System and method for optimizing a fully horizontal scanned beam distance

Abstract

A method for optimizing the fully horizontal scanned beam distance of an accelerator beam is provided herein. In one method, the method includes placing a first Faraday cup along a first side of an intended beam scan region, placing a second Faraday cup along a second side of the intended beam scan region, scanning an ion beam along the first and second sides of the intended beam scan region, measuring a first beam current of the ion beam at the first Faraday cup and measuring a second beam current of the ion beam at the second Faraday cup, and determining an optimal scan distance of the ion beam across the intended beam scan region based on the first beam current and the second beam current.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of priority of U.S. Patent Application No. 17 / 827,204, filed May 27, 2022, which is hereby incorporated by reference in its entirety.

[0002] The present disclosure generally relates to ion beam processing techniques, and more particularly, to systems and methods for optimizing a fully horizontal scanned beam distance.

Background Art

[0003] Today, various types of processing apparatuses are employed to treat or process substrates with ions. In a processing substrate such as a semiconductor substrate, ions can be used to etch layers or features on the substrate. Ions can also be used to deposit layers or structures on the substrate, to implant nuclides into the substrate, or to amorphize the substrate. Also, techniques for monitoring the processing of the substrate to control the processing of the substrate have been developed.

[0004] A horizontal scan distance is used to scan the beam across the wafer diameter. Current techniques use an estimate of the beam edge to estimate the total required horizontal scan distance. However, over - scan or under - scan of the wafer often occurs because no actual measurement is performed to confirm that the beam is sufficiently scanned across the wafer.

[0005] Therefore, it would be beneficial to ensure that the beam is sufficiently scanned across the entire wafer diameter to provide uniform implantation and to optimize the beam current utilized during wafer implantation. This disclosure is provided in view of this and other considerations.

Summary of the Invention

[0006] The summary of the present invention is provided to introduce, in a simplified form, a selection of concepts that will be further described below in the detailed description of the invention. The summary of the present invention is not intended to identify the key features or essential features of the claimed subject matter, nor is it intended to be helpful in determining the scope of the claimed subject matter.

[0007] In one embodiment, a method may include providing a first Faraday cup position along a first side of an intended beam-scan area, providing a second Faraday cup position along a second side of the intended beam-scan area, scanning an ion beam along the first and second sides of the intended beam-scan area, measuring a first beam current of the ion beam at the first Faraday cup position, measuring a second beam current of the ion beam at the second Faraday cup position, and determining an optimal scan distance of the ion beam across the intended beam-scan area based on the first beam current and the second beam current.

[0008] In another embodiment, an apparatus for optimizing a scanned beam distance of an ion beam may include a beam scanner operable to scan a spot ion beam with respect to an intended beam-scan area, a Faraday cup disposed along a first side of the intended beam-scan area, and a Faraday profiler disposed along a second side of the intended beam-scan area, the Faraday cup being operable to measure a first beam current of the spot ion beam and the Faraday profiler being operable to measure a second beam current of the spot ion beam. The apparatus may further include a beam calibration component comprising a controller and a memory, the memory comprising a calibration routine operable on the controller to determine an optimal scan distance of the ion beam based on the first beam current and the second beam current.

[0009] In another embodiment, a non-transitory computer-readable storage medium, the non-transitory computer-readable storage medium including instructions that, when executed by a computer, cause the computer to scan a spot ion beam with respect to an intended beam scan region by a beam scanner, measure a first beam current of the spot ion beam in a first Faraday cup disposed along a first side of the intended beam scan region, and measure a second beam current of the spot ion beam in a second Faraday cup disposed along a second side of the intended beam scan region. The non-transitory computer-readable storage medium further includes instructions that, when executed by a computer, cause the computer to determine an optimal scan distance of the ion beam based on the first beam current and the second beam current.

[0010] Next, by way of example, embodiments of the present disclosure will be described with reference to the accompanying drawings.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 5

Figure 6

[0012] The drawings are not necessarily to scale. The drawings are merely illustrative and do not depict specific parameters of the present disclosure. The drawings show exemplary embodiments of the present disclosure and should not be considered as limiting the scope. In the drawings, like numerals represent like elements.

[0013] Furthermore, some elements in some of the figures may be omitted or not shown to scale for clarity of explanation. Cross-sectional views may be in the form of "fragmented" or "nearsighted" cross-sectional views that omit some background lines that would otherwise be visible in an "accurate" cross-sectional view for clarity of explanation. Additionally, for clarity, some reference numerals may be omitted in some of the drawings.

[0014] Next, the present embodiments will be described in more detail below with reference to the accompanying drawings, in which some embodiments are shown. The subject matter of the present disclosure can be embodied in many different forms and should not be construed as limited to the embodiments described herein. Instead, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the subject matter to those skilled in the art. Like numerals refer to like elements throughout.

[0015] The embodiments described herein provide a novel technique for optimizing the horizontal scan distance of an accelerator beam using beam current measurements from a set of Faraday cups disposed at opposing edges of a wafer. Unlike prior art techniques where beam edge estimation is used in an attempt to determine the total required horizontal scan distance, embodiments of the present disclosure use actual beam current measurements by Faraday cups disposed on each side of the wafer to determine the optimal scanned beam distance. This ensures that the beam passes beyond the edge of the wafer and minimizes the additional over-scanned distance. Advantageously, when the beam leaves the wafer, there is no wasted beam current and the beam current is utilized / optimized during wafer implantation. Further, the embodiments herein ensure that the beam is sufficiently scanned across the entire wafer diameter to guarantee uniform implantation. Still further, the embodiments herein advantageously ensure accurate measurements of the implantation monitoring Faraday cup for dose accuracy.

[0016] FIG. 1 shows a first embodiment of an apparatus 100 for determining an optimal scan distance for an ion implantation apparatus. The apparatus 100 can include a Faraday cup 101 at a first Faraday cup position 102 along a first side 104 of an intended beam scan region 106 and a Faraday cup or Faraday profiler 103 at a second Faraday cup position 110 along a second side 112 of the intended beam scan region 106. In some embodiments, only the Faraday cup 101 is present and measurements are taken at multiple positions by a single Faraday cup 101.

[0017] Although not limiting, the Faraday cup 101 is generally fixed along the x-direction, while the Faraday profiler 103 can move horizontally along the x-direction. For example, the Faraday profiler 103 can be arranged inside or outside the intended beam scan region 106. The first Faraday cup 102 can include a first aperture (not shown) operable to receive an indication of the current of the ion beam 114 when the ion beam 114 is scanned horizontally near the first side 104 (e.g., along the x-direction in the illustrated orientation). The Faraday profiler 103 can measure the current of the ion beam 114 when the ion beam 114 is scanned horizontally near the second side 112. As further described herein, the measurements obtained from the Faraday cup 101 and the Faraday profiler 103 can be used to determine when the beam current completely passes through a specific location outside the intended beam scan region 106, such as the first aperture of the Faraday cup 101. Although not limiting, the ion beam 114 can be an accelerator spot beam. In some cases, when the ion beam 114 passes by the Faraday cup 101 and the Faraday profiler 103, the left and right edges of the ion beam 114 can be detected. These edges can be approximately 0.6% of the detected peak (not the integrated current) of the spot ion beam 114.

[0018] The intended beam scan region 106 may generally correspond to the region where the wafer is to be processed (e.g., scanned) by the ion beam 114. During use, the ion beam 114 may be scanned horizontally (e.g., in the x direction), while the wafer may be moved vertically (e.g., along the y direction). The implantation region 106 may be defined by the outer perimeter 124, and the first side 104 and the second side 112 may correspond to opposing points on the circumference along the outer perimeter 124. The diameter of the intended beam scan region 106 may extend between the first side 104 and the second side 112. In the illustrated embodiment, the Faraday cup 101 is disposed outside the outer perimeter 124 in the first overscan region 130, and the Faraday profiler 103 is disposed outside the outer perimeter 124 in the second overscan region 132. The first overscan region 130 may include a first CLF dimension (CD1) corresponding to the length (e.g., along the x direction) between the first aperture and the first side 104.

[0019] During use, the ion beam 114 is scanned between the first side 104 and the second side 110 of the intended beam scan region 106. The first beam current of the ion beam 114 is measured at the first Faraday cup position 102, and the second beam current of the ion beam 114 is measured at the second Faraday cup position 110. Based on the first beam current and the second beam current, the optimal scan distance of the ion beam across the intended beam scan region 106 and across the first overscan region 130 and the second overscan region 132 can be determined. Advantageously, by optimizing the horizontal scan distance, the beam current can be increased. More specifically, the embodiments herein decrease the horizontal scan distance as much as possible to maximize the beam current in the case of a high-dose strategy. In another example, the horizontal scan distance is increased in the case of a low-dose strategy, and thus the beam current can be reduced. In other words, the apparatus 100 enables rapid adjustment of that distance to keep the beam current down to the target such that the horizontal scan distance is at least the minimum HSD.

[0020] In one embodiment, the ion beam 114 is scanned over a wide horizontal distance (e.g., from the first overscan region 130 to the second overscan region 132), and then the width in the horizontal direction can be gradually reduced toward the center of the intended beam scan region 106. FIG. 2A shows the relationship between the current and the first Faraday cup multiplier (hereinafter multiplier 1). As indicated by the reference line 133, the current is expected to increase linearly as the overscan is reduced. In other words, as the ion beam 114 moves away from the first overscan region 130 and toward the intended beam scan region 106, the current increases. A line 135 tracking an exemplary current measurement by the Faraday cup 101 shows a case where the overscan is insufficient and the line 135 deviates from the reference line 133. To determine an appropriate value for multiplier 1, a current deviation above or below a first predetermined threshold can be used. For example, a scan location before a “x”% drop in current from the expected value (reference line 133) can be selected. In various examples, “x” can be between 0.01 and 10. Thus, multiplier 1 can be approximately 1.1, as indicated by line 138 in this example.

[0021] As shown in FIG. 2B, a similar analysis can be performed for the Faraday profiler 103. The reference line 133 corresponds to the expected current that increases linearly, and the line 139 connects exemplary current measurements by the Faraday profiler 103. To determine an appropriate value for the second Faraday cup multiplier (hereinafter multiplier 2), a current deviation above or below a second predetermined threshold, in this case, a scan location before a “x”% drop in current from the expected value (reference line 133) can be used. In various examples, “x” can be between 0.01 and 10. Thus, multiplier 2 can be approximately 0.8, as indicated by line 140 in this example.

[0022] Using the following equation (1), the dynamic horizontal scan distance (ScanWidthTotal) of the ion beam 114 can be determined for the intended beam scan region 106 of the apparatus 100, the first overscan region 130, and the second overscan region 132. ScanWidthTotal = Multipler1 * Beam width + CLF distance + Wafer Diameter + Multipler2 * Beam width (1)

[0023] In the above, Beam width is a measurable value and can vary according to the parameters of the ion beam 114.

[0024] Figure 3 shows another method for determining the horizontal scan distance for apparatus 200. Apparatus 200 may be the same as or similar to apparatus 100. Thus, only some aspects of apparatus 200 are described below for brevity. In this embodiment, a set of stationary spot ion beams 214A, 214B are first placed in a first overscan region 230 and a second overscan region 232, respectively. The first ion beam 214A can be repeatedly shifted towards the Faraday cup 201 at the first Faraday position 202 via a scanner commanded to a fixed position. The Faraday cup 201 measures an increase in current as the first ion beam 214A moves towards the intended beam scan region 206. Similarly, the second ion beam 214B can be repeatedly shifted towards the Faraday profiler 203 at the second Faraday position 210 via a scanner commanded to a fixed position. The Faraday profiler 203 measures an increase in current as the second ion beam 214B moves towards the intended beam scan region 206. Based on the point where each beam is outside the intended beam scan region 206 and the Faraday cup 201 and the Faraday profiler 203 do not measure an increased beam current from a no-beam offset, the scan distance can be set. The above equation (1) can be reused to calculate the horizontal scan distance.

[0025] Figures 4A - 4C illustrate yet another method for determining the dynamic horizontal scan distance of the "high - speed spot" beam. In the "high - speed spot" beam method, the spot beam 214A can be swept multiple times, such as 16 times, across the Faraday cup 201 to obtain an average current response as a high - speed spot profile, which may require about 3 seconds. Similarly, the spot beam 214B can be swept multiple times, such as 16 times, across the Faraday profiler 203 to obtain an average current response as a high - speed spot profile. In this embodiment, the high - speed spot ion beam can be scanned around the CLF position (i.e., the aperture) of the Faraday cup 201 to determine the current - versus - position profile 260, as shown in FIG. 4B. The high - speed spot ion beam can be similarly scanned in the Faraday profiler 203 to determine the current edge at the edge of the intended beam scan region 206 based on the current - versus - position profile 262 shown in FIG. 4C. The high - speed spot data can then be used to determine the measured current edge, and then the scan distance is set based on the high - speed spot current measurement distance.

[0026] FIG. 5 shows a block-form plan view of a beamline ion implantation apparatus, shown as ion implantation apparatus 300, according to various embodiments of the present disclosure. Ion implantation apparatus 300 includes an ion source 302 configured to generate an ion beam 304. Ion beam 304 may be provided as a spot beam that is scanned along a direction such as the X direction. In the convention used herein, the Z direction refers to the direction of an axis parallel to the central ray trajectory of ion beam 304. Thus, the absolute direction of the Z direction and the absolute direction of the X direction, where the X direction is perpendicular to the Z direction, may vary at different points within ion implantation apparatus 300, as shown. Ion beam 304 may proceed through analyzer magnet 306, mass separation slit 308, and collimator 312 before affecting substrate 316 disposed on substrate stage 314. Substrate stage 314 may be configured to scan substrate 316 at least along the Y direction in some embodiments. In the example shown in FIG. 5, ion implantation apparatus 300 includes a beam scanner 310. When ion beam 304 is provided as a spot beam, beam scanner 310 scans ion beam 304 along the X direction to produce a scanned ion beam, and may be scanned along the X direction across the substrate. The width of the resulting scanned spot beam may correspond to the width W of substrate 316.

[0027] Ion implantation apparatus 300 further includes a set of current detectors 318A - 318B, such as a Faraday cup current detector for monitoring the beam current provided to substrate 316, and in particular a closed-loop Faraday current detector, and a profiler Faraday cup for measuring beam uniformity. Current detectors 318A - 318B may be placed along opposite sides of substrate 316 to intercept ion beam 304 and may be configured to record the beam current of ion beam 304 during optimization operations of various horizontal scanned beam distances, as described above.

[0028] Ion implantation device 300 also includes a beam calibration component 320. The beam calibration component 320 can be coupled to beam scanner 310 and current detectors 318A, 318B. As a result of the beam distance optimization procedure, the beam calibration component 320 can be coupled to one or more components to adjust the scan of ion beam 304 to provide more uniform and efficient ion implantation to substrate 316. The beam calibration component 320 can include logic for determining ScanWidthTotal based on the application of various beam measurements and for determining the application of routines based on these measurements, as described in the examples above. The logic can further generate an adjustment signal for adjusting the scan of ion beam 304 based on the determined ScanWidthTotal. In some cases, the logic of beam calibration component 320 can be implemented in a combination of software and hardware, or firmware. In some examples, beam calibration component 320 can include a circuit such as controller 320-A and a memory 320-B coupled to software for executing instructions for adjusting the scan of ion beam 304 based on the determination of ScanWidthTotal. Embodiments are not limited to this context.

[0029] Referring to FIG. 6, a method 400 according to an embodiment of the present disclosure is described. In block 401, method 400 can include providing a first Faraday cup position along a first side of the intended beam scan region and providing a second Faraday cup position along a second side of the intended beam scan region. In some embodiments, the Faraday cup can be located at the first Faraday cup position and the Faraday profiler can be located at the second Faraday cup position. The first Faraday cup position and the second Faraday cup position can be located at points that are circumferentially opposite along the same horizontal axis of the intended beam scan region.

[0030] In block 402, method 400 may further include scanning an ion beam along a first side and a second side of an intended beam scan region. In some embodiments, the ion beam may be scanned completely across the intended beam scan region, the first Faraday cup position, and the second Faraday cup position. In some embodiments, the ion beam may be scanned only at the first Faraday cup position and the second Faraday cup position. That is, the spot beam may be held beyond each of the Faraday cup and the Faraday profiler and moved inwardly toward the intended beam scan region and stopped at the edge of the intended beam scan region. This process may be implemented using high-speed spot beam operation.

[0031] In block 403, method 400 may include measuring a first beam current of the ion beam at the first Faraday cup position and measuring a second beam current of the ion beam at the second Faraday cup position.

[0032] In block 404, method 400 may include determining an optimal scan distance of the ion beam across the intended beam scan region based on the first beam current and the second beam current. In some embodiments, determining the optimal scan distance includes scanning the ion beam beyond the first side of the intended beam scan region until the ion beam completely passes through the first aperture of the Faraday cup and scanning the ion beam beyond the second side of the intended beam scan region until the ion beam completely passes through the Faraday profiler. In some embodiments, the method may further include determining that the ion beam has completely passed through the first aperture of the Faraday cup when the first current measurement of the Faraday cup reaches a first predetermined threshold and determining that the ion beam has completely passed through the second aperture of the second Faraday cup when the second current measurement of the second Faraday cup reaches a second predetermined threshold.

[0033] The foregoing description is presented for purposes of illustration and description and is not intended to limit the disclosure to the one or more forms disclosed herein. For example, the various features of the disclosure may be grouped together in one or more aspects, embodiments, or configurations for the purpose of streamlining the disclosure. However, it should be understood that the various features of some aspects, embodiments, or configurations of the disclosure may be combined in alternative aspects, embodiments, or configurations. Moreover, the following claims are hereby incorporated herein by reference as forms for carrying out the invention, and each claim stands on its own as an individual embodiment of the disclosure.

[0034] Elements or steps recited in the singular and preceded by the word “a” or “an” are to be understood as not excluding a plurality of elements or steps, unless such exclusion is explicitly recited. Further, reference to “one embodiment” of the disclosure is not to be construed as excluding the existence of additional embodiments that also incorporate the recited features.

[0035] The use of the terms “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Thus, the terms “including,” “comprising,” or “having” and variations thereof are open-ended expressions and may be used interchangeably herein.

[0036] References indicating all directions (e.g., proximal, distal, upper, lower, upward, downward, left, right, lateral, longitudinal, front, rear, top, bottom, above, below, vertical, horizontal, radial, axial, clockwise, and counterclockwise) are used only for identification purposes to assist the reader's understanding of the present disclosure and do not create limitations with respect to position, orientation, or use of the present disclosure. References to connection (e.g., attached, coupled, connected, and joined) should be construed broadly and may include intermediate members between sets of elements and relative movement between elements, unless otherwise specified. Thus, references to connection do not necessarily infer that two elements are directly connected and in a fixed relationship to each other.

[0037] Furthermore, references to identification (e.g., primary, secondary, first, second, third, fourth, etc.) do not imply importance or priority and are used to distinguish one feature from another. The drawings are for illustrative purposes only, and the dimensions, positions, orders, and relative sizes reflected in the drawings attached hereto may vary.

[0038] Additionally, the terms "substantial" or "substantially", as well as the terms "approximate" or "approximately", may be used interchangeably in some embodiments and may be described using any relative measure acceptable to those skilled in the art. For example, these terms can serve to compare with a reference parameter to indicate a deviation that can provide the intended function. By way of non-limiting example, the deviation from the reference parameter can be in an amount such as less than 1%, less than 3%, less than 5%, less than 10%, less than 15%, less than 20%, etc.

[0039] Although some embodiments of the present disclosure have been described herein, the present disclosure is broad as permitted by the art and this specification may be read accordingly, so the present disclosure is not limited to those embodiments. Accordingly, the above description should not be construed as limiting. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

1. providing a first Faraday cup position along a first side of the intended beam scan region; providing a second Faraday cup position along a second side of the intended beam scan region; scanning an ion beam along the first side and the second side of the intended beam scan region; measuring a first beam current of the ion beam at the first Faraday cup position and measuring a second beam current of the ion beam at the second Faraday cup position; determining an optimum scan distance of the ion beam based on the first beam current and the second beam current A method comprising the above.

2. Scanning the ion beam along the first side and the second side of the intended beam scan region includes: scanning the ion beam beyond the first side of the intended beam scan region until the ion beam completely passes through a first aperture of a first Faraday cup at the first Faraday cup position; scanning the ion beam beyond the second side of the intended beam scan region until the ion beam completely passes through the second Faraday cup position The method according to claim 1, comprising the above.

3. The method according to claim 2, further comprising: determining that the ion beam has completely passed through the first aperture of the first Faraday cup when the first beam current of the first Faraday cup reaches a first predetermined threshold; and determining that the ion beam has completely passed through the second Faraday cup position when the second beam current at the second Faraday cup position reaches a second predetermined threshold.

4. Determining the optimum scan distance of the ion beam includes: determining a beam width of the ion beam; multiplying the beam width by a first multiplier to obtain a first product, wherein the first multiplier is determined from the first predetermined threshold; adding the first product to a length dimension between the first aperture and a first side of the implantation region to determine a first overscan value; Multiplying the beam width by a second multiplier to obtain a second overscan value, wherein the second multiplier is determined from the second predetermined threshold, multiplying the beam width by the second multiplier; Adding together the first overscan value, the second overscan value, and the diameter of the intended beam scan region The method according to claim 3, further comprising.

5. Scanning the ion beam along the first side and the second side of the intended beam scan region, First, in a first overscan region, disposing the ion beam beyond the first Faraday cup; Moving the ion beam toward the first side of the intended beam scan region The method according to claim 2, comprising.

6. Scanning the ion beam along the first side and the second side of the intended beam scan region, First, in a second overscan region, disposing the ion beam beyond the second Faraday cup position; Moving the ion beam toward the second side of the intended beam scan region The method according to claim 5, further comprising.

7. The method according to claim 1, further comprising changing the current of the ion beam based on the determined optimal scan distance of the ion beam.

8. An apparatus for optimizing the scanned beam distance of an ion beam, the apparatus comprising: A beam scanner operable to scan a spot ion beam with respect to an intended beam scan region; A Faraday cup along a first side of the intended beam scan region; A Faraday profiler along a second side of the intended beam scan region, wherein the Faraday cup is operable to measure a first beam current of the spot ion beam, and the Faraday profiler is operable to measure a second beam current of the spot ion beam. A beam calibration component comprising a controller and a memory, wherein the memory comprises a calibration routine operable on the controller to determine an optimal scan distance of the ion beam based on the first beam current and the second beam current, the beam calibration component and An apparatus comprising.

9. The apparatus according to claim 8, wherein the beam scanner is operable to scan the spot ion beam along a first side and a second side of the intended beam scan region.

10. The beam scanner operable to scan the spot ion beam along a first side and a second side of the intended beam scan region, Scanning the spot ion beam beyond the first side of the intended beam scan region until the spot ion beam completely passes through the first aperture of the Faraday cup; Scanning the spot ion beam beyond the second side of the intended beam scan region until the spot ion beam completely passes through the Faraday profiler The apparatus according to claim 9, further operable to perform.

11. The calibration routine is Determining that the ion beam has completely passed through the first aperture of the Faraday cup when the first beam current of the Faraday cup reaches a first predetermined threshold; Determining that the ion beam has completely passed through the Faraday profiler when the second beam current of the Faraday cup reaches a second predetermined threshold The apparatus according to claim 10, further operable on the controller to perform.

12. The calibration routine is Determining the beam width of the ion beam; Multiplying the beam width by a first multiplier to obtain a first product, wherein the first multiplier is determined from the first predetermined threshold, multiplying the beam width by a first multiplier; Adding the first product to a length dimension between the first aperture and a first side of the implantation region to determine a first overscan value; Multiplying the beam width by a second multiplier to obtain a second overscan value, wherein the second multiplier is determined from the second predetermined threshold, multiplying the beam width by the second multiplier; Summing the first overscan value, the second overscan value, and the diameter of the intended beam scan region; The apparatus according to claim 11, further operable on the controller to determine the optimal scan distance of the ion beam thereby. **Claim 13** The beam scanner is First, in a first overscan region, disposing the ion beam beyond the Faraday cup; Moving the ion beam toward the first side of the intended beam scan region; The apparatus according to claim 8, further operable to perform. **Claim 14** The beam scanner is First, in a second overscan region, disposing the ion beam beyond the Faraday profiler; Moving the ion beam toward the second side of the intended beam scan region; The apparatus according to claim 8, further operable to perform. **Claim 15** A non-transitory computer-readable storage medium, the non-transitory computer-readable storage medium including instructions that, when executed by a computer, cause the computer to Scan a spot ion beam with respect to an intended beam scan region by a beam scanner; Measure a first beam current of the spot ion beam in a first Faraday cup disposed along a first side of the intended beam scan region and measure a second beam current of the spot ion beam in a second Faraday cup disposed along a second side of the intended beam scan region; Determine an optimal scan distance of the ion beam based on the first beam current and the second beam current; A non-transitory computer-readable storage medium causing the above to be performed. **Claim 16** The non-transitory computer-readable storage medium according to claim 15, wherein the instructions further configure the computer to scan the spot ion beam along the first side and the second side of the intended beam scan region. **Claim 17** The command further configures the computer to scan the spot ion beam beyond the first side of the intended beam scan region until the spot ion beam completely passes through the first aperture of the first Faraday cup, scan the spot ion beam beyond the second side of the intended beam scan region until the spot ion beam completely passes through the second aperture of the second Faraday cup The non-transitory computer-readable storage medium according to claim 15, which is further configured to perform the above. **Claim 18** The command further configures the computer to determine that the spot ion beam has completely passed through the first aperture of the first Faraday cup when the first beam current of the first Faraday cup reaches a first predetermined threshold, determine that the spot ion beam has completely passed through the second aperture of the second Faraday cup when the second beam current of the second Faraday cup reaches a second predetermined threshold The non-transitory computer-readable storage medium according to claim 17, which is further configured to perform the above. **Claim 19** The command further configures the computer to determine the beam width of the ion beam, multiply the beam width by a first multiplier to obtain a first product, wherein the first multiplier is determined from a first predetermined threshold, multiplying the beam width by the first multiplier, add the first product to the length between the first aperture and the first side of the implantation region to determine a first overscan value, multiply the beam width by a second multiplier to obtain a second overscan value, wherein the second multiplier is determined from a second predetermined threshold, multiplying the beam width by the second multiplier, sum the first overscan value, the second overscan value, and the diameter of the intended beam scan region The non-transitory computer-readable storage medium according to claim 15, which is further configured to perform the above. **Claim 20** The command further configures the computer to first, in a first overscan region, place the ion beam beyond the first Faraday cup Measuring the first beam current when the spot ion beam moves toward the first side of the intended beam scan region; First, disposing the spot ion beam beyond the second Faraday cup in a second overscan region; Measuring the second beam current when the spot ion beam moves toward the second side of the intended beam scan region The non-transitory computer-readable storage medium according to claim 15, further configured to perform the above.

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