Cathode support and ion source

Abstract

To improve workability during gap adjustment between a filament and a cathode.SOLUTION: A cathode support includes: a cylindrical or rod-like cathode holder 1 supporting a cathode 6 at one end and having a flange 2 at the other end; and clamps 3, 4 and 5 supporting the cathode holder 1. The clamps 3, 4 and 5 include first adjustment surfaces 31, 41 and 51 and second adjustment surfaces 32, 42 and 52 in the axial direction of the cathode holder 1, and the rotation of the cathode holders 1 and 61 around the axis of the cathode holders 1 and 61 and the movement of the cathode holders 1 and 61 in the axial direction allow the arrangement of the flange 2 from the first adjustment surfaces 31, 41 and 51 to the second adjustment surfaces 32, 42 and 52.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cathode support that supports a cathode and an ion source equipped with the same. [Background technology]

[0002] Due to the demand for a longer life for the ion source, an indirectly heated ion source is used. An indirectly heated ion source has a filament and a cathode that is heated by thermions emitted from the filament and emits its own thermions. A dopant gas is introduced into the arc chamber, and plasma is generated from this gas by thermions emitted from the cathode.

[0003] The filament and cathode of an indirectly heated ion source are spaced apart by a predetermined distance, called the gap, which is adjusted during assembly of the ion source. During gap adjustment, the cathode is positioned at two positions in a predetermined direction. First, the cathode is positioned at the first position. Next, the filament is positioned and fixed in position based on the positioned cathode. After that, the cathode is moved from the first position to the second position, and the cathode position is fixed. By fixing the cathode position in this way, a predetermined gap is formed between the cathode and the filament. As an example of gap adjustment, Patent Document 1 proposes using a positioning pin to position the cathode.

[0004] The device disclosed in Patent Document 1 includes a support rod that supports a cathode at one end and a clamp that supports the other end of the support rod. The support rod and the clamp have openings that penetrate both members in a direction perpendicular to the axial direction of the support rod. In the axial direction of the support rod, the opening dimension formed in the support rod is larger than the opening dimension formed in the clamp. Positioning pins having the same dimensions as the openings in the clamp in the axial direction of the support rod are inserted into the openings in the support rod and the clamp, and the support rod is then moved up and down along its axial direction.

[0005] The movement of the support rod is restricted in the axial direction of the support rod at two positions: a lower position where the open end of the support rod abuts against the end of the positioning pin, and an upper position, so the position of the support rod is determined at these positions. Because the cathode is supported on the end of the support rod, positioning the support rod also achieves positioning of the cathode. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent Application Publication No. 2008 / 0072413A1 Summary of the Invention [Problem to be solved by the invention]

[0007] In the configuration of Patent Document 1, the use of a positioning pin is essential for positioning the support rod that supports the cathode during gap adjustment, which makes the gap adjustment work complicated.

[0008] The main object of the present invention is to improve the workability during gap adjustment. [Means for solving the problem]

[0009] The cathode support is a cylindrical or rod-shaped cathode holder that supports a cathode at one end and has a flange at the other end; a clamp for supporting the cathode holder; the clamp has a first adjustment surface and a second adjustment surface in an axial direction of the cathode holder; The collar can be positioned from the first adjustment surface to the second adjustment surface by rotating the cathode holder around its axis and by moving the cathode holder in the axial direction.

[0010] By simply placing the flange of the cathode holder on the first and second adjustment surfaces, it is possible to position the cathode in two positions. Because the flange positioning does not require the positioning pins used in conventional technology, workability during gap adjustment is significantly improved.

[0011] More specifically, The clamp has a step portion between the first adjustment surface and the second adjustment surface, and the step portion faces the flange portion disposed on the second adjustment surface.

[0012] The first adjustment surface is preferably flush with the upper surface of the flange portion disposed on the second adjustment surface.

[0013] When fixing the cathode holder after adjusting the gap, it is easy to check whether the cathode holder is properly positioned.

[0014] It is desirable that the flange portion faces the step portion around the entire circumference of the cathode holder, and that the step portion restricts rotation of the cathode holder around the axis.

[0015] With the above-described configuration, the effect of suppressing displacement of the cathode holder is improved.

[0016] The ion source is configured as follows: An ion source having the cathode support of the above configuration, an arc chamber for generating plasma therein; The arc chamber includes an upper cover having an extraction opening for extracting an ion beam from the plasma; a bottom plate facing the top cover, It is desirable that the step portion faces the flange portion in the opposing direction of the top cover and the bottom plate.

[0017] When assembling the ion source, if the direction from the top lid to the bottom plate is the direction of gravity, and the flange portion and the step portion face each other in the direction in which the top lid and bottom plate face each other, the tilt of the cathode holder due to the weight of the cathode is suppressed by the step portion, making it easy to fix the cathode holder. [Effects of the Invention]

[0018] By simply placing the flange of the cathode holder on the first and second adjustment surfaces, it is possible to position the cathode in two positions. Because the flange positioning does not require the positioning pins used in conventional technology, workability during gap adjustment is significantly improved. [Brief explanation of the drawings]

[0019] [Figure 1] Schematic cross-sectional view for explaining gap adjustment [Figure 2] Plan view showing the clamp configuration [Figure 3] A plan view showing the state when the cathode holder is mounted on the clamp in Figure 2. [Figure 4] A plan view showing the cathode holder of Figure 3 rotated 90 degrees. [Figure 5] Schematic plan view showing the ion source during assembly. [Figure 6] Illustration of the effect of gravity on assembly work [Figure 7] 10 is a plan view of another example of the configuration of the cathode holder and the clamp. [Figure 8] Schematic cross-sectional view for explaining gap adjustment using a rod-shaped cathode holder [Figure 9] FIG. 8(A) is a plan view showing the relationship between the cathode holder and the clamp. [Figure 10] FIG. 8(B) is a plan view showing the relationship between the cathode holder and the clamp. DETAILED DESCRIPTION OF THE INVENTION

[0020] 1 is a schematic cross-sectional view illustrating gap adjustment. In this specification, the direction parallel to the axial direction of a cylindrical or rod-shaped cathode holder 1, 61 (described later) is defined as the Z direction, and the two directions perpendicular to the Z direction are defined as the X direction and the Y direction. The axis refers to the central axis of the cathode holder in the longitudinal direction.

[0021] The cathode 6 is supported at one end of the cylindrical cathode holder 1 by a ring-shaped lock wire 13. As for the support structure of the cathode 6 in the cathode holder 1, in addition to fixation by the lock wire 13 as shown in the figure, other fixing structures such as a conventionally known lock plate or screw fastening may also be employed.

[0022] A flange 2 that protrudes radially outward from the cathode holder 1 is provided at the other end of the cathode holder 1 opposite to the end where the cathode 6 is supported. In the illustrated XY plane, the distance that the flange 2 protrudes from the cathode holder 1 varies depending on the location in the circumferential direction of the cylindrical cathode holder 1.

[0023] A bolt (not shown) is inserted into the first clamp 3 and the second clamp 4 that fix and support the cathode holder 1, and by screwing a nut 9 onto the bolt, the gap between the clamps 3 and 4 is adjusted, thereby fixing and supporting the cathode holder 1.

[0024] The first clamp 3 and the second clamp 4 have first adjustment surfaces 31, 41 and second adjustment surfaces 32, 42. The first adjustment surfaces 31, 41 and the second adjustment surfaces 32, 42 are surfaces that have different heights in the axial direction of the cathode holder 1, and a step portion D is provided between the first adjustment surfaces 31, 41 and the second adjustment surfaces 32, 42. Furthermore, the second adjustment surfaces 32 and 42 are located closer to the location where the cathode holder 1 is supported (the holder insertion opening 71, which will be described later) than the first adjustment surfaces 31 and 41.

[0025] When adjusting the gap between the filament 11 and the cathode 6, as shown in Figure 1(A), the flange portion 2 of the cathode holder 1 is abutted against the first adjustment surfaces 31, 41 of each clamp 3, 4, and the nuts 9 of each clamp 3, 4 are tightened to fix the cathode holder 1. Thereafter, the filament 11 is inserted through the filament insertion port 72 of the cathode holder 1 , and the other end of the filament 11 is fixed by the filament clamp 12 in a state where the tip of the filament 11 abuts against the cathode 6 in the Z direction.

[0026] Various conventionally known configurations can be used for the filament clamp 12. For example, a configuration in which a member that rotates in the XY plane is used to apply a force in the direction of shearing the filament 11 while fixing and supporting the filament 11, or a configuration in which the filament is clamped by an elastically deformable slot structure can be used.

[0027] In the state shown in FIG. 1(A), after the position of the filament 11 is fixed, the nut 9 is loosened and the cathode holder 1 is released from the fixed state. Next, the cathode holder 1 is rotated around its axis and moved axially to position the flange 2 on the second adjustment surfaces 32, 42. After that, the nuts 9 of the clamps 3, 4 are tightened to fix the cathode holder 1. Figure 1(B) shows the state at this point.

[0028] By moving the flange 2 of the cathode holder 1 from the first adjustment surfaces 31, 41 to the second adjustment surfaces 32, 42 of the clamps 3, 4, the gap S between the filament 11 and the cathode 6 shown in the figure is adjusted. The above-described gap adjustment method does not require the positioning pins used in Patent Document 1, and therefore the workability of gap adjustment is significantly improved.

[0029] The configuration of each part will be described in detail below with reference to FIGS. Figure 2 shows a plan view of each of the clamps 3 and 4 with the cathode holder 1 removed. Figure 2(A) shows each of the clamps 3 and 4 in the XY plane, and Figure 2(B) shows each of the clamps 3 and 4 in the ZX plane.

[0030] The clamps 3 and 4 are physically independent members. When the clamps 3 and 4 are joined together, a holder insertion opening 71 for fixing and supporting the cathode holder 1 is formed. A bolt 10 is inserted through each of the clamps 3, 4. By adjusting the tightening or loosening of nuts 9 at each end of the bolt 10, the strength with which the cathode holder 1 is supported by each of the clamps 3, 4 can be adjusted. 1, each clamp 3, 4 has a first adjustment surface 31, 41, a second adjustment surface 32, 42, and a step portion D. Here, the step portion D is a plane parallel to the YZ plane, but depending on the configurations of the first adjustment surface 31, 41 and the second adjustment surface 32, 42, it may be formed as a plane intersecting the YZ plane, or may be formed as a curved surface instead of a flat surface.

[0031] In Figure 2(A), a gap is depicted between the first clamp 3 and the second clamp 4, but this is depicted to make it easier to understand that each clamp is a physically independent separate member, and such a gap is not necessarily required when the two members are assembled. This also applies to the other figures described below.

[0032] 3 and 4 are plan views of the cathode holder 1 attached to the holder insertion opening 71 of Fig. 2. Fig. 3 corresponds to Fig. 1(A), and the planar views of Figs. 3(A) and 3(B) are different. 3, a part of the flange 2 of the cathode holder 1 is placed on the first adjustment surfaces 31, 41 of the clamps 3, 4. In this state, the filament 11 is passed through the filament insertion port 72 of the cathode holder 1 and the tip of the filament 11 is brought into contact with the cathode 6.

[0033] Figure 4 shows the state when, from the state shown in Figure 3, the clamps 3 and 4 are loosened, the cathode holder 1 is rotated 90 degrees around the central axis, and moved in the axial direction, so that the flange portion 2 of the cathode holder 1 is positioned on the second adjustment surfaces 32 and 42 of the clamps 3 and 4. Figure 4 corresponds to Figure 1(B), and the planar views of Figures 4(A) and (B) are different.

[0034] In Figure 4, when the flange portion 2 is placed on the second adjustment surfaces 32, 42, the step portion D facing the flange portion 2 restricts the rotation of the cathode holder 1 in the circumferential direction, and the cathode holder 1 is positioned in the circumferential direction. Similarly, a configuration may be adopted in which protrusions are provided on the first adjustment surfaces 31 and 41 so that the cathode holder 1 can also be positioned in the circumferential direction on the first adjustment surfaces 31 and 41.

[0035] When the flange portion 2 is placed on the second adjustment surfaces 32, 42, if the thickness dimension of the flange portion 2 in the Z direction and the dimension of the step portion D are made the same so that the upper surface of the flange portion 2 (the surface opposite to the surface placed on the second adjustment surfaces 32, 42) and the first adjustment surfaces 31, 41 are on the same plane, it can be easily confirmed that the cathode holder 1 is placed horizontally without tilting.

[0036] 5 shows the ion source IS during assembly. An ion extraction opening 21c is formed in the top lid 21a of arc chamber 21, which has a rectangular parallelepiped outer shape, for extracting an ion beam from plasma generated in the arc chamber. A gas inlet pipe (not shown) for introducing gas into arc chamber 21 is connected to bottom plate 21b facing top lid 21a. In addition, a housing 24 attached below arc chamber 21 is provided with a refrigerant flow path for flowing a refrigerant to cool arc chamber 21, a vaporizer for discharging vapor into arc chamber 21, and the like.

[0037] Ion sources used in ion implantation systems come in a variety of sizes depending on the size of the ion beam extracted from the ion source. An ion source that extracts an ion beam smaller than the wafer diameter is known as a relatively small ion source. As shown in FIG. 5, this type of ion source is assembled using a flange 25 for fixing the ion source unit to the ion implantation system body and a handle 26 for carrying the ion source unit as a base. When assembling the ion source, the direction of gravity G is downward in the figure. In terms of the configuration of the ion source IS, the direction of gravity G is parallel to the opposing direction of the top cover 21a and the bottom plate 21b.

[0038] Cathode holder 1, which supports cathode 6, is inserted into arc chamber 21 from one end face of arc chamber 21. Also, a reflecting electrode 27 is provided in arc chamber 21 opposite cathode holder 1. Instead of this reflecting electrode 27, two cathode holders 1 may be provided and arranged in the arc chamber 21 so as to face each other.

[0039] The cathode holder 1 is fixed and supported by the second clamp 4 described above and the first clamp 3 (not shown), and the filament 11 inserted into the cathode holder 1 is supported by a filament clamp 12. In addition, insulating members are provided between members that require electrical insulation. If the weight of the cathode 6 supported at one end of the cathode holder 1 causes the cathode holder 1 to tilt in the direction of the arrow T, there is a concern that the cathode holder 1 may be fixed in an obliquely tilted position when it is fixed after the gap adjustment.

[0040] In the configuration of Figure 6(A), there is no member to restrict movement of the flange portion 2 in the direction of gravity G, and as described above, when the cathode holder 1 is fixed, the cathode holder 1 may tilt significantly, which may hinder the work of fixing the cathode holder 1. On the other hand, in the configuration of Figure 6(B), the flange portion 2 and the step portion D face each other in the direction of gravity G, so tilting of the cathode holder 1 is somewhat suppressed compared to the configuration of Figure 6(A), making the work of fixing the cathode holder 1 easier.

[0041] The flange portion 2, the first adjustment surfaces 31, 41, the second adjustment surfaces 32, 42, and the step portion D may have various configurations other than those described above, such as those shown in FIG. 7(A) to 7(D) are plan views of the flange portion 2 when it is disposed on the second adjustment surfaces 32 and 42. FIG. In Fig. 7(A), the flange 2 has a special sawtooth shape. In Fig. 7(B), a portion of the flange 2 is disposed outside each of the clamps 3 and 4. In Fig. 7(C), the flange 2 is provided partially in the circumferential direction of the cathode holder 1. In Fig. 7(D), the flange 2 faces a step D all around the circumference of the cathode holder 1, and the step D restricts rotation of the cathode holder 1 around its axis.

[0042] In either configuration, the flange portion 2 can be positioned from the first adjustment surface 31, 41 to the second adjustment surface 32, 42 by rotating the cathode holder 1 around its axis and moving the cathode holder 1 in the axial direction, so that gap adjustment work can be performed without using positioning pins, as in the embodiment described in Figures 1 to 4.

[0043] The cathode holder 1 rotates around its axis at an appropriate angle depending on the shapes of the flange 2, first adjustment surfaces 31 and 41, and second adjustment surfaces 32 and 42. For example, in the configuration of FIG. 7(C), the rotation angle of the cathode holder 1 may be set in the range of approximately 30 degrees to approximately 150 degrees. In addition, in the configuration of FIG. 7(D), considering that the flange 2 is disposed on the first adjustment surfaces 31 and 41, the optimum rotation angle of the cathode holder 1 is approximately 45 degrees.

[0044] In order to prevent the cathode holder 1 from tilting due to the influence of gravity as described in FIG. 5, it is desirable that the area of ​​the step D facing the flange 2 is large. In this regard, if the flange portion 2 is configured to face the step portion D around the entire circumference of the cathode holder 1, as shown in Figure 7(D), this will have a high effect in suppressing the cathode holder 1 from shifting out of position, and will effectively prevent the cathode holder 1 from being fixed in the wrong position when fixing the cathode holder 1 after adjusting the gap.

[0045] 7(D), four protruding portions of the flange 2 are provided in the radial direction of the cathode holder 1, but in practicing the present invention, two or more protruding portions are sufficient. Furthermore, considering the stability when the flange 2 is disposed on the first adjustment surfaces 31 and 41, it is desirable that the number of protruding portions of the flange 2 be three or more, and that they be evenly arranged in the circumferential direction of the cathode holder 1.

[0046] In the embodiments described above, the cathode holder 1 is assumed to be a cylindrical member, but the shape of the cathode holder 1 is not limited to this. For example, the cathode holder 1 may be a rectangular cylindrical member or a member with a notch in part of the cylinder. Moreover, instead of a cylindrical member, a rod-shaped member may be used as the cathode holder, as in Patent Document 1.

[0047] An example of a configuration in which a rod-shaped member is used as the cathode holder will be described with reference to FIGS. FIG. 8(A) is a schematic cross-sectional view showing the state when the filament 11 is positioned, and the plan views of FIG. 9(A) and FIG. 9(B) correspond to this. FIG. 8B is a schematic cross-sectional view showing the state after the gap adjustment, and the plan views of FIGS. 10A and 10B correspond to this. The cathode holder 61 is a rod-shaped member that is long in one direction, and supports the cathode 6 at one end by screwing or press-fitting, and has a flange portion 2 at the other end.

[0048] When adjusting the gap between the filament 11 and the cathode 6, the cathode holder 61 is rotated around its axis and moved in the axial direction to position the flange portion 2 from the first adjustment surface 51 to the second adjustment surface 52, which is the same as the embodiment of the cylindrical cathode holder 1.

[0049] 8 to 10, the clamp configuration is changed because a rod-shaped cathode holder 61 with a smaller diameter than the cylindrical cathode holder 1 is used. This clamp 5 has an elastically deformable slot structure that clamps the filament.

[0050] Even with the rod-shaped cathode holder 61 shown in the embodiment of Figures 8 to 10, it is possible to position the cathode 6 without using a positioning pin, just like the cylindrical cathode holder 1 shown in the embodiment of Figures 1 to 7.

[0051] The cathode support may include a cylindrical or rod-shaped cathode holder that supports the cathode at one end and has a flange at the other end, and a clamp that supports the cathode holder, and other additional components may be added as appropriate. Furthermore, the other end of the cathode holder is not limited to the very end of the cathode holder, but also includes an end that is shifted from the very end in the axial direction. In this respect, the flange is not necessarily provided at the very end of the cathode holder.

[0052] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0053] IS ion source 1, 61 Cathode holder 2. Tsuba 3 First Clamp 4 Second Clamp 5 Third Clamp 6 cathode 11 filaments 31, 41, 51 First adjustment surface 32, 42, 52 Second adjustment surface D Step part G Gravity direction

Claims

1. a cylindrical or rod-shaped cathode holder that supports a cathode at one end and has a flange at the other end; a clamp for supporting the cathode holder; the clamp has a first adjustment surface and a second adjustment surface in an axial direction of the cathode holder; the cathode holder is rotated around its axis and moved in its axial direction, thereby enabling the flange to be positioned from the first adjustment surface to the second adjustment surface; the clamp has a step portion between the first adjustment surface and the second adjustment surface, The cathode support restricts rotation of the cathode holder around the axis by sandwiching the flange portion disposed on the second adjustment surface between the stepped portion and the flange portion.

2. The cathode support of claim 1 , wherein the first adjustment surface is flush with an upper surface of the collar portion disposed on the second adjustment surface.

3. 3. The cathode support according to claim 1, wherein the flange faces the step over the entire circumference of the cathode holder, and the step restricts rotation of the cathode holder around its axis.

4. An ion source having the cathode support according to any one of claims 1 to 3, an arc chamber for generating plasma therein; The arc chamber includes an upper cover having an extraction opening for extracting an ion beam from the plasma; a bottom plate facing the top cover, The step portion faces the flange portion in a direction in which the top cover and the bottom plate face each other.

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