JP2001221898A - Method for measuring dose of electron beam and device for electron beam irradiation treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely measure the dose of an electron beam outputted from an electron beam(EB) tube and to adjust the dose of the electron beam radiated onto an object to a constant value under control. SOLUTION: A device for measuring the dose of an electron beam, that consists of a current detecting component 11a and a current measuring component 11b, is placed near the outside of a window 1b of the EB tube 1. The surface of the current detecting component 11a, which is composed of a conductor or a semiconductor, is coated with an insulant coating of a prescribed thickness. Some electrons in the electron beam emitted from the window 1d of the EB tube 1 are caught by the current detecting component 11a to generate a current in it. The generated current is sent from the current measuring component 11b to a controlling component 12, for example, which adjusts the dose of the electron beam emitted from the EB tube 1 to a constant value under control by controlling a filament power source 3. Since a conductor or a semiconductor coated with an insulating film is used as the current detecting component 11a, the dose of the electron beam outputted from the EB tube 1 can be measured precisely, without being affected by a suspended electric charge near the current detecting component 11a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures an electron dose emitted from a vacuum tube type electron beam tube used for curing a resist applied to a semiconductor wafer or the like or drying ink applied to various printed materials. Electron dosimetry method, and
The present invention relates to an electron beam irradiation processing apparatus that performs processing by irradiating the object with an electron beam.

[0002]

2. Description of the Related Art It has been proposed to use electron beam irradiation for curing a resist applied to a semiconductor wafer or the like and for drying or curing a paint, ink, adhesive or protective resin applied to a substrate or the like. Is coming. In recent years, Tokuhyo Hei 10-5120
Electron tubes with windows, such as those described at 92, have become commercially available. The configuration of this electron beam tube is as follows: a thermoelectron emission section and an electron beam acceleration section are provided in a vacuum vessel having a window through which electron beams pass, and the thermoelectrons emitted from the thermoelectron emission section are accelerated by the electron beam acceleration section And release from the window. When such an electron beam tube is used, an electron beam can be emitted from the window into the atmosphere. Conventionally, an electron beam irradiation processing apparatus decompresses the atmosphere in which an object is placed. However, if the electron beam tube is used, there is no need to use a vacuum pump or a vacuum chamber for decompression. The structure of the line irradiation processing device is simple and handling is easy.

FIG. 7 shows a schematic structure of a straight tube type electron beam tube (hereinafter referred to as an EB tube) having a window and a power supply circuit thereof. E
The B tube 1 has a filament 1a and a grid 1b inside. The filament 1a and the grid 1b are connected to the DC high voltage power supply 2 through the terminal
A high voltage of V is applied. A filament power supply 3 is connected to the filament 1a via a terminal 1f. The filament 1a is heated by a current supplied from the power supply 3 and emits thermoelectrons. The emitted electrons are on grid 1
The beam shape is adjusted by the electric field generated by b. A grid power supply 4 is connected to the grid 1b via a terminal 1f. By controlling a voltage applied to the grid 1b, electron emission from the EB tube 1 can be controlled. The shaped electron beam (hereinafter, referred to as an electron beam) passes through a window 1 d provided in the flange 1 c through the EB tube 1.
Is emitted outside. The electron beam emitted from the EB tube 1 is
For example, an object to be processed such as a semiconductor wafer or various printed materials (not shown) is irradiated to cure the resist and dry the ink.

The EB tube 1 has a quartz tube wall 1e and a flange 1
c and the window 1d form a closed structure. Inside
The pressure is set to 10 so that the generated electron beam does not decay.^-Four~
10 ^-6Pa (10^-6-10^-8Torr)
You. The window 1d is such that it does not decay when passing through the electron beam,
Special silicon-containing material with a thickness of several μm (for example, 3 μm)
It is a film made of a material. The larger the area of window 1d,
The generated electron beam can be efficiently emitted to the outside of the EB tube 1.
it can. However, as described above, a very thin thickness (several μ
m), the atmospheric pressure outside the EB tube 1 and the pressure inside the EB tube 1
(10^-Four-10^-6Pa). did
There is a risk of breakage, so you can increase the area of one
Absent. Therefore, as shown in FIG.
window with a small area of m so that it follows the shape of the electron beam
And a plurality of filaments are arranged in the longitudinal direction of the filament.

[0005] Using the electron beam emitted from the EB tube 1,
When processing a workpiece (work), it is necessary to irradiate the workpiece with a set predetermined electron dose. If a predetermined amount of electron beam cannot be irradiated on the object to be processed, a shortage or excessive amount of irradiation may cause a processing failure. The following two methods are considered as a method of emitting a constant electron dose. E
This is control for keeping the power supplied to the B tube 1 constant. A method of detecting a tube current and controlling the current to be constant. As shown in FIG. 7, a tube current (in FIG. 7, a current flowing from the DC high-voltage power supply 2 to the EB tube 1, a dotted arrow in the drawing) is detected by the current detection unit 5, and a current flowing in the filament 1 a is controlled. This is a method of controlling the tube current to be constant. If the voltage of the DC high-voltage power supply 2 is constant, the tube current is controlled to be constant so that the power supplied to the EB tube 1 is controlled to be constant. This method uses X
It is usually done in a wire tube.

[0006] A method of keeping the input power of the filament constant. The current flowing through the filament 1a (and the filament 1
This is a method of controlling the input power of the filament 1a to be constant by controlling the voltage of the filament 1a). By controlling the power of the filament 1a to be constant, the amount of thermionic emission, that is, the tube current is controlled to be constant, and the power supplied to the EB tube 1 is controlled to be constant.

[0007]

As shown in FIG. 7, even when the tube current is controlled to be constant and constant power is supplied to the EB tube 1, the amount of electron beam output from the EB tube 1 is reduced. May change. This is considered to be due to the following reasons. Filament 1a and grid 1b inside EB tube 1
Is fixed internally so that the position does not change. However, when the electron beam is emitted, the heated filament is about 19
Since the temperature reaches 00 ° C., the shape of the filament and the grid near the filament change due to thermal expansion. Therefore, the shape and direction of the electron beam change. The inside of the tube wall is charged, and the shape and direction of the electron beam change due to the influence of the charged static electricity.

As described above, the window 1d for taking out the electron beam to the outside of the EB tube 1 has a width of about 1 mm and is arranged in the longitudinal direction of the filament. For this reason, if the shape or direction of the generated electron beam changes inside the EB tube 1 due to the reasons described above, the electron beam is also irradiated to portions other than the window 1d, and such an electron beam is externally irradiated. , The resulting emitted electron dose changes. Therefore, even if the EB tube 1 is controlled to supply a constant power, the amount of the electron beam output from the EB tube 1 cannot be made constant.

As described above, even if the EB tube 1 is controlled so as to supply a constant power, the electron dose output from the EB tube 1 cannot always be controlled to be constant. In the case of processing the work using the electron beam emitted from No. 1, it was not possible to irradiate the work with the predetermined electron dose set. The electron dose can be controlled to be constant by measuring the electron dose output from the EB tube 1 and controlling the power supplied to the EB tube 1 so that the measured electron dose becomes constant. However, there has been no known method for accurately measuring the electron dose output from the EB tube 1. In particular, by irradiating the electron beam, the atmospheric gas becomes plasma, and secondary electrons are emitted from the object to be processed, a work stage on which the object to be processed is mounted, walls of a processing chamber, and the like. For this reason, even if a sensor or the like for detecting the electron dose is disposed near the window 1d of the EB tube 1, the electron dose output from the EB tube 1 can be accurately and stably affected by the floating charge due to the secondary electrons. Sometimes it cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and a first object of the present invention is to accurately measure an electron dose output from an electron beam tube and applied to a processing object. It is to provide an electron dosimetry method which can be performed. A second object of the present invention is to provide an electron beam irradiation processing apparatus capable of controlling the amount of electron beams output from an electron beam tube to be constant and controlling the dose of electrons irradiated to an object to be processed to be constant. It is to be.

[0011]

According to the present invention, the above-mentioned problems are solved as follows. (1) A current detection unit in which a conductor or a semiconductor is covered with an insulating film is disposed outside the window of the electron beam tube, and the current flowing through the current detection unit is measured to irradiate an electron beam from the electron beam tube. Is measured. (2) The method of measuring an electron dose is applied to an electron beam irradiation processing apparatus, and a current detection unit composed of a conductor or a semiconductor covered with an insulating film is provided outside a window of an electron beam tube. An electron dosimeter consisting of a current measuring unit that measures the flowing current is arranged, and the power unit is controlled in accordance with the current signal flowing through the current detecting unit to control the electron dose irradiated to the irradiation target to be constant. I do.

In the present invention, as described above, a current detector is provided in which a conductor or a semiconductor is covered with an insulating film, and a current flowing through the current detector is measured to radiate the current from the electron beam tube. Since the electron dose is measured, the insulating film serves as an energy barrier, so that it is possible to prevent the generation of current due to the incorporation of stray charges into the conductor or semiconductor. Therefore, it is possible to detect a current caused only by electrons emitted from the electron beam tube, and to accurately measure an electron beam output from the electron beam tube. Also,
The above electron dose measurement method is applied to an electron beam irradiation processing device to control the electron dose output from the electron tube, so that the electron dose output from the electron tube is controlled without being affected by stray charges. In addition, a constant amount of electron beam can be output stably even if the shape or direction of the electron beam changes inside the electron tube. For this reason, it is possible to irradiate the irradiation target with the set predetermined electron dose, and it is possible to prevent the occurrence of processing failure due to an insufficient or excessive irradiation amount.

[0013]

FIG. 1 is a diagram showing an embodiment of the present invention. 7, the EB tube 1 includes a filament 1a and a grid 1b inside. Filament 1a
And the grid 1b, for example, 30
A high voltage of ~ 70 kV is applied. A filament power supply 3 is connected to the filament 1a via a terminal 1f. The filament 1a is heated by a current supplied from the power supply 3 and emits thermoelectrons. The emitted electrons are shaped into a beam by the electric field generated by the grid 1b. Further, a grid power supply 4 is connected to the grid 1b via a terminal 1f, and thermionic emission can be controlled by controlling the voltage applied to the grid 1b. The shaped electron beam is emitted out of the EB tube 1 from a window 1d provided in the flange 1c.

An electron dosimeter 11 having a current detector 11a is provided near the outside of the window 1d of the EB tube 1 (for example, at a distance of 5 mm from the window). The current detector 11a is made of a conductor such as stainless steel, copper, aluminum or a semiconductor such as silicon, germanium, or a compound semiconductor. The current measuring unit 11b includes an ammeter for measuring the detected current and a current-voltage conversion circuit. Some of the electrons emitted from the window 1d of the EB tube 1 are caught by the current detector 11a. The caught electrons move through the current detector 11a, which is a conductor or a semiconductor, to generate a current. The generated current is measured by the current measuring unit 11b, converted into a voltage signal indicating the measured current value, and sent to the control unit 12.

The control unit 12 compares the measured current value with a preset current value input in advance. If the measured current value is smaller than the set current value, the filament power supply 3 is controlled to increase the tube current and the power supplied to the EB tube 1. If the measured current value is larger than the set current value, the tube current is reduced and the power supplied to the EB tube 1 is reduced. As described above, the electron beam emitted from the window 1d of the EB tube 1 is detected as a current value, and the electron beam is detected based on the current value.
By controlling the power value supplied to the B tube 1, the amount of the electron beam output from the EB tube 1 can be controlled constantly and stably. FIG. 1 shows a case in which the filament power supply 3 is controlled by the output of the electron dosimeter 11, but the voltage applied to the grid 1b is P
The electron dose output from the EB tube 1 may be controlled by WM control.

FIG. 2 is a diagram showing an example of the arrangement of the current detection unit. As shown in the figure, the current detecting unit 11a is constituted by a plurality of conductors or wires made of semiconductors, and each of the windows 1 of the EB tube 1
It is preferable that each line is arranged near d in a direction substantially orthogonal to the longitudinal direction (the direction in which the windows 1d are arranged). With this arrangement, even if the position of the current detector 11a is slightly shifted, the effect can be reduced, and the irradiation of the electron beam is not hindered. When the electrons are taken into the current detecting unit 11a shown in FIG. 2, the electrons flow through the conductor or semiconductor of the current detecting unit 11a, and the magnitude of the current is a value proportional to the amount of the electrons taken into the current detecting unit 11a. Becomes Since the current is generated by taking in electrons, the direction of the current is as shown in FIG.

Here, it is necessary to consider the following in order to stabilize the current value detected by the current detector 11a. The current detector 11a needs to catch only the electron beam output from the window 1d of the EB tube 1. However, in the vicinity of the current detection unit 11a, charges are generated and floated by electron beam irradiation, and the current detection unit 11a also takes in the charges. It is considered that the above-mentioned charge is caused by the following reasons. The atmosphere gas is turned into plasma by electron beam irradiation. By electron beam irradiation, secondary electrons are emitted from the electron dosimeter 11, a work stage for mounting an object to be processed (not shown), a wall of a processing chamber where the work stage is arranged, and the like.

These floating charges in the vicinity of the current detector 11a are taken into the current detector 11a to generate a current when the object to be processed is not near. Further, when the object approaches, the object is attracted to the object and cannot be taken into the current detection unit 11a. That is, the current value measured by the current measuring unit 11b greatly changes depending on the presence or absence of the object to be processed. From the above, if the electron dose is not measured so as not to be affected by the floating charge, the EB tube 1
The electron dose output from the EB tube 1 cannot be accurately measured, and the electron dose output from the EB tube 1 cannot be stably controlled.

Normally, the energy of the electron beam output from the EB tube 1 is several tens keV, and the energy of the floating charge is several tens eV. However, regardless of the magnitude of the energy, the current generated in the current detection unit 11a when electrons are caught is the same.
The current flowing to the current detection unit 11a increases. Therefore,
In the present invention, by utilizing the difference between the energy of the electron beam output from the EB tube 1 and the magnitude of the energy of the stray charge, only the electrons having a large energy output from the EB tube are supplied to the electron dosimeter 11. Is caught by the current detector 11a. Specifically, the current detection unit 11
a) Conductor or semiconductor surface is coated with an insulator.
The type and thickness of the insulator to be coated are selected so that a charge of several tens eV does not pass, but an electron of several tens keV serves as a barrier for passing energy. As the insulator, for example, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), or the like can be used.

A stainless steel wire is used as the current detecting portion 11a of the electron dosimeter 11, and the current value is determined depending on whether the stainless steel wire is coated with a ceramic film (Al ₂ O ₃ , 15 μm thick) or not. Was measured. FIG. 3 shows an experimental circuit. As shown in FIG.
An electron dosimeter 1 at a position 5 mm away from the window 1 d of the tube 1
1 of the current detector 11a, and the window 1 of the EB tube 1.
A work W (using a wafer) is placed below d, and E
By changing the distance between the B tube 1 and the work W, the current detection unit 11a
Was measured by the current measuring unit 11b. The work W is placed on the work stage WS. The work stage WS is made of a conductor and is grounded. The power supplied to the EB tube 1 is 50 kV · 200
μA, and the atmosphere is normal pressure and air.

FIG. 4 shows the results. The horizontal axis is the distance (mm) from the window of the EB tube to the surface of the wafer as the work W,
The vertical axis represents the current value (μ) detected by the current detection unit 11a.
A), a circle in the figure indicates a case where an uncoated stainless wire is used as the current detection unit 11a, and a square indicates the stainless wire covered with the 15 μm-thick ceramic film as the current detection unit. It shows the case of using. When the current detector 11a is a stainless wire without coating, the closer the wafer (work W) is to the EB tube 1, the smaller the detected current value. This is because, as described above, as the wafer approaches, charges floating near the electron dosimeter are caught by the wafer.

On the other hand, when the current detector 11a is coated with a ceramic having a thickness of 15 μm, the detected current value hardly changes even when the wafer approaches. An Al ₂ O ₃ ceramic coating with a thickness of 15 μm corresponds to an energy barrier of about 30 keV. Therefore, the floating electric charge of several tens eV cannot pass through the ceramic coating film and is not caught by the stainless wire. Therefore, the current detection unit 11a
Is 30 keV emitted from the EB tube 1 without being affected by the electric charge floating near the current detecting unit 11a.
A current due to only electrons having the above energy can be detected. From the above experiment, it was found that the electron dose can be measured accurately without being affected by the stray charge if the conductor or semiconductor of the current detection unit 11a is coated with a ceramic having a thickness of 15 μm. It is considered that the thickness of the ceramic film may be smaller than 15 μm. That is, as described above, the floating charge is several tens eV, and the ceramic film may be coated to such a thickness that the floating charge of several tens eV cannot pass.

As described above, by providing the electron dosimeter 11 and measuring the electron dose and controlling the power of the EB tube 1, the electron dose is controlled without being affected by the floating charge as described above. In addition to this, as described above, it is also possible to prevent the output of the EB tube 1 from fluctuating due to the effect of thermal expansion due to heating of the filament and the effect of charging inside the tube wall. The electron dose output from the EB tube 1 can be kept constant. FIG. 5 shows a case where the electron dose is measured by the electron dosimeter 11 to control the power of the EB tube 1 as shown in FIG. 1 and a case where the tube current is detected and the power of the EB tube 1 is detected as shown in FIG. E when controlling
It is a figure showing the output of B tube 1.

FIG. 2 shows the result of measuring the current flowing through the work when the conductor is used as the work and the work is irradiated with an electron beam from the EB tube. Time (minutes), horizontal axis is EB at the start of EB tube lighting
The percentage when the output of the tube is 1 is shown. The circles indicate the case of constant tube current control, and the triangles indicate the case where the electron dosimeter 11 is provided to control the power of the EB tube 1. As shown in the figure, when the tube current is controlled to be constant (circle in the figure), the output from the EB tube decreases after the EB tube is turned on, and reaches 100% after approximately 14 minutes. This is because, as described above, the shape of the filament and the grid in the vicinity thereof change due to thermal expansion due to the heating of the filament after the EB tube is turned on, and the shape and direction of the electron beam change, and the influence of the charging. It is thought to be due to. On the other hand, when the electron dosimeter 11 was provided to control the power of the EB tube (triangular mark in the figure), the output of the EB tube was kept substantially constant as shown in the figure. As described above, by providing the electron dosimeter 11 and controlling the power of the EB tube,
Immediately after the lighting of the B tube, the electron dose output from the EB tube becomes constant, so that the electron beam irradiation processing can be performed without waiting time, and the throughput can be improved.

By the way, the diameter of the EB pipe is about several centimeters, and when processing a large work, it is necessary to arrange a plurality of EB pipes in a plane to process the work. FIG. 6 is a diagram showing a configuration example of a control system when a plurality of EB tubes are used as described above. A voltage is supplied from the DC high-voltage power supply 2 and the grid power supply 4 to each of the EB tubes 1-1 to 1-n, and each of the EB tubes 1 is provided with a filament power supply 3-1 to 3-n. And, as shown in FIG.
The above-mentioned electron dosimeter 11 is provided in each of a plurality of EB tubes, and the output is sent to each of the control units 12-1 to 12-n. Each of the control units 12-1 to 12-n is provided with the electronic dosimeter 11
Is compared with the preset current value input in advance, and if the measured current value is smaller than the preset current value, the filament power supplies 3-1 to 3-n are controlled to Increase the current. If the measured current value is larger than the set current value, the filament current is reduced. Thereby, the electron dose output from each EB tube 1 can be controlled to be constant.

In the embodiment described above, the filament power supply 3 is controlled based on the output of the electron dosimeter 11 to
The case where the electron dose output from the EB tube 1 is controlled has been described. However, the voltage applied to the grid 1b of the EB tube 1 is controlled so that the electron dose output from the EB tube 1 can be controlled by PWM.
You may make it control. That is, since the EB tube 1 can control the output of the electron beam on / off by controlling the voltage applied to the grid 1b, the EB tube 1 sends the current value measured by the electron dosimeter 11 to the PWM controller. , A PWM controller outputs a pulse width modulation signal (PWM signal) such that the measured current value matches the set current value,
The output controls the voltage applied to the grid 1b of the EB tube 1. As a result, the electron dose output from the EB tube 1 is subjected to PWM control, and the electron dose output from the EB tube 1 can be controlled to be constant as an average value, similarly to the above embodiment.

[0027]

As described above, the following effects can be obtained in the present invention. (1) A current detection unit in which a conductor or a semiconductor is covered with an insulating film is arranged outside the window of the electron beam tube, and a current flowing through the current detection unit is measured. Since the dose is measured, the insulating film serves as an energy barrier, and it is possible to prevent the generation of electric current due to the incorporation of stray charges into the conductor. Therefore, it is possible to stably detect a current caused only by electrons emitted from the electron beam tube, and accurately measure an electron beam output from the electron beam tube.

(2) An electron dosimeter comprising a current detecting section composed of a conductor or semiconductor covered with an insulating film outside the window of the electron beam tube, and a current measuring section for measuring a current flowing through the detecting section. The electron beam output from the electron beam tube is controlled according to the current signal flowing through the current detection unit, so that the electron beam is output from the electron beam tube without being affected by stray charges. The electron dose can be controlled. In addition, since the electron beam output from the electron beam tube is detected and controlled, it is possible to stably output a constant amount of electron beam inside the electron tube even if the shape or direction of the electron beam changes. it can. Therefore, it is possible to irradiate the irradiation target with the set predetermined electron dose,
It is possible to prevent the occurrence of processing failure due to shortage or excessive irradiation amount.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an electron beam tube control device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an arrangement example of a current detection unit.

FIG. 3 is a diagram showing a configuration of an experimental circuit.

FIG. 4 is a diagram showing currents measured when a stainless steel wire is coated with a ceramic film and when it is not coated.

FIG. 5 is a diagram showing outputs when an electron dose is measured by an electron dosimeter and power of the EB tube is controlled, and output when a tube current is detected and power of the EB tube is controlled.

FIG. 6 is a diagram illustrating a configuration example of a control system when a plurality of EB tubes are used.

FIG. 7 is a view showing a schematic structure of an EB tube having a window and a power supply circuit thereof.

FIG. 8 is a diagram illustrating an arrangement of windows of an EB tube.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 EB tube (electron beam tube) 1a filament 1b grid 1c flange 1d window 1e tube wall 2 DC high voltage power supply 3 filament power supply 4 grid power supply 11 electron dosimeter 11a current detection unit 12 control unit

Claims (2)

[Claims] 1. A measuring method for measuring the dose of electrons emitted from an electron beam tube having a window, comprising: a current detecting section in which a conductor or a semiconductor is covered with an insulating film outside the window of the electron beam tube. And measuring a current flowing through the detection unit to measure an electron dose emitted from the electron beam tube. 2. An electron beam tube having a window, and a power supply unit for supplying power to the electron beam tube, and irradiating an electron beam emitted from the electron beam tube to an object to be processed. An electron beam irradiation processing apparatus for processing an object, comprising: a current detection unit formed of a conductor or a semiconductor covered with an insulating film outside a window of the electron beam tube; and measuring a current flowing through the detection unit. An electron dosimeter comprising a current measuring unit is disposed, and the power supply unit is controlled according to a current signal flowing through the current detecting unit to control an electron dose output from the electron beam tube. Electron beam irradiation processing equipment.