Sample suction ejector

Abstract

The purpose of the present invention is to provide a sample suction ejector which is suitable for laser ablation ICP analysis and is capable of maintaining a highly sensitive analysis accuracy. The present invention provides a sample suction ejector for laser ablation ICP analysis, said sample suction ejector being characterized by comprising: a fluid supply pipe having a nozzle part from which a pressurized fluid is jetted; a sample suction pipe connected so as to open into the upstream side of the nozzle part; and a diffuser for discharging the pressurized fluid jetted from the nozzle part together with an analysis sample aerosol suctioned from the sample suction pipe, wherein two of the sample suction pipes are provided at symmetrical positions with respect to a straight line which is a flow direction of the pressurized fluid such that the inflow angle of the suctioned analysis sample aerosol is 25-70° with respect to the straight line direction in which the pressurized fluid flows from the fluid supply pipes through the nozzle part and is discharged from the diffuser.

Description

Sample suction ejector

[0001] The present invention relates to a sample suction ejector used in high-frequency inductively coupled plasma mass spectrometry, and in particular to a sample suction ejector suitable for laser ablation ICP analysis, in which an analytical sample is evaporated and atomized by irradiation with laser light, followed by ICP mass spectrometry.

[0002] A known method for mass analyzing analytical samples using radio-frequency inductively coupled plasma (ICP) is laser ablation ICP analysis, in which a laser is irradiated onto a microscopic region of the analytical sample, vaporizing and atomizing the sample at the irradiated location to generate an analytical sample aerosol, which is then subjected to ICP mass analysis. Because laser ablation ICP analysis allows for highly accurate and continuous mass analysis of a specific region on the analytical sample surface, it is used in a wide range of fields, including the analysis of contaminants in semiconductor substrates, the analysis of element distribution and isotope ratios in geological samples, and the analysis of trace elements in biological materials (e.g., bark and cells).

[0003] In this laser ablation ICP analysis method, as described above, a laser is irradiated onto an analytical sample to vaporize and atomize it, generating an analytical sample aerosol, which is then introduced into an ICP analyzer for mass spectrometry. The following analytical techniques have been proposed as such analytical methods:

[0004] Patent Document 1 discloses a laser ablation ICP analysis method in which an analytical sample is atomized and discharged from a chamber together with a carrier gas by suction with an ejector, and then subjected to inductively coupled plasma mass spectrometry. This laser ablation ICP analysis method exhibits a sharp peak in ICP signal intensity, enabling highly sensitive analysis and easily analyzing analytical samples with large surface areas.

[0005] JP 2016-40537 A

[0006] In such laser ablation ICP analysis, when an analytical sample is introduced into an ICP analyzer, the analytical sample is generally aspirated using a sample aspirator. FIG. 1 shows a schematic cross-sectional view of a commonly used sample aspirator. In a conventional sample aspirator 100, a pressurized fluid G, which is an inert gas such as argon (Ar), is introduced into a fluid supply pipe 101, passes through a nozzle 102 provided in the fluid supply pipe 101, and is discharged from a diffuser 103. A sample aspirator pipe 104 for aspirating an analytical sample W is provided upstream of the nozzle 102. The pressurized fluid G is ejected at high speed from the nozzle 102 to create a low-pressure space, which allows an analytical sample S to be aspirated from the outside through the sample aspirator pipe 104. The aspirated analytical sample S is then discharged from the diffuser 103 together with the pressurized fluid G and introduced into the ICP analyzer.

[0007] In the conventional sample suction ejector shown in FIG. 1 , the fluid containing the analytical sample is introduced perpendicular to the flow direction of the pressurized fluid G. That is, the fluid containing the analytical sample S enters through the sample suction tube 104, bends 90° upstream of the nozzle 102, and proceeds toward the outlet of the diffuser 103. The analytical sample W may contain very hard substances such as Si and SiC. When an analytical sample containing such hard substances is aspirated using the sample suction ejector shown in FIG. 1 , it collides with the inner wall of the ejector upstream of the nozzle (near the XXX indicated by arrow A in FIG. 1 ) and may remain on the inner wall of the ejector. Residual Si, SiC, or other substances on the inner wall of the ejector may cause a memory effect in ICP analysis, adversely affecting analytical accuracy.

[0008] Under these circumstances, an object of the present invention is to provide a sample suction ejector suitable for laser ablation ICP analysis, which is capable of maintaining high analytical sensitivity and accuracy.

[0009] The present invention provides a sample suction ejector for use in laser ablation ICP analysis, in which an analytical sample is irradiated with laser light to generate an analytical sample aerosol by atomizing the analytical sample, the analytical sample aerosol is aspirated and collected, and the collected analytical sample is introduced into an inductively coupled plasma mass spectrometer for analysis.The sample suction ejector has a fluid supply pipe equipped with a nozzle portion from which pressurized fluid is ejected, a sample suction tube connected to open upstream of the nozzle portion, and a diffuser for discharging the pressurized fluid ejected from the nozzle portion together with the analytical sample aerosol aspirated from the sample suction tube, and is characterized in that two sample suction tubes are provided at symmetrical positions on a line which is the flow direction of the pressurized fluid, so that the inflow angle of the aspirated analytical sample aerosol is 25° to 70° relative to the linear direction of flow of the pressurized fluid which flows from the fluid supply pipe through the nozzle portion and is ejected from the diffuser.

[0010] According to the sample suction ejector of the present invention, two sample suction tubes are provided at a predetermined inflow angle relative to the linear direction of the pressurized fluid flowing from the fluid supply tube through the nozzle unit and ejected from the diffuser, at positions symmetrical to the line corresponding to the flow direction of the pressurized fluid. Therefore, upstream of the nozzle unit, the analysis sample aerosol flowing from the two sample suction tubes intersects with each other and is ejected toward the diffuser without colliding with the inner wall of the ejector. This prevents hard substances such as Si and SiC from remaining on the inner wall of the ejector, thereby preventing the memory effect of these hard substances. In the present invention, the upstream side of the nozzle unit refers to the region where the pressurized fluid supplied to the fluid supply tube passes through the nozzle unit and flows into the diffuser.

[0011] In the sample suction ejector according to the present invention, the inflow angle of the aspirated analysis sample aerosol is set to 25° to 70° relative to the linear flow direction of the pressurized fluid that flows from the fluid supply tube through the nozzle and is discharged from the diffuser. If the inflow angle exceeds 70°, the angle at which the analysis sample aerosol flows from the two sample suction tubes becomes large, and particles may collide with the inlet on the diffuser side. Setting the inflow angle to less than 25° makes the design of the sample suction ejector difficult. This inflow angle is preferably set to 30° to 45°.

[0012] The sample suction ejector according to the present invention is suitable for use in laser ablation ICP analysis, but is also applicable to standard ICP analysis, without any particular limitations. Furthermore, in the sample suction ejector according to the present invention, two sample suction tubes are provided at symmetrical positions with respect to a line in the flow direction of the pressurized fluid so that the inflow angle of the aspirated analysis sample aerosol is 25° to 70°. However, two more sample suction tubes can also be provided at the same inflow angle. In other words, it is also possible to provide four sample suction tubes around the line in the flow direction of the pressurized fluid.

[0013] According to the sample suction ejector of the present invention, even if the analysis sample contains hard substances such as Si or SiC, it can be introduced into an ICP-MS analyzer without leaving any hard substances on the inner walls of the ejector, thereby making it possible to maintain high analytical accuracy.

[0014] Schematic cross-sectional view of a conventional sample suction ejector. Schematic cross-sectional view of a sample suction ejector of the present invention. ７１ Time analysis data of Ga. Isotopes in Si wafer analysis after GaN wafer analysis using a conventional sample suction ejector ７１ Time analysis data of Ga isotopes in Si wafer analysis after GaN wafer analysis using the sample suction ejector of the present invention. ７１ Time analysis data for Ga.

[0015] The sample suction ejector of the present invention will now be described. Fig. 2 shows a schematic cross-sectional view of the sample suction ejector of the present invention.

[0016] The sample suction ejector 10 of the present invention has a fluid supply pipe 11 into which pressurized fluid G, which is pressurized Ar gas, is introduced, a nozzle portion 12 provided in the fluid supply pipe 11, and a diffuser 13, and is arranged in a straight line (dashed line X-X) so that the pressurized fluid G passes through the nozzle portion 12 and is ejected from the diffuser 13.

[0017] Two sample aspirating tubes (14, 14') for aspirating the analysis sample S are provided upstream of the nozzle unit 12. The sample aspirating tube 14 is positioned at an inflow angle θ (θ') with respect to a straight line (X-X) in the flow direction of the pressurized fluid G. Specifically, the angle between the dashed line Y, which represents the inflow direction of the analysis sample aerosol aspirated into the sample aspirating tube 14, and the X-X line, which represents the flow direction of the pressurized fluid G, is θ. The sample aspirating tube 14' is positioned symmetrically with respect to the straight line (X-X), which represents the flow direction of the pressurized fluid, i.e., at a position symmetrical to the sample aspirating tube 14 with respect to the straight line (X-X), so as to form an inflow angle θ' (= θ). The analysis sample aerosol aspirated from these two sample aspirating tubes (14, 14') flows into the nozzle unit 12 at an intersecting angle upstream, is ejected from the nozzle unit 12 at high speed, and is discharged from the diffuser 13 together with the pressurized fluid G. With this structure, the analysis sample aerosol flowing in from the two sample suction tubes (14, 14') is discharged from the diffuser 13 without colliding with the inner wall of the ejector.

[0018] The results of laser ablation ICP analysis performed using the conventional sample suction ejector shown in FIG. 1 and the sample suction ejector of the present invention shown in FIG. 2 will be described below.

[0019] First, we will explain the case where the conventional sample suction ejector shown in Figure 1 is used. The conventional sample suction ejector used in the analysis was made from SUS304 material. Ar gas was used as the pressurized fluid. The first analysis target was a Si wafer, and the laser ablation ICP analysis conditions were as follows: *Laser conditions: Femtosecond laser device (CARBIDE / Light Conversion) Laser output: 100%, irradiation frequency: 60 kHz *ICP-MS analysis conditions: ICP-MS device (Agilent 8900 / Agilent Technologies) Ejector supply Ar gas flow rate: 0.2 L / min

[0020] Figure 3 shows the isotope analysis of the Si wafer, which was the first target of analysis, performed by laser ablation ICP. ７１ The time-resolved data for Ga is shown. ７１ No Ga signal was detected.

[0021] Next, laser ablation ICP analysis was performed using a GaN wafer as the analysis object under the same analysis conditions as above. Thereafter, laser ablation ICP analysis was performed again under the same analysis conditions using the same Si wafer as the first analysis object.

[0022] FIG. 4 shows the isotope analysis of the laser ablation ICP analysis of the Si wafer performed after the analysis of the GaN wafer. ７１ The time-domain analysis data for Ga is shown in Figure 4. ７１ A large number of Ga signals were detected. This is thought to be because, during the laser ablation ICP analysis of the previously analyzed GaN wafer, GaN particles collided with and remained on the inner wall of the conventional sample suction ejector (near the XXX indicated by arrow A in Figure 1), and as a result of this memory effect, during the subsequent laser ablation ICP analysis of the Si wafer, Si particles sucked into the conventional sample suction ejector collided with the inner wall of the ejector on which the GaN particles remained, causing the GaN particles to be released.

[0023] Next, a case where the sample suction ejector of the present invention shown in Figure 2 is used will be described. The sample suction ejector of the present invention used in the analysis was made of SUS304 material. Ar gas was used as the pressurized fluid. The inflow angle θ (= θ') shown in Figure 2 was 45°. The conditions for the laser ablation ICP analysis were the same as those for the conventional sample suction ejector described above.

[0024] Regarding the sample suction ejector of the present invention, a Si wafer was used as the first analysis object and laser ablation ICP analysis was carried out. ７１ When we checked the time analysis data for Ga, ７１ No Ga signal was detected.

[0025] Next, laser ablation ICP analysis was performed using a GaN wafer as the analysis target under the same analytical conditions as above, followed by laser ablation ICP analysis of a Si wafer under the same analytical conditions.

[0026] FIG. 5 shows the isotope analysis of the laser ablation ICP analysis of the Si wafer performed after the analysis of the GaN wafer. ７１ As shown in FIG. 5, in the case of the sample suction ejector of the present invention, the time analysis data of Ga isotope ７１ No Ga signal was detected, which indicates that when the sample suction ejector of the present invention is used, no GaN particles remain on the inner wall of the sample suction ejector even when laser ablation ICP analysis of a GaN wafer is performed.

[0027] According to the sample suction ejector of the present invention, even if the analytical sample contains hard substances such as Si or SiC, the memory effect in the sample suction ejector can be prevented, and therefore high analytical accuracy can be maintained.

[0028] 10, 100 Sample suction ejector 11, 101 Fluid supply pipe 12, 102 Nozzle part 13, 103 Diffuser 14, 14', 104 Sample suction pipe G Pressurized fluid

Claims

1. A sample suction ejector used in laser ablation ICP analysis, in which a laser beam is irradiated onto an analytical sample to generate an analytical sample aerosol by atomizing the analytical sample, the analytical sample aerosol is sucked in and collected, and the collected analytical sample is introduced into an inductively coupled plasma mass spectrometer for analysis. The sample suction ejector has a fluid supply pipe equipped with a nozzle section from which pressurized fluid is ejected, a sample suction pipe connected to open upstream of the nozzle section, and a diffuser for discharging the pressurized fluid ejected from the nozzle section together with the analytical sample aerosol sucked in from the sample suction pipe, and is characterized in that two sample suction pipes are provided at symmetrical positions on a line that is the flow direction of the pressurized fluid, so that the inflow angle of the sucked analytical sample aerosol is 25° to 70° relative to the linear direction of flow of the pressurized fluid that passes from the fluid supply pipe through the nozzle section and is ejected from the diffuser.

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