JPH06223760A - Ion extracting electrode - Google Patents

Abstract

PURPOSE:To eliminate the need for replacing the whole of an assembly when the assembly is locally damaged or failed by devising a single unit block or a plurality of unit blocks to be taken out of a support frame. CONSTITUTION:A plurality of unit blocks 1 in a square shape are combined into a support frame 2 in a rectangular shape so as to be fitted in an electrode frame 3 the outer circumference of which is circular while being furnished with a rectangular opening at its center. It is the vicinity of the hole of the unit block 1 that an electrode plate is damaged by discharge. Damages are given to only one or two unit blocks. Therefore, when the electrode is damaged, damaged unit blocks can be replaced with new ones so as to be integrated with the electrode plate. A repair about the electrode plate has been done as mentioned above, and there is no need for replacing the whole of the electrode plate cost efficiency is thereby extremely advantageous.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous extraction electrode used for an ion source or the like. The ion source excites gas or metal vapor by electric discharge to generate plasma, which extracts ions by the action of an electric field. The ion source chamber is, of course, in a vacuum. For example, the source gas is excited by causing an arc discharge between the chamber and the chamber including an electrode such as a cathode filament. There are two or three extraction electrodes at the outlet of the chamber.

Electrodes have names. The first electrode is called a positive electrode, the second electrode is called a negative electrode, and the third electrode is called a ground electrode. Alternatively, the first sheet may be the plasma electrode and the second sheet may be the extraction electrode. Naming varies from person to person and is not consistent. The extraction electrode here is a generic term for these three or two electrodes, and does not refer to only the second electrode.

The electrode has a hole for extracting ions, which may be a single hole or a plurality of holes.
The shape of the electrode and the size distribution of the holes are appropriately determined by the target spread of the ion beam and the current. The porous electrode is an electrode for drawing out a beam having a plurality of holes perforated. It is therefore used for all the electrodes 1-3.

[0004]

2. Description of the Related Art FIG. 1 is a plan view of a conventional porous lead electrode. This is a plate of Mo, Ta, C, OFCu (oxygen-free copper) and has a circular shape. The electrode plate is not limited to a circular shape, but may be a quadrilateral or a polygon. 3 × 7 holes are drilled. The distribution and number of holes are arbitrary and can be changed freely. FIG. 2 is a sectional view of one hole.
This hole is narrow at the top and wide at the bottom. When the electrode plate is thick, the step portion is formed in the middle in this way to facilitate the extraction of the beam. If the plate is thin, a simple cylindrical hole is sufficient.

[0005]

In the case of an electrode plate for drawing out a large area ion beam, there are many circular holes.
To manufacture this, holes are made one by one in a plate of Mo, Ta, C, OFCu (oxygen-free copper). The electrode plate is provided at the outlet of the ion source chamber and a voltage is applied.
Ions are extracted as a beam due to the difference in voltage in the ion source chamber.

It is electrically conductive to use Mo or C as an electrode,
This is because it can withstand high heat and is relatively easy to process.
A high temperature plasma exists in the ion source chamber.
In addition, discharge is occurring. The electrode plate is naturally exposed to high temperature and electric discharge. Sometimes the discharge becomes abnormal. Then, one end of the arc discharge may be concentrated in a narrow area between the holes. In this case, the discharge concentrated portion of the electrode is in a high heat state.
Some melt. After this, even if the discharge becomes normal, once it melts, it remains as a protrusion. Further, if the local discharge is remarkable, this portion may be blown. When this happens, the hole is widened. Even if it does not, the shape of the hole will be distorted.

Since the electric field is likely to be concentrated when the above-mentioned protrusions are present, a local discharge is likely to occur here after the fact. When the shape of the hole is distorted, the shape of the ion beam becomes non-uniform. Therefore, the desired uniform large-area ion beam cannot be extracted.

For this reason, if the porous electrode is damaged by discharge or the like, it cannot be used as it is. It should be repaired, but since it is a hard metal and once melted, it becomes non-uniform, so it is not possible to polish or hit it to return the hole to its original shape . In other words, the electrode plate cannot usually be repaired. Since it cannot be repaired, it is necessary to replace it with a new one. Conventionally, when the electrode plate is damaged, the entire electrode plate is replaced.

However, the electrode plate is an expensive component. The material is also expensive and it takes time to drill a large number of holes. Mo and Ta are hard and it takes time just to make one hole. As mentioned above, since it is a hole with a step,
Working time becomes longer and cost is increased.

Although the electrode is expensive as described above, the whole must be replaced even if only one hole is deformed. This is a waste. This is because the whole must be replaced due to some failures.

In the case of local damage to the electrode plate, it is sufficient if the damage can be overcome by local replacement. The present invention is
Based on such a consideration, it is an object to provide an extraction electrode that does not need to be entirely replaced in the case of a local damage failure.

[0012]

The extraction electrode of the present invention comprises:
A part including several holes is disassembled into individual unit blocks, and the unit blocks are combined to form one electrode plate. When this causes local damage, only the unit block of that portion needs to be replaced. It is preferable to determine the shape of the unit block such that the flat surfaces can be completely covered by combining objects having the same shape. Of course, it is possible that some voids remain.

For example, one hole corresponds to a unit block. If an appropriate regular polygon centered on the center of the hole is used, this can be combined to completely cover the plane. Given that the interior angle of the polygon is a divisor of 360 °, this can be a triangle, a square or a regular hexagon.

Further, projections or recesses may be formed so that portions contacting adjacent unit blocks are suspended from each other. Due to the mutual suspension, the unit blocks can be combined into one electrode plate. Simple, square, triangle,
In the case of a hexagon, a frame is required to hold the whole and solidify it.

Further, a plurality of holes may be combined into one unit block. For example, four or two holes are put together to form a unit block. It is also possible to use an electrode plate in which the whole is covered with unit blocks. However, if a blind plate portion is also required, it may be used as a large separate member as an electrode frame. It suffices to fit the above-mentioned many unit blocks into this electrode frame.

[0016]

Operation: The extraction electrode is disassembled into a large number of unit blocks and these are combined to form one electrode plate. If a local discharge occurs, the holes melt,
Even if a protrusion is formed on the surface or the hole is deformed, it is not necessary to replace the entire electrode plate. You can remove only the unit block of the part where the failure occurred and replace it with a new one. This avoids the total replacement of expensive electrode plates. The cost required for maintenance and repair of the ion source can be reduced.

There is another effect. It means that the fabrication of the ion source electrode is standardized. Since the unit blocks are combined, an electrode plate having an arbitrary hole distribution can be manufactured by determining only the frame body that defines the overall shape. If the hole distribution is different as in the conventional case, it is necessary to drill holes in different parts each time.
However, since the present invention is a unit block and is combined with each other, such troublesomeness becomes unnecessary.

Further, the manufacturing process itself of the electrode plate is changed, which makes it more convenient. Since the unit block having holes is manufactured in advance, when making the electrode plate, the work of making holes in a hard metal such as Mo or Ta is omitted, and only the work of combining the unit blocks is required. This is very convenient for manufacturing the electrode plate.

[0019]

【Example】

[1. When using a square unit block] A porous electrode plate is constructed by combining square unit blocks. Figure 3
FIG. 3 is an exploded perspective view of an extraction electrode according to an embodiment of the present invention. This is one in which a large number of square unit blocks 1 are combined into a rectangular shape with a support frame 2, and this is fitted into an electrode frame 3 having a circular outer periphery and a rectangular opening. The shape of the opening 4 is equal to the shape of the support frame 2. In this example, a matrix having 3 rows and 7 columns is shown. FIG. 4 shows the unit block 1 through the support frame 2 and the electrode frame 3
The top view of the state fitted in FIG. The electrode plate has a desired shape as a whole.

The distribution of holes is the same as that shown in FIG. However, it is not integrated as shown in FIG. 1, but is a combination of many unit blocks 1, a support frame 2 and an electrode frame 3. The unit block 1, the support frame 2, and the electrode frame 3 are M
It is made of o, Ta, C, etc. Each unit block 1 is strongly pressed so as to be electrically connected.

FIG. 5 is a plan view of one square unit block 1. FIG. 6 is a sectional view of the same thing. The unit block 1 has a stepped hole 5 in the center. It has a small diameter at the top and a large diameter at the bottom. Since this is fitted with the adjacent unit block 1, the projections 6, 6 are provided on two of the four sides.
However, recesses 7, 7 are formed on the other two sides. Recess 7
By inserting the protrusions 6 into the square unit blocks, square unit blocks are combined.

In this way, by combining the projections having a height from the upper end to the middle and the recesses having a height from the middle to the lower, the unit block 1 can be inserted from the upper left end of the support frame 2. The unit blocks are sequentially assembled by mounting the protrusions on the concave portions of the unit blocks that have been previously inserted. The unit blocks on the edges are strongly pressed horizontally by the support frame. Further, the load is supported by the protrusion (not shown in the figure) on the lower side of the support frame. Since the unit blocks transmit the load by the projections and the recesses, if the unit blocks on the end sides are supported by the support frame, all the unit blocks can be collectively supported. However, the load bearing is asymmetric.

Alternatively, it is also possible to form protrusions and recesses at the intermediate height of the side faces and insert adjacent unit blocks from the side and combine them. In this way, the load sharing becomes symmetrical, and the load on the support frame becomes even. The combination work becomes a little difficult, but this is fine when the height of the protrusion is low. In any case, the unit blocks are strongly pressed together by the support frame 2 that hardens the four sides to put them together.

7 and 8 show examples of simpler unit blocks. Although it is a square unit block, it has no protrusions or recesses on its side surface. Has flat sides. If combined on the side, the unit block may fall out. In order to avoid this, the contact part of the unit block should be
You may make it support by something like a strip | belt of the insulator which fixed both ends to. It may be effective to make the side surfaces rough instead of smooth.

[2. When using a hexagonal unit block] FIG. 9 is an exploded perspective view showing an embodiment of an electrode plate in which regular hexagonal unit blocks are combined. FIG. 10 is a plan view of a state where the whole is combined. A large number of regular hexagonal unit blocks 1 are arranged in a line and are fixed by a larger regular hexagonal support frame 2. Since the unit blocks are regular hexagons, the arrangement of the unit blocks is not a matrix but a honeycomb. In other words, the distribution of holes is not a matrix but a staggered pattern. This is put into an electrode frame 3 having a circular outer periphery and having a regular hexagonal opening 4 inside to be integrated.

FIG. 11 is a plan view of a regular hexagonal unit block, and FIG. 12 is a sectional view. This unit block has a hole 5 in the center, a projection 6 on three of the six sides, and a recess 7 on the other three sides. The hole 5 is a stepped hole for pulling out the ion beam. The projections 6 and the recesses 7 are combined with each other so as to exert a load between adjacent unit blocks. This has the same function as that shown in FIG.

In addition to this, it is also possible to prevent vertical displacement by a recess and a protrusion provided at the intermediate height of the side surface. This is a little difficult to assemble, but it can completely prevent misalignment. 13 and 14 show simple regular hexagonal unit blocks. Although this is easy to assemble, it cannot prevent vertical displacement, so it is necessary to provide an insulating member below the contact portion to support the unit block.

In any case, when the electrode plate is damaged by the discharge, it is near the hole. Therefore, the damage only covers one or two unit blocks. If damaged, remove only that unit block and insert a new unit block in its place to integrate. This completes the repair of the electrode plate. There is no need to replace the whole. It is extremely cost effective.

Although the unit blocks described above are regular hexagonal and square unit blocks, regular triangular unit blocks are also possible. Geometrically, these figures can be repeated to cover the entire plane. Only three types of regular polygons are possible. However, if the shape is not limited to a regular polygon, that is, if it includes a curved line, there are other figures in which unit blocks of the same shape can be arranged to cover a plane. The present invention may use a unit block having such a shape.

[0030]

A high temperature plasma exists in the ion source chamber. Also, a high voltage is applied between the electrodes.
As a result, the discharge may become unstable, and local discharge may occur on the electrode plate, causing a part of the electrode plate to melt. The holes melt when melted, or the holes deform. In this case, conventionally, the entire electrode plate had to be replaced, but according to the present invention, only the damaged unit block needs to be replaced. Although the electrode plate is expensive, it is only necessary to replace a part of the unit blocks, so that the labor and cost for repair can be significantly reduced.

Further, since the unit blocks are combined to form one electrode plate, it becomes easy to form electrode plates having various shape distributions. This is because the unit block is standardized. For example, when the square unit blocks shown in FIG. 4 are combined, it is possible to easily create an arbitrary N × M matrix hole distribution. It is only necessary to make the support frame 2 according to this. A cooling channel may be provided between the matrices to prevent distortion of the electrode plate due to heat from the plasma. Its purpose is to prevent thermal distortion of the electrode plate.

Further, when it is desired to make the peripheral part of the electrode a blind plate,
As shown in FIGS. 3 and 9, a circular or rectangular electrode frame is required at the outermost circumference, but when holes may be arranged in the peripheral portion as well, the unit block 1 is attached to the support frame 2 It can be used as an electrode plate.

[Brief description of drawings]

FIG. 1 is a plan view of a porous electrode plate of an ion source chamber according to a conventional example.

FIG. 2 is a sectional view of a hole portion of the electrode plate of FIG.

FIG. 3 is an exploded perspective view of a porous electrode plate in which square unit blocks are repeatedly arranged according to an embodiment of the present invention.

FIG. 4 is a plan view of a combined state of porous electrode plates in which square unit blocks are repeatedly arranged according to an embodiment of the present invention.

FIG. 5 is a plan view of a square unit block having protrusions and recesses so as to be suspended from an adjacent block.

6 is a cross-sectional view of the square unit block shown in FIG. 5 having a protrusion and a recess so as to be suspended from an adjacent block.

FIG. 7 is a plan view of a square unit block having flat side surfaces.

8 is a cross-sectional view of the square unit block shown in FIG. 5 having flat sides.

FIG. 9 is an exploded perspective view of a porous electrode plate in which regular hexagonal unit blocks are repeatedly arranged in a honeycomb shape according to an embodiment of the present invention.

FIG. 10 is a plan view of a combination state of porous electrode plates in which regular hexagonal unit blocks according to the embodiment of the present invention are repeatedly arranged in a honeycomb shape.

FIG. 11 is a plan view of a regular hexagonal unit block having protrusions and recesses so as to be suspended from an adjacent block.

FIG. 12 is a cross-sectional view of the regular hexagonal unit block shown in FIG. 5, which has protrusions and recesses so as to be suspended from an adjacent block.

FIG. 13 is a plan view of a regular hexagonal unit block having flat side surfaces.

14 is a cross-sectional view of the regular hexagonal unit block shown in FIG. 5 having flat side surfaces.

[Explanation of symbols]

 1 unit block 2 support frame 3 electrode frame 4 opening 5 hole 6 protrusion 7 recess

Claims (3)

[Claims] 1. A raw material gas or a raw material metal vapor is introduced into a vacuum chamber, plasma is generated by discharge, and an ion beam is drawn from the plasma by applying an electric field between the raw material gas and the chamber. An ion extraction electrode provided, combining a plurality of unit blocks of the same shape including one or more holes in a plate shape,
An ion extraction electrode characterized by being integrally assembled by a support frame, and only one or a plurality of unit blocks can be removed from the support frame. 2. A source gas or a source metal vapor is introduced into a vacuum chamber, plasma is generated by discharge, and an ion beam is extracted from the plasma by applying an electric field between the source and the chamber. An ion extraction electrode provided, combining a plurality of unit blocks of the same shape including one or more holes in a plate shape,
It is integrated by a support frame, and the support frame is a blind plate and is fitted in an electrode frame that fits the outlet opening of the vacuum chamber so that only one or a plurality of unit blocks can be removed from the support frame. Ion extraction electrode characterized by 3. A raw material gas or a raw material metal vapor is introduced into a vacuum chamber, plasma is generated by discharge, and an ion beam is drawn from the plasma by applying an electric field between the raw material gas and the chamber. An ion extraction electrode to be provided, wherein a plurality of unit blocks of the same shape including one or more holes and having protrusions and recesses are combined in a plate shape by fitting the protrusions into the recesses,
An ion extraction electrode characterized by being integrally assembled by a support frame, and only one or a plurality of unit blocks can be removed from the support frame.