JPH09329552A - Glow discharge emission spectral analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glow discharge emission spectral analyzer capable of abstaining accurate analysis results irrespective of difference of a surface area of samples in analysis of unconductive samples. SOLUTION: This analyzer is provided with an anode block 1 having an anode valve 1d, a cathode plate 2 to which a sample 5 is fitted, and into which the anode valve 1d is inserted, and an insulation block 3, composed of an insulation substance, which is interposed between the anode block 1 and the cathode plate 2, and into which the anode valve 1d is inserted. An inward space V for housing the anode valve 1d is formed by the anode block 1, the insulation block 3, the cathode plate 2 and the sample 5 fitted on the cathode plate 2. Further, this embodiment comprises decompressing means 1b, 1c for drawing the inward space V in a vacuum, and power supplying means 8 for generating glow discharge in the inward space V by applying a high frequency voltage to between the anode block 1 and cathode plate 2 or between the anode block and the sample 5. The cathode plate 2 has a larger outer diameter than the sample 5, and a ratio d/e of the thickness d to a thickness e of the insulation block 3 is set to be 1/100 to 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow discharge emission spectroscopic analyzer for analyzing generated light while sputtering a sample.

[0002]

2. Description of the Related Art When a DC or high-frequency high voltage is applied between two electrodes in an argon (Ar) atmosphere at a gas pressure of about 4 to 10 Torr, a glow discharge occurs to generate Ar ions. The generated Ar ions are accelerated by a high electric field, collide with the surface of the cathode, and knock out substances existing there. This phenomenon is called sputtering. Sputtered particles (atoms, molecules, ions) are excited in plasma and emit light of a wavelength peculiar to the element when returning to the ground state. An analysis method in which the emitted light is separated by a spectroscope to identify elements is called a glow discharge emission spectral analysis method.

The glow discharge emission spectral analysis method described above is generally embodied by an analyzer using a hollow anode type grim glow discharge tube. In this grim glow discharge tube, an anode block and a cathode block, which are integrally formed with a hollow anode tube, are joined, and the inside of the tube is set to a rare gas atmosphere of argon (4 to 10 Torr). The sample is pressed in a gastight state directly or indirectly to the cathode block via a seal member, and the anode tube is close to the analysis surface on the surface of the sample. This glyme glow discharge tube applies a high voltage between the anode block and the sample to generate a glow discharge, and causes argon cations generated by the generation of the glow discharge to collide with the surface of the sample. Is to be sputtered.

By the way, the conventional glow discharge emission spectroscopic analyzer mainly targets a conductive sample,
A high DC voltage is applied between the anode block and the sample to generate glow discharge. On the other hand, in recent years, an analyzer which can analyze a non-conductive sample has been devised, and this analyzer generates a discharge plasma by applying a high frequency high voltage to the non-conductive sample, so that the sample is negatively charged. It is designed to apply a self-bias voltage. As this type of analyzer, one shown in FIG. 5 or FIG. 6 is known.

That is, the analyzer 20 shown in FIG. 5 is disclosed in US Pat. No. 5,028,133 and includes an anode tube 21.
An insulating block 22 made of an electrically insulating material is joined to the anode block 21 having a through a sealing member 23 in an airtight state, and the non-conductive sample 5 is inserted into the insulating block 22 via a sealing member 24. Then, the high frequency power source 8 applies a high frequency high voltage between the anode block 21 and the sample 5 to generate discharge plasma. On the other hand, the analyzer 30 of FIG.
It is disclosed in Japanese Patent No. 325035, and can analyze both conductive and non-conductive sample 5. In this analyzer 30, an anode block 31 and a cathode block 32 are joined with an insulating member 33 interposed therebetween, and an insulating isolator 37 having a contact member 34 on the surface of the cathode block 32 opposite to the anode block 31. Is attached in an airtight state only when the non-conductive sample 5 is analyzed. Further, the non-conductive sample 5 is connected to the contact member 34 by being attached to the isolator 37 in an airtight state, and a high frequency voltage is applied between the sample 5 and the anode block 31 through the contact member 34 by the high frequency power supply unit 8. Discharge plasma is generated.

[0006]

By the way, the sample 5 set in the analyzers 20 and 30 is the anode tube 21.
Although only a part facing a and 31a is sputtered for analysis, it is difficult to always form the sample 5 with the same overall size. However, in each of the analyzers 20 and 30 of FIGS. 5 and 6, even if the sample 5 is made of the same material, one surface including the analysis surface of the sample 5 (FIG. 6, FIG.
If the surface area of the upper surface 7 is different, the emission intensity changes according to the difference in surface area even if the same electric power is supplied, and an accurate analysis result cannot be obtained.

That is, in the analyzer 20 of FIG. 5, a high-frequency high voltage is directly applied to the sample 5, so that the insulating block 22 between the sample 5 and the anode block 21 causes the sample 5 to flow.
A stray capacitance C is generated between the anode block 21 and the anode block 21. This stray capacitance C is represented by C = εS / D, where D is the thickness of the insulating block 22, S is the surface area of one surface including the analysis surface of the sample 5, and ε is the dielectric constant of the insulating block 22. When the surface area S of the sample 5 to be analyzed becomes large, for example, as shown by the chain double-dashed line in FIG. 5, the stray capacitance C changes accordingly. Furthermore, sample 5 and anode block 21
The impedance Z between is Z = 1 / ωC = 1 / 2πfC, where ω is the angular frequency of the high frequency high voltage and f is the frequency.
Therefore, when the stray capacitance C becomes large as described above, the impedance Z becomes small. As a result, the high-frequency high voltage applied between the anode block 21 and the sample 5 has a loss that a part thereof leaks through the insulating block 22, so that the energy of the glow discharge plasma is not sufficiently accumulated, The glow discharge becomes insufficient, the luminous efficiency decreases, and the luminous intensity decreases.

On the other hand, in the analysis device 30 of FIG. 6, when the non-conductive sample 5 is analyzed, the sample 5 is replaced with the isolator 3.
It is supported by the conductive cathode block 32 through 7,
When this sample becomes large so as to protrude to the outside of the contact member 34 as shown by the chain double-dashed line in FIG. 7, for example, stray capacitance also occurs between the protruding portion and the insulating isolator 37. Since this stray capacitance changes according to the difference in the surface area of the sample 5 that directly faces the insulating isolator 37, light emission occurs according to the difference in the surface area of one surface including the analysis surface of the sample 5 as in the analyzer of FIG. The intensity changes.

Therefore, according to the present invention, an accurate analysis result can be obtained irrespective of the difference in the surface area of one side of the analysis surface of the sample, and high luminous efficiency can be obtained by efficiently applying a high frequency high voltage to the sample. It is an object of the present invention to provide a glow discharge emission spectroscopic analyzer capable of performing the above.

[0010]

In order to achieve the above object, a glow discharge emission spectroscopic analyzer according to the present invention comprises an anode block having an anode tube, a cathode to which a sample is attached and the anode tube is inserted. It consists of a plate and an insulator,
An insulating block which is interposed between the anode block and the cathode plate and through which the anode tube is inserted, and in which the anode tube is housed by the anode block, the insulating block, the cathode plate and the sample attached to the cathode plate. An inner space is formed, and a high-frequency voltage is applied between the anode block and the cathode plate or between the anode plate and the sample and a decompression means for evacuating the inner space. The cathode plate has an outer diameter larger than that of the sample, and the ratio d / e of the thickness d to the thickness e of the insulating block is 1/100. As a result, it is set to 9 or less.

In the above glow discharge emission spectroscopy analyzer, the sample is attached to the cathode plate when a high frequency voltage is applied between the anode block and the cathode plate or between the anode plate and the sample. And the cathode plate have almost the same potential. Here, the outer shape of the sample is contained within the outer shape of the cathode plate. Therefore, the stray capacitance generated becomes a constant value determined by the facing area and the facing distance between the anode plate and the cathode plate, and the same voltage is applied to the sample of the same material even if its outer diameter changes. In this case, since the emission intensities are the same, accurate analysis results can be obtained.

Further, since the ratio d / e of the thickness d of the cathode plate to the thickness e of the insulating block is set to 1/100 or more and 9 or less, the thickness required for the strength of the cathode plate (for example, 0.5 m).
m) or more and the thickness e of the insulating block is equal to or more than the thickness necessary for insulation (for example, 5 mm), and the total thickness d + e of the two causes increase in size of the device and increase in length of the anode tube. Since it can be set as large as possible within the evacuated range (for example, 50 mm or less), it is possible to suppress a decrease in the emission intensity of light from the sample due to the lengthening of the anode tube.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a glow discharge emission spectroscopic analyzer according to an embodiment of the present invention emits light of a wavelength peculiar to an element by sputtering using glow discharge, and is emitted from a grim glow discharge tube 10. The light L transmitted through the window plate 13 enters the spectroscope 15. The spectroscope 15 measures the entrance slit 14, the diffraction grating 16 that diffracts the light L incident from the entrance slit 14 at different diffraction angles according to the wavelength, the exit slit 17 that passes the diffracted light, and the intensity of the diffracted light. A photomultiplier tube 18 is provided.

FIG. 2 shows an example of the Grim glow discharge tube 10 in the analyzer of FIG. In FIG. 2, the grim glow discharge tube 10 has an anode block 1 and a cathode plate 2 both made of a conductive material such as copper, joined together via an insulating block 3 made of an insulating material such as resin or ceramic. ing. The anode block 1 is integrally formed with a hollow anode tube 1d, and the anode tube 1d is made up of an insulating block 3d.
Also, it is inserted through the cathode plate 2 and is close to the surface 5 a of the sample 5. The sample 5 is pressed against the cathode plate 2 by a sample holder 7 in a gas-tight manner via a seal member 6 such as an O-ring having an annular shape that can surround the analysis surface on the surface 5a. The outer diameter D2 of the cathode plate 2 is set larger than the outer diameter D5 of the sample 5. The cathode plate 2 is usually circular,
In addition to the circular shape, the sample 5 may be a triangular shape or a polygonal shape of a quadrangle or more. In that case, the outer diameter D5 of the sample 5 is the outer diameter of the circumscribed circle of the triangular shape or the polygonal shape.

Thus, the anode block 1, the insulating block 3, the cathode plate 2 and the sample 5 form an inner space (glow discharge space) V for housing the anode tube 1d. In addition, the first and second electrodes provided on the anode block 1
The inner space V is evacuated through the vacuum exhaust holes 1b and 1c. Further, the anode block 1 has an argon gas supply hole 1a, and the inside V of the tube is set to a rare gas atmosphere of argon (4 to 10 Torr).

This glyme glow discharge tube 10 applies a high frequency high voltage between a positive electrode block 1 and a negative electrode plate 2 by a high frequency power source (feeding means) 8 to generate a glow discharge, and is generally made of copper. The sample 5 is sputtered by applying a voltage to the sample 5 through the cathode plate 2 and causing argon cations generated by the generation of glow discharge to collide with the surface 5a of the sample 5. The insulating block 3 is cooled by the cooling water sent from the cooling water supply hole 3a to the cooling water discharge hole 3b. The sample 5 and the hollow anode tube 1d are cooled via the sample holder 7 by the cooling water supplied from the cooling water supply hole 7a of the sample holder 7 to the cooling water discharge hole 7b.

Next, the operation of the above configuration will be described. FIG.
When a high-frequency high-frequency voltage is applied from the high-frequency power source 8 between the anode block 1 and the sample 5 through the cathode plate 2, glow discharge is generated and argon cations are generated. The plasma generated by this glow discharge applies a negative self-bias voltage to the non-conductive sample 5. As a result, the generated Ar ions are generated in the sample 5 at a negative potential.
It collides with the analysis surface 5a of 1 and the analysis surface 5a is sputtered. As a result, the atoms that have been knocked out and separated from the analysis surface 5a of the sample 5 are excited by Ar ions or electrons, and emit element-specific light when returning to the ground state again.

Of the light from the sample 5, the light L having a divergence angle θ passes through the window plate 13. The divergence angle θ is the anode tube 1
a point on the analysis surface 5a located on the central axis of d and the anode tube 1
It is an angle formed by a straight line that connects two points on the inner circumference of the inner edge of d that face each other by 180 °. The light L transmitted through the window plate 13 is
It goes through the entrance slit 14 of FIG. 1 toward the diffraction grating 16 of the spectroscope 15. The diffraction grating 16 diffracts light having a predetermined wavelength, and makes the light enter a photomultiplier tube 18 through an exit slit 17. The photomultiplier tube 18 measures the intensity of the incident light.

By the way, in the glow discharge emission spectroscopic analyzer, the sample 5 is mounted by directly pressing it against the conductive cathode plate 2 by the sample holder 7, so that a high frequency high voltage is applied between the anode block 1 and the cathode block 2. Then, the sample 5 and the cathode plate 2 have almost the same potential. Further, the cathode plate 2 has an outer diameter larger than that of all the samples 5 to be analyzed, and the outer shape of the sample 5 does not extend radially outward from the outer shape of the cathode plate 2.
Therefore, the stray capacitance is generated only between the anode plate 1 and the cathode plate 2, and the stray capacitance is generated between the anode plate 1 and the cathode plate 2 regardless of the difference in the surface area of the surface 5a including the analysis surface of the sample 5. Is a constant value determined by the facing area and the facing distance. That is, the stray capacitance C
Is C, where Q is the facing area between the cathode plate 2 and the anode block 2, e is the distance between the cathode plate 2 and the anode block 2, that is, the thickness of the insulating block 3, and ε is the relative dielectric constant of the insulating block 3. = ΕQ / e, the stray capacitance C is always a constant value because the facing area Q and the thickness e of the insulating block 3 are invariable.

Further, the cathode plate 2 and the anode block 1
The impedance Z between is Z = 1 / ωC = 1 / 2πf
Since the stray capacitance C is represented by C and has a constant value as described above, the impedance Z also always has a constant value. Therefore, when analyzing the sample 5 of the same material, even if the area of the surface 5a of the sample 5 to be attached is different, the same high-frequency voltage is applied from the high-frequency power source 8 and the emission intensity is always the same. It is possible to obtain various analysis results. The high-frequency voltage is applied between the sample 5 and the anode plate 1 via the sample holder 7 as shown by a chain double-dashed line in FIG. 2 in addition to being applied between the anode plate 1 and the cathode plate 2 described above. The same analysis result as described above can be obtained even when the voltage is applied to.

As described above, it was confirmed from the experimental results that the same luminescence intensity can be obtained for the sample 5 made of the same material even if the surface areas are different. A brass with a thickness of 15 mm was used as a sample for this experiment. In the analyzer 10, the inner diameter a of the anode tube 1d was set to 4 mm, the distance between the anode block 1 and the cathode plate 2, that is, the thickness e of the insulating block 3 was set to 15 mm, and the thickness d of the cathode plate 2 was set to 5 mm. The luminescence intensity of zinc contained in brass, which is the result of this analysis, is shown in FIG.
Are shown by solid line characteristic curves. In this experiment,
As the brass of the sample, as shown in FIGS. 3 and 4, the surface area was (3.5 × 3.5) mm ² , (7 × 7) mm ² and (7 × 11) mm ²
Using three types of rectangular plates, the emission intensity is (3.5 × 3.5) mm
The luminous intensity of brass ² is shown as 100.

As is clear from FIGS. 3 and 4, when brasses having different surface areas are sputtered, the emission intensity of zinc and copper contained in the brasses at the same content is almost the same in each case. It became the same value. On the other hand, when the same three types of brass as described above are analyzed using the conventional analyzer shown in FIG. 5, the characteristic curves shown by the two-dot chain lines in FIGS. 3 and 4 are shown for comparison. In addition, the emission intensity decreased as the surface area of brass used as a sample increased.

Although the above experiment was conducted using conductive brass as the sample 5, the same analysis result can be obtained for the non-conductive sample.

In the analyzer 10 of FIG. 2, the ratio d / e between the thickness d of the cathode plate 2 and the thickness e of the insulating block 3 is d / e.
Is set to 1/100 or more and 9 or less. The basis of this numerical value will be specifically described. First, the thickness d of the cathode plate 2
Is required to have a strength of 0.5 mm or more. However, it is preferable that the thickness d of the cathode plate 2 be as thin as possible because the area facing the outer peripheral surface of the anode tube 1d becomes small and the stray capacitance becomes small. The thickness e of the insulating block 3 is
It is required to be 5 mm or more to maintain sufficient insulation. On the other hand, the total thickness of the cathode plate 2 and the insulating block 3 d + e
When the value exceeds 50 mm, the entire device 10 becomes large, and the anode tube 1d becomes long, the divergence angle θ of the light L from the sample 5 becomes small, and the emission intensity decreases.
The following is desirable. That is, 0.5 mm ≦ d ≦ 45 (≈50
(d + e) -5 (e)), 5mm ≦ e ≦ 50 (≒ 50 (d + e) -0.5
It falls within the range of (d)). Therefore, the thickness ratio d / e between the cathode plate 2 and the insulating block 3 is set to 0.5 mm / 50 mm (1/100) or more and 45 mm / 5 mm (9) or less.

The ratio d / e is preferably set to 1/100 to 5, more preferably 1/30 to 3, and even more preferably 1/10 to 2. Good. As a result, the cathode plate 2 has a required thickness d in terms of strength, and the anode block 1 and the cathode plate 2 are prevented from increasing in size of the entire apparatus 10 and the anode tube 1d.
Alternatively, it is possible to reduce leakage of the high frequency voltage applied to the sample 5 through the insulating block 3 as much as possible. As a result, the high voltage applied from the high-frequency power supply unit 8 is efficiently applied to the discharge space V through the conductive cathode plate 2, so that a glow discharge sufficient for analyzing the sample 5 is generated in the discharge space V. be able to.

[0026]

As described above, according to the glow discharge emission spectroscopic analyzer of the present invention, even if the outer diameter of the sample of the same material changes, the emission intensity becomes the same, and an accurate analysis result can be obtained. Obtainable. Also, while the cathode plate has the required thickness for strength, the thickness of the insulating block is prevented from becoming excessive while maintaining a thickness range that does not cause insulation failure, and the emission intensity accompanying the lengthening of the anode tube is increased. Can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an analyzer according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing an example of a glow discharge tube according to the same analyzer.

FIG. 3 is a characteristic diagram showing the relationship between the surface area of brass and the emission intensity of zinc contained in brass, showing the results of brass analysis by the same apparatus.

FIG. 4 is a characteristic diagram showing the relationship between the surface area of brass and the emission intensity of copper contained in brass showing the results of brass analysis by the same apparatus.

FIG. 5 is a vertical cross-sectional view showing a main part of a glow discharge tube in a conventional analyzer.

FIG. 6 is a vertical cross-sectional view showing a main part of a glow discharge tube in another conventional analyzer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Anode block, 1b, 1c ... Vacuum exhaust hole (pressure reducing means), 1d ... Anode tube, 2 ... Cathode plate, 3 ... Insulation block, 5 ... Sample, 8 ... High frequency power supply section (power feeding means), D2
... outer diameter of the cathode plate, D5 ... outer diameter of the sample, V ... inner space.

Claims (1)

[Claims] 1. An anode block having an anode tube, a cathode plate to which a sample is attached and the anode tube is inserted, and an insulator, which is interposed between the anode block and the cathode plate, and the anode tube And an insulating block through which the anode block, the insulating block, the cathode plate and an inner space for accommodating the anode tube are formed by the sample attached to the cathode plate, and the inner space is vacuumed. Depressurizing means for pulling, and a power feeding means for applying a high frequency voltage between the anode block and the cathode plate or between the anode plate and the sample to generate glow discharge in the inner space, the cathode plate Has a larger outer diameter than the sample,
The ratio d / e between the thickness d and the thickness e of the insulating block is
A glow discharge emission spectroscopic analyzer that is 1/100 or more and 9 or less.