JPH0721951A - Particle beam neutralizer and particle beam irradiation device using this neutralizer - Google Patents

Abstract

PURPOSE:To provide a neutralizer with no secondary charge caused by particle charge for neutralization, low operation voltage. high controllability, and compact control power source. CONSTITUTION:An electron source 5 for keeping cathode potential the same as the potential of a work 9, and a layered grid 2 enclosing an ion beam 1 and applied with positive voltage are installed. Low energy electrons supplied from the electron source 5 are stored in the layered grid 2. The electrons stored in the layered grid 2 are attracted by space charge of the ion beam 1 and trapped to neutralize the ion beam. A neutralizer arranged just before the work 3 acts as Faraday cup and current value of the ion beam 1 is obtained. A particle irradiation device with correct dimension is thus provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle beam neutralizer for neutralizing the space charge of an ion beam, and preventing the work from being charged when the work is irradiated with the ion beam. The present invention relates to a particle beam neutralizing device, particularly to a beam neutralizing tube of a neutral beam injecting device, an electron shower of an ion implanting device, a plasma flood device and the like.

[0002]

2. Description of the Related Art In a neutralizing device for an ion implanter, for example, when the charge of a work is neutralized by electrons,
If the electrons have high energy, a secondary phenomenon occurs in which the work is negatively charged and damaged. For this reason, various methods for reducing the energy of the electrons have been devised.

As a conventional neutralizing device, in order to suppress the electrification of the work piece or sample in a vacuum, a device for supplying electrons to the work piece or sample from an electron source having the same potential as the work piece or sample is used. is there. That is, the electrons are accelerated and extracted,
After that, the speed is reduced to reduce the energy of electrons, and the electron source and the workpiece or sample are set to the same potential to prevent the workpiece or sample from being charged. Related to this is the technique described in JP-A-1-220350.

As another conventional apparatus, there is a method using plasma. The method using plasma is to generate plasma by a plasma bridge for neutralization.
That is, low-energy electrons are accumulated around the positive ions in the center of the plasma to make the potential zero as a whole, and the density thereof is increased.

[0005]

In the above conventional neutralizer, when electrons are reduced in energy by deceleration or the like, the electrons diverge due to their own space charge, or the electrons are Since the electric field around the beam cannot be exceeded,
There is a problem that it is difficult to obtain a sufficient charge density or current value necessary for neutralization. On the other hand, the neutralization device using plasma is considered to be improved in terms of the above-mentioned charge density or current value, but there were other problems.

Next, the above problem will be described in detail. 1. Atmosphere pressure during operation of the neutralizer is high, that is, the degree of vacuum is low. Therefore, an error may occur in the ion beam current measurement. Further, an ion beam mixing phenomenon occurs in which atmospheric gas is injected into the surface of the work, and the contamination of the work due to this phenomenon becomes a problem.

2. Plasma control is difficult. At present, it is difficult to control the optimum and sufficient amount of plasma, that is, the density, for various ion beam conditions. The first reason is that the means for accurately measuring the neutralization state of the work has not been established. This is also the case when using electron showers without using plasma. Therefore, it is difficult to make the standard of the plasma control, that is, the set value.
However, it is said that the plasma is less likely to be negatively charged like the electron shower even when it is excessively irradiated. Therefore, in many cases, excessive power is input, plasma is excessively generated, and control is not performed.

The second reason is that the parameters for controlling the plasma are microwave power, magnetic field strength, etc. when microwaves are used for plasma generation, and arc discharge is used. In this case, arc voltage and current, filament current, and the like. Further, a parameter common to these two methods is a supply gas flow rate. The supply gas flow rate determines the atmospheric gas pressure, and the plasma density is determined by the atmospheric gas pressure.

However, even when the work is irradiated with ion beams, gas is generated and the atmospheric gas pressure changes. That is, as described above, there are many setting parameters and some of them change with time like the gas pressure, and it is difficult to set the plasma density itself.

3. The control power supply is large. Regardless of whether microwave or arc discharge is used to generate plasma, an excessive amount of plasma must be generated, which requires a large power supply capacity. The present invention has been made in order to solve the above-mentioned problems of the prior art, and there is no secondary charging due to particle charge for neutralization, lower operating pressure, better controllability, and control power supply. The first object is to provide a neutralizer having a small size. A second object of the present invention is to provide a particle beam irradiation apparatus in which the current value of the ion beam is accurately controlled by using the above neutralizing apparatus.

[0011]

In order to achieve the above object, the constitution of the first invention relating to the neutralizing apparatus of the present invention is an ion source for irradiating a work in a vacuum chamber with an ion beam. And an electron source having substantially the same electric potential as the work for supplying electrons to the ion beam to prevent space charge of the ion beam or charging of the work caused by irradiation of the ion beam. In the particle beam neutralizing apparatus configured as described above, a means for accumulating electrons from the electron source is provided around the ion beam.

The storage means has a conductive layered grid arranged around the ion beam, a positive high voltage is applied to the grid, and electrons from an electron source are passed through the electric field of the layered grid to generate an ion beam. It is designed to be supplied to the system. The grid closest to the outside of the ion beam is set to have substantially the same potential as the work or vacuum chamber.

Further, the voltage power supply applied to the layered grid is common to the electron extraction power supply of the electron source cathode section. Further, the layer grid, the electron source and the work constitute a Faraday cup for measuring the ion beam current. Further, it is provided with a mechanism for supplying a gas to the layered grid, and the gas is a rare gas such as high-purity argon, xenon or krypton. Further, a control mechanism is provided in the gas supply mechanism so that the gas pressure of the ion beam becomes constant.

In order to achieve the above-mentioned second object, the second invention relating to the particle beam irradiation apparatus of the present invention is the particle beam according to the first invention immediately before the irradiated work. A neutralizer is provided.

[0015]

The function of each of the above technical means is as follows.
According to the structure of the first aspect of the invention, the cathode potential of the electron source is set to substantially the same potential as that of the work and the electrons are drawn out, so that low-energy large-current electrons can be obtained. Since a layered grid is arranged in the electron emitting portion of the electron source and a positive voltage is applied to the layered grid, the layered grid absorbs the large current electrons. The absorbed electrons diffuse in the grid,
A large amount is accumulated until the positive potential of the grid is offset.

When the layered grid is arranged so as to surround the ion beam, and the series of grids closest to the ion beam side have the same potential as the work or vacuum chamber, the positive space charge of the ion beam becomes The electrons accumulated in the grid are trapped. As a result, the positive space charge of the ion beam is neutralized. When such a ion beam is applied to a work having an insulator surface, the work surface is positively charged and the potential rises.

When the work surface rises positively as described above,
The electrons in the ion beam are absorbed by the work,
The potential of the ion beam increases due to the positive space charge of the ion beam. Again, the electrons accumulated in the layered grid are supplied to the ion beam. Since the layered grid surrounds the entire ion beam, electrons are uniformly supplied to the ion beam to neutralize the ion beam. In this case, since the electrons are not supplied from one direction of the ion beam, the electron density does not locally increase, and the increase in the impedance at the time of supplying the electrons can be minimized.

Further, by setting the layered grid of the layer closest to the ion source side to have substantially the same potential as the work, a potential barrier is created with respect to the outer layer grid, and the electrons once trapped in the ion beam are regenerated. It is prevented from moving to the layered grid side. In the case where gas is generated from the work surface by ion beam irradiation, when the generated gas reaches the layered grid, the electrons accumulated in the grid collide with gas molecules and become plasma, and this plasma is generated. It acts to neutralize the ion beam.

When the ion beam is irradiated for a long period of time, the gas emission may be reduced and the neutralizing ability of the neutralizing device may be changed. In such a case, by supplying gas to the grid portion from the outside and keeping the gas pressure constant, the neutralizing ability can be made constant during the beam irradiation time.

Further, even if there is no gas emission from the work due to the ion beam, plasma can be efficiently generated and contribute to neutralization by releasing the gas from the outside to the grid. In this case, since it is not necessary to cause arc discharge, it is not necessary to raise the gas pressure as in the case of arc discharge, and it is possible to operate at a low pressure.

According to the second aspect of the invention, since the particle beam neutralizer is arranged immediately before the work, the electron source, the layered grid and the work of the particle beam neutralizer are arranged. A Faraday cup is constructed by combining and the ion beam current incident on the work can be accurately measured. Therefore, the work is irradiated with an ion beam having an accurate current value. be able to.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Each embodiment of the present invention will be described below with reference to FIGS. [Embodiment 1] FIG. 1 is a schematic perspective view of a particle beam neutralizer main body according to an embodiment of the present invention, and FIG. 2 is an AA of the particle beam neutralizer main body of FIG. ′ A cross-sectional view and FIG. 3 are overall configuration diagrams of a particle beam neutralizing device including the particle beam neutralizing device main body of FIG. 1.

The particle beam neutralizing apparatus according to the first embodiment of the present invention is shown in FIGS. 1, 2 and 3 in which 1 is an ion beam,
2 is a layered grid for focusing the ion beam 1; 3 is a work for irradiating the ion beam 1; 4 is a Faraday cage;
5 is an electron source, 6 is a filament of the electron source 5, 7 is an electron extraction electrode from the filament 6, 8 is a shield plate of the filament 6, 9 is an electron from the filament 6 and 10 is a gas in the Faraday cage 4. Gas pipe to be introduced, 11 is a gas flow rate control device, 12 is a gas cylinder, 13 is an aperture, 14 is a suppressor electrode, 15 is a bias power supply for the work 3, 16 and 17 are ammeters, 18 is a filament 6 Heating power source, 19 is a bias power source for the electron extraction electrode 7, P
a, Pb, Qa, Qb are conductor plates.

A Faraday cage 4 is disposed in a chamber (not shown) held in a vacuum, and the Faraday cage 4 has a hollow casing forming a rectangular body. There is. Conductor plates Pa and Pb are provided on the inner sides of both sides (both left and right sides in the figure) of the Faraday cage 4 close to each other, and layered between the conductor plates Pa and Pb. The wire grid 2 is stretched.

Conductor plates Qa and Qb are arranged close to each other inside the conductor plates Pa and Pb. The conductor plate Qa,
A large number of small holes are provided in Qb, the layered wire grid 2 is passed through the small holes, and the conductor plates Qa, Qb and the layered wire grid 2 are electrically insulated. The Faraday cage 4 and the conductor plate Q are arranged so that the Faraday cage 4 and the conductor plates Pa and Pb are electrically insulated.
Each of a and Qb is configured to be electrically connected.

Through holes Ha and Hb for the ion beam 1 are provided on both the left and right sides of the Faraday cage 4, and the conductor plates Pa and Pb corresponding to the Ha and Hb and the conductor plate Qa, respectively. A through hole is also formed in each of the Qb portions. One through hole (left side in the drawing) Ha is an inlet side of the ion beam 1, and another through hole (right side in the drawing) Hb is an outlet side. An earth aperture 13 and a suppressor electrode 14 are provided outside the inlet through hole Ha, and a work 3 is provided near the outside of the outlet through hole Ha.

On the upper and lower surfaces of the Faraday cage 4,
One electron source 5 is provided for each. Each of the electron sources 5 includes a filament 6 and an electron extraction electrode 7
Composed of and. The filament 6 is connected to a filament power source 18 to be heated and is also connected to the casing of the Faraday cage 4. And work 3
And the potential is almost the same.

The electron extraction electrode 7 is connected to an electron extraction power source 19 and is biased by 50 to 1 KV higher. The electronic drawing power source 19 is controlled by the CPU. A shield plate 8 is provided on the filament 6 so as to shield it from the work 3 and the ion beam 1.

The shield plate 8 is disposed between the conductor plates Qa and Qb, and is inclined to the left and right so as to be convex with respect to the filament 6. The Faraday cage
A gas pipe 10 for introducing gas into the Faraday cage 4 is provided on the upper surface of the casing of the gas pipe 4, and the gas pipe 10 is a CPU.
Gas flow controller 11 and gas cylinder 1 controlled by
2 is connected to the pipe.

In the work 3, a bias power supply 15 and ammeters 16 and 17 for measuring the amount of electric charges incident on the work are connected in series. The housing of the Faraday cage 4 and the electronic drawing power source 19 are connected to a common terminal of the ammeter 16 and the ammeter 17. The terminal of the ammeter 17 opposite to the common terminal is grounded. The ammeter 16 indicates the ion beam current after neutralization, and the ammeter 17
Shows the current value of the ion beam 1. The ammeters 16 and 17 output the current value to the CPU.

The operation of this embodiment will be described. The ion beam 1 passes through the ground potential aperture 13 and the suppressor electrode 14, enters the Faraday gauge 4 through the through holes Ha, passes through the through holes of the conductor plates Pa and Qa, and passes through the layered grid 2
Then, the work 3 is irradiated with the light passing through the portion surrounded by the arrow, the through holes of the conductor plates Qb and Pb, and the through hole Hb.

The filament 6 is heated by the heating filament power source 18 to emit electrons 9. An electron extraction electrode 7 is placed on the filament 6 and is biased so that a large amount of electrons are extracted. Since the shield plate 8 is attached to the conductor plates Qa and Qb, the shield plate 8 has the same potential as the case of the Faraday cage 4. Further, since the filament 6 is also connected to the casing of the Faraday cage 4, it has substantially the same potential as the shielding plate 8. Therefore, the electrons 9 are decelerated by the shield plate 8 and do not enter the shield plate 8.

As described above, the shielding plate 8 is formed so as to be convex with respect to the filament 6 and inclined leftward and rightward, so that the electrons 9 are deflected leftward and rightward. As a result, the movement of the electron 9 acts in a trajectory as shown in FIG. Then, the electrons 9 are transmitted to the layered grid 2
Of the Faraday Gauge 4 so as to be wrapped around each wire grid. When the electrons 9 diffuse into the whole Faraday-4 and approach the central ion beam 1, they are trapped by the positive space charges of the ion beam 1 and neutralize the ion beam 1.

Now, the ion beam entering the work 3
The column 1 and the electron flow are superposed and measured by the ammeter 16. The amount of electrons emitted from the electron source 5 is controlled by the CPU so that the current value becomes approximately 0 to a slightly negative current value. At this time, when the work 3 applies a positive voltage of about 1 to 10 V from the bias power supply 15, the control of the electron amount becomes easy.

The electrons 9 emitted from the electron source 5 are applied to the extraction electrode 7 of the electrons 9 and the electron extraction power source 19 is applied.
The bias voltage due to is controlled by the CPU. It is desirable that this bias voltage be 50 to 1 kV. The filament power source 18 may be controlled. The electronic 9 is controlled by the
There is no problem even if another method such as a di-sensor is used. In this way, the amount of the electrons 9 can be set to the optimum value, so that the power supply capacity will not be increased more than necessary. The energy of the electrons can be set freely because it is determined by the potential difference between the work 3 and the filament 6.

The ion beam 1 is formed on the surface of the work 3.
Is irradiated, gas is released and the degree of vacuum is lowered.
When this gas reaches the layered grid 2, the gas collides with the electrons diffused in the layered grid 2 and is ionized, and simultaneously emits electrons. The ions and electrons generated here diffuse in the plasma state and reach the ion beam 1 and the work 3 to neutralize their respective charges.
The released gas decreases with time. Therefore, the neutralizing effect changes with the gas pressure.

In order to suppress this change, gas is supplied into the Faraday gauge 4 from the pipe 10 to which the gas flow rate control device 11 and the cylinder 12 are connected. The gas supply system is controlled by the CPU so that the pressure immediately before the work 3 is constant, not for supplying the gas pressure more than necessary. The gas supplied at this time is preferably a rare gas such as argon, xenon or krypton. As described above, according to this embodiment, electrons of high density and low energy are supplied, the ion beam is neutralized, and the work is neither charged nor damaged.

[Embodiment 2] The particle beam irradiation apparatus of the present embodiment according to the first invention will be described with reference to FIGS. 1 and 3 used for the description of [Embodiment 1]. 1 and 3 show [Example 1].
Since it has been described above, it will be omitted. As shown in FIG. 1, the particle beam neutralizing device and the work 3 are arranged close to each other. If the secondary electron of the work 3 is prevented from diffusing by the particle beam, the electron source 5, the layered grid 2 and the work 3 form a Faraday cup, and the ammeter 16 is used to form an ion beam. The current can be measured accurately. Thus, when it is necessary to accurately irradiate the particle beam, the particle beam can be used in, for example, an ion implantation device.

[0039]

As described in detail above, according to the present invention, firstly, there is no secondary electrification due to the particle charge for neutralization, the operating pressure is lower, the controllability is good, and It is possible to provide a neutralizer having a small control power supply.
Secondly, it is possible to provide a particle beam irradiation device in which the current value of the ion beam is accurately controlled by using the neutralizing device.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a particle beam neutralizing apparatus main body according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA ′ of the particle beam neutralizing device body of FIG.

FIG. 3 is a particle beam including the particle beam neutralizing apparatus main body of FIG.
It is a whole neutralization apparatus block diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion beam 2 Layered grid 3 Work 4 Faraday cage 5 Electron source 6 Filament 7 Electron extraction electrode 8 Shielding plate 9 Electron 10 Gas introduction pipe 11 Gas flow control device 12 Gas cylinder 13 Earth aperture 14 Suppressor Electrode 15 Bias electrode 16,17 Ammeter 18 Filament power supply 19 Electron extraction power supply Pa, Pb, Qa, Qb Conductor plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 21/027

Claims (9)

[Claims] 1. An ion beam is provided in a work in the vacuum chamber.
An ion source for irradiating the ion beam, and an electron source having substantially the same potential as the work for supplying electrons to the ion beam, and to the space charge of the ion beam or the work of the ion beam. In the particle beam neutralizing device configured to prevent the work from being charged by the irradiation of the ion beam, a means for accumulating electrons from the electron source is provided around the ion beam. A particle beam neutralizing device. 2. The particle beam according to claim 1, wherein the accumulating means has a conductive layered grid arranged around the ion beam, and a positive high voltage is applied to the grid. Neutralizer. 3. The particle beam neutralizing apparatus according to claim 2, wherein the grid closest to the outer side of the ion beam has substantially the same potential as that of the work or vacuum chamber. 4. The particle beam neutralizing device according to claim 2, wherein the voltage power source applied to the layered grid is common to the electron extracting power source of the electron source cathode section. 5. A Faraday cup for measuring an ion beam current is constituted by a layered grid, an electron source and a work.
Any of the particle beam neutralization devices described. 6. A gas supply mechanism for supplying a gas to the layered grid is provided.
Any of the particle beam neutralization devices described. 7. The particle beam neutralizing apparatus according to claim 6, wherein the gas supply mechanism includes a control unit for controlling the gas supply so that the gas pressure of the ion beam becomes constant. . 8. The particle beam neutralization device according to claim 6, wherein the gas is a rare gas such as high-purity argon, xenon, or krypton. 9. The method according to any one of claims 1 to 8 immediately before the work.
A particle beam irradiating device comprising the particle beam neutralizing device according to any one of the above.