JP3345188B2 - Glow discharge emission spectroscopy method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow discharge optical emission spectroscopy method and apparatus for analyzing generated light with a spectroscope while sputtering a sample.

[0002]

2. Description of the Related Art When a 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, and the sputtered particles (atoms, molecules, and 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 in which the emitted light is separated by a spectroscope to identify elements is called a glow discharge emission spectral analysis method. In such an analysis method, a sample or an apparatus is cooled for the purpose of stabilizing a light emitting state.

[0003]

By the way, the present inventors analyzed low melting point metals such as bismuth, solder and lead, and samples having an organic film (insulating film). Stable data could not be obtained.

[0004] After examining the cause, it is presumed that the temperature of the sample surface at the time of sputtering is higher than the melting point of such a low melting point metal, and that the sample surface is melted. That is, in such an analysis method, since the atomization of the sample is performed by the sputtering effect and is not performed by a thermal change, when the sample surface is melted, stable discharge does not continue,
Occasionally, a transition to arc discharge occurs or sputtering becomes extremely unstable. Therefore, stable data cannot be obtained.

On the other hand, it is presumed that the reason for the organic film is that the surface of the sample becomes higher than the temperature of thermal decomposition. That is, with respect to the organic film, the physical and chemical properties of the sample surface change due to melting or thermal decomposition of the sample surface, and the film is peeled off or the film is cracked. Therefore, stable data cannot be obtained.

Further, a sample is cooled by pressing a cooling device using cooling water against a surface of the sample opposite to the analysis surface and flowing a certain amount of cooling water having a constant water temperature into the cooling device. ing. In such a cooling means, even if the above-mentioned phenomenon such as the melting in the low melting point sample and the thermal decomposition of the organic film does not occur due to the cooling, the temperature of the analysis surface of the sample becomes longer than the sputtering time due to heat generated by sputtering. As the temperature rises, the sputtering rate gradually increases. As a result, the emission intensity gradually increases, so that the concentration distribution of the component elements of the sample cannot be measured accurately.

For example, FIG. 4 shows an analysis result of a sample having an organic film having a composition in which carbon (c) is distributed at a uniform concentration on the surface of a substrate having a composition having a uniform iron (Fe) concentration distribution. Where a is a characteristic curve of carbon and b is a characteristic curve of iron. In the figure, a correct characteristic curve is shown by a virtual line. When a cooling means having a constant cooling power as described above is used, the emission intensities of carbon and iron gradually increase with the elapse of the sputtering time, and the concentrations of carbon and iron move toward the inside of the sample. The measurement data is erroneous as if it were gradually increasing.

In the quantitative analysis of a sample, usually, a plurality of samples are cut out from a single sample object, and the determination is made based on an average value of the measured data. At this time, if the sizes of these samples vary, the heat capacities of the samples differ depending on the size of the shapes. Each temperature rise has a different result. Therefore, accurate quantitative analysis cannot be performed.

Accordingly, the present invention provides a glow discharge optical emission spectroscopy method and apparatus capable of performing not only analysis of a substance having a low melting point or a substance which is thermally decomposed but also highly accurate quantitative analysis. The purpose is to do so.

[0010]

In order to achieve the above object, a glow discharge emission spectroscopy method according to the present invention comprises an anode block, a support block, and a sample analysis surface.
Press the opposite side to place the analysis surface of the sample on the support block.
Grim glow discharge with cathode block pressed against
Using a tube, between the anode block and the cathode block
A glow for applying voltage and causing cations to collide with the sample to sputter the sample and analyze the sample based on the measured intensity of light generated from atoms excited by the cations or electrons. In the discharge emission spectroscopy method, the heat absorbing portion of the thermoelectric cooler of the thermoelectric cooler utilizing the Peltier effect is connected to the cathode block.
Press the lock on the surface opposite to the surface pressed against the sample
While cooling the sample by Rukoto, the temperature of the analytical surface of the specimen, there is 350 ° C. or less equal to or less than the melting point or below 130 ° C. of the samples were held at the pyrolysis temperature below a predetermined temperature of the sample To keep the sputtering rate constant
It is characterized by keeping .

Further, the glow discharge optical emission spectrometer according to the present invention comprises an anode block, a support block, and a sample separation unit.
Press the surface opposite to the analytical surface to support the analytical surface of the sample.
A cathode block pressed against the block;
Apply a voltage between the block and the cathode block to
The sample is swirled by bombarding the sample with cations.
Along with putting, the above cations or electrons are
Therefore, based on the measured intensity of light generated from the excited atoms,
Glow discharge optical emission spectroscopy
And an electronic cooling device that cools the sample by using the Peltier effect, and the temperature of the analysis surface of the sample is 350 ° C. or less.
A less melting or below 130 ° C. of the samples was
Temperature control means for controlling the electronic cooling device so as to maintain a constant temperature equal to or lower than the thermal decomposition temperature of the sample ;
Maintain a constant cutting speed, and
The heat absorption part of the thermoelectric cooling element
It is characterized in that it is pressed against the surface opposite to the pressing surface .

[0012]

According to the invention, the heat generated by sputtering is efficiently absorbed by the electronic cooling device having a high response speed utilizing the Peltier effect, and the temperature of the analysis surface of the sample having a low melting point is reduced. Since the temperature is kept below the melting point, the analysis surface of the sample does not melt at the time of sputtering, so that it is possible to analyze even such a substance having a low melting point.
In addition, since the temperature of the analysis surface of a sample that may cause thermal decomposition is maintained at a temperature equal to or lower than the thermal decomposition temperature of the sample by the same cooling means, the analysis surface does not thermally decompose during sputtering. Can be analyzed.

In addition, regardless of the size of the sample and the amount of heat generated by sputtering, the temperature of the analysis surface of the sample is
Since the control is performed so as to maintain a constant value that is set to be equal to or lower than the melting point of the sample or equal to or lower than the thermal decomposition temperature, the sputtering rate can always be kept constant. Therefore, quantitative analysis of the sample can be performed with high accuracy.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a glow discharge optical emission spectrometer according to one embodiment of the present invention.
The glow discharge optical emission spectrometer includes a grim glow discharge tube 4 that generates light having a wavelength specific to an element by sputtering on a sample 1 using a glow discharge, and a window plate that is emitted from the grim glow discharge tube 4 and emits light. And a spectroscope 10 into which the light L transmitted through 8 enters through the entrance slit 9. The spectroscope 10 includes a diffraction grating 11 for diffracting the incident light L at different diffraction angles according to the wavelength, an exit slit 13 for transmitting the diffracted light, and a photomultiplier tube 12 for measuring the intensity of the diffracted light. I have.

FIG. 2 is a configuration diagram showing in detail a main part including the grim glow discharge tube 4 in the analyzer of FIG. FIG.
The sample 1 has an organic film 2 such as a paint on which thermal decomposition may occur, for example, on a substrate 3 such as a plated steel plate. In this sample 1, the surface of the organic film 2, that is, the analysis surface 2a of the sample 1 is pressed air-tight against the support block 5 of the Grim glow discharge tube 4 via the O-ring 16, and the cathode opposite to the surface 2a Block 17 is pressed. The Grimm glow discharge tube 4 is of a generally used hollow anode type, and a support block 5 and an anode block 6 are joined via a Teflon washer 7 which is an insulator.
The anode block 6 has an argon gas supply hole 6a and first and second vacuum exhaust holes 6b and 6c.
Is a rare gas atmosphere of argon (4 to 10 Torr). A hollow anode tube 6d is formed integrally with the anode block 6, and this anode tube 6d penetrates the Teflon washer 7 and is close to the analysis surface 2a of the sample 1.

The grim glow discharge tube 4 generates a glow discharge by applying a high frequency or a DC high voltage from a power supply section 18 between the anode block 6 and the cathode block 17, and passes through the cathode block 17, which is generally made of copper. A negative voltage is applied to the sample 1, and cations of argon generated by generation of glow discharge collide with the analysis surface 2a of the sample 1, thereby sputtering the sample 1.

The support block 5 is provided with a jacket 5b of a cooling liquid K for cooling the support block 5. The coolant introduction passage 5a and the coolant discharge passage 5c communicate with the jacket 5b. As the cooling liquid K, for example, water containing ethylene glycol is used. After being cooled by a cooler (not shown), the cooling liquid K is introduced into the jacket 5b from the cooling liquid introduction path 5a, and is passed through the support block 5 to the sample 1 and the anode tube 6d.
To cool.

In the glow discharge optical emission spectrometer described above, the analysis surface 2a of the sample 1 is vacuum-sealed with an O-ring 16 embedded in the support block 5 and pressed against the support block 5, and the sample 1 is used to form a hollow anode tube. The inner space of the support block 5 that houses 6d is closed, and the inner space is evacuated.

Next, the operation of the above configuration will be described. FIG.
When a high-frequency high voltage of several hundred to several thousand volts is applied between the negative electrode block 17 and the positive electrode block 6 by the power supply unit 18, glow discharge is generated, and cations of argon are generated. The generated Ar ions collide with the sample 1, which is a cathode, and strike out atoms from the analysis surface 2a of the surface of the organic film 2. The knocked-out atoms are excited by Ar ions or electrons, and emit light unique to the element when returning to the ground state again. This light L passes through the window plate 8 and travels through the entrance slit 9 in FIG. 1 to the diffraction grating 11 of the spectroscope 10. This diffraction grating 11 diffracts light of a predetermined wavelength,
The light enters the photomultiplier tube 12 through the exit slit 13. The photomultiplier tube 12 measures the intensity of the incident light.

On the other hand, the organic film 2 shown in FIG. 2 is sputtered by the above-mentioned bombardment of Ar ions, and its thickness gradually decreases with time. Thus, the measured intensity is measured as the sputtering time elapses, and a spectrum with respect to the time elapse of the analysis element is obtained. From the spectrum, the element is analyzed by the following method. First, a plurality of standard samples whose concentrations are known are prepared in advance, the intensity of the light L is measured for each of them, and the relationship between the concentration and the intensity of the light L is obtained from the average value. Subsequently, the intensity of light L for the sample to be analyzed is determined, and the concentration of the element is determined based on the above relationship.

In this analysis method, since the sample 1 is sputtered, the temperature of the analysis surface 2a of the sample 1 rises. Therefore, in the present invention, when sputtering the sample 1, the temperature of the analysis surface 2a of the sample 1 is controlled so as to maintain a constant temperature equal to or lower than the thermal decomposition temperature of the paint forming the organic film 2. On the other hand, when the sample is a low melting point metal such as solder, tin, bismuth, and lead having a melting point of 350 ° C. or less, the temperature of the analysis surface 2a of the sample 1 is maintained at a constant temperature equal to or lower than the melting point of the sample 1. Control.

Next, the cooling means for maintaining the sample 1 at a required constant temperature as described above will be described in detail. FIG.
In FIG. 2, a heat absorbing portion (cold junction portion) 20a of a well-known electronic cooling element 20 is pressed against a surface of the cathode block 17 opposite to a surface pressed against the sample 1, and a heat radiating portion of the electronic cooling element 20 is formed. A heat exchanger 21 is connected to the hot junction portion 20b.
A control voltage is applied to the electronic cooling element 20 from a control power supply 22 through a filter circuit 23. The electronic cooling element 20, the heat exchanger 21, the control power supply 22, and the filter circuit 23 use the Peltier effect to make the cathode block 17
An electronic cooling device 24 that cools the sample 1 through the above is configured.

The electronic cooling device 24 is controlled by a temperature control means 25 so that the temperature of the analysis surface 2a of the sample 1 is maintained at a constant value below the melting point of the sample 1 or below the thermal decomposition temperature. The temperature control means 25 controls the analysis surface 2a of the sample 1.
Is measured by a temperature sensor 25 such as a thermocouple, and the measured temperature data c is input to an error amplifier 29 via a filter circuit 27 and an insulation circuit 28 such as an isolation amplifier. The error amplifier 29 compares the measured temperature data c with the set temperature data d set in advance by the temperature setting unit 30, and outputs a control signal e obtained by amplifying the difference to the control power supply 22. The control power supply 22 varies the voltage applied to the electronic cooling element 20 so that the control signal e becomes zero. The low-pass filter circuits 23 and 27 and the insulating circuit 28 are provided to exclude the influence of high voltage and high frequency from the power supply unit 18 when measuring the temperature of the analysis surface 2a of the sample 1.

The operation of the cooling means will be described. When electrons flow from one thermoelectric semiconductor to the other thermoelectric semiconductor joined by a metal electrode, the thermoelectric cooling element 20 absorbs heat at the heat absorbing portion 20 a by the Peltier effect, and
0b, heat is generated, and heat is transferred from the heat absorbing section 20a to the heat radiating section 20a.
Pumped to b. That is, in the heat absorbing section 20a,
As the electrons transition from the low energy state to the high energy state, the vibrational energy of the surrounding crystal lattice is absorbed by the electrons in the form of heat, and as a result, the temperature is reduced, so that the cathode block 17 is cooled.

On the other hand, in the heat radiating portion 20b, electrons are transferred to the heat absorbing portion 2b.
0a, the electrons that have absorbed the lattice vibration energy in the heat absorbing portion 20a shift from a high energy state to a low energy state, and give the surplus energy to the surrounding crystal lattice, and the vibration energy of the lattice increases. As a result, the temperature rises, and extra heat is released from the radiator 20b to the outside air through the heat exchanger 21. The energy for causing the flow of electrons is supplied by applying a voltage from the control voltage 22.

In the above embodiment, the cathode block 17 is cooled by the electronic cooling element 20 and the sample 1 is cooled through the cathode block 17.
The temperature of the analysis surface 2a is measured by the temperature sensor 26, and the measured temperature data c is compared with the set temperature data d to feedback-control the temperature of the analysis surface 2a. Table 1 below shows actual measured values of the measured temperature of the cathode block 17 and the measured temperature of the analysis surface 2a of the sample 1 at this time.

[0027]

[Table 1]

In Table 1, the temperature measuring point is the cathode block 17, and the temperature measuring point is the analysis surface 2 a of the sample 1.
As shown in Table 1, the temperature of the cathode block 17 is determined to be substantially constant according to the control voltage value V of the control power supply 22 and the voltage application time, and the analysis surface of the sample 1 is determined according to the temperature of the cathode block 17. The temperature of 2a is determined almost constant.
Therefore, in the error amplifier 29, the temperature measurement point (analysis surface)
Is compared with the temperature set on the analysis surface 2a by the temperature setting unit 30, and a control signal e is output based on the difference. Further, the cathode block 17 is formed of a material having a small heat capacity and a high thermal conductivity, and the electronic cooling element 20 has a high response speed. As a result, heat generated by sputtering on the analysis surface 2a of the sample 1 is efficiently and quickly absorbed by the electron cooling element 20 via the cathode block 17, and the temperature of the analysis surface 2a of the sample 1 is set by the temperature setting unit 30. Feedback control is accurately performed so that the temperature is always constant.

Therefore, for example, in the case of paint,
Since thermal decomposition occurs at 130 ° C., the temperature of the analysis surface 2a is set to 1
Maintain a constant temperature of 30 ° C. or less. On the other hand, since the melting point of a low melting point metal such as bismuth is 271 ° C., in this case, the temperature of the analysis surface 2a of the sample 1 is set to 271 ° C.
Maintain the following constant temperature. As a result, even if the sample 1 is likely to undergo thermal decomposition, the sample 1 is not thermally decomposed, while the sample 1 having a low melting point is not melted. Can also be analyzed.

In addition, the temperature of the analysis surface 2a of the sample 1 is controlled so as to always maintain a constant value irrespective of the size of the shape of the sample 1 and the amount of heat generated by sputtering. Therefore, the sputtering rate can always be kept constant. For example, FIG. 3 shows the measured values of the same sample 1 as actually measured in FIG. 4, where A is a characteristic curve of carbon and B is a characteristic curve of iron. Each of the characteristic curves A and B has a uniform density distribution, and accurately indicates the actual density distribution. Therefore,
The quantitative analysis of the sample 1 can be performed with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram showing a main part of the analyzer in detail;

FIG. 3 is a characteristic diagram showing an actual measurement result by the analyzer.

FIG. 4 is a characteristic diagram showing a measurement result by a conventional analyzer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sample, 2a ... Analysis surface, 24 ... Electronic cooling device, 25 ...
Temperature control means.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Kimi Yamamoto 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Works, Steel Research Laboratory JP-A-7-120394 (JP, A) JP-A-60-8865 (JP, U) JP-A-59-54840 (JP, U) JP-A-60-17427 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 21/62-21/74 JICST file (JOIS)

Claims (2)

(57) [Claims] An anode block, a support block, and a sample
Press the surface opposite to the analysis surface of
A grip with a cathode block pressed against a support block
The above anode block and cathode block were
The sample is sputtered by applying a voltage to the sample and causing the cations to collide with the sample, and the sample is sampled based on the measured intensity of light generated from atoms excited by the cations or electrons. in glow discharge emission spectroscopic analysis method for analyzing a, electronic cooling of the electronic cooling device utilizing the Peltier effect
The surface where the heat absorbing part of the element is pressed against the sample of the cathode block
While cooling the sample by pressing it against the surface on the opposite side, the temperature of the analysis surface of this sample is set to 350 ° C. or less.
And the temperature is below the melting point of the sample or below 130 ° C.
To a constant temperature below the pyrolysis temperature of the sample .
A glow discharge emission spectroscopy method characterized by maintaining a constant putting speed . 2. An anode block, a support block, and a sample
Press the surface opposite to the analysis surface of
A cathode block pressed against the support block,
Apply a voltage between the anode block and the cathode block,
In a glow discharge emission spectrometer, which collides cations with the sample to sputter the sample and analyze the sample based on the measured intensity of light generated from atoms excited by the cations or electrons. An electronic cooling device that cools the sample by using the Peltier effect; and a temperature of an analysis surface of the sample is 350 ° C. or less and a melting point or less of the sample or 130 ° C. or less and a thermal decomposition temperature of the sample or less. Temperature control means for controlling the electronic cooling device so as to maintain a constant temperature of , the sputtering speed
Degree, the heat absorption part of the electronic cooling element of the electronic cooling device is
Press the cathode block on the surface opposite to the surface pressed against the sample.
A glow discharge optical emission spectrometer characterized by being attached .