JP5720021B2 - Ion gun - Google Patents

Description

  The present invention relates to an ion gun, and more particularly to an ion beam extraction structure in an ion gun.

  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.

  FIG. 1A shows a general ion gun (for example, Patent Document 1). The ion gun includes a cathode 10 composed of a pair of filaments 11 and 12, an annular anode 20 having a longitudinal direction parallel to the cathode 10, a grid 30 having ion beam extraction holes 31, and a plurality of cathodes 10 and anodes 20 sealed inside. The main body 40 exposes the ion beam extraction hole 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 and a cooling mechanism 42 for introducing a discharge gas.

  7A and 7B are a side view and a top view, respectively, around the anode 20 in the prior art. As shown in FIG. 7B, the grid 30 has ion beam extraction holes 31 arranged in the longitudinal direction (x-axis direction) in a region defined by the periphery of the anode 20. The ion beam extraction hole 31 includes a plurality of holes.

  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 filaments 11 and 12, 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, ions are extracted from the plasma by the ion beam extraction hole 31 and accelerated to form an ion beam.

  As shown in FIGS. 7A and 7B, around the ion beam extraction hole 31, a plurality of magnets 55 are arranged with the south pole facing the ion beam emission direction (z-axis positive direction) and the north pole facing the opposite. Yes. The magnet 55 forms a positive magnetic field in the z-axis direction in the ion beam extraction hole 31 to increase the plasma density.

JP 2007-31118 A

  FIG. 8 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. The horizontal axis of FIG. 8 represents a position corresponding to the x-axis direction of FIGS. 7A and 7B, and the point of position 0 mm corresponds to the position of x = 0 in FIGS. 7A and 7B. Here, as shown in FIG. 8, there is a problem that the ion current density increases corresponding to the pair of filaments 11 and 12 and decreases at a separation portion between the filaments, and the distribution is not uniform.

  Accordingly, an object of the present invention is to provide a configuration in which the current density of an ion beam is made uniform in an ion gun having a plurality of filaments.

An ion gun for solving the above problem comprises a plasma generating means comprising a cathode and an anode, and a grid for extracting an ion beam from the plasma, having a longitudinal direction and a width direction, and a plurality of filaments in which the cathode extends in the longitudinal direction. The grid has an ion beam extraction hole extending in the longitudinal direction. The ion gun is further a plurality of main magnets arranged around the ion beam extraction hole, each of which is arranged with the south pole facing the ion beam emission direction and the north pole facing the opposite direction. , At least four first auxiliary magnets arranged symmetrically with respect to the longitudinal direction and the width direction at the longitudinal end portion of the ion beam extraction hole , each of which has the south pole inward in the longitudinal direction and the north pole in reverse First auxiliary magnets (60) arranged in the direction and second auxiliary magnets arranged symmetrically in the width direction at positions corresponding to the separated portions between the plurality of filaments, each having N poles A second auxiliary magnet (65) is provided in the ion beam emission direction with the south pole facing in the opposite direction.

In one embodiment of the present invention, in the ion gun, the plurality of filaments are composed of a pair of filaments.
Here, it is good also as a structure further equipped with the power supply which controls separately the electric current which supplies with electricity to a some filament.
Further, the first auxiliary magnet and the second auxiliary magnet may be arranged outside the plurality of main magnets.

It is a figure which shows the basic composition of an ion gun. It is a figure which shows the example of an anode. It is a figure which shows the example of an ion extraction hole. It is a side view near the anode of the ion gun by the Example of this invention. It is a top view near the anode of the ion gun according to the embodiment of the present invention. It is sectional drawing of the ion gun by the Example of this invention. It is a side view near the magnet of the ion gun by the Example of this invention. It is a top view near the magnet of the ion gun by the Example of this invention. It is a figure which shows the ion beam current density by the Example of this invention. It is a figure which shows the ion beam current density of the ion gun of a reference example. It is a figure which shows the ion beam current density of the ion gun of a reference example. It is a figure which shows the ion beam current density of the ion gun of a reference example. It is a figure which shows the magnet arrangement | positioning of a reference example. It is a figure which shows the magnet arrangement | positioning of a reference example. It is a figure which shows the magnet arrangement | positioning of a reference example. It is a side view near the anode of the conventional ion gun. It is a top view near the anode of the conventional ion gun. It is a figure which shows the ion beam current density of the ion gun of a prior art example.

The present invention improves ion beam current density non-uniformity in an ion gun having a plurality of filaments as cathodes by adjusting the magnet arrangement around the anode.
The basic configuration of the ion gun according to the embodiment of the present invention is the same as the configuration of FIG. 1A described above. In other words, the ion gun includes a plasma generating means including a cathode 10 and an anode 20 and a grid 30 for extracting an ion beam from the plasma. The cathode 10 is composed of a pair of filaments 11 and 12 extending in the longitudinal direction, and the grid 30 has an ion beam extraction hole 31 extending in the longitudinal direction. The grid 30 has a two-layer structure, and includes a shielding grid and an acceleration grid. The shielding grid is at the same potential as the ion gun body and is disposed on the ion extraction surface of the ion gun body. The acceleration grid is arranged substantially in parallel with a predetermined distance from the shielding grid, and an acceleration potential is applied. As a result, a voltage gradient is formed and ions in the plasma are extracted. A deceleration grid with a ground potential may be arranged outside the acceleration grid to form a three-layered grid structure. The deceleration grid may be disposed substantially parallel to the acceleration grid at a predetermined distance.

As shown in FIG. 1B, the anode 20 includes (a) a frame shape, (b) a frame shape with a separated center, (c) a frame shape with one end open, (d) two plate shapes, and the like. It can take the form of
As shown in FIG. 1C, the ion beam extraction holes 31 are (a) a plurality of compound eye holes arranged separately in a top view, and (b) individual compound eye holes while a plurality of compound eye holes are connected and arranged. (C) a plurality of compound eye holes connected to each other and the shape of each compound eye hole cannot be recognized, (d) a plurality of single eye holes arranged separately, and (e) a longitudinal direction. It can take the form of a single hole or the like extending in the direction.
There are various variations in the form of the anode and the ion beam extraction hole, and the anode 20 and the ion beam extraction hole 31 of the present invention are not limited to those shown in FIGS. 1B and 1C.

  The present invention is different from the conventional example in the configuration of the magnet arrangement around the anode 20. 2A to 2C are a side view, a top view, and a cross-sectional view, respectively, around the anode 20 in the present invention. For convenience of explanation, the center of the ion beam extraction hole 31 is the origin, the longitudinal direction is the x-axis direction, the width direction is the y-axis direction, and the ion beam emission direction is the z-axis positive direction.

As shown in FIGS. 2A to 2C, a plurality of main magnets 50 are arranged around the ion beam extraction hole 31, and each of the main magnets 50 has the south pole in the z-axis positive direction and the north pole in the opposite direction. Arranged. A plurality of main magnets 50 apply a z-axis positive magnetic field to the ion beam extraction hole 31. The configuration of the main magnet 50 may be the same as the magnet 55 of the conventional example (FIGS. 7A and 7B).
In the embodiment of the present invention, in addition to the main magnet 50 described above, a first auxiliary magnet 60 and a second auxiliary magnet 65 are provided.

  The auxiliary magnet 60 is disposed symmetrically with respect to the x axis and the y axis at the ends of the plurality of main magnets 50. The auxiliary magnet 60 is preferably arranged outside the plurality of main magnets 50, but may be arranged on the same straight line as the main magnet 50 or inside the main magnet 50. Each of the auxiliary magnets 60 is arranged with the south pole facing the x-axis origin direction and the north pole facing the opposite direction. A magnetic field in the x-axis origin direction is applied to the end of the ion beam extraction hole 31 by the four auxiliary magnets 60. In addition, although the four auxiliary magnets 60 are used in a present Example, the number can be changed according to the size of the auxiliary magnet 60 or the strength of magnetic force. For example, in FIG. 2A, a plurality of auxiliary magnets 60 at each position may be provided in the z-axis direction.

  The auxiliary magnet 65 is disposed symmetrically with respect to the x axis at a position corresponding to a separation portion between the pair of filaments 11 and 12. The auxiliary magnet 65 is preferably arranged outside the plurality of main magnets 50, but may be arranged on the same straight line as the main magnet 50 or inside the main magnet 50. Each of the auxiliary magnets 65 is disposed with the north pole in the z-axis positive direction and the south pole in the opposite direction. The two auxiliary magnets 65 apply a negative z-axis magnetic field to the center of the ion beam extraction hole 31 (a position corresponding to the separated portion of the filament 11 and the filament 12).

  3A and 3B are detailed explanatory views of the main magnet 50, the auxiliary magnet 60, and the auxiliary magnet 65. FIG. A flat magnetic body 70 is attached to each of the S pole face and the N pole face of the main magnet 50. The magnetic body 70 is disposed in parallel to the xy plane. In the embodiment, a pair of magnetic plates and a plurality of main magnets arranged therebetween are used as one unit, and two units are prepared, and each unit is fixed to the ion gun body along the X axis of the outer periphery of the anode 20. A magnetic body 71 is attached to the auxiliary magnet 60 only on the south pole surface. The magnetic body 71 is formed in an L shape, one end is fixed to the auxiliary magnet and the other end is fixed to the mounting base 73. The mounting base 73 is made of a nonmagnetic material and is fixed to the ion gun body. One end of an L-shaped magnetic body 72 is attached to both sides of the auxiliary magnet 65, and the other end of the magnetic body 72 is fixed to a mounting base 73. The magnet mounting surfaces of the L-shaped magnetic bodies 71 and 72 are disposed in parallel to the yz plane, and the fixed surface to the mounting base is disposed in parallel to the xy plane. The magnetic field is optimized by the main magnet 50, the auxiliary magnet 60, the auxiliary magnet 65, the magnetic body 70, the magnetic body 71, and the magnetic body 72, and a desired ion current density distribution is obtained. The magnetic bodies 70 to 72 are made of a magnetic material such as iron.

  FIG. 4 shows the distribution of the ion beam current density (the ion beam current density at a position 25 mm from the grid surface, that is, the position where the processing substrate is disposed) in the present embodiment. Also in FIG. 4, the horizontal axis represents a position corresponding to the x-axis direction of FIGS. 2A and 2B, and the point of position 0 mm corresponds to the position of x = 0 in FIGS. 2A and 2B.

For reference, when only the auxiliary magnet 60 is provided in FIGS. 5A, 5B, and 5C (FIG. 6A), the auxiliary magnet 60 and the auxiliary magnet 65 are provided, but the polarity of the auxiliary magnet 65 is as shown in FIGS. 2A to 2C. FIG. 6B shows the ion beam current density in the case reverse to that shown in FIG. 6 (FIG. 6B) and in the case where the auxiliary magnet 65 is arranged parallel to the longitudinal direction (FIG. 6C). The measurement conditions are beam voltage: 600 V, discharge current: 800 mA, argon gas flow rate (5.0 sccm), discharge pressure: 2.8 × 10 ⁻² Pa.

  As shown in FIG. 4, a substantially uniform ion current density was obtained by the configuration of the example. When the difference from the average value at each position is expressed as a percentage in the range of ± 50 mm from the center of the ion extraction hole 31 (ie, y = 0, x = ± 50), the conventional example Although it was ± 6.9% in (FIG. 8), it was ± 2.4% in this example (FIG. 4), and it can be seen that the uniformity was greatly improved by this example. Further, in FIGS. 5A, 5B, and 5C of the reference examples, they were ± 7.1%, ± 6.9%, and ± 7.7%, respectively.

  2A to 2C, in the ion gun having the pair of filaments 11 and 12, a uniform ion beam current density can be obtained by the interaction of the main magnet 50 and the auxiliary magnets 60 and 65. Can do.

  In addition, the ion gun is provided with a power source (not shown) that controls the current supplied to the pair of filaments 11 and 12. Here, the power source may be capable of individually controlling the current for each filament. By individually controlling the current of each filament, it is possible to compensate for variations in output between filaments and variations in magnetic force between magnets, thereby obtaining a more uniform ion beam current density.

  In the above embodiment, an ion gun having a pair of filaments 11 and 12 arranged extending in the longitudinal direction has been described. However, those skilled in the art will understand that the principle of the present invention extends in the longitudinal direction. It should be understood that the present invention can also be applied to an ion gun having three or more filaments arranged. For example, in the case where n filaments are arranged extending apart from each other, at least four auxiliary magnets 60 are arranged at the four corners of the ion extraction hole 31 in the same manner as in the above embodiment, and the N pole is arranged on the z axis. A total of (n−1) × 2 auxiliary magnets 65 directed in the positive direction may be arranged symmetrically with respect to the x axis at a position corresponding to a separation portion between the filaments.

10. Cathodes 11 and 12. Filament 20. Anode 30. Grid 31. Ion beam extraction hole 40. Main body 41. Gas inlet 50. Main magnets 60, 65. Auxiliary magnet

Claims (4)

An ion gun having a longitudinal direction and a width direction, comprising a plasma generating means comprising a cathode and an anode and a grid for extracting an ion beam from the plasma,
The cathode comprises a plurality of filaments extending in the longitudinal direction;
The grid has ion beam extraction holes extending in the longitudinal direction;
further,
A plurality of main magnets arranged around the ion beam extraction hole, each of which is arranged with the south pole facing the ion beam exit direction and the north pole facing the opposite direction;
At least four first auxiliary magnets arranged symmetrically with respect to the longitudinal direction and the width direction at the longitudinal end portion of the ion beam extraction hole , each having an S pole inwardly in the longitudinal direction and an N pole First auxiliary magnets arranged in the opposite direction, and second auxiliary magnets arranged symmetrically in the width direction at positions corresponding to the separation portions between the plurality of filaments, each of which is N An ion gun comprising a second auxiliary magnet arranged with the poles directed in the direction of ion beam emission and the S poles directed in the opposite direction.   2. The ion gun according to claim 1, wherein the plurality of filaments comprise a pair of filaments.   2. The ion gun according to claim 1, wherein the first auxiliary magnet and the second auxiliary magnet are arranged outside the plurality of main magnets.   4. The ion gun according to claim 1, further comprising a power source for individually controlling currents to be supplied to the plurality of filaments.

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