Shield for ion implanter

Abstract

A shadow mask for use with a rotatable platen is disclosed. The shadow mask includes an exposed portion and a frame that attaches the shadow mask to the platen. The exposed portion of the shadow mask has an arcuate back surface that faces the platen and an opposing exposed surface that faces the ion beam. The exposed surface is designed so that the ion beam impinges the exposed surface at an angle of approximately 90°, as sputtering can be reduced at such angles. The exposed surface can have various shapes, including flat, circular, or skewed. Additionally, the exposed surface can include multiple exposed segments separated by connecting segments that are not exposed to the ion beam. The shadow mask can be graphite, silicon, or silicon carbide.

Description

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 621,830, filed January 17, 2024, and U.S. Patent Application No. 18 / 946,776, filed November 13, 2024, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0002] This disclosure describes an embodiment of a shielding element used in an ion implanter to protect the platform. Background Technology

[0003] Semiconductor devices are fabricated using multiple processes, some of which involve ion implantation into a workpiece. Some implanters have the ability to monitor the ion beam guided toward the workpiece. The incident ion beam is typically very narrow in the height direction but has a width larger than the diameter of the workpiece. This width can be achieved using a strip ion beam or by scanning a point ion beam.

[0004] Ion beams typically strike the workpiece at an angle orthogonal to the ion beam direction. However, in some embodiments, implantation at an angle not orthogonal to the ion beam may be useful. This can be referred to as angled implantation.

[0005] When the workpiece is tilted, the ion beam may impact the stage. Therefore, in some cases, a shield can be placed around the stage to protect it from such ion beam impacts. The purpose of the shield is to withstand ion beam impacts and prevent damage to the stage. However, there is a possibility that the ion beam may cause sputtering of the shield, resulting in undesirable particles.

[0006] Therefore, it would be beneficial to have a shielding device that protects the stage but produces fewer particles when bombarded by an ion beam. Summary of the Invention

[0007] A shielding member for use with a rotatable stage is disclosed. The shielding member includes an exposed portion and a frame for attaching the shielding member to the stage. The exposed portion of the shielding member has an arcuate back surface facing the stage and a contrasting exposed surface facing the ion beam. The exposed surface is designed such that the ion beam impacts the exposed surface at an angle of approximately 90°, which reduces sputtering. The exposed surface can have various shapes, including flat, circular, or skewed. Additionally, the exposed surface may include multiple exposed segments separated by connecting segments not exposed to the ion beam. The shielding member can be graphite, silicon, silicon carbide, or another material.

[0008] According to one embodiment, an ion implanter is disclosed. The ion implanter includes: an ion source for generating ions; a platform for supporting a workpiece, the workpiece being treated using an ion beam generated by the ions, wherein, when the ion beam reaches the workpiece, the ion beam has a longer dimension in the X direction, a smaller dimension in the Y direction, and a travel direction in the Z direction, wherein the Y direction is perpendicular to the X direction; wherein the platform is positioned within a process chamber of the ion implanter and includes a base and an electrostatic chuck; and a shielding member for protecting the electrostatic chuck from the ion beam; wherein the shielding member includes a surface exposed to the ion beam, the surface being referred to as an exposed surface, and wherein, when measurements are performed in the XZ plane, the ion beam impacts the exposed surface at an angle deviating from the normal by 20° or less. In some embodiments, the electrostatic chuck is maintained at an X tilt angle of at least 60°. In some embodiments, when measurements are performed in the XZ plane, the ion beam impacts the exposed surface at an angle deviating from the normal by 10° or less. In some embodiments, when measurements are performed in the XZ plane, the ion beam impacts the exposed surface at a normal angle. In some embodiments, when measurements are performed in the YZ plane, the ion beam impinges on the exposed surface at an angle deviating from the normal by 20° or less. In some embodiments, when measurements are performed in the YZ plane, the ion beam impinges on the exposed surface at the normal angle. In some embodiments, the electrostatic chuck is tilted at an X-angle of θ° relative to vertical, and the angle between the exposed surface and the top surface of the electrostatic chuck in the YZ plane is 180-θ° or less. In some embodiments, the angle between the exposed surface and the top surface of the electrostatic chuck in the YZ plane is an acute angle. In some embodiments, the shielding element is made of graphite.

[0009] According to another embodiment, a shielding member for use with a stage is disclosed. The shielding member includes: an exposed portion; and a frame connecting the exposed portion to the stage; wherein the exposed portion includes a back surface and an exposed surface opposite the back surface, the back surface being configured adjacent to the stage and having an arcuate shape, the exposed surface being adapted to be exposed to an ion beam, wherein the exposed portion has a first dimension, referred to as a width, the first dimension being at least as wide as the stage, and wherein the exposed surface is substantially straight along the first dimension. In some embodiments, the exposed surface is configured such that the exposed surface does not bend, curl, or skew more than 10° along the first dimension. In some embodiments, the exposed surface is flat along the first dimension. In some embodiments, the exposed portion includes a top surface, and the top surface forms an acute angle with the exposed surface. In some embodiments, the exposed portion is graphite. In some embodiments, the exposed portion includes a top surface, and the top surface forms an obtuse angle with the exposed surface such that the exposed surface is substantially perpendicular to the ion beam in two directions.

[0010] According to another embodiment, a shielding member for use with a stage is disclosed. The shielding member includes: an exposed portion; and a frame connecting the exposed portion to the stage; wherein the exposed portion includes a back surface and an exposed surface opposite the back surface, the back surface being configured adjacent to the stage and having an arcuate shape, the exposed surface being adapted to be exposed to an ion beam, wherein the exposed portion has a first dimension, referred to as a width, the first dimension being at least as wide as the stage, and wherein the exposed surface includes a plurality of exposed segments configured to be substantially parallel to each other in the first dimension and a plurality of connecting segments disposed between adjacent exposed segments, wherein the plurality of connecting segments form an angle of 90° or less with the adjacent exposed segments. In some embodiments, the plurality of exposed segments are parallel to each other. In some embodiments, the plurality of connecting segments form an angle of less than 90° with the adjacent exposed segments. In some embodiments, the exposed portion is graphite. In some embodiments, the exposed portion includes a top surface, and the top surface forms an obtuse angle with the exposed surface such that the exposed surface is substantially perpendicular to the ion beam in two directions. Attached Figure Description

[0011] For a better understanding of this disclosure, reference is made to the accompanying drawings, in which the same reference numerals are used to refer to the same elements and in the drawings:

[0012] Figure 1 This is a block diagram of an ion implanter using a shielding element according to one embodiment;

[0013] Figure 2 It is a block diagram of a process chamber with a platform and shielding components;

[0014] Figure 3 This shows the rotation and tilting of the workpiece on the platform;

[0015] Figure 4 The process chamber is shown with an electrostatic chuck at a large X-angle.

[0016] Figure 5 A top view of a shielding member according to one embodiment is shown;

[0017] Figures 6A-6C A top view of a shielding member according to several different embodiments is shown;

[0018] Figures 7A-7C A side view of a shielding member according to several different embodiments is shown; and

[0019] Figure 8 A side view of the shielding member according to another embodiment is shown. Detailed Implementation

[0020] Figure 1An ion implanter including a process chamber 100 is shown, the process chamber 100 including a platform and a shielding element. An ion source 200 is used to generate ions. 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 another type of source. Therefore, the type of ion source is not limited to this disclosure. An extraction optics 201 is disposed outside and close to the extraction opening of the ion source 200, and the extraction optics 201 may include one or more electrodes.

[0021] The mass analyzer 210 is located downstream of the extraction optics 201. The mass analyzer 210 uses a magnetic field to guide the path of the extracted ion beam. The magnetic field influences the ion flight path based on the ion's mass and charge. A mass resolution device 220 with a resolution 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 extracted ion beam with the selected mass and charge will be guided through the resolution aperture 221. Other ions will collide with the walls of the mass resolution device 220 or the mass analyzer 210 and will not travel further in the system.

[0022] Collimator 230 may be disposed downstream of mass analyzer 220. Collimator 230 receives ions from the ion beam passing through analyzer aperture 221 and forms an ion beam 250 composed of multiple parallel or nearly parallel beamlets. The output or distal end of mass analyzer 210 may be separated from the input or proximal end of collimator 230 by a fixed distance. Mass analyzer 220 is disposed in the space between the two components.

[0023] Accelerator / decelerator stage 240 may be located downstream of collimator 230. Accelerator / decelerator stage 240 is a beamline lens assembly configured to independently control the deflection, deceleration, and focusing of ion beam 250. For example, acceleration / decelerator stage 240 may be an electrostatic filter (EF). Ion beam 250 exiting acceleration / decelerator stage 240 enters process chamber 100.

[0024] Controller 280 may communicate with one or more power supplies, enabling monitoring and / or modification of the voltage or current supplied by those power supplies. Controller 280 may include a processing unit, such as a microcontroller, personal computer, dedicated controller, or other suitable processing unit. Controller 280 may also include non-transitory storage elements, such as semiconductor memory, magnetic memory, or other suitable memory. Such non-transitory storage elements may contain instructions and other data that enable controller 280 to perform the functions described herein.

[0025] In some embodiments, the ion source 200 may generate a ribbon-like ion beam that travels through the components. Therefore, although... Figure 1 A strip ion beam system is shown, but it should be understood that the ion implantation system may utilize a scanning beam. Such an ion implanter includes an ion source that generates ions in the form of a point ion beam. As described above, this type of ion implanter also includes a mass analyzer and a mass resolution device. Additionally, a scanner (which may be electrostatic or of another type) is used to form the scanning ion beam. Specifically, the point beam may enter an electrostatic scanner used to scan the point beam in the width direction to form a scanning ion beam in the form of an ion beam whose width is much greater than its height. The scanning ion beam may then pass through an angle corrector. The angle corrector is designed to deflect the ions in the scanning ion beam to generate an ion beam with parallel ion trajectories, thereby focusing the scanning ion beam. Specifically, the angle corrector is used to change diverging ion trajectory paths into substantially parallel paths of the ion beam 250. In some embodiments, the angle corrector may include spaced magnetic pole pieces defining a gap and a magnetic coil coupled to a power source. The scanning 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.

[0026] In both configurations, when the ion beam 250 reaches the workpiece, the ion beam has a larger dimension in the X direction and a smaller dimension in the Y direction. The X direction can be referred to as the width of the ion beam, and the Y direction can be referred to as the height of the ion beam. The X and Y directions are perpendicular to each other. Furthermore, the ion beam 250 travels in the Z direction.

[0027] Figure 2 Show in more detail Figure 1 The process chamber 100 is shown. The process chamber 100 includes a platform 120 on which a workpiece 110 may be disposed. When in the operating position, an ion beam 250 impacts the workpiece 110. The platform 120 may include an electrostatic chuck 140 for clamping and holding the workpiece 110 when the ion beam 250 is guided into the process chamber 100. In some embodiments, the platform 120 may be raised and lowered in the Y direction 127 by movement of the shaft 128.

[0028] In addition, the platform 120 can rotate around different axes. Figure 3 The table 120 and its various rotation directions are shown. Figure 3 A perspective view of a rotatable platform 120 (referred to as a roplat) is shown. Figure 2As shown, the roplat includes a base 130 and an electrostatic chuck 140. The electrostatic chuck 140 includes one or more electrodes that enable it to generate an electrostatic force to clamp the workpiece 110 to the clamping surface 129. The electrostatic chuck 140 is rotatably coupled to the base 130. The stage 120 may have three axes. A torsion axis 121 may be present, perpendicular to the clamping surface 129 of the electrostatic chuck 140 and passing through the center of the electrostatic chuck 140. Rotation about this torsion axis 121 is referred to as the torsion angle 122. Note that the electrostatic chuck 140 can rotate about the torsion axis 121 while the base 130 remains stationary. An X-axis 123 passes through the stage, parallel to the clamping surface 129 of the stage 120, and perpendicular to the torsion axis 121. The X-axis 123 is parallel to the width of the ion beam 250. The tilt around the X-axis 123 is called the X-tilt angle 124 and is achieved by rotating the electrostatic chuck 140 on the base 130. The X-tilt angle is measured relative to the vertical direction. In other words, when the clamping surface 129 is vertical, as... Figure 2 As shown, the X-tilt angle is defined as 0°. A 90° X-tilt angle is defined as being in a horizontal position. A Y-axis 125 also exists, passing through the stage 120, parallel to the clamping surface 129 of the stage 120, and perpendicular to the torsion axis 121 and the X-axis 123. The Y-axis 125 is parallel to the narrow dimension of the ion beam 250. The tilt about the Y-axis 125 is referred to as the Y-tilt angle 126 and can be achieved by moving the base 130. For example, the Y-tilt angle 126 can be achieved by rotating the shaft 128.

[0029] In some embodiments, the electrostatic chuck 140 can be rotated 90° about the X-axis 123 such that the clamping surface 129 of the electrostatic chuck 140 is horizontal, thereby placing the workpiece 110 on the platform 120. This may be referred to as the loading position. Then, the electrostatic chuck 140 is rotated about the X-axis 123 to... Figure 2 The operation or implantation location is shown in the figure.

[0030] Note that, as Figure 4 As shown, when the electrostatic chuck 140 is tilted about the X-axis 123, the bottom portion of the electrostatic chuck 140 can be exposed to the incident ion beam 250. Therefore, a shielding member 300 can be added to protect the electrostatic chuck 140. Figure 5A top view of the shield 300 is shown when the stage 120 is in the loading position. The shield 300 includes an exposed portion 310 positioned along a lower portion of the electrostatic chuck 140. The lower portion is defined as the portion of the electrostatic chuck 140 facing the ion beam 250 when the electrostatic chuck 140 is in the loading position. The exposed portion 310 has a first dimension (also referred to as width) generally wider than the electrostatic chuck 140 along the X direction and a second dimension perpendicular to the first direction, the second dimension being smaller than the first dimension (also referred to as length). When the stage is in the loading position, the second dimension is parallel to the Z direction. When the stage is in the loading position, the exposed portion 310 also has a thickness perpendicular to the first and second dimensions and parallel to the Y direction. The exposed portion 310 also has a top surface that is parallel to the top surface of the electrostatic chuck 140.

[0031] The exposed portion 310 has an exposed surface 311 facing the ion beam 250 and extending along a first dimension. The exposed portion 310 also has a back surface 312 facing the electrostatic chuck 140. In some embodiments, the back surface 312 is arcuate, and its diameter is slightly larger than the diameter of the electrostatic chuck 140. The shielding member 300 also includes a frame 320 for attaching the exposed portion 310 to the base 130. The frame 320 may have one or more supports 321 for attaching the exposed portion 310 to the base 130.

[0032] The exposed portion 310 of the shielding member 300 may be made of graphite. It has been found that sputtering on the graphite surface is minimized when the ion beam strikes the graphite at an angle orthogonal to the graphite surface. Furthermore, sputtering increases as the angle formed between the ion beam and the graphite surface deviates from the normal. Specifically, the sputtering amount remains low within an angle of no more than approximately 20° relative to the normal, and increases more rapidly when the angle deviates beyond 20°.

[0033] Therefore, in one embodiment, the exposed surface 311 of the shielding member 300 is flat along its width (i.e., the X direction) and perpendicular to the incident ion beam 250 in the XZ plane, as shown below. Figure 6A As shown in the diagram. Note that in this embodiment, the ion beam 250 is perpendicular to the exposed surface 311 in the XZ plane over the entire width of the exposed surface 311. In other words, when viewed from above, the ion beam is perpendicular to the exposed surface 311.

[0034] However, as mentioned above, the sputtering amount remains low as long as the incident angle deviates from the normal by no more than 20°. Therefore, in another embodiment, such as Figure 6BAs shown, the exposed surface 311 is not flat in the X direction, but has a curve or ramp. However, the radius of the curve or ramp is chosen such that the ion beam 250 does not impinge on the exposed surface 311 at an angle less than 70° or greater than 110° (when measured in the XZ plane). In another embodiment, the incident angle deviates from the normal by no more than 10°. Therefore, the radius of the curve or ramp is chosen such that the ion beam 250 does not impinge on the exposed surface 311 at an angle less than 80° or greater than 100° (when measured in the XZ plane). In other words, the exposed surface 311 is substantially straight. In this disclosure, the term "substantially straight" means that the exposed surface 311 is configured not to bend, curl, or skew more than 20° in any direction along the width exposed to the ion beam 250. Furthermore, in some embodiments, the exposed surface 311 is configured not to bend, curl, or skew more than 10° in the width or thickness direction.

[0035] Notice, Figures 6A-6B This includes a large exposed portion. In other embodiments, the size of the exposed portion 310 is reduced. Figure 6C One such embodiment is shown. In this embodiment, the exposed surface 311 includes a plurality of exposed segments 313, each of which is orthogonal to the incident ion beam 250 in the XZ plane. Connecting segments 314 are located between adjacent exposed segments 313. Connecting segments 314 may form an angle perpendicular to adjacent exposed segments 313. In other embodiments, connecting segments 314 may form an acute angle with two adjacent exposed segments 313. In this way, connecting segments 314 are not exposed to the ion beam 250. In another embodiment, the exposed segments 313 form an angle in the XZ plane relative to the ion beam 250 that is 20° or less off the normal. In other words, the exposed segments 313 may be substantially parallel to each other. The term "substantially parallel" indicates that the direction of each exposed segment 313 differs from the direction of any other exposed segment 313 by less than 20° and from the normal of the ion beam 250 by less than 20°. In some embodiments, similar to Figure 6C As shown, the exposed sections 313 are parallel to each other and orthogonal to the ion beam 250 in the XZ plane.

[0036] although Figures 6A-6C Several different embodiments are shown, but this disclosure is not limited to the embodiments shown herein. Specifically, any shielding member 300 may be used, in which the exposed surface 311 exposed to the ion beam 250 forms an angle between 70° and 110° with the ion beam 250 in the XZ plane.

[0037] However, the exposed surface 311 also has a thickness, which is in the Y direction when the platform 120 is in the loading position. Therefore, in some embodiments, such as Figures 7A-7BAs shown, the shielding element 300 is configured such that the exposed surface 311 is perpendicular to the ion beam 250 in the YZ plane. Note that the electrostatic chuck 140 can be set at different X tilt angles. Figure 7A An electrostatic chuck 140 with an X tilt angle of 80° is shown, as well as a shield 300 with an exposed surface 311 perpendicular to the incident ion beam 250 in the YZ plane.

[0038] Figure 7B An electrostatic chuck 140 with an X-tilt angle of 60° is shown, along with a shield 300 having an exposed surface 311 perpendicular to the incident ion beam 250 in the YZ plane. Note that different shields are used for each X-tilt angle to ensure that the exposed surface 311 is perpendicular to the ion beam 250 in the YZ plane.

[0039] Therefore, in one embodiment, a set of shielding elements is disclosed, each shielding element having an exposed surface 311, the exposed surface 311 being configured such that the ion beam 250 does not impinge on the exposed surface 311 at an angle less than 70° or greater than 110° (when measured in the XZ plane). Furthermore, each shielding element is configured for a specific X-tilt angle such that the exposed surface 311 is perpendicular to the ion beam 250 in the YZ plane.

[0040] To ensure that the exposed surface 311 is perpendicular to the ion beam 250 in the YZ plane, if the X tilt angle is given as θ, then the angle formed by the top surface of the electrostatic chuck 140 and the exposed surface of the shielding member 300 (in the YZ plane) is given as 180-θ. Since θ is always less than 90°, the angle formed between the top surface and the exposed surface of the shielding member 300 can be an obtuse angle.

[0041] Note that the angle at which the ion beam 250 impacts the exposed surface 311 may deviate from the normal in the YZ plane. As mentioned above, if the angle deviates from the normal by less than 20°, the sputtering amount is low. Therefore, in some embodiments, the exposed surface 311 is substantially perpendicular to the ion beam in both directions. The term "substantially perpendicular" indicates that the edge of the exposed surface 311 in contact with the ion beam differs from the normal of the ion beam 250 by less than 20° in both the YZ and XZ planes.

[0042] Therefore, the shielding member 300, which includes an exposed surface 311 forming a 70° angle with the top surface of the electrostatic chuck 140 in the YZ plane, can be used for implantation at tilt angles between 50° and 90°. Thus, a single shielding member can serve a range of tilt angles.

[0043] Furthermore, in some embodiments, it may be desirable for the angle to deviate relative to the normal, such that the ion beam 250 deviates in the downward direction relative to the exposed surface 311. Figure 7C Showing it Figure 7A The illustrated embodiment shows the shielding element 300 positioned at a 60° tilt angle on the electrostatic chuck 140. A fine beam of light 251 strikes the shielding element 300 and deflects downwards, away from the workpiece 110. Therefore, in these embodiments, the angle (in the YZ plane) formed between the top surface of the electrostatic chuck 140 and the exposed surface of the shielding element 300 is less than 180-θ, where θ is the X tilt angle.

[0044] In this scenario, a shield designed for an X-tilt angle of θ can be used with an electrostatic chuck 140 whose X-tilt angle is less than θ. However, in some embodiments, the opposite may not be true, making it impossible for a shield designed for an X-tilt angle of θ to be used with an electrostatic chuck 140 whose X-tilt angle is greater than θ.

[0045] In some embodiments, the angle between the top surface of the electrostatic chuck 140 and the exposed surface 311 in the YZ plane can be an acute angle, such as... Figure 8 As shown in the diagram. In this embodiment, the fine beam 251 from the ion beam 250 that strikes the exposed surface 311 will deflect downward toward the base 130.

[0046] Although the exposed portion 310 is described as graphite, it should be understood that other materials may also be used, such as monocrystalline silicon, silicon carbide, nickel, yttrium, zirconium, and doped diamond-like carbon (DLC).

[0047] This system offers several advantages. Traditional shielding devices have a curved exposed surface. Therefore, the ion beam strikes the exposed surface at varying angles along the X-axis. In the middle of the ion beam, it may be perpendicular to the exposed surface; however, the contact angle may decrease closer to the edge of the ion beam. As mentioned above, the sputtering rate of the shielding device can be related to the angle at which the ion beam strikes the exposed surface. By modifying the shielding device design so that the exposed surface of the shielding device struck by the ion beam is substantially perpendicular to the ion beam, the number of particles generated by sputtering from the shielding device can be reduced. Furthermore, this design can be accommodated within the space currently used by existing shielding devices.

[0048] The scope of this disclosure is not limited to the specific embodiments set forth herein. In fact, upon reading the foregoing description and accompanying drawings, various other embodiments and modifications thereof will become apparent to those skilled in the art, in addition to those described herein. Therefore, such other embodiments and modifications are intended to fall within the scope of this disclosure. Furthermore, although this disclosure has been set forth herein for a specific purpose, in a specific environment, and in the context of a specific implementation, those skilled in the art will recognize that the utility of this disclosure is not limited thereto, but that it can be advantageously practiced for any number of purposes and in any number of environments. Therefore, the scope of the following claims should be understood in light of the full scope and spirit of this disclosure as set forth herein.

Claims

1. An ion implanter, comprising: An ion source is used to generate ions; A platform for supporting a workpiece treated using an ion beam generated by the ions, wherein, when the ion beam reaches the workpiece, the ion beam has a longer dimension in the X direction, a smaller dimension in the Y direction, and a travel direction in the Z direction, wherein the Y direction is perpendicular to the X direction, wherein the platform is positioned within the processing chamber of the ion implanter and includes a base and an electrostatic chuck; and A shielding element is used to protect the electrostatic chuck from the effects of the ion beam; The shielding element includes a surface exposed to the ion beam, the surface being referred to as the exposed surface, and wherein, when measured in the XZ plane, the ion beam strikes the exposed surface at an angle deviating from the normal by 20° or less.

2. The ion implanter of claim 1, wherein the electrostatic chuck is maintained at an X tilt angle of at least 60°.

3. The ion implanter of claim 1, wherein when measurement is performed in the XZ plane, the ion beam strikes the exposed surface at an angle deviating from the normal by 10° or less.

4. The ion implanter of claim 1, wherein when the measurement is performed in the XZ plane, the ion beam strikes the exposed surface at a normal angle.

5. The ion implanter of claim 1, wherein when measured in the YZ plane, the ion beam strikes the exposed surface at an angle deviating from the normal by 20° or less.

6. The ion implanter of claim 1, wherein when measured in the YZ plane, the ion beam strikes the exposed surface at a normal angle.

7. The ion implanter of claim 1, wherein the electrostatic chuck is maintained at an X tilt angle of θ° relative to the vertical, and the angle between the exposed surface and the top surface of the electrostatic chuck in the YZ plane is 180-θ° or less than 180-θ°.

8. The ion implanter of claim 1, wherein the angle between the exposed surface and the top surface of the electrostatic chuck in the YZ plane is an acute angle.

9. The ion implanter of claim 1, wherein the shielding element is made of graphite.

10. A shielding element for use with a table, comprising: Exposed parts; as well as The frame connects the exposed portion to the platform; The exposed portion includes a back surface and an exposed surface opposite the back surface, the back surface being configured adjacent to the stage and having an arcuate shape, the exposed surface being adapted to be exposed to an ion beam, wherein the exposed portion has a first dimension referred to as a width, the first dimension being at least as wide as the stage, and wherein the exposed surface is substantially straight along the first dimension.

11. The shielding member of claim 10, wherein the exposed surface is configured such that the exposed surface does not bend, curl, or skew more than 10° along the first dimension.

12. The shielding member of claim 10, wherein the exposed surface is flat along the first dimension.

13. The shielding member of claim 10, wherein the exposed portion includes a top surface, and the top surface forms an acute angle with the exposed surface.

14. The shielding member of claim 10, wherein the exposed portion is graphite.

15. The shielding member of claim 10, wherein the exposed portion includes a top surface, and the top surface forms an obtuse angle with the exposed surface such that the exposed surface is substantially perpendicular to the ion beam in two directions.

16. A shielding member for use with a table, comprising: Exposed parts; as well as The frame connects the exposed portion to the platform; The exposed portion includes a back surface and an exposed surface opposite the back surface, the back surface being configured adjacent to the stage and having an arcuate shape, the exposed surface being adapted to be exposed to an ion beam, the exposed portion having a first dimension referred to as a width, the first dimension being at least as wide as the stage, and the exposed surface including a plurality of exposed segments configured to be substantially parallel to each other in the first dimension and a plurality of connecting segments disposed between adjacent exposed segments, wherein the plurality of connecting segments form an angle of 90° or less with the adjacent exposed segments.

17. The shielding member of claim 16, wherein the plurality of exposed sections are parallel to each other.

18. The shielding member of claim 16, wherein the plurality of connecting segments form an angle of less than 90° with the adjacent exposed segments.

19. The shielding member of claim 16, wherein the exposed portion is graphite.

20. The shielding member of claim 16, wherein the exposed portion includes a top surface, and the top surface forms an obtuse angle with the exposed surface such that the exposed surface is substantially perpendicular to the ion beam in two directions.

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