Apparatus for controlling the uniformity of an extracted ion beam

Abstract

An ion source capable of extracting a ribbon ion beam with improved uniformity is disclosed. One of the walls of the ion source has a protrusion on its inner surface facing the chamber. The protrusion creates a loss area that acts as a sink for free electrons and ions. This reduces the plasma density near the protrusion, and by modifying the beam current near the protrusion, the uniformity of the ribbon ion beam extracted from the ion source can be improved. The shape of the protrusion may be modified to achieve the desired uniformity. The protrusion may also be utilized in cylindrical ion sources. In certain embodiments, the protrusion is formed by mechanically adjustable protrusion elements.

Description

Technical Field

[0001] This application claims the benefit of U.S. Patent Application No. 17 / 473,101, filed Sep. 13, 2021, the disclosure of which is hereby incorporated by reference in its entirety.

[0002] This disclosure describes a system for controlling the uniformity of a ribbon ion beam extracted from an ion source (such as an indirectly heated cathode (IHC) ion source).

Background Art

[0003] Semiconductor devices are manufactured using multiple processes. Some of those processes involve implanting ions into a workpiece. Various ion sources can be used to generate the ions. One such mechanism is an indirectly heated cathode (IHC) ion source. The IHC ion source includes a filament disposed behind a cathode. The cathode can be maintained at a positive voltage relative to the filament. Passing a current through the filament emits thermoelectrons from the filament, and those thermoelectrons are accelerated toward the more positively charged cathode. These thermoelectrons help heat the cathode, which then emits electrons into the ion source chamber. The cathode is disposed at one end of the chamber. A repeller is typically disposed at the end of the chamber opposite the cathode.

[0004] In certain embodiments, the IHC ion source is configured to extract a ribbon ion beam. The width of the ribbon ion beam is much larger than its height. Unfortunately, in many systems, the beam current of the extracted ribbon ion beam is not uniform along its width. This non-uniformity can cause the concentration of ions implanted into the workpiece to be non-uniform. In other embodiments, additional components within the beamline, such as quadrupole lenses, may be utilized in an attempt to compensate for this non-uniformity. These measures can add additional complexity and cost to the beamline system.

[0005] Therefore, it would be beneficial to have a system that can control the uniformity of the ribbon ion beam being extracted from the ion source. SUMMARY OF THE INVENTION

[0006] An ion source is disclosed that can extract a ribbon ion beam with improved uniformity. One of the walls of the ion source has a protrusion on its inner surface facing the chamber. The protrusion creates a loss area that functions as a sink for free electrons and ions. This reduces the plasma density near the protrusion, and by changing the beam current near the protrusion, the uniformity of the ribbon ion beam extracted from the ion source can be improved. The shape of the protrusion may be changed to achieve the desired uniformity. The protrusion may also be used in a cylindrical ion source. In certain embodiments, the protrusion is formed by a plurality of mechanically adjustable protrusion elements.

[0007] According to one embodiment, an ion source is disclosed. The ion source includes a chamber having a first end, a second end, and a plurality of walls connecting the first end and the second end. One of the plurality of walls is an extraction plate having an extraction opening with a width greater than its height. The ion source further includes a plasma generator for generating plasma within the chamber. One of the plurality of walls different from the extraction plate is a protruding wall having a protrusion extending towards the interior of the chamber. In some embodiments, the protrusion extends into the chamber at least 3 mm at at least one location. In certain embodiments, the protrusion has a constant radius of curvature from the first end to the second end. In some embodiments, the protrusion has a triangular shape. In some embodiments, the protrusion has a trapezoidal shape. In some embodiments, the protruding wall faces the extraction plate. In certain embodiments, the protruding wall is adjacent to the extraction plate. In some embodiments, the plasma generator includes an indirectly heated cathode disposed at the first end.

[0008] According to another embodiment, an ion source is disclosed. The ion source includes a chamber having a first end, a second end, and a cylindrical housing connecting the first end and the second end. An extraction opening having a width greater than its height is disposed in the cylindrical housing. The ion source further includes a plasma generator for generating plasma in the chamber. A protrusion extends from the cylindrical housing into the interior of the chamber. In some embodiments, the protrusion is disposed in the cylindrical housing opposite the extraction opening such that it is offset 180° from the extraction opening. In some embodiments, the protrusion is offset 90° from the extraction opening. In certain embodiments, the plasma generator includes an indirectly heated cathode disposed at the first end. In some embodiments, the maximum thickness of the protrusion occurs at the center of the extraction opening in the width direction.

[0009] According to another embodiment, an ion source is disclosed. The ion source includes a chamber having a first end, a second end, and a plurality of walls connecting the first end and the second end. One of the plurality of walls is an extraction plate having an extraction opening with a width greater than its height. The ion source further includes a plasma generator for generating plasma in the chamber and a plurality of mechanically adjustable protrusion elements electrically connected to the plurality of walls and extending into the interior of the chamber. In some embodiments, the ion source includes an actuator for controlling the position of the plurality of mechanically adjustable protrusion elements within the chamber. In certain embodiments, each of the plurality of mechanically adjustable protrusion elements is independently controlled. In some embodiments, the plurality of mechanically adjustable protrusion elements extend through the wall opposite the extraction plate. In certain embodiments, the plurality of mechanically adjustable protrusion elements extend through the wall adjacent to the extraction plate. In some embodiments, the plasma generator includes an indirectly heated cathode disposed at the first end.

[0010] To better understand the present disclosure, reference is made to the accompanying drawings. In the accompanying drawings, like elements are referred to using like numerals.

Brief Description of the Drawings

[0011]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 4E

Figure 5A

Figure 5B

Figure 6

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0012] Figures 1A - 1B show an IHC ion source 10 that can be utilized to extract a ribbon ion beam with improved uniformity according to two embodiments. Figures 2A - 2B show cross - sectional views of the HC ion source 10 of Figures 1A - 1B respectively. In these embodiments, the IHC ion source 10 includes a chamber 100 with two opposing ends and a wall 101 connecting these ends. These walls 101 include side walls, namely, an extraction plate 103 and a bottom wall opposing the extraction plate 103. The extraction plate 103 includes an extraction opening 140 through which ions are extracted. The extraction opening 140 may be considerably larger in the width direction (also referred to as the X - direction) than in the height direction (also referred to as the Y - direction). The Z - direction is defined along the thickness of the extraction plate 103 and is defined as the movement direction of the ribbon ion beam. For example, the extraction opening 140 may be larger than 2 inches in the width direction and smaller than 0.5 inches in the height direction.

[0013] The walls 101 of the chamber 100 may be constructed of a conductive material (such as tungsten or another high - melting - point metal) and may be electrically connected to each other. A cathode 110 is disposed within the chamber 100 at a first end 104 of the chamber 100. A filament 160 is disposed behind the cathode 110. The filament 160 is in communication with a filament power supply 165. The filament power supply 165 is configured to pass a current through the filament 160. Thereby, the filament 160 emits thermoelectrons. A cathode bias power supply 115 biases the filament 160 negatively with respect to the cathode 110. Thus, these thermoelectrons are accelerated from the filament 160 towards the cathode 110, and when these thermoelectrons hit the back surface of the cathode 110, the cathode 110 is heated. The cathode bias power supply 115 may bias the filament 160 to have a voltage, for example, between - 200V and - 1500V relative to the voltage of the cathode 110. Then, the cathode 110 emits thermoelectrons into the chamber 100 from its front surface.

[0014] Therefore, the filament power supply 165 supplies current to the filament 160. The cathode bias power supply 115 biases the filament 160. Thereby, the filament 160 becomes more negative than the cathode 110. As a result, electrons are attracted from the filament 160 toward the cathode 110. The cathode 110 communicates with the arc voltage power supply 111. The arc voltage power supply 111 supplies voltage to the cathode with respect to the chamber 100. This arc voltage accelerates the thermoelectrons emitted at the cathode into the chamber 100 to ionize the neutral gas. The current drawn by this arc voltage power supply 111 is a measured value of the amount of current driven through the plasma. In certain embodiments, the wall 101 serves as the ground reference for other power supplies.

[0015] In this embodiment, the reflective electrode 120 is disposed within the chamber 100 at the second end 105 of the chamber 100 facing the cathode 110. The center of the cathode 110 and the center of the reflective electrode 120 may form two points on the central axis 109 of the chamber 100.

[0016] The reflective electrode 120 may be in electrical communication with the reflective electrode power supply 123. As its name indicates, the reflective electrode 120 serves to repel the electrons emitted from the cathode 110 toward the center of the chamber 100. For example, in certain embodiments, the reflective electrode 120 may be biased to a negative voltage with respect to the chamber 100 to repel electrons. For example, in certain embodiments, the reflective electrode 120 is biased between 0 and -150 V with respect to the chamber 100. In certain embodiments, the reflective electrode 120 may be floating with respect to the chamber 100. In other words, when in a floating state, the reflective electrode 120 is not electrically connected to either the reflective electrode power supply 123 or the chamber 100. In this embodiment, the voltage of the reflective electrode 120 tends to drift to a voltage close to the voltage of the cathode 110. Alternatively, the reflective electrode 120 may be electrically connected to the wall 101.

[0017] In certain embodiments, a magnetic field 190 is generated within the chamber 100. This magnetic field is intended to confine electrons along one direction. The magnetic field 190 typically passes parallel to the wall 101 from the first end 104 to the second end 105. For example, the electrons may be confined within a column parallel to the direction from the cathode 110 to the reflecting electrode 120 (i.e., the X direction). Thus, the electrons do not receive an electromagnetic force moving in the X direction. However, the movement of electrons in other directions may be subject to electromagnetic forces.

[0018] One or more gas containers 108 may communicate with the chamber 100 via the gas inlet 106. Each gas container 108 may include a mass flow controller (MFC) to regulate the gas flow from each gas container.

[0019] The extraction power supply 170 can be used to bias the wall 101 of the IHC ion source 10 with respect to the remaining components within the beamline. For example, the platen 260 (see FIG. 2) may be at a first voltage such as ground, while a positive voltage is applied to the IHC ion source 10 so that the IHC ion source 10 is biased more positively than the platen 260. Thus, the voltage supplied by the extraction power supply 170, called the extraction voltage, determines the energy of the ions extracted from the IHC ion source 10. Further, the current supplied by the extraction power supply 170 serves as a measure of the total extraction beam current.

[0020] In certain embodiments, there is a feedback loop between the cathode bias power supply 115 and the extraction power supply 170. Specifically, it may be desirable to maintain the extraction beam current at a constant value. Thus, the current supplied by the extraction power supply 170 may be monitored, and the output of the cathode bias power supply 115 can be adjusted to maintain a constant extraction current. This feedback loop may be executed by the controller 180 or in another manner.

[0021] Controller 180 may be in communication with one or more of the power supplies. Thereby, the voltage or current supplied by these power supplies may be monitored and / or corrected. Further, controller 180 may be in communication with the MFCs of each gas container 108 to regulate the flow of each gas into chamber 100. Controller 180 may include a processing unit such as a microcontroller, a personal computer, a dedicated controller, or another suitable processing unit. Controller 180 may also include a non-transitory storage element such as a semiconductor memory, a magnetic memory, or another suitable memory. This non-transitory storage element may contain instruction commands and other data that enable controller 180 to perform the functions described herein. For example, controller 180 may be in communication with cathode bias power supply 115 to enable the IHC ion source 10 to vary the voltage applied to the filament 160 as a cathode. Controller 180 may also be in communication with reflector electrode power supply 123 to bias the reflector electrode. Further, controller 180 can monitor the voltage, current, and / or power supplied by cathode bias power supply 115.

[0022] FIG. 3 shows an ion implantation system using the IHC ion source 10 of FIG. 1A. One or more electrodes 200 are disposed outside and in the vicinity of the extraction aperture of the IHC ion source 10.

[0023] Downstream from the electrode 200, a mass spectrometer 210 is arranged. The mass spectrometer 210 uses a magnetic field to direct the path of the extracted ribbon ion beam 1. 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 arranged at the output (i.e., distal end) of the mass spectrometer 210. By appropriately selecting the magnetic field, only those ions in the ribbon ion beam 1 having the selected mass and charge will be directed through the resolving aperture 221. Other ions will collide with the walls of the mass resolving device 220 or the mass spectrometer 210 and will not be able to move further within the system.

[0024] A collimator 230 may be arranged downstream from the mass resolving device 220. The collimator 230 receives ions from the ribbon ion beam 1 that has passed through the resolving aperture 221 and generates a ribbon ion beam formed from a plurality of parallel or substantially parallel beamlets. The output (i.e., distal end) of the mass spectrometer 210 and the input (i.e., proximal end) of the collimator 230 may be spaced apart by a certain distance. The mass resolving device 220 is arranged in the space between these two components.

[0025] Downstream from the collimator 230, an acceleration / deceleration stage 240 may be arranged. The acceleration / deceleration stage 240 may be referred to as an energy purity module. The energy purity module is a beamline lens component configured to independently control the deflection, deceleration, and focusing of the ion beam. For example, the energy purity module may be a vertical electrostatic energy filter (VEEF) or an electrostatic filter (EF). Downstream from the acceleration / deceleration stage 240, a platen 260 is arranged. A workpiece is arranged on the platen 260 during processing.

[0026] Referring back to FIGS. 1A-1B and FIGS. 2A-2B, chamber 100 includes at least one wall 101 having a protrusion 150. The protrusion 150 extends inwardly from an inner surface facing the chamber 100. This wall having the protrusion 150 may be referred to as the protruding wall 151. In other words, the protrusion 150 changes the thickness of the protruding wall 151. In certain embodiments, as shown in FIGS. 1A and 2A, the protruding wall 151 is the bottom wall facing the extraction plate 103. In other embodiments, as shown in FIGS. 1B and 2B, the protruding wall 151 is adjacent to the extraction plate 103.

[0027] When the protruding wall 151 is as shown in FIGS. 1A and 2A, the protrusion 150 extends in the Z direction. When the protruding wall 151 is as shown in FIGS. 1B and 2B, the protrusion 150 extends in the Y or -Y direction.

[0028] In any embodiment, the protrusion 150 increases the loss area within the chamber 100. In particular, the protrusion 150 is conductive, is electrically connected to the wall 101, and functions as a sink for free electrons and ions. This loss area serves to reduce the plasma density proximate to the protrusion 150.

[0029] In some embodiments, the maximum extent of the protrusion 150 occurs at the center of the extraction opening. As used herein, the term "center of the extraction opening" refers to the center of the extraction opening in the X (i.e., width) direction. Further, FIGS. 1A-1B show that the maximum thickness of the protrusion 150 occurs at the center of the extraction opening 140, although other embodiments are possible. For example, as shown in FIG. 4D, the maximum thickness of the protrusion may occur proximate to the first end 104 and / or the second end 105. This can be beneficial when the ion source generates a higher plasma density near the ends.

[0030] The protrusion 150 may have any suitable shape. For example, in FIGS. 2A-2B, the cross-section of the protrusion 150 is a rectangle extending inwards from the inner wall. The dimensions of the rectangle are defined as a thickness dimension towards the center of the chamber and a height perpendicular to the thickness. The protrusion 150 may have a height between 0.060 inches and 0.250 inches. This protrusion 150 may be referred to as a fin. Of course, other shapes are also possible. For example, the cross-section of the protrusion 150 may be rounded and have a radius of curvature such that there are no edges within the chamber 100.

[0031] Furthermore, the outer surface of the protruding wall 151 facing away from the chamber 100 may remain unchanged and flat. More specifically, the protrusion 150 extends into the chamber 100. Furthermore, the thickness of the protrusion 150 may vary as a function of its position in the width direction (i.e., the X direction). For example, the thickness of the protrusion 150 may be greatest at the center of the extraction opening 140 and may decrease as it moves away from the center towards the first end 104 and the second end 105.

[0032] In certain embodiments, the maximum difference between the thinnest part and the thickest part of the protrusion 150 is between 5% and 25% of the height of the chamber 100. For example, the protrusion 150 may extend into the chamber 100 by at least 1 mm at at least one location. In certain embodiments, the protrusion 150 may extend into the chamber 100 by at least 3 mm at at least one location. Of course, in other embodiments, other dimensions may be used.

[0033] In certain embodiments, the protrusion 150 may have a smooth radius of curvature along the X direction, similar to that shown in FIGS. 1A-1B. However, other curvatures are possible. For example, there may be a first radius of curvature between the first end 104 and the center of the extraction opening 140, and a second radius of curvature between the second end 105 and the center of the extraction opening 140. Further, FIGS. 1A-1B show the protrusion 150 extending between the first end 104 and the second end 105, but in other embodiments, the protrusion 150 may be smaller in the width direction. Thereby, as shown in FIG. 4A and the like, the protrusion 150 starts at a position away from the first end 104 and terminates at a position before the second end 105.

[0034] FIGS. 1A-1B show a protruding wall 151 according to two embodiments. In these embodiments, the protrusion 150 starts at the first end 104 and extends to the second end 105. Further, the protrusion 150 has a constant radius of curvature throughout.

[0035] However, the protrusion 150 may have other shapes. For example, as shown in FIG. 4B, the protrusion 150 may appear triangular. The thickness of the protrusion 150 increases linearly from the first end 104 to the center of the extraction opening 140 and from the second end 105 to the center of the extraction opening 140. In other embodiments, the protrusion 150 starts at a position behind the first end 104 and terminates at a position before the second end 105.

[0036] Alternatively, as shown in FIG. 4C, the protrusion 150 may be trapezoidal. The thickness of the protrusion 150 increases linearly from the first end 104 and from the second end 105 to a flat region positioned near the center of the extraction opening 140. In other embodiments, the protrusion 150 starts at a position behind the first end 104 and terminates at a position before the second end 105.

[0037] Furthermore, all of the previous drawings show the protrusion 150 symmetric about the center of the extraction opening 140. However, a plurality of other embodiments are possible. For example, the plasma density within the ion source may be distributed as follows. That is, the density near the first end 104 may be greater than the density near the second end 105. In this case, as shown in FIG. 4E, the maximum (or minimum) thickness of the protrusion 150 may occur nearer the first end 104 than nearer the second end 105.

[0038] Furthermore, FIGS. 4A-4E show the protruding wall 151 facing the extraction plate 103, but in a plurality of other embodiments, the protruding wall 151 may be adjacent to the extraction plate 103, as shown in FIG. 2A and the like. In other words, the configuration of the protruding wall 151 shown in FIGS. 4A-4E can also be realized when the protruding wall 151 is adjacent to the extraction plate 103.

[0039] Furthermore, in FIGS. 4A-4C, it is assumed that the maximum plasma density is seen near the center of the extraction opening 140. However, when the maximum plasma density is located near the first end 104 and the second end 105, the shapes shown in FIGS. 4A-4C may be reversed as follows. That is, as shown in FIG. 4D, the minimum thickness is seen at the center of the extraction opening 140, and the maximum thickness is seen near the ends.

[0040] In another embodiment shown in FIGS. 5A-5B, the chamber 500 may be cylindrical. As shown in FIG. 5A, the protrusion 150 may be arranged opposite the extraction opening 140, that is, it may be offset by 180°. In a plurality of other embodiments, as shown in FIG. 5B, the protrusion may be arranged offset by 90° from the extraction opening 140. Of course, the protrusion 150 may be arranged at any position along the inner surface of the chamber 500. Furthermore, the shape of the protrusion 150 may be any of the shapes shown in FIGS. 1A-1B and 4A-4E described above.

[0041] Without being bound by a specific theory, the plasma within the IHC ion source 10 is thought to tend to rotate around the central axis 109. As shown in FIG. 1A, this central axis 109 passes through the center of the cathode 110 and the center of the reflecting electrode 120. This rotation can be caused by an E×B drift. Note that the magnetic field 190 is generated parallel to the central axis 109. Also, the potential of the plasma is greatest at its center and decreases as it moves towards the wall 101. Thus, there is an electric field perpendicular to the magnetic field 190. This combination generates an electromagnetic force in a direction perpendicular to both the magnetic field 190 and the electric field. It is this electromagnetic force that would cause this rotation.

[0042] By incorporating the protruding wall 151 into the chamber, the rotating plasma comes into contact with the protrusion 150. This neutralizes free electrons and ions, reducing the plasma density. This is shown in FIG. 6. Note that the plasma is rotating counterclockwise in this figure. Also note that the plasma density is significantly reduced on the left side of the protrusion 150. This phenomenon may be similar to a wood lathe. The lathe removes material at the location where the turning tool is applied to the workpiece.

[0043] In other words, although the plasma density is thought to be greater near the center of the extraction aperture 140, the plasma density within this region can be reduced by increasing the loss area within this region. Further, if the extraction current is known as a function of the width, it may be possible to appropriately shape the protrusion 150 in order to reduce the plasma cross-sectional area across the width. Thereby, the extracted ion beam current becomes substantially constant along the width direction.

[0044] The ability to properly shape the protrusion 150 can be achieved using the embodiment shown in FIG. 7. In this embodiment, the protrusion is formed by using a plurality of mechanically adjustable protrusion elements 152a - 152e. FIG. 7 shows five mechanically adjustable protrusion elements, but the number of elements is not limited by this disclosure. In one embodiment, each of the mechanically adjustable protrusion elements 152a - 152e may be independently controlled, allowing the protrusion to take on various different shapes. In a plurality of other embodiments, the group of mechanically adjustable protrusion elements 152a - 152e may be commonly controlled. As an example, the mechanically adjustable protrusion elements 152a and 152e may be commonly controlled, and the mechanically adjustable protrusion elements 152b and 152d may be commonly controlled. With this configuration, a protrusion symmetric about the center of the extraction opening 140 can be formed.

[0045] The mechanically adjustable protrusion elements 152a - 152e may be made of the same conductive material as the wall, such as tungsten or another suitable material. The mechanically adjustable protrusion elements 152a - 152e may be electrically connected to the wall 101 of the chamber 100. Further, the mechanically adjustable protrusion elements 152a - 152e may be cuboid. Thereby, the top view of the protrusion element is as shown in FIG. 7, and the side view is as shown in FIG. 2A or FIG. 2B. The dimensions of the rectangular protrusion element may be defined as a thickness that is the dimension towards the center of the chamber, a height that is perpendicular to the thickness, and a width that is the dimension in the X direction. These mechanically adjustable protrusion elements 152a - 152e may have a height between 0.060 inches and 0.250 inches. The mechanically adjustable protrusion elements 152a - 152e may have a thickness between at least 5% and 25% of the height of the chamber. Thereby, they may extend into the chamber. The width of each of the mechanically adjustable protrusion elements 152a - 152e may be the same, or they may be different. For example, in certain embodiments, the mechanically adjustable protrusion elements 152a - 152e extend across the entire width of the chamber. Thereby, each of the N elements has a width of approximately W / N. Here, W is the width of the chamber 100. In other embodiments, the mechanically adjustable protrusion elements 152a - 152e may also occupy 50% of the width of the chamber 100. In this example, each of the N elements has a width of approximately W / 2N. Here, W is the width of the chamber 100.

[0046] Of course, other shapes are also possible. For example, the cross - section of the mechanically adjustable protrusion elements 152a - 152e may be rounded as shown in FIGS. 2A - 2B and have a radius of curvature such that there are no edges within the chamber 100.

[0047] Furthermore, FIG. 7 shows that the mechanically adjustable protrusion element has a flat surface exposed inside the chamber, but other embodiments are also possible. For example, in the mechanically adjustable protrusion shown in FIG. 7, the inner surface may be rounded in the Y direction. These mechanically adjustable protrusion elements 152a - 152e may be constructed of another suitable material such as tungsten or a high - melting - point metal.

[0048] Furthermore, FIG. 7 shows a mechanically adjustable protrusion element disposed on the wall facing the extraction plate 103, but other embodiments are possible. For example, the mechanically adjustable protrusion element may be disposed on the wall adjacent to the extraction plate 103, similar to the configuration shown in FIG. 1B.

[0049] Furthermore, the mechanically adjustable protrusion element may be used with a cylindrical chamber, such as those shown in FIGS. 5A-5B.

[0050] In certain embodiments, the mechanically adjustable protrusion elements 152a-152e may be coupled to one or more actuators 153. In other embodiments, the mechanically adjustable protrusion elements 152a-152e may be manually moved.

[0051] In some embodiments, there may be a calibration process for determining the appropriate position for each of the mechanically adjustable protrusion elements. For example, a beam profiler, such as an array of Faraday cups, may be disposed outside the extraction aperture 140 along the beam line. For example, the array of Faraday cups may be disposed proximate to the platen 260. The beam profiler may communicate with the controller 180. The controller 180 controls the actuator 153 to improve the uniformity of the extracted ion beam.

[0052] The above-described is an ion source, which is an IHC ion source. However, other ion sources may also be used with this extraction plate 103. For example, a magnetized DC plasma source, a tubular cathode source, a Bernas ion source, and an inductively coupled plasma (ICP) ion source may also use this extraction plate 103 having the protrusion 150. Accordingly, the extraction plate may be used with ion sources having various different plasma generators.

[0053] The present system and method have many advantages. As described above, in certain plural ion sources that extract a ribbon ion beam, the ribbon ion beam is not uniform across its width. To attempt to correct this non-uniformity, various techniques have been employed. The present system provides a mechanism for selectively reducing the plasma density within a specific region within the chamber. In this way, even when the ion source generates a plasma with a higher density at a specific part of the chamber, such as near the center or the cathode, a protrusion or a mechanically adjustable protrusion element can compensate for this and enable a more uniform ion beam to be extracted. Further, this system addresses the non-uniformity in the ion source and reduces the complexity and number of components conventionally used in the beamline system to compensate for this issue.

[0054] The present disclosure is not limited to the scope by the specific plural embodiments described herein. Indeed, in addition to what is described herein, various other embodiments and modifications of the present disclosure will be apparent to those skilled in the art from the foregoing description and the accompanying drawings. For this reason, such other embodiments and modifications are intended to be included within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of specific embodiments for specific purposes in a specific environment, those skilled in the art will recognize that its usefulness is not limited thereto and that the present disclosure can be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below are to be construed in view of the broadest scope and spirit of the present disclosure described herein.

Claims

1. A chamber comprising a first end, a second end, and a plurality of walls connecting the first end and the second end, wherein one of the plurality of walls is an extraction plate having an extraction opening with a width greater than the height, and an ion source comprising a plasma generator for generating plasma within the chamber, and one of the plurality of walls different from the extraction plate is a protruding wall having a protrusion extending towards the interior of the chamber.

2. The ion source according to claim 1, wherein the protrusion extends into the chamber by at least 3 mm at at least one location.

3. The ion source according to claim 1, wherein the protrusion has a constant radius of curvature from the first end to the second end.

4. The ion source according to claim 1, wherein the protrusion has a triangular shape.

5. The ion source according to claim 1, wherein the protrusion has a trapezoidal shape.

6. The ion source according to claim 1, wherein the protruding wall faces the extraction plate.

7. The ion source according to claim 1, wherein the protruding wall is adjacent to the extraction plate.

8. The ion source according to claim 1, wherein the plasma generator comprises an indirectly heated cathode disposed at the first end.

9. The ion source according to claim 1, wherein the maximum thickness of the protrusion occurs at the center of the extraction opening in the width direction.

10. A chamber comprising a first end, a second end, and a cylindrical housing connecting the first end and the second end, wherein an extraction opening having a width greater than the height is disposed in the cylindrical housing, and an ion source comprising a plasma generator for generating plasma within the chamber, and a protrusion extending from the cylindrical housing towards the interior of the chamber.

11. The ion source according to claim 10, wherein the protrusion is disposed on the cylindrical housing opposite the extraction opening so as to be offset by 180° from the extraction opening.

12. The ion source according to claim 10, wherein the protrusion is offset by 90° from the extraction opening.

13. The ion source according to claim 10, wherein the plasma generator comprises an indirectly heated cathode disposed at the first end.

14. The ion source according to claim 10, wherein the maximum thickness of the protrusion occurs at the center of the extraction opening in the width direction.

15. A chamber comprising a first end, a second end, and a plurality of walls connecting the first end and the second end, wherein one of the plurality of walls is an extraction plate having an extraction opening with a width greater than its height. A plasma generator for generating plasma within the chamber, and An ion source comprising a plurality of mechanically adjustable protrusion elements extending into the interior of the chamber, electrically connected to one of the plurality of walls different from the extraction plate.

16. The ion source according to claim 15, further comprising an actuator for controlling the position of the plurality of mechanically adjustable protrusion elements within the chamber.

17. The ion source according to claim 16, wherein each of the plurality of mechanically adjustable protrusion elements is independently controlled.

18. The ion source according to claim 15, wherein the plurality of mechanically adjustable protrusion elements extend through the wall facing the extraction plate.

19. The ion source according to claim 15, wherein the plurality of mechanically adjustable protrusion elements extend through the wall adjacent to the extraction plate.

20. The ion source according to claim 15, wherein the plasma generator comprises an indirectly heated cathode disposed at the first end.

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