Fasteners for fixing the faceplate to the ion source

Abstract

A fastener for securing a faceplate to the chamber wall of an ion source is disclosed. The ion source is mounted on a source housing having a flange. The fastener includes two straps having a cross-section resembling a rounded rectangle. Each strap has two mounting and engaging portions that abut the outer surface of the faceplate. The mounting portions pass through an opening in the flange and are attached to a tension system located on the opposite side of the flange. The tension system includes at least one spring associated with each strap, which presses the faceplate against the top of the chamber wall. The shape of the straps reduces electrostatic stress between the faceplate and the extraction electrodes located near the faceplate.

Description

Technical Field

[0001] This application claims priority to U.S. Patent Application No. 18 / 144,367, filed May 8, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0002] Embodiments of the present disclosure relate to fasteners for fixing a faceplate to an ion source.

Background Art

[0003] The manufacture of semiconductor devices involves multiple distinct and complex processes. One such process may utilize an ion beam that can be extracted from an ion source. In an ion source, a supply gas is excited to form ions. These ions are then extracted from the ion source through extraction apertures disposed on a faceplate. The ions are manipulated downstream by various components including electrodes, acceleration and deceleration stages, and mass analyzers.

[0004] One such ion source is a cathode ion source that is indirectly heated. An indirectly heated cathode (IHC) ion source operates by supplying current to a filament disposed behind the cathode. The filament emits thermionic electrons that are accelerated towards the cathode through an applied potential, heating the cathode and emitting electrons into the arc chamber of the ion source. The cathode is disposed at one end of the arc chamber. A repeller may be disposed at the end of the arc chamber opposite the cathode. The cathode and repeller may be biased to repel the electrons and return them towards the center of the arc chamber. In some embodiments, a magnetic field is used to further confine the electrons within the arc chamber. A plurality of sides are used to connect the two ends of the arc chamber.

[0005] The extraction apertures are disposed along one of these sides called the faceplate. The extraction apertures are disposed near the center of the arc chamber, and ions generated within the arc chamber may be extracted through this center.

[0006] Typically, the faceplate is a separate component from the rest of the arc chamber. Therefore, it is fixed to the arc chamber. However, conventional means of fixing the faceplate create areas of high electrostatic stress, which can cause arc discharge in nearby components such as the extraction electrode.

[0007] Therefore, fasteners that can be used to secure the faceplate to the arc chamber would be beneficial, as they reduce the risk of electrostatic stress and arc discharge. [Overview of the Initiative]

[0008] A fastener for securing a faceplate to the chamber wall of an ion source is disclosed. The ion source is mounted on a source housing having a flange. The fastener includes two straps having a cross-section resembling a rounded rectangle. Each strap has two mounting and engaging portions that abut the outer surface of the faceplate. The rounded portions are located between the engaging portions and each mounting portion. The mounting portions pass through an opening in the flange and are attached to a tension system located on the opposite side of the flange. The tension system includes at least one spring associated with each strap, which presses the faceplate against the top of the chamber wall. The shape of the straps reduces electrostatic stress between the faceplate and the extraction electrodes located near the faceplate.

[0009] According to one embodiment, an ion implantation system is disclosed. The ion implantation system comprises an arc chamber having a plurality of chamber walls and having a first end and a second end; a faceplate having extraction openings positioned on the upper part of the plurality of chamber walls; a source housing having a flange; a faceplate having a first strap positioned near the first end and the second end and having two mounting portions that pass through each opening of the flange; and an ion source having a faceplate having an engaging portion positioned between the two mounting portions. In some embodiments, the faceplate has two grooves positioned on its outer surface, and the first strap and the second strap are positioned in the respective grooves. In some embodiments, the tension system comprises at least one spring associated with each strap. In a particular embodiment, the tension system comprises a retaining block mounted on the distal end of each of the two mounting portions of each strap, and a spring positioned between the underside of the flange and the retaining block. In certain embodiments, the tension system comprises a yoke attached to two attachment points of each strap, the yoke having two arms connecting to each attachment point and to a central portion located between the two arms, and a spring positioned between the lower side of the flange and the central portion of the yoke. In certain embodiments, the tension system further comprises an upper fastener attached to the source housing below the flange and above the central portion of the yoke, a lower fastener positioned below the upper fastener and below the central portion of the yoke, and a post positioned between the upper and lower fasteners, the post being located inside the spring and passing through a hole in the central portion. In certain embodiments, the tension system further comprises guide rails positioned on both sides of the post, the guide rails extending from the upper fastener to the lower fastener and passing through the respective holes in the central portion. In some embodiments, the source housing has a cylindrical shape with a flat region formed on the source housing, to which the upper and lower fasteners are fixed.In some embodiments, each strap includes a rounded portion between the engaging portion and each attachment portion. In certain embodiments, the radius of curvature of the rounded portion is between 0.25 inches and 1.0 inches. In some embodiments, the cross-section of each strap includes a rounded rectangle having width and thickness, and the side defining the thickness has a radius of curvature equal to half the thickness.

[0010] According to another embodiment, an assembly for use in an ion source is disclosed, which comprises an arc chamber having a plurality of chamber walls. The assembly comprises a faceplate adapted to be positioned on top of the plurality of chamber walls, the faceplate having two grooves on its outer surface, and a first strap and a second strap, each having two rounded portions, an engaging portion positioned between the two rounded portions, and two mounting portions, the engaging portion of each strap being positioned within each groove. In some embodiments, the assembly comprises a tension system associated with each strap such that the first strap and the second strap exert a compressive force on the faceplate. In certain embodiments, the tension system comprises a retaining block mounted on the distal end of each of the two mounting portions of each strap, and a spring, the distal ends of the two mounting portions passing through the center of the spring. In certain embodiments, the tension system comprises a yoke attached to each of the two attachment points of each strap, the yoke comprising two arms, each connecting to the respective attachment point, and a central portion located between the two arms, and a spring is positioned to bias the central portion of the yoke away from the faceplate. In certain embodiments, the radius of curvature of the rounded portion is between 0.25 inches and 1.0 inches. In some embodiments, the cross-section of each strap comprises a rounded rectangle having width and thickness, and the side defining the thickness has a radius of curvature equal to half the thickness.

[0011] To better understand this disclosure, refer to the attached drawings. These drawings are incorporated herein by reference. [Brief explanation of the drawing]

[0012] [Figure 1] This is a diagram of an ion source according to one embodiment. [Figure 2] This is a side view of the inside of the ion source in Figure 1. [Figure 3] This is a diagram of one of the straps. [Figure 4] This shows the interface between the faceplate and the strap. [Figure 5A-5B] A tension system for a strap according to one embodiment is shown. [Figure 6] A strap tensioning system according to another embodiment is shown. [Figure 7] Figure 6 shows a source housing for use in the tension system. [Modes for carrying out the invention]

[0013] As mentioned above, the means used to secure the faceplate to the arc chamber may generate undesirable amounts of electrostatic stress, potentially increasing the risk of arc discharge.

[0014] Figure 1 shows a top view of an ion source having an improved fastener for securing a faceplate according to one embodiment. The ion source 10 includes a plurality of chamber walls 11 defining an arc chamber 200. A faceplate 40 having extraction openings 41 may be positioned in contact with the chamber walls 11. The faceplate 40 may be a single component or may consist of multiple components. For example, in one embodiment, the faceplate 40 includes a faceplate insert positioned below an outer side plate and helping to define the extraction openings 41. Thus, the term “faceplate” as used in this disclosure refers to any component or component that constitutes a structure including extraction openings 41 from which ions are removed. Within the arc chamber 200, there may be a mechanism for generating ions. For example, in one embodiment, an indirectly heated cathode (IHC) may be positioned within the arc chamber 200.

[0015] The faceplate 40 is secured to the source housing 30 using a plurality of straps 50. The source housing 30 may include a flange 31 having holes or slots through which the straps 50 pass. The straps 50 are held in place using a tension system. The arc chamber 200 may be positioned on or attached to the source housing 30. In certain embodiments, the source housing 30 may be temperature-controlled. For example, the source housing 30 may be attached to a heat sink or may be the heat sink itself. Thus, the chamber wall 11 is in direct thermal contact with the source housing 30. This may help to cool the chamber wall 11.

[0016] Figure 2 shows an electronic and internal side view of an ion source 10 according to one embodiment. In this embodiment, the ion source 10 includes an arc chamber 200 having two opposing ends and chamber walls 11 connected to these ends. The arc chamber 200 also includes a bottom wall and a faceplate 40. The chamber walls 11 may be made of an electrically and thermally conductive material and may be electrically connected to each other. A cathode 210 is located inside the arc chamber 200 at a first end 201 of the arc chamber 200. A filament 260 is located behind the cathode 210. The filament 260 is in communication with a filament power supply 265. The filament power supply 265 is configured to pass an electric current through the filament 260 so that the filament 260 emits thermionic electrons. The cathode bias power supply 215 negatively biases the filament 260 with respect to the cathode 210, so that these thermionic electrons are accelerated from the filament 260 toward the cathode 210, and when these thermionic electrons strike the back surface of the cathode 210, they heat the cathode 210. The cathode bias power supply 215 can bias the filament 260 to have a voltage between 200V and 1500V negative to the voltage of the cathode 210. The cathode 210 then releases the thermionic electrons on its front surface into the arc chamber 200.

[0017] As a result, the filament power supply 265 supplies current to the filament 260. The cathode bias power supply 215 biases the filament 260 to be negative compared to the cathode 210, so that electrons are attracted from the filament 260 towards the cathode 210. Furthermore, the cathode power supply 270 can be used to electrically bias the cathode 210 relative to the arc chamber 200.

[0018] In this embodiment, the repeller 220 is located within the arc chamber 200 on the second end 202 of the arc chamber 200 opposite the cathode 210. The repeller 220 can communicate with a repeller power supply 225. As the name suggests, the repeller 220 plays a role in repelling electrons emitted from the cathode 210 toward the center of the arc chamber 200. For example, the repeller 220 may be biased with a negative voltage relative to the arc chamber 200 to repel electrons. For example, the repeller power supply 225 may have an output in the range of 0 to -150V, but other voltages may be used. In certain embodiments, the repeller 220 is biased between 0 and -150V relative to the arc chamber 200. In other embodiments, the cathode power supply 270 is also used to supply voltage to the repeller 220. In other embodiments, the repeller 220 may be electrically grounded or floating.

[0019] During operation, gas is supplied to the arc chamber 200. Thermionic electrons emitted from the cathode 210 cause the gas to form a plasma 250. Ions from this plasma 250 are then extracted through extraction openings 41 in the faceplate 40. The ions are then manipulated to form an ion beam directed toward the workpiece. An extraction electrode 280 is positioned outside the arc chamber 200 and near the extraction openings 41. The extraction electrode 280 is biased with a voltage different from that of the arc chamber 200 to attract ions from inside the arc chamber 200 through the extraction openings 41.

[0020] Note that other mechanisms for generating ions may also be used. These other mechanisms include, but are not limited to, Bernas ion sources, RF antennas, and capacitive coupling sources.

[0021] Thus, in some embodiments as shown in FIG. 1, there is a first strap located near the first end 201 of the arc chamber 200 and a second strap located near the second end 202 of the arc chamber 200. The two straps serve to fix the faceplate 40 to the chamber wall 11 of the arc chamber.

[0022] FIG. 3 shows a perspective view of one of the straps 50. Note that the arc chamber 200 can be held in place using two straps 50 that can be identical in size and structure.

[0023] Figure 4 shows a cross-section of a strap 50 attached to a faceplate 40. The strap 50 may be made of tungsten, but other suitable materials may be used. The strap 50 may be formed to have a rounded rectangular cross-section. The cross-section of the strap 50 has a width 51 and a thickness 52, where the width 51 may be greater than the thickness 52. The width 51 of the strap 50 may be between 0.25 inches and 1 inch, while the thickness 52 may be between 1 / 16 and 1 / 4 inch. The ends of the rectangular cross-section defining the thickness 52 are rounded with a diameter equal to the thickness 52 of the strap 50. As is best seen in Figure 3, the strap 50 includes three straight sections separated by a rounded section 53. The rounded section 53 may include a curved section with a radius of curvature. The bend may be a 90° bend, but bends between 45° and 135° may also be used. The radius of curvature of the rounded portion 53 may be between 0.25 inches and 1.0 inch. Between the rounded portions 53 are engagement portions 55. As shown in Figure 1, the engagement portions 55 of the strap 50 are the portions that are placed against the outer surface of the faceplate 40, and the surface of the faceplate 40 is closest to the extraction electrode 280. In some embodiments, the length of the engagement portions 55 is slightly longer than the width of the faceplate 40 so that the engagement portions 55 contact the entire width of the faceplate 40. For example, the engagement portions 55 of the strap 50 may be 1 to 6 inches, but other dimensions are also possible. On the opposite side of each rounded portion 53 is a mounting portion 54. The mounting portion 54 may have a length greater than the height of the arc chamber 200. For example, the mounting portion 54 may have a length of 4 to 10 inches, but other dimensions are also possible. As is best seen in Figure 1, the mounting portion 54 of the strap 50 passes through a slot 32 or opening in the flange 31. At least one hole 56 may be located near the distal end of each attachment portion 54. This hole 56 may be used to attach the strap 50 to the tension system.

[0024] FIG. 4 also shows a groove 42 disposed on the outer surface of the faceplate 40. The groove 42 is disposed, for example, near the first end 201 and the second end 202 of the arc chamber 200 and on two opposite sides of the extraction aperture 41. The groove 42 may be formed in a direction perpendicular to the larger dimension of the extraction aperture 41. The groove 42 may have a width slightly larger than the width 51 of the strap 50. For example, the groove 42 may be wider than the strap 50 by 0.1 inches or less. Further, the groove 42 may have a depth of up to 0.025 inches, although other depths may be used. The engaging portion 55 of the strap 50 is placed within this groove 42.

[0025] As described above, the mounting portion 54 of the strap 50 passes through the slot 32 of the flange 31. The tensioning system is disposed on the side of the flange 31 opposite the arc chamber 200. The tensioning system may include a spring used to apply pressure to the strap 50 and press the faceplate 40 against the upper portion of the chamber wall 11. The tensioning system may be constructed in a plurality of ways. For example, the tensioning system may be configured such that one spring is associated with each mounting portion 54. In another embodiment, the tensioning system may be configured such that one spring is associated with each strap 50.

[0026] Figures 5A-5B show a first embodiment of the tension system. In this embodiment, a spring 500 is used for each mounting portion 54 of each strap 50. As is best seen in Figure 5B, a screw 511 or other fastener can pass through a hole 56 in the mounting portion 54 and hold the retaining block 510. The spring 500 is positioned between the underside of the flange 31 and the retaining block 510. The spring 500 applies a downward force to the retaining block 510, thereby tightening the strap 50 against the faceplate 40. The distance between the underside of the flange 31 and the retaining block 510 is shorter than the free length of the spring 500 to ensure a downward force on the faceplate 40. This distance can be modified to achieve a desired compressive force on the faceplate 40. For example, in one embodiment, there may be multiple holes 56 in the mounting portion 54 of each strap 50, such that the holes 56 used to connect the strap 50 to the retaining block 510 determine the compressive force. In some embodiments, the washer 520 may be positioned between the underside of the flange 31 and the spring 500. The washer 520 may be made of aluminum oxide (alumina) or another suitable material.

[0027] Figure 6 shows a second embodiment of the tensioning system. In this embodiment, one spring is used for each strap 50. The two ends of the attachment portion 54 of each strap 50 are connected to the yoke 600, for example, through the use of screws or other fasteners 610. The yoke 600 may include two arms 601 extending toward the attachment portion 54 of the strap 50. Furthermore, the yoke 600 may include a central portion 602 connecting the two arms 601. A spring 630 is positioned between the flange 31 and the central portion 602. In some embodiments, the central portion 602 may include one or more holes for accommodating a guide rail 640. The central portion 602 may also include another hole for accommodating a post passing between an upper fastener 620 and a lower fastener 625. In some embodiments, the upper fastener 620 is secured to the source housing 30 below the flange 31 and above the yoke 600. The lower fastener 625 is attached to the source housing 30 below the yoke 600. A post may be positioned between the upper fastener 620 and the lower fastener 625. The spring 630 may be positioned such that the post passes through the center of the spring 630. The first end of the spring 630 contacts the underside of the upper fastener 620, and the second end of the spring 630 contacts the central portion 602 of the yoke 600. The distance between the underside of the upper fastener 620 and the central portion 602 of the yoke 600 is shorter than the free length of the spring 630, ensuring a downward force on the faceplate 40. This distance can be modified to achieve a desired compressive force on the faceplate 40, based on the mounting position of the upper fastener or the length of the arm 601 of the yoke 600. For example, in one embodiment, there may be multiple holes 56 in the mounting portion 54 of each strap 50, so that the holes 56 used to connect the strap 50 to the arm 601 determine the compressive force. In addition, guide rails 640 may be positioned between the upper fastener 620 and the lower fastener 625 and pass through the holes in the central portion 602. These guide rails 640 provide stability. The spring 630 applies a downward force to the central portion 602 of the yoke 600, which then causes the arm 601 to pull the mounting portion 54 of the strap 50 downward, pressing the strap 50 against the faceplate 40.

[0028] Figure 7 shows the source housing 30 of Figure 6 in more detail. As described above, the source housing 30 has a flange 31 located on or near the top surface. The flange 31 has a number of openings or slots 32 through which the straps 50 pass. In certain embodiments, there may be a total of four slots 32. The bottom of the source housing 30 may include a lower flange 33. The source housing 30 includes a housing body 34 defined as the region between the flange 31 and the lower flange 33. In certain embodiments, the interior of the housing body 34 may be hollow to allow for the inclusion of components. The exterior of the housing body 34 may be cylindrical. Two regions located on opposite sides of the housing body 34 may be machined to form a flat surface 36. The flat surface 36 creates a place where each tension system can be mounted. The flat surface 36 may have a width ranging from 1 to 3 inches and a height ranging from 2 to 5 inches, but other dimensions are possible.

[0029] The embodiments described herein may have numerous advantages. In one simulation, the strap 50 described herein is compared to a conventional hook used to hold a faceplate. The hook is fixed in a pocket located on the outer surface of the faceplate. Due to the configuration of these hooks, they may have bends greater than 90° and radii of curvature less than 0.2 inches. Electrostatic stress simulations were performed for both designs. In the simulation, it was assumed that the extraction electrode was positioned 1 inch away from the faceplate 40 and biased with a voltage 30 kV lower than the voltage of the faceplate 40. Because the hook has a small radius of curvature near the faceplate, a localized area of ​​high electrostatic stress is generated. In contrast, the strap design increases the radius of curvature. It was found that the maximum electrostatic stress of the strap 50 described herein was reduced by at least 15%. This reduction in electrostatic stress reduces the risk of arc discharge between the strap and the extraction electrode, which may result in improved throughput and increased system availability.

[0030] Furthermore, the embodiment in Figure 6 offers additional advantages. By using one spring per strap 50, possible variations in faceplate tension can be reduced in several ways. First, the springs shown in Figure 6 are further from the arc chamber 200 than the springs in Figures 5A and 5B. This reduces the thermal load on the springs, potentially lowering the likelihood of variations in the spring constant due to thermal expansion / contraction. Additionally, one spring is used per fastener, rather than two. Each spring has a manufactured tolerance. Suppose the two springs associated with one fastener are manufactured at the upper limit of the tolerance, and the two springs associated with the other strap are manufactured at the lower limit of the tolerance. In this scenario, there is a difference between the two ends. On the other hand, if there is only one spring on the side, this maximum difference is only half the difference that occurs with four springs.

[0031] This disclosure should not be limited in scope by the specific embodiments described herein. In fact, a person skilled in the art will see from the above description and accompanying drawings that, in addition to the embodiments and modifications to this disclosure, a variety of other embodiments and modifications not described herein will be obvious. Thus, such other embodiments and modifications are also intended to be within the scope of this disclosure. Furthermore, while this disclosure has been described herein in relation to a specific implementation in a specific environment for a specific purpose, a person skilled in the art will recognize that the usefulness of this disclosure is not limited thereto, and that this disclosure can be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims described below should be interpreted in light of the entire scope and essence of this disclosure as described herein.

Claims

1. An ion implantation system, It is an ion source, An arc chamber comprising multiple chamber walls and having a first end and a second end, and A faceplate having extraction openings is positioned on the upper part of the plurality of chamber walls. An ion source containing, A source housing having a flange, wherein the arc chamber is positioned on top of the source housing, A first strap located near the first end and a second strap located near the second end, wherein each strap has two attachment portions that pass through the respective openings of the flange, and an engagement portion positioned between the two attachment portions and in contact with the outer surface of the faceplate, A tension system located on the opposite side of the flange from the ion source, wherein the tension system applies pressure to press the first strap and the second strap against the faceplate in order to secure the faceplate to the arc chamber. An ion implantation system equipped with the following features.

2. The ion implantation system according to claim 1, wherein the faceplate has two grooves located on its outer surface, and the first strap and the second strap are each positioned in the corresponding grooves.

3. The ion implantation system according to claim 1, wherein the tension system includes at least one spring associated with each strap.

4. The ion implantation system according to claim 3, wherein the tension system includes a retaining block attached to the distal end of each of the two attachment portions of each strap, and a spring positioned between the lower side of the flange and the retaining block.

5. The ion implantation system according to claim 3, wherein the tension system includes a yoke attached to the two attachment portions of each strap, the yoke including two arms connected to the respective attachment portions and a central portion located between the two arms, and a spring is positioned between the lower side of the flange and the central portion of the yoke.

6. The tension system, An upper fastener fixed to the source housing below the flange and above the central portion of the yoke, A lower fastener positioned below the upper fastener and below the central portion of the yoke, A post positioned between the upper fastener and the lower fastener, which is positioned inside the spring and passes through the hole in the central portion. The ion implantation system according to claim 5, further comprising:

7. The ion implantation system according to claim 6, wherein the tension system further includes guide rails positioned on both sides of the post, the guide rails extending from the upper fastener to the lower fastener and passing through each of the holes in the central portion.

8. The ion implantation system according to claim 6, wherein the source housing has a cylindrical shape, a flat region is formed on the source housing, and the upper fastener and the lower fastener are fixed to the flat region.

9. The ion implantation system according to claim 1, wherein each strap includes a rounded portion between the engaging portion and each attachment portion.

10. The ion implantation system according to claim 9, wherein the radius of curvature of the rounded portion is between 0.25 and 1.0 inches.

11. The ion implantation system according to claim 1, wherein the cross-section of each strap includes a rounded rectangle having width and thickness, and the side defining the thickness has a radius of curvature equal to half the thickness.

12. An assembly for use in an ion source, wherein the ion source includes an arc chamber having a plurality of chamber walls, and the assembly is A faceplate adapted to be positioned on the upper part of the plurality of chamber walls, the faceplate having two grooves on its outer surface, A first strap and a second strap, each having two rounded portions, an engaging portion positioned between the two rounded portions, and two attachment portions, wherein the engaging portion of each strap is configured to be positioned within its respective groove. An assembly comprising:

13. The assembly according to claim 12, further comprising a tensioning system associated with each strap such that the first strap and the second strap apply compressive force to the faceplate.

14. The assembly according to claim 13, wherein the tension system includes a retaining block attached to the distal end of each of the two attachment portions of each strap, and a spring, the distal end of each of the two attachment portions passing through the center of the spring.

15. The assembly according to claim 13, wherein the tensioning system includes a yoke attached to each of the two attachment portions of each strap, the yoke including two arms, each connected to the respective attachment portion, and a central portion located between the two arms, and a spring is arranged to bias the central portion of the yoke away from the faceplate.

16. The assembly according to claim 12, wherein the radii of curvature of the two rounded portions are between 0.25 inches and 1.0 inch.

17. The assembly according to claim 12, wherein the cross-section of each strap includes a rounded rectangle having width and thickness, and the side defining the thickness has a radius of curvature equal to half the thickness.

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