JP2001307650A - Method of operating ion source and irradiation device of ion beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means for reducing the time to stabilize ion beam quantity in starting operation of the ion source, without providing extra heater or the like. SOLUTION: In extracting an ion beam 16 after starting operation of an ion source, before the extraction of a given quantity of the ion beam 16, a preliminary heating of a vessel for the plasma generation is made. By generating plasma 12 by applying electric power for plasma generation larger than the power for the plasma generation applied to extract the given quantity of the ion beam 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation method of an ion source used for an ion beam irradiation apparatus such as an ion implantation apparatus and an ion beam irradiation apparatus for performing the same, and more specifically, to an ion source. The present invention relates to means for shortening the time until the ion beam amount is stabilized when the operation is started and the ion beam is extracted.

[0002]

2. Description of the Related Art FIG. 1 shows an example around an ion source of an ion beam irradiation apparatus. This ion source 1 is a so-called burner-type ion source among hot cathode PIG-type ion sources, and a similar one is also described in JP-A-9-35648.

[0003] The ion source 1 comprises a plasma generation vessel 2 also serving as an anode, a filament 8 provided on one side of the plasma generation vessel 2, and a reflective electrode 10 provided on the other side of the plasma generation vessel 2. And an ion extraction slit 4 provided on the wall surface of the plasma generation container 2. Near the outlet of the ion extraction slit 4, an extraction electrode 14 for extracting an ion beam 16 from the plasma 12 generated in the plasma generation container 2 is provided. A magnetic field 19 is applied to the inside of the plasma generation container 2 by an electromagnet 18.

An ion source material (that is, a material that is a source of the ion beam 16) 24 is introduced into the plasma generation vessel 2 through an introduction port 6 provided on a wall surface thereof. The ion source material 24 is a gas supplied from a gas source (not shown) or a gas (vapor) supplied by evaporating a solid by an evaporation source (not shown).

In the ion source 1, the filament 8 is energized by a filament power supply 20 while evacuating the inside and outside of the plasma generation container 2 and introducing the ion source substance 24 into the plasma generation container 2 at an appropriate flow rate. When heated to generate thermoelectrons, the filament 8
By applying an arc voltage from an arc power supply 22 between the plasma source and the plasma generation container 2 to generate an arc discharge between the two, the ion source material 24 is ionized and the plasma 12
Is generated. Then, the ion beam 1 containing the ions of the elements constituting the ion source material 24 is generated from the plasma 12.
6 can be pulled out.

The reflection electrode 10 repels thermionic electrons emitted from the filament 8 to increase the ionization efficiency of the ion source material 24 and thus the generation efficiency of the plasma 12. In addition, the magnetic field 19 generated by the electromagnet 18 also moves so that thermoelectrons are wound around the lines of magnetic force, thereby increasing the effective range.

The ion beam 16 extracted as described above is subjected to mass separation, acceleration / deceleration, scanning,
After being subjected to a process such as convergence, the object 26 is irradiated with the object and used for a process such as ion implantation. Although the irradiated object 26 is shown near the ion source 1 for convenience of illustration, it is usually arranged at a position considerably downstream of the ion source 1 in practice.

[0008] The ion beam 1 irradiated to the irradiation object 26
It is desirable that the beam amount of No. 6 is temporally stationary.
One of the means for achieving this is to keep the beam amount (that is, beam current) of the ion beam 16 extracted from the ion source 1 temporally constant.

An ion beam 16 extracted from the ion source 1
(1) arc voltage (output voltage of arc power supply 22), (2) arc current (output current of arc power supply 22), (3) supply amount of ion source material 24, (4) It is necessary to keep operating parameters of the ion source 1 constant, such as a current flowing through the electromagnet 18 (specifically, a coil not shown). The values of these operating parameters can be set and adjusted through a control device such as the control device 28, for example. Arc voltage, arc current,
For the electromagnet currents, their actual values will be close to the values set through controller 28.

[0010] However, the actual value of the supply amount of the ion source material into the plasma generation vessel 2 is not always close to the set value. This will be described in detail below.

The ion source material 24 is usually introduced into the plasma generation vessel 2 through the inlet 6. As described above, the ion source material 24 is a gas supplied from a gas source or a gas supplied by evaporating a solid by an evaporation source. These gases usually have a flow control mechanism that keeps the supply from the gas source constant,
The supply amount is controlled by a temperature control mechanism that keeps the temperature of the evaporation source constant. However, the ion source material can be supplied into the plasma generation container 2 from a route other than such a route. It is adsorbed on the wall surface (inner wall surface; the same applies hereinafter) of the plasma generation vessel 2 or adheres in the form of a film (hereinafter, this is simply referred to as adhesion). Etc.).

As an example, in the plasma generation container 2 immediately after the maintenance, unnecessary substances mainly including water molecules existing in the atmosphere are attached. In this case, when the operation of the ion source is started, the temperature of the plasma generation container 2 increases, and accordingly, the unnecessary substances are gradually released from the wall surface of the plasma generation container 2. In this example, water molecules, which are the main components of the unnecessary substance, are dissociated and ionized to generate ions such as H ⁺ , H ₂ ⁺ , O ⁺ , and OH ⁺ , which are ionized by the ion source substance 24. The ion beam 16 is extracted together with the ion beam. As the temperature of the plasma generation container 2 increases, the emission rate of the unnecessary substance from the wall surface increases, while the amount of the unnecessary substance held on the wall surface decreases due to the release. Therefore, the amount of the unnecessary substance released from the wall surface changes with the elapse of the operation time of the ion source 1 due to these balances.

This means that the amount of supply of the ion source material in a broad sense (the combination of the true ion source material 24 and the unnecessary material emitted from the wall surface of the plasma generation container 2) into the plasma generation container 2 is as follows. This means that the temperature changes depending on the temperature of the plasma generation container 2.

As another example, there is a case where the operation is started from a state where the inside of the plasma generation vessel 2 is in a vacuum state and the plasma generation vessel 2 is at room temperature (this is called a cold start). At this time, when a gas such as PH ₃ (phosphine) or AsH ₃ (arsine) or a metal compound gas such as In (CH ₃ ) ₃ (trimethylindium) is used as the ion source substance 24, phosphorus, arsenic, indium, or the like is used. Metal may adhere to the inner wall of the plasma generation vessel 2 in large quantities. During the operation of the ion source 1, the ion source substance 24 and its components are constantly adhered to the inner wall of the plasma generation vessel 2, while being re-evaporated. When the operation of the ion source 1 is started in a state where the temperature of the plasma generation container 2 is low, the speed of ionization and the like adhering to the wall surface is faster than the speed of re-evaporation. They are accumulating. When the operation time elapses and the temperature of the plasma generation vessel 2 rises, re-evaporation becomes active and the amount of the substance released from the wall surface temporarily increases. When the re-evaporation rate exceeds the deposition rate, the total amount of the substances deposited on the wall surface starts to decrease and finally converges to a certain amount. Accordingly, the supply amount of the substance released from the wall surface also decreases, and eventually converges to a certain amount. This phenomenon also means that the supply amount of the ion source material into the plasma generation container 2 changes with the temperature change of the plasma generation container 2.

As described above, there is an ion source substance that is released into the plasma generation container 2 from a path other than the regular path (the path from the inlet 6), and the amount of the released ion source material varies with the temperature change of the plasma generation container 2. Change. this is,
This means that the total supply amount of the ion source material into the plasma generation container 2 changes with the temperature change of the plasma generation container 2. Due to such causes, the ion beam 16
May involuntarily fluctuate, thereby taking a long time to stabilize the ion beam amount.

[0016]

On the other hand, in Japanese Patent Application Laid-Open No. Hei 5-325871, a heater for forcibly heating the plasma generation container is provided on the wall of the plasma generation container (arc chamber) (the heater is embedded). ) An ion source has been proposed, which makes it possible to shorten the ion beam startup time.

However, in this method, it is necessary to newly provide a heater, a power supply for the heater, and a feedthrough for guiding electric power from the power supply for the heater in the atmosphere to the heater in the vacuum, and the configuration becomes complicated.

The plasma generating container is usually a hexahedron, and each surface is provided with an ion extraction slit or an insulator which hinders the heater arrangement. It is not easy to uniformly heat the entire wall of the plasma generation container. If there is a portion where the heating temperature is low, the time required for the ion beam amount to stabilize becomes longer.

Further, the plasma generation vessel has a relatively short life (for example, it may be replaced in several maintenance cycles) and needs to be replaced frequently, and it is not necessary to attach or bury a heater every time. Very laborious and impractical. If the plasma generation container is replaced while the heater is attached or buried, the cost is increased because the heater is provided.

Accordingly, it is a main object of the present invention to provide a means for shortening the time until the ion beam amount is stabilized at the start of the operation of the ion source without providing an additional component such as a heater.

[0021]

According to a method of operating an ion source according to the present invention, when starting operation of an ion source and extracting an ion beam, the ion source is operated before an operation of extracting an ion beam of a desired amount is started. The preheating of the plasma generation container is performed by supplying plasma generation power larger than the plasma generation power input when extracting the amount of ion beam into the plasma generation container of the ion source to generate plasma. It is characterized by performing.

The above-mentioned preheating is specifically performed in any of the following cases. In each of these cases, the total supply amount of the ion source material into the plasma generation container changes relatively greatly with the temperature change of the plasma generation container.

(1) When the operation of the ion source is started after exposing the inside of the plasma generation container to the atmosphere for maintenance or the like (that is, when the ion source is started from a stopped state) to extract the ion beam.

(2) When starting the operation of the ion source from a stopped state in which the inside of the plasma generation vessel is in a vacuum state but the plasma generation vessel is at or near room temperature to extract an ion beam. The stopped state refers to a state in which the plasma and the ion beam are not generated.

(3) Irrespective of the temperature state of the plasma generation container, the operation of the ion source is restarted after switching the ion source material to be introduced into the plasma generation container, and the ion of a different ion species is used. When pulling out the beam.

According to the above-mentioned operating method, the temperature of the plasma generation vessel is quickly raised by the preheating to shorten the time until the amount of the ion source material supplied into the plasma generation vessel is stabilized. Can be. As a result, it is possible to reduce the time required until the amount of the ion beam is stabilized when the operation of the ion source is started and the ion beam is extracted.

In addition, since the preheating is performed by generating a plasma by applying a large amount of power for plasma generation, there is no need to provide an additional component such as a heater. Therefore, the configuration of the ion source does not need to be complicated, and the cost of the ion source does not increase. In addition, since the plasma generation vessel is preheated by generating a plasma by supplying a large amount of power for plasma generation, and the inner wall of the plasma generation vessel is directly heated from the inside, the entire inner wall of the plasma generation vessel can be completely heated. It becomes easy to heat uniformly and efficiently.

It is most preferable that the preheating is performed immediately before the operation for extracting the desired amount of ion beam is started. In that case, preheating can be used most effectively.

The electric power applied at the time of the preheating is preferably, for example, about 1.5 to 2 times the electric power applied at the time of extracting a desired amount of ion beam. If it is less than 1.5 times, the effect of preheating is small, and if it exceeds twice, the capacity of the power source for plasma generation may have to be increased for preheating.

The time for performing the preheating is preferably, for example, about 2 to 5 minutes. If the heating time is less than 2 minutes, the effect of the preheating is small, and if the heating time exceeds 5 minutes, the time required for the preheating is too long, and the effect of shortening the time until the beam amount is stabilized is reduced.

The ion beam irradiation apparatus according to the present invention
A control device for performing the above-described preheating operation at the start of the operation of the ion source is provided.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an operation method of an ion source according to the present invention will be described with reference to an example of an ion source 1 of an ion beam irradiation apparatus shown in FIG.

First, as an example, consider the case of a cold start in which the operation of the ion source 1 is started from a state where the plasma generation vessel 2 is at room temperature. The ion source substance 24 is AsH ₃ gas.

The operating parameters are as follows: arc voltage is 60 V;
The arc current is 0.8 A. At this time, the electric power P supplied for generating the plasma 12 into the plasma generation container 2 is given by the following equation.

[0035]

P = (arc current × arc voltage) + (filament current × filament voltage)

The filament current and the filament voltage are the outputs of the filament power supply 20. Usually, the filament power supply 20 automatically adjusts the power supplied to the filament 8 so that the arc discharge current generated mainly by thermionic emission from the filament 8 maintains a predetermined value. Typical filament current and filament voltage under the above conditions are 120 A and 2.0 A, respectively.
About V.

Accordingly, the electric power P ₁ supplied into the plasma generation vessel 2 at the time of the above operation parameters is as follows.

[0038]

P ₁ = (0.8 × 60) + (120 × 2) = 2
88 [W]

FIG. 2 shows the relationship between the power input into the plasma generation container 2 and the temperature of the plasma generation container 2. According to this, it can be seen that the temperature (T ₁ ) of the plasma generation container 2 reaches about 450 ° C. (723 K) by the input power P ₁ of 288 W.

FIG. 3 shows the vapor pressure with respect to the temperature of various substances. According to this, the vapor pressure of arsenic at 723K is 1 × 1
It is understood that 0 ⁴ Pa approximately.

With the above parameters, when the operation of the ion source 1 is started from a state where the plasma generation vessel 2 is at room temperature, it is necessary to adjust the beam amount to a target amount (a desired value) after starting to extract the ion beam 16. About 21 hours
Minutes.

On the other hand, when the operation of the ion source 1 is started from a state where the plasma generation vessel 2 is sufficiently warmed, the time required for adjusting the beam amount of the ion beam 16 to the target amount is typically 6 hours. It is about 7 minutes.

As described above, when the operation of the ion source 1 is started from a state in which the plasma generation container 2 is at room temperature, the total supply amount of the ion source material fluctuates effectively due to a change in the temperature of the plasma generation container 2. Thereby, the beam amount of the ion beam 16 fluctuates involuntarily. The difference in the required time occurs because the beam amount is adjusted in accordance with the involuntary fluctuation.

Next, an embodiment in which preheating is performed according to the present invention will be described.

Before starting the operation of extracting the desired amount of ion beam 16, for example, the plasma generation vessel 2 and the extraction electrode 1
Before applying a withdrawal voltage between the arc voltage and the
Preheating is performed for 2 minutes at 0 V and an arc current of 3 A. Typical filament current and filament voltage under these conditions are 140 A and 2.7, respectively.
About V. Thus input power P ₂ to the plasma generating chamber 2 when the operating parameter is obtained by the following equation.

[0046]

P ₂ = (3 × 60) + (140 × 2.7) = 5
58 [W]

At this time, the temperature (T
₂ ) is about 600 ° C. (873 K) from FIG.
Subsequent to the preheating, an operation for extracting a desired amount of the ion beam 16 is started. The operating parameters at this time are, for example, as described above, an arc voltage of 60 V and an arc current of 0.
8 A, the filament current is 120 A, the filament voltage is 2.0 V, and the input power P _{1 in} this case is 288 W
And the temperature T ₁ of the plasma generation vessel 2 is 450 ° C. as described above. FIG. 4 schematically shows the change of the preheating, the input power and the temperature of the plasma generation vessel 2 thereafter.
Shown in

Temperature T of plasma generating vessel 2 during preheating
Vapor pressure of arsenic when the ₂ is 600 ° C. (873 K), from 3, becomes approximately 1 × 10 ⁵ Pa, the input power P ₁
It will be about 10 times the time. Accordingly, the release rate at which arsenic is released from the wall surface of the plasma generation container 2 is also about 10 times that at the input power P _{1, and the} time required for the amount of the ion source material supplied into the plasma generation container 2 to stabilize. Can be shortened, and the time required until the beam amount of the ion beam 16 extracted from the ion source 1 becomes stable can be shortened.

In fact, in the case of this embodiment, the operation of the ion source 1 is started from the state where the plasma generation vessel 2 is at room temperature,
The time required until the beam amount of the ion beam 16 was adjusted to the target amount was about 11 minutes including the above-mentioned preheating time of 2 minutes, and was about 1 minute as compared with the case where preheating was not performed.
A reduction of 0 minutes could be achieved. In other words, the required time was reduced by about half.

Further, according to this operation method, there are the following advantages as compared with the technique of heating the plasma generating vessel by the heater as described in the above-mentioned Japanese Patent Application Laid-Open No. 5-325871.

(1) The preheating of the plasma generation vessel 2
Since the plasma 12 is generated by applying a large amount of power for plasma generation (the input power P shown in Equation 1 in the above embodiment), additional components such as a heater, a heater power supply, and a feedthrough are provided. No need. Therefore,
The configuration of the ion source 1 is not complicated, and the cost of the ion source is not increased. In addition, replacement of the plasma generation container 2 can be easily (without doing anything).

(2) This is a method of preheating the plasma generation container 2 by supplying a large amount of power for plasma generation into the plasma generation container 2 to generate the plasma 12. Since the wall of the plasma generation container 2 is heated three-dimensionally and the heat from the three-dimensional plasma 12 and the like heats the entire inner wall of the plasma generation container 2 more easily than the heater. become.

(3) Since the inner wall surface of the plasma generation vessel 2 can be directly heated from the inside, the heating efficiency is higher than when heating is performed from the outside of the plasma generation vessel 2 like a heater.

The above-mentioned operation method uses the power supplied for plasma generation for preheating, and power is supplied for plasma generation in any type of ion source. Can be widely applied to ion sources other than the ion source 1. For example,
(1) Freeman ion source using rod-shaped filaments, (2) Multipole magnetic field (cusp magnetic field) for plasma confinement
, A high frequency ion source using high frequency (including microwave) power for plasma generation, and (4) an ECR ion source using ECR (Electron Cyclotron Resonance) for plasma generation. be able to. In the case of the ion sources of (1) and (2), the sum of the filament heating power and the arc discharge power is the power for plasma generation, as in the case of the burner type ion source.
In the cases (3) and (4), the high frequency power (or microwave power) to be supplied is power for plasma generation.

Further, a control device for automatically performing the preheating operation at the start of the operation of the ion source as described above may be provided.
In the example of FIG. 1, the control device 28 is the control device.

[0056]

As described above, according to the present invention, the preheating increases the temperature of the plasma generation vessel at an early stage, until the amount of the ion source material supplied into the plasma generation vessel becomes stable. Time can be reduced. As a result, it is possible to reduce the time required until the amount of the ion beam is stabilized when the operation of the ion source is started and the ion beam is extracted.

Further, according to the present invention, the following advantageous effects can be obtained as compared with the technique of heating the plasma generating vessel by the heater.

(1) Since the preheating of the plasma generation vessel is performed by generating plasma by applying a large amount of power for plasma generation, it is not necessary to provide additional components such as a heater, a power supply for the heater, and a feedthrough. . Therefore,
The configuration of the ion source is not complicated, and the cost of the ion source is not increased. Further, it is possible to easily cope with the exchange of the plasma generation container.

(2) This is a method in which a large amount of power for plasma generation is supplied into the plasma generation container to generate plasma, thereby preheating the plasma generation container. The plasma is three-dimensionally generated in the plasma generation container. Since the wall of the plasma generation container is heated by the heat from the three-dimensional plasma or the like, it becomes easier to uniformly heat the entire inner wall of the plasma generation container as compared with the heater.

(3) Since the inner wall surface can be directly heated from the inside of the plasma generation container, the heating efficiency is higher than when heating is performed from the outside of the plasma generation container like a heater.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of the vicinity of an ion source of an ion beam irradiation apparatus.

FIG. 2 is a diagram illustrating an example of a relationship between input power and a temperature of a plasma generation container.

FIG. 3 is a diagram showing the vapor pressure with respect to the temperature of various substances.

FIG. 4 is a diagram showing an example (A) in which the input power is changed according to the operation method according to the present invention, and an outline (B) of a change in the temperature of the plasma generation vessel at that time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion source 2 Plasma generation container 12 Plasma 16 Ion beam 24 Ion source material 26 Irradiated object 28 Control device

Claims (2)

[Claims] When starting operation of an ion source and extracting an ion beam, power for plasma generation to be applied when extracting the target amount of ion beam before starting an operation of extracting the target amount of ion beam. A method for operating an ion source, characterized in that a plasma generation container is preheated by applying a larger power for plasma generation into a plasma generation container of the ion source to generate plasma. 2. An ion beam irradiation apparatus for irradiating an object to be irradiated with an ion beam extracted from an ion source, the operation of extracting an ion beam of a desired amount when starting the operation of the ion source and extracting the ion beam. before,
By generating a plasma by inputting plasma generation power larger than the plasma generation power input when extracting the target amount of ion beam into the plasma generation container of the ion source, the plasma generation container is protected. An ion beam irradiation apparatus comprising a control device for performing a heating operation.