Cathode holding assembly and arc chamber support assembly including the same

Abstract

A cathode holding assembly attached to an arc chamber support of an ion implantation apparatus, comprising a cathode holding plate (3), an insulator block (4), and a shielding cap (5). The cathode holding plate (3) has an opening (3a) with a protruding outer rib (3d) and a protruding inner rib (3c) facing the shielding cap (5). The protruding portion (4a) of the insulator block (4) passes through the opening (3a) of the cathode holding plate (3). The insulator block (4) abuts against the protruding inner rib (3c) of the opening of the cathode holding plate at the edge of the insulator block (4) to accurately fit the insulator block into the opening (3a) of the cathode holding plate (3). The shielding cap (5) is disposed on the side of the insulator block opposite to the protruding portion (4a). A gap extends between the cathode holding plate (3) and the shielding cap (5), and further between the cathode holding plate (3) and the insulator block (4) and terminates there.

Description

Technical Field

[0001] The present invention relates to a cathode holding assembly (or cathode holding assembly) attached to an arc chamber support of an ion implantation apparatus. More specifically, the present invention relates to various components of the cathode holding assembly, the respective designs of these components, the arrangement between these components, and the arrangement of these components on the arc chamber support. Further, the present invention relates to an arc chamber support assembly having the cathode holding assembly, and an arc chamber assembly of an ion implantation apparatus provided with the arc chamber support assembly.

Background Art

[0002] When manufacturing semiconductor components, ion implantation apparatuses are widely used to modify various regions of a semiconductor wafer. At this time, positive ions or negative ions (dopants) are diffused or implanted into the wafer surface to form regions having various characteristics (for example, conductivity, etc.). These ion implantation apparatuses are provided with an arc chamber to generate a plasma containing various ion species to be implanted into the surface of the semiconductor wafer.

[0003] In one of the general configurations known for an arc chamber, a cathode assembly is arranged on the opposite side of a repeller (anti-cathode). During the operation of the arc chamber, for example, the cathode assembly is heated by a filament, the purpose of which is to emit electrons by thermionic emission during operation. By a relatively positive arc voltage on the wall of the arc chamber, electrons are accelerated into the arc chamber, and by an externally generated magnetic field, the electrons move spirally into the arc chamber. The emitted electrons are confined by an emitter and a repeller electrode that are typically negatively biased with respect to the wall of the arc chamber. Due to the combined effect of the emitter and the repeller electrode, electrons are concentrated toward the center of the arc chamber, so that the interaction with the dopant gas introduced into the arc chamber through a conduit is maximized, thereby obtaining a plasma having desired characteristics.

[0004] During operation, the arc chamber contains a large number of molecular species at very high temperatures. Under this harsh environment, the components (including the components of the cathode holding assembly) are exposed to conditions that may unduly limit their lifespan or effectiveness, which may result in either or both of the limitation of the effectiveness of the ion implantation device and the increase in its operating cost. For example, a plasma film tends to deposit on the components of the cathode holding assembly, such as the cathode holding plate, the insulator block, the shielding cap, etc. Due to this plasma coating on the insulator block, a short circuit may occur. For example, a short circuit may occur between the cathode holding plate and the filament / filament clamp, or between the cathode holding plate and the arc chamber, or between the filament clamp and the arc chamber, which may cause the shutdown of the ion source. Therefore, it is desirable to provide an extended and tortuous coating path so that the coating process (and correspondingly the occurrence of short circuits) of the electrically isolated or insulated components is prolonged. Furthermore, due to the size of the gaps or gaps provided in the cathode assembly, there are other failure modes such as gas leakage from the arc chamber. Furthermore, the assembly of the cathode assembly is not very simple, and a large number of fixtures (such as screws, alignment, and gap adjustment tools) are required.

[0005] In the prior art, the configurations of several cathode holding assemblies are known.

[0006] U.S. Patent No. 8,253,334 discloses an ion source assembly, as well as an arc chamber and an arc chamber support (see FIG. 10). The dimensions of the arc chamber support are defined to support the arc chamber, and it has a front end with a protrusion that is slidably fitted (or slide-fitted) within an insulator block (see FIG. 10B). FIG. 9 shows that an undercut is provided in the insulator block, which helps interrupt the accumulation of a conductive coating along a surface where the coating could cause a short circuit. In this configuration, the insulator block is attached to the arc chamber support by socket head cap screws, and the shield is attached to the graphite support plate by two socket head shoulder screws, where the two socket head shoulder screws cover, among other things, the insulator block and the graphite support plate. As a result, the upper end of the shield is shaped in a branched manner so as to lie over a major portion of the graphite support plate, holding a collar within a retaining portion (or retainer) and a retaining portion within the support plate. A sleeve is attached within the opening of the arc chamber and protrudes outward into the space of the graphite support plate, defining a tortuous gap so as to constrict the flow of plasma from the internal cavity of the arc chamber.

[0007] In the above-mentioned patent document, when a plasma path is provided, its length is limited. Further, in the assembly of the cathode holding assembly according to the prior art, many fixtures are required and its assembly is not easy. Also, as is well known, in the prior art, a plurality of tools and work steps are required to fix the components of the cathode holding assembly to each other and attach the cathode holding assembly to the arc chamber support.

[0008] Therefore, there is still room for improvement in the design of the cathode holding assembly in order to improve the life and effectiveness of the cathode, and thus the life and effectiveness of the arc chamber.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] The main object of the present invention is to provide a cathode holding assembly that achieves an improvement in the operating time of an ion implantation apparatus. By increasing the operating time, in particular, an effect of reducing the operating cost of the ion implantation apparatus can be obtained. Further, the present invention aims to provide a cathode holding assembly that is easy to assemble and requires a minimum of tools.

Means for Solving the Problems

[0011] In view of the above object and other objects, the present invention provides the following cathode holding assembly. That is, this cathode holding assembly is attached to the arc chamber support of an ion implantation apparatus and includes a cathode holding plate, an insulator block, and a shielding cap. The above cathode holding plate is formed to include a protruding outer rib facing the shielding cap and an opening having a protruding inner rib facing the shielding cap. The above insulator block is formed to include a protruding portion (or protrusion) configured to penetrate the opening of the cathode holding plate and be inserted into a corresponding recess of the arc chamber support. A through hole for fixing the insulator block to the arc chamber support is formed in the protruding portion of the insulator block. The above insulator block abuts at the edge of the insulator block against the protruding inner rib of the opening of the cathode holding plate to ensure that the insulator block fits accurately within the opening of the cathode holding plate. The above shielding cap is disposed on the side of the insulator block opposite to the protruding portion and defines a gap, which is defined to extend between the cathode holding plate and the shielding cap and further between the cathode holding plate and the insulator block and terminate there.

[0012] In other words, the object of the present invention can be solved by providing a cathode holding assembly attached to the arc chamber support of an ion implantation apparatus, the cathode holding assembly comprising a cathode holding plate, an insulator block, and a shielding cap. The cathode holding plate has a protruding outer rib facing the shielding cap and an opening provided with a protruding inner rib facing the shielding cap, and the protruding portion of the insulator block passes through the opening of the cathode holding plate and can be inserted into a corresponding recess of the arc chamber support. The protruding portion of the insulator block is provided with a hole extending so as to fix the insulator block to the arc chamber support. The insulator block is adjacent to the protruding inner rib of the opening of the cathode holding plate at the edge of the insulator block so that the insulator block fits exactly into the opening of the cathode holding plate, and the shielding cap is disposed on the side of the insulator block opposite to the protruding portion to define a gap, the gap being defined to extend between the cathode holding plate and the shielding cap and further between the cathode holding plate and the insulator block and terminate there. This is the same as described in the claims. This new cathode holding assembly is envisioned to be mounted on the arc chamber support of an ion implantation apparatus. However, the arc chamber support itself does not constitute a part of the invention described in independent claim 1. The arc chamber support only explains the interaction between the components of the cathode holding assembly. Further, an arc chamber support assembly of an ion implantation apparatus is provided, wherein the cathode holding assembly described in the claims is mounted so as to have the features described in the claims. Further, the arc chamber assembly of the ion implantation apparatus using the arc chamber support outlined below is detailed and described in the claims.

[0013] Further features and details of the present invention are described in the dependent claims, the detailed description and the drawings. Needless to say, the features and details described with respect to the cathode holding assembly according to the present invention are also applicable to the arc chamber support assembly and the arc chamber assembly according to the present invention, and vice versa. For this reason, in the disclosure of the individual aspects of the present invention, they can be referred to each other or can be referenced.

[0014] The inventors have found that in the cathode holding assembly described in the claims, even when only one insulator is used in the assembly, a longer and more tortuous coating path can be provided compared to the prior art. In the above-mentioned U.S. Patent No. 8,253,334, no gap is provided between the insulator and the shield, and only an undercut is available between the shield and the insulator. In addition, when using the cathode holding assembly described in the claims, the gas lost from the arc chamber during ion beam operation is reduced because the gap between the components of the cathode holding assembly / arc chamber support assembly described in the claims is smaller compared to the prior art. Due to the longer coating path and the smaller gap, it becomes possible to extend the life of the arc chamber during ion beam operation. Furthermore, the cathode holding assembly described in the claims can reduce the frequency of maintenance stops in the arc chamber.

[0015] One of the advantages of the present invention is that the components of the cathode holding assembly recited in the claims, namely, at least the cathode holding plate, the insulator block, and the shielding cap, self-align or self-align. Further, the cathode holding assembly and the arc chamber support self-align. This means that when these components are assembled together and when attached to the arc chamber support, these parts automatically assume the correct positions relative to each other. The exact distance between the impeller assembly and the cathode assembly also automatically aligns. As described above, in the prior art documents, many fixtures were required to assemble the ion source assembly to the arc chamber support. By using the cathode holding assembly or the arc chamber support assembly recited in the claims, when assembling the cathode holding assembly recited in the claims and attaching this assembly to the arc chamber support, the number of fixtures (and the number of tools required to adjust the fixtures) can be reduced.

[0016] Since the ion source assembly is exposed to a high-temperature and chemically rich environment, often a single component of the assembly, such as a screw, is rubbed against the mating assembly. In the present invention, the screw that holds the filament clamp against the cathode holding plate and holds the cathode holding plate against the arc chamber support is preferably attached to a fitting nut (see the locking member 7 in FIG. 4A and the locking member 11a in FIG. 3). In this configuration, even if rubbing occurs, the nut and the screw can be destructively disassembled without damaging the filament clamp, the cathode holding support, or the arc chamber support.

[0017] The cathode holding plate of the cathode holding assembly described in the claims is a monolithic plate, which has a circular opening at the upper end to receive a holding part or a retainer (for accommodating the filament), and has a rectangular (or oblong) opening at the lower end to allow the protrusion of the insulator block to pass through. The cathode holding plate has an inner rib protruding towards the shielding cap and an outer rib protruding in the area covered by the composition described in the claims (i.e., the lower end of the cathode holding plate arranged on the side opposite to the arc chamber support). The protruding inner rib is aligned or positioned with the opening of the cathode holding plate. The protruding outer rib overlaps with the flange of the insulator block. The cathode holding plate further has protruding ribs towards at least two arc chamber supports. Note that the arrangement of these ribs will be described later in relation to the arc chamber support assembly.

[0018] The cathode holding plate is made of graphite, a high melting point metal (or heat-resistant metal), or a high melting point metal-based alloy (or high melting point-based metal). The high melting point metal refers to the base metals (or parent materials) with high melting points in the fifth subgroup (vanadium, niobium, and tantalum) and the sixth subgroup (chromium, molybdenum, and tungsten). These melting points are higher than the melting point of platinum (1772 °C). The high melting point metal-based alloy can mean a combination of several pure high melting point metals (e.g., W and Mo), as well as a combination of their alloys (e.g., W-Re) and / or their compounds. In the context of the present invention, the high melting point metal-based alloy is understood to mean an alloy containing at least 80% by weight, preferably at least 90% by weight, of one or more high melting point metals. Among the high melting point metals, Mo and W, as well as Mo-based alloys and W-based alloys, are particularly suitable. In this regard, in Mo-based or W-based alloys, the proportion of Mo (or W) is 80% by weight or more, particularly 90% by weight or more or >95% by weight or more. Molybdenum has a very high melting point, low thermal expansion, and high thermal conductivity, so Mo or Mo-based alloys are particularly advantageous (this is also advantageous from the perspective of cost).

[0019] The insulator block has a protrusion at one end. This protrusion fits precisely within the opening of the cathode holding plate. When the cathode holding assembly is attached to the arc chamber support, the protrusion passes through the opening and reaches the corresponding recess in the arc chamber support. The protrusion of the insulator block is provided with a hole extending over the entire protrusion for fixing the insulator block to the arc chamber support. Preferably, towards the cathode holding plate, the insulator is provided with a peripheral flange extending between the outer protruding rib and the inner protruding rib of the cathode holding plate. The insulator block abuts at the edge of the insulator block against the protruding inner rib of the opening of the cathode holding plate. This edge creates a gap between the cathode holding plate and the insulator block. Further, this edge of the insulator block provides an arrangement in which the protrusion of the insulator block fits precisely within the opening of the cathode holding plate. The insulator block is made of a high-temperature ceramic material, preferably Al2O3, and electrically insulates the cathode holding plate. Further, the insulator block fixes the cathode holding plate to the arc chamber support when the cathode holding assembly is attached to the arc chamber support.

[0020] On the insulator block, a shielding cap is disposed on the side opposite to the protruding portion. In a preferred embodiment, the shielding cap is provided with a peripheral flange extending toward the cathode holding plate. In a more preferred embodiment, the shielding cap is only fixed to the insulator block by using at least one fixing device extending from the shielding cap to the insulator block. The shielding cap is attached in a floating manner (or a floating configuration) on the insulator block so that a gap provided between the cathode holding plate and the insulator block extends, that is, the gap continues between the shielding cap and the insulator block and between the shielding cap and the cathode holding plate. The shielding cap is made of stainless steel, a high melting point metal, a high melting point metal-based alloy, or ceramic. In the above-mentioned U.S. Patent No. 8,253,334, a shield is disposed on the cathode holding plate and the insulator block to prevent the formation of a conductive coating on the insulator block. Therefore, a configuration attached in a floating manner was not desirable in the prior art.

[0021] In a preferred embodiment, the shielding cap covers only the insulator block and the protruding outer rib of the cathode holding plate. In the above-mentioned U.S. Patent No. 8,253,334, the shield not only covers the insulator block but also covers most of the graphite support plate and most of the periphery of the collar (see, for example, FIGS. 3 and 4). Therefore, the collar of the prior art assembly was maintained within the holding portion, and the holding portion was maintained within the graphite support plate.

[0022] As described above, by using the cathode holding assembly described in the claims, a gap is defined between the cathode holding plate, the shielding cap, and the insulator block. This gap extends along the cathode holding plate and the shielding cap, and further extends between the cathode holding plate and the insulator block and terminates there. The size of the gap according to the present invention is 2 mm or less, preferably in the range of 0.4 mm to 1.5 mm, and more preferably in the range of 0.5 mm to 1.0 mm. This gap forms an extended and tortuous path, and when viewed in the direction from the cup-shaped shield (or shielding portion) towards the cathode holding plate based on the specific design of different parts of the cathode holding assembly, it has at least six turns (curvatures) and at least one side branch (or bifurcation). In a preferred embodiment, this side branch extends between the shielding cap and the insulator block. In a preferred embodiment, the shielding cap has a double gradient (or double gradation) towards the end of the insulator block on the opposite side of the protrusion and the fixing device (for example, the screw used to attach the shielding cap to the insulator block). Also, the insulator block may be provided with a step towards the shielding cap, and at that location, the gap between the double gradient of the shielding cap where the fixing device (for example, the screw) is arranged and the insulator block defines the side branch of the gap. Also, the width of the side branch is preferably 2 mm or less, preferably in the range of 0.4 mm to 1.5 mm, and more preferably in the range of 0.5 mm to 1.0 mm. Therefore, this plasma path is more extended compared to the paths disclosed in the prior art. During the ion beam operation of the arc chamber, such an extended and tortuous path delays the accumulation of a conductive plasma layer on the surface of the components of the cathode holding assembly. For this reason, the lifespan of the cathode holding assembly during ion beam operation can be extended.

[0023] In a preferred embodiment of the present invention, the shielding cap includes a peripheral flange extending toward the cathode holding plate, the cathode holding plate includes a protruding outer rib inside the peripheral flange overlapping with the peripheral flange, and further the insulator block includes an outer flange extending toward the cathode support plate inside the protruding outer rib. Accordingly, an extended and tortuous path / gap is provided such that the tortuous path is bent seven times and has one side branch.

[0024] In a preferred embodiment of the present invention, the components of the cathode holding assembly, particularly the cathode holding plate, the insulator block, and the shielding cap, are geometrically designed such that when these components are assembled together along the assembly direction, these components self-align. Accordingly, these components are positioned at the correct distances relative to each other with respect to the assembly direction and are correctly and firmly positioned relative to each other when attached to the arc chamber support. Since these components have correspondingly geometrically designed shapes, the feature of self-alignment is realized (this will be described in detail with reference to the drawings). In a preferred embodiment, this is achieved, for example, by the peripheral flange of the shielding cap overlapping with the protruding outer rib of the cathode holding plate overlapping with the outer flange of the insulator block, and the protrusion of the insulator block fitting into the opening of the cathode holding plate. Accordingly, the correct arrangement of these components is ensured when attached to the arc chamber support. Further, due to the self-aligning feature, no additional device or measuring device is required to accurately arrange the components of the cathode holding assembly.

[0025] The present invention also relates to an arc chamber support assembly of an ion implantation apparatus including the cathode holding assembly and the arc chamber support described in the claims. In this assembly, the insulator block is fixed to the arc chamber support using a fixing device, and this fixing device extends from the insulator block to the arc chamber support and is fixed by a locking member arranged on the side of the arc chamber support through a hole in the protrusion of the insulator block and a second hole in the recess in the arc chamber support.

[0026] The cathode holding assembly is disposed within a recess of the arc chamber support corresponding to the protruding portion of the insulator block, together with the protruding portion of the insulator block. The arc chamber support has a hole, that is, it has a second hole within the recess, and for this reason, a fixing device extends from the insulator block to the arc chamber support and passes through the hole of the protruding portion of the insulator block and the second hole within the recess of the arc chamber support, enabling the insulator block to be fixed to the arc chamber support. This fixing device, for example, a screw, is fixed using a locking member, for example, a lock nut disposed on the side portion of the arc chamber support. Accordingly, a second gap is defined to extend between the arc chamber support and the cathode holding plate, and further between the cathode holding plate and the insulator block, and terminate there.

[0027] In a preferred embodiment of the present invention, the fixing device is a screw and the locking member is a lock nut.

[0028] In a more preferred embodiment, the arc chamber support includes, in addition to the corresponding recess, an inner rib facing the cathode holding plate and an outer flange, and the cathode holding plate includes at least two protruding ribs facing the arc chamber support. In this case, at least two protruding ribs of the cathode holding plate facing the arc chamber support overlap with the inner rib and the outer flange of the arc chamber support, and the second gap provides a meandering path that extends between the arc chamber support and the cathode holding assembly, and further between the cathode holding plate and the insulator block, and terminates there.

[0029] When using an arc chamber support having one protruding portion towards the ion source assembly, the second gap is very small compared to the gaps known in the prior art. The size of the second gap according to the present invention is 2 mm or less, preferably within the range of 0.4 mm to 1.5 mm, and more preferably within the range of 0.5 mm to 1.0 mm. Accordingly, by using the arc chamber support assembly described in the claims, the size of the second gap can be minimized, and as a result, the gas lost within the arc chamber during ion beam operation is reduced.

[0030] Furthermore, as already outlined, the second gap generates an extended and meandering path which, when viewed from the side of the arc chamber support, includes at least seven turns (or bends) based on a specific design of different parts of the cathode holder assembly and the arc chamber support.

[0031] In a preferred embodiment, the protruding part of the insulator block is provided with at least one peripheral groove between the opening of the cathode holder plate and the recess of the arc chamber. Accordingly, the second gap further extends into and terminates in the peripheral groove of the insulator block, providing an extended second gap having at least eight turns. Further, by providing, for example, two peripheral grooves in the protruding part of the insulator block, the second gap is extended by side branches which preferably extend into the insulator block. Also, the width of the side branches is preferably 2 mm or less, preferably in the range from 0.4 mm to 1.5 mm, more preferably in the range from 0.5 mm to 1.0 mm. Accordingly, this plasma path is extended based on a specific design of the parts of the arc chamber support assembly as compared to the paths disclosed in the prior art. During the ion beam operation of the arc chamber, due to such an extended and meandering path, the accumulation of the conductive plasma layer on the surface of the parts of the repeller assembly is delayed. For this reason, the life of the cathode assembly during the ion beam operation is extended.

[0032] As described above, the components of the arc chamber support assembly self-align along the major longitudinal axis of the fixing device that extends through the insulator block and the arc chamber support when assembling these components together. The major longitudinal axis direction (or x-direction / axial direction) of the fixing device corresponds to the axial direction of the cylindrical shape of the fixing device when the fixing device is a screw. Therefore, these components are positioned axially at the correct distance relative to each other, positioned radially (perpendicular to the axial direction), and positioned correctly and firmly relative to each other. Further, due to the self-aligning feature, only a few fixtures are required to assemble the arc chamber support assembly. For this reason, in the arc chamber support assembly described in the claims, it is advantageous for providing a cathode assembly having better performance and a longer life (or service life) compared to the case of an insufficiently or incorrectly aligned assembly.

[0033] Regarding the above-described problems and other problems, the present invention also provides an arc chamber assembly of an ion implantation device including the arc chamber support outlined above and an arc chamber disposed on the arc chamber support.

[0034] Other features that can be considered characteristic of the present invention are described in the appended claims.

[0035] In this specification, the present invention is illustrated and described with respect to an embodiment embodied as a cathode holding assembly and an arc chamber support assembly including the cathode holding assembly. However, the present invention is not intended to be limited to what is described in detail here. This is because various modifications and structural changes are possible within the equivalent scope of the claims without departing from the technical idea of the present invention.

[0036] It should be noted that the structure and the operation method of the present invention will be best understood by reading the following detailed description with reference to the accompanying drawings in addition to further problems and advantages.

Brief Description of the Drawings

[0037]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

[0038] A detailed description will be given below with reference to the attached drawings. First, referring particularly to FIG. 1, a perspective view of the outside of the arc chamber 1 of the ion implantation apparatus is illustrated. The arc chamber 1 includes a cathode holding assembly according to the present invention. The cathode holding assembly is attached onto the arc chamber support 2. The arc chamber 1 has, in particular, at one end of the arc chamber, one outer wall, namely, the front wall 1a, to which an opening for attaching the cathode is provided. On the opposite side of the cathode, a repeller (or reflecting electrode) assembly is arranged. As shown in the figure, the cathode holding plate 3 has an opening 3b at the upper end, which is directed toward the opening of the arc chamber where the cathode is arranged. At this upper end of the cathode holding plate, a filament 15 is attached, which extends into the cavity of the arc chamber where the cathode is arranged (not visible in the figure). Around the opening 3b, a shaftless cathode retainer (or shaftless cathode retentainer) 16 is arranged. The lower end of the cathode holding plate 3 is attached to the arc chamber support 2. The lower end of this cathode holding plate 3 is covered by a shielding cap 5. The insulator block of the cathode holding assembly is not visible in the figure. A filament clamp (or filament clip) 9 is attached to the insulator block 4 (see FIG. 2), and is fixed to a filament strap (or filament band) 10 by a lock nut 13. As is apparent from FIG. 1, the arc chamber support 2 is dimensioned to support the arc chamber 1, and only the lower end of the cathode holding plate is attached to the arc chamber support 2.

[0039] Figure 2 illustrates the cathode holding assembly recited in the claims. In this figure, it is shown that the cathode holding plate 3 is provided with a rectangular opening 3a at the lower end of the cathode holding plate and a circular opening 3b at the upper end of the cathode holding plate. Further, the cathode holding plate is provided with a protruding outer rib 3d and a protruding inner rib 3c (on the side facing the shielding cap and the insulator block). The insulator block 4 includes, among other things, an outer flange 4b and a protruding portion 4a facing the cathode holding plate. When the insulator block is attached to the cathode holding plate, the protruding portion 4a is passed through the opening 3a of the cathode holding plate, so that the protruding outer rib 3d of the cathode holding plate 3 is overlapped with the outer flange 4b of the insulator block 4. A shielding cap 5 is attached to the insulator block / cathode holding plate assembly. The peripheral flange 5a of the shielding cap 5 extending toward the cathode holding plate is overlapped with the protruding outer rib 3d of the cathode holding plate 3. All the components of the cathode holding assembly are adapted to self-align along the assembly direction based on the specific geometric design (e.g., protrusions and depressions) of these components when these components are assembled together.

[0040] Figure 3 shows the cathode holding assembly described in the claims and illustrated in Figure 2 in association with a further part of the cathode assembly mounted on the arc chamber support, where the filament extends into the cavity of the arc chamber. In this figure, among other things, the cathode holding plate 3, the insulator block 4, and the shielding cap 5, as well as the fixing devices 6, 8, 11, 12, 13, and the locking members 11a, 14 are illustrated. In order for the components of the cathode holding assembly to be assembled together, two fixing devices 11, for example, square head screws, are introduced into the insulator block 4 from the side of the cathode holding plate, pass through the insulator block, the shielding cap 5, and the filament clamp 9, and are fixed to the side of the filament clamp 9 opposite the shielding cap by a locking member 11a, for example, a lock nut. The cathode holding plate is attached to the insulator block by two fixing devices 12, for example, screws, introduced into the cathode holding plate from the side of the arc chamber support. The protrusion 4a of the insulator block 4 is passed through the opening 3a of the cathode holding plate 3. Further, since fixing means 6, for example, screws, are completely passed through the hole (not visible in this figure) of the protrusion 4a of the insulator block 4, it is possible to attach the insulator block to the arc chamber support (not shown). The shielding cap 5 is attached to the insulator block 4 and is fixed only to the insulator block by two fixing devices 8, for example, screws. For this reason, the shielding cap is attached to the insulator block in a floating manner and covers the protruding outer rib 3d of the cathode holding plate and the insulator block. The filament clamp 9 is arranged on the insulator block 4 and is fixed by the locking member 11a (for example, a lock nut) as described above, so that the filament clamp 9 is attached to the assembly. Further, in this figure, the filament 15 introduced into the opening 3b of the cathode holding plate is shown. Inside the opening 3b of this cathode holding plate, the cathode 17 and the shaftless cathode holder 16 are arranged. In this figure, further, a filament strap 10 attached to the filament clamp 9 by a fixing device 13, for example, a screw, is shown.

[0041] In the major longitudinal axis direction of the range of the holes extending through the protrusion 4a of the insulator block 4, that is, along the central axis of the holes or the fixing device 6, all the components of the cathode holding assembly are assembled together. In the figure, it is shown that the cathode holding plate, the insulator block, and the shielding cap are self-aligning along the major longitudinal axis direction of the fixing device 6. Therefore, when attaching the components of the cathode assembly onto the arc chamber support, correct placement among these components is ensured. In a preferred embodiment, screws are used to fix the separate components to each other. The number of fixings required in the prior art assemblies can usually be reduced by the design of the cathode holding plate, the insulator block, and the shielding cap. Therefore, the cathode holding assembly can be easily assembled and minimizes the number of tools usually required.

[0042] FIG. 4A illustrates a cross-sectional view of an embodiment of the arc chamber support assembly according to the claims, including the cathode holding assembly according to the claims. In the figure, the cathode holding assembly is attached to the arc chamber support 2. As shown in the figure, the cathode holding plate 3 is provided with a protruding inner rib 3c and a protruding outer rib 3d facing the shielding cap. The protruding inner rib 3c is aligned or positioned with the rectangular opening 3a of the cathode holding plate. Further, as shown in the figure, the cathode holding plate is provided with two protruding ribs facing the arc chamber support, and the arc chamber support is provided with an inner rib 2c and an outer flange 2d facing the cathode holding plate. Therefore, these inner rib 2c and outer flange 2d are overlapped with the protruding ribs of the cathode holding plate. When the arc chamber support assembly is assembled, the protrusion 4a of the insulator block 4 is passed through the opening 3a of the cathode holding plate into the corresponding recess 2b of the arc chamber support 2. As is clear from the figure, the protrusion 4a of the insulator block is accurately fitted into the recess 2b provided in the arc chamber support 2. The arc chamber support shown in the above-mentioned prior art documents was provided with a protrusion that slidably fitted into the insulator block. However, the prior art documents did not show an arc chamber support having a recess.

[0043] The insulator block 4 has an outer flange 4b, which is superimposed on the protruding outer rib 3d of the cathode holding plate. Further, the insulator block has an edge portion so that the protruding inner rib 3c of the cathode holding plate can be attached thereto, whereby the protruding portion 4a of the insulator block is accurately fitted into the opening 3a of the cathode holding plate. A hole 4d extending over the entire protruding portion of the insulator block is provided in the protruding portion of the insulator block. A fixing device 6 is introduced into this hole 4d from the side opposite to the cathode holding plate, and the insulator block is fixed to the arc chamber support by a locking member 7, for example, a lock nut. To enable this, a hole, i.e., a second hole, is provided in the recess of the arc chamber support, and a lock nut is arranged on the side portion of the arc chamber support.

[0044] The shielding cap 5 is attached to the insulator block by two fixing devices 8, and at this time, the shielding cap is attached to the insulator block in a floating manner. The shielding cap is provided with a peripheral flange 5a so as to cover the protruding outer rib 3d of the cathode holding plate.

[0045] In this embodiment, the components of the arc chamber support assembly self-align when these components are assembled together along the range in the main longitudinal axis direction of the fixing device 6. In the range shown in the figure, this main longitudinal axis direction is shown as the x-axis (axial direction). The geometric shapes of the components of the arc chamber support assembly are defined so that these components can accurately self-align at fixed positions in the x-direction, y-direction, and z-direction. Therefore, the cathode holding assembly described in the claims can be easily attached to the arc chamber support, and at this time, no additional device or measuring device that is usually required to correctly arrange the components of the cathode assembly within the opening of the wall of the arc chamber is required.

[0046] Figure 4B shows the same arc chamber support assembly as illustrated in Figure 4A, but in this figure, one gap and a second gap are emphasized, which are defined when the cathode holding assembly is mounted on the arc chamber support. This gap extends between the cathode holding plate and the shielding cap and further extends between the cathode holding plate and the insulator block and terminates there. In this embodiment, a side branch is shown between the shielding cap and the insulator block. At this time, the black line indicates the plasma / gas flow from the inside of the arc chamber to the outside of the arc chamber. As shown, the gas or gas flows along the shielding cap and then flows between the cathode holding plate and the shielding cap and between the cathode holding plate and the insulator block and terminates there. Therefore, an extended and tortuous gap for the plasma flow is provided, and this gap has seven curved portions (or turns) and one side branch (as seen from the shielding cap). For this reason, the time until the entire gap is covered with plasma is extended, resulting in a longer service life of the arc chamber. In addition, Figure 4B shows a further gap. This further gap extends between the cathode holding plate and the arc chamber support and then extends between the arc chamber support and the insulator block and terminates there. In this preferred embodiment, since the protrusion of the insulator block has two circumferential grooves, the second gap further extends into the insulator block and terminates there. In the same figure, the extended and tortuous second gap for the plasma flow has seven curved portions and one side branch. Also, in the same figure, it is shown that the width of the gap and the second gap is 2 mm or less along their entire length.

[0047] Therefore, the cathode holding assembly provided by the invention described in the claims can improve the life performance of the ion implantation apparatus during ion beam operation when mounted on the arc chamber support of the ion implantation apparatus. Therefore, the invention described in the claims reduces the frequency of maintenance stops in the arc chamber.

[0048] With a configuration in which multiple components self-align, it becomes possible to correctly install the cathode holding assembly without using additional equipment or measuring devices.

[0049] The following is a list of the outlines of the structures corresponding to the reference numbers used in the detailed description of the present invention described above.

Explanation of Signs

[0050] 1 Arc chamber (or arc chamber) 1a Front wall of the arc chamber 2 Arc chamber support (or arc chamber support) 2a Opening of the arc chamber support 2b Recess of the arc chamber support 2c Inner rib of the arc chamber support 2d Outer flange of the arc chamber support 3 Cathode holding plate (or cathode holding plate) 3a Rectangular opening of the cathode holding plate 3b Circular opening of the cathode holding plate 3c Inner rib protruding towards the shielding cap of the cathode support plate 3d Outer rib protruding towards the shielding cap of the cathode support plate 4 Insulator block (or insulator block) 4a Protrusion of the insulator block towards the cathode holding plate 4b Outer flange of the insulator block towards the cathode holding plate 4c Edge of the insulator block 5 Shielding cap (or shield cap) 5a Peripheral flange of the shielding cap 5b Hole for fixing the device of the shielding cap to the insulator block 6 Fixing device, preferably a screw 7 Locking member, preferably a lock nut 8 Screw 9 Filament clamp 10 Filament strap 11 Fixing member, for example, square head screw 11a, 14 Locking member, preferably lock nut 12, 13 Fixing members, preferably screws 15 Filament 16 Shaftless cathode retainer 17 Cathode (or negative electrode)

Claims

1. A cathode holding assembly attached to an arc chamber support of an ion implantation apparatus, comprising a cathode holding plate, an insulator block, and a shielding cap, The cathode holding plate is formed to include a protruding outer rib facing the shielding cap and an opening having a protruding inner rib facing the shielding cap, The insulator block is formed to include a protruding portion configured to penetrate the opening of the cathode holding plate and be inserted into a corresponding recess of the arc chamber support. A through hole for fixing the insulator block to the arc chamber support is formed in the protruding portion of the insulator block, The insulator block abuts at an edge of the insulator block against the protruding inner rib of the opening of the cathode holding plate to ensure that the insulator block fits precisely within the opening of the cathode holding plate, The shielding cap is disposed on a side of the insulator block opposite to the protruding portion and defines a gap, which gap is defined to extend between and terminate at the cathode holding plate and the shielding cap, and further between the cathode holding plate and the insulator block, Cathode holding assembly.

2. The cathode holding assembly according to claim 1, wherein the width of the gap is 2 mm or less.

3. The cathode holding assembly according to claim 1 or 2, wherein the gap follows a meandering path including at least six curved portions and at least one side branch.

4. The cathode holding assembly according to any one of claims 1 to 3, wherein the shielding cap is fixed only to the insulator block by at least one fixing device extending from the shielding cap into the insulator block.

5. The cathode holding assembly according to any one of claims 1 to 4, wherein the shielding cap is disposed to cover only the insulator block and the protruding outer rib of the cathode holding plate.

6. The cathode holding assembly according to any one of claims 1 to 5, wherein each component of the cathode holding assembly is geometrically designed to self-align along an assembly direction when the components are assembled together.

7. The shielding cap includes a peripheral flange extending toward the cathode holding plate, and the protruding outer rib of the cathode holding plate is disposed inside the peripheral flange and is overlapped by the peripheral flange. The insulator block is formed to include an outer flange extending toward the cathode holding plate inside the protruding outer rib, according to any one of claims 1 to 6. The cathode holding assembly.

8. The cathode holding plate is made of a high melting point metal or a high melting point metal system, according to any one of claims 1 to 7. The cathode holding assembly.

9. An arc chamber support assembly of an ion implantation apparatus, An arc chamber support, and the cathode holding assembly according to any one of claims 1 to 8 attached to the arc chamber support, An insulator block, and the insulator block is attached to the arc chamber support by a fixing device extending from the insulator block to the arc chamber support. The fixing device passes through a hole in a protruding portion of the insulator block and a second hole in a recess of the arc chamber support and is fixed to a locking member disposed on a side portion of the arc chamber support. Arc chamber support assembly.

10. The fixing device is a screw, and the locking member is a lock nut. The arc chamber support assembly according to claim 9.

11. The arc chamber support includes an inner rib and an outer flange facing the cathode holding plate. The cathode holding plate is formed to include at least two protruding ribs facing the arc chamber support. The ribs are overlapped with the inner rib and the outer flange of the arc chamber support to define a second gap. The second gap extends between the cathode holding plate and the arc chamber support and between the cathode holding plate and the insulator block and terminates there. The arc chamber support assembly according to claim 9 or 10.

12. The protruding portion of the insulator block is formed to include at least one peripheral groove, and the second gap extends into the at least one groove of the insulator block and terminates there. The arc chamber support assembly according to any one of claims 9 to 11.

13. The width of the second gap is 2 mm or less. The arc chamber support assembly according to any one of claims 9 to 12.

14. The second gap forms a meandering path including at least seven curved portions, the arc chamber support assembly according to any one of claims 9 to 13.

15. The shielding cap, the insulator block, the cathode holding plate, and the arc chamber support are geometrically configured to self-align along the major longitudinal axis direction within the range of the fixing device extending through the insulator block and the arc chamber support when they are assembled, the arc chamber support assembly according to any one of claims 9 to 14.

16. An arc chamber assembly of an ion implantation device, The arc chamber support assembly according to any one of claims 9 to 15, An arc chamber disposed on the arc chamber support, Comprising an arc chamber assembly.

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