Dose cup combination for ion implanter

Abstract

A dose cup assembly that induces less particles in a process chamber is disclosed. The dose cup assembly includes a panel attached to a back wall of a process chamber and having an opening; a perforated plate defining a plurality of slots; and a tunnel having a plurality of walls and a plurality of sidewalls and having a proximal end and a distal end located between the panel and the perforated plate such that the proximal end is closer to the panel and the distal end is closer to the perforated plate; wherein at least one of the panel, the plurality of walls, the plurality of sidewalls, or the perforated plate has one or more exposed outer surfaces comprising silicon. The exposed outer surface may be silicon. In some embodiments, the panel, the plurality of walls, the plurality of side walls, or the perforated plate may be graphite coated with silicon or silicon carbide, aluminum, or stainless steel.

Description

[0001] This application claims priority to U.S. patent application serial number 18 / 101,260, filed on January 25, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] The present disclosure describes embodiments of a dosage cup assembly for measuring ion beam current in an ion implanter. Background Art

[0003] Semiconductor devices are manufactured using a variety of processes, some of which involve implanting ions into a workpiece. Some implanters have the capability to monitor the ion beam directed toward the workpiece. The incident ion beam is typically very narrow in height but has a width greater than the diameter of the workpiece. This width can be achieved using a ribbon ion beam or by scanning a point ion beam.

[0004] To monitor the incident ion beam, one or more current sensors (which may be Faraday cups or other sensors) may be positioned in the process chamber. These current sensors may be positioned so that the ion beam strikes the current sensors when the workpiece is not in an operating position. The current sensors may then be used to measure the incident beam current as a function of position in the width direction. In some embodiments, multiple current sensors are arranged in the width direction. In another embodiment, a single current sensor that is movable in the width direction is used.

[0005] The ion beam is aligned and directed toward the current sensor using a structure called a dose cup assembly. Due to the location of the current sensor, the dose cup assembly, which protects the current sensor, is exposed to the ion beam. This exposure can cause a film to form on the dose cup assembly, which can interfere with the operation of the current sensor. This film can be fragile, making it susceptible to rupture. Consequently, particles can form in the process chamber due to rupture of this film. Particles can increase the frequency of preventive maintenance (PM) routines, thereby reducing the overall throughput of the ion implanter.

[0006] Therefore, it would be beneficial to have a dose cup assembly that is more resistant to the buildup of this film. Alternatively, it may be advantageous to expose the dose cup assembly to an ion beam, thereby forming a different type of film that is less susceptible to rupture. Summary of the Invention

[0007] An ion implanter is disclosed, comprising: an ion source for generating an ion beam; a platen disposed in a process chamber to support a workpiece treated with the ion beam; and a dose cup assembly for generating fewer particles in the process chamber. The dose cup assembly comprises: a faceplate attached to a rear wall of the process chamber, the faceplate defining an opening; an aperture plate defining a plurality of slots; and a tunnel having a plurality of walls and a plurality of sidewalls and having a proximal end and a distal end, the tunnel being located between the faceplate and the aperture plate, with the proximal end being closer to the faceplate and the distal end being closer to the aperture plate; and one or more current sensors disposed behind the slots in the aperture plate so that the ion beam passes through the slots to reach the one or more current sensors. At least one of the faceplate, the walls, the sidewalls, or the aperture plate has one or more exposed outer surfaces comprising silicon. The exposed outer surfaces may be silicon. In some embodiments, the faceplate, the walls, the sidewalls, or the aperture plate may be graphite, aluminum, or stainless steel coated with silicon or silicon carbide. In some embodiments, the panel, the walls, the sidewalls, and the aperture plate all have one or more exposed outer surfaces comprising silicon. In some embodiments, the one or more exposed outer surfaces comprise silicon. In some embodiments, the one or more exposed outer surfaces include a coating composed of silicon or silicon carbide. In certain embodiments, the underlying substrate beneath the coating comprises graphite, aluminum, or stainless steel. In some embodiments, the walls of the tunnel are parallel to one another and are made of silicon or coated with silicon or silicon carbide. In some embodiments, the spacing between the walls of the tunnel is greater at the proximal end than at the distal end, so as to taper inward toward the aperture plate. In some embodiments, the spacing between the sidewalls of the tunnel is less at the proximal end than at the distal end, so as to taper outward toward the aperture plate. In some embodiments, the aperture plate includes a front support member and a rear slotted member, wherein the front support member is made of silicon or coated with silicon or silicon carbide. In certain embodiments, the front support member is permanently joined to the rear slotted member. In certain embodiments, the front support member is mechanically coupled to the rear slotted member.

[0008] In another embodiment, a dose cup assembly configured to be disposed in a process chamber of an ion implanter is disclosed. The dose cup assembly includes: a faceplate configured to be attached to a rear wall of the process chamber of the ion implanter, the faceplate defining an opening; an aperture plate defining a plurality of slots; and a tunnel having a plurality of walls and a plurality of sidewalls and having a proximal end and a distal end, the tunnel being positioned between the faceplate and the aperture plate such that the proximal end is closer to the faceplate and the distal end is closer to the aperture plate; wherein at least one of the faceplate, the plurality of walls, the plurality of sidewalls, or the aperture plate has one or more exposed outer surfaces comprising silicon. In some embodiments, the faceplate, the plurality of walls, the plurality of sidewalls, and the aperture plate all have the one or more exposed outer surfaces comprising silicon. In some embodiments, the one or more exposed outer surfaces comprise silicon. In some embodiments, the one or more exposed outer surfaces comprise a coating composed of silicon or silicon carbide. In certain embodiments, an underlying substrate beneath the coating comprises graphite, aluminum, or stainless steel. In some embodiments, the spacing between the multiple walls of the tunnel is greater at the proximal end than the spacing between the multiple walls of the tunnel at the distal end, so as to taper inwardly toward the perforated plate. In some embodiments, the spacing between the multiple side walls of the tunnel is less at the proximal end than the spacing between the multiple side walls of the tunnel at the distal end, so as to taper outwardly toward the perforated plate. In some embodiments, the perforated plate includes a front support member and a rear slotted member, wherein the front support member is made of silicon or coated with silicon or silicon carbide. In certain embodiments, the front support member is permanently joined to the rear slotted member. In certain embodiments, the front support member is mechanically connected to the rear slotted member.

[0009] According to another embodiment, a system for measuring beam current of an ion beam is disclosed, comprising: the dose cup assembly described above; and one or more current sensors disposed behind the plurality of slots in an aperture plate, wherein the ion beam is adapted to pass through the plurality of slots to reach the one or more current sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a better understanding of the present disclosure, reference is made to the accompanying drawings, in which like numerals are used to refer to like elements and in which:

[0011] Figure 1 is a block of an ion implanter using a dose cup assembly according to one embodiment.

[0012] Figure 2 is a block diagram of a process chamber with a dose cup assembly and a current sensor.

[0013] Figure 3A The dose cup assembly is shown.

[0014] Figure 3B The components that make up the dose cup assembly are shown.

[0015] Figure 4 An aperture plate is shown for use as part of a dose cup assembly according to one embodiment.

[0016] Figures 5A-5B Two embodiments of tunnels for use as part of a dose cup assembly are shown. DETAILED DESCRIPTION

[0017] Figure 1 An ion implanter including a process chamber 100 and a dose cup assembly 10 is shown. An ion source 200 is used to generate an ion beam 250. The ion source 200 may be an indirectly heated cathode (IHC) ion source. Alternatively, the ion source 200 may be a capacitively coupled plasma source, an inductively coupled plasma source, a Bernas source, or other sources. Therefore, the type of ion source is not limited by the present disclosure. An extraction optical device 205 is disposed outside and adjacent to an extraction aperture of the ion source 200. The extraction optical device 205 may include one or more electrodes.

[0018] The mass analyzer 210 is located downstream of the extraction optics 205. The mass analyzer 210 uses a magnetic field to guide the path of the extracted ion beam. The magnetic field affects the flight path of the ions according to their mass and charge. A mass resolving device 220 having a resolving aperture 221 is provided at the output or distal end of the mass analyzer 210. By appropriately selecting the magnetic field, only those ions in the ion beam 250 having a selected mass and charge will be guided through the resolving aperture 221. Other ions will impact the walls of the mass resolving device 220 or the mass analyzer 210 and will not travel further in the system.

[0019] Collimator 230 may be positioned downstream of mass-resolving device 220. Collimator 230 receives ions from ion beam 250 that pass through resolving aperture 221 and forms an ion beam consisting of a plurality of parallel or nearly parallel beamlets. The output, or distal end, of mass analyzer 210 and the input, or proximal end, of collimator 230 may be spaced a fixed distance apart. Mass-resolving device 220 is positioned in the space between these two components.

[0020] The acceleration / deceleration stage 240 may be located downstream of the collimator 230. The acceleration / deceleration stage 240 is a beamline lens assembly configured to independently control the deflection, deceleration, and focusing of the ion beam. For example, the acceleration / deceleration stage 240 may be an electrostatic filter (EF). After exiting the acceleration / deceleration stage 240, the ion beam 250 enters the process chamber 100.

[0021] The process chamber 100 includes a platen 110 on which a workpiece 112 may be disposed. When in an operating position, an ion beam 250 impinges on the workpiece 112. Additionally, a dose cup assembly 10 is disposed at a rear wall 101 of the process chamber 100. One or more current sensors 120 may be positioned behind the dose cup assembly 10.

[0022] Controller 280 can communicate with one or more of the power supplies to monitor and / or modify the voltage or current supplied by the power supplies. Controller 280 can include a processing unit, such as a microcontroller, a personal computer, a dedicated controller, or other suitable processing unit. Controller 280 can also include a non-transitory storage element, such as a semiconductor memory, a magnetic storage device, or another suitable memory. Such non-transitory storage element can contain instructions and other data that enable controller 280 to perform the functions described herein.

[0023] In some embodiments, the ion source 200 may generate a ribbon beam that travels through the components. Of course, other ion implanters may also be used. For example, an ion implanter may generate a scanned ion beam rather than a ribbon beam. Such an ion implanter includes an ion source that forms a point beam. As described above, this type of ion implanter also includes a mass analyzer and a mass resolving device. In addition, a scanner (which may be electrostatic or other types) is used to form the scanned ion beam. The scanned ion beam may pass through an angle corrector. The angle corrector is designed to deflect the ions in the scanned ion beam to produce an ion beam with parallel ion trajectories, thereby focusing the scanned ion beam. Specifically, the angle corrector is used to change the diverging ion trajectory path into a substantially parallel path of the ion beam 250. In some embodiments, the angle corrector may include magnetic pole pieces spaced apart to define a gap and a magnetic coil coupled to a power supply. The scanned ion beam passes through the gap between the magnetic pole pieces and is deflected according to the magnetic field in the gap. In other embodiments, the angle corrector may be an electrostatic lens, sometimes referred to as a parallelizing lens.

[0024] Figure 2 Shown in more detail Figure 1The process chamber 100 is shown. The process chamber 100 includes one or more current sensors 120. The dose cup assembly 10 is disposed between the incident ion beam 250 and the current sensor 120. A platen 110 is also disposed in the process chamber 100. The platen 110 can be an electrostatic platen for clamping and holding a workpiece 112 while directing the ion beam 250 into the process chamber 100. In some embodiments, the platen 110 can be raised and lowered in the Y direction 118 by movement of the axis 115. In addition, the platen 110 can be rotated about the X axis 111. In some embodiments, the platen 110 can be rotated 90° so that the clamping surface of the platen 110 is horizontal, thereby allowing the workpiece 112 to be placed on the platen 110. The platen 110 is then rotated to an operating position or an implantation position, such as Figure 2 As shown in .

[0025] To monitor the ion beam 250, the platen 110 is lowered by actuating the axis 115 in the Y direction 118. This movement removes the platen 110 from the path of the ion beam 250. Thus, the ion beam 250 is unobstructed as it travels toward the current sensor 120. As described in more detail below, the dose cup assembly 10 is used to direct the ion beam 250 and align the ion beam 250 with the current sensor 120.

[0026] Figure 3A Shown in Figure 2 A diagram of a dosing cup assembly 10 for use in a process chamber 100 is shown. Figure 3B An exploded view of the dosing cup assembly 10 showing the individual components is shown. The dosing cup assembly 10 includes a panel 20. As shown in Figure 2 As seen in FIG, faceplate 20 is attached to rear wall 101 of process chamber 100 and covers the gap between rear wall 101 and tunnel 30. Faceplate 20 defines openings 21 that allow ions to pass through and reach current sensor 120.

[0027] Tunnel 30 extends rearward from face plate 20. The term "rearward" refers to a direction in the direction of ion beam 250 and away from the source of ion beam 250. In some embodiments, proximal end 31 of tunnel 30 contacts rear surface 22 of face plate 20. In other embodiments, a gap may exist between proximal end 31 of tunnel 30 and rear surface 22 of face plate 20.

[0028] An aperture plate 40 is coupled to the tunnel 30. The aperture plate 40 defines a plurality of slots 41 through which ions can pass. In some embodiments, the slots 41 may be between 2 inches and 6 inches in height and between 1 / 16 inch and 1 / 4 inch in width. A bracket 35 may be used to secure the tunnel 30 to the aperture plate 40. In some embodiments, the aperture plate 40 contacts the distal end 32 of the tunnel 30. In other embodiments, there may be a gap between the aperture plate 40 and the distal end 32. In one embodiment, seven current sensors 120 are disposed behind seven corresponding slots 41. Of course, other numbers of slots and current sensors may also be utilized. In another embodiment, one current sensor 120 is used that translates across the width of the ion beam 250 to collect current from each slot 41.

[0029] Thus, tunnel 30 is positioned between panel 20 and aperture plate 40, with proximal end 31 of tunnel 30 closer to rear surface 22 of panel 20 and distal end 32 of tunnel closer to aperture plate 40. In some embodiments, proximal end 31 may contact or be attached to rear surface 22 of panel 20. In some embodiments, distal end 32 may contact a portion of aperture plate 40. In some embodiments, tunnel 30 is attached to aperture plate 40 using bracket 35.

[0030] Each component will be described in more detail. The aperture plate 40 may have a thickness between 0.25 inches and 0.75 inches and, in some embodiments, may be made from a single piece of silicon. This single piece of silicon may be crystalline silicon or polycrystalline silicon. In another embodiment, the aperture plate 40 may be constructed from graphite, aluminum, or stainless steel and then coated with silicon or silicon carbide. The coating may have a thickness between 50 micrometers (μm) and 100 μm.

[0031] exist Figure 4 In another embodiment shown in , the perforated plate 40 is made of multiple parts. The front support member 42 includes an opening 43 that is wider and longer than the slot 41, so as not to block the slot 41. This front support member 42 is used to provide structural integrity. The rear slotted member 44 includes a slot 41. The combined thickness of the front support member 42 and the rear slotted member 44 can be between 0.25 inches and 0.75 inches. In one embodiment, the rear surface of the front support member 42 is permanently bonded to the front surface of the rear slotted member 44. This can be done using indium bonding. In another embodiment, fasteners are used to mechanically connect the two components. In some embodiments, the front support member 42 and the rear slotted member 44 can be made of silicon (which can be crystalline silicon or polycrystalline silicon). Alternatively, as described above, the components can be made of graphite, aluminum, or stainless steel coated with silicon or silicon carbide. In another embodiment, the front support member 42 is made of silicon or coated with silicon or silicon carbide, and the rear slotted member 44 is graphite.

[0032] In one embodiment, Figure 3B As shown in FIG, tunnel 30 includes a set of parallel walls 33a and 33b. Tunnel 30 also includes a set of parallel sidewalls 34a and 34b. Walls 33a, 33b, and sidewalls 34a and 34b extend a distance of between 4 inches and 8 inches from proximal end 31 to distal end 32. Walls 33a and 33b may have a length of between 12 inches and 17 inches in width. Sidewalls 34a and 34b may have a length of between 2 inches and 6 inches in height. The thickness of the walls and sidewalls may be approximately 1 inch. In some embodiments, walls 33a, 33b, and sidewalls 34a and 34b are made of silicon (which may be crystalline silicon or polycrystalline silicon). In other embodiments, as described above, walls 33a, 33b, and sidewalls 34a and 34b may be made of graphite, aluminum, or stainless steel coated with silicon or silicon carbide.

[0033] Other embodiments are also possible. Figure 5A A second embodiment of tunnel 30 is shown. In this second embodiment of tunnel 30, walls 33a and 33b are closer together at distal end 32 than at proximal end 31. In other words, walls 33a and 33b taper inwardly toward perforated plate 40. In certain embodiments, sidewalls 34a and 34b also taper inwardly toward perforated plate 40. In some embodiments, the spacing between walls 33a and 33b at proximal end 31 is at least one inch greater than the spacing between walls 33a and 33b at distal end 32. In some embodiments, the spacing between walls 33a and 33b at proximal end 31 can be more than two inches greater than the spacing at distal end 32. Similarly, in some embodiments, the spacing between sidewalls 34a and 34b at proximal end 31 is at least one inch greater than the spacing between sidewalls 34a and 34b at distal end 32. In some embodiments, the distance between the side walls 34 a , 34 b at the proximal end 31 may be more than 3 inches greater than the distance at the distal end 32 .

[0034] Figure 5B A third embodiment of the tunnel 30 is shown. In this third embodiment of the tunnel 30, the sidewalls 34a and 34b are further apart from each other at the distal end 32 than at the proximal end 31. In other words, the sidewalls 34a and 34b taper outwardly toward the aperture plate 40. In some embodiments, the spacing between the sidewalls 34a and 34b at the proximal end 31 is at least one inch smaller than the spacing between the sidewalls 34a and 34b at the distal end 32. In some embodiments, the spacing between the sidewalls 34a and 34b at the proximal end 31 can be at least three inches smaller than the spacing at the distal end 32.

[0035] exist Figure 3B and Figures 5A-5BIn the embodiment shown in , walls 33a, 33b and sidewalls 34a, 34b may be made of silicon (which may be crystalline silicon or polycrystalline silicon). Alternatively, as described above, walls 33a, 33b and sidewalls 34a, 34b may be made of graphite, aluminum, or stainless steel coated with silicon or silicon carbide.

[0036] Finally, the dose cup assembly includes a panel 20. As described above, the panel 20 defines an opening 21. The size of the opening can be approximately the same as the size of the perimeter formed by walls 33a, 33b and sidewalls 34a, 34b at the proximal end 31. In this way, the opening 21 is aligned with the proximal end of the tunnel 30. Therefore, depending on which embodiment of the tunnel 30 is used, the size of the opening 21 can vary. The thickness of the panel 20 can be between 0.25 inches and 1 inch. The panel 20 can be composed of silicon, which can be crystalline silicon or polycrystalline silicon. In other embodiments, the panel 20 can be coated with silicon or silicon carbide. In these embodiments, the panel can be graphite or a metal (e.g., aluminum or stainless steel).

[0037] Thus, in some embodiments, at least one of the components making up the dosing cup assembly has one or more exposed outer surfaces comprising silicon. These exposed outer surfaces can be pure silicon or can be a silicon-containing compound (e.g., silicon carbide). In some embodiments, the exposed outer surface is a coating composed of silicon or silicon carbide and the underlying substrate is graphite, aluminum, or stainless steel. In some embodiments, all of the components making up the dosing cup assembly have one or more exposed outer surfaces comprising silicon.

[0038] The present system and method have numerous advantages. In certain current configurations, species from the ion beam may react with materials used to form components of the dosing cup assembly. For example, boron ions may react with graphite components to form a film composed of boron carbide. This film may break down, forming particles. The formation of such a boron carbide film can be reduced or minimized by redesigning one or more of the components of the dosing cup assembly to have an outer surface comprising silicon.

[0039] In addition, changing the geometry of tunnel 30 can have additional beneficial effects. When the walls are parallel to each other, low-energy ion beams (e.g., boron or phosphorus) can impact the walls at a grazing angle, causing a deposited layer that may flake off. Changing the geometry of tunnel 30 can address this problem. For example, if tunnel 30 tapers outward toward aperture plate 40, the number of ions that may impact walls 33a, 33b and sidewalls 34a, 34b is reduced. Since fewer ions will impact the walls and sidewalls of tunnel 30, the likelihood of forming an unwanted film is reduced. Alternatively, if tunnel 30 tapers inward toward aperture plate 40, the angle at which ions impact the walls and sidewalls is increased. By increasing the angle of incidence, ions are more likely to sputter material from the walls, thereby reducing the likelihood of unwanted film deposition.

[0040] The scope of the present disclosure is not limited by the specific embodiments described herein. In fact, upon reading the above description and the accompanying drawings, various other embodiments of the present disclosure and various modifications to the present disclosure in addition to the embodiments and modifications described herein will also be apparent to those skilled in the art. Therefore, such other embodiments and modifications are intended to fall within the scope of the present disclosure. In addition, although the present disclosure has been described herein in the context of specific embodiments for specific purposes and in specific environments, those skilled in the art will recognize that the utility of the present disclosure is not limited thereto, but rather can be beneficially implemented in any number of environments for any number of purposes. Therefore, the scope of the claims set forth below should be understood in light of the full scope and spirit of the present disclosure as described herein.

Claims

1. An ion implanter comprising: an ion source for generating an ion beam; a platen for supporting a workpiece to be treated with the ion beam, the platen being positioned within a process chamber of the ion implanter; Dosing cup assembly, including: a face plate attached to a rear wall of a process chamber of the ion implanter, the face plate defining an opening; an apertured plate defining a plurality of slots; and a tunnel having a plurality of walls and a plurality of sidewalls and having a proximal end and a distal end, located between the face plate and the aperture plate such that the proximal end is closer to the face plate and the distal end is closer to the aperture plate; and one or more current sensors disposed behind the plurality of slots in the aperture plate, wherein the ion beam passes through the plurality of slots to reach the one or more current sensors; Wherein at least one of the face plate, the plurality of walls, the plurality of sidewalls, or the aperture plate has one or more exposed exterior surfaces comprising silicon.

2. The ion implanter of claim 1 , wherein the face plate, the walls, the sidewalls, and the aperture plate each have one or more exposed exterior surfaces comprising silicon.

3. The ion implanter of claim 1 , wherein the one or more exposed exterior surfaces comprise silicon.

4. The ion implanter of claim 1 , wherein the one or more exposed exterior surfaces comprises a coating comprised of silicon or silicon carbide.

5. The ion implanter of claim 4, wherein an underlying substrate beneath the coating comprises graphite, aluminum, or stainless steel.

6. The ion implanter of claim 1, wherein the walls of the tunnel are parallel to each other and are made of silicon or coated with silicon or silicon carbide.

7. The ion implanter of claim 1, wherein a spacing between the plurality of walls of the tunnel is greater at the proximal end than the spacing between the plurality of walls of the tunnel at the distal end so as to taper inwardly toward the aperture plate.

8. The ion implanter of claim 1, wherein a spacing between the plurality of side walls of the tunnel is smaller at the proximal end than the spacing between the plurality of side walls of the tunnel at the distal end to taper outwardly toward the aperture plate.

9. The ion implanter of claim 1, wherein the aperture plate comprises a front support member and a rear slotted member, wherein the front support member is made of silicon or coated with silicon or silicon carbide.

10. The ion implanter of claim 9, wherein the front support member is permanently joined to the rear slotted member.

11. The ion implanter of claim 9, wherein the front support member is mechanically coupled to the rear slotted member.

12. A dose cup assembly configured to be disposed in a process chamber of an ion implanter, comprising: a face plate configured to be attached to a rear wall of the process chamber of the ion implanter, the face plate defining an opening; an apertured plate defining a plurality of slots; as well as a tunnel having a plurality of walls and a plurality of sidewalls and having a proximal end and a distal end, positioned between the face plate and the aperture plate such that the proximal end is closer to the face plate and the distal end is closer to the aperture plate; Wherein at least one of the face plate, the plurality of walls, the plurality of sidewalls, or the aperture plate has one or more exposed exterior surfaces comprising silicon.

13. The dosing cup assembly of claim 12, wherein the face plate, the plurality of walls, the plurality of sidewalls, and the aperture plate each have one or more exposed exterior surfaces comprising silicon.

14. The dosage cup assembly of claim 12, wherein the one or more exposed exterior surfaces comprise silicon.

15. The dosage cup assembly of claim 12, wherein the one or more exposed exterior surfaces comprises a coating comprised of silicon or silicon carbide.

16. The dosing cup assembly of claim 15, wherein the underlying substrate beneath the coating comprises graphite, aluminum, or stainless steel.

17. The dosing cup assembly of claim 12, wherein a spacing between the plurality of walls of the tunnel is greater at the proximal end than the spacing between the plurality of walls of the tunnel at the distal end to taper inwardly toward the aperture plate.

18. The dosing cup assembly of claim 12, wherein a spacing between the plurality of side walls of the tunnel is smaller at the proximal end than the spacing between the plurality of side walls of the tunnel at the distal end to taper outwardly toward the aperture plate.

19. The dose cup assembly of claim 12, wherein the aperture plate comprises a front support member and a rear slotted member, wherein the front support member is made of silicon or coated with silicon or silicon carbide.

20. A system for measuring beam current of an ion beam, comprising: The dosing cup assembly of claim 12; as well as One or more current sensors are disposed behind the plurality of slots in the aperture plate, wherein the ion beam is adapted to pass through the plurality of slots to reach the one or more current sensors.

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