JP3790363B2 - Glow discharge optical emission spectrometer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glow discharge optical emission spectrometer that analyzes generated light with a spectroscope while sputtering a sample.
[0002]
[Prior art]
When a direct current or high frequency (high frequency of 13.56 MHz) is applied between two electrodes in an argon (Ar) atmosphere with a gas pressure of about 500 to 1300 Pa, glow discharge occurs and Ar ions are generated. Is done. The generated Ar ions are accelerated by a high electric field, collide with the cathode surface, and knock out the substances present there. This phenomenon is called sputtering, and the sputtered particles (atoms, molecules, ions) are excited in the plasma and emit light having a wavelength specific to the element when returning to the ground state. An analysis method for identifying elements by spectroscopically analyzing the emitted light is called a glow discharge emission spectroscopy method. There is an increasing demand for precise analysis of a so-called depth profile such as a change in the content of a component in the depth direction of a sample using an analyzer that embodies this glow discharge emission spectroscopic analysis method.
[0003]
[Problems to be solved by the invention]
However, in the conventional apparatus, since the sputtering of the sample and the excitation and emission of the sputtered particles are performed by a single power supply means, the discharge current value or the discharge power by the power supply means is to be analyzed accurately. If it is lowered and sputtered slowly, the light emission intensity also decreases, and the sensitivity as a device also deteriorates. That is, it is difficult to accurately analyze the depth profile.
[0004]
Accordingly, an object of the present invention is to provide a glow discharge emission spectroscopic analyzer capable of performing a precise analysis of a depth profile.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a glow discharge optical emission spectrometer according to claim 1 first applies a direct current or alternating voltage between a glow discharge tube having an anode tube and the anode tube and a sample. First power supply means for generating glow discharge and sputtering the sample with a discharge current value of 10 mA or less is provided. Moreover, the 2nd electric power feeding means which applies a high frequency voltage whose frequency is higher than the said 1st electric power feeding means in the range of 30-100 MHz between the said anode tube and a sample is provided. Furthermore, a detection means for measuring the intensity of light generated from the sample is provided.
[0006]
According to the apparatus of the first aspect, the sputtering of the sample is mainly performed by the first power supply means, and the excitation and emission of the atoms of the sputtered sample can be mainly performed by the second power supply means. Even if the current value is lowered and the sputtering is performed slowly, the emission intensity of the atoms of the sample by the second power feeding means is not lowered as much as the conventional one, and the sensitivity of the apparatus at a low sputtering rate is improved as compared with the conventional one. Therefore, a precise analysis can be performed on the depth profile. In the comparison of the frequency between the first power supply means and the second power supply means, when the first power supply means applies a DC voltage, the frequency is considered to be zero.
[0008]
A glow discharge emission spectroscopic analysis apparatus according to claim 2 is the apparatus according to claim 1 , wherein the voltage applied by the second power feeding means is modulated at a predetermined frequency, and the detection based on the magnitude of the voltage applied by the second power feeding means. Photometric means for calculating the difference between the detection signals of the means is provided. According to the apparatus of claim 2, the emission intensity due to the discharge of the first and second feeding means, is emitted component removal by discharge of the first feed means can be a disturbing line, the light emitting component due to discharge of the second power supply means only Is detected, so a more precise analysis is possible.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a glow discharge optical emission spectrometer according to an embodiment of the present invention will be described with reference to the drawings. First, the configuration of this apparatus will be described. As shown in FIG. 1, this apparatus uses a hollow anode type grim glow discharge tube 1 as a glow discharge tube. The Grimm glow discharge tube 1 includes a support block (a support portion with which the sample 6 is abutted and an insulating portion at the same time in this embodiment) 2 and an anode block 3 and a seal member 11 such as an O-ring. Are joined through. A hollow anode tube 3 d is formed integrally with the anode block 3, and this anode tube 3 d is inserted through the support block 2 and is close to the analysis surface (surface) 6 a of the sample 6. The sample 6 is pressed against the support block 2 mainly by the cathode block 4 through a seal member 11 such as an O-ring having an annular shape surrounding a portion to be analyzed on the analysis surface 6a.
[0010]
Thus, the opening of the inner space (glow discharge space) V of the support block 2 that accommodates the anode tube 3d by the sample 6 is sealed, and this inner space V is sealed by a vacuum exhaust device (decompression unit) (not shown). The first and second vacuum exhaust holes 3b and 3c are evacuated. Furthermore, the anode block 3 has an argon gas supply hole 3a, and the inside V of the tube is a rare gas atmosphere (500 to 1300 Pa) of argon. In addition, the sample 6 and the anode tube 3d are cooled via the cathode block 4 by introducing the coolant into the jacket from a coolant introduction path (not shown) of the cathode block 4 and feeding it to the coolant discharge path. .
[0011]
This apparatus includes first power feeding means 10 for generating a glow discharge by applying a DC voltage between an anode tube 3d and a sample 6 through an anode block 3 and a cathode block 4, respectively, and mainly sputtering the sample 6. ing. The first power supply means 10 is an AC blocking means for blocking inflow of high-frequency current from a DC power supply 16 and second power supply means 12 described later, for example, an LC series circuit of an inductance element (coil) 25 and a capacitance element (capacitor) 26. 17. Further, in this apparatus, a glow discharge is generated by applying a high frequency voltage between the anode tube 3d and the sample 6 through the anode block 3 and the cathode block 4, respectively, and is mainly sputtered by the first power supply means 10. A second power feeding unit 12 that excites atoms of the sample 6 to generate light S is provided. The second power supply means 12 includes a high frequency power source 18 of 40.68 MHz and a capacitance element (capacitor) 19 which is a direct current blocking means for blocking direct current flow by the first power supply means 10.
[0012]
The DC power supply 16 has a positive electrode that is grounded, and an inductance element 25 is connected between the negative electrode and a connection point between the capacitance element 19 of the second feeding unit 12 and the cathode block 4, and the inductance element 25 and the DC power supply 16 are connected. A capacitance element 26 is connected between the connection point between the two and the ground.
[0013]
Further, this apparatus is provided with detection means 14 for measuring the intensity of the light S generated from the sample 6. The detection means 14 includes a spectroscope 20 that splits the light S generated from the sample 6 and a photomultiplier tube 21 that measures the intensity of the split light. Furthermore, this apparatus modulates the voltage applied by the second power supply means 12 at a predetermined frequency, for example, 1 kHz, and calculates the difference in the detection signal of the detection means 14 depending on the magnitude of the voltage applied by the second power supply means 12. Means 15 are provided. The photometric means 15 has the following pulse wave generator 22, lock-in amplifier 23 and computer 24.
[0014]
The pulse wave generator 22 generates a pulse wave of the predetermined frequency (1 kHz) and transmits it to the high frequency power source 18 and the lock-in amplifier 23 of the second power feeding means 12. Receiving the pulse wave, the second power feeding means 12 modulates a high frequency voltage of 40.68 MHz applied between the anode tube 3 d and the sample 6 at 1 kHz. More specifically, for example, in the present embodiment, it is intermittent at 1 kHz. When the lock-in amplifier 23 receives the pulse wave of the pulse wave generator 22 and the detection signal from the detection means 14 is applied with the voltage A applied by the second power supply means 12 every 500 μsec, it is not applied. The difference A−B from the one B is calculated and transmitted to the computer 24. The computer 24 converts the analog signal from the lock-in amplifier 23 into a digital signal, stores and processes the converted digital signal, and displays it on the display means 27.
[0015]
Next, the operation of this apparatus will be described. Now, it is assumed that the depth profile of the component Cu of a certain sample 6 is precisely analyzed using this apparatus. First, the analysis surface 6a of the sample 6 is brought into contact with the support block 2, and the cathode block 4 is pressed and brought into conductive contact with the back surface 6e of the sample from below by a robot hand (not shown) and the sample 6 is held. In addition, when the inner space V of the support block 2 is evacuated by a decompression means (not shown) and is brought into a rare gas atmosphere (500 to 1300 Pa) of argon, the analysis surface 6a of the sample is also caused by the atmospheric pressure applied to the back surface 6e. Then, it is pressed against the support block 2 through the seal member 11 and closely contacts.
[0016]
Then, a DC voltage is applied between the anode tube 3 d and the sample 6 by the first power supply means 10, and at the same time, a high frequency voltage of 40.68 MHz is applied by the second power supply means 12. Then, first, glow discharge is generated by the DC voltage of the first power supply means 10 to generate positive ions of argon, and the sample 6 is sputtered mainly by the Ar ions. Furthermore, the atoms of the sputtered sample 6 are excited mainly by glow discharge due to the high-frequency voltage of the second power feeding means 12 to generate light S.
[0017]
Here, FIG. 2 shows the relationship between the current value of DC discharge and the emission intensity in the vicinity of the Cu atomic beam (324.8 nm), the conventional technique in which only a DC voltage is applied (left), the DC voltage and the high-frequency voltage ( 40.68 MHz) is compared with the present embodiment (right). According to this, at a high DC discharge current value of 12.5 mA or more, that is, a fast sputtering rate, there is not much difference between them, but at a low DC discharge current value of 10 mA or less, that is, at a slow sputtering rate, it is remarkable. There is a difference, and in particular, at 8 mA and 6 mA suitable for precise depth profile analysis, the light emission intensity is hardly measured by the conventional technique, but the light emission intensity can be measured in this embodiment. The emission intensity of the Cu atomic beam (324.8 nm) in this embodiment at 8 mA and 6 mA appears to be small in FIG. 2 because it is displayed in the same range as the emission intensity at 20 mA. It is strong enough for actual measurement.
[0018]
FIG. 3 shows the relationship between the DC discharge current value and the ratio of the emission intensity of the Cu atomic beam (324.8 nm) in the present embodiment to the emission intensity in the prior art. It can be seen that at 8 mA, 6 mA, and 4 mA, the present embodiment provides a light emission intensity that is 10 times or more that of the prior art. Such an operational effect is caused not only by slowing the sputtering as the direct current discharge current value is lowered, but also by suppressing the excitation and emission of particles of the sputtered sample. If discharge due to application of a high frequency voltage of 68 MHz is applied, such high frequency discharge does not contribute much to the sputtering of the sample because sufficient energy is not accumulated in Ar ions, but the sample sputtered by direct current discharge This is because it contributes to the excitation and emission of atoms.
[0019]
Moreover, such high-frequency discharges contribute to excitation and emission only with atomic beams that are excited with low excitation energy, and ion beams that are often not disturbed without high excitation energy. Not included. Therefore, for example, if a direct current discharge of 6 mA and a high frequency discharge of 40.68 MHz are used in an overlapping manner, only a specific atomic beam of Cu, for example, is sufficiently affected by a slow sputter rate without being affected by interference lines. Luminous intensity can be obtained.
[0020]
In order to obtain such effects, in the apparatus of the present embodiment, the discharge current value by the DC power supply 16 of the first power supply means 10 in FIG. 1 is 6 mA in this analysis, and the high frequency power supply 16 of the second power supply means 12 is used. The frequency is 40.68 MHz. This frequency is preferably higher than 13.56 MHz, and more preferably about 30 to 100 MHz. However, the applicable industrial frequency is only 40.68 MHz. Use this.
[0021]
Now, the light S generated from the sample 6 in this way passes through the window plate 13, enters the spectroscope 20 of the detection means 14, and is dispersed, and its intensity is measured by the photomultiplier tube 21. Here, the light S generated from the sample 6 generally means light having a wavelength specific to the element that is emitted when particles (atoms, molecules, ions) of the sputtered sample are excited and return to the ground state. However, in the present embodiment, in addition to the atomic beam generated by the excitation of the high frequency discharge of the second power supply unit 12, there may be some atomic beams generated by the excitation of the DC discharge of the first power supply unit 10. In some cases, an ion beam or the like serving as an interference line with respect to an atomic beam serving as an analysis line may be included.
[0022]
Therefore, in the present embodiment, the photometric means 15 makes the applied voltage by the second power feeding means 12 intermittent at a predetermined frequency of 1 kHz, and detection when the applied voltage by the second power feeding means 12 is applied or not applied. The difference between the detection signals of the means 14 is calculated. As a result, the light emission component due to the discharge of the first power supply means 10 that can be a disturbing line is removed from the light emission intensity due to the discharge of the first and second power supply means 10, 12, and only the light emission component due to the discharge of the second power supply means 12 is removed. Because it is detected, a more precise analysis is possible.
[0023]
In addition, since the voltage applied by the first power supply means 10 is a DC voltage, the apparatus according to the present embodiment can be easily configured based on an apparatus using a conventional DC power supply as the power supply means. However, when the applied voltage is a direct current voltage and when it is a high frequency voltage of 13.56 MHz, the conditions of sputtering, excitation, light emission, etc. by glow discharge are approximated. A high frequency voltage of .56 MHz may be applied. In this case, it can be easily configured on the basis of a device using a conventional high frequency power supply as a power feeding means. Here, in the industrial frequency, in addition to 13.56 MHz, 6.78 MHz or 27.12 MHz may be adopted on the condition that the frequency is lower than the high-frequency voltage applied by the second feeding unit.
[0024]
【The invention's effect】
As described above, according to the glow discharge optical emission spectrometer of the present invention, the sputtering of the sample is mainly performed by the first power supply means, and the excitation and emission of the atoms of the sputtered sample are mainly performed by the second power supply means. Even if the discharge current value or discharge power by the first power supply means is lowered and the sputtering is performed slowly, the emission intensity of the atoms of the sample by the second power supply means does not decrease as much as in the prior art, and the sensitivity of the apparatus at a low sputter rate is higher than in the past Will also improve. Therefore, a precise analysis can be performed on the depth profile. In addition, the luminous efficiency of the sample in the plasma is hardly affected by the composition change on the sample surface, and the depth profile can be analyzed more precisely.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a glow discharge optical emission spectrometer according to an embodiment of the present invention.
FIG. 2 is a diagram comparing the prior art (left) and the present embodiment (right) with respect to the relationship between the current value of DC discharge and the emission intensity in the vicinity of the Cu atomic beam (324.8 nm).
FIG. 3 shows the relationship between the DC discharge current value and the ratio of the emission intensity of the Cu atomic beam in the present embodiment to the emission intensity in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Glow discharge tube, 3d ... Anode tube, 6 ... Sample, 10 ... 1st electric power feeding means, 12 ... 2nd electric power feeding means, 14 ... Detection means, 15 ... Photometry means, S ... Light emitted from a sample.

Claims (2)

A glow discharge tube having an anode tube;
First feeding means for generating a glow discharge by applying a DC or AC voltage between the anode tube and the sample, and sputtering the sample with a discharge current value of 10 mA or less ;
A second power feeding means for applying a high-frequency voltage having a frequency higher than that of the first power feeding means in a range of 30 to 100 MHz between the anode tube and the sample;
A glow discharge emission spectroscopic analysis apparatus comprising: a detection unit that measures the intensity of light generated from a sample. In claim 1 ,
A glow discharge emission spectroscopic analysis apparatus comprising a photometric means for modulating a voltage applied by the second power feeding means at a predetermined frequency and calculating a difference between detection signals of the detecting means depending on the magnitude of the voltage applied by the second power feeding means. .

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