Abstract:
An ion beam scanning assembly includes a set of scanning electrodes defining a gap to accept an ion beam and scan the ion beam in a first plane, and a multipole electrostatic lens system comprising a plurality of electrodes arranged along a portion of a path of travel of the ion beam bounded by the pair of scanning electrodes, the multipole electrostatic lens system configured to shape the ion beam in a direction perpendicular to the first plane.

Description:
FIELD 
     This invention relates to an ion implantation apparatus, more particularly, to lens components of an ion implanter. 
     BACKGROUND 
     Present day manufacturing for semiconductor electronics, solar cells, and other technology relies on ion implanter systems for doping or otherwise modifying silicon and other types of substrates. A typical ion implanter system performs the doping by generating an ion beam and steering it into a substrate so that the ions come to rest beneath the surface. Different types of ion implantation systems have been developed for different applications. High-current ion implanter systems are one type of implanter system that is widely used in semiconductor manufacturing. Such implanter systems typically produce currents up to 25 milliamperes (mA) and may be employed to efficiently introduce high doses of implanted species into a substrate. 
     Medium-current ion implanter systems have been developed to produce an ion beam having an intensity in the range of one microampere to about five mA, at energies between 2 kilo electron volts (keV) and 900 keV. These types of ion implantation systems may be especially useful to introduce dopant into a substrate in concentration ranges of about 1E13 to 5E14 or so. Generally, medium current implanter systems have been developed to operate by scanning a spot beam across a wafer In particular, for many applications, during ion implantation, it is desirable to achieve a uniform ion dose or beam current profile along the scan path. One approach to achieve this is to scan a spot beam in one plane while moving a target wafer in a direction orthogonal the plane to treat an entire surface of the target wafer. Scanning of an ion beam may be accomplished by the use of electrostatic scanners that are employed to controllably deflect the ion beam from its normal trajectory to span a larger area by changing the electric fields in a direction perpendicular to the direction of travel of the ion beam. The strength of the scanner field determines the total deflection from the normal path of the ion beam, hence the ion beam may be scanned by changing the electric field strength of the scanner elements. 
       FIG. 1   a  depicts an ion implantation system  100  that is arranged according to the prior art. As illustrated, the ion implantation system  100  includes an ion source  102 , which typically is used to generate positive ions for implantation. The positive ions are provided as an ion beam that is deflected, accelerated, decelerated, shaped, and/or scanned between its emergence from the ion source and a substrate to be processed. An ion beam  120  is illustrated in  FIG. 1  by a central ray trajectory (CRT). However, it will be appreciated by those of skill in the art, that an ion beam has a finite width, height, and shape, which may vary along the beam path between the ion source  102  and substrate  112 .  FIG. 1   a  further depicts a mass analyzer  104  that deflects the ion beam, an electrostatic scanner  106 , corrector magnet  108 , and end station  110  that may manipulate the substrate  112 . In known systems, the electrostatic scanner  106  generates an electric field that is generally perpendicular to the direction of travel of ion beam  120  as it passes through the electrostatic scanner  106 . 
       FIG. 1   b  illustrates a known scenario in which a spot beam is used to implant a substrate. In the example shown, the substrate  112  is a circular wafer, such as a silicon wafer.  FIG. 1   b  depicts a cross-section of the ion beam  120  projected onto the substrate  112 . In known systems, it is typical for a scanner, such as the electrostatic scanner  106 , to scan an ion beam along a direction, such as a direction  122  (shown as parallel to the X-axis of the Cartesian coordinate system illustrated), while the substrate  112  is independently translated along a second direction  124  (shown as parallel to the Y-axis), which may be perpendicular to the first direction. The action of translating the substrate along direction  124  together with the scanning of ion beam  120  along the direction  122  may allow the ion beam  120  to expose the entire substrate  112  to ions. In the example illustrated, the ion beam  120  is a spot beam having a height H 1  and width W 1 . 
     As shown in  FIG. 1   b , when the ion beam  120  is scanned along the direction  122  the ion beam  120  covers a scanned area  126 . Because of the size and shape of the ion beam  120  and shape of the substrate  112 , in order to ensure that all desired regions of the substrate  112  are exposed to the ion beam  120 , the ion beam  120  is typically scanned beyond the edge  128  of the substrate  112  as illustrated. For example, it may be necessary to scan the ion beam  120  past the edge  128  a distance comparable to or even larger than width W 1 , as suggested in  FIG. 1   b . The scanned area  126  may thus include a substantial region  130  (shown only along one side of the substrate  112  for clarity) that lies outside of the substrate  112  and represents a dose of ions that is “wasted,” that is, the ions in region  130  are not used to implant or otherwise treat the substrate  112 . 
     In addition, if the height H 1  of the ion beam  120  is not sufficiently large, implantation dose non-uniformities may result. It may be desirable to ensure that the height H 1  is not so large that ions strike beamline components such as pole pieces of corrector magnets that may be arranged to surround the ion beam  120 . However, if the value of H 1  is too small, the substrate  112  may be non-uniformly implanted when the substrate  112  is translated along the direction  124 . For example, an ion beam  120  may oscillate in the direction  122  when the substrate is located at position P 1 , leading to implantation in an area on the substrate  112  that corresponds to the portion of the scanned area  126  that impinges on the substrate  112 . The substrate  112  may then be stepped or scanned along the direction  124 , leading to successive areas of comparable size to scanned area  126  being exposed on the substrate  112  due to the action of the electrostatic scanner  106 . However, due to the finite dimension for the ion beam  120  along the direction  124 , that is height H 1 , there may be underlap or overlap of the successive areas exposed by the scanning of ion beam  120  along the direction  122 . 
     In order to improve uniformity in such ion implantation systems, it may be desirable to alter the beam size and or shape of an ion beam in cross-section. For example, extra lens elements may be added to the beamline to alter the beam shape, such as a lens to increase the beam spot size. However, the introduction of extra lens elements serves to increase the ion beam path length and to change the footprint of an ion implantation system, both of which are generally not desirable. In addition, the introduction of electrostatic scanners in series with components such as lens elements to shape the ion beam may create an increased region in which electrons are stripped from the ion beam. As is known, whenever electron are stripped or removed from a (positive) ion beam, the ion beam has a tendency to expand. This takes place due to the mutual repulsion of positive ions within the ion beam. The ion beam may be stripped of electrons anytime low energy electrons are attracted and accelerated out of the ion beam by a high positive potential applied to any of various beamline components. A result of beam expansion may include a reduction in beam current that can effectively be applied to a substrate. 
     What is needed is an improved method and apparatus to form more uniform beams in ion implantation systems, such as medium current ion implantation systems. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description, and is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter. 
     In one embodiment, an ion beam scanning assembly includes a set of scanning electrodes defining a gap to accept an ion beam and scan the ion beam in a first plane. A multipole electrostatic lens system is also included which comprises a plurality of electrodes arranged along a portion of a path of travel of the ion beam bounded by the pair of scanning electrodes. The multipole electrostatic lens system is configured to shape the ion beam in a direction perpendicular to the first plane. 
     In a further embodiment, a method of treating an ion beam may include generating one or more oscillating electric fields along a first plane perpendicular to the ion beam over a portion of an ion beam path of the ion beam; and applying a set of static electric fields along the portion of the ion beam path in a direction perpendicular to the first plane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a  depicts a known ion implantation system; 
         FIG. 1   b  depicts processing of a substrate using an ion beam according to the prior art; 
         FIG. 2  depicts an ion implantation system according to an embodiment of the disclosure; 
         FIG. 3   a  depicts an embodiment of an ion beam scanning assembly according to an embodiment of the disclosure; 
         FIG. 3   b  depicts exemplary waveforms of a set of oscillating voltages applied to an ion beam scanning assembly according to an embodiment of the disclosure; 
         FIG. 3   c  depicts further exemplary waveforms of a set of oscillating voltages applied to an ion beam scanning assembly according to an embodiment of the disclosure; 
         FIG. 3   d  depicts another embodiment of an ion beam scanning assembly according to an embodiment of the disclosure; 
         FIG. 4   a  depicts a front view of an ion beam scanning assembly in one scenario of processing an ion beam consistent with the present embodiments; 
         FIG. 4   b  depicts a back view of the ion beam scanning assembly in the scenario of  FIG. 4   a;    
         FIGS. 4   c  and  4   d  depict exemplary waveforms corresponding to elements of the ion beam scanning assembly depicted in  FIGS. 4   a  and  4   b  respectively; 
         FIG. 4   e  depicts one example of processing a substrate using the embodiment of  FIGS. 4   a ,  4   b;    
         FIG. 5   a  depicts a front view of an ion beam scanning assembly in one scenario of processing an ion beam consistent with the present embodiments; 
         FIG. 5   b  depicts a back view of the ion beam scanning assembly in the scenario of  FIG. 4   a;    
         FIGS. 5   c  and  5   d  depict exemplary waveforms corresponding to elements of the ion beam scanning assembly depicted in  FIGS. 5   a  and  5   b  respectively; and 
         FIG. 5   e  depicts one example of processing a substrate using the embodiment of  FIGS. 5   a ,  5   b.    
     
    
    
     DETAILED DESCRIPTION 
     The embodiments described herein provide apparatus and methods for treating an ion beam in an ion implantation system. Examples of an ion implantation system include a beamline ion implantation system. The ion implantation systems covered by the present-embodiments include those that generate “spot ion beams” that have a cross-section that has the general shape of a spot. In the present embodiments, a beam shaper component (or system) is added to an electrostatic scanner component that contains a set of scanning electrodes to form an ion beam scanning assembly that treats an ion beam so that performance of the ion implantation apparatus is improved without requiring an additional footprint for the beam shaper component. 
       FIG. 2  depicts an ion implantation system  200  according to an embodiment of the disclosure. The ion implantation system  200  may include conventional components including the ion source  102 , magnetic analyzer  104 , corrector magnet  108  and substrate stage  110 . In various embodiments the ion implantation system  100  generates a spot type ion beam that is scanned by an electrostatic scanner component to provide ion implantation over a substrate that is larger than the cross-sectional area of the spot type ion beam. In the example of  FIG. 2 , an ion beam electrostatic scanner/ion beam shaper, or simply an ion beam scanning assembly  202  is disposed along the beamline  204  at a point between the magnetic analyzer  104  and corrector magnet  108 . The ion beam scanning assembly  202  is arranged to receive an ion beam  206  generated by the ion source  102  and to produce a scanned and shaped beam that may be further manipulated, such as by the corrector magnet  108  before impinging on the substrate  112 . 
     In particular, the magnetic analyzer  104  may remove unwanted ions from the ion beam  206 . The magnetic analyzer  104  acts according to known principles to separate charged species of the ion beam  206  as the ion beam  206  emerges from the ion source  102 . The separation is performed according to a ratio of the mass to charge of the particular species in the ion beam  206  so that a charged particles (ions) of a desired mass/charge ratio may be selected to emerge from an exit of the magnetic analyzer  104 , which directs the ion beam  206  in a different direction that its original direction. In this manner, the analyzed ion beam  206   a  is directed toward the ion beam scanning assembly  202 . 
     As detailed below, the ion beam scanning assembly  202  manipulates the analyzed ion beam  206   a  to produce a processed ion beam  206   b  whose shape, size, and/or density, among other factors, are altered to improve the characteristics on the ion beam  206 . In various embodiments, the ion beam scanning assembly  202  combines the actions of an electrostatic scanner with that of a multipole electrostatic lens that modifies the ion beam spot size, spot shape, and/or ion density of the analyzed ion beam  206   a  as it traverses the ion beam scanning assembly  202 . In particular embodiments detailed with respect to the figures to follow, the ion beam scanning assembly  202  constitutes a quadrupole electrostatic lens that is superimposed on an electrostatic scanner. In other words, the components of the quadrupole electrostatic lens and the electrostatic scanner bound the ion beam  206  along the same portion of the beam path traversed by ion beam  206 . 
       FIG. 3   a  depicts a perspective view of an embodiment of an ion beam scanning assembly according to an embodiment of the disclosure. In  FIG. 3   a , the ion beam scanning assembly  300  includes a quadrupole electrostatic lens system  320  that includes a front lens  302  and back lens  308 . The front lens  302  includes two pairs of opposed electrodes  304 ,  306  and  314   a ,  316   a , while the back lens  308  includes another two pairs of opposed electrodes  310 ,  312  and  314   b ,  316   b . The ion beam scanning assembly  300  also contains an electrostatic scanner component embodied as a set of scanning electrodes  318 . In the embodiment depicted in FIG.  3   a , the set of scanning electrodes  318  includes two pairs of plates or scanning electrodes  314   a ,  316   a  and  314   b ,  316   b . As shown in  FIG. 3   a , the electrodes  304 ,  306 ,  314   a ,  316   a ,  310 ,  312 ,  341   b ,  316   b  of the quadrupole electrostatic lens system  320  and scanning electrodes  314   a ,  314   b ,  316   a ,  316   b  of the set of scanning electrodes  318  are mutually configured to define a region  330  to transmit an ion beam (not shown) therethrough. When an ion beam passes through region  330  a set of voltages may be applied to the electrodes  304 ,  306 ,  310 ,  312  and  314   a ,  314   b ,  316   a ,  316   b  to shape and scan the ion beam. These voltages may be adjusted to optimize the beam shape and the magnitude of the beam deflection based on beam energy and ion species. 
     As additionally shown  FIG. 3   a , the scanning electrodes  314   a ,  314   b ,  316   a ,  316   b  of the set of scanning electrodes  318  are connected to respective voltage sources V 3 , V 3 ′, V 4  and V 4 ′, which are applied as AC signals. As further illustrated in  FIGS. 3   b , and  3   c  each of the AC voltages V 3 , V 3 ′, V 4  and V 4 ′ constitutes a respective voltage waveform  350 ,  352 ,  354 ,  356  that is composed of an oscillating voltage component, or simply oscillating voltage Vscan and a DC offset voltage Voffset. The oscillating voltages V 3 scan, V 3 ′scan, V 4 scan, V 4 ′scan fluctuate with the respect to their DC offset voltages V 3 offset, V 3 ′offset, V 4 offset and V 4 ′offset respectively. For example, the AC voltages V 3 , V 3 ′, V 4 , V 4 ′ applied to the scanning electrodes  314   a ,  314   b ,  316   a ,  316   b  may be adjusted in such way that the DC offset voltages V 3 offset, V 3 ′offset applied to the scanning electrodes  314   a ,  316   a  have same magnitude and polarity and the DC offset voltages V 4 offset, V 4 ′offset applied to the scanning electrodes  314   b ,  316   b  have same magnitude and polarity. Moreover, the oscillating voltages V 3 scan, V 3 ′scan applied to the scanning electrodes  314   a ,  316   a  may have same amplitude but opposite phase angle, and the oscillating voltages V 4 scan, V 4 ′scan applied to the scanning electrodes  314   b ,  316   b  may have same amplitude but opposite phase angle. In addition, the oscillating voltages V 3 scan, V 4 scan applied to the scanning electrodes  314   a ,  316   a  may have same phase angle and the oscillating voltages V 3 ′scan, V 4 ′scan applied to the scanning electrodes  314   b ,  316   b  have same phase angle. In this manner, an oscillating electric field is created along the X-direction where the direction and magnitude of the electric field varies with time. Because the X-direction is perpendicular to the direction of propagation of an ion beam traversing the region  330 , the ion beam will experience a time dependent deflection force that deflects the ion beam in an alternating fashion towards the scanning electrodes  314   a ,  314   b  on the one hand and the scanning electrodes  316   a ,  316   b  on the other hand. The oscillating voltages V 3 scan, V 3 ′scan, V 4 scan, V 4 ′scan applied to the scanning electrodes  314   a ,  314   b ,  316   a ,  316   b  may be adjusted in the range of +/−200V to +/−25 kV to optimize the magnitude of the beam deflection based on beam energy. In some embodiments, the ion beam may be deflected through an angle of about +/−10 degrees, while in other embodiments the ion beam may be deflected through an angle of up to about +/−20 degrees. Referring also to  FIG. 2 , this deflection may cause the ion beam to scan across the width W of a substrate  112 . 
     As further illustrated in  FIG. 3   a , each electrode  304 ,  306 ,  310 ,  312  is coupled to a respective voltage source (DC voltage generator) V 1  or V 2  to receive a potential (DC voltage). The DC voltage V 1  applied to the electrodes  304  and  306  may be adjusted in such way that V 1  has same magnitude but opposite polarity as V 3 offset and V 3 ′offset, the DC offset voltages applied to the scanning electrodes  314   a ,  316   a . The DC voltage V 2  applied to the electrodes  310  and  312  may be adjusted in such way that V 2  has same magnitude but opposite polarity as V 4 offset and V 4 ′offset, the DC offset voltages applied to the scanning electrodes  314   b ,  316   b . A first set of DC voltages V 1  applied to the electrodes  304 ,  306 , and V 3 offset, V 3 ′offset applied to the scanning electrodes  314   a ,  316   a  create a static electric field (not shown) that may form a first quadrupole electrostatic lens within the region  330 . A second set of DC voltages V 2  applied to the electrodes  310 ,  312 , and V 4 offset, V 4 ′offset applied to the scanning electrodes  314   b ,  316   b  create another static electric field (not shown) that may form a second quadrupole electrostatic lens within the region  330 . In particular, in the arrangement of  FIG. 3   a , the direction of propagation of an ion beam (not shown) is along the Z-axis. Accordingly, the quadrupole electrostatic lens system  320  including the first and the second quadrupole electrostatic lenses is formed to generate a set of electrical fields that are perpendicular to the direction of propagation of an ion beam to shape the ion beam as it traverses the region  330 . The first set of DC voltages V 1  applied to the electrodes  304 ,  306 , and V 3 offset, V 3 ′offset applied to the scanning electrodes  314   a ,  316   a  and the second set of DC voltages V 2  applied to the electrodes  310 ,  312 , and V 4 offset, V 4 ′offset applied to the scanning electrodes  314   b ,  316   b  may be adjusted coordinately in the range of −20 kV to +20 kV to optimize the beam shape based on beam energy and ion species. 
     In addition to scanning an ion beam the ion beam scanning assembly  300  shapes an ion beam by action of the electric fields provided by the quadrupole electrostatic lens system  320 . Accordingly, as the ion beam emerges from the ion beam scanning assembly  300  the ion beam may have a different shape, size and ion density as compared to the shape, size, and/or ion density of the ion beam before entry into the ion beam scanning assembly  300 . 
       FIG. 3   d  depicts a variant of the ion beam scanning assembly  300  of  FIG. 3   a . As illustrated in  FIG. 3   c , the scanning electrodes  314   b ,  316   b  of the set of scanning electrodes  318  have a flared shape as viewed along the Y-axis, such that the separation D between the scanning electrodes  314   b ,  316   b  is larger toward the substrate side  332  of the set of scanning electrodes  318  compared to the separation D on the ion source side  334 . As noted above, the voltage source V 3  may generate an AC signal that causes the polarity of voltage applied between the scanning electrodes  314   a ,  316   a  on the one hand and  316   a ,  316   b  on the other hand to switch so that a beam of ions (not shown) traversing the region  330  experiences a deflecting field whose direction alternates between the directions  336  and  338 . This alternating deflecting field may cause a beam of ions to fan out so as to trace a range of angles, such as +/−10 degrees or more with respect to direction of propagation of the ion beam. 
     Although  FIG. 3   c  depicts the ion beam scanning assembly  300  as constituting two sets of electrodes  304 ,  306 ,  314   a ,  316   a  and  310 ,  312 ,  315   b ,  316   b  in some variants, the ion beam scanning assembly  300  may contain a single set of electrodes or more than two sets of electrodes as in known electrostatic scanners and quadrupole electrostatic lenses. In various embodiments, the electric fields generated by the set of scanning electrodes  318  and the quadrupole electrostatic lens system  320  may be such that the cross-section of an ion beam traversing the region  330  is altered so that the shape of the cross-section of the ion beam at the ion source side  334  differs from that at the substrate side  332 . 
       FIG. 4   a  and  FIG. 4   b  together depict one scenario for processing (treating) an ion beam consistent with the present embodiments.  FIG. 4   b  depicts a back view of the ion beam scanning assembly  300  for the same scenario as illustrated in  FIG. 4   a .  FIGS. 4   c  and  4   d  depict exemplary waveforms  420 ,  422 , respectively, which correspond to elements of the ion beam scanning assembly depicted in  FIGS. 4   a  and  4   b  respectively. In particular, the waveforms  420 ,  422  are each composed of an oscillating voltage Vscan and a DC offset voltage Voffset as described above with respect to  FIGS. 3   b  and  3   c . In  FIG. 4   a , a front view of the ion beam scanning assembly  300  is illustrated looking downstream in a direction of travel of the ion beam. An ion beam  402  is shown in cross-section as it enters the ion beam scanning assembly  300  at the ion source side  334 . As shown in  FIG. 4   a , the ion beam  402  is a spot beam characterized by a height H 2  and width W 2 . As the ion beam  402  enters the ion beam scanning assembly  300 , the ion beam  402  experiences electric fields (E) that are generated by the various electrodes  304 ,  306 ,  310 ,  312 ,  314   a ,  314   b ,  316   a ,  316   b . The scanning electrodes  314   a ,  314   b ,  316   a ,  316   b  are coupled to AC voltages that generate an oscillating electric field along the direction  404  parallel to the X-axis of the Cartesian coordinate system shown. The oscillating electric field produced by the scanning electrodes  314   a ,  314   b ,  316   a ,  316   b  causes the position of the beam to vary with time as the ion beam  402  traverses the ion beam scanning assembly  300 , although  FIG. 4   a  illustrates only a single position of the ion beam  402 . 
     In some embodiments, the ion beam scanning assembly  300  is used to process an ion beam to be delivered to a substrate with ion energy of 2 keV to 900 keV. In some cases, the absolute value of voltage applied to the scanning electrodes  314   a ,  314   b ,  316   a ,  316   b  is in the range of 200 V to 35 kV. The embodiments are not limited in this context. In the example illustrated in  FIG. 4   a , fluctuating voltages applied to the scanning electrodes  314   a ,  314   b  on the one hand and  316   a ,  316   b  on the other hand is superimposed on a DC offset voltage of +10 kV. The absolute value of the peak voltage applied to the scanning electrodes  314   a ,  314   b ,  316   a ,  316   b  is 25 kV with respect to the offset voltage of +10 kV, which may deflect the ion beam  402  through a range of angles of about +/−10 degrees in some cases. As illustrated in  FIGS. 4   c  and  4   d , it should be noted that in  FIGS. 4   a  and  4   b , the +/−25 kV refers an oscillating voltage that fluctuates 25 kV with respect to the offset voltage of +10 kV, and that −/+25 kV refers a oscillating voltage having opposite phase angle with respect to the +/−25 kV. 
       FIG. 4   a  further illustrates an example in which a static DC voltage of −10 kV is applied to the electrodes  304 ,  306  that are coupled with the scanning electrodes  314   a ,  316   a  to form the front lens  302  of quadrupole electrostatic lens system  320 . Coupled with the DC offset voltage of +10 kV on scanning electrodes  314   a ,  316   a , the application of a negative voltage to the electrodes  304 ,  306  establishes a set of electric fields that exert a force on the ion beam  402  that tends to expand the ion beam  402  along the direction  406  that is perpendicular to the direction  404 . In this manner, the shape of the ion beam  402  in cross-section is altered as the ion beam  402  traverses the ion beam scanning assembly  300 . 
       FIG. 4   b  depicts a back view of the ion beam scanning assembly  300  facing upstream opposite the direction of travel of the ion beam  402  for the same scenario as illustrated in  FIG. 4   a . In the example illustrated, a static voltage of −10 kV is applied to the electrodes  310 ,  312  that are coupled with the scanning electrodes  314   b ,  316   b  to form the back lens  308  of quadrupole electrostatic lens system  320 . Coupled with the DC offset voltage of +10 kV on scanning electrodes  314   b ,  316   b , this application of negative voltage to the electrodes  310 ,  312  establishes another set of electric fields that further exerts a force on the ion beam  402  that tends to stretch the ion beam  402  along the direction  406  that is perpendicular to the direction  404 . In this manner, as shown in  FIG. 4   b , as the ion beam  402  emerges from the ion beam scanning assembly  300 , the ion beam  402  is elongated along the direction  406  in comparison to its shape when entering the ion beam scanning assembly  300  shown in  FIG. 4   a . Thus, the ion beam  402  emerges with a height H 3  that is greater than H 2  of the (incident) ion beam  402 . 
     One advantage provided by the embodiment of  FIGS. 4   a ,  4   b  is that the increased height H 3  of the ion beam  402  provides more uniform ion dose as successive areas of a substrate are exposed to the ion beam  402 . However, it is to be noted that the voltages applied to the ion beam scanning assembly  300  may be set so that the height H 3  is kept below a dimension where portions of the ion beam  402  strike downstream components of an ion implantation system such as pole pieces of an angle corrector.  FIG. 4   e  depicts one example of processing a substrate  112  using the embodiment of  FIGS. 4   a ,  4   b . There are shown two ion exposure areas  410 ,  412  that are formed when the ion beam  402  is electrostatically scanned using the scanning electrodes  314   a ,  314   b ,  316   a ,  316   b  while the substrate is positioned at two different positions along the direction  406 . Thus, the substrate  112  may be stepped between two different positions to create the two ion exposure areas  410 ,  412 . As illustrated in  FIG. 4   c , an overlap region  414  exists between the ion exposure areas  410 ,  412 . Because the ion beam  402  has an increased height H 3  the control of the overlap region  414  (or an underlap region) may be better as compared to the case where the beam height is only H 2  as is the case in the absence of the quadrupole electrostatic lens system  320 . This leads to the ability to provide a more uniform ion dose across an entire substrate  112 . Moreover, because the quadrupole electrostatic lens system  320  is arranged along the same portion of the beam path of the ion beam  402  as that occupied by the set of scanning electrodes  318 , the ion beam scanning assembly and thereby without requiring a larger footprint for an ion implantation system to house the ion beam scanning assembly  300 . 
     In addition to improving the uniformity of ion dose at a substrate, in additional embodiments the ion beam scanning assembly  300  may be used to increase beam current utilization for ion implantation process(es). The term “beam current utilization” as used herein refers to the fraction of ion beam current, that is the fraction of ions of an ion beam, that are delivered to a substrate.  FIG. 5   a  and  FIG. 5   b  together depict a further scenario for processing (treating) an ion beam consistent with the present embodiments. In  FIG. 5   a , a front view of the ion beam scanning assembly  300  is illustrated, while in  FIG. 5   b  a back view of the ion beam scanning assembly  300  is shown.  FIGS. 5   c  and  5   d  depict exemplary waveforms  522 ,  524 , respectively, which correspond to elements of the ion beam scanning assembly depicted in FIGS.  5   a  and  5   b  respectively. In particular, the waveforms  522 ,  524  are each composed of an oscillating voltage Vscan and a DC offset voltage Voffset as described above with respect to  FIGS. 3   b  and  3   c.    
     In the scenario of  FIG. 5   a , the ion beam  502  is a spot beam, which is shown as having the same dimensions height H 2  and width W 2  as the ion beam  402  before entering the ion beam scanning assembly  300 . Similarly to the scenario of  FIG. 4   a , in the example illustrated in  FIG. 5   a , fluctuating voltages applied to the scanning electrodes  314   a ,  316   a  is superimposed on a DC offset voltage of −20 kV. The absolute value of the peak voltage applied to the scanning electrodes  314   a ,  316   a  is 25 kV with respect to the offset voltage of −20 kV, which may deflect the ion beam  402  through a range of angles of about +/−10 degrees in some cases. As shown in  FIG. 5   c , it should be noted that in  FIG. 5   a , the +/−25 kV refers an oscillating voltage that fluctuates 25 kV with respect to the offset voltage of −20 kV, and that −/+25 kV refers an oscillating voltage having opposite phase angle with respect to the +/−25 kV. 
     However, unlike the case of  FIGS. 4   a ,  4   b  in the scenario of  FIGS. 5   a ,  5   b  a different voltage is applied to the front lens  302  as compared to the voltage applied to the back lens  308 . In particular, in  FIG. 5   a , a static voltage of +20 kV is applied to the electrodes  304 ,  306  that are coupled with the scanning electrodes  314   a ,  316   a  to form the front lens  302  of quadrupole electrostatic lens system  320 . Coupled with the DC offset voltage of −20 kV on scanning electrodes  314   a ,  316   a , the application of a positive voltage to the electrodes  304 ,  306  establishes a set of electric fields that exert a force on the ion beam  502  that tends to compress the ion beam  502  along the direction  404 . In this manner, the shape of the ion beam  502  in cross-section is further altered as the ion beam  502  traverses the ion beam scanning assembly  300 . 
       FIG. 5   b  depicts a back view of the ion beam scanning assembly  300  for the same scenario as illustrated in  FIG. 5   a . In the example illustrated, fluctuating voltages applied to the scanning electrodes  314   b ,  316   b  is superimposed on a DC offset voltage of +20 kV, and static voltage of −20 kV is applied to the electrodes  310 ,  312  that are coupled with the scanning electrodes  314   b ,  316   b  to form the back lens  308  similarly to the situation in  FIG. 4   b . Coupled with the DC offset voltage of +20 kV on scanning electrodes  314   a ,  316   a , this application of negative voltage to the electrodes  310 ,  312  exerts a force on the ion beam  402  that tends to stretch the ion beam  502  along the direction  406  that is perpendicular to the direction  404 . In this manner, as shown in  FIG. 5   b , as the ion beam  502  emerges from the ion beam scanning assembly  300 , the ion beam  502  is elongated along the direction  406  and compressed in the direction  404  in comparison to its shape when entering the ion beam scanning assembly  300  shown in  FIG. 5   a . Thus, the ion beam  502  emerges with a height H 3  that is greater than H 2  of the (incident) ion beam  502 , and width W 3  that is less than the width W 2  of the (incident) ion beam  502 . In addition, the absolute value of the peak voltages applied to the scanning electrodes  314   b  and  316   b  is 25 kV with respect to the offset voltage of +20 kV, which may deflect the ion beam  402  through a range of angles of about +/−10 degrees in some cases. It should be noted that in  FIG. 5   b , the +/−25 kV refers an oscillating voltage that fluctuates 25 kV with respect to its offset voltage of +20 kV, and that −/+25 kV refers an oscillating voltage having opposite phase angle with respect to the +/−25 kV. 
       FIG. 5   e  depicts one example of processing the substrate  112  using the embodiment of  FIGS. 5   a ,  5   b , which illustrates an advantage provided by the embodiment of  FIGS. 5   a ,  5   b , namely increased beam current utilization. In particular, the ion beam  502  having the cross-sectional shape characterized by the height H 3  and the width W 3  of  FIG. 5   b  is shown as it impinges on the substrate  112 . The ion beam  502  may be electrostatically scanned using the scanning electrodes  314 ,  316  to form the exposed area  510 . As shown in  FIG. 5   e , the exposed area  510  includes an exposed substrate area  512 , which represents the portion of the exposed area  510  that intercepts the substrate  112 . The exposed area  510  further includes off-substrate areas  514   a ,  514   b  which represent portions of the exposed area  510  in which ions do not impact the substrate  112 . The ratio of the exposed substrate area  512  to the exposed area  510  may be considered as a measure of the beam current utilization. Because the ion beam  502  has a narrower width W 3  as compared to the width of the ion beam  502  W 2  without the action of the quadrupole electrostatic lens system  320  depicted in  FIGS. 5   a ,  5   b , the ion beam  502  may not need to be scanned as far beyond the edges  518 ,  520  of the substrate  112  to ensure complete exposure of the substrate  112 , in comparison to the situation in which the ion beam width is W 2  (see, e.g.,  FIG. 4   c  in which the off-substrate areas  416 ,  418  are larger). Accordingly, the beam current utilization is enhanced in the scenario of  FIGS. 5   a ,  5   b.    
     In addition to the aforementioned advantages afforded by the present embodiments, the co-location of a scanner lens component and a quadrupole lens components affords a compact system for manipulating an ion beam that reduces the length of a region along the ion beam path in which electrons are stripped in comparison to configurations in which the components are not collocated. In other words, because the scanner and quadrupole components may attract electrons and thereby strip a passing ion beam of electrons, their collocation into a compact system reduces the length of the ion beam that may be stripped of electrons if the scanner component and quadrupole lens component were located in series fashion along a beam line. 
     The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Furthermore, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto 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 view of the full breadth and spirit of the present disclosure as described herein.