JP2522222B2 - Electrostatic accelerator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic accelerator for generating a high energy ion beam, and more particularly to an accelerator applicable to the fields of analysis using a high energy ion beam and semiconductor manufacturing.

[0002]

2. Description of the Related Art In a tandem electrostatic accelerator, generally, as shown in a block diagram of FIG. 5, positive ions extracted from an ion source 1 are negatively ionized by a charge conversion cell 2, and the negative ions are converted into negative ions. Is guided to the inside from one end side of the accelerating tube 3 to which a positive high voltage is applied at the center at the earth potential, and the negative ions are converted into positive ions in the central part of the accelerating tube 3. The target 4 can be irradiated with a high energy ion beam by accelerating the ions again toward the other end.

By the way, positive low energy ions (several ke
A method of passing through metal vapor is often used for charge conversion of about V), and this method is also applied to the charge conversion cell 2 in the electrostatic accelerator described above.

In such a charge conversion cell, as shown in the sectional view of FIG. 6, an ion inlet 21a and an ion outlet 2 are provided.
In the cell body (boiler) 21 having 1b, Li, Na, C
An evaporation metal material M such as s, Rb or the like is accommodated, and the inside of the cell body 21 is filled with metal vapor by heating this with a heater 22, and positive ions from the ion source 1 pass through the vapor. By doing so, negative ions are generated.

In the electrostatic accelerator using such a charge conversion cell, when the metal vapor for charge conversion diffuses out of the cell, there is a problem that the surrounding components are contaminated and the device is supported.

Therefore, in the conventional device of this type,
As shown in FIG. 6 , the ion inlets 21 a, 2 of the cell body 21
1b and other appropriate slits S ... Measures have been taken to minimize the spread of.

There is also an apparatus in which an electrostatic deflection device is provided before and after the charge conversion cell to guide the ion beam in a direction different from the diffusion direction of the metal vapor to prevent the device from being contaminated.

[0008]

However, it cannot be said that the conventional measures as described above are sufficient, and the surrounding components are still contaminated by metal vapor, which makes maintenance of the device complicated. There is a problem. Also,
The measures to provide the electrostatic deflection device and the like have a problem that the beam trajectory is affected and the configuration of the device becomes complicated.

The object of the present invention is to greatly reduce the metal vapor diffused from the charge conversion cell of the electrostatic accelerator to the outside with a simple structure, to reduce the pollution of the surroundings and to extend the maintenance cycle of the apparatus. The object is to provide an electrostatic accelerator capable of processing.

[0010]

In order to achieve the above object, an electrostatic accelerator according to the present invention is provided with an ion beam at an ion inlet and an outlet of a charge conversion cell that produces metal vapor therein.
It is characterized by the provision of a shutter mechanism that opens only when the camera is used .

[0011]

For example, in an electrostatic accelerator in an analyzer or the like, the ratio of the time for effectively using the ion beam in the time from operating (heating or raising) the charge conversion cell to stopping (cooling) is Generally few.

The present invention has been made in consideration of this point, and the shutter mechanism provided at the entrance and exit of the ions in the charge conversion cell is opened only while the ion beam is used, and closed at other times. It is possible to reduce the diffusion of metal vapor to the outside.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of the essential parts of an embodiment of the present invention. In this embodiment, the ion source, the accelerating tube, and the target are equivalent to those of the conventional electrostatic accelerator shown in FIG.

Further, the charge conversion cell 2 itself has an ion inlet 21a and an ion outlet 21 similar to the conventional one shown in FIG.
b, a cell main body 21 having slits S ... S, and a heater 22 provided outside the accommodating portion of the evaporation metal material M of the cell main body 21.

The ion inlet 21a and the ion outlet 21b of the charge conversion cell 2 are constructed so that they can be opened and closed by the shutter mechanism 5. That is, the shutters 5a and 5b are provided outside and adjacent to the ion inlet 21a and the ion outlet 21b. The shutters 5a and 5b are connected to the piston rod of the shutter driving cylinder 52 by the connecting member 51, respectively. When the shutter driving cylinder 52 is driven, the shutters 5a and 5b are interlocked with each other so that both the ion inlet 21a and the ion outlet 21b are closed and both are opened. It is configured so that it can take either state.

In the above-mentioned structure, the shutters 5a and 5 are heated in a state where the evaporation metal material M is heated by driving the heater 22 and the cell body 21 is filled with the metal vapor.
In the state where b is opened, like the conventional electrostatic accelerator, positive ions are guided from the ion inlet 21a into the cell body 21 and passed through the metal vapor to be negatively ionized, and the negative ions are made to pass through the ion outlet 21b. It can be guided into the accelerating tube 3 via.

When the shutters 5a and 5b are closed, the metal vapor in the cell body 21 can be prevented from diffusing to the outside. The shutter driving cylinder 52 is driven in synchronization with the timing of using the ion beam, as illustrated in the chart showing the operation timing thereof in FIG. 2, and, for example, in an analyzer or the like, only when the ion beam is used for measurement or the like. By driving the shutters 5a and 5b so that they are opened and the shutters 5a and 5b are closed during standby, diffusion of metal vapor to the outside is greatly reduced.

The shutter driving cylinder 52 may be driven manually, but by controlling it in conjunction with a beam request signal in, for example, an analyzer, the opening time of the shutters 5a and 5b is shortened as much as possible. Is preferable.

Further, by utilizing the shutter mechanism of the present invention,
By providing one or both of the shutter 5a and the shutter 5b with a mass detection function, it is possible to control the heating temperature by the heater 22 and predict the replenishment time of the evaporation metal material.

That is, as shown in FIG. 3, for example, a crystal oscillator 6 is provided on the shutter 5b and its vibration frequency is monitored, so that the change amount of the vibration frequency is determined by the total mass of the crystal oscillator 6 and the shutter 5b. Since it is proportional to the amount of change, it is possible to know the amount of metal attached to the shutter 5b when the shutter 5b is closed. This temporal change in the amount of deposited metal can serve as information for estimating the amount of metal evaporated in the cell body 21, and thus the measurement result can be used for heating temperature control by the heater 22.
In addition, from the change over time of the amount of deposited metal, the cell body 21
It is possible to know the decrease of the evaporation metal material M in the inside, and before the charge conversion efficiency is lowered, the evaporation metal material M is not detected.
Can be replenished. Incidentally, the replenishment of the evaporation metal material M could only be performed after it was known that the charge conversion efficiency of the ion beam was lowered in the conventional apparatus.

Further, the shutters 5a and 5b can be opened and closed individually, and both shutters 5a and 5b are opened.
Beam adjustment can be easily performed by providing b with a current detection function.

That is, as shown in FIG. 4, for example, the shutters 5a and 5b are electrically insulated from the outside by an insulator 7 and are connected to an ammeter 9 by a conductor 8, and the shutter 5a on the inlet 21a side is formed. When the ion beam current guided to the shutter 5a is measured in the closed state, and the ion beam current guided to the shutter 5b is measured with the shutter 5a opened and the shutter 5b on the outlet 21b side is closed, the charge conversion cell 2 Since it is possible to know the passing efficiency of the positive ion beam due to, it becomes easy to adjust the beam of the apparatus based on the result.

As the actuator for driving the shutters 5a, 5b, in addition to air or an electromagnetic cylinder,
It is needless to say that an arbitrary motor or the like can be used, and the opening / closing movement of the shutters 5a and 5b may be linear movement as well as rotary movement.

As described above, according to the present invention, since the ion entrance and the exit of the charge conversion cell in the electrostatic accelerator are provided with the shutter mechanism which is opened only when the ion beam is used , Heating or raising the charge conversion cell
Ion bee occupies the time from warming to cooling
In light of the fact that the percentage of time spent using mobile phones is generally low,
The amount of metal vapor in the cell diffused outside the cell is greatly reduced, and the contamination of the components outside the cell is extremely reduced. As a result, the maintenance cycle of the device becomes long, and it is possible to reduce the maintenance work and improve the operating rate of the device.

Further, in the present invention, since the shutter is mechanically opened and closed and no electric field or magnetic field is applied, the beam orbit is not affected, and the above-mentioned effects are achieved with a relatively simple structure. be able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram of essential parts of an embodiment of the present invention.

FIG. 2 is a timing chart illustrating an opening / closing timing of the shutter mechanism 5.

FIG. 3 is a configuration diagram of a shutter according to another embodiment of the present invention.

FIG. 4 is a configuration diagram of a shutter according to still another embodiment of the present invention.

FIG. 5 is a block diagram showing the basic overall configuration of a tandem electrostatic accelerator.

FIG. 6 is a sectional view showing the configuration of a conventional charge conversion cell.

[Explanation of symbols]

 1 ion source 2 charge conversion cell 21 cell body 21a ion inlet 21b ion outlet 22 heater 3 acceleration tube 4 target 5 shutter mechanism 5a, 5b shutter 51 connecting member 52 shutter driving cylinder 6 crystal oscillator 7 insulator 8 conducting wire 9 ammeter

Claims (1)

(57) [Claims] 1. Positive ions extracted from an ion source are
In a device that converts a negative ion by passing through a charge conversion cell that generates a metal vapor inside by heating a metal material, and accelerates the negative ion by an electrostatic acceleration unit to irradiate a target, Ion beam is used for the ion inlet and outlet of the charge conversion cell
An electrostatic accelerator provided with a shutter mechanism that opens only when