JPH03167450A - Discharge emission spectroscopic apparatus - Google Patents

Abstract

PURPOSE:To achieve high accuracy in a spectroscopic apparatus with high sensitivity being maintained by measuring a rotating electron current generated by the actions of an electric field and a magnetic field. CONSTITUTION:A spectroscopic apparatus has an cathode 10, an anode 20 and a magnetic-field setting means 30 for forming a magnetic field which is intersected with an electric field formed with the cathode 10 and the anode 20. The light emitting intensity of a material to be measured in a discharging space undergoes spectroscopic detection. Thus the material to be measured is determined and measured. That is, a rotating electron-current measuring means 40 measures the rotating electron current generated by the actions of the electric field and the magnetic field. Then the ratio between the rotating electron current obtained by the rotating electron-current measuring means 40 and the spectroscopic intensity is obtained. Thus the amount of existence (concentration) of the material to be measured can be obtained. In this way, the accuracy in quantitative analysis is improved in comparison with quantitative analysis that is performed based on only spectroscopic intensity.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention measures the amount of a substance to be measured by introducing the substance into a gas discharge space and spectroscopically detecting the discharge light emitted from the substance to be measured. Regarding the discharge emission spectrometer,
In particular, the present invention relates to a type of discharge emission spectroscopy (hereinafter referred to as crossed electromagnetic field type) that generates a rotating electron current in a space where an electric field and a magnetic field intersect, thereby increasing the discharge excitation of a substance to be measured.

[Prior Art] This type of discharge emission spectrometer is currently under development, and is described in detail in, for example, the following literature.

Vacuum, 31 [5] (1988), Sakai et al., “Detection of molecular beams by cold cathode discharge induced emission spectroscopy”, 9. 4
32-435 Such a crossed electromagnetic field type originally has high sensitivity, but has the drawback of low accuracy.

[Problem to be Solved by the Invention 1] This type of discharge emission spectrometer operates on the same principle as a crossed electromagnetic field type discharge ionization vacuum gauge. First, the operation of this discharge ionization vacuum gauge will be explained. This discharge ionization vacuum gauge is said to have low accuracy because the relationship between pressure and ion current (also called discharge current) is not completely proportional, and the theory is not clear. The present inventor believes that conventional discharge ionization vacuum gauges measure ion current, but the rotating electron current (corresponding to the anode current of hot cathode ionization vacuum gauges) that is the source of this ion current is measured. It is assumed that the accuracy is low because it was not measured. In other words, the pressure is not measured based on the ratio of the rotating electron current to the ion current, so it seems that the reliability is poor.

By the way, the following literature describes the measurement of the above-mentioned rotating electron current.

Journal of Applied Phys1c
s. 33 [6] (1982) (USA). W.
Knauer. "Mechanism of Penning discharge at low pressure" 1). 2
093-2099 In this document, a sensor coil is wound around the Penning discharge tube so that the rotating electron current can be measured indirectly. Then, by intermittently turning on and off the Penning discharge, the rotating electron current is intermittent, and the current induced in the sensor coil due to this intermittent interruption is measured. The rotating electron current is determined from the value of this induced current.

Taking this literature as a hint, the present inventor attempted to improve the crossed electromagnetic field type discharge ionization vacuum gauge to make it possible to constantly measure the rotating electron current, and also found that the ratio between this and the spectral intensity of the discharge emission was By determining this, we have developed a discharge emission spectrometer that can quantitatively measure the substance to be measured in the discharge space with high accuracy.

Therefore, the purpose of this invention is to improve the precision of this type of discharge emission spectrometer by regulating the rotating electron current at 11111 while maintaining the high sensitivity that is a feature of the crossed electromagnetic field type discharge ionization vacuum gauge. It's about trying.

[Means and effects for solving the problem] In order to achieve the above-mentioned object, the emission spectrometer according to the first invention of this application has the following features. First, this discharge emission spectrometer is equipped with a cathode, an anode, and a magnetic field setting means that forms a magnetic field that intersects the electric field created by the cathode and the anode, and the device is equipped with a The substance to be measured is quantitatively measured by spectroscopically detecting the luminescence intensity of the substance. Furthermore, as a new element particularly adopted in this invention, a means for measuring rotating electron current generated by the action of an electric field and a magnetic field is provided. By determining the ratio between the rotating electron current and the spectral intensity obtained by this measuring means, the amount (concentration) of the substance to be measured can be determined.

The Rizan that measures rotating electron current in addition to spectroscopic detection intensity and ion collector current is as follows.

The more gas molecules there are, the more light the discharge emits and the more ions it generates. However, the rotating electron current, which causes gas molecules to emit light and ionize, is not always constant; if the rotating electron current fluctuates, the same pressure,
Even in the presence of the same substance, the amount of light emitted changes. In contrast, in the present invention, quantitative analysis can be performed based on the ratio of rotating electron current and spectral detection intensity.
Compared to the conventional case where quantitative analysis is performed based only on spectral intensity, the accuracy of quantitative analysis is dramatically improved.

In addition, in this invention, "measuring rotating electron current"
This includes not only the direct measurement of the rotating electron current, but also the indirect measurement of the rotating electron current by measuring a physical quantity that depends on the rotating electron current.

In addition to the features of the first aspect 4 described above, the discharge emission spectrometer according to the second aspect of this application controls the rotating electron current to a constant value. Quantitative analysis is then performed by measuring the spectral intensity at this time.

For example, the rotating electron current can be kept constant by feeding back the measurement result of the rotating electron current to the anode voltage or to the current flowing through an electromagnet as a magnetic field setting means. If the rotating electron current is kept constant, quantitative analysis with a higher degree of precision can be performed.

In the discharge emission spectrometer according to the third aspect of this application, a voltage consisting of a direct current component and an alternating current component is applied between the cathode and the anode. In the conventional discharge emission spectrometer, only a direct current of several thousand volts was applied, but in this third invention, an alternating current is added to this.

By adding the alternating current, the voltage between the electrodes changes periodically, and the magnitude of the rotating electron current also changes accordingly. The fluctuating rotating electron current can be detected by electromagnetic induction effects. That is, by adding an alternating current component, it becomes possible to utilize the electromagnetic induction phenomenon as a "means for measuring rotating electron current."

[Example] Next, embodiments of the invention will be described with reference to the drawings.

Examples will be described in the following order.

stomach. First embodiment (using hot cathode magnet) Mouth. Second embodiment (using cold cathode magnet) c. Examples of various electrode changes Third embodiment (Utilization of Penning type discharge) E. To the measurement of rotating electron current using microwaves. Measurement of rotating electron current using a probe a. First Embodiment (Utilization of Hot Cathode Magnetron Type Discharge) FIG. 2 shows an example in which the discharge emission spectrometer of this invention is attached to a vapor deposition apparatus to control the vapor deposition rate. That is, a heating boat 2 is placed in a vacuum container 1, and a vapor deposition material is put therein, and the heating boat 2 is heated by a heater 3 to evaporate the vapor deposition phase material, thereby forming a thin film on the substrate 5. A sensor 6 of a discharge emission spectrometer is attached to the upper part of the vacuum container 1 to monitor the vapor deposited substance. A part of the evaporated material flies as shown by arrow 4 and enters sensor 6. The light taken out from the sensor 6 is spectrally detected by an analyzer 100 to measure the amount of the deposited material, and the measurement result is sent to the substrate 5.
To control the adhesion speed in Icheon. That is, the output signal of the analyzer 100 is fed back to the evaporation power source 9 through the signal line 8, and the temperature of the heater 3 is controlled to control the evaporation rate.

FIG. 1 is a block diagram of a first embodiment of the present invention, in which a portion of the sensor 6 is shown in a longitudinal section. FIG. 3 is a sectional view taken along the line ■--■ in FIG. 1.

In FIG. 1, the cathode 10 includes a hot cathode filament 11
and lead wires 12 and 13, most of which are covered with an insulating film 14.

The insulating film 14 prevents electrons from being emitted from the surface of the lead wire 13 and prevents the lead wire from coming into contact with other parts, thereby preventing the generation of dark current based on these. . The anode 20 includes a cylindrical anode bucket 21 and a lead wire 22. In this example, the anode electrode 21 has a diameter of 44 mm and a length of 48 mm. At the center of the anode electrode 21, two hot cathode filaments 11 are arranged.

The ion collector 50 is a disk-shaped ion collector 7ii.
It consists of a plum 51 and a lead wire 52. The ion collector electrode 51 is disposed near one end of the positive electrode 21 in the axial direction, perpendicular to the axis of the positive electrode 21 .

The above hot shade tub filament 11, positive plum electrode 21, and ion collector electrode 51 are housed inside a metal container 60. The container 60 includes a measuring tube 61 and a connecting flange 62.
It consists of The connection flange 62 is attached to a vacuum chamber or the like where emission spectrometry is to be performed. The shield 63 is a metal component with many holes, and is placed opposite the ion collector electrode 51 . This shield 63 prevents the dissipation of rotating electrons, which will be described later, and is applied with a negative potential.

The reason for the large number of holes is to ensure conductance,
This is to introduce the substance to be analyzed, mainly steam.

A thousand magnetic field setting stages 30 are arranged around the container 60. The magnetic field setting means 30 consists of two cylindrical permanent magnets 31 and a yoke 32 between them.

The magnetic field created by the permanent magnet 31 is generated by the hot cathode filament 11 and the Yooke Den Ffi. In the space 27 between the anode electrode 2
1 axis. On the other hand, this Denumema Space 27
In this case, the electric field is oriented in the radial direction of the Yangmei electrode 21. Therefore, the electric field and the magnetic field are orthogonal to each other in the interelectrode space 27. A discharge occurs in the space 27 where this electric field and magnetic field intersect,
The substances there are excited and emit light. That light is arrow 7
The light enters the spectrometer 103 through the introduction tubes 25, 101 and the window 102, and a separated spectrum can be obtained. By knowing the wavelength of each peak in this spectrum, it is possible to know the material of the substance that emitted light. Furthermore, by determining the intensity of each peak, the amount (concentration) of the emitting substance can be determined. In this embodiment, the strength of the magnetic field created by the permanent magnet 31 is 2500 Gauss at the hot cathode filament 11.

Recess 3 sandwiched between the inner surface of yoke 32 and two permanent magnets
3 houses a sensor coil 41. The sensor coil 41 is for measuring the intensity of a rotating electron current, which will be described later, and is wound with 2000 turns.

Next, the electrical structure of this discharge emission spectrometer will be explained.

A DC power supply 23 and an AC power supply 24 are connected in a row between the cathode 10 and the anode 20, and the cathode 10 side is grounded.

The output voltage of the DC power supply 23 is about 2 to 2.5 kV,
The output voltage of the AC power supply 24 has an amplitude (difference between maximum peak and minimum peak) of approximately 100V to 2kV. As shown in FIG. 4, the total voltage is such that the maximum voltage is about 3 kV and the minimum voltage is OV or more (preferably 500 V or more). There are no particular restrictions on the frequency of alternating current, but
A frequency of 10 to 1000 Hz is used.

A changeover switch 251 is provided between the anode 20 and the power sources 23 and 24, so that it is possible to switch to another power source 26. For example, in the case of a high pressure of 10-'Torr or more, a low-power, low-voltage power source can be used as the other power source 26.

Between the two lead wires 12 and 13 of the cathode 10, there is a filament heating power source 15, which heats the hot cathode filament 11.
A DC voltage of several volts is applied to.

The ion collector 50 is powered by a DC power supply 54.
A negative voltage of about -100V is applied.

The two lead wires of the sensor coil 41 are connected to each other after passing through a band pass filter 43 to form a loop. An ammeter 42 is connected to this loop. The bandpass filter 43 is for removing noise of a frequency different from the frequency of the alternating current applied to the anode from the output current of the sensor coil 41.

Next, the operation of this sensor 6 will be explained.

An anode voltage as shown in FIG. 4 is applied between the anode electrode 21 and the hot cathode filament 11.

The maximum value of the anode voltage is 3 kV, and the minimum value is 1 kV. The DC component of the applied voltage is 2kV, and the amplitude of the AC component is also 2kV.
It is. The frequency of the alternating current component is 300 Hz. Minus 100V is applied to the ion collector electrode 51. 5V is applied to both ends of the hot cathode filament 11. The shield 63 is set to -100V.

When this sensor 6 is operated under the above conditions, first,
Hot cathode filament 11. Thermionic electrons fly out and head toward the anode electrode 21. However, the trajectory of the electrons is aided by the action of the magnetic field, resulting in a rotational motion 17 as shown in FIG. As a result, the electrons rotate over an extremely long distance before reaching the anode electrode 21, colliding with gas molecules on the way and ionizing or exciting them. Due to this phenomenon, a discharge with high electron density occurs in the interelectrode space 27. Many of the ions generated by the ionization of gas molecules gather on the ion collector electrode 51, and this is detected by the current 153 as the ion collector current 1c. This value of ion collector current is 1000 times more extensive than a conventional BA gauge of comparable size. Therefore, it is no longer necessary to keep the minute current 8-1 constant, and the circuit for measuring the ion collector current becomes extremely inexpensive.

Since the anode voltage varies as shown in FIG. 4, the intensity of the rotating electron current also varies accordingly.

When the rotating electron current changes, the magnetic flux density passing through the sensor coil 41 changes, and an alternating current is induced in the sensor coil 41. This induced current is detected by an ammeter 42. Since the rate of change in the rotating electron current is proportional to the intensity of the rotating electron current, the rotating electron current 1r can be determined by determining the magnitude of the induced current.

When it is desired to measure the pressure P using this sensor 6, it is determined as follows. When the pressure inside the gauge bulb is P1 and the sensitivity coefficient of the vacuum gauge is S, the pressure P can be determined by the following equation.

P= (1/S) (I c / I r) When analyzing a material, the substance present in the discharge space can be known by examining the emission spectrum. Furthermore, the concentration of the substance present in the discharge space can be determined from the spectral intensity. Since the emission intensity changes approximately in proportion to the rotating electron current 1r, the emission intensity and Ir
If quantitative analysis is performed while measuring the ratio of , highly accurate analysis can be performed.

Next, another method of operating this sensor 6 will be explained. In the two operating methods, only the rotating electron current is measured, but it is also possible to go further and control the rotating electron current to a constant value. There are several ways to do this.

The first method is to feed back the output of the ammeter 42 to the DC power supply 23 and change the anode voltage so that the output of current=142 is constant. The second method is to feed back the output of the ammeter 42 to the voltage of the hot cathode filament power supply 54. A third method is to use an electromagnet instead of the permanent magnet 31 and feed back the output of the ammeter 42 to the current flowing through the electromagnet to change the strength of the magnetic field.

In this way, it is possible to not only measure the luminescence intensity and the ratio of the ion collector current to the rotating electron current, but also to control the rotating electron current to a constant level, making it possible to perform more accurate quantitative luminescence analysis and pressure measurement. become.

Note that in order to measure the rotating electron current, a loop including the hot cathode filament 11 may be used instead of the sensor coil 41 described above. That is, an ammeter 18 and a bandpass filter 19 are inserted into a loop made up of the lead wire 12, the filament 11, and the lead wire 13. Since an alternating current induced by the rotating electron current flows through this loop, the rotating electron current can be determined by measuring this induced current with the ammeter 18.

The role of the bandpass filter 19 is the same as that of the bandpass filter 43 described above.

The sensor 6 of FIG. 1 can also be used in nude form. That is, the cathode, anode, ion collector, etc. may be directly inserted into the container to be measured without using the container 60.

mouth. Second Embodiment (Utilization of Cold Cathode Magnetron Type Discharge) FIG. 5 is a longitudinal sectional view of a sensor 6 mainly showing only the electrode portion of the embodiment of the cold cathode magnetron type. In this example, the two-mentioned heat shade plum filament 1.
Instead, Reiinbaibo 16 is used. The advantage of a cold cathode is that it does not disturb the system under test compared to a hot cathode.

That is, the temperature of the system to be measured -L does not rise by i/{<<, and gas emission is also small. However, cold cathodes generally have poorer discharge stability than hot cathodes, and the discharge current tends to become unstable.

If this method of generation is applied to such a cold cathode magnetron type, the lack of reliability due to instability of discharge can be overcome. In other words, in addition to the spectral emission intensity and the ion collector current, this four-shot system also measures the rotating electron current that results from ionization, so if we calculate the ratio of the spectral emission intensity and the rotating electron current, we can Fluctuations can be offset. Therefore, if this invention is used, the advantages of a cold cathode can be maintained.
Reliability can be improved.

The differences when a cold cathode magnetron type is adopted will be explained below.

The electrical structure differs from that in Figure 1 in that the filament power supply 15 is not required, and the lead wire 1 at the other end
3 becomes unnecessary. The anode voltage is set to 1000-8000V.

In the case of a cold cathode, discharge tends to become unstable, and various noises are superimposed on the current induced in the sensor coil. Therefore, the bandpass filter 43 shown in FIG. 1 is of particular importance.

In FIG. 5, a sensor coil 41 is placed next to the permanent magnet 311.
1 is shown, however, the sensor film 41 may be arranged as shown in FIG. Of course, even with the hot cathode type shown in FIG. 1, the arrangement of the sensor coil 411 as shown in FIG. 5 can be selected. After all, the sensor coil can be placed anywhere as long as it can be coupled to the rotating electron current.

FIG. 6 shows an example in which the emission spectrum during aluminum vapor deposition was measured using the sensor shown in FIG. 5. In this spectrum, peaks at 309 and 396 nm, which are identified as the emission of aluminum atoms, are clearly observed. On the other hand, the emission wavelength of iron atoms in the stainless steel used as the cold cathode material in the range of 235 to 275 nm was hardly observed.

When the intensity of light of, for example, 309 nm in this emission spectrum is measured over time, a change in intensity appears over time, which is thought to be due to a change in the surface of the cold shade. However, when the ratio between this light intensity and the rotating electron current 1r was determined, it was found that there was almost no change in this ratio, and the accuracy of quantitative measurement based on this ratio was extremely excellent.

C. Example of modification of each electrode insertion The cathode or anode shown in FIG. 1 can be modified as follows.

FIG. 7 shows a hot cathode filament 111 in the form of a hairpin. However, when this cathode is used, the rotating electron current cannot be measured using the ammeter 18 shown in FIG. This is because the rate of change in the magnetic flux passing through the loop including the filament 111 is extremely small.

FIG. 8 shows a cylindrical anode electrode 2 with a slit 28 formed therein.
11 is shown. This anode electrode can be made to function as a one-turn coil by looping the lead wire as shown in FIG. That is, an alternating current is induced in this one-turn coil by the rotating electron current, and the rotating electron current is measured by measuring this with an ammeter 29.

FIG. 9 shows a rectangular anode electrode 212, which can also be used as a one-turn coil.

FIG. 10 shows a cold cathode magnetron type cathode structure with end plates. Disc-shaped end plates 161 and 162 are fixed to the cold cathode rod 16, and these are arranged near both ends of the anode electrode 21. A large number of holes are made in the end plate 161 on one side, similar to the shield 63 in FIG.

FIG. 11 shows an inverted magnetron type electrode structure. That is, the anode rod 213 is arranged at the center of the cylindrical cathode electrode 163. In the illustrated example, end plates 164 and 165 are provided at both ends of the cathode electrode 163 in order to prevent electrons from diffusing outside the discharge space. End plate 165
Make many holes in the hole.

two. The third embodiment (utilization of Penning type discharge) Figure 12 shows the following:
This invention is applied to Penning type discharge. Near both ends of the cylindrical anode electrode 21 are a pair of disc-shaped negatives tf! Electrodes 166 and 167 are arranged. A large number of holes are made in the cathode electrode 167. For information on the voltage applied between the anode and cathode and how to measure the rotating electron current,
This embodiment is basically the same as the embodiment shown in FIG.

Ho. Measurement of rotating electron current using microwaves FIGS. 13 and 14 show an example of detecting microwaves as another means for determining the rotating electron current. Although these figures show examples of a cold cathode type, a hot cathode type can also be used.

In FIG. 13, a microwave extraction electrode 70 is placed near one end of the anode electrode 21. In FIG. The microwave extraction electrode 70 consists of a coupling lube 71 and a transmission line 72. Since the intensity of the generated microwaves depends on the rotating electron current, the rotating electron current can be measured by detecting the intensity of the microwaves.

In FIG. 14, a cavity 214 is provided in the Yomei electrode 21, and a coupling loop 71 is arranged inside the cavity 214.

fart. Measurement of rotating electron current using a probe FIG. 15 shows an example in which a probe 90 is used as another means for measuring the rotating electron current. There is a small opening 216 in the anode electrode 21.
is formed, from which the probe electrode 91 is pushed into the discharge space. The probe electrode 91 is insulated in areas other than the discharge space. 193 and connected to an external instrument by a lead wire 92. By measuring the current, potential, etc. of this probe 90, the rotating electron current can be measured. The attachment position of the probe 90 can also be a position other than that shown in the drawings, if necessary.

Incidentally, when using either of the two types of rotating electron current measuring means described above, that is, a microwave or a probe, the AC power supply 24 shown in FIG. 1 is not necessarily required. This is because there is no need to vary the rotating electron current.

The respective embodiments, electrode structures, and rotating electron current measuring means shown in each figure can be used in combination with each other unless there is any particular disadvantage.

[Effect of striking] The discharge emission spectrometer according to the first invention of Chumyo measures the rotating electron current in a crossed electromagnetic field type discharge, and calculates the ratio of this to the spectral intensity, thereby detecting the Performs quantitative analysis of substances. Therefore, the following effects are achieved. Conventional discharge emission spectrometers using crossed electromagnetic fields have high sensitivity, but they measure only the spectral intensity, which has a drawback in measurement accuracy.In this invention, however, the ratio of the spectral intensity to the rotating electron current has been improved. As a result, measurement accuracy is significantly improved while maintaining high sensitivity.

In addition to the features of the first invention, the discharge emission spectrometer according to the second invention of this application controls the rotating electron current to a constant value, so it can be expected to further improve measurement accuracy.

In addition to the features of the first invention, the discharge emission spectrometer according to the third invention of this application applies a voltage consisting of a DC component and an AC component between the cathode and the anode. Therefore, the rotating electron current fluctuates periodically, and this rotating electron current can be measured using the electromagnetic induction phenomenon.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the first embodiment, Fig. 2 is a block diagram of a vapor deposition system using this invention as a vapor deposition rate monitor, Fig. 3 is a sectional view taken along the line ■-■ of Fig. 1, and Fig. 4 is A graph showing the anode voltage of the first embodiment, Fig. 5 is a sectional view of the main part of the second embodiment, Fig. 6 is a diagram showing an example of the emission spectrum, and Figs. Figure 12 is a cross-sectional view of the main part of the third embodiment. Figures 13 and 14 are illustrations of the microwave detection means. Figure 15 is a fourth diagram of the probe. be. 10... Cathode 20... Anode 23... DC power supply 24... AC power supply 30... Magnetic field setting means 40... Rotating electron current measuring means 103... Spectrometer

Claims (3)

[Claims] (1) It is equipped with a cathode, an anode, and a magnetic field setting means for forming a magnetic field that intersects the electric field created by the cathode and anode, and spectrally detects the emission intensity of the substance to be measured in the discharge space. What is claimed is: 1. A discharge light emission spectrometer for quantitatively measuring a substance to be measured, the discharge light emission spectrometer comprising means for measuring a rotating electron current generated by the action of the electric field and the magnetic field. (2) The discharge emission spectrometer according to claim 1, wherein the rotating electron current is controlled to be constant. (3) The discharge emission spectrometer according to claim 1, wherein a voltage consisting of a DC component and an AC component is applied between the cathode and the anode.