JP2010153096A - Ion gun and ion beam extraction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make uniform an ion beam current density in an ion gun lined up with a plurality of ion beam extracting holes. <P>SOLUTION: The ion gun includes: a plasma generating means composed of a cathode and an anode; and a grid for extracting ion beams from plasma, wherein the grid has a plurality of or a series of ion beam extracting holes. In this case, with a central section of a plurality of or a series of ion beam extracting holes as an origin, the longitudinal direction as an x axis direction, and the ion beam emitting direction as a z axis positive direction, the ion gun further includes: a first magnet that is arranged in the periphery of a plurality of or a series of the ion beam extracting holes and imparting a magnetic field in a z-axis positive direction of a plurality of or a series of ion beam extracting holes; and a second magnet that is arranged at an end section of a plurality or a series of ion beam extracting holes and imparting a magnetic field in the direction of the x-axis origin in the vicinity of the end section. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ion gun, and more particularly, to an ion beam extraction method in an ion gun in which a plurality of ion beam extraction holes are aligned.

An ion gun is generally used for a frequency adjustment device of a piezoelectric element. As a principle, an ion gun generates plasma inside the ion gun, and accelerates by extracting ions from the plasma while applying a magnetic field in the beam emission direction to the plasma. Is formed.
Patent Document 1 discloses an ion gun in which a plurality of ion beam extraction holes are arranged to emit an ion beam having a corresponding current density peak.

  In FIG. 1, the ion gun includes a filament (cathode) 10 installed between a pair of filament electrodes, an annular anode 20 having a longitudinal direction parallel to the filament 10, a grid 30 having a plurality of ion beam extraction holes 31, and the filament 10. And a main body 40 that seals the anode 20 inside and exposes a plurality of ion beam extraction holes 31. The cathode 10 and the anode 20 constitute plasma generation means and are connected to respective power sources (not shown). The main body 40 includes a gas inlet 41 for introducing a discharge gas.

11A and 11B are a side view and a top view around the anode 20 in the prior art.
As shown in FIG. 11B, the grid 30 has a plurality of ion beam extraction holes 31 arranged in the x-axis direction in a region defined by the periphery of the anode 20.

  Regarding the operation of the ion gun, first, a discharge gas such as argon is introduced into the main body 40 from the gas inlet 41. A negative voltage is applied to the filament 10 and a positive voltage is applied to the anode 20, and discharge is performed by the potential difference to generate plasma. When a voltage is applied to the grid 30 from a power source (not shown), ions are extracted from the plasma by the plurality of ion beam extraction holes 31 and accelerated to form an ion beam.

  As shown in FIGS. 11A and 11B, around the ion beam extraction hole 31, a plurality of first magnets with the S pole oriented in the z-axis positive direction (ion beam emission direction) and the N pole oriented in the z-axis negative direction 50 is arranged. The first magnet 50 forms a magnetic field in the z-axis positive direction in the ion beam extraction hole 31 to increase the plasma density.

FIG. 11C shows the magnetic field distribution of the ion gun described above.
FIG. 11D shows the current density of the ion beam at a position 25 mm from the grid surface, that is, a position where the processing substrate is arranged in this configuration. As shown in the figure, each peak corresponds to the ion beam extraction hole 31, and the current density peak on the end side is greatly reduced with respect to the current density peak near the center. As described above, the configuration of FIGS. 11A and 11B has a problem that the ion beam current density becomes non-uniform.

Details of this problem will be described below.
In order to obtain a uniform ion current density distribution on the processing substrate side, the plasma density in the vicinity of the extraction hole contributing to the emission of the ion beam needs to be uniform. In the case of the ion gun having the configuration as shown in FIG. 1, a convex temperature distribution (that is, the temperature is low from the center toward the outside) is formed by the heat radiation of the filament end, and electrons necessary for plasma generation and sustaining are generated. Insufficient toward the end of the anode.
As a result, as shown by curve a in FIG. 12, the plasma density at the anode center is relatively high and tends to decrease as it approaches the end. This tendency is the same even when the region is limited to the region of the extraction hole that contributes to the emission of the ion beam, and the current density at the end becomes lower than the current density peak near the center as shown in FIG. 11D. End up.

With respect to the above problems, Patent Document 2 discloses a configuration in which a plurality of filaments are arranged in the longitudinal direction and each filament is individually controlled by each power source. In this configuration, more power is consumed by the filament on the end side of the plurality of filaments, and the current density of the ion beam on the corresponding end side is increased.
JP 2006-100205 A JP 2007-31118 A

However, according to the configuration as in Patent Document 2, in order to increase the current density at the end of the ion beam and make the current density uniform, it is necessary to significantly increase the power supplied to the filament on the end side. Power consumption increases and is not preferable. In addition, it is necessary to install a plurality of power supplies according to a plurality of filaments, which causes a problem that the configuration of the ion gun becomes complicated and large, and the cost becomes high.
Therefore, it is desirable to solve the problem that the current density of the ion beam on the end side becomes small in an ion gun in which a plurality of ion beam extraction holes are aligned without changing the power supply mode to the filament.

  According to a first aspect of the present invention, in an ion gun comprising a plasma generating means comprising a cathode and an anode and a grid for extracting an ion beam from the plasma, the grid has a plurality or a series of ion beam extraction holes in the longitudinal direction. A plurality of or a series of ions are arranged around a plurality of or a series of ion beam extraction holes, with the center of the series of ion beam extraction holes as the origin, the longitudinal direction as the x-axis direction, and the ion beam emission direction as the z-axis positive direction. A first magnet that applies a magnetic field in the z-axis positive direction to the beam extraction hole, and a second magnet that is disposed at an end of the plurality or series of ion beam extraction holes and applies a magnetic field in the x-axis origin direction near the end. Furthermore, it is an ion gun.

  Here, with the axis perpendicular to the x-axis and the z-axis as the y-axis, at least four second magnets are arranged at the x-axis symmetric position and the y-axis symmetric position surrounding the plurality or series of ion beam extraction holes, Each of the second magnets has a configuration in which the S pole is disposed in the x-axis origin direction and the N pole is directed in the opposite direction.

  A second aspect of the present invention is an ion beam extraction method in an ion gun in which a plurality of ion beam extraction holes are aligned, and (A) a step of generating plasma inside the ion gun, and (B) a first magnet. To apply a magnetic field in the ion beam extraction direction (z-axis positive direction) of the plurality of ion beam extraction holes, and to the center portion direction (x-axis origin direction) from the ends of the plurality of ion beam extraction holes by the second magnet. The ion beam extraction method includes a step of applying and applying a voltage to a grid in which the plurality of ion beam extraction holes are formed to extract and accelerate ions.

  In the ion gun in which a plurality of ion beam extraction holes are aligned, the problem that the ion beam current density on the end side becomes small has been solved by improving the distribution of magnetic lines of force, so that it is simple and inexpensive without increasing power consumption. The method was able to effectively achieve uniform ion beam current density.

Example 1.
2A and 2B are views around the anode 20 in the ion gun of the first embodiment. The configurations of the filament (cathode) 10, the grid 30, the main body 40, and the first magnet 50 in the ion gun of the present invention are the same as those shown in FIG. 1, FIG.

  As shown in FIGS. 2A and 2B, the ion gun of this embodiment further includes four second magnets 60 symmetrically with respect to the x axis and the y axis. Each of the second magnets 60 is arranged with the S pole in the x-axis origin direction and the N pole in the opposite direction, and in the x-axis origin direction near the end of the ion beam extraction hole 31 (end of the anode 20). Give the magnetic field. For convenience of explanation, four second magnets 60 are provided, but may be eight, twelve, or the like.

  FIG. 2C shows the magnetic field distribution of the ion gun described above. As shown in the figure, the magnetic field lines near the ends of the plurality of ion beam extraction holes 31 (x-axis ± 30 to 45 mm) are generated in the center of the ion beam extraction hole 31 (in the x-axis origin direction) by the action of the second magnet 60. This inwardly directed magnetic field can contribute to the extraction of the ion beam by increasing the plasma density near the edges.

  By the way, it is well known that electrons in plasma in a uniform magnetic field spirally move along the lines of magnetic force as shown in FIG. When the ion current density distribution is made uniform, the plasma density distribution should be uniform only in the region of the extraction hole as shown by the line b in FIG. In this embodiment, by arranging the second magnet 60 as shown in FIGS. 2A and 2B, the magnetic field lines at the anode end are directed inward as shown in FIG. By being directed to the region of the extraction hole, the plasma density in the region of the extraction hole is adjusted.

  FIG. 2D shows the current density of the ion beam at a position 25 mm from the grid surface in the above configuration, that is, a position where the processing substrate is arranged. Also in FIG. 2D, the current density peak corresponds to each ion beam extraction hole 31. As can be seen from comparison with FIG. 11D, the current density peak on the ion beam end side becomes substantially the same level as the current density peak in the center, and the ion beam current density can be made substantially uniform in the x-axis direction. It was.

In the first embodiment, the most preferable arrangement of the second magnet 60 has been shown. However, the second magnet 60 generates an x-axis origin in the plasma near the end of the ion beam extraction hole 31 (end of the anode 20). Other arrangements may be used as long as a magnetic field in the direction can be applied.
For example, as shown in FIGS. 4A and 4B, the second magnet 60 may be disposed outside the grid 30. Even in this configuration, the same actions and effects can be achieved.

Example 2
5A and 5B show a second embodiment of the present invention. In the first embodiment, a permanent magnet is used as the second magnet 60, but in this embodiment, an electromagnet is used. 5A and 5B, the second magnet 60 is one in which a coil (shaded portion) is wound around a core of magnetic material, and magnetic force is generated by energizing the coil from a power source (not shown). In this embodiment, the second magnet 60 has an S pole on the center side and an N pole on the other side.
Even in this configuration, the same effect as in the first embodiment can be obtained.

  Here, the anode 20 will be supplemented. 6A to 6D show variations of the shape of the anode (all are top views). FIG. 6 (a) is the annular type shown in FIG. 2B, but is also divided in the longitudinal direction as shown in (b), a U-shaped one as shown in (c), (d) And the like divided in the width direction. Further, the shape is not limited to a square and may be an ellipse. The main body 40 itself may be an anode without providing the anode 20.

  Further, a supplementary explanation will be given for the plurality of ion beam extraction holes 31. 7A to 7E show variations of the plurality of ion beam extraction holes 31. FIG. Thus, in addition to what is shown in FIG. 2B (ie, FIG. 7D), the ion beam 31 can take various forms. The “plurality of ion beam extraction holes” referred to in the present specification and claims includes all of the embodiments exemplified above and similar embodiments thereof.

Reference Example 1
8A and 8B show the second magnet 60 with the north pole in the x-axis origin direction and the south pole in the opposite direction (the polarity is opposite to that in FIGS. 2A and 2B). As a result, a magnetic field in the x-axis outer direction is applied near the end of the ion beam extraction hole 31.
As shown in FIG. 8C, the magnetic field in the vicinity of the ends of the plurality of ion beam extraction holes 31 is directed to the outside of the ion beam extraction holes 31 by the second magnet 60.
As shown in FIG. 8D, the ion beam current density not only increases its non-uniformity, but also reduces the current density as a whole.

Reference Example 2
FIGS. 9A and 9B show the second magnet 60 with the south pole in the z-axis positive direction and the north pole in the opposite direction. As a result, as shown in FIG. 9C, a magnetic field in the z-axis positive direction is applied near the end of the ion beam extraction hole 31. The concept of this configuration (that is, the concept of changing the magnitude, not the direction of the magnetic field vector) is similar to that of increasing the electric power of the end side filament in Patent Document 2.
As shown in FIG. 9D, the ion beam current density is generally higher than that of FIG. 11D, but the non-uniformity is hardly eliminated.

  From the reference examples 1 and 2, it can be seen that the arrangement of the second magnet is preferably the one shown in each example. In particular, it can be seen that the method of improving the magnetic field direction of the present invention has a higher effect of eliminating the nonuniformity of the ion beam current distribution than the method of magnetic field enhancement as in Patent Document 2.

Example 3 FIG.
In the first and second embodiments, the second magnet 60 is fixed. In this embodiment, the installation angle is variable based on the first and second reference examples.
The installation angle with respect to the z-axis direction of each of the second magnets 60 can be made variable, and the magnetic field in the x-axis origin direction can be adjusted. Specifically, when the magnetic field in the x-axis origin direction when the second magnet 60 is installed at 90 ° with respect to the z-axis direction is too strong, as shown in FIG. What is necessary is just to make the angle with respect to an axial direction smaller than 90 degrees.

As a result, the peak of the ion beam current density, particularly on the end side, can be adjusted, and the current density can be made more strictly uniform.
In addition, the installation angle of the four second magnets 60 may be interlocked, or a pair at an x-axis symmetric position, a y-axis symmetric position, or a diagonal position may be interlocked. The four installation angles may be individually adjustable.

Here, if the installation angle of the second magnet 60 can be adjusted from the outside during the ion beam emission, the adjustment during the beam irradiation is possible, which is more preferable.
FIG. 10B is a flowchart of the ion beam extraction method in this case.
In step S100, a discharge gas such as argon is introduced from the gas inlet 41, a negative voltage is applied to the filament (cathode) 10, and a positive voltage is applied to the anode 20, and plasma is generated by the discharge during this time.
In step S110, a voltage is applied to the grid 30 and ions are extracted from the plasma in a state where a magnetic field is applied in the positive z-axis direction by the first magnet 50 and in the x-axis origin direction by the second magnet 60. Accelerate.
If the peak at the end of the ion beam current density is higher than the central peak at this time, the installation angle of the second magnet 60 is adjusted in step S120, and the distribution of the current density peak is adjusted. When the second magnet 60 is an electromagnet, the current supplied to the coil may be adjusted so that a desired current density peak distribution is obtained.
In addition, each figure does not necessarily follow a dimension.

It is a figure explaining the ion gun of this invention and a prior art example. It is a figure which shows the 1st Example of this invention. It is a figure which shows the 1st Example of this invention. It is a figure explaining the 1st Example of this invention. It is a figure explaining the 1st Example of this invention. It is a figure explaining the principle of this invention. It is a figure which supplements the 1st example of the present invention. It is a figure which supplements the 1st example of the present invention. It is a figure which shows the 2nd Example of this invention. It is a figure which shows the 2nd Example of this invention. It is a figure which supplements this invention. It is a figure which supplements this invention. It is a figure which shows the reference example 1. FIG. It is a figure which shows the reference example 1. FIG. It is a figure which shows the reference example 1. FIG. It is a figure explaining the reference example 1. FIG. It is a figure which shows the reference example 2. FIG. It is a figure which shows the reference example 2. FIG. It is a figure which shows the reference example 2. FIG. It is a figure explaining the reference example 2. FIG. It is a figure which shows the 3rd Example of this invention. It is a flowchart explaining the 3rd Example of the present invention. It is a figure which shows a prior art example. It is a figure which shows a prior art example. It is a figure explaining a prior art example. It is a figure explaining a prior art example. It is a figure explaining a general ion gun.

Explanation of symbols

10. Filament (cathode)
20. Anode 30. Grid 31. Ion beam extraction hole 40. Main body 41. Gas inlet 50. First magnet 60. Second magnet

Claims (3)

In an ion gun comprising a plasma generating means comprising a cathode and an anode and a grid for extracting an ion beam from the plasma,
The grid has a plurality or a series of ion beam extraction holes in the longitudinal direction;
With the central portion of the plurality or series of ion beam extraction holes as the origin, the longitudinal direction is the x-axis direction, and the ion beam emission direction is the z-axis positive direction,
A first magnet disposed around the plurality of or a series of ion beam extraction holes and applying a positive magnetic field to the plurality or the series of ion beam extraction holes; and an end of the plurality or the series of ion beam extraction holes An ion gun further comprising a second magnet that is disposed in a portion and that provides a magnetic field in the x-axis origin direction near the end. The ion gun according to claim 1, wherein an axis perpendicular to the x-axis and the z-axis is a y-axis.
At least four of the second magnets are disposed at an x-axis symmetric position and a y-axis symmetric position surrounding the plurality or series of ion beam extraction holes, and each of the second magnets has an S pole in the x-axis origin direction. And an ion gun placed with the north pole facing in the opposite direction. An ion beam extraction method in an ion gun in which a plurality of ion beam extraction holes are aligned,
(A) generating plasma inside the ion gun; and (B) applying a magnetic field to the ion beam extraction direction (z-axis positive direction) of the plurality of ion beam extraction holes by the first magnet, and a second magnet. By applying a magnetic field from the ends of the plurality of ion beam extraction holes in the central direction (x-axis origin direction) and applying a voltage to the grid in which the plurality of ion beam extraction holes are formed, ions are extracted and accelerated. An ion beam extraction method comprising steps.

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