Cathode-holding assembly and arc chamber support assembly with cathode-holding assembly

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 holder assembly (or cathode support assembly) that is mounted on an arc chamber support of an ion implanter. More specifically, the present invention relates to the various components of the cathode holder assembly, their respective designs, their relative arrangements, and their arrangement on the arc chamber support. Additionally, the present invention relates to an arc chamber support assembly having a cathode holder assembly, and an arc chamber assembly of an ion implanter that includes the arc chamber support assembly. [Background technology]

[0002] Ion implanters are widely used in the manufacture of semiconductor components to modify various regions of semiconductor wafers by diffusing or implanting positive or negative ions (dopants) into the wafer surface to create regions with different properties (e.g., conductivity, etc.) These ion implanters include an arc chamber to generate a plasma containing the various ion species that are implanted into the surface of the semiconductor wafer.

[0003] In one common arc chamber configuration, a cathode assembly is positioned opposite a repeller (anticathode). During arc chamber operation, the cathode assembly is heated, e.g., by a filament, so that it emits electrons by thermionic emission during operation. A relatively positive arc voltage on the arc chamber walls accelerates the electrons into the arc chamber, and an externally generated magnetic field causes the electrons to spiral into the arc chamber. Emitter and repeller electrodes, which are typically negatively biased relative to the arc chamber walls, confine the emitted electrons. The combined effect of the emitter and repeller electrodes focuses the electrons toward the center of the arc chamber, maximizing their interaction with the dopant gas introduced into the arc chamber via a conduit, thereby achieving a plasma with desired characteristics.

[0004] During operation, the arc chamber contains numerous molecular species at very high temperatures. In this harsh environment, components (including those of the cathode support assembly) are subjected to conditions that can unduly limit their lifespan or effectiveness, limiting the effectiveness of the ion implanter and / or increasing its operating costs. For example, plasma films tend to deposit on parts of the cathode support assembly, such as the cathode support plate, insulator block, and shielding cap. This plasma coating on the insulator block can create short circuits, for example, between the cathode support plate and the filament / filament clamp, or between the cathode support plate and the arc chamber, or between the filament clamp and the arc chamber, which can cause the ion source to shut down. Therefore, it is desirable to provide an extended, tortuous coating path to prolong the coating process (and corresponding short circuit occurrence) of electrically isolated or insulated components. Furthermore, the size of the gaps or clearances in the cathode assembly can lead to other failure modes, such as gas leakage from the arc chamber. Furthermore, the assembly of the cathode assembly is not very simple, requiring numerous fasteners (eg, screws, alignment and gap adjustment tools).

[0005] Several cathode holder assembly configurations are known in the prior art.

[0006] U.S. Patent No. 8,253,334 discloses an ion source assembly, arc chamber, and arc chamber support (see FIG. 10). The arc chamber support is sized to support the arc chamber and has a forward end with a protrusion for a sliding fit within the insulator block (see FIG. 10B). FIG. 9 shows the insulator block having an undercut, which helps prevent the buildup of conductive coating along its surface, which could cause short circuits. In this configuration, the insulator block is attached to the arc chamber support by a socket head cap screw, and the shield is attached to the graphite support plate by two socket head shoulder screws, which cover, among other things, the insulator block and the graphite support plate. The shield has an upper end shaped in a bifurcated manner to overlie the main portion of the graphite support plate and is retained by a collar in a retainer and a retainer in the support plate. A sleeve is mounted within the opening of the arc chamber and projects outwardly into the space in the graphite support plate, defining a serpentine gap to throttle the flow of plasma from the interior cavity of the arc chamber.

[0007] In the above-mentioned patents, when a plasma path is provided, its length is limited. Furthermore, the assembly of the cathode holder assembly according to the prior art requires many fasteners, making the assembly difficult. Also, as is known, the prior art requires multiple tools and work steps to secure the components of the cathode holder assembly together and to attach the cathode holder assembly to the arc chamber support.

[0008] Therefore, there is still room for improvement in the design of cathode holding assemblies to improve the life and effectiveness of the cathodes, and therefore the life and effectiveness of the arc chamber. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 8,253,334 Summary of the Invention [Problem to be solved by the invention]

[0010] A primary object of the present invention is to provide a cathode holder assembly that achieves increased operating time for an ion implanter. Increased operating time has the effect of, among other things, reducing the operating costs of the ion implanter. A further object of the present invention is to provide a cathode holder assembly that is easy to assemble and requires minimal tooling. [Means for solving the problem]

[0011] In view of the above and other objects, the present invention provides a cathode holder assembly for mounting to an arc chamber support of an ion implanter, the cathode holder assembly comprising a cathode holder plate, an insulator block, and a shielding cap. The cathode retaining plate is formed with an opening having a protruding outer rib toward the shielding cap and a protruding inner rib toward the shielding cap. The insulator block is formed with a protrusion (or projection) configured to pass through the opening in the cathode retaining plate and be inserted into a corresponding recess in the arc chamber support, and the protrusion of the insulator block has a through hole formed therein for securing the insulator block to the arc chamber support. The insulator block abuts at its edge against the protruding inner rib of the opening in the cathode retainer plate to ensure a precise fit of the insulator block within the opening in the cathode retainer plate. The shielding cap is positioned on the side of the insulator block opposite the protrusion to define a gap that extends and terminates between the cathode retaining plate and the shielding cap, and further between the cathode retaining plate and the insulator block.

[0012] In other words, the object of the present invention can be achieved by providing a cathode holding assembly for mounting to an arc chamber support of an ion implanter, the cathode holding assembly comprising a cathode holding plate, an insulator block, and a shielding cap. The cathode retainer plate has an opening with a protruding outer rib toward the shielding cap and a protruding inner rib toward the shielding cap to allow the protrusion of the insulator block to pass through the opening in the cathode retainer plate and be inserted into a corresponding recess in the arc chamber support. The protrusion of the insulator block includes a hole extending therethrough to secure the insulator block to the arc chamber support. The insulator block abuts the protruding inner rib of the cathode holder plate opening at its edge to ensure a precise fit of the insulator block within the cathode holder plate opening, and a shielding cap is positioned on the side of the insulator block opposite the protrusion to define a gap extending and terminating between the cathode holder plate and the shielding cap, and further between the cathode holder plate and the insulator block, as described in the claims. It is envisioned that this new cathode holder assembly will be mounted on an arc chamber support of an ion implanter. However, the arc chamber support itself does not form part of the invention described in independent claim 1. The arc chamber support merely describes the interaction between the components of the cathode holder assembly. Further, an arc chamber support assembly for an ion implanter is provided, in which the claimed cathode holder assembly is mounted to have the features described in the claims. Further, an ion implanter arc chamber assembly using the arc chamber support generally described is described and claimed below.

[0013] Further features and details of the invention are set out in the dependent claims, the detailed description and the drawings. It goes without saying that the features and details described with respect to the cathode holder assembly according to the invention also apply to the arc chamber support assembly and arc chamber assembly according to the invention, and vice versa. For this reason, the disclosures of the individual aspects of the invention are or can be made to refer to one another.

[0014] The inventors have found that the claimed cathode holder assembly provides an extended, tortuous coating path compared to the prior art, even when only one insulator is used in the assembly. In 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. Additionally, the claimed cathode holder assembly reduces gas loss from the arc chamber during ion beam operation because the gap between the components of the claimed cathode holder assembly / arc chamber support assembly is smaller compared to the prior art. The extended coating path and smaller gaps allow for extended arc chamber life during ion beam operation. Furthermore, the claimed cathode holder assembly can reduce the frequency of maintenance shutdowns within the arc chamber.

[0015] One advantage of the present invention is that the components of the claimed cathode holder assembly, i.e., at least the cathode holder plate, insulator block, and shielding cap, are self-aligning or self-matching. Furthermore, the cathode holder assembly and the arc chamber support are self-aligning. This means that when these components are assembled together and attached to the arc chamber support, they automatically align with respect to each other. The precise distance between the repeller assembly and the cathode assembly also automatically aligns. As noted above, prior art documents required numerous fixtures to assemble the ion source assembly to the arc chamber support. By using the claimed cathode holder assembly or arc chamber support assembly, the number of fixtures (and the number of tools required to adjust the fixtures) can be reduced when assembling the claimed cathode holder assembly and attaching it to the arc chamber support.

[0016] Because ion source assemblies are exposed to high temperatures and chemically rich environments, single components of the assembly, such as screws, often become worn against their mating assemblies. In the present invention, the screws that hold the filament clamp to the cathode retaining plate and the cathode retaining plate to the arc chamber support are preferably attached to mating nuts (see locking member 7 in FIG. 4A and locking member 11a in FIG. 3). In this configuration, even if wear occurs, the nuts and screws can be destructively separated without damaging the filament clamp, cathode retaining support, or arc chamber support.

[0017] The cathode holder plate of the claimed cathode holder assembly is a monolithic plate having a circular opening at its upper end to receive a holder or retainer (containing a filament) and a rectangular (or oblong) opening at its lower end to allow the protrusion of the insulator block to pass through. The cathode holder plate has an inner rib protruding toward the shielding cap and an outer rib protruding toward the shielding cap in the area covered by the claimed structure (i.e., the lower end of the cathode holder plate opposite the arc chamber support). The inner rib protruding toward the cathode holder plate is aligned or registered with the opening in the cathode holder plate. The outer rib protruding toward the insulator block is overlapped with a flange of the insulator block. The cathode holder plate also has at least two ribs protruding toward the arc chamber support. The arrangement of these ribs will be described later in connection with the arc chamber support assembly.

[0018] The cathode support plate is made of graphite, a refractory metal (or refractory metal), or a refractory metal alloy (or refractory metal). Refractory metals refer to high-melting-point base metals (or base metals) of the fifth subgroup (vanadium, niobium, and tantalum) and the sixth subgroup (chromium, molybdenum, and tungsten). Their melting points are higher than that of platinum (1772°C). Refractory metal alloys can refer to combinations of several pure refractory metals (e.g., W and Mo), as well as their alloys (e.g., W-Re) and / or their compounds. In the context of the present invention, refractory metal alloys are understood to mean alloys containing at least 80% by weight, preferably at least 90% by weight, of one or more refractory metals. Among the refractory metals, Mo and W, as well as Mo- and W-based alloys, are particularly suitable. In this context, in Mo-based or W-based alloys, the proportion of Mo (or W) is 80% by weight or more, in particular 90% by weight or more or >95% by weight or more. Mo or Mo-based alloys are particularly advantageous because molybdenum has a very high melting point, low thermal expansion and high thermal conductivity (which is also advantageous from the cost point of view).

[0019] The insulator block has a protrusion at one end that fits precisely within an opening in the cathode retainer plate. When the cathode retainer assembly is attached to the arc chamber support, the protrusion passes through the opening and into a corresponding recess in the arc chamber support. The protrusion of the insulator block is provided with a hole extending the entire length of the protrusion for securing the insulator block to the arc chamber support. Preferably, the insulator is provided with a peripheral flange extending toward the cathode retainer plate between the outer and inner protruding ribs of the cathode retainer plate. The insulator block abuts at its edge against the protruding inner rib of the opening in the cathode retainer plate. This edge provides a gap between the cathode retainer plate and the insulator block. The edge of the insulator block also ensures that the protrusion of the insulator block fits precisely within the opening in the cathode retainer plate. The insulator block is made of a high-temperature ceramic material, preferably Al2O3, and electrically insulates the cathode retainer plate. Additionally, the insulator block secures the cathode retainer plate to the arc chamber support when the cathode retainer assembly is attached to the arc chamber support.

[0020] A shielding cap is disposed on the insulator block opposite the protrusion. In a preferred embodiment, the shielding cap has a peripheral flange extending toward the cathode retaining plate. In a more preferred embodiment, the shielding cap is simply secured to the insulator block using at least one fastener extending from the shielding cap to the insulator block. The shielding cap is mounted in a floating manner (or a floating configuration) on the insulator block so that a gap provided between the cathode retaining plate and the insulator block extends, i.e., the gap continues between the shielding cap and the insulator block and between the shielding cap and the cathode retaining plate. The shielding cap is made of stainless steel, a refractory metal, a refractory metal alloy, or a ceramic. In the aforementioned U.S. Patent No. 8,253,334, a shield is disposed on the cathode retaining plate and the insulator block to prevent a conductive coating from forming on the insulator block. Therefore, a floating mounting configuration was undesirable 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 retainer plate. In the aforementioned 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, e.g., Figures 3 and 4). Thus, the collar in the prior art assemblies was retained within the retainer, which in turn was retained within the graphite support plate.

[0022] As described above, with the cathode holder assembly of the present invention, a gap is defined between the cathode holder plate, the shielding cap, and the insulator block. This gap extends along the cathode holder plate and the shielding cap, and further extends between and terminates between the cathode holder plate and the insulator block. 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 elongated, tortuous path, and has at least six turns and at least one branch when viewed from the cup-shaped shield toward the cathode holder plate, depending on the specific design of the different portions of the cathode holder assembly. In a preferred embodiment, this branch extends between the shielding cap and the insulator block. In a preferred embodiment, the shielding cap has a double gradation toward the end of the insulator block opposite the protrusion and the fastening device (e.g., a screw used to attach the shielding cap to the insulator block). The insulator block may also have a step toward the shielding cap, where the fastening device (e.g., a screw) is located. The gap between the double gradation of the shielding cap and the insulator block defines a side branch of the gap. 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. This plasma path is therefore more elongated than paths disclosed in the prior art. During ion beam operation in the arc chamber, this elongated, tortuous path delays the buildup of a conductive plasma layer on the surfaces of the cathode support assembly components. This, in turn, extends the life of the cathode support assembly during ion beam operation.

[0023] In a preferred embodiment of the invention, the shielding cap has a peripheral flange extending toward the cathode retainer plate, the cathode retainer plate has a protruding outer rib inwardly of the peripheral flange that overlaps the peripheral flange, and the insulator block has an outer flange inwardly of the protruding outer rib that extends toward the cathode support plate, thus providing a serpentine path such that the elongated serpentine path / gap has seven bends and one side branch.

[0024] In a preferred embodiment of the present invention, the components of the cathode holder assembly, particularly the cathode holder plate, insulator block, and shielding cap, are geometrically designed so that they self-align when assembled together along the assembly direction. Therefore, these components are positioned at the correct distance from one another in the assembly direction, and are correctly and securely positioned relative to one another when attached to the arc chamber support. The self-alignment feature is realized because these components have corresponding geometrically designed shapes (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 the protruding outer rib of the cathode holder plate overlapping the outer flange of the insulator block, and the protrusion of the insulator block fitting into the opening in the cathode holder plate. Therefore, the correct positioning of these components is ensured when attached to the arc chamber support. Furthermore, due to the self-alignment feature, no additional or measuring device is required to accurately position the components of the cathode holder assembly.

[0025] The present invention also relates to an arc chamber support assembly for an ion implanter, comprising the cathode holder assembly of claim 1 and an arc chamber support, wherein an insulator block is secured to the arc chamber support by a fastening device extending from the insulator block to the arc chamber support, passing through a hole in the protrusion of the insulator block and a second hole in the recess of the arc chamber support, and secured by a locking member disposed on the side of the arc chamber support.

[0026] The cathode holder assembly is positioned with the protrusion of the insulator block in a recess of the arc chamber support that corresponds to the protrusion of the insulator block. The arc chamber support has a hole, i.e., a second hole in the recess, so that the insulator block can be secured to the arc chamber support by a fastening device extending from the insulator block to the arc chamber support and passing through the hole in the protrusion of the insulator block and the second hole in the recess of the arc chamber support. This fastening device, e.g., a screw, is secured with a locking member, e.g., a lock nut, located on the side of the arc chamber support. Thus, a second gap is defined between the arc chamber support and the cathode holder plate, and further between the cathode holder plate and the insulator block, terminating therein.

[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 further preferred embodiment, the arc chamber support includes, in addition to the corresponding recess, an inner rib and an outer flange toward the cathode retainer plate, and the cathode retainer plate includes at least two protruding ribs toward the arc chamber support, wherein the at least two protruding ribs of the cathode retainer plate toward the arc chamber support overlap the inner ribs and outer flange of the arc chamber support, and a second gap provides a tortuous path extending between the arc chamber support and the cathode retainer assembly and between the cathode retainer plate and the insulator block, where it terminates.

[0029] When using an arc chamber support having a single protrusion toward the ion source assembly, the second gap is significantly smaller than gaps known in the prior art. The size of the second 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. Therefore, by using the arc chamber support assembly according to the present invention, the size of the second gap can be minimized, thereby reducing gas loss in the arc chamber during ion beam operation.

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

[0031] In a preferred embodiment, the protrusion of the insulator block is provided with at least one peripheral groove between the opening in the cathode retainer plate and the recess in the arc chamber. Thus, the second gap extends further into the peripheral groove of the insulator block and terminates there, providing an extended second gap having at least eight turns. Furthermore, the protrusion of the insulator block is provided with, for example, two peripheral grooves, thereby extending the second gap with a side branch. This side branch preferably extends into the insulator block. Furthermore, 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, the plasma path is extended based on the specific design of the arc chamber support assembly components compared to paths disclosed in the prior art. During ion beam operation of the arc chamber, this extended, tortuous path delays the buildup of a conductive plasma layer on the surfaces of the repeller assembly components. This, in turn, extends the life of the cathode assembly during ion beam operation.

[0032] As described above, the components of the arc chamber support assembly self-align along the major longitudinal axis of the fastener, which extends through the insulator block and the arc chamber support, when the components are assembled together. The major longitudinal axis (or x-direction / axial direction) of the fastener corresponds to the axial direction of the cylindrical shape of the fastener, if the fastener is a screw. Thus, the components are correctly and securely positioned relative to each other, axially positioned at the correct distance from each other, and radially positioned (perpendicular to the axial direction). Furthermore, because of the self-aligning feature, only a small number of fasteners are required to assemble the arc chamber support assembly. Therefore, the claimed arc chamber support assembly advantageously provides a cathode assembly with better performance and a longer lifespan (or service life) than an assembly that is poorly or incorrectly aligned.

[0033] With regard to the above and other objectives, the present invention also provides an arc chamber assembly for an ion implanter that includes an arc chamber support as generally described above and an arc chamber disposed on the arc chamber support.

[0034] Other features which may be considered characteristic of the invention are set forth in the appended claims.

[0035] Although the present invention is illustrated and described herein as embodied in a cathode holder assembly and an arc chamber support assembly including the cathode holder assembly, it is not intended that the present invention be limited to the details set forth herein, as various modifications and structural changes may be made within the scope and equivalents of the claims without departing from the spirit of the present invention.

[0036] The structure and method of operation of the present invention, together with further objects and advantages thereof, will best be understood by reading the following detailed description when read in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0037] [Figure 1]FIG. 1 is a perspective view of an arc chamber for an ion implanter according to the present invention. [Figure 2] FIG. 2 is an exploded perspective view of a cathode holder assembly according to the present invention. [Figure 3] FIG. 3 is an exploded perspective view of the cathode assembly (ion source assembly) including the cathode holder assembly according to the present invention, as well as filament clamps, filament straps, cathode holders, screws, bolts, nuts, and the like. [Figure 4A] FIG. 4A is a cross-sectional view of a cathode holder assembly attached to the arc chamber support of the ion implanter illustrated in FIG. 1 in accordance with one embodiment of the present invention. [Figure 4B] FIG. 4B is a cross-sectional view of a cathode holder assembly attached to the arc chamber support of the ion implanter illustrated in FIG. 1 in accordance with one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] The following detailed description will be provided with reference to the accompanying drawings. Referring specifically to FIG. 1, an exterior perspective view of an arc chamber 1 of an ion implanter is illustrated. The arc chamber 1 includes a cathode retaining assembly according to the present invention. The cathode retaining assembly is mounted on an arc chamber support 2. The arc chamber 1 includes, among other things, an outer wall, i.e., a front wall 1a, at one end of the arc chamber, which has an opening for mounting a cathode. A repeller (or repeller electrode) assembly is located on the opposite side of the cathode. As shown in the figure, a cathode retaining plate 3 has an opening 3b at its upper end, which faces the opening of the arc chamber where the cathode is located. A filament 15 is attached to the upper end of the cathode retaining plate, which extends into the arc chamber cavity where the cathode is located (not visible in the figure). A shaftless cathode retainer 16 is positioned around the opening 3b. The lower end of the cathode retaining plate 3 is attached to the arc chamber support 2. The lower end of the cathode retainer plate 3 is covered by a shielding cap 5. The insulator block of the cathode retainer assembly is not visible in this view. A filament clamp (or filament clamp) 9 is attached to the insulator block 4 (see FIG. 2) and is secured 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 sized to support the arc chamber 1, and only the lower end of the cathode retainer plate is attached to the arc chamber support 2.

[0039] FIG. 2 illustrates a cathode holder assembly as claimed. The figure shows that the cathode holder plate 3 has a rectangular opening 3a at its lower end and a circular opening 3b at its upper end. Furthermore, the cathode holder plate has a protruding outer rib 3d and a protruding inner rib 3c (on the side facing the shielding cap and insulator block). The insulator block 4 has, among other things, an outer flange 4b ​​toward the cathode holder plate and a protrusion 4a. When the insulator block is attached to the cathode holder plate, the protruding outer rib 3d of the cathode holder plate 3 overlaps with the outer flange 4b ​​of the insulator block 4. A shielding cap 5 is attached to the insulator block / cathode holder plate assembly. The peripheral flange 5a of the shielding cap 5, which extends toward the cathode holder plate, overlaps with the protruding outer rib 3d of the cathode holder plate 3. All parts of the cathode holding assembly are self-aligning along the assembly direction when they are assembled together based on the specific geometric designs (eg, protrusions and recesses) of the parts.

[0040] FIG. 3 shows the cathode holder assembly as claimed and illustrated in FIG. 2 in association with additional portions of the cathode assembly mounted on the arc chamber support, with the filament extending into the arc chamber cavity. This figure illustrates, among other things, the cathode holder plate 3, the insulator block 4, and the shielding cap 5, as well as the fasteners 6, 8, 11, 12, 13, and the locking members 11a and 14. To assemble the cathode holder assembly components together, two fasteners 11, e.g., square-head screws, are introduced into the insulator block 4 from the side of the cathode holder plate, pass through the insulator block, the shielding cap 5, and the filament clamp 9, and are secured to the side of the filament clamp 9 opposite the shielding cap by the locking member 11a, e.g., a lock nut. The cathode holder plate is attached to the insulator block by two fasteners 12, e.g., screws, introduced into the cathode holder plate from the side of the arc chamber support. The protruding portion 4a of the insulator block 4 passes through the opening 3a of the cathode holder plate 3. Furthermore, a fastening means 6, e.g., a screw, passes completely through a hole (not visible in the figure) in the protruding portion 4a of the insulator block 4, allowing the insulator block to be attached to an arc chamber support (not shown). The shielding cap 5 is attached to the insulator block 4 and is secured to the insulator block only by two fastening devices 8, e.g., screws. Thus, the shielding cap is attached to the insulator block in a floating manner, covering the protruding outer rib 3d of the cathode holder plate and the insulator block. The filament clamp 9 is positioned on the insulator block 4 and, as mentioned above, is secured by a locking member 11a (e.g., a lock nut), thereby attaching the filament clamp 9 to the assembly. The figure also shows a filament 15 introduced into the opening 3b of the cathode holder plate. A cathode 17 and a shaftless cathode holder 16 are positioned within the opening 3b of the cathode holder plate. The figure also shows a filament strap 10 attached to the filament clamp 9 by a fastening device 13, for example a screw.

[0041] All components of the cathode holder assembly are assembled together along the major longitudinal axis of the hole extending through the protrusion 4a of the insulator block 4, i.e., along the central axis of the hole or fixture 6, respectively. The figure shows that the cathode holder plate, insulator block, and shielding cap are self-aligned along the major longitudinal axis of the fixture 6. Therefore, proper alignment between the components of the cathode assembly is ensured when they are mounted on the arc chamber support. In a preferred embodiment, screws are used to secure the separate components to each other. The number of fasteners required in prior art assemblies can typically be reduced by the design of the cathode holder plate, insulator block, and shielding cap. Therefore, the cathode holder assembly is easy to assemble and typically requires a minimal number of tools.

[0042] FIG. 4A illustrates a cross-sectional view of an embodiment of the claimed arc chamber support assembly, including the claimed cathode holder assembly. In this figure, the cathode holder assembly is attached to the arc chamber support 2. As shown in this figure, the cathode holder plate 3 has a protruding inner rib 3c and a protruding outer rib 3d that extend toward the shielding cap. The protruding inner rib 3c is aligned or registered with the rectangular opening 3a in the cathode holder plate. Furthermore, as shown in this figure, the cathode holder plate has two protruding ribs that extend toward the arc chamber support, and the arc chamber support has an inner rib 2c that extends toward the cathode holder plate and an outer flange 2d, so that the inner ribs 2c and outer flange 2d overlap the protruding ribs of the cathode holder plate. When the arc chamber support assembly is assembled, the protruding portion 4a of the insulator block 4 passes through the opening 3a in the cathode holder plate and into the corresponding recess 2b in the arc chamber support 2. As can be seen from the figure, protrusion 4a of the insulator block fits precisely into recess 2b provided in arc chamber support 2. The arc chamber supports shown in the prior art documents mentioned above were provided with protrusions that slide into the insulator block. However, the prior art documents did not show arc chamber supports with recesses.

[0043] The insulator block 4 has an outer flange 4b, which overlaps the protruding outer rib 3d of the cathode holder plate. The insulator block also has an edge to which the protruding inner rib 3c of the cathode holder plate is attached, so that the protruding portion 4a of the insulator block fits precisely into the opening 3a of the cathode holder plate. The protruding portion of the insulator block has a hole 4d extending over the entire protruding portion of the insulator block. A fastening device 6 is introduced into this hole 4d from the side opposite the cathode holder plate, and the insulator block is fixed to the arc chamber support by a locking member 7, e.g., a locking nut. To enable this, a hole, i.e., a second hole, is provided in the recess of the arc chamber support, and a locking nut is arranged on the side of the arc chamber support.

[0044] The shielding cap 5 is attached to the insulator block by two fastening devices 8, with the shielding cap being attached in a floating manner relative to the insulator block. The shielding cap is provided with a peripheral flange 5a that covers the protruding outer rib 3d of the cathode holding plate.

[0045] In this embodiment, the arc chamber support assembly components self-align when assembled together along the major longitudinal extent of the fixture 6. In the illustrated embodiment, this major longitudinal extent is designated as the x-axis (axial). The arc chamber support assembly components have geometries that allow them to precisely self-align in their fixed positions in the x-, y-, and z-directions. Thus, the claimed cathode retention assembly can be easily attached to the arc chamber support without the need for additional equipment or measuring devices that are typically required to properly position the cathode assembly components within the arc chamber wall opening.

[0046] FIG. 4B shows the same arc chamber support assembly as illustrated in FIG. 4A, but emphasizes one gap and a second gap that are defined when the cathode holder assembly is mounted on the arc chamber support. This gap extends between the cathode holder plate and the shield cap, and further between the cathode holder plate and the insulator block, terminating there. In this embodiment, a side branch is shown between the shield cap and the insulator block. The black lines indicate the plasma / gas flow from the interior of the arc chamber to the exterior of the arc chamber. As shown, the gas or vapor flows along the shield cap, then between the cathode holder plate and the shield cap, and between the cathode holder plate and the insulator block, terminating there. Thus, an extended, serpentine gap for the plasma flow is provided, with seven bends (or turns) and one side branch (as viewed from the shield cap). This extends the time it takes for the entire gap to become covered with plasma, thereby extending the arc chamber's service life. Additionally, FIG. 4B shows an additional gap. This additional gap extends between the cathode retainer plate and the arc chamber support, and then between the arc chamber support and the insulator block, terminating there. In this preferred embodiment, the protrusion of the insulator block has two circumferential grooves, so the second gap extends further into the insulator block, terminating there. In this figure, the extended, serpentine second gap for the plasma flow has seven bends and one side branch. This figure also shows that this gap and the second gap have a gap width of 2 mm or less along their entire length.

[0047] Therefore, the claimed invention provides a cathode holder assembly that, when attached to the arc chamber support of an ion implanter, can improve the life performance of the ion implanter during ion beam operation, thereby reducing the frequency of maintenance shutdowns within the arc chamber.

[0048] The multi-component self-aligning configuration allows for proper placement of the cathode holder assembly without the use of additional instrumentation or measuring devices.

[0049] Below is a brief list of reference numbers and corresponding structures used in the detailed description of the present invention above. [Explanation of symbols]

[0050] 1. Arc chamber 1a Front wall of the arc chamber 2. Arc chamber support (or arc chamber support) 2a Opening in arc chamber support 2b Recess in arc chamber support 2c Inner rib of arc chamber support 2d Outer flange of arc chamber support 3. Cathode holding plate (or cathode holding plate) 3a Rectangular opening in cathode holding plate 3b Circular opening in cathode holding plate 3c Protruding inner rib of cathode support plate towards shielding cap 3d Protruding outer rib on cathode support plate towards shielding cap 4. Insulator block (or insulator block) 4a Protrusion of insulator block toward cathode holding plate 4b Outer flange of insulator block toward cathode retaining plate 4c Edge of insulator block 5 Shielding cap (or shield cap) 5a Shielding cap peripheral flange 5b Holes for fastening the shielding cap device to the insulator block 6 Fixation device, preferably a screw 7. Locking member, preferably a lock nut 8 screws 9 Filament clamp 10 Filament Straps 11 Fixing elements, e.g., square head screws 11a, 14 Locking member, preferably a lock nut 12, 13 Fixing member, preferably a screw 15 filaments 16 Shaftless cathode retainer 17 Cathode

Claims

1. A cathode retaining assembly attached to an arc chamber support of an ion implanter, the cathode retaining assembly including a cathode retaining plate, an insulator block, and a shielding cap; the cathode retaining plate is formed with an opening having a protruding outer rib toward the shielding cap and a protruding inner rib toward the shielding cap; the insulator block is formed with a protrusion configured to pass through the opening in the cathode retainer plate and be inserted into a corresponding recess in the arc chamber support, the protrusion of the insulator block having a through hole formed therein for securing the insulator block to the arc chamber support; the insulator block abuts at its edge against the protruding inner rib of the opening in the cathode holding plate to ensure that the insulator block fits accurately within the opening in the cathode holding plate; the shielding cap is disposed on a side of the insulator block opposite the protrusion to define a gap, the gap extending between the cathode retaining plate and the shielding cap and further between the cathode retaining plate and the insulator block and terminating therein; Cathode retention assembly.

2. 2. The cathode holder assembly of claim 1, wherein the gap has a width of 2 mm or less.

3. 10. The cathode holder assembly of claim 1, wherein the gap follows a tortuous path including at least six bends and at least one side branch.

4. 2. The cathode holder assembly of claim 1, wherein the shielding cap is secured only to the insulator block by at least one fastener extending from the shielding cap into the insulator block.

5. 2. The cathode holder assembly of claim 1, wherein the shielding cap is positioned to cover only the insulator block and the protruding outer rib of the cathode holder plate.

6. 2. The cathode holder assembly of claim 1, wherein each part of the cathode holder assembly is geometrically designed to self-align along an assembly direction when the parts are assembled together.

7. 2. The cathode holder assembly of claim 1, wherein the shielding cap includes a peripheral flange extending toward the cathode holder plate, the protruding outer rib of the cathode holder plate is positioned inside of and overlapped by the peripheral flange, and the insulator block is formed with an outer flange extending toward the cathode holder plate inside of the protruding outer rib.

8. 2. The cathode holder assembly according to claim 1, wherein the cathode holder plate is made of a high melting point metal or a high melting point metal.

9. 1. An arc chamber support assembly for an ion implanter comprising: an arc chamber support; and a cathode holder assembly according to any one of claims 1 to 8 attached to the arc chamber support; an insulator block, wherein the insulator block is attached to the arc chamber support by a fastener extending from the insulator block to the arc chamber support, the fastener passing through a hole in a protrusion of the insulator block and a second hole in a recess of the arc chamber support and fastened to a locking member disposed on a side of the arc chamber support. Arc chamber support assembly.

10. 10. The arc chamber support assembly of claim 9, wherein said fastener is a screw and said locking member is a lock nut.

11. the arc chamber support includes an inner rib toward the cathode retainer plate and an outer flange; 10. The arc chamber support assembly of claim 9, wherein the cathode retainer plate is formed with at least two protruding ribs toward the arc chamber support, the ribs overlapping the inner rib and outer flange of the arc chamber support to define a second gap that extends between and terminates at the cathode retainer plate and the arc chamber support and between the cathode retainer plate and the insulator block.

12. 10. The arc chamber support assembly of claim 9, wherein the protrusion of the insulator block is formed with at least one circumferential groove, and the second gap extends into and terminates in the at least one groove of the insulator block.

13. 10. The arc chamber support assembly of claim 9, wherein the second gap has a width dimension of 2 mm or less.

14. 10. The arc chamber support assembly of claim 9, wherein the second gap defines a tortuous path including at least seven bends.

15. 10. The arc chamber support assembly of claim 9, wherein the shielding cap, the insulator block, the cathode retainer plate, and the arc chamber support are geometrically configured to self-align along a major longitudinal axis of an area of ​​the fastener that extends through the insulator block and the arc chamber support when assembled.

16. 1. An arc chamber assembly for an ion implanter comprising: The arc chamber support assembly of claim 9; an arc chamber disposed on the arc chamber support; 1. An arc chamber assembly comprising:

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