JP6166565B2 - Glow discharge mass spectrometer and glow discharge mass spectrometry using the same - Google Patents

Description

  The present invention relates to a glow discharge mass spectrometer and a glow discharge mass spectrometry method using the same, and more particularly to a flat cell type glow discharge mass spectrometry device and a glow discharge mass spectrometry method using the same.

  Glow discharge mass spectrometry is a mass spectrometry that uses glow discharge for ionization of atoms in a sample. When a voltage is applied using a conductive solid sample as a cathode in an inert gas atmosphere, a positively charged argon plasma is generated, and the plasma collides with the sample surface and knocks out atoms in the sample. At the same time, atoms are ionized by the generated glow discharge and introduced into a double-focusing mass spectrometer, and the ionized constituent elements are measured by the mass spectrometer. Glow discharge mass spectrometry enables trace analysis of most elements in the periodic table.

  Since the glow discharge mass spectrometry can directly analyze a solid sample and the sensitivity difference between elements is small, semi-quantitative analysis and quantitative analysis can be performed based on the ionic strength ratio between the main component and the target element. Glow discharge mass spectrometry is an analysis method that has received much attention in the field of electronic materials, and no alternative method exists at present.

  The glow discharge mass spectrometry includes a pin cell type that performs glow discharge analysis on a pin-shaped sample and a flat cell type that performs glow discharge analysis on a flat plate-shaped sample (Patent Document 1). Among these, the flat cell type glow discharge analysis enables a minute amount analysis or depth direction analysis of the sample surface in the macro region as compared with the pin cell type, and its application range is widened.

JP-A-7-122606

  In the flat cell type glow discharge mass spectrometry, the surface of the sample is shaved by the plasma of the inert gas colliding with the sample surface and knocking out atoms in the sample as described above. According to the present inventor, when a conventional flat cell type glow discharge mass spectrometry is used, when the shape of the sample surface after analysis is observed, the surface is shaved to a uniform depth as shown in FIG. I found out. Specifically, the discharge trace (scraped trace) on the sample surface in FIG. 1 is deep near the edge of the sample surface (also referred to as an edge drop; indicated by a circle in FIG. 1), and as it goes to the center. It is shallow. When such a non-uniform surface portion is analyzed, it is apparent that accurate mass analysis of composition information for sample surface or depth analysis in the macro region is difficult.

  The present inventor has conducted research to solve the above problems, and the edge drop occurs at a portion corresponding to the edge of the anode ring of the discharge electrode used in the flat cell type glow discharge mass spectrometer. I paid attention to. And it discovered that generation | occurrence | production of the said edge drop could be suppressed by keeping the distance of the said anode ring and the sample surface away. And as the means, by controlling the thickness of the insulating ring to prevent electrical short-circuit between the discharge electrode provided with the anode ring and the sample holder, the distance between the anode ring and the sample surface is increased, and the edge drop is prevented. It has been found that generation is suppressed, thereby enabling accurate mass analysis of the sample.

The present invention completed on the background of the above knowledge is, in one aspect, a flat cell type glow discharge mass spectrometer, a discharge electrode, a sample holder for supporting a sample serving as a counter electrode, and the discharge. Edge drop on the surface of the sample after analysis, comprising an insulating ring for preventing an electrical short circuit between the electrode for electrode and the sample holder, wherein the thickness of the insulating ring is 1.5 to 3.0 mm Is a glow discharge mass spectrometry apparatus for performing glow discharge mass spectrometry without forming a gas.

  In another aspect, the present invention is a glow discharge mass spectrometry method for performing mass analysis of a sample using the glow discharge mass spectrometer of the present invention.

  According to the present invention, in glow discharge mass spectrometry, accurate mass analysis in the sample surface or depth direction in the macro region can be realized.

It is a graph which shows the discharge trace of the sample surface obtained by the conventional glow discharge mass spectrometry (Example 1). It is a schematic diagram of a flat cell type glow discharge mass spectrometer according to an embodiment of the present invention. It is a schematic diagram of the glow discharge part which concerns on embodiment of this invention. It is a schematic diagram of the sputter | spatter area | region of the sample which concerns on embodiment of this invention. 6 is a graph showing the discharge trace in the depth direction of the sample surface obtained by glow discharge mass spectrometry of Example 2. 4 is a graph showing discharge traces in the depth direction of a sample surface obtained by glow discharge mass spectrometry of Example 3. 6 is a graph showing discharge traces in the depth direction of a sample surface obtained by glow discharge mass spectrometry of Example 4.

  FIG. 2 is a schematic diagram of a flat cell type glow discharge mass spectrometer according to an embodiment of the present invention. A glow discharge mass spectrometer separates ions generated by glow discharge in the glow discharge portion into a target ion using a magnetic field and a slit. After selecting and subsequently converging the energy in the electric field, the constituent elements ionized by the detector are measured.

  FIG. 3 shows a schematic diagram of a glow discharge section according to an embodiment of the present invention. The glow discharge mass spectrometer is a flat cell type, and the sample to be measured is formed in a cylindrical shape and a square shape. The glow discharge unit includes a sample holder that supports the sample. A sample insertion portion with a spring for inserting a sample to be measured into the sample holder is inserted into the sample holder. On the opposite side of the sample holder, an insulating ring and an insulating member for preventing an electrical short circuit between the discharge electrode and the sample holder are provided. Further, a glow discharge chamber composed of an anode ring having a space into which an inert gas is introduced and an anode body is provided via an insulating ring. The sample uses a conductive material and serves as a counter electrode for the glow discharge chamber.

  In FIG. 3, when a voltage is applied to a glow discharge chamber in an inert gas atmosphere, for example, an argon atmosphere, using a conductive solid sample as a cathode, positively charged argon plasma is generated, and the plasma is applied to the sample surface. Colliding and knocking out atoms in the sample by sputtering. At the same time, atoms in the sample are ionized by the generated glow discharge, emitted from the glow discharge portion, and separated and selected into target ions by a magnetic field and a slit. Subsequently, after the energy is converged by an electric field, the ionized constituent elements are measured with a mass spectrometer.

  When the above plasma sputters the surface of a cylindrical or square sample, a circular region as shown in FIG. 4 is sputtered. This region depends on the shape of the anode ring in which the discharge electrode emits argon plasma to the sample surface. Conventionally, in the sputter region on the sample surface, the portion corresponding to the edge of the circular hole of the anode ring has been sputtered particularly deeply to form an edge drop. On the other hand, in the present invention, the thickness of the insulating ring interposed between the anode ring and the sample surface is formed to be 1.5 mm or more, so that the influence of the shape of the anode ring in the sputter region on the sample surface is affected. It is suppressed and the occurrence of the edge drop is suppressed well. In addition, if the distance between the anode ring and the sample surface is too large, it is difficult to satisfactorily sputter the sample surface with the plasma of the inert gas. For this reason, it is preferable that the thickness of the insulating ring is 1.5 to 3.0 mm.

  The insulating ring may be made of any insulating material, but flexible Teflon (registered trademark), ceramic oxide, ceramic nitride, etc. are used to improve the contact between the sample holder and the anode ring. preferable.

  In the present invention, in order to suppress the influence of the sputter region on the sample surface from the shape of the anode ring, the thickness of the insulating ring is controlled, and the surface area of the insulating ring and the inner diameter of the ring are controlled. The size is not particularly limited.

  A voltage is applied to the space surrounded by the discharge electrode using an electrically conductive solid sample as a cathode in an inert gas atmosphere to generate a positively charged inert gas plasma, and the plasma collides with the sample surface. The atoms in the sample are sputtered by sputtering, but if the discharge current and discharge voltage are set, the edge drop on the sample surface can be suppressed more favorably, and the necessary sample surface can be sputtered. Accurate mass analysis of composition information for surface or depth analysis can be performed.

  Examples of the present invention are shown below, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

(Example 1)
Using a flat cell type glow discharge mass spectrometer as shown in FIGS. 2 and 3, glow discharge mass spectrometry was performed using a cylindrical and square copper plate as a sample to be measured. An insulating ring having a thickness of 0.5 mm was used. The discharge current was 2 mA and the discharge voltage was 1 kV. The sputtering rate on the sample surface was 0.25 μm / min.

(Example 2)
Glow discharge mass spectrometry was performed under the same conditions as in Example 1 except that the thickness of the insulating ring was 1.0 mm.

(Example 3)
Glow discharge mass spectrometry was performed under the same conditions as in Example 1 except that the thickness of the insulating ring was 1.5 mm.

(Example 4)
Glow discharge mass spectrometry was performed under the same conditions as in Example 1 except that the thickness of the insulating ring was 2.0 mm.

  For Examples 1 to 4, the discharge trace in the depth direction of the sample surface was observed with Thermo Fisher Scientific VG9000 type and Nu instruments ASTRUM, and the results are shown in FIG. Is shown in FIG. 5, Example 3 is shown in FIG. 6, and Example 4 is shown in FIG. 7. As can be seen from the results of Example 1 and Example 2 shown in FIG. 1 and FIG. 5, when the insulating ring thickness is 0.5 mm and 1.0 mm, the distance between the anode body and the sample surface is close and the sample is formed on the sample surface. The edge drop that was made was great. On the other hand, as can be seen from the results of Example 3 and Example 4 shown in FIGS. 6 and 7, when the insulating ring thickness is 1.5 mm and 2.0 mm, the distance between the anode body and the sample surface is sufficiently large. No edge drop was formed on the sample surface.

Claims (2)

A flat cell glow discharge mass spectrometer,
A discharge electrode, a sample holder for supporting a sample serving as a counter electrode, and an insulating ring for preventing an electrical short circuit between the discharge electrode and the sample holder,
A glow discharge mass spectrometer for performing glow discharge mass spectrometry without forming an edge drop on the surface of the sample after analysis, wherein the insulating ring has a thickness of 1.5 to 3.0 mm.   A glow discharge mass spectrometry method for performing mass analysis of a sample using the glow discharge mass spectrometer according to claim 1.

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