JPH10270194A - Charged particle accelerator - Google Patents

Abstract

(57) [Summary] To change the acceleration voltage of a charged particle accelerator at high speed and with high accuracy. An accelerating power source is arranged between a charged particle source and an accelerating electrode, and a voltage applying means capable of changing a voltage between the accelerating electrode and a ground potential is provided. [Effect] The tracking performance and the high stability when the acceleration voltage of the charged particle accelerator is changed can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle accelerator or a charged particle irradiation device provided with the accelerator.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional charged particle accelerator.
The electron beam accelerator of the present invention will be described as an example.

An electron source 1 is heated by a heating power supply 5 to generate electrons. The electrons are converged by the voltage applied to the electrode 2 from the bias power supply 6. An acceleration voltage is applied to the electron source 1 and the electrode 4 by an acceleration power supply 7. The electrons are accelerated by the accelerating voltage. The electron source 1, the electrode 2, and the electrode 4 are wrapped in a vacuum insulating container 3, and the inside of the vacuum insulating container 3 is evacuated (for example, Japanese Patent Application Laid-Open No. 3-141543,
As described in JP-A-61-200699).

[0004]

The acceleration voltage is controlled by an acceleration power supply 7.
To the electron source 1 and the electrode 4. In the case of a one-stage accelerator, the electrode 4 is at the ground potential. The acceleration power supply 7 requires a high degree of stability, but the response when changing the voltage is poor due to the influence of the time constant of the element incorporated in the acceleration power supply 7, and this problem is more remarkable as the power supply generates a higher acceleration voltage. Met.

An object of the present invention is to provide a charged particle accelerator capable of solving the above problems.

[0006]

According to the present invention, there is provided a charged particle irradiation apparatus comprising a charged particle source and an accelerating electrode for accelerating charged particles generated from the charged particle source. An accelerating power source is arranged between the charged particle source and the accelerating electrode, and a voltage applying means capable of changing a voltage between the accelerating electrode and a ground potential is provided.

According to this configuration, at least the charged particle source,
A desired acceleration voltage can be obtained without changing the voltage in a closed circuit including the acceleration electrode and the acceleration power supply.
In addition, by providing a voltage applying unit that floats the accelerating electrode from the ground potential and can vary the voltage between the accelerating voltage and the ground potential, a narrow voltage range including the variation of the accelerating voltage can be covered by the voltage applying unit. The ability to follow changes is improved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to a one-stage acceleration type electron beam accelerator shown in FIG.

The electron source 1 is heated by a heating power supply 5 to generate electrons. These electrons are converged by the voltage applied to the first electrode 2 from the bias power supply 6. An acceleration voltage is applied between the electron source 1 and the second electrode 4 by an acceleration power supply 7. The electrons are accelerated by the accelerating voltage.

The electron source 1, the first electrode 2 and the second electrode 4 are wrapped in a vacuum insulating container 3, and the inside of the vacuum insulating container 3 is evacuated (a means for evacuating is not shown).

The second electrode 4 and the vacuum insulating container 3 are insulated from the ground potential 8 by insulating means 9. The acceleration power supply 7 supplies an acceleration voltage to the electron source 1 based on the potential of the second electrode 4.

In the embodiment of the present invention, the accelerating electron beam generating section insulated from the ground potential 8 by the insulating means 9 is connected to the ground potential 8.
And a voltage applying means 10 between them. As a result, the acceleration voltage applied to the electron source 1 is the sum of the output voltage of the acceleration power supply 7 and the voltage output by the voltage application means 10. The voltage applying means 10 is a variable power supply capable of changing the applied voltage.

With the above configuration, an arbitrary acceleration voltage can be obtained without changing the set voltage of the acceleration power supply 7. That is, while the acceleration voltage ripple and the acceleration voltage in the closed circuit including the electron source 1, the second electrode 4 as the acceleration electrode, and the acceleration power source 7 are kept stable, the acceleration voltage of the electron source 1 with respect to the ground potential is applied to the voltage application means 10 Thus, a desired acceleration voltage can be set.

Generally, a charged particle beam irradiation apparatus provided with such a charged particle source requires an extremely high accelerating voltage. This is because, for example, in the case of a scanning electron microscope (SEM), the obtained data is different due to the fluctuation of the acceleration energy, which causes a problem that a desired detection result cannot be obtained.

If it is assumed that the closed circuit includes voltage displacement means, the closed circuit is constituted by a high-stability high-voltage generating power supply represented by the acceleration power supply 7, so that the time constant of the closed circuit is reduced. Even if the voltage is largely varied, a desired acceleration voltage cannot be obtained with high accuracy.

In this embodiment, the portion for generating and accelerating charged particles is floated above the ground potential, and an accelerating voltage displacing means is provided between the portions to change the accelerating voltage while maintaining the closed circuit in a stable state. It becomes possible to do.

Further, in this embodiment, a fixed value of the acceleration voltage can be generated by the acceleration power supply 7 and a fluctuation can be generated by the voltage applying means 10. This makes it possible to improve the followability of the voltage displacement.

Generally, a cockcroft Wellington circuit (CW circuit) is used in the acceleration power supply 7 to obtain a high DC voltage. A Cockcroft Wellington circuit (CW circuit) applies an AC voltage at several tens of Khz and rectifies and boosts it to a DC voltage, and therefore has a unique ripple voltage. To reduce this ripple voltage, a high-resistance filter and a capacitor are required. Further, in order to stabilize the acceleration voltage, the time constant of the closed circuit is increased due to a high-resistance detection resistor or the like, thereby deteriorating the response of the closed circuit.

It can be said that the smaller the time constants of these elements are, the better the follow-up property at the time of voltage displacement is, but high stability is required on the other hand. In the present invention, by driving the entire closed circuit with a separate power supply, a power supply with a small corresponding voltage and a small time constant can be formed. For example, when the output voltage of the acceleration power supply 7 is 100 kV and the stability is 2 ppm, the allowable voltage fluctuation is 0.2 V. If the maximum applied voltage of the voltage applying means 10 is set to 1 kV, the stability for obtaining the same allowable voltage fluctuation is 200 ppm, which is a two-digit stability.
Similarly, the filter capacity to be used can be reduced to reduce the voltage fluctuation (ripple voltage).

That is, it can be seen that the smaller the corresponding voltage of the power supply for the voltage displacement becomes, the easier the stability becomes and the better the followability when the voltage changes.

According to the configuration disclosed in the embodiment of the present invention, most or a fixed portion of the acceleration voltage is applied by the acceleration power supply 7, and a voltage (small voltage) including the displacement is applied by the voltage application means 10. It is possible to set a power supply suitable for obtaining good follow-up performance.

As described above, according to the embodiment of the present invention, it is possible to obtain not only the stability of the acceleration voltage but also excellent followability when the voltage changes.

In this embodiment, a thermionic emission type electron source is employed, but the invention is not limited to this. For example, an electron source using a field emission type electron gun may be used.

Next, another embodiment of the present invention will be described with reference to FIG. A means 11 for arbitrarily changing the amplitude and frequency of the applied voltage of the voltage applying means 10 is provided in the configuration of FIG. 2 described above.

Thus, the amplitude and the frequency can be independently set to arbitrary values. The means 11 for arbitrarily changing the amplitude and frequency makes it possible to change the output voltage of the voltage applying means 10 at high speed and with high accuracy, and to change the acceleration voltage of the electron source 1 at high speed and with high accuracy. it can.

The interface means 12 can output an amplitude signal corresponding to the amplitude and a synchronization signal corresponding to the frequency to the outside, so that the external device operates in synchronization with the acceleration voltage at the amplitude and the frequency. Conversely, the amplitude and frequency can be driven by an external signal, and the voltage applying means 10 can be operated in synchronization with an external signal from an external device. Thus, for example, by synchronizing with the image capturing of the electron microscope image by the imaging means, it can be used for the alignment of the electron microscope and the like.

Still another embodiment of the present invention will be described with reference to FIG. This means is provided with means 13 for electrically turning on / off between the electron beam accelerator and the ground potential 8 in the configuration of FIG.
When the voltage applying unit 10 is used, the ON / OFF unit 13 is turned ON, and when the voltage applying unit 10 is not used, the ON / OFF unit 13 is turned OFF.

An electron beam accelerator and a ground potential 8 are added to the configuration of FIG.
The discharge tube 14 or an equivalent of the discharge tube 14 is provided to prevent application of an overvoltage during the discharge. With such a configuration, the voltage applying means 10 due to abnormal discharge in the electron beam accelerator is provided.
To prevent overvoltage.

Another embodiment of the present invention will be described with reference to FIG. In the configuration disclosed in FIG. 5, in addition to the configuration disclosed in FIG. 4, a conductive cover 15 surrounding components having a potential higher than the ground potential is provided. The conductive cover 15 is formed of an insulating member on the side surrounding the components of the charged particle accelerator and the insulating means 9. This insulating member has a sufficient withstand voltage function with respect to the voltage applied by the voltage applying means 10.

With the above configuration, it is possible to ensure safety for a portion connected to the ground potential 8 and to which a high voltage is applied.

Although the embodiments of the present invention have been described with reference to the single-stage acceleration type of thermionic beam accelerator, the multi-stage acceleration type of thermionic beam accelerator as well as the single-stage or multi-stage acceleration type of the electron beam accelerator are described. It goes without saying that the present invention can be applied to a field emission type electron beam accelerator.

[0032]

According to the present invention, a charged particle beam accelerator,
Alternatively, the acceleration voltage of the charged particle beam irradiation device can be varied with high followability and high accuracy while maintaining high accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a conventional charged particle accelerator.

FIG. 2 is a diagram showing an example of a charged particle accelerator according to the present invention.

FIG. 3 is a diagram showing an example in which the charged particle accelerator of the present invention is provided with means for arbitrarily changing the amplitude.

FIG. 4 is a diagram showing an example in which a discharge tube is provided in the charged particle accelerator of the present invention.

FIG. 5 is a view showing the charged particle beam accelerator according to the present invention provided with a conductive cover.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron source, 2 ... 1st electrode, 3 ... Vacuum insulation container, 4 ... Second electrode, 5 ... Heating power supply, 6 ... Bias power supply, 7 ... Acceleration power supply, 8 ... Ground potential, 9 ... Insulation means, 10 ... Voltage applying means, 11 means for arbitrarily changing amplitude and frequency, 12
... Interface, 13 ... Means for turning ON / OFF electrically, 14 ... Discharge tube, 15 ... Conductive cover.

Continued on the front page (72) Inventor Ryuichi Shimizu 3 1-22, Nyoinya, Minoh-shi, Osaka (72) Inventor Takashi Ikuta 1-1-1 Koei Heights, Shimonakajo-cho, Ibaraki-shi, Osaka 307

Claims (8)

[Claims] 1. A charged particle irradiation apparatus comprising a charged particle source and an acceleration electrode for accelerating charged particles generated from the charged particle source, wherein an acceleration power source is arranged between the charged particle source and the acceleration electrode. And a voltage applying means capable of changing a voltage between the acceleration electrode and a ground potential. 2. A charged particle irradiation apparatus according to claim 1, further comprising means for arbitrarily changing the amplitude and / or frequency of the voltage applied by said voltage applying means. 3. The apparatus according to claim 2, wherein the means for arbitrarily changing the amplitude and / or frequency of the voltage applied by the voltage applying means includes means for controlling the voltage based on amplitude signal information and synchronization signal information from outside. A charged particle irradiation apparatus, comprising: a charged particle irradiation apparatus; 4. The apparatus according to claim 2, wherein the means for arbitrarily changing the amplitude and / or frequency of the voltage applied by the voltage applying means includes changing the amplitude and / or frequency of the voltage applied between the acceleration electrode and a ground potential. A charged particle irradiation apparatus comprising means for outputting a corresponding synchronization signal and / or amplitude signal. 5. The charged particle irradiation apparatus according to claim 1, further comprising a switch for conducting between the acceleration electrode and the ground potential. 6. A charged particle irradiation apparatus according to claim 1, further comprising a discharge tube or an equivalent thereof between said acceleration electrode and said ground potential. 7. A conductive cover according to claim 1, further comprising: a conductive cover disposed between each of the constituent elements of the charged particle beam irradiation apparatus and the ground potential. A charged particle irradiation apparatus, wherein an insulating member is formed and the ground potential is connected to the conductive cover. 8. A charged particle accelerator comprising a charged particle source and an acceleration electrode for accelerating charged particles generated from the charged particle source, wherein an acceleration power source is arranged between the charged particle source and the acceleration electrode. And a voltage applying means capable of changing the voltage between the acceleration electrode and a ground potential.