Closed-loop Faraday correction of horizontal beam current profile for uniform current tuning

Abstract

A system and method for generating a beam current profile that eliminates position-independent variations is disclosed. The system includes two Faraday sensors. One of the Faraday sensors is moved across the ion beam, while the second remains at or near a specific location. A reference Faraday sensor is used to measure the beam current variation over time, while the movable Faraday sensor measures both the position-dependent variation and the time-dependent variation. By combining these measurements, the actual position-dependent variation of the scanning ion beam can be determined. The resulting beam current profile can then be used to control the scan speed of an electrostatic or magnetic scanner.

Description

[Technical Field]

[0001] This application claims priority to U.S. Patent Application No. 17 / 897,719, filed August 29, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure relate to systems and methods for measuring the current profile of an ion beam and correcting for variations over time. [Background technology]

[0003] Ion implantation is a common technique for introducing impurities into a workpiece to affect the electrical conductivity of a portion of the workpiece. For example, to form a P-type region in a silicon workpiece, ions containing Group III elements (such as boron, aluminum, and gallium) may be used. To form an N-type region in a silicon workpiece, ions containing Group V elements (such as phosphorus and arsenic) may be used.

[0004] In some systems, a spot ion beam is scanned across the workpiece to implant ions. The scanning speed can determine the amount of ions each part of the workpiece receives. For example, a faster scanning speed reduces the time it takes the ion beam to pass through an area, thereby reducing the beam current in that area. A slower scanning speed allows more ions to be implanted in the area.

[0005] Ideally, the scan speed of the ion beam would be uniform. However, position-dependent variations exist. For example, the beam current may be lower at the edge of a workpiece than in the center of the workpiece. To compensate for this, the scanner may move slower near the edge of the workpiece. Therefore, in some embodiments, the beam current is profiled to generate data, which may be in the form of a graph or table showing the beam current as a function of position. This data may then be used to adjust the scan speed to provide a uniform current across the workpiece.

[0006] However, in addition to position-dependent variations, there may also be non-reproducible variations that occur during this profiling, and if such non-reproducible variations are used to adjust the scanning speed, the final results may not be optimal.

[0007] Therefore, it would be advantageous to have a system and method for generating a beam current profile that contains only position-dependent variations and using this beam current profile to adjust the speed of a scanner. Summary of the Invention

[0008] A system and method for generating a beam current profile that eliminates position-independent variations is disclosed. The system includes two Faraday sensors. One of the Faraday sensors is moved across the ion beam, while the second remains at or near a specific location. A reference Faraday sensor is used to measure the beam current variation over time, while the movable Faraday sensor measures both the position-dependent variation and the time-dependent variation. By combining these measurements, the actual position-dependent variation of the scanning ion beam can be determined. The resulting beam current profile can then be used to control the scan speed of an electrostatic or magnetic scanner.

[0009] According to one embodiment, an ion implantation system is disclosed that includes an ion source from which a spot beam is extracted, a scanner for scanning the spot beam in a first direction to result in divergent ion trajectory paths, an angle corrector for modifying the divergent ion trajectory paths to result in a substantially parallel scanned ion beam path, a mobile current measurement device that moves in the first direction and measures current as a function of position in the first direction, referred to as a movable position current measurement, where the movable position current measurement includes position-dependent variation and variation over time, a reference current measurement device that is used to generate a reference position current measurement including the variation over time, and a controller, wherein the controller uses the movable position current measurement and the reference position current measurement to generate a corrected beam current profile. In some embodiments, the speed at which the scanner scans the spot beam is determined by a scan speed profile, and the controller uses the corrected beam current profile to generate the scan speed profile used by the scanner. In some embodiments, the corrected beam current profile is generated by subtracting the reference position current measurement from the movable position current measurement for all positions in the first direction. In some embodiments, the corrected beam current profile is generated by normalizing the reference position current measurements and the movable position current measurements and using the normalized values ​​to generate the corrected beam current profile. In some embodiments, the controller calculates an average value of the reference position current measurements and subtracts this average value from each of the reference position current measurements to generate the beam current profile including the time variation. In some embodiments, the corrected beam current profile is generated by subtracting the beam current profile including the time variation from the movable position current measurements for all positions in the first direction. In certain embodiments, the movable current measurement device is a Faraday sensor. In some embodiments, the reference current measurement device is a Faraday sensor.In some embodiments, the scanned ion beam is wider than the width of the workpiece being implanted, and the reference current measuring device is positioned in the path of the scanned ion beam outside of the portion of the scanned ion beam that strikes the workpiece. In some embodiments, the reference current measuring device is positioned at a fixed position while the movable current measuring device moves across the scanned ion beam in a first direction. In some embodiments, the variation over time in the corrected beam current profile is reduced by at least 90% compared to a beam current profile generated using only movable position current measurements.

[0010] According to another embodiment, a method for tuning an ion beam to achieve a target uniformity is disclosed, the method including: scanning an ion beam in a first direction with a constant scan speed profile to produce a scanned ion beam having position-dependent and time-dependent variations; measuring the current of the scanned ion beam using two current measuring devices, a first of the two current measuring devices being a movable current measuring device that moves across the ion beam in the first direction; combining the current measurements from the two current measuring devices to produce a corrected beam current profile, the corrected beam current profile having reduced time-dependent variations compared to a beam current profile obtained using only the movable current measuring device; and comparing the uniformity of the corrected beam current profile to a target uniformity. and if the uniformity of the corrected beam current profile is inferior to the target uniformity, inputting the corrected beam current profile into a tuning algorithm, where the tuning algorithm generates a new scan speed profile based on the corrected beam current profile. In some embodiments, the scanning, measuring, using, comparing, and inputting are repeated until the uniformity meets the target uniformity. In some embodiments, the measurements from the two current measuring devices are normalized before being combined to generate the corrected beam current profile. In some embodiments, the second of the two current measuring devices remains stationary during the measurement. In certain embodiments, the measurement from the first of the two current measuring devices is referred to as a movable position current measurement and the measurement from the second of the two current measuring devices is referred to as a reference position current measurement, and the combining includes normalizing the reference position current measurement and the movable position current measurement and using the normalized values ​​to generate the corrected beam current profile. In certain embodiments, measurements from a first of the two current measurement devices are referred to as movable position current measurements and measurements from a second of the two current measurement devices are referred to as reference position current measurements, and combining includes calculating an average value of the reference position current measurements and subtracting this average value from each of the reference position current measurements to generate a beam current profile including the time variation. In some further embodiments, combining further includes subtracting the beam current profile including the time variation from the movable position current measurements for all positions in the first direction. In some further embodiments, combining further includes normalizing the beam current profile including the time variation and the movable position current measurements before subtracting.

[0011] For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference. [Brief explanation of the drawings]

[0012] [Figure 1A] 1 is an ion implanter utilizing a spot beam, according to one embodiment. [Figure 1B] The position of the current measuring device is shown in relation to the direction of the scanning ion beam. [Figures 2A-2C] 1 shows the beam current profile and the corrected beam current profile displayed for the movable current measuring device and the reference current measuring device, respectively. [Figure 3] 1 illustrates the operation of a controller during a tuning process, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Figure 1A shows a spot beam ion implantation system that may be used to implant ions into a workpiece using a spot beam, according to one embodiment, and Figure 1B shows a view of a current measurement device looking in the direction of a scanning ion beam.

[0014] The spot beam ion implantation system includes an ion source 100, which includes a plurality of chamber walls defining an ion source chamber. In certain embodiments, the ion source 100 may be an RF ion source. In this embodiment, an RF antenna may be positioned in contact with a dielectric window. The dielectric window may comprise part or all of one of the chamber walls. The RF antenna may include a conductive material (such as copper). An RF power supply is electrically connected to the RF antenna. The RF power supply may provide an RF voltage to the RF antenna. The power provided by the RF power supply may be between 0.1 kW and 10 kW and may be at any suitable frequency (such as between 1 MHz and 100 MHz). Furthermore, the power provided by the RF power supply may be pulsed.

[0015] In another embodiment, a cathode is positioned within the ion source chamber. A filament is positioned behind the cathode and emits electrons when a voltage is applied. These electrons are attracted to the cathode, which then emits electrons into the ion source chamber. This cathode may be referred to as an indirectly heated cathode (IHC) because it is indirectly heated by the electrons emitted from the filament.

[0016] Other embodiments are possible, for example, the plasma may be generated in various ways, such as by a Bernas-type ion source, a capacitively coupled plasma (CCP) source, a microwave, or an ECR (electron cyclotron resonance) ion source, etc. This disclosure is not limited to the manner in which the plasma is generated.

[0017] One chamber wall (referred to as the extraction plate) includes an extraction aperture. The extraction aperture may be an opening through which ions 1 generated in the ion source chamber are extracted and directed toward the workpiece 10. The extraction aperture may be any suitable shape. In certain embodiments, the extraction aperture may be oval or rectangular.

[0018] A source filter 110 is positioned adjacent the exterior of the extraction aperture of the ion source 100 .

[0019] A mass analyzer 120 is positioned downstream of the source filter 110. An acceleration / deceleration column 115 is positioned between the source filter 110 and the mass analyzer 120. The mass analyzer 120 uses a magnetic field to guide the path of the extracted ions 1. The magnetic field affects the flight path of the ions according to their mass and charge. A mass resolving device 130 having a resolving aperture 131 is positioned at the output (or distal end) of the mass analyzer 120. By appropriately selecting the magnetic field, only ions 1 having a selected mass and charge will be directed through the resolving aperture 131. Other ions will collide with the mass resolving device 130 or the walls of the mass analyzer 120 and will not enter further into the system. The ions that pass through the mass resolving device 130 may form a spot beam.

[0020] The spot beam then enters the scanner 140, which is located downstream of the mass resolving device 130. The scanner 140 fans the spot beam into multiple branched ion beamlets. In other words, the scanner 140 creates branched ion trajectory paths. The scanner 140 may be electrostatic or magnetic. The scanner 140 may include spaced-apart scan plates connected to a scan generator. The scan generator applies a scan voltage waveform, such as a sawtooth waveform, to scan the ion beam according to the electric field between the scan plates. The angle corrector 150 is designed to deflect ions in the scanned ion beam to generate the scanned ion beam 2 with parallel ion trajectories, thereby focusing the scanned ion beam. Specifically, the angle corrector 150 is used to change the branched ion trajectory paths to make the scanned ion beam 2 substantially parallel. In particular, the angle corrector 150 may include spaced apart magnetic pole pieces 151 defining a gap, and magnet coils (not shown) coupled to a power supply 152. The scanned ion beam 2 passes through the gap between the magnetic pole pieces 151 and is deflected according to the magnetic field in the gap. The magnetic field may be adjusted by varying the current through the magnet coils. Beam scanning and beam focusing are performed in a selected plane (such as the horizontal plane).

[0021] A workpiece 10 is placed in a movable workpiece holder 160 .

[0022] In certain embodiments, the forward direction of the ion beam is referred to as the Z direction. The horizontal direction perpendicular to this direction may be referred to as the first direction or X direction, while the vertical direction perpendicular to the Z direction may be referred to as the second direction or Y direction. In this example, it is assumed that the scanner 140 scans the spot beam in the first direction while the movable workpiece holder 160 translates in the second direction. The speed at which the scanner 140 scans the spot beam in the first direction may be referred to as the beam scan speed or simply the scan speed.

[0023] Thus, during operation, the movable workpiece holder 160 moves in the second direction from a first position, which may be above the scanning ion beam 2, to a second position, which may be below the scanning ion beam 2. The movable workpiece holder 160 then moves from the second position back to the first position, while the spot beam is being scanned in the first direction to ensure that the entire workpiece 10 is exposed to the spot beam.

[0024] A mobile current measuring device 170 is positioned proximate to the mobile workpiece holder 160. In certain embodiments, the mobile current measuring device 170 may be positioned within a plane 161 of the mobile workpiece holder 160 to measure the actual beam current impinging on the workpiece 10, as shown in FIG. 1A . In some embodiments, the mobile workpiece holder 160 is moved to a position out of the path of the scanning ion beam 2 while the mobile current measuring device 170 moves along the plane 161 of the mobile workpiece holder 160. The mobile current measuring device 170 may be a Faraday sensor or other suitable sensor. The mobile current measuring device 170 is configured to move in a first direction across the scanning ion beam 2. This mobile current measuring device 170 may also be referred to as a profiler Faraday sensor.

[0025] A reference current measuring device 175 may also be positioned within the path of the scanned ion beam 2. Unlike the mobile current measuring device 170, this device remains at or near one position while measurements are being taken. In some embodiments, the reference current measuring device 175 is stationary during the measurement process. In some embodiments, the reference current measuring device 175 is positioned on the same plane as the mobile current measuring device 170. In other embodiments, the reference current measuring device 175 may be positioned elsewhere. In certain embodiments, as can be seen in FIG. 1B , the scanned ion beam 2 may be wider than the workpiece 10. The reference current measuring device 175 may be positioned within the path of the scanned ion beam 2 but outside the area where the workpiece 10 is located. In this way, the mobile current measuring device 170 can move across the entire width of the workpiece without interfering with the reference current measuring device 175. FIG. 1B also shows an aperture 174, which is used to limit the width of the scanned ion beam 2 in the second or Y direction.

[0026] A controller 180 is also utilized to control the system. The controller 180 includes a processing unit 181 and an associated memory device 182. The memory device 182 contains instructions 183 that, when executed by the processing unit, enable the system to perform the functions described herein. The memory device 182 may be any non-transitory storage medium, including non-volatile memory such as flash ROM, electrically erasable ROM, or other suitable devices. In other embodiments, the memory device 182 may be volatile memory (such as RAM or DRAM). In certain embodiments, the controller 180 may be a general-purpose computer, an embedded processor, or a specially designed microcontroller. The actual implementation of the controller 180 is not limited by this disclosure. The controller 180 may be in communication with the scanner 140, the mobile current measuring device 170, and the reference current measuring device 175, and may be configured to vary the scanning speed of the scanner 140 based on data collected from these two current measuring devices.

[0027] During the tuning process, the movable workpiece holder 160 may be moved out of the path of the scanning ion beam 2. Ions 1 are extracted from the ion source 100 and travel along a path that ultimately produces the scanning ion beam 2. Initially, the scanner 140 may be configured by the controller 180 to utilize a constant scan speed profile.

[0028] The mobile current measuring device 170 is then moved along a first direction to measure the collected beam current as a function of position in the first direction. In some embodiments, the mobile current measuring device 170 may move at a speed between 1 mm / sec and 320 mm / sec. This movement of the mobile current measuring device 170 allows for the generation of data correlating the beam current with the workpiece position in the first direction. FIG. 2A shows one such data set represented graphically. Note that this graph is merely illustrative of the data collected by the mobile current measuring device 170, and other formats may be generated. The horizontal axis represents position on the workpiece, with the center of the workpiece designated as 0 mm, and the distance in each direction from this point is measured. Note in FIG. 2A that there are areas where the beam current reaches local maxima (e.g., at −140 mm, 0 mm, and 120 mm). In addition, there are also areas where the beam current reaches local minima (e.g., at −60 mm).

[0029] While the mobile current measuring device 170 is moving along the first direction, the reference current measuring device 175 is also operating to measure the beam current. Although the reference current measuring device 175 does not move, the resulting measurements correlate with the position of the mobile current measuring device 170. This can be seen visually in the graph of FIG. 2B. Note that the horizontal axis represents the position of the mobile current measuring device 170 at the time the current measurement was taken by the reference current measuring device 175. Again, note that this graph is merely illustrative of the data collected by the reference current measuring device 175, and that other formats may be generated. Note that for purposes of illustration, it is assumed that the scanning ion beam 2 has a sinusoidal fluctuation. Because the reference current measuring device 175 remains in one position, this fluctuation is time-varying and therefore not reproducible.

[0030] The data collected by the reference current measuring device 175 indicates not only the current at the specific position where the reference current measuring device 175 is located, but also the variation of that current over time. Therefore, if the currents collected by the reference current measuring device 175 are averaged as the movable current measuring device 170 moves throughout the first direction, the result will indicate not only the current at the specific position where the reference current measuring device 175 is located, but also its average variation over time. In other words, each current measured by the reference current measuring device 175 can be expressed as a position-dependent current obtained at position x (where x is the location of the reference current measuring device in the first direction) and its variation over time based on time. Similarly, the average current measured by the reference current measuring device 175 can be expressed as a position-dependent current obtained at position x and its average variation over time across the entire scan. Therefore, when the average current measured by the reference current measuring device 175 is subtracted from each individual current measurement, the resulting beam current profile includes the variation over time. In some embodiments, the position-dependent variation is completely eliminated.

[0031] Thus, when the mobile current measuring device 170 is in multiple different positions, the reference current measuring device 175 collects data at multiple time points. The multiple data points collected by the reference current measuring device 175 are referred to as reference position current measurements, sometimes referred to as RC(x). The current values ​​collected by the reference current measuring device 175 during the scan are then TIFF2025529088000002.tif6170 is subtracted from each of the reference position current measurements to obtain results that vary only over time. These results are called adjusted reference position current measurements, or ARC(x), TIFF2025529088000003.tif6170 In other words, the difference between the reference position current measurement and the adjusted reference position current measurement is a constant offset, and this constant offset is the average value of all of the reference position current measurements.

[0032] Subtracting this time variation (i.e., the adjusted reference position current measurement) from the data collected by the mobile current measuring device 170 provides a more accurate representation of the relationship between beam current and X position. Figure 2C shows the graph shown in Figure 2A with the time variation detected using the reference current measuring device 175 removed.

[0033] In one embodiment, the data collected by the reference current measuring device 175 is simply subtracted from the data collected by the mobile current measuring device. In other words, for each position in the first direction, the reference position current measurement is subtracted from the data collected by the mobile current measuring device. This removes time-dependent variations, but all results are offset by the position-dependent current observed by the reference current measuring device 175. In this embodiment, the correction current (CC) is: CC(x)=MC(x)-RC(x) It can be defined as:

[0034] Alternatively, a reference position current measurement, referred to as an adjusted reference position current measurement or ARC(x) (x is the X position of the mobile current measuring device 170 in the first direction at the time of measurement), calculated based on data collected by the reference current measuring device 175, may be subtracted from the data collected by the mobile current measuring device 170. Specifically, the data collected by the mobile current measuring device 170 may be referred to as a mobile position current measurement or MC(x). Thus, in one embodiment, for all x within the range of the scanner 140, the corrected current (CC) is: CC(x)=MC(x)-ARC(x) It can be defined as:

[0035] In another embodiment, the gain or location of the current measuring devices may be such that the current measured by each current measuring device is not on the same scale. For example, if the reference current measuring device 175 is further upstream (closer to the scanner 140 and further from the workpiece 10) than the mobile current measuring device 170, it may collect more current than the mobile current measuring device 170. In this embodiment, it may be advantageous to normalize the measurements from the two different current measuring devices. For example, the data from the reference current measuring device 175 may be normalized to represent the change from the average. Specifically, the normalized change over time as a function of X position in the first direction (ΔNormRC) may be expressed as: TIFF2025529088000004.tif9170 formula, where RC(x) is the arithmetic mean value of the reference current measurements taken for all values ​​of TIFF2025529088000005.tif6170x, and RC(x) is the reference position current measurement taken when the mobile current measuring device is at position x in the first direction. Note that by subtracting the arithmetic mean value, the numerator now represents only the time variations of the scanning ion beam 2.

[0036] This value may be combined with the value collected by the mobile current measuring device 170 as follows: TIFF2025529088000006.tif6170 formula, This is the arithmetic mean value of the moving position current measurements for all values ​​of TIFF2025529088000007.tif6170X.

[0037] Of course, these calculations could be done differently. For example, the following sequence of operations could be done, resulting in the same equation: TIFF2025529088000008.tif33170

[0038] 2C shows a corrected current profile as a function of X in which the time variation shown in FIG. 2B has been removed from the current profile collected by the mobile current measurement device 170. This corrected current profile can then be used to adjust the scan speed of the scanner 140.

[0039] In other words, the mobile current measuring device 170 collects data that includes both position-dependent information and non-repeatable time-dependent information. Specifically, there is position-dependent variation and time-dependent variation. In contrast, the reference current measuring device 175 collects data that includes position-dependent variation from only one position (which may be subtracted) and non-repeatable time-dependent information, also known as time-dependent variation. By removing the non-repeatable time-dependent information from the data collected from the mobile current measuring device 170, a corrected current profile that includes only position-dependent information may be generated.

[0040] The above description states that the reference current measurement device 175 may be located at a fixed location. However, other embodiments are possible. For example, small variations in a first direction may not affect the position-dependent component of the measurement. For example, movement of less than 5 mm in either the positive or negative X direction may not adversely affect the accuracy of the reference measurement.

[0041] 3 illustrates the operation of the controller 180 during the tuning process. First, as shown in box 300, the scanner 140 is configured to utilize a uniform scan speed. Then, as shown in box 310, the mobile current measuring device 170 is moved in a first direction across the scanning ion beam 2 to collect data regarding the beam volume as a function of position in the first direction. As discussed above, this data may be referred to as mobile position current data. Simultaneously, the reference current measuring device 175 measures the current multiple times and associates each current measurement with the X position of the mobile current measuring device 170 in the first direction. This data may be referred to as reference position current data and includes the RC(x) function discussed above. As discussed above, the current measured by the reference current measuring device 175 is used to obtain adjusted reference position current data. TIFF2025529088000009.tif6170 can be subtracted from the reference position current data.

[0042] Next, as described above and shown in box 320, a corrected beam current profile is generated based on the data collected from the mobile current measuring device 170 and the reference current measuring device 175. This may involve simply subtracting the time-varying variation obtained using the reference current measuring device 175 from the data from the mobile current measuring device 170, or generating a normalized value and performing the conversion using the normalized value. In some embodiments, the time-varying variation has already been removed from the corrected beam current profile. In other embodiments, the time-varying variation is significantly reduced in the corrected beam current profile. In other words, the corrected beam current profile has reduced time-varying variation compared to a beam current profile generated using only the mobile current measuring device 170. In some embodiments, more than 90% of the time-varying variation is removed from the corrected beam current profile compared to a beam current profile generated using only the mobile current measuring device 170.

[0043] This corrected beam current profile is then analyzed to determine whether it meets uniformity limits. For example, it may be desirable to have uniformity within 0.5% across the width of the scanned ion beam 2. In this disclosure, uniformity is defined as the standard deviation of the scanned ion beam profile divided by the mean value of the scanned ion beam profile multiplied by 100%. If the uniformity threshold is met, the tuning process is complete, as shown in box 350.

[0044] If the uniformity threshold is not met, then this corrected beam current profile is fed into a tuning algorithm to adjust the scan speed profile, as shown in box 330 .

[0045] The tuning algorithm may be a PID (proportional-integral-derivative) controller that uses the corrected beam current profile to calculate a scan speed profile. The scan speed profile represents the scan speed of the scanner 140 as a function of the first direction. As an example, FIG. 2C shows a corrected beam current profile that may be provided to the tuning algorithm. In response, the tuning algorithm may generate an updated scan speed profile. The scan profile may resemble the beam current profile in that areas with high beam current have a higher scan speed. In contrast, locations with low beam current have a lower scan speed. The actual implementation of the tuning algorithm is not limited by this disclosure, and those skilled in the art may implement the tuning algorithm in other ways. For example, a PI controller or a PD controller may be used.

[0046] The updated scan speed profile determined by the tuning algorithm is then provided to scanner 140, as shown in box 340. The sequence shown in boxes 310-350 is then repeated until the uniformity threshold is met or the maximum number of iterations is reached.

[0047] The embodiments described hereinabove may have a number of advantages. First, the corrected beam current profile encompasses only position-dependent variations. Such variations are expected to be more consistent and highly repeatable. As a result, the number of iterations required to find a scan speed profile that meets a uniformity threshold may be reduced. This is particularly true for ion implantation systems with unstable ion sources.

[0048] Additionally, the reproducibility of the injection system may be improved because the tuning algorithm does not attempt to correct for non-reproducible variations.

[0049] Finally, there is no drawback to implementing this method in an ion implantation system that does not have time variations, in which case the current measured by the reference current measuring device 175 will be relatively uniform across the width of the scanned ion beam 2. As a result, the beam current profile obtained by the mobile current measuring device 170 will be largely uncorrected.

[0050] The present disclosure is not limited in scope by the specific embodiments described herein. Indeed, in addition to the embodiments of and modifications to the present disclosure, various other embodiments and modifications besides those described herein will become apparent to those skilled in the art from the above description and the accompanying drawings. Accordingly, such other embodiments and modifications are intended to be included within the scope of the present disclosure. Furthermore, while the present disclosure has been described herein in the context of particular implementations in particular environments for particular purposes, those skilled in the art will recognize that the usefulness of the present disclosure is not limited to such contexts, and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in light of the full scope and nature of the present disclosure as described herein.

Claims

1. an ion source from which a spot beam is extracted; a scanner for scanning the spot beam in a first direction to result in divergent ion trajectory paths; an angle corrector for modifying the divergent ion trajectory paths into a substantially parallel scanned ion beam path; a mobile current measuring device that moves in the first direction and measures current as a function of position in the first direction, referred to as a mobile position current measurement, the mobile position current measurement including position dependent variation and variation over time; a reference current measurement device used to generate a reference position current measurement that includes variations over time; A controller; 1. An ion implantation system comprising: the controller generates a corrected beam current profile using the movable position current measurements and the reference position current measurements. Ion implantation system.

2. 2. The ion implantation system of claim 1, wherein a speed at which the scanner scans the spot beam is determined by a scan speed profile, and wherein the controller uses the corrected beam current profile to generate the scan speed profile used by the scanner.

3. 2. The ion implantation system of claim 1, wherein the corrected beam current profile is generated by subtracting the reference position current measurement from the movable position current measurement for all positions in the first direction.

4. 2. The ion implantation system of claim 1, wherein the corrected beam current profile is generated by normalizing the reference position current measurement and the movable position current measurement, and using the normalized values ​​to generate the corrected beam current profile.

5. 2. The ion implantation system of claim 1, wherein the controller calculates an average value of the reference position current measurements and subtracts the average value from each of the reference position current measurements to generate a beam current profile including variations over time.

6. 6. The ion implantation system of claim 5, wherein the corrected beam current profile is generated by subtracting a beam current profile including the time variation from the movable position current measurements for all positions in the first direction.

7. 2. The ion implantation system of claim 1, wherein the mobile current measuring device is a Faraday sensor.

8. 2. The ion implantation system of claim 1, wherein the reference current measuring device is a Faraday sensor.

9. 10. The ion implantation system of claim 1, wherein the scanning ion beam is wider than a width of a workpiece being implanted, and the reference current measuring device is positioned within the path of the scanning ion beam outside a portion of the scanning ion beam that strikes the workpiece.

10. 2. The ion implantation system of claim 1, wherein the reference current measuring device is positioned at a fixed location while the movable current measuring device moves across the scanning ion beam in the first direction.

11. 10. The ion implantation system of claim 1, wherein the time-dependent variation in the corrected beam current profile is reduced by at least 90% compared to a beam current profile generated using only the movable position current measurements.

12. 1. A method for tuning an ion beam to achieve a target uniformity, comprising: scanning the ion beam in a first direction with a constant scan speed profile to produce a scanned ion beam having position dependent variation and time dependent variation; measuring the current of the scanned ion beam using two current measuring devices, a first of the two current measuring devices being a movable current measuring device that moves across the ion beam in the first direction; combining the current measurements from the two current measuring devices to generate a corrected beam current profile, the corrected beam current profile having reduced variation over time compared to a beam current profile obtained using only the movable current measuring device; comparing the corrected beam current profile uniformity to the target uniformity; and if the uniformity of the corrected beam current profile is less than the target uniformity, inputting the corrected beam current profile into a tuning algorithm, the tuning algorithm generating a new scan speed profile based on the corrected beam current profile. method.

13. 13. The method of claim 12, wherein the scanning, measuring, using, comparing, and inputting are repeated until the uniformity of the corrected beam current profile meets the target uniformity.

14. The method of claim 12 , wherein measurements from the two current measuring devices are normalized before being combined to generate the corrected beam current profile.

15. The method of claim 12 , wherein a second of the two current measuring devices remains stationary during the measuring.

16. a measurement from the first of the two current measuring devices referred to as a movable position current measurement and a measurement from the second of the two current measuring devices referred to as a reference position current measurement, and said combining includes: normalizing the reference position current measurement and the movable position current measurement; and generating the corrected beam current profile using the normalized value.

17. a measurement from the first of the two current measuring devices referred to as a movable position current measurement and a measurement from the second of the two current measuring devices referred to as a reference position current measurement, and said combining includes: calculating an average value of the reference position current measurements; and subtracting the average value from each of the reference position current measurements to generate a beam current profile including variations over time.

18. 18. The method of claim 17, wherein said combining further comprises subtracting the beam current profile including the time variation from the movable position current measurements for all positions in the first direction.

19. 20. The method of claim 18, wherein said combining further comprises normalizing said beam current profile including said time variation and said movable position current measurement prior to said subtracting.

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