Patent Publication Number: US-8124947-B2

Title: Ion implanter having combined hybrid and double mechanical scan architecture

Description:
REFERENCE TO RELATED APPLICATION 
     This application is a continuation of and claims priority to U.S. patent application Ser. No. 11/831,744 which was filed Jul. 31, 2007, entitled ION IMPLANTER HAVING COMBINED HYBRID AND DOUBLE MECHANICAL SCAN ARCHITECTURE, the entirety of which is hereby incorporated by reference as if fully set forth herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to ion implantation systems and methods, and more specifically to an ion implantation system and method for implanting ions in a plurality of operating ranges. 
     BACKGROUND OF THE INVENTION 
     Ion implanters are conventionally utilized to place a specified quantity of dopants or impurities within semiconductor workpieces or wafers. In a typical ion implantation system, a dopant material is ionized, therein generating a beam of ions. The ion beam is directed at a surface of the semiconductor wafer to implant ions into the wafer, wherein the ions penetrate the surface of the wafer and form regions of desired conductivity therein. For example, ion implantation has particular use in the fabrication of transistors in semiconductor workpieces. A typical ion implanter comprises an ion source for generating the ion beam, a beamline assembly having a mass analysis apparatus for directing and/or filtering (e.g., mass resolving) ions within the beam, and a target chamber containing one or more wafers or workpieces to be treated. 
     Various types of ion implanters allow respectively varied dosages and energies of ions to be implanted, based on the desired characteristics to be achieved within the workpiece. For example, high-current ion implanters are typically used for high dose implants, and wherein medium-current to low-current ion implanters are utilized for lower dose applications. An energy of the ions can further vary, wherein the energy generally determines the depth to which the ions are implanted within the workpiece, e.g. to control junction depths in semiconductor devices. 
     As device geometries continue to shrink, shallow junction contact regions translate into requirements for higher ion beam currents at lower and lower energies. Additionally, requirements for precise dopant placement have resulted in ever-more demanding requirements for minimizing beam angle variation, both within the beam, and across the substrate surface. For example, in certain applications, high current implants at energies down to 300 electron Volts are desirable, while concurrently minimizing energy contamination, maintaining tight control of angle variation within the ion beam as well as across the workpiece, and also while providing high workpiece processing throughput. 
     At present, the preferred architecture to achieve high currents at low energies while minimizing angle variation is a dual-mechanical scan architecture, wherein the workpiece is mechanically scanned in two directions (e.g., a “fast” scan direction and a generally perpendicular “slow” scan direction) relative to a stationary spot ion beam. However, the relatively modest “fast” scan frequency utilizing this conventional architecture is limited by maximum accelerations that the mechanical systems can tolerate, and generally ranges between 1-3 Hz, thus limiting the maximum throughput of workpieces through the ion implanter. Ribbon beam systems, on the other hand, utilize ion beam optics for steering and shaping a ribbon-shaped ion beam, and are capable of achieving reasonably high currents at low energies. However, uniform current densities in conventional ribbon beam systems may be difficult to achieve, often at the expense of loss of angle accuracy. Hybrid scan technologies have also been provided utilizing electrostatic or magnetic “fast” scans of pencil or spot ion beams and mechanical “slow” scans of the workpiece, however, these conventional hybrid implanters further suffer beam transport problems resulting from the relatively higher space-charge density in a pencil beam and longer beam line length, especially at energies below 5 keV. 
     Conventionally, high dose implants and lower dose implants require the utilization of separate dose-specific ion implanters, wherein each implanter is designed for the respective higher or lower dose ion implantation architecture. Such a requirement for multiple ion implanters thus increases equipment cost to the semiconductor product manufacturer, as well as increasing the cost of ownership of the particular implanters. Thus, it can be appreciated that an improved beamline architecture is desirable for providing both a high dose implant and a lower dose implant utilizing a common ion implantation system. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the limitations of the prior art by providing a system, apparatus, and method that combines high current capabilities and angle control of a two-dimensional mechanical scan or “spot” ion beam implanter for high dose implants with the productivity of a hybrid scanned implanter for mid and lower dose implants. Accordingly, the following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. 
     The present invention is directed generally toward a system and method for implanting ions in a plurality of operating ranges. In accordance with the invention, an ion implantation system is provided, wherein the ion implantation system comprises an ion source configured to generate a beam of ions having a generally elliptical cross-section, therein defining a spot or pencil ion beam. The ion implantation system further comprises a mass analyzer configured to mass resolve the beam of ions, and a beam scanning system positioned downstream of the mass analyzer. 
     In accordance with the invention, the ion implantation system is configured to selectively operate in a first mode and a second mode, based on a desired dosage of ions and/or ion beam current or energy to be implanted into a workpiece. The first mode, for example, is associated with a first operating range, such as for low dose ion implantation. In the first mode, the beam scanning system is configured to scan the beam of ions along a single beam scan plane, thus defining a scanned ion beam. 
     According to one exemplary aspect of the invention, a parallelizer is positioned downstream of the beam scanning system, wherein the parallelizer is configured to selectively bend the scanned ion beam into a substantially S-shape when the ion implantation system is operated in the first mode. As such, contaminants associated with the scanned ion beam are generally filtered out while concurrently parallelizing the scanned ion beam into a ribbon-shaped beam comprising a plurality of parallel beamlets, wherein the plurality of parallel beam lets have a substantially equal length. Accordingly, the plurality of parallel beamlets of the scanned ion beam can be uniformly implanted into a workpiece positioned on a workpiece scanning system residing downstream of the parallelizer. When the ion implantation system is operating in the first mode, the workpiece scanning system is configured to selectively translate the workpiece in one dimension through the scanned ion beam, therein implanting ions at the desired dosage and/or current or energy within the first operating range. Accordingly, in the first mode, the ion implantation system can be operated in a “mechanically-limited” throughput manner, wherein medium to low-dose implants can be achieved at a substantially high workpiece throughput, and wherein an upper limit of the workpiece throughput is mainly governed by mechanical capabilities (e.g., speed) of the workpiece scanning system to translate workpieces through the scanned ion beam. 
     In accordance with the present invention, the beam scanning system is further configured to pass the beam of ions un-scanned when the ion implantation system is operated in the second mode, therein defining an un-scanned spot ion beam. The second mode, for example, is associated with a second operating range, such as a high current, or high dosage implantation. In one example, the un-scanned spot ion beam is further bent into the S-shape via the parallelizer, and the workpiece scanning system is configured to selectively translate the workpiece in two dimensions through the un-scanned spot ion beam, therein implanting ions at the desired current, energy, and/or dosage within the second operating range. Accordingly, with the ion implantation system operating in the second mode, the ion implantation system can be operated in an “implant-limited” throughput manner, wherein high-dose implants can be achieved, and wherein an upper limit of the current and/or dosage of the implants is mainly governed by the capabilities of the ion source and the ion beam transport system. 
     To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are block diagrams illustrating an exemplary ion implantation system having a common architecture for a plurality of operating ranges according to one aspect of the present invention. 
         FIG. 2  is a schematic diagram illustrating an exemplary parallelizer according to another aspect of the present invention. 
         FIGS. 3A and 3B  illustrate an exemplary first mode of operation of ion implantation according yet another aspect of the invention. 
         FIGS. 4A and 4B  illustrate an exemplary second mode of operation of ion implantation according to still another aspect of the invention. 
         FIG. 5  illustrates an exemplary method for implanting ions into a workpiece at a plurality of operating ranges utilizing a common ion implantation system in accordance with a further exemplary aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed generally toward an ion implantation system and method for implanting ions in a workpiece, wherein a plurality of differing modes of operation of the implantation system can be implemented for a plurality of operating ranges. Accordingly, the present invention will now be described with reference to the drawings, wherein like reference numerals may be used to refer to like elements throughout. It should be understood that the description of these aspects are merely illustrative and that they should not be interpreted in a limiting sense. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident to one skilled in the art, however, that the present invention may be practiced without these specific details. 
     Referring now to the figures,  FIG. 1  illustrates an exemplary ion implantation system  100  according to one aspect of the present invention, wherein the ion implantation system can be controlled to implant ions at various energies, currents, and/or dosages, as will be described herein. The ion implantation system  100  (also called an ion implanter) comprises a terminal  102 , a beamline assembly  104 , and an end station  106 , wherein the terminal comprises an ion source  108  powered by a high voltage power supply  110 . The ion source  108  is thus operable to produce an ion beam  112 , and to direct the ion beam to the beamline assembly  104 . The ion source  108 , for example, generates charged ions that are extracted and formed into the ion beam  112 , wherein the ion beam is directed along a nominal beam path  113  within the beamline assembly  104  and toward the end station  106 . It should be noted that the ion beam  112  of the present invention has a relatively narrow profile (e.g., a generally circular cross-section when viewed from along the nominal beam path  113 ), and is hereinafter alternatively referred to as a “pencil” or “spot” ion beam. 
     In order to generate the ions, a gas of a dopant material (not shown) to be ionized is located within a generation chamber  114  of the ion source  108 . The dopant gas, for example, can be fed into the chamber  114  from a gas source (not shown). In another example, it will be appreciated that any number of other suitable mechanisms (not shown) can be implemented or utilized to excite free electrons within the ion generation chamber  114 , such as RF or microwave excitation sources, electron beam injection sources, electromagnetic sources and/or a cathode operable to create an arc discharge within the chamber. Accordingly, the excited electrons collide with the dopant gas molecules, and ions are thereby generated. In general, positive ions are generated, however, the present invention contemplates the generation of negative ions, as well, and all such ion generating systems are contemplated as falling within the scope of the present invention. 
     The ions are controllably extracted through an aperture or slit  116  in the chamber  114  via an ion extraction assembly  118 , wherein the extraction assembly comprises a plurality of extraction and/or suppression electrodes  120 A and  120 B. The extraction assembly  118 , for example, can comprise a separate extraction power supply (not shown) to bias the extraction and/or suppression electrodes  120 A and  120 B in order to accelerate the ions from the generation chamber  114 . 
     It will be appreciated that since the ion beam  112  comprises like charged particles, the ion beam may have a tendency to blow up or expand radially outwardly as the like charged particles repel one another. It will be further appreciated that beam blow up can be exacerbated in low energy, high current (known in the art as high perveance) ion beams, wherein many like-charged particles are moving in the same direction relatively slowly, such that an abundance of repulsive forces among the particles exists with little particle momentum to maintain the particles moving in the direction of the nominal beam path  113 . Accordingly, in accordance with one example, the extraction assembly  118  is configured such that the ion beam  112  is generally extracted at an energy sufficiently high enough such that the spot ion beam does not blow up (i.e. so that the particles have sufficient momentum to overcome repulsive forces that can lead to the ion beam blowing up). In another example, in order to promote beam containment, it can be advantageous to transfer the ion beam  112  at a relatively high energy throughout the system, wherein the energy of the ion beam may be optionally reduced just prior to impacting a workpiece  122  located within the end station  106 , as will be described infra. It should be noted that it can also be advantageous to generate and transport molecular or cluster ions which can be transported at a relatively high energy while being implanted with a lower equivalent energy, since the energy of the molecule or cluster is divided amongst the dopant atoms of the molecule. 
     In accordance with another aspect of the invention, the beamline assembly  104  comprises a beamguide  124 , a mass analyzer  126 , and a beam scanning system  128 . The beamline assembly  104 , for example, may further comprise a parallelizer  130 . The mass analyzer  126 , for example, is generally formed at about a ninety degree angle and comprises one or more magnets (not shown), wherein the one or more magnets generally establish a dipole magnetic field within the mass analyzer. As the ion beam  112  enters the mass analyzer  126 , it is correspondingly bent via the magnetic field such that ions of an inappropriate charge-to-mass ratio are generally rejected. More particularly, ions having too great or too small a charge-to-mass ratio are deflected into side walls  132  of the mass analyzer  126 . In this manner, the mass analyzer  126  primarily allows only those ions in the ion beam  112  which have the desired charge-to-mass ratio to pass therethrough, wherein the ion beam  112  exits the mass analyzer through a resolving aperture  134 . It will be appreciated that ion beam collisions with other particles (not shown) in the system  100  can degrade beam integrity, thus, one or more pumps (not shown) may be further included to evacuate, at least, the beamguide  124 . 
     The present invention contemplates a plurality of ranges of ion dosages that can be implanted via the ion implantation system  100 . For example, the ion implantation system  100  can be configured to implant ions in a first operating range (e.g., an ion dosage ranging between approximately 5×10 10  and 5×10 14  ions/cm 2 ) and a second operating range (e.g., an ion dosage ranging between approximately 5×10 14  and 1×10 17  ions/cm 2 ). The first and second operating ranges, for example, may not necessarily be defined by dosage alone, but may be further defined by a combination of ion beam current and energy as well as, or in place of, the dosage. Accordingly, the first and second operating ranges maybe associated with ion dosage, ion beam current, and/or ion beam energy. In accordance with one example, a good approximation of operating range can be attained via the desired ion dosage, as will be further described infra. 
     Conventionally, ion implantation in both the first operating range and second operating range would require two separate ion implantation systems, with each ion implantation system being configured to only implant in a respective one of the first or second ranges of dosage, current, and/or energy. The present invention advantageously utilizes a common architecture in the ion implantation system  100  to accommodate the plurality of operating ranges, wherein a control of the ion implantation system generally determines the operating range, as will be discussed hereafter. 
     The exemplary beam scanning system  128  illustrated in  FIG. 1 , for example, comprises a scanning element  136  and a focusing and/or steering element (not shown), wherein power supply  140  is operably coupled to the scanning element  136  (and the focusing and steering element—not shown). The focusing and steering element (not shown), for example, may be configured to receive the mass analyzed spot ion beam  112  and to selectably focus and steer the ion beam to a scan vertex  148  of the scanning element  136 . 
     In accordance with one aspect of the invention, the ion implantation system  100  is configured to selectively operate in a first mode (e.g., associated with the first operating range) and a second mode (e.g., associated with the second operating range). In the first mode, for example, a voltage waveform can be selectively applied to the scanner plates  144 A and  144 B of the beam scanning system  128  via the power supply  140 , wherein the applied voltage waveform is operable to electrostatically scan the spot ion beam  112  back and forth over time, thus “spreading out” the ion beam along a single beam scan plane  149  (e.g., along the X-axis, as illustrated in  FIG. 1A ) and defining a scanned ion beam  150 , wherein the scanned ion beam can be seen as an elongate “ribbon” beam when time-averaged over a cycle of the applied voltage waveform. The scanned ion beam  150 , for example, can be viewed as comprising a plurality of beamlets  151 , wherein each beamlet is comprised of the spot ion beam  112  at a respective point in time over the cycle of the applied voltage waveform. The scanned ion beam  150  thus has a width  152  associated therewith when measured along the beam scan plane  149 , wherein the width is greater than the cross-sectional dimension of the spot ion beam  112 . The width  152  of the scanned ion beam  150 , for example, can be as wide or wider than a width (not illustrated) of the workpiece  122 . It should be noted that the width  152  of the scanned ion beam  150  may be altered or further focused via the parallelizer  130  downstream of the beam scanning system  128 . It will be further appreciated that the scan vertex  148  can be defined as the point in the nominal beam path  113  from which each beamlet  151  appears to originate after having been scanned by the scanning element  136 . 
     In accordance with the present invention, the ion implantation system is further configured to selectively pass the spot ion beam  112  through the beam scanning system  128  generally un-scanned in the second mode, wherein the spot ion beam generally only follows the nominal beam path  113 , as illustrated in  FIG. 1B . Accordingly, in the second mode of operation of the ion implantation system  100 , no voltage is applied to the scanner plates  144 A and  144 B via the power supply  140 , thus letting the spot ion beam  112  travel through the beam scanning system generally unimpeded or unaltered, while benefiting from the beam transport enhancement provided by focusing properties of the parallelizer  130 . Focusing elements such as dipole magnets and the like can be designed with focusing properties in both dimensions transverse to the propagation direction of the ion beam  112 , wherein this focusing can counteract the expansion of the beam size, thus providing good transmission of the ion beam through restrictions in the beam line, such as vacuum enclosures, apertures etc. 
     In accordance with another example, the ion beam  112  (e.g., the scanned beam  150  in the case of the first mode of operation illustrated in  FIG. 1A  or the un-scanned spot ion beam in the case of the second mode of illustrated in  FIG. 1B ) is passed through the parallelizer  130 . The parallelizer  130 , for example, comprises two dipole magnets (dipoles)  153 A and  153 B that are substantially trapezoidal in shape and are oriented to mirror one another. The dipoles  153 A and  153 B are thus configured to cause the ion beam  112  (e.g., the scanned ion beam  150  or the un-scanned spot ion beam) to bend into a substantially S-shape. Stated another way, the dipoles  153 A and  153 B have equal angles and opposite bend directions, wherein the dipoles are operable make the divergent beamlets  151  of the scanned ion beam  150  originating from the scan vertex  148 , for example, generally parallel. The two symmetric dipoles  153 A and  153 B are further described in U.S. patent application Ser. No. 11/540,064, filed Sep. 29, 2006, the contents of which is hereby incorporated herein by reference in its entirety. The use of the two symmetric dipoles  153 A and  153 B permits, in general, isotropic, or spatially uniform properties across the scanned ion beam  150 , both in terms of path length of the beamlets  151 , as well as first and higher order focusing properties. 
     Furthermore, similar to the operation of the mass analyzer  126 , the S-bend serves to decontaminate the spot ion beam  112  and scanned ion beam  150 , wherein the trajectories (not shown) of neutral particles and/or other contaminants (e.g., environmental particles that enter the beam downstream of the mass analyzer  120 ) are minimally affected by the dipoles  153 A and  153 B. As such, some number of these neutrals which do not get bent (such as from an injector), or get bent very little, thus do not impact the workpiece  122 . 
     The parallelizer  130 , for example, causes the beamlets  151  of the scanned ion beam  150  to become parallel, such that implantation parameters (e.g., implant angle) are made generally uniform across the workpiece  122 . Turning to  FIG. 2 , it can be seen that each of the dipoles  153 A and  153 B cause the beamlets  151  to bend through an angle θ  154  relative to a direction  156  parallel to the original trajectory (e.g., the nominal beam path  113 ) of the ion beam  112 , thus giving the beam its substantially S-shape. In one example, θ  154  is between about 30 degrees and about 40 degrees, but can be any angle greater than about 20 degrees. In any event, because the two dipoles  153 A and  153 B mirror one another, the respective beamlets  151  are of a substantially equal length  158 , as illustrated in  FIG. 1A . Alternatively, this can also be stated as each of the beamlets  151  having a constant path length. The symmetry properties of the dipoles thus facilitate uniform implantation parameters (e.g., implant angle). The length  158  of the beamlets  151  is kept relatively short by using relatively small bend angles in the dipoles  153 A and  153 B. This is advantageous at least because it maintains an overall footprint of the implantation system  100  relatively compact. Additionally, the dipoles  153 A and  153 B are generally separated by a gap  160 , as the illustrated example of FIG.  2 . The gap  160 , for example, generally provides an equal drift length for the respective beamlets  151 , and may separate the dipoles  153 A and  153 B by a distance of two times the pole gap of the dipoles (e.g., between about 100 and about 250 millimeters). 
     Each of the dipoles  153 A and  153 B may further comprise a plurality of cusping magnets (not shown), in order to help contain and/or otherwise control the ion beam  112  of  FIGS. 1A and 1B  passing therethrough. The cusping magnets, for example, operate as described in U.S. Pat. No. 6,414,329 to Benveniste et al., the entirety of which is hereby incorporated herein by reference. It will be appreciated that the cusping magnets generally induce a static magnetic field close to the beamline enclosure to confine electrons generated by self-neutralization or any other means so that motion of such electrons in a direction perpendicular to the magnetic field of the cusps is thereby inhibited. More particularly, the cusping magnets act to confine electrons so that it is difficult for them to move along the magnetic field and reach pole pieces or the walls of the enclosure. In this manner, any contribution of the electrons to further self-neutralization is thereby enhanced. It should be noted that various orientations, sizes, spacings and/or numbers of the cusping magnets about the dipoles  153 A and  153 B are possible and are contemplated as falling with the scope of the disclosure herein. 
     Referring again to  FIG. 1A , one or more deceleration stages (not shown) may be further positioned downstream of the parallelizer  130 . Up to this point in the system  100 , the ion beam  112  is generally transported at a relatively high energy level, such as to mitigate the propensity for beam blow up. For example, the propensity of beam blow up can be particularly high where beam density is elevated, such as at the resolving aperture  134 . Similar to the ion extraction assembly  118 , scanning element  136  and the focusing and steering element (not shown), the deceleration stage comprises one or more electrodes (not shown) coupled to a power supply (not shown), wherein the one or more electrodes of the deceleration stage are operable to selectively decelerate the ion beam  112  (e.g., the scanned ion beam  150 ). For example, deceleration of the ion scanned ion beam  150  is particularly beneficial in the first mode of operation of the ion implantation system  100 , wherein the ion beam  112  can travel at a substantially high energy prior to being scanned by the beam scanning system, and the energy of the scanned ion beam  150  can be lowered prior to impacting the workpiece  122  for the implantation of ions in the first operating range. In accordance with one example, the deceleration stage (not shown) is operable to selectively further filter neutrals and other ions of non-desired energies out of the ion beam  112  (e.g., the scanned ion beam  150 ), and ion species of the desired energy will continue to follow the desired path of the ion beam and can be selectively decelerated via the deceleration stage. 
     In accordance with another exemplary aspect of the invention, in the second mode of operation of the ion implantation system  100 , no voltage may be applied to the electrodes of the deceleration stage (not shown), therein generally permitting the spot ion beam  112  to pass through the deceleration stage generally unaffected. 
     It should be noted that in the present example, two electrodes  120 A and  120 B, and  144 A and  144 B are respectively illustrated in the ion extraction assembly  118  and scanning element  136 . It should be further noted, however, that extraction assembly  118 , scanning element  136 , focusing and steering element (not shown) and deceleration stage (not shown) may comprise any suitable number of electrodes arranged and biased to accelerate and/or decelerate ions, as well as to focus, bend, deflect, converge, diverge, scan, parallelize and/or decontaminate the ion beam  112 , such as provided in U.S. Pat. No. 6,777,696 to Rathmell et al., the entirety of which is hereby incorporated herein by reference. Additionally, the focusing and steering element may comprise electrostatic deflection plates (e.g., one or more pairs thereof, as well as an Einzel lens, quadrupoles and/or other focusing elements to selectively focus the ion beam  112 . 
     The end station  106  illustrated in  FIGS. 1A and 1B , for example, comprises a “serial” type end station, wherein a single workpiece  122  is translated through the path of the ion beam  112  via a workpiece scanning system  167  for ion implantation thereto. Alternatively, the end station  106  may comprise a “batch” type end station, wherein a plurality of workpieces (not shown) may be placed on a spinning disk (not shown) and passed through the ion beam  112 . In a preferred embodiment, the workpiece scanning system  167  is configured to support the single workpiece  122  and to mechanically scan the single workpiece in one or more dimensions or directions generally orthogonal to the ion beam path  113  through the ion beam  112 . The workpiece scanning system  167 , for example, may comprise the two-dimensional scanning system described in U.S. Pat. No. 7,135,691 to Berrian et al., the contents of which are hereby incorporated by reference herein in its entirety. Alternatively, any workpiece scanning system  167  capable of translating the workpiece  122  through the path of the ion beam  112  in one or more directions generally orthogonal to the ion beam path  113  is contemplated as falling within the scope of the present invention. 
     For example, in the first mode of operation associated with the first operating range, the workpiece scanning system  167  may mechanically translate the workpiece  122  in a first direction (e.g., Y or slow scan direction) while the ion beam  112  is scanned via the scanning element  136  (thus defining the scanned ion beam  150 ) in a second direction (e.g., X or fast scan direction) to implant ions over the entire workpiece. Accordingly, in the first mode, the ion implantation system  100  can be operated in a “mechanically-limited” throughput manner, as will be further discussed infra, wherein medium to low-dose implants can be achieved at a substantially high workpiece throughput, and wherein the upper limit of the workpiece throughput is mainly governed by mechanical capabilities of the workpiece scanning system  167  to translate workpieces  122  through the scanned ion beam  150 . 
     In accordance with another exemplary aspect of the invention, the parallelizer  130  can be omitted, and the workpiece scanning system  167  can further rotate the workpiece  122  generally about the Y axis when the ion implantation system  100  is operated in the first mode, as described in U.S. Pat. No. 6,992,310 to Ferrara et al., the contents of which are hereby incorporated by reference herein. By rotating the workpiece  122  about the Y-axis, a substantially constant implantation angle can be achieved on the workpiece. 
     In the first mode of operation associated with the first operating range, for example, the ion beam is scanned relative to the workpiece, as illustrated in  FIGS. 3A and 3B .  FIG. 3A , for example, the workpiece is shown traveling in the Y-direction (illustrated as arrow  168 ), while the ion beam  112  is scanned in the X-direction (illustrated as arrow  169 ). Accordingly, as illustrated in  FIG. 3B , the ion beam  112  traces a trajectory  170  that forms stripes  171  across the workpiece  122  as the ion beam is scanned relative to the traveling workpiece. A width  172  of each stripe  171  (shown in  FIG. 3A ), for example, is associated with the size of the ion beam  112 . Accordingly, the ion beam  112  is scanned across the workpiece  122  and then off the workpiece in order to maintain correct ion dosages, wherein one or more beam monitoring devices  173  positioned beyond the circumference of the workpiece generally permit real-time monitoring of the ion beam at extents  174  of the beam travel. Thus, as shown in  FIG. 3B , a total area  175  swept by the ion beam  112  is larger than an area  176  of the workpiece  122 , wherein the ion beam spends a considerable amount of time while being off the workpiece (e.g., when the ion beam does not impact the workpiece). 
     The ratio of time on the workpiece  122  to time off the workpiece generally defines the ion beam utilization, U. Alternatively, the ion beam utilization U can be defined, at a constant ion beam current, I, as the desired quantity of dopant implanted into the workpiece to the quantity of dopant delivered by the implantation system during the implantation process. 
     With a desired dosage D of dopant (per square unit) to be implanted into a given workpiece, the implant time t implant  for the workpiece in an ion implanter can be expressed as:
 
 t   implant   =D×A/q/I/U   (1)
 
where A is the total area of the workpiece to be implanted by the ion beam, and q is the ion charge. It will be appreciated that, depending on the width of the ion beam, the utilization can range from highs approaching approximately 80% to less than 20% in the first mode of operation. Furthermore, with continuous operation of the ion implanter, such as when implanting ions into multiple workpieces in a serial manner, the total throughput, or total processing time t total  per workpiece, of the ion implanter can be expressed as:
 
 t   total   =t   implant   +t   handling   (2)
 
where t implant  is the time associated with implanting ions into each workpiece as described above, and t handling  is the handling time associated with transferring the workpiece into and out of the ion implanter. If, for example, the implant time t implant  for a given workpiece is short, (e.g. significantly shorter than the handling time t handling ), then the throughput of the implanter is mainly governed by the handling time, and the ion implanter is operated in a “mechanically limited” throughput manner or mode.
 
     In the second mode of operation associated with the second operating range, in accordance with yet another example, the workpiece scanning system  167  is configured to mechanically translate the workpiece  122  in both the first direction (Y or slow scan direction) and the second direction (X or fast scan direction) while the ion beam  122  remains an un-scanned spot ion beam for higher dosage, higher current, and/or higher energy implants, as illustrated in  FIG. 1B . Accordingly, in the second mode, the ion implantation system  100  can be operated in an “implant-limited” throughput manner, as will be described infra, wherein high-dose implants can be achieved, and wherein an upper limit of the dosage, current, and/or energy of the implants is mainly governed by the capabilities of the terminal  102 , beamguide  124 , and mass analyzer  126 . Throughput of workpieces  122  in the second mode is thus generally limited by the beam current performance of the beamline. 
     In second mode of operation, as illustrated in  FIGS. 4A and 4B , for example, the workpiece  122  is swept through the stationary ion beam  112  in both the X-direction (illustrated as arrow  177 ) and Y-direction (illustrated as arrow  178 ) where the utilization U is again defined by the time that the ion beam spends on the workpiece versus the total implant time. A real-time current monitoring device (not shown) is located, for example, behind the workpiece, such that the scan widths are given by beam size. It should be noted that while arrows  177  and  178  are illustrated as linear translations, curvilinear translations are also contemplated as failing within the scope of the present invention, such as a pendulum-type translation of the workpiece  122  in the X-direction. 
     Speeds of two-dimensional mechanical scans of the workpiece  122  are generally slower than scan speeds of electrically and magnetically scanned systems. Accordingly, it is advantageous to mechanically scan the workpiece  122  when the implant time is long, (e.g. when the desired implant dose is high). In such a case, the times during which the ion beam  112  is off the workpiece can be made relatively short (e.g., as illustrated in  FIG. 4B ) by maintaining high accelerations in a workpiece turn-around area  179  (e.g., the time associated with the reversal of direction of workpiece travel), thus achieving higher utilizations than can be achieved in the first mode, (e.g., approaching 100% utilization), wherein a relative area  180  of beam/workpiece travel is minimized. Thus, in the second mode of operation, the workpiece  122  throughput is primarily defined by the implant time t implant , which is typically much larger than the workpiece handling time t handling . As seen in equation (1), higher utilizations lead to shorter implant times, thus leading to improved throughput and productivity for the ion implanter. 
     According to yet another example, as illustrated in  FIGS. 1A and 1B , a dosimetry system  182  is included in the end station  106  near the workpiece  122  for calibration measurements prior to implantation operations. In one example, during calibration, the ion beam  112  passes through dosimetry system  182 , wherein the dosimetry system comprises one or more profilers  184  operable to translate along a profiler path  186 , thereby measuring one or more characteristics of the ion beam (e.g., operable to measure a profile of the scanned ion beam and/or the spot ion beam  112 ). The profiler  184 , for example, may comprise a current density sensor, such as a Faraday cup, operable to measure a current density of the ion beam  112 . The measured current density, for example, may be utilized for a control of the ion implantation system via a system controller  188  operably coupled thereto. 
     The system controller  188 , for example, may comprise a computer, microprocessor, or other control system, wherein the controller is operable to control one or more of the terminal  102 , mass analyzer  126 , beam scanning system  128 , focusing and steering element (not shown), scanning element  136 , parallelizer  130 , deceleration stage (not shown), and the workpiece scanning system  167 . In one example, the system controller  188  is configured to receive measurement values from the dosimetry system  182  and to control the implantation of ions into the workpiece  122  based on the received measurement values. The system controller  188 , for example, is operable to control the formation of the ion beam  112  via a control of the ion generation chamber  114  and extraction assembly  118 . The system controller  188  is further operable to control the scanning element  136  via the power supply  140 , wherein the ion beam  112  is selectively scanned, based on the desired operating range (e.g., the first mode or the second mode of operation of the ion implantation system  100 ). 
     For example, based on the desired implantation dosage, current, and/or energy, the controller  188  is configured operate the ion implantation system  100  in the first mode, wherein the ion beam  112  is scanned by the beam scanning system  128  in the X direction, and wherein the controller controls the workpiece scanning system  167  to translate the workpiece  122  in the Y direction, therein implanting the workpiece with ions of the scanned ion beam  150 . In the second mode, the controller  188  is configured to pass the ion beam  112  through the beam scanning system  128  generally unaltered or un-scanned, wherein the controller is further configured to control the workpiece scanning system  167  such that the workpiece  122  is translated in both the X direction and the Y direction through the generally stationary spot ion beam traveling along the ion beam path  113 . 
     Accordingly, the ion implantation system  100  can be adjusted via the system controller  188  in order to facilitate desired ion implantation based upon a desired dosage, current, and/or energy of ion implantation, as well as based on the one or more measured characteristics provided by the dosimetry system  182 . In accordance with one example, the ion beam  112  can initially be established according to predetermined beam tuning parameters (e.g., the predetermined beam tuning parameters may be stored/loaded into the system controller  188 ). Then, based upon feedback from the dosimetry system  182 , the parallelizer  130  can be adjusted to alter the degree of S-bend to alter an implantation angle, for example. Likewise, the energy level of the scanned ion beam  150 , for example, can be adapted to adjust junction depths by controlling a bias applied to the electrodes  120 A and  120 B in the ion extraction assembly  118  and electrodes in the deceleration stage (not shown). In another example, the strength and orientation of magnetic field(s) generated in the mass analyzer  126  can be further controlled, such as by regulating the amount of electrical current running through field windings associated therewith, therein altering the charge-to-mass ratio of the ion beam  112 . The angle of implantation can be further controlled by adjusting the voltage applied to the steering element (not shown). 
     In accordance with another aspect of the present invention,  FIG. 5  illustrates an exemplary method  200  for implanting ions of various operating ranges into a workpiece. It should be noted that while exemplary methods are illustrated and described herein as a series of acts or events, it will be appreciated that the present invention is not limited by the illustrated ordering of such acts or events, as some steps may occur in different orders and/or concurrently with other steps apart from that shown and described herein, in accordance with the invention. In addition, not all illustrated steps may be required to implement a methodology in accordance with the present invention. Moreover, it will be appreciated that the methods may be implemented in association with the systems illustrated and described herein as well as in association with other systems not illustrated. 
     The method  200  begins at act  202 , wherein an ion implantation system, such as the ion implantation system  100  of  FIGS. 1A and 1B , is provided, wherein the ion implantation system is configured to implant ions of a spot ion beam into a workpiece in a plurality of operating ranges. For example, the ion implantation system is configured to operate in a first mode and a second mode, wherein the spot ion beam is scanned by a beam scanning mechanism in the first mode, and wherein the spot ion beam remains un-scanned in the second mode. In act  204  of  FIG. 5 , a set of desired criteria, such as a desired dosage, current, and/or energy of ions to be implanted into the workpiece, is provided. For example, a desired dosage of implantation is provided in act  204 , wherein the desired dosage ranges from a low dosage implant (e.g., approximately 5×10 10  and 5×10 14  ions/cm 2 ) to a high dosage implant (e.g., approximately 5×10 14  and 1×10 17  ions/cm 2 ). The set of desired criteria, for example, may further or alternatively comprise one or more of ion beam utilization, throughput considerations, productivity considerations, or other criteria related to the implant. 
     In act  206 , the spot ion beam is formed and mass analyzed, wherein the spot ion beam has a generally circular cross section, and wherein the ion beam has an energy and current associated with the desired criteria provided in act  204 . In act  208 , one or more properties of the spot ion beam are quantified. For example, the current and/or size of the spot ion beam is measured or determined in act  208 , such as via the dosimetry system  168  of  FIGS. 1A and 1B . In act  210  of  FIG. 5 , an implant time (e.g., a time needed to implant ions into the entire workpiece) is determined, wherein the determination of the implant time is based on the quantified one or more properties of the spot ion beam. For example, the in order to implant the entire workpiece at the desired dosage provided in act  204 , an implant time is calculated based on the quantified current and/or size of the spot ion beam. 
     In act  212 , the implant time is then compared to a scan time associated with a mechanically limited scan time. The mechanically limited scan time, for example, is a minimal time associated with operating the ion implantation system  100  in the second mode, and wherein the workpiece scanning system  167  of  FIGS. 1A and 1B  translates the workpiece  122  in the X direction and the Y direction at respective maximum velocities or limits. In the comparison of act  212  of  FIG. 5 , if the implant time determined in act  210  is generally less than the mechanically limited scan time (a relatively short implant time), and, for example, sufficient ion beam current is available, then the ion implantation system is operated in the first mode in act  214 , wherein the ion beam is scanned via the beam scanning system  128 , as illustrated in  FIG. 1A . If the implant time determined in act  210  of  FIG. 5  is generally greater than the mechanically limited scan time (a relatively long implant time), then the ion implantation system is operated in the second mode in act  216 , wherein the ion beam remains un-scanned as illustrated in  FIG. 1B , wherein the workpiece scanning system  167  translates the workpiece  122  in both the X direction and the Y direction. Accordingly, regardless of whether the ion implantation system  100  is operated in the first mode or the second mode, an implantation of ions into the workpiece  122  is performed in act  218 , wherein the implantation meets the set of desired criteria (e.g., desired dosage). 
     Thus, the present invention provides an architecture and method for implanting ions in a plurality of operating ranges while utilizing a common implantation system. As such, desired dosages, currents, and/or energies of ion implantations, as well as utilization and productivity efficiencies can be achieved using the common implantation system, regardless of the operating range, thus reducing equipment costs associated with dose-specific systems, and also increasing the utilization of the current ion implantation system. 
     Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more other features of the other embodiments as may be desired and advantageous for any given or particular application.