JP3818162B2 - Electron beam irradiation processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron beam irradiation processing apparatus that performs curing, improvement of material quality, sterilization, and the like of printed paints and semiconductor materials by irradiating an electron beam, and in particular, controls the output of an electron beam emitted from an electron tube. The present invention relates to an electron beam irradiation processing apparatus according to an improvement of control means.
[0002]
[Prior art]
Usually, the electron beam irradiation processing apparatus is provided with a control means for controlling the electron beam emitted from the electron beam tube to output a predetermined amount of electron beam by performing feedback control.
[0003]
FIG. 5 is a diagram showing an example of an electron beam irradiation processing apparatus provided with such a control means.
In this device, a direct current high voltage supplied from a direct current high voltage power source is applied between the filament and flange of the electron beam tube and the electron beam exit window to measure the tube current flowing as shown by the broken line in the figure, and the measurement result By controlling the filament power supply or grid power supply based on the above, the current flowing through the filament and the grid voltage applied to the grid are controlled to control the tube current constant, thereby controlling the electron beam output constant. Yes.
[0004]
Here, the reason why the tube current changes may be that the resistance value changes due to thermal degradation or deformation of the filament. By adding the control means as described above, the tube current can be maintained and controlled constant regardless of the change in the resistance value.
[0005]
FIG. 6 is a diagram showing an example of an electron beam irradiation processing apparatus provided with a control means different from that shown in FIG.
[0006]
In this apparatus, the electron beam emitted from the electron beam exit window is measured by the current detection unit and the current measurement unit, the filament power supply is controlled based on the measurement result, and the electron beam output is controlled to be constant.
[0007]
Japanese Patent Laid-Open No. 2001-221898 is known as a known technique relating to this device, but the advantage of this type of device is that an electron beam emitted from an electron beam emission window by a current detection unit and a current measurement unit. The output is directly detected and measured.
[0008]
[Problems to be solved by the invention]
However, in the electron beam irradiation processing apparatus shown in FIG. 5, when the shape of the electron beam changes due to thermal deformation or electrostatic charging of components inside the electron beam tube, the number of electron beams that are not emitted from the electron beam emission window increases. In such a case, there is a problem that the electron beam output cannot be kept constant even if the tube current is kept constant.
[0009]
Furthermore, the electron beam exit window increases or decreases in thickness due to the reaction with the electron beam irradiation atmosphere gas, and accordingly, the electron dose transmitted through the electron beam exit window of the electron beam increases or decreases, and the tube current and the electron beam output There is a problem that the electron beam output cannot be kept constant even if the tube current is kept constant.
[0010]
Moreover, in the electron beam irradiation processing apparatus shown in FIG. 6, it is necessary to capture a part of the electron beam output by the current detection unit, and there is a problem that a part of the electron beam that can be irradiated to the object to be processed is lost. According to the knowledge of the present inventors, in order to stably detect an electron beam and obtain a predetermined stable and constant electron beam output, it is necessary to capture about 20 to 30% of the electron beam.
[0011]
Furthermore, since the current detection unit must be disposed in the vicinity of the electron beam exit window, the object to be processed cannot be brought close to the electron beam exit window. Therefore, when an electron beam is irradiated at atmospheric pressure, the electron beam is absorbed and scattered by the atmospheric pressure between the electron beam exit window and the object to be processed and attenuated. In the embodiment disclosed in the above Japanese Patent Laid-Open No. 2001-221898, the distance between the electron beam exit window and the current detector is 5 mm, and the distance to the object to be processed at this time requires about 10 mm. Absorption and scattering by the atmosphere will be very large.
[0012]
Furthermore, this apparatus has a problem that the sensitivity of the current detector changes due to long-term use and the electron beam output changes.
[0013]
Furthermore, in this apparatus, when irradiating under reduced pressure conditions, atmospheric gas plasma is generated. Therefore, detection at the current detector becomes unstable due to current from the atmospheric gas plasma, resulting in fluctuations in the electron beam output. In addition, since the state of the atmospheric gas plasma changes depending on the pressure of the atmospheric gas, there arises a problem that the output of the electron beam varies depending on the pressure of the atmospheric gas.
[0014]
Furthermore, when contaminants generated from the object to be processed adhere to the current detection unit, the sensitivity of the current detection unit changes, and there is a problem that the electron beam output changes.
[0015]
The object of the present invention is to consider the difference between the tube current flowing through the electron beam tube and the current flowing from the electron beam emitting portion of the electron beam tube to the ground in view of various problems in the conventional electron beam irradiation processing apparatus as described above. An object of the present invention is to provide an electron beam irradiation processing apparatus capable of outputting a constant electron beam that is stable over a long period of time by providing a means for detecting.
[0016]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
The first means is an electron beam irradiation processing apparatus comprising: an electron beam tube including an electron beam emitting unit that transmits and transmits an electron beam; and a direct current high voltage power source that applies a direct current high voltage to the electron beam tube. The electron beam emitting portion is made of a conductive member, and electrically insulates between the electron beam emitting portion and the low voltage portion of the DC high voltage power source, and also flows current between the electron beam emitting portion and the low voltage portion. And an ammeter for measuring the tube current flowing in the electron beam tube, and the current flowing in each ammeter so that the difference between the current values measured by both ammeters is constant. It is characterized in that a control means for controlling is provided.
The second means is the first means, wherein the control means controls a traveling power of electrons generated by a filament power source for generating thermionic electrons from the filament of the electron beam tube and / or the grid of the electron beam tube. The grid power supply is controlled to control the current flowing through each ammeter so that the difference between the current values measured by the two ammeters is constant.
[0017]
The third means is provided with display means for notifying that an abnormal state is present when the difference between the current values measured by the two ammeters exceeds a predetermined range in the first means or the second means. It is characterized by that.
[0018]
A fourth means is an electron beam irradiation processing apparatus comprising: an electron beam tube including an electron beam emitting unit that transmits and transmits an electron beam; and a direct current high voltage power source that applies a direct current high voltage to the electron beam tube. The electron beam emitting portion is made of a conductive member, and electrically insulates between the electron beam emitting portion and the low voltage portion of the DC high voltage power source, and also flows current between the electron beam emitting portion and the low voltage portion. And an ammeter that measures the tube current flowing in the electron beam tube, and when the difference between the current values measured by the two ammeters exceeds a predetermined range, it is in an abnormal state. It is characterized in that a display means for informing is provided.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a configuration for explaining the basic principle of an electron beam irradiation processing apparatus according to the present invention.
In the figure, 1 is an electron beam tube, 11 is a filament for emitting thermoelectrons, 12 is a grid for accelerating and controlling electrons emitted from the filament 11, 13 is a flange of the electron beam tube 1, and 14 is an electron beam tube. 1 is an electron beam exit window through which an electron beam is transmitted and emitted to the outside, 2 is a filament power supply, 3 is a filament power transformer, 4 is a grid power supply, 5 is a grid power transformer, and 6 is a current for measuring a tube current flowing through the electron beam tube. A total of 7 is a DC high-voltage power supply for supplying a DC high voltage to the electron beam tube 1 with one end connected to the high voltage application unit of the electron beam tube 1 and the other end connected to the ground.
[0020]
In this electron beam irradiation processing apparatus, the thermoelectrons generated in the filament 11 are drawn out to the electric field concentration portion by a high voltage by the grid 12 and then accelerated toward the electron beam exit window 14 to reach the electron beam exit window 14. Is configured to do.
[0021]
Here, the flange 13 and the electron beam emission window 14 constitute an electron beam emission part as a whole, and these are constituted by a conductive member. The electrons that have reached the electron beam exit window 14 are divided into those that pass through the electron beam exit window 14 and those that are absorbed by the electron beam exit window 14 at a rate corresponding to the acceleration voltage. A slight amount of electrons is absorbed not by the electron beam exit window 14 but by the flange 13.
[0022]
The current flowing through each part of the electron beam irradiation processing apparatus will be described. It is assumed that the tube current is It, the current flowing as an electron beam is Ieb, the current absorbed in the flange 13 and the electron beam exit window 14 is Is, and the leakage current is Im. The tube current It is expressed by the following equation.
It = Ieb + Is + Im (1)
Furthermore, the leakage current Im includes a leakage current Im ₁ flowing through the glass wall surface of the electron beam tube 1, a leakage current Im ₂ in the electron beam tube 1 caused by deterioration of the degree of vacuum in the electron beam tube 1 due to long-term use, an electron beam exit window 14 and the recombination current Im ₃ of the secondary electrons generated in the flange 13, the discharge current Im ₄ leaking from the high voltage application part of the electron beam tube 1 through air or insulating gas, etc. It is represented by the general formula below.
Im = Im ₁ + Im ₂ + Im ₃ + Im ₄ (2)
Note that these leakage currents Im ₁ , Im ₂ , Im ₃ , and Im ₄ are relatively small compared to the currents Ieb and Is, but all these leakage currents Im are not emitted from the electron beam exit window. 14 and the flange 13 are absorbed.
[0023]
When the equation (1) is rewritten, the current Ieb output as the electron beam is expressed by the following equation.
Ieb = It− (Is + Im) (3)
As described above, the current (Is + Im) represents the sum of the currents flowing through the flange 13 and the electron beam emission window 14 constituting the electron beam emission part, so that the tube current It and the flange 13 and the electron beam emission window are displayed. By knowing the sum total (Is + Im) of the currents flowing through 14, the current Ieb output as an electron beam can be known.
[0024]
FIG. 2 is a diagram showing the configuration of the electron beam irradiation processing apparatus according to the present invention, in which the holding part structure of the electron beam tube 1 is shown in detail.
In the figure, 20 is a decompression chamber, 21 is interposed between the flange 13 of the electron beam tube 1 and the decompression chamber 20, and is an insulator provided to block current flowing from the flange 13 through the decompression chamber 20 to the ground. , 22 is an O-ring provided between the flange 13 and the insulator 21, 23 is an O-ring provided between the insulator 21 and the decompression chamber 20, and 24 is provided between the flange 13 and the ground for measuring current (Is + Im). The ammeter 25 is a control unit that controls the filament power supply based on the current detected by the ammeter 6 and the ammeter 24 so as to maintain the current Ieb output as the electron beam at a predetermined value. It is.
Other configurations correspond to the same reference numerals shown in FIG.
Here, as the insulator 21, ceramic, glass, resin, or the like is used, and the decompression chamber 20 is made of SUS.
[0025]
In this electron beam irradiation processing apparatus, when the filament power source 2 and the grid power source 4 are operated and a DC high voltage is applied from the DC high voltage power source 7 to the electron beam tube 1, an electron beam is emitted from the electron beam exit window 14 and processed. Objects can be irradiated. When an electron beam is emitted from the electron beam exit window 14, the current flowing into the flange 13 together with the electron beam is blocked by the insulator 21 and cannot flow to the ground via the decompression chamber 20, but between the flange 13 and the ground. As a result, the sum (Is + Im) of the current flowing into the flange 13 by the ammeter 24 can be measured. On the other hand, the tube current It is measured by the ammeter 6, and the current measured by the ammeter 24 and the ammeter 6 is input to the control unit 25. The control unit 25 controls the filament power supply 2 so that the current Ieb = It− (Is + Im) output as an electron beam is maintained at a predetermined value.
[0026]
Although the case where the filament power source 2 is controlled has been described here, the grid power source 4 may be controlled instead of controlling the filament power source 2, or both may be controlled simultaneously. Needless to say.
[0027]
FIG. 3 is a diagram showing the configuration of the electron beam irradiation processing apparatus according to the present invention, showing the control system in detail.
In the figure, the ammeters 6 and 24 show cases where currents are detected using Hall elements, and currents It and (Is + Im) detected by the Hall elements are respectively current amplifiers 251 and 251 of the control unit 25. 252 is configured to input. The respective currents amplified in the current amplifiers 251 and 252 are converted into voltages by the current-voltage converters 253 and 254, and both voltages correspond to the ratio x ₁ = (Is + Im) ₁ / It ₁ in the arithmetic unit 255. An operation is performed. Further, in the calculation unit 255, the calculation formula x ₁ = (Is + Im) ₂ / It ₂ based on the obtained ratio x ₁ and the output current Ieb _{0 of the} electron beam set and input in accordance with the electron beam output to be output = Based on a set value corresponding to It ₂ − (Is + Im) ₂ , a value corresponding to the tube current It ₂ = Ieb ₀ / (1−x ₁ ) to be corrected is obtained, and the tube current It is calculated as It ₂ = Ieb. _A control signal is output so that ₀ / (1-x ₁ ). The control signal output from the calculation unit 255 is subjected to gain adjustment by the gain adjuster 257 after an unnecessary frequency component is removed by the filter 256, and is output as a control signal to the PWM control circuit 202 of the filament power supply 2. In the filament power supply 2, the PWM control circuit 202 outputs a pulse width modulation signal controlled according to the control signal at a frequency given by the reference oscillator 201. The drive circuit 203 is driven by the pulse width modulation signal and controls the filament current flowing through the filament 11.
[0028]
Here, the reference oscillation frequency of the reference oscillator 201 is 80 kHz, the drive circuit 203 adopts a push-pull method, and it has been confirmed that a stable electron beam output can be obtained in the range of the tube current of 10 μA to 1000 μA.
[0029]
FIG. 4 is a table for explaining how the electron beam current Ieb radiated from the electron tube is controlled and corrected when it changes for some reason.
In Example 1 of the same table, the current (Is + Im) ₀ = 225 μA measured by the ammeter 24 and flowing from the electron beam emitting portion to the ground when normal, the tube current It ₀ = 300 μ measured by the ammeter 6, based on this What was in the normal state of the electron beam current Ieb ₀ = (300−225) μA = 75 μA calculated in this way, the current measured by the ammeter 24 changes to (Is + Im) ₁ = 230 μA for some reason. As a result, the normal electron beam current Ieb ₀ = 75 μA is reduced to the electron beam current Ieb ₁ = (300−230) μA = 70 μA, and an abnormal state is reached. According to the present invention, It ₂ = Ieb ₀ / (1-x ₁ ) = 75 / (1-230 / 300) = 321.4 μA, similarly (Is + Im) ₂ based on the calculation formula described above. = Ieb ₀ · x ₁ / (1−x ₁ ) = 75 · 230/300 (1-230 / 300) = 246.4 μA, and the control signal from the control unit 25 so that these currents are obtained. Is output. As a result, correction control is performed so that the tube current It ₂ = 321.4 μA and the current (Is + Im) ₂ = 246.4 μA, and the electron beam current Ieb ₂ = (321.4-246.4) calculated thereby. ) ΜA = 75 μA can be maintained, and the electron beam current Ieb can always be maintained at a predetermined value of 75 μA. Further, Example 2 will be described in the same manner.
[0030]
In the above-described embodiment of the present invention, when the current (Is + Im) measured by the ammeter 24 changes for some reason, and as a result, the current of the electron beam decreases Ieb, the tube current It or current ( (Is + Im) is increased to control the electron beam current Ieb to be constant, but instead of or in addition to this, has the electron beam current Ieb deviated from a predetermined range? If it is determined whether or not it deviates from a predetermined range, it may be informed that an abnormal state is present by a display means such as a light emitting means or a sounding means.
[0031]
【The invention's effect】
According to the first aspect of the present invention, the electron beam emitting portion is made of a conductive member, and the electron beam emitting portion and the low voltage portion of the DC high-voltage power source are electrically insulated, and the electron beam An ammeter for measuring the current flowing between the emission part and the low-voltage part and an ammeter for measuring the tube current flowing in the electron beam tube are provided so that the difference between the current values measured by the two ammeters is constant. In addition, since the control means for controlling the current flowing in each ammeter is provided, the disadvantage of the conventional device that makes the electron beam output constant by controlling the conventional tube current is solved, and the stable and constant electron A line can be output. Moreover, even if the thickness of the electron beam exit window increases or decreases due to the reaction with the electron beam irradiation atmosphere gas, the electron beam output can be kept constant. Furthermore, compared to a conventional device that captures a part of the electron beam and detects the current, all the electron beams can be used effectively, so that the efficiency of the device can be improved and the current detection unit has an atmospheric gas. Various problems caused by exposure to plasma and contaminants from the object to be processed can be solved.
[0032]
According to the invention described in claim 2, the control means controls the filament power source for generating thermionic electrons from the filament of the electron beam tube and / or the grid power source for controlling the traveling energy of the electrons generated by the grid of the electron beam tube. The current flowing through each ammeter is controlled so that the difference between the current values measured by the two ammeters is constant. Can be controlled.
[0033]
According to the invention described in claim 3 or claim 4, when the difference between the current values measured by the two ammeters exceeds a predetermined range, the display means for notifying that the state is abnormal is provided. The abnormal state of the electron beam output can be notified easily and with high accuracy by simple means.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration for explaining the basic principle of an electron beam irradiation processing apparatus according to the present invention.
FIG. 2 is a diagram showing a configuration of an electron beam irradiation processing apparatus according to the present invention, showing in detail the structure of an electron beam tube holder.
FIG. 3 is a diagram showing a configuration of an electron beam irradiation processing apparatus according to the present invention showing a control system in detail.
FIG. 4 is a table for explaining how the electron beam current Ieb radiated from the electron beam tube is corrected when it changes for some reason.
FIG. 5 is a diagram showing an example of an electron beam irradiation processing apparatus provided with a control means according to the prior art.
FIG. 6 is a diagram showing an example of an electron beam irradiation processing apparatus provided with a control means according to the prior art.
[Explanation of symbols]
1 Electron tube 11 Filament 12 Grid 13 Flange 14 Electron beam exit window 2 Filament power supply 201 Reference oscillator 202 PWM control circuit 203 Drive circuit 3 Filament power transformer 4 Grid power transformer 5 Grid power transformer 6 Ammeter 7 DC high voltage power supply 20 Depressurization chamber 21 Insulators 22, 23 O-ring 24 Ammeter 25 Control unit 251, 252 Current amplifier 253, 254 Current-voltage converter 255 Calculation unit 256 Filter 257 Gain adjuster

Claims (4)

In an electron beam irradiation processing apparatus comprising an electron beam tube having an electron beam emitting part that transmits and transmits an electron beam, and a DC high voltage power source that applies a DC high voltage to the electron beam tube,
The electron beam emitting portion is made of a conductive member, and electrically insulates between the electron beam emitting portion and the low voltage portion of the DC high voltage power source and flows between the electron beam emitting portion and the low voltage portion. An ammeter that measures current and an ammeter that measures the tube current flowing in the electron beam tube are provided, and flows to each ammeter so that the difference between the current values measured by the two ammeters is constant. An electron beam irradiation processing apparatus comprising a control means for controlling current. The control means controls the filament power source for generating thermionic electrons from the filament of the electron beam tube and / or the grid power source for controlling the traveling energy of electrons generated by the grid of the electron beam tube, The electron beam irradiation processing apparatus according to claim 1, wherein the current flowing through each of the ammeters is controlled so that a difference between measured current values is constant. 3. The electronic device according to claim 1, further comprising display means for notifying that the state is abnormal when a difference between current values measured by the two ammeters exceeds a predetermined range. X-ray irradiation processing equipment. In an electron beam irradiation processing apparatus comprising an electron beam tube having an electron beam emitting part that transmits and transmits an electron beam, and a DC high voltage power source that applies a DC high voltage to the electron beam tube,
The electron beam emitting portion is made of a conductive member, and electrically insulates between the electron beam emitting portion and the low voltage portion of the DC high voltage power source and flows between the electron beam emitting portion and the low voltage portion. An ammeter that measures current and an ammeter that measures the tube current flowing in the electron beam tube are provided, and when the difference between the current values measured by both ammeters exceeds a predetermined range, it is in an abnormal state. An electron beam irradiation processing apparatus provided with display means for notifying that.

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