JP3801958B2 - ICP mass spectrometer and analysis method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mass spectrometer using high frequency inductively coupled plasma (ICP) as an ion source and an analysis method thereof.
[0002]
[Prior art]
The ICP mass spectrometer is an apparatus that analyzes a measurement target element contained in a solution by ionizing a solution sample by ICP, guiding the ions to a mass analysis chamber, and detecting the intensity of each ion mass. One of the most powerful elemental analyzers in the field of ultra-trace analysis because of its extremely high sensitivity compared to conventional atomic absorption spectrometers and ICP emission spectrometers and the ease of simultaneous determination of other elements Is widely used.
[0003]
In such an ICP mass spectrometer, the sample ionized in the ICP section passes through the skimmer cone from the sampling cone and is introduced into the mass spectrometer. For this reason, for example, when a sample containing a silicon matrix to be analyzed in the semiconductor field or the like is supplied, a phenomenon occurs in which silicon oxide is deposited on the tip of the sampling cone. As the deposition of the silicon oxide film progresses, the opening at the tip of the sampling cone becomes narrow, so that the number of ions supplied to the mass spectrometry chamber side is reduced, resulting in a problem that the analysis sensitivity deteriorates.
[0004]
In order to prevent such deterioration of sensitivity and maintain a highly sensitive analysis state, a method of confirming sensitivity using a calibration curve is known. (Hereinafter referred to as “first prior art”.) For example, there is a method of grasping the degree of deposition of the oxide film at the tip of the sampling cone by confirming the increase or decrease in sensitivity from the slope of the calibration curve.
[0005]
There is also a method in which the silicon concentration in the sample is reduced in advance before analysis to prevent deposition of silicon oxide or the like adhering to the sampling cone. For example, a method of heating and concentrating a sample before analysis and removing the silicon component in the sample and introducing the sample into an apparatus has been attempted. (Hereafter referred to as “second prior art”.)
[0006]
[Problems to be solved by the invention]
However, in the first conventional technique described above, the analysis for confirming the sensitivity must be performed many times, and the working time becomes long. On the contrary, if the analysis for confirming the sensitivity is neglected, the sample is analyzed in a state where the analytical sensitivity is deteriorated, and the accurate analysis cannot be performed. If the sensitivity shows a decrease in the analysis, the sampling cone must be removed from the main body of the apparatus and the like must be cleaned, resulting in a prolonged working time.
[0007]
In the second prior art described above, a silicon component removal step must be provided before sample analysis, which takes time and effort. Furthermore, there is a possibility that the sample may be contaminated during the silicon component removing process, and accurate analysis may not be possible.
[0008]
In view of the above problems, it is an object of the present invention to provide an ICP mass spectrometer and a method thereof that can shorten the working time and can always perform highly sensitive analysis.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned object, the first feature of the present invention is that (a) a mass spectrometer that includes a sampling cone and mass-analyzes a sample ionized through the sampling cone; An ICP unit that is provided facing and generates plasma for ionizing the sample; (c) a sample introduction unit that introduces the sample into the ICP unit; and (d) a cleaning liquid supply unit that supplies the cleaning liquid to the ICP unit; (E) The gist of the present invention is an ICP mass spectrometer having a deposition monitor provided to face the sampling cone and detecting the deposition state of the deposited film deposited on the sampling cone.
[0010]
According to the first feature of the present invention, since the deposition state of the deposited film deposited on the sampling cone is detected by the deposition monitor, the state of analysis sensitivity can be grasped. Further, since the cleaning liquid is supplied to the ICP section in the high temperature plasma state by the cleaning liquid supply section, the deposited film deposited on the sampling cone can be effectively removed. Therefore, it is possible to always perform highly sensitive analysis without performing inaccurate analysis in a state where sensitivity is deteriorated.
[0011]
In the first feature of the present invention, the deposition monitor preferably comprises a reflectance measuring device. Furthermore, the deposition monitor preferably comprises an ellipsometer.
[0012]
In the first feature of the present invention, a central control processing device connected to a deposition monitor, detects a deposition state of a deposited film deposited on the surface of the sampling cone and determines whether or not to supply a cleaning liquid, and a central control processing It is preferable that the ICP mass spectrometer further includes an automatic supply unit that is connected to the apparatus and the ICP unit and automatically supplies the sample and the cleaning liquid.
[0013]
In the first feature of the present invention, the plasma is preferably a mass spectrometer characterized in that the plasma temperature is 5000 K or more and 9000 K or less. Furthermore, the cleaning liquid is preferably an ICP mass spectrometer made of hydrofluoric acid.
[0014]
The second feature of the present invention is that (a) the step of setting the plasma temperature of the ICP unit based on the analysis target of the sample, (b) the step of introducing the sample into the ICP unit, and (c) mass spectrometry of the sample. (D) a step of bringing the ICP part into a high temperature plasma state, (e) a step of supplying a cleaning liquid to the ICP part in a high temperature plasma state, and (f) a sampling cone by the cleaning liquid supplied to the ICP part. The gist of the present invention is an ICP mass spectrometry method including a step of removing a deposited film.
[0015]
According to the second feature of the present invention, the cleaning liquid is supplied to the ICP portion in the high temperature plasma state, and the cleaning liquid is brought into contact with the deposited film deposited on the sampling cone to remove the oxide film. The necessary work time can be shortened.
[0016]
In the second aspect of the present invention, it is preferable that the step of mass spectrometry of the sample is repeated at least once.
[0017]
In the second feature of the present invention, the step of setting the plasma temperature includes setting the ICP portion to a low temperature plasma state when the analysis target is a light element, and setting the ICP portion to a high temperature plasma state when the analysis target is a heavy element. It is preferable to make it.
[0018]
In the second aspect of the present invention, it is preferable that the method further includes the step of monitoring the deposition state of the deposited film deposited on the surface of the sampling cone. The step of monitoring the deposition state of the deposited film is preferably performed by measuring the refractive index of the deposited film. Furthermore, the step of monitoring the deposition state of the deposited film can be performed by determining the reflectance of the sampling cone where the deposited film is deposited.
[0019]
In the second aspect of the present invention, the method further includes the steps of detecting the deposition state of the deposited film deposited on the surface of the sampling cone, determining whether or not to supply the cleaning liquid, and automatically supplying the cleaning liquid. It is preferable.
[0020]
In the second feature of the present invention, the high temperature plasma state preferably has a plasma temperature of 5000K to 9000K. Furthermore, the cleaning liquid is preferably made of hydrofluoric acid.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and the shapes, dimensions, and the like are different from the actual ones. Therefore, specific shapes and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.
[0022]
(First embodiment)
As shown in FIG. 1, the ICP mass spectrometer according to the first embodiment of the present invention includes a sampling cone 31, and mass analyzer 30 that performs mass analysis on a sample ionized through the sampling cone 31; An ICP unit 20 that is provided facing the mass analysis unit 30 and generates plasma for ionizing the sample, a sample introduction unit 10 that introduces the sample into the ICP unit 20, and a cleaning liquid supply unit that supplies the cleaning liquid to the ICP unit 11.
[0023]
The sample introduction unit 10 introduces a sample to be analyzed into the ICP unit 20 via the introduction tube 12. The cleaning liquid supply unit 11 is a cleaning liquid for cleaning the deposited film (oxide film) 40 attached to the sampling cone 31 and the skimmer cone 32 of the mass analysis unit 30 as shown in FIG. 2, and the ICP unit 20 is in a high-temperature plasma state. At this time, it is supplied to the ICP unit 20 through the introduction pipe 12. The cleaning liquid is made of 10% hydrofluoric acid (HF aqueous solution) or the like. The cleaning liquid is hydrogen peroxide (H ₂ O ₂ Solution) and HF aqueous solution may be mixed, and nitric acid (HNO ₃ ) And an HF aqueous solution may be mixed. Furthermore, an alkaline solution such as potassium hydroxide (KOH solution) can also be used.
[0024]
The ICP unit 20 can generate high-temperature plasma of about several thousand K by inductively coupling high-frequency power. The ICP unit 20 includes a plasma torch unit 21 provided to face the mass analysis unit 30. The plasma torch part 21 is made of quartz glass and has the shape of a coaxial triple tube 23 as shown in FIG. The plasma torch unit 21 turns the introduced sample or inert gas into the plasma flame 14 by flowing high-frequency power through an induction coil (not shown) or the like provided on the outer periphery of the triple tube 23. In addition, the plasma torch unit 21 can change the temperature of the plasma flame 14 by the cooling gas 24 supplied into the triple tube 23. For example, the cooling gas 24 can be set to a high temperature plasma state when performing heavy element mass analysis of a sample, and can be set to a low temperature plasma state when performing light element mass analysis. The plasma temperature can generally be switched by RF power. In addition, an inert gas supply unit 22 is connected to the plasma torch unit 21. The inert gas supply unit 22 supplies the plasma torch unit 21 with an inert gas for generating plasma. Argon (Ar) or the like is used as the inert gas.
[0025]
The mass analysis unit 30 mass-separates the sample ionized by the ICP unit 20. The mass analyzing unit 30 is opposed to the sampling cone 31 provided facing the plasma torch unit 21, the skimmer cone 32 provided opposite to the plasma torch unit 21, and the skimmer cone 32 provided opposite to the plasma torch unit 21. In addition, a mass analyzer 33 provided on the side opposite to the sampling cone 31 is provided.
[0026]
As shown in FIG. 2, the sampling cone 31 and the skimmer cone 32 have a conical shape in which a small hole is provided in the center portion, and are provided so as to protrude from the plasma torch portion 21. The sampling cone 31 and skimmer cone 32 are differentially evacuated and efficiently draw ions from the ICP unit 20 provided in the atmosphere. The sampling cone 31 and the skimmer cone 32 are made of copper (Cu) or nickel (Ni) coated with titanium nitride (TiN) or platinum (Pt) to increase oxidation resistance. The mass analyzer 33 detects the ions drawn from the sampling cone 31 and the skimmer cone 32 by mass separation. As the mass analyzer 33, a quadrupole mass spectrometer or a magnetic field mass spectrometer is used.
[0027]
According to the ICP mass spectrometer according to the first embodiment of the present invention, the cleaning liquid is supplied to the mass analysis unit 30 by the cleaning liquid supply unit 11 when the plasma torch unit 21 is in the high temperature plasma state. The deposited film (oxide film) 40 adhering to 31 can be effectively removed. Therefore, the analysis sensitivity is not deteriorated due to adhesion of the deposited film (oxide film) 40, and the analysis can always be performed with high sensitivity.
[0028]
Next, an analysis method of the ICP mass spectrometer according to the first embodiment of the present invention will be described with reference to FIGS.
[0029]
(A) First, in S101, the plasma temperature of the plasma torch unit 21 is set, and in step S102, the sample to be analyzed is introduced into the sample introduction unit 10. For example, when analyzing light elements, the plasma torch unit 21 is set to a low temperature plasma state by RF power, and when heavy elements are targeted, a high temperature plasma state is set.
[0030]
(B) Next, in step S <b> 103, the introduced sample is introduced from the sample introduction unit 10 into the ICP unit 20 through the introduction tube 12, and is ionized by the plasma torch unit 21. FIG. 2 shows an enlarged view of the plasma flame 14 containing the ionized sample. The plasma flame 14 is drawn into the sampling cone 31 and the skimmer cone 32, and is separated and detected for each mass by the mass analyzer 33. At this time, a part of the ionized sample is not drawn into the mass analyzer 33 and is attached as a deposited film (oxide film) 40 on the sampling cone 31 and the skimmer cone 32 as shown in FIG.
[0031]
(C) Next, in step S104, the plasma torch part 21 is set to a high temperature plasma state. In step S102, if the high temperature plasma state has already been set, the high temperature plasma state is continued as it is. Here, the higher the plasma temperature in the high-temperature plasma state, the easier it is to ionize the cleaning liquid described later, and the deposited film (oxide film) 40 can be effectively cleaned. Therefore, the plasma gas temperature is set to 5000K to 9000K. It is preferable to do.
[0032]
(D) Next, in step S <b> 105, the cleaning liquid is introduced into the cleaning liquid supply unit 11. The cleaning liquid is introduced from the cleaning liquid supply unit 11 into the ICP unit 20 through the introduction pipe 12. Next, in step S <b> 107, the cleaning liquid introduced into the ICP unit 20 is ionized by the plasma torch unit 21. Next, in step S108, the ionized cleaning liquid is drawn into the mass analyzer 33 through the sampling cone 31 and the skimmer cone 32, and the cleaning liquid is applied to the deposited film (oxide film) 40 attached to the sampling cone 31 and the skimmer cone 32. Remove by contact.
[0033]
As described above, according to the ICP mass spectrometry method according to the first embodiment of the present invention, the deposited film (oxide film) 40 attached to the sampling cone 31 by supplying the cleaning liquid in the high-temperature plasma state after the sample analysis. Can be removed. Therefore, analysis can be continued without deteriorating sensitivity.
[0034]
Example 1
In Example 1 according to the first embodiment of the present invention, three types of samples were used to determine the state of analysis sensitivity of the ICP mass spectrometer shown in FIG. The sample includes a sample containing no silicon matrix (hereinafter referred to as “standard solution”), a sample containing 1000 ppm of the silicon matrix (hereinafter referred to as “sample A”), and a sample containing 500 ppm of the silicon matrix (hereinafter referred to as “sample solution”). "Sample B") was used. The standard solution was used as a solution for preparing a calibration curve at the start of sample analysis and at the end of sample analysis. Sample A and Sample B were prepared by vapor phase decomposition of 1 μm of a thermal oxide film formed on a silicon substrate. Samples to be analyzed were light elements (Na and Fe). Judgment of the deterioration of sensitivity was made by analyzing the standard solution and preparing a calibration curve before and after the analysis of Sample A and Sample B containing the silicon matrix. The standard solution, sample A, sample B, and cleaning solution used in the following examples are all the same.
[0035]
In Example 1, first, a standard curve (1) was prepared by analyzing a sample obtained by adding a known amount of impurities to a standard solution. Next, the sample A was analyzed. Next, the plasma torch part 21 was put into a high temperature plasma state, and cleaning liquid was supplied. The cleaning liquid was supplied for 5 minutes (in the following examples, all of the cleaning liquid was supplied for 5 minutes). The apparatus conditions in the high-temperature plasma state are: Ar gas total amount 2.533 Pa · m ³ / S, the distance between the plasma torch part 21 and the sampling cone 31 is 10 mm, the plasma gas temperature is 5000 K, and the operating frequency is 27.12 MHz (in the following examples, the above apparatus conditions are referred to as “high temperature plasma state”). Next, the sample A and the cleaning solution were supplied to the ICP mass spectrometer five times in total. Finally, the standard solution was analyzed again to prepare a calibration curve (2).
[0036]
FIG. 4 shows the analysis result of Example 1 using the ICP mass spectrometry method shown in FIG.
[0037]
4A is a calibration curve of a standard solution obtained by Na analysis, and FIG. 4B is a calibration curve of a standard solution obtained by Fe analysis. The horizontal axis represents the impurity concentration [ppb], and the vertical axis represents the count number indicating the ionic strength. The solid line is the calibration curve (1), and the broken line is the calibration curve (2). From FIG. 4, the slope of the calibration curve (2) was equivalent to the slope of the calibration curve (1). Therefore, in Example 1 using the ICP mass spectrometry method according to the first embodiment of the present invention, the analysis sensitivity was not deteriorated by analyzing the sample B including the silicon matrix.
[0038]
As a comparative example with respect to Example 1, FIG. 5 shows an analysis result when the high temperature plasma state shown in Step S104 of FIG. 3 is changed to a low temperature plasma state (plasma power 600 W). The apparatus conditions in the low-temperature plasma state are: Ar gas total amount 2.533 Pa · m ³ / S, the distance between the plasma torch part 21 and the sampling cone 31 was 10 mm, the plasma gas temperature was 2000 K, and the operating frequency was 27.12 MHz (in the following examples, the above apparatus conditions are referred to as “low temperature plasma state”). The slope of the calibration curve (2) shown in FIG. 5 was smaller than the slope of the calibration curve (1). Therefore, when the cleaning liquid is supplied in a low temperature plasma state, the sensitivity is deteriorated.
[0039]
Furthermore, as a comparative example, an analysis result when no cleaning liquid is supplied is shown in FIG. The slope of the calibration curve (2) was smaller than the slope of the calibration curve (1). Therefore, even when no cleaning liquid was supplied, the sensitivity deteriorated.
[0040]
As is apparent from FIGS. 4 to 6, according to Example 1 using the ICP mass spectrometry method according to the first embodiment of the present invention, the cleaning liquid is supplied with high-temperature plasma after the analysis of the sample. In addition, the sampling sensitivity can be prevented from being deteriorated by cleaning the sampling cone 31.
[0041]
(Example 2)
Example 2 differs in that the sample mass analysis shown in step S103 of FIG. 3 was performed twice in succession. The analysis was performed using Sample B whose silicon matrix concentration was half that of Sample A.
[0042]
In Example 2, first, a calibration curve (1) was prepared. Next, the sample B was analyzed twice in succession. Next, the plasma torch part 21 was set to a high temperature plasma state, the cleaning liquid was supplied, and the deposited film (oxide film) 40 was removed. Next, the above-described step of supplying the cleaning liquid after repeating the continuous analysis of the sample B twice was repeated twice, and the sample B was supplied six times in total. Finally, a calibration curve (2) was created.
[0043]
In FIG. 7, the analysis result in Example 2 is shown. The slope of the calibration curve (2) was equivalent to the slope of the calibration curve (1). Therefore, even in Example 2 using the ICP mass spectrometry method according to the first embodiment of the present invention, no deterioration in sensitivity occurred.
[0044]
As described above, according to the ICP mass spectrometry method according to the first embodiment of the present invention, the supply of the cleaning liquid does not have to be performed for each analysis of each sample, but is performed according to the matrix concentration contained in the sample. Thus, deterioration of sensitivity can be prevented.
[0045]
(Modification of the first embodiment)
In the ICP mass spectrometry method according to the first embodiment of the present invention, as shown in FIG. 8, the sampling cone 31 can be washed during the analysis of each sample.
[0046]
(A) First, in step S201, the plasma torch part 21 is set to a low temperature plasma state, and an analysis is performed on a light element contained in the sample. The sample introduction method is the same as that of the ICP mass spectrometry method according to the first embodiment of the present invention.
[0047]
(B) Next, in step S202, the plasma torch part 21 is shifted to a high temperature plasma state. Conditions such as plasma gas temperature in the high-temperature plasma state are the same as those in the ICP mass method according to the first embodiment.
[0048]
(C) Next, in step S203, analysis is performed on the heavy elements contained in the sample. During the heavy element analysis, the cleaning liquid is supplied from the cleaning liquid supply unit 11, and the cleaning liquid is brought into contact with the sampling cone 31 and the skimmer cone 32 to remove the deposited film (oxide film) 40.
[0049]
(D) After the heavy element analysis in step S203 is completed, in step S204, the high temperature plasma state is shifted to the low temperature plasma state. Here, when analyzing a new sample, it progresses to step S205. If a new sample is not analyzed, the operation is terminated.
[0050]
(E) Next, in step S205, the sample is exchanged, a sample to be newly analyzed is introduced from the sample introduction unit 10 to the mass analysis unit 30, and analysis is performed for light elements.
[0051]
As described above, according to the ICP mass spectrometry method according to the modification of the first embodiment of the present invention, it is not necessary to provide a step of supplying the cleaning liquid by supplying the cleaning liquid simultaneously during the heavy element analysis of the sample. . Therefore, the working time for removing the deposited film (oxide film) 40 can be shortened.
[0052]
(Example)
FIG. 9 shows the results of an example performed according to the ICP mass spectrometry method shown in FIG. Sample A was used for sample analysis. In FIG. 9, the slope of the calibration curve (2) was equivalent to the slope of the calibration curve (1). Therefore, it can be confirmed that no deterioration in sensitivity occurred in this example.
[0053]
(Second Embodiment)
As shown in FIG. 10, the ICP mass spectrometer according to the second embodiment of the present invention includes a sampling cone 31, a mass analyzer 30 that performs mass analysis on a sample ionized through the sampling cone 31, and a mass An ICP unit 20 that is provided facing the analysis unit 30 and generates plasma for ionizing the sample, a sample introduction unit 10 that introduces the sample into the ICP unit 20, and a cleaning liquid supply unit that supplies the cleaning liquid to the ICP unit 20 10 and a deposition monitor 50 that is provided opposite to the sampling cone 31 and detects the deposition state of the deposited film 40 deposited on the sampling cone 31, and a deposited film that is connected to the deposition monitor 50 and is deposited on the surface of the sampling cone 31. A central control processing unit (CPU) 60 that detects whether or not a deposition liquid is supplied and determines whether or not to supply a cleaning liquid; and a central control processing unit Connected to (CPU) 60 and ICP unit 20, and a an automatic supply unit 13 for supplying automatically sample and the washing solution. Since the automatic supply unit 13 and the central control processing unit (CPU) 60 are substantially the same as those in the first embodiment, duplicate descriptions are omitted.
[0054]
The automatic supply unit 13 includes an auto sampler or the like that automatically collects a sample and a cleaning solution and injects them into the ICP unit 20. The automatic supply unit 13 has, for example, a sample and a cleaning liquid in a test tube provided along the circumference of the turntable, and by injecting a needle-like tube provided at the top of the turntable into the test tube, The sample and the cleaning liquid are introduced into the ICP unit 20.
[0055]
The deposition monitor 50 is schematically shown in FIG. 10, but is actually a reflectance measuring device as shown in FIG. The reflectance measurement system as the deposition monitor 50 shown in FIG. 11 includes a light source 51 and a light receiver 52, and the light source 51 makes light incident on the sampling cone 31 at a certain incident angle. Measure the intensity of reflected light. The incident light intensity of the light source 51 branches through the half mirror 53 and is detected by the light intensity monitor 54. The incident light intensity measured by the light intensity monitor 54 and the reflected light intensity measured by the light receiver 52 are calculated by the calculation unit 57 via the interface 56, and reflectance = (reflected light intensity) / (incident light intensity). ) Here, as the light source 51 used for measuring the reflectance, it is preferable to use a gas laser or a semiconductor laser such as helium-neon (He—Ne). Further, in order to improve the accuracy of the deposition monitor 50, pulsed light can be incident. It is preferable that the wavelength of light to be used is a wavelength having the highest reflectivity with respect to the material of the sampling cone 31.
[0056]
As illustrated in FIG. 10, the CPU 60 includes a reflectance acquisition unit 61, a reflectance recording unit 62, and a determination unit 64. The reflectance acquisition unit 61 acquires the reflectance value of the sampling cone 31 measured by the deposition monitor 50. The reflectance recording unit 62 records in the reflectance recording device 63 the reflectance value acquired by the reflectance acquiring unit 61, the reference value that serves as a guide for supplying the cleaning liquid, and the like. The determination unit 64 compares the reflectance acquired by the reflectance acquisition unit 61 with the reflectance recorded by the reflectance recording device 63 and determines whether or not to supply the cleaning liquid.
[0057]
As described above, according to the ICP mass spectrometer in the second embodiment of the present invention, the reflectance of the sampling cone 31 is measured by the deposition monitor 50, so that the deposition is confirmed by confirming the decrease in the reflectance. The attached state of the film (oxide film) 40 can be seen. Further, the timing for supplying the cleaning liquid is determined by the CPU 60, and the cleaning liquid is automatically supplied by the automatic supply unit 13. Therefore, the deposited film (oxide film) 40 is efficiently removed, and the removal operation can be performed easily and in a short time. Can be done. Therefore, analysis can always be performed with high sensitivity.
[0058]
Next, an ICP mass spectrometry method according to the second embodiment of the present invention will be described with reference to FIG. 10 and FIG.
[0059]
(A) First, in step S301, the reflectance acquisition unit 61 acquires the reflectance of the sampling cone 31 before sample analysis. Here, the “reflectance of the sampling cone 31” is a value of the reflectance of the sampling cone 31 measured by the deposition monitor 50. Note that the reflectance value before sample analysis is set as the initial value.
[0060]
(B) Next, in step S <b> 302, the reflectance recording unit 62 records the initial value in the reflectance recording device 63. Further, the reflectance recording unit 62 records in the reflectance recording device 63 conditions for supplying a cleaning liquid preset by the user. For example, by setting a reflectance reference value based on the initial value, and supplying the cleaning liquid when the acquired reflectance value is lower than the reference value, if not less than the reference value, Record the sample to continue analysis.
[0061]
(C) Next, in step S303, the plasma temperature of the plasma torch unit 21 is set based on the type of element to be analyzed. In step S304, the automatic supply unit 13 introduces the sample to be analyzed into the ICP unit 20. Next, in step S305, the sample is ionized by the plasma torch unit 21, and the mass is obtained via the sampling cone 31 and skimmer cone 32. It introduce | transduces into the analyzer 33 and performs mass spectrometry.
[0062]
(D) Next, in step S306, the reflectance acquisition unit 61 acquires the reflectance of the sampling cone 31 again by the deposition monitor 50.
[0063]
(E) In step S307, the determination unit 64 determines whether or not the acquired reflectance value is lower than the reference value. If the acquired reflectance value is below the reference value, the process proceeds to step S308. If the acquired reflectance value exceeds the reference value, the process ends.
[0064]
(F) In step S308, the plasma torch unit 21 is set to a high temperature plasma state, and in step S309, the automatic supply unit 13 supplies the cleaning liquid to the ICP unit 20. Next, in step S <b> 310, the cleaning liquid introduced into the ICP unit 20 is ionized by the plasma torch unit 21. In step S311, the ionized cleaning liquid is brought into contact with the sampling cone 31 and the skimmer cone 32, and the deposited film (oxide film) 40 is removed. Next, in order to confirm whether or not the deposited film (oxide film) 40 has been removed, in step S306, the reflectance of the sampling cone 31 is measured again, and the obtained reflectance value waits above the reference value. If so, the process ends.
[0065]
As described above, according to the mass spectrometry method of the second embodiment of the present invention, the reflectance is measured after the sample analysis, and the degree of decrease of the reflectance with respect to the reference value is automatically determined. The cleaning liquid can be supplied to the mass analysis unit 30 side to clean the sampling cone 31. Therefore, it is possible to prevent the deterioration of sensitivity due to the deposition of the deposited film (oxide film) 40, and to always perform analysis in a highly sensitive state. Furthermore, according to the ICP mass spectrometric method according to the second embodiment of the present invention, the cleaning liquid is automatically supplied by the automatic supply unit 13, thereby shortening the work time for removing the deposited film (oxide film) 40. be able to.
[0066]
(Example)
In the example according to the second embodiment of the present invention, the calibration curve (1) was first created. Next, the reflectance was measured by the deposition monitor 50. Next, an initial value and a reference value were recorded by the reflectance recording unit 62. Here, in the present embodiment, the reflectance of the sampling cone 31 measured before the start of analysis is set to 1, and the reflectance ratio obtained thereafter is compared with the initial value to obtain the reflectance ratio. Set. The reference value for supplying the cleaning liquid was set to 0.98. Sample A was then introduced. Sample A was introduced five times in total.
[0067]
FIG. 13 shows the transition of the reflectance ratio measured by the deposition monitor 50 in this example. Although the ratio of the reflectance after the second time decreased slightly from 0.98, it was almost flat. Further, as shown in FIG. 14, the slope of the calibration curve {circle around (2)} is almost the same as the slope of the calibration curve {circle around (1)}, and it can be confirmed that no deterioration in sensitivity has occurred.
[0068]
On the other hand, as a comparative example with respect to the present embodiment, FIG. 15 shows a change in the reflectance ratio measured by the deposition monitor 50 when no cleaning liquid is supplied. The reflectance ratio continued to decrease as the number of measurements progressed. Further, as shown in FIG. 16, the slope of the calibration curve (2) was smaller than the slope of the calibration curve (1). Therefore, when no cleaning liquid is supplied at all, it can be confirmed that the reflectance ratio decreases and the sensitivity deteriorates.
[0069]
From the above, as apparent from FIGS. 13 to 16, according to the ICP mass spectrometry method in the second embodiment of the present invention, the reflectance is measured after the analysis of the sample, whereby the deposited film (oxide film) Since the 40 accumulation conditions can be confirmed, the state of analytical sensitivity can be determined. Therefore, an inaccurate analysis is not performed in a state where sensitivity is deteriorated. Furthermore, since the cleaning can be performed in a timely manner according to the deposition state of the deposited film (oxide film) 40, it is possible to always perform highly sensitive analysis without requiring the work such as removing the sampling cone 31.
[0070]
(Third embodiment)
As shown in FIG. 17, the ICP mass spectrometer according to the third embodiment of the present invention comprises an ellipsometer in which the deposition monitor 50 optically measures the refractive index, and is connected to the deposition monitor 50 and the automatic supply unit 13. 10 is different from FIG. 10 in that the CPU 60 further includes a refractive index acquisition unit 81 and a refractive index recording unit 82. Others are the same as those in the second embodiment, and a duplicate description is omitted.
[0071]
The deposition monitor 50 is schematically shown in FIG. 17, but is actually an ellipsometer as shown in FIG. As shown in FIG. 18A, a light source 51 and a manipulator 73 are provided. FIG. 13B is an ellipsometer viewed from a direction orthogonal to 13A. In the deposition monitor 50, the light source 51 makes light incident on the sampling cone 31 via the rotating polarizer 71, and the manipulator 73 receives the reflected light. The rotating polarizer 71 changes the light emitted from the light source 51 into linearly polarized light and enters the sampling cone 31. Reflected light changed to elliptically polarized light by the deposited film (oxide film) 40 deposited on the sampling cone 31 enters the light receiver (spectrometer) 76 via the analyzer 72 of the manipulator 73. Here, the manipulator 73 is moved by the manipulator driver 74 so that the analyzer 72 maintains a constant angle with respect to the incident angle by the rotating polarizer 71. The spectroscope 76 separates the reflected light changed to elliptically polarized light into light parallel to the incident surface (P-polarized light) and light perpendicular to the incident surface (S-polarized light). The split P-polarized light and S-polarized light are amplified by the amplification circuit 75, and the calculation unit 57 calculates the reflection coefficient via the interface 56. Further, the calculation unit 57 analyzes the linearly polarized light incident on the rotating polarizer 71 and the reflection coefficient of the reflected light measured by the light receiver (spectrometer) 76 to thereby analyze the deposited film (oxide film) 40 on the sampling cone 31. Calculate the refractive index.
[0072]
The CPU 60 further includes a refractive index acquisition unit 81 and a refractive index recording unit 82 in addition to the ICP mass spectrometer shown in FIG. 10, and the refractive index acquisition unit 81 acquires the value of the refractive index acquired by the deposition monitor 50. To do. The refractive index recording unit 82 records the refractive index value acquired by the refractive index acquisition unit 81, a reference value serving as a guide for supplying the cleaning liquid, and the like in the refractive index recording device 83.
[0073]
Thus, according to the ICP mass spectrometer of the third embodiment of the present invention, the refractive index of the thin film deposited on the sampling cone 31 can be measured by the deposition monitor 50. Furthermore, since the timing for supplying the cleaning liquid is determined by the CPU 60 and the cleaning liquid is supplied in a timely manner by the cleaning liquid supply unit 13, the deposited film (oxide film) 40 deposited on the sampling cone 31 can be effectively removed. .
[0074]
Next, an ICP mass spectrometric method according to the third embodiment of the present invention will be described with reference to FIG. The ICP mass spectrometry method according to the third embodiment of the present invention is substantially the same as the ICP mass spectrometry method shown in FIG.
[0075]
(A) First, in step S401, the refractive index acquisition unit 81 acquires the refractive index of the sampling cone 31 before sample analysis. Here, the “refractive index of the sampling cone 31” is a value of the refractive index of the sampling cone 31 measured by the deposition monitor 50.
[0076]
(B) Next, in step S <b> 402, the refractive index recording unit 82 records the initial value in the refractive index recording device 83. Further, the refractive index recording unit 82 records in the refractive index recording device 83 conditions for supplying a cleaning liquid set in advance by the user.
[0077]
(C) Next, in step S403, the plasma temperature of the plasma torch unit 21 is set based on the type of element to be analyzed, and in step S404, the automatic supply unit 13 sets the sample to be analyzed to the ICP unit. 20 is introduced. Next, in step S405, the sample is ionized by the plasma torch unit 21, introduced into the mass analyzer 33 via the sampling cone 31 and the skimmer cone 32, and mass analysis is performed.
[0078]
(D) Next, in step S406, the refractive index acquisition unit 81 acquires the refractive index measured by the deposition monitor 50 again.
[0079]
(E) In step S407, the determination unit 64 determines whether or not the value of the refractive index acquired in step S406 is lower than the reference value. If the acquired refractive index value is below the reference value, the process proceeds to step S408. If the obtained refractive index value exceeds the reference value, the process is terminated.
[0080]
(F) In step S408, the plasma torch unit 21 is set to a high temperature plasma state, and in step S409, the automatic supply unit 13 supplies the cleaning liquid to the ICP unit 20. Next, in step S410, the cleaning liquid introduced into the ICP unit 20 is ionized by the plasma torch unit 21. In step S411, the ionized cleaning liquid is brought into contact with the sampling cone 31 and the skimmer cone 32 to remove the deposited film (oxide film) 40. Then, the process proceeds to step S406, where the refractive index value is acquired. If it exceeds the reference value, the process is terminated.
[0081]
As described above, according to the ICP mass spectrometry method in the third embodiment of the present invention, the deposition state of the deposited film (oxide film) 40 can be confirmed by measuring the refractive index after the sample analysis. Similarly to the ICP mass spectrometry method in the second embodiment, the state of analysis sensitivity can be confirmed.
[0082]
(Example)
FIG. 20 shows the transition of the refractive index ratio measured by the deposition monitor 50 in this example. The ICP mass spectrometry method in this example was performed in the same procedure as in the example shown in FIG. The ratio of the refractive index changed from the initial value with the number of measurements. Therefore, when confirming the degree of deposition of the deposited film (oxide film) 40, it can be confirmed that the deposition monitor 50 that measures the refractive index can be used.
[0083]
(Other embodiments)
As described above, the present invention has been described according to the first to third embodiments. However, the description and the drawings that constitute a part of this disclosure do not limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.
[0084]
In the ICP mass spectrometers according to the first to third embodiments of the present invention already described, the cleaning liquid supply unit 11 is not only supplied from the introduction tube 12 together with the sample, but is supplied from another tube. You can also.
[0085]
Furthermore, in the second and third embodiments of the present invention, the sampling cone 31 can be appropriately removed in accordance with the deposition state of the deposited film (oxide film) 40, and the tip portion can be immersed in a cleaning solution, acid, or the like. is there.
[0086]
Furthermore, in the ICP mass spectrometers according to the second and third embodiments of the present invention, it is possible to perform manual operation without causing the central control processor (CPU) 60 and the automatic supply unit 13 to function.
[0087]
Furthermore, in the ICP mass spectrometer according to the second embodiment of the present invention, the reflectance may be measured with the layout of the optical system as shown in FIG. 18, and the third embodiment of the present invention is applied. In such an ICP mass spectrometer, ellipsometry may be performed with an optical system layout as shown in FIG. That is, where the light source 51 and the light receivers 52 and 76 are arranged can be changed as appropriate.
[0088]
Furthermore, in the ICP mass spectrometry method according to the third embodiment of the present invention, the initial value shown in step S402 in FIG. 19 is set as the refractive index value in the state where the deposited film is deposited on the sampling cone 31, and the reference value is set. Can be set to such a condition that the cleaning liquid is supplied when the ratio of the obtained refractive index to the initial value becomes ± 10%.
[0089]
As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.
[0090]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an ICP mass spectrometer and a method thereof that can shorten the working time and can always perform highly sensitive analysis.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an ICP mass spectrometer according to a first embodiment of the present invention.
FIG. 2 is an enlarged view for explaining a deposition state of a deposited film of the ICP mass spectrometer shown in FIG.
FIG. 3 is a flowchart showing an ICP mass spectrometry method according to the first embodiment of the present invention.
FIG. 4 is a calibration diagram showing the relationship between the impurity concentration and the count number measured in Example 1 of the first embodiment of the invention.
5 is a calibration diagram showing the relationship between the impurity concentration and the count number in Comparative Example 1 with respect to Example 1 in FIG. 4. FIG.
6 is a calibration diagram showing the relationship between the impurity concentration and the count number shown in Comparative Example 2 with respect to Example 1 in FIG. 4; FIG.
FIG. 7 is a calibration diagram showing the relationship between the impurity concentration and the number of counts in Example 2 measured in the first embodiment of the present invention.
FIG. 8 is a sequence diagram showing an ICP mass spectrometry method according to a first modification of the first embodiment of the present invention.
FIG. 9 is a calibration curve diagram showing the relationship between the impurity concentration and the count number measured in the example of the first modification of the first embodiment of the present invention.
FIG. 10 is a schematic view of an ICP mass spectrometer according to a second embodiment of the present invention.
FIG. 11 is a diagram showing details of a deposition monitor according to a second embodiment of the present invention.
FIG. 12 is a flowchart showing an ICP mass spectrometry method according to a second embodiment of the invention.
FIG. 13 is a diagram showing the relationship between the number of measurements and the reflectance ratio in an example of the second embodiment of the present invention.
FIG. 14 is a calibration diagram showing the relationship between the impurity concentration and the count number measured in the example of the second embodiment of the present invention.
15 is a diagram showing the relationship between the number of measurements and the ratio of reflectance in a comparative example with respect to the embodiment of FIG.
16 is a diagram showing the relationship between the impurity concentration and the count number of a comparative example with respect to the embodiment of FIG.
FIG. 17 is a schematic view of an ICP mass spectrometer according to a third embodiment of the present invention.
FIG. 18 is a diagram showing details of a deposition monitor according to a third embodiment of the present invention.
FIG. 19 is a flowchart showing an ICP mass spectrometry method according to a third embodiment of the invention.
FIG. 20 is a diagram illustrating the relationship between the number of measurements and the ratio of reflectance in an example of the third embodiment of the present invention.
[Explanation of symbols]
10 ... Sample introduction part
11 ... Cleaning liquid supply unit
12 ... Introduction pipe
13 ... Automatic supply unit
14 ... Plasma flame
20 ... ICP part
21 ... Plasma torch part
22 ... inert gas supply section
23 ... Triple tube
24 ... Cooling gas
30 ... Mass spectrometer
31 ... Sampling cone
32 ... Skimmer cone
33 ... Mass spectrometer
40 ... Deposited film (oxide film)
50 ... Deposition monitor
51. Light source
52. Light receiver
53 ... Half Mirror
54. Light intensity monitor
56 ... Interface
57 ... Calculation unit
60 ... Central control processor (CPU)
61: Reflectance acquisition unit
62 ... Reflectance recording section
63 ... Reflectance recording device
64 ... determination part
71 ... Rotating polarizer
72 ... Analyzer
73 ... Manipulator
74: Manipulator driver
75 ... Amplifier circuit
76. Light receiver (spectrometer)
81: Refractive index acquisition unit
82: Refractive index recording section
83 ... Refractive index recording device

Claims (12)

A mass analyzer having a sampling cone, and mass-analyzing a sample ionized through the sampling cone;
An ICP unit provided opposite to the mass spectrometric unit and generating plasma for ionizing the sample;
A sample introduction part for introducing the sample into the ICP part;
A cleaning liquid supply unit for supplying a cleaning liquid to the ICP unit;
An ICP mass spectrometer comprising: a deposition monitor provided to face the sampling cone and detecting a deposition state of a deposited film deposited on the sampling cone.   The ICP mass spectrometer according to claim 1, wherein the deposition monitor includes a reflectance measuring device.   The ICP mass spectrometer according to claim 1, wherein the deposition monitor is an ellipsometer. A central control processing device connected to the deposition monitor and for determining whether or not to supply the cleaning liquid by detecting the deposition state of the deposited film deposited on the surface of the sampling cone
4. The apparatus according to claim 1, further comprising: an automatic supply unit that is connected to the central control processing device and the ICP unit and automatically supplies the sample and the cleaning liquid. 5. ICP mass spectrometer.   The ICP mass spectrometer according to any one of claims 1 to 4, wherein the plasma has a plasma temperature of 5000K to 9000K.   The ICP mass spectrometer according to any one of claims 1 to 5, wherein the cleaning liquid is made of hydrofluoric acid. Setting the plasma temperature of the ICP portion based on the analysis target of the sample;
Introducing the sample into the ICP part;
Mass analyzing the sample;
Bringing the ICP part into a high temperature plasma state;
Monitoring the deposition state of the deposited film deposited on the surface of the sampling cone ;
Supplying a cleaning liquid to the ICP part in the high-temperature plasma state;
Removing the deposited film deposited on the sampling cone with the cleaning liquid supplied to the ICP unit;
ICP mass spectrometry method characterized by having and. 8. The ICP mass spectrometry method according to claim 7 , wherein the step of monitoring the deposition state of the deposited film is performed by measuring a refractive index of the deposited film. 8. The ICP mass spectrometric method according to claim 7 , wherein the step of monitoring the deposition state of the deposited film is performed by obtaining a reflectance of the sampling cone where the deposited film is deposited. Monitoring the deposition state of the deposited film deposited on the surface of the sampling cone and determining whether to supply the cleaning liquid ;
By the determination, ICP mass spectrometry method according to any one of claims 7-9, characterized by automatically supplying the cleaning liquid. The ICP mass spectrometry method according to claim 7 , wherein the high-temperature plasma state has a plasma temperature of 5000K to 9000K. The ICP mass spectrometric method according to claim 7 , wherein the cleaning liquid is made of hydrofluoric acid.

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