions in the cell and improving analytical accuracy.

[0039] The detector 54 detects the ions separated by their mass-to-charge ratios in the mass separator 52. For example, an electron multiplier, a microchannel plate, or the like can be used as the detector 54. Such a detector intensifies and detects the ions that have passed through the mass separator 52.

[0040] The sampler 14 to the mass separation unit 13 are placed in a reduced pressure environment by a vacuum pump (not shown). For example, the ICP generation unit 12 is placed in an atmospheric pressure environment, and the vacuum level is reduced to 1×10 -6 The pressure is gradually reduced towards the detector 53, which is on the order of mbar.

[0041] An inductively coupled plasma mass spectrometry method according to an embodiment of the present invention, which uses an inductively coupled plasma mass spectrometry apparatus configured as described above, will now be described. The inductively coupled plasma mass spectrometry method of this embodiment is for measuring a plurality of trace metal elements contained as impurities in a semiconductor material. Examples of the semiconductor material to be measured include semiconductor silicon, compound semiconductors, semiconductor industry reagents, and ultrapure water. In this embodiment, the semiconductor material to be measured is described as silicon. In the plasma mass spectrometry method of this embodiment, at least two elements selected from Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Zr, Sr, Mo, Ag, Cd, Ba, W, and Pb are measured for each measurement sample.

[0042] In the inductively coupled plasma mass spectrometry method of this embodiment, measurements are performed using the above-mentioned inductively coupled plasma mass spectrometry apparatus in the following procedure. First, a container containing the prepared sample solution R is placed on the sample solution table 21, and the liquid supply pump 22 is operated to suck up the sample solution R placed on the sample solution table 21 through the suction tube 28, and the sample solution R is sprayed from the sprayer 23 by a carrier gas flow supplied from the carrier gas supply unit 25, forming a sample mist in the spray chamber 24. For example, argon gas is used as the carrier gas.

[0043] Additionally, the plasma torch moving device 43 is operated to move the unitized high-frequency induction coil 35 and plasma generating cylinder 32 horizontally. This adjusts the distance between the open surface 32a of the plasma generating cylinder 32 and the sampling cone 41 that constitutes the sampler 14. The distance between the open surface 32a of the plasma generating cylinder 32 and the sampling cone 41 is defined as the sampling depth D (mm).

[0044] Plasma gas is supplied to the plasma torch 31 from the plasma gas inlet 34, and a high-frequency current is applied to the high-frequency induction coil 35 of the plasma torch 31. This generates plasma in the plasma generation chamber 36 of the plasma torch 31. The output power of the high-frequency current of the plasma torch 31 at this time is referred to as the plasma output (W: watts).

[0045] The sample mist carried by the carrier gas is exposed to the plasma formed by the plasma torch 31, and the components of the sample solution R are ionized into individual elements.

[0046] The elements ionized by the plasma torch 31 are focused by a focusing lens 51 and then introduced into the first mass separator 52a. The first mass separator 52a separates the ions according to their mass-to-charge ratio. For example, in a quadrupole separator, a high-frequency current is applied to each electrode to perturb the ions, allowing only specific ions to pass through. At this time, the mass-to-charge ratio of the ions that can pass through can be changed by changing the voltage value of each electrode.

[0047] The ions that have passed through the first mass separator 52a are introduced into the reaction cell 53. In the reaction cell 53, a gas such as ammonia is introduced into the cell, and an interaction occurs between the gas molecules and the ions, thereby removing most of the interfering ions. The ions that have passed through the reaction cell 53 are again separated by mass-to-charge ratio by the second mass separator 52b. Interfering ions that have passed through the reaction cell 53 are also separated from the analyte element ions here, and only the analyte element ions with a specific mass-to-charge ratio are introduced into the detector 54. The detector 54 intensifies and detects the ions. This allows the mass spectrum of each ion to be obtained.

[0048] In the inductively coupled plasma mass spectrometry method of this embodiment, multiple trace metal elements are measured using only hot plasma as the plasma condition. That is, a high-frequency current is applied to the high-frequency induction coil 35 so that the plasma 2 generated in the plasma generation chamber 36 becomes hot plasma.

[0049] Here, if measurements are performed using only hot plasma, the plasma will be stable and sensitivity will be high, but interference will be more likely to occur, making it difficult to measure multiple trace metal elements with high accuracy. Therefore, in the plasma mass spectrometry method of this embodiment, pure ammonia gas or a helium / ammonia mixed gas and hydrogen gas are used in combination as the reaction gases introduced into the reaction cell 53.

[0050] By introducing hydrogen gas into the reaction cell 53, it becomes possible to efficiently remove interference from argon used as the plasma gas and carrier gas. Furthermore, by introducing pure ammonia gas or a mixed gas of helium and ammonia into the reaction cell 53, it becomes possible to efficiently remove interference from silicon, which is a semiconductor material.

[0051] In the plasma mass spectrometry method of this embodiment, the flow rate of the pure ammonia gas or the helium / ammonia mixed gas is preferably set within the range of 0.5 mL / min to 1 mL / min. By setting the flow rate of pure ammonia gas or helium / ammonia mixed gas to 0.5 mL / min or more, it becomes possible to more efficiently remove interference from silicon. On the other hand, by setting the flow rate of pure ammonia gas or helium / ammonia mixed gas to 1 mL / min or less, it becomes possible to suppress the decrease in sensitivity of elements that easily react with ammonia and maintain high sensitivity for all elements.

[0052] In the plasma mass spectrometry method of this embodiment, the flow rate of the hydrogen gas is preferably set within the range of 2 mL / min to 6 mL / min. By setting the hydrogen gas flow rate to 2 mL / min or higher, it is possible to more efficiently remove interference from argon. In addition, introducing an appropriate amount of hydrogen into the cell focuses the ions in the cell, increasing sensitivity. On the other hand, by setting the hydrogen gas flow rate to 6 mL / min or less, it is possible to prevent the probability of ions and hydrogen from colliding too high, maintaining high sensitivity for all elements.

[0053] Furthermore, in the plasma mass spectrometry method of this embodiment, it is preferable to set various voltage conditions as follows.

[0054] (Octopole bias voltage: -25V to -15V) The octopole bias voltage is determined by the flow rate of hydrogen, pure ammonia gas, or helium / ammonia mixed gas, and is adjusted to efficiently cause collisions and reactions between ions and gas molecules in the cell.

[0055] (Extraction electrode 1 voltage: within the range of +2V to +5V) (Extraction electrode 2 voltage: -70V to -20V) The extraction electrode 1 voltage and extraction electrode 2 voltage are adjusted together. Setting the extraction electrode 1 voltage to +5V or less prevents excessive ion repulsion, which would otherwise reduce sensitivity. Setting the extraction electrode 1 voltage to +2V or more reduces the amount of matrix ions, thereby lowering the background.

[0056] (Omega bias voltage: -70V to -20V) (Omega lens voltage: within the range of +2V to +8V) The omega bias voltage and omega lens voltage are adjusted together. Sensitivity can be improved by setting the omega bias voltage to -20V or less. Background can be reduced by setting the omega bias voltage to -70V or more.

[0057] (Q pole 1 incident voltage: in the range of -50V to -15V) The background can be reduced by setting the Q-pole 1 incident voltage to -15 V or less, while the sensitivity can be improved by setting the Q-pole 1 incident voltage to -50 V or more.

[0058] By performing measurements under the voltage conditions described above, it becomes possible to stably measure a plurality of trace metal elements even when the plasma conditions are limited to hot plasma only.

[0059] According to the plasma mass spectrometry method of this embodiment configured as described above, pure ammonia gas or a helium / ammonia mixed gas is used in combination with hydrogen gas as the reactive gas. Therefore, even if the plasma conditions are limited to hot plasma, interference from argon and interference from silicon can be suppressed, and multiple trace metal elements can be measured accurately and in a short time.

[0060] In the plasma mass spectrometry method of this embodiment, when the flow rate of pure ammonia gas or helium / ammonia mixed gas is set within the range of 0.5 mL / min to 1 mL / min, and the flow rate of hydrogen gas is set within the range of 2 mL / min to 6 mL / min, the hydrogen gas can effectively suppress interference from argon, and the ammonia gas can effectively suppress interference from silicon, and multiple trace metal elements can be accurately measured even when the plasma conditions are limited to hot plasma.

[0061] In the plasma mass spectrometry method of this embodiment, if the octopole bias voltage is within the range of -25V to -15V, the extraction electrode 1 voltage is within the range of +2V to +5V, the extraction electrode 2 voltage is within the range of -70V to -20V, the omega bias voltage is within the range of -70V to -20V, the omega lens voltage is within the range of +2V to +8V, and the Q-pole 1 injection voltage is within the range of -50V to -15V, multiple trace metal elements can be measured stably and accurately even when the plasma conditions are limited to hot plasma.

[0062] In the plasma mass spectrometry method of this embodiment, when at least two elements selected from Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Zr, Sr, Mo, Ag, Cd, Ba, W, and Pb are measured per measurement sample, it becomes possible to efficiently measure these trace metal elements contained in semiconductor materials in a short period of time.

[0063] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Example]

[0064] The results of confirmation experiments conducted to confirm the effectiveness of the present invention will be described below.

[0065] <Example of the present invention> Using a 2 vol% aqueous nitric acid solution, a 1 ppb mixed standard solution (nitric acid 2 vol%), and a 1 ppb mixed standard solution (Si concentration: 100 massppm, 500 massppm), the ICP-MS was set under the following conditions, and the BEC (background equivalent concentration), sensitivity, measurement stability, and the influence of the Si matrix were evaluated for each of the elements Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Zr, Sr, Mo, Ag, Cd, Ba, W, and Pb. In the present invention, measurements were carried out using only hot plasma as the plasma condition.

[0066] Lens type: S lens RF power: 1500W Nebulizer gas: 0.7 L / min Make-up gas: 0.52L / min Sampling depth: 8mm Extraction electrode 1 voltage: +3.6V Extraction electrode 2 voltage: -60V Omega bias voltage: -50V Omega lens voltage: +7V Q pole 1 incident voltage: -25V Hydrogen flow rate: 5 mL / min Helium / ammonia flow rate: 5% Octopole bias voltage: -20V Deflection lens voltage: -10V

[0067] <Conventional example> Using the measurement solution used in the above-mentioned example of the present invention, an ICP-MS was set under the following conditions, and the BEC (background equivalent concentration), sensitivity, measurement stability, and influence of the Si matrix were evaluated for each of the elements Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Zr, Sr, Mo, Ag, Cd, Ba, W, and Pb. In the conventional examples, the elements to be measured were divided into cool plasma (conventional example 1), medium hot plasma (conventional example 2), and hot plasma (conventional example 3) as plasma conditions, and measurements were carried out for each.

[0068] (Conventional example 1) Measurement elements: Li, Na, Mg, Al, K, K, Ca, Cr, Mn, Fe, Ni, Co, Cu Lens type: S lens RF power: 800W Nebulizer gas: 0.7 L / min Make-up gas: 0.65L / min Sampling depth: 18mm Extraction electrode 1 voltage: -60V Extraction electrode 2 voltage: -6V Omega bias voltage: -50V Omega lens voltage: +7V Q pole 1 incident voltage: -25V Helium / ammonia flow rate: 15% Octopole bias voltage: -10V Deflection lens voltage: -3V

[0069] (Conventional example 2) Measurement elements: Ti, V, Zn, Sr, Mo, Ag, Cd, Ba, Pb Lens type: S lens RF power: 1500W Nebulizer gas: 0.7 L / min Make-up gas: 0.52L / min Sampling depth: 8mm Extraction electrode 1 voltage: -200V Extraction electrode 2 voltage: -20V Omega bias voltage: -200V Omega lens voltage: +13V Q pole 1 incident voltage: -25V Helium / ammonia flow rate: 7% Octopole bias voltage: -5V Deflection lens voltage: +7V

[0070] (Conventional example 3) Measurement elements: As, Zr, W Lens type: S lens RF power: 1500W Nebulizer gas: 0.7 L / min Make-up gas: 0.52L / min Sampling depth: 8mm Extraction electrode 1 voltage: -200V Extraction electrode 2 voltage: -20V Omega bias voltage: -200V Omega lens voltage: +13V Q pole 1 incident voltage: -25V Oxygen flow rate: 7% Octopole bias voltage: -5V Deflection lens voltage: +7V

[0071] Table 1 shows the evaluation results of the measurement times for the elements to be measured in the example of the present invention and the conventional example. The BEC (background equivalent concentration) and sensitivity of the invention example and conventional example are shown in Table 2. The BEC and sensitivity were calculated as follows. BEC = Intensity when measuring 1 vol% nitric acid aqueous solution / slope of calibration curve Sensitivity = Intensity when measuring 1 ppb mixed standard solution

[0072] Furthermore, the measurement stability of the present invention example and the conventional example is shown in Table 3. The measurement stability was evaluated using the RSD (relative standard deviation) when measuring a 1 ppb mixed standard solution. The matrix resistance of the inventive example and conventional example is shown in Table 4. The matrix resistance was evaluated using the relative sensitivity when measuring a 1 ppb Si-containing mixed standard solution to the sensitivity when measuring a 1 ppb mixed standard solution. Relative sensitivity (%) = Intensity when measuring 1 ppb mixed standard solution (Si concentration: 100 / 500 ppm) / Intensity when measuring 1 ppb mixed standard solution × 100

[0073] [Table 1]

[0074] [Table 2]

[0075] [Table 3]

[0076] [Table 4]

[0077] From the results in Table 1, it was confirmed that the measurement time per sample in the example of the present invention was about one-third of that in the conventional example, and that measurement was possible in a short time. Furthermore, from the results in Table 2, it can be seen that the sensitivity of the inventive example to some elements is lower than that of the conventional example, but sufficient sensitivity is still achieved, and it was confirmed that the BEC is at a level comparable to that of the conventional example. Furthermore, the results in Tables 3 and 4 confirm that the present invention examples also have improved measurement stability and matrix resistance.

[0078] As described above, according to the present invention, it has been confirmed that an inductively coupled plasma mass spectrometry method can be provided that uses only more stable hot plasma conditions and measures all the elements to be measured in the measurement of trace metal impurities in semiconductor materials at once, thereby enabling measurements to be made more accurately and in a shorter time than conventional methods.

Claims

1. 1. An inductively coupled plasma mass spectrometry method for measuring a plurality of trace metal elements contained in a semiconductor material, comprising:

1. An inductively coupled plasma mass spectrometry method for measuring a plurality of trace metal elements, using pure ammonia gas or a helium / ammonia mixed gas in combination with hydrogen gas as reactive gases, and setting the plasma conditions to hot plasma.

2. 2. The inductively coupled plasma mass spectrometry method according to claim 1, wherein the flow rate of the pure ammonia gas or the helium / ammonia mixed gas is set to a range of 0.5 mL / min to 1 mL / min, and the flow rate of the hydrogen gas is set to a range of 2 mL / min to 6 mL / min.

3. The inductively coupled plasma mass spectrometry method according to claim 1 or 2, wherein the octopole bias voltage is in the range of -25 V or more and -15 V or less, the extraction electrode 1 voltage is in the range of +2 V or more and +5 V or less, the extraction electrode 2 voltage is in the range of -70 V or more and -20 V or less, the omega bias voltage is in the range of -70 V or more and -20 V or less, the omega lens voltage is in the range of +2 V or more and +8 V or less, and the Q-pole 1 incident voltage is in the range of -50 V or more and -15 V or less.

4. 3. The inductively coupled plasma mass spectrometry method according to claim 1, wherein at least two elements selected from Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Zr, Sr, Mo, Ag, Cd, Ba, W, and Pb are measured for each measurement sample.

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