Abstract:
An ion implanting architecture ( 60 ). The architecture comprises an arc chamber ( 64 ) having an interior area ( 64   i ). The architecture also comprises a plurality of electron sources ( 66, 68 ) disposed at least partially within the interior area. Each of the plurality of sources comprises a conductive plate ( 72, 80 ) operable to emit electrons into the interior area and a heating element ( 70, 78 )for transferring heat to the conductive plate.

Description:
This application claims priority under 35 USC § 119(e)(1) of provisional application No. 60/167,373 filed Nov. 24, 1999. 
    
    
     CROSS-REFERENCES TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present embodiments relate to integrated circuit formation, and are more particularly directed to an ion source architecture for providing ion implantation to form integrated circuits. 
     Integrated circuits are immensely prevalent in all aspects of contemporary electronic technology. Indeed, vast resources are expended in developing and implementing integrated circuit technology in order to supply demands imposed by the consuming marketplace. In this regard, the efficient production of integrated circuits is critical, and the present embodiments are directed at such efficiency. Particularly, the present embodiments improve the efficiency for building integrated circuits on a wafer or the like by improving the efficiency of the ion source architecture for providing ion implantation to the wafer. This as well as other benefits are explored later, but are first preceded by a discussion of the prior art. 
     By way of introduction, FIG. 1 illustrates a general view of various components of a prior art ion source architecture  10 . Architecture  10  may include other components and could be illustrated and presented in still greater detail, but the illustration as shown and discussion below should be satisfactory to present one skilled in the art with a sufficient understanding of the prior art and for purposes of better appreciating the preferred embodiments discussed later. Turning to architecture  10 , it includes an ion source  12  which includes various components described below, and as detailed below where during operation an ion beam  14  is extracted from source  12  so that ions are directed toward and implanted into an integrated circuit wafer  16 . Looking in greater detail, ion source  12  includes an arc chamber  18  which has an interior area  18   i  for ion activity described below, and which includes an arc slit  18   s  which is an aperture through which ions may exit interior area  18   i  in the form of ion beam  14 . Disposed through open ends of arc chamber  18  and through interior area  18   i  is a filament  20 . Filament  20  at its ends  20   p  and  20   n  is connected to the positive and negative terminals, respectively, of a filament power supply  22 . An arc power supply  24  has its negative terminal connected to the positive terminal of filament power supply  22  and its positive terminal connected to arc chamber  18 . A positive terminal of an extraction power supply  26  is connected to the positive terminal of arc power supply  24 , and the negative terminal of an extraction power supply  26  is connected to an extraction electrode  28  shown vertically in FIG. 1, and which includes an aperture  28   a  through which ion beam  14  may pass as further detailed below. 
     The operation of architecture  10  is now explored. Each of power supplies  22 ,  24 , and  26  is energized, while wafer  16  is set at a potential which is low relative to that imposed on arc chamber  18  (e.g., wafer  16  may be set at ground or treated as a ground plane). The energizing of filament power supply  22  applies a potential across filament  20  which thereby causes filament  20  to heat; this heat is of a sufficient intensity so that electrons are emitted away from filament  20  into interior area  18   i . In addition, the energizing of arc power supply  24  imposes a voltage on arc chamber  18  that is positive relative to that on filament  20  to thereby influence the direction of the electrons emitted by filament  20 , primarily in an effort to maintain a heavy concentration of those electrons near the center of interior area  18   i . Still further, one or more gases is typically provided into interior area  18   i , although the apparatus for providing such gas is not shown in FIG.  1 . In any event, the resultant electron and gas combination is often referred to in the art as a plasma, with its constituent parts also being referred to as ions. Magnets (not shown) are used to increase the electron mean free path further enhancing plasma generation. Lastly, the energizing of extraction power supply  26  imposes a voltage on extraction electrode  28  that is negative relative to that imposed on arc chamber  18 , thereby attracting positive ions outward of slit  18   s  and producing a positive charged ion beam  14 . Ion beam  14  passes through aperture  28   a  and impacts the surface of wafer  16 , thereby implanting ions from beam  14  into wafer  16 . Lastly, it is also known in the art to use one or more magnets (not shown) so as to divert some of the ion types away from wafer  16  so that only the remaining desired ions impact and thereby implant within wafer  16 . 
     While architecture  10  has been successful for implanting ions in wafers, it also has various drawbacks. For example, recall that filament  20  passes through the center of interior area  18   i , and also that it is desirable to maintain a heavy concentration of electrons near the center of interior area  18   i . The resulting concentration of plasma at the center of interior area  18   i  tends to gradually wear filament  20  and, indeed, it is known that filament  20  will eventually fail (e.g., break), typically in response to this plasma exposure. This failure prohibits further use of architecture  10  until a satisfactory repair is made and, thus, there may be considerable down time in the operation of architecture  10 . Such down time is considerably expensive when demand is to keep architecture  10  operating on a full-time basis, as is often the case in contemporary semiconductor fabrication facilities. As another disadvantage, the use of filament  20  as a single filament may have limitations on the amount of ion concentration it is capable of producing. 
     By way of further background, FIG. 2 illustrates an alternative prior art ion source architecture  30 . To simplify this and the remaining prior art illustrations, some of the components in architecture  30  are the same as those shown with respect to architecture  10  of FIG. 1; as a result, these components and their reference numbers are carried forward from FIG.  1  and the reader is assumed familiar with the earlier discussion of such components. Looking then to the other components in architecture  30 , it includes an ion source  32 , which is sometimes referred to in the art as a Bernas source. Ion source  32  includes an arc chamber  34  which has an interior area  34   i  for ion activity and an arc slit  34   s  which through which ions may exit interior area  34   i  (as ion beam  14 ). Located proximate a first opening at a first end of arc chamber  34  is a filament  36 , where filament  36  has a length  36   ptl  in the shape of a pigtail and which exists within interior area  34   i , and where filament  36  further has ends  36   p  and  36   n  connected to the positive and negative terminals, respectively, of filament power supply  22 . Located at a second end of arc chamber  34  is a reflector  38 , where for reasons discussed below it should be noted that reflector  38  is therefore at an opposite end of arc chamber  34  relative to the location of filament  36 . Reflector  38  includes a reflecting plate  38   p  which is typically a metal material, and plate  38   p  is supported by a support  38   s  which is an insulating material so as to electrically isolate plate  38   p  from arc chamber  34 . 
     The operation of architecture  30  is similar in various respects to that of architecture  10 , namely, in architecture  30  each of power supplies  22 ,  24 , and  26  is energized and wafer  16  is set at a potential which is low relative to that imposed on arc chamber  34 . In response, filament  36  heats and pigtail  36   ptl  emits electrons into interior area  34   i , and these electrons are further directed toward the center of interior area  34   i  due to the electrical bias imposed on arc chamber  34  and additional source magnets (not shown). Once more, these electrons may be combined with one or more gases in interior area  34   i  to create a plasma from which ion beam  14  may be extracted. In addition, however, for architecture  30  reflector  38  also influences the directionality of the electrons in interior area  34 . Particularly, when electrons are initially emitted by pigtail  36   ptl  and toward reflector plate  38   p , plate  38   p  accumulates a negative charge. Thereafter, as additional electrons are emitted in the same manner, they are reflected away from plate  38   p  and again toward the center of interior area  34   i . As a result, the concentration of electrons and, thus, the ion plasma density at the center of interior area  34   i , is enhanced. 
     From the above, one skilled in the art will appreciate that architecture  30  also has been successful for implanting ions in wafers, but it too has various drawbacks. For example, filament  36 , both in the portion forming pigtail  36   ptl  and a smaller portion that extends toward ends  36   p  and  36   n , also is physically in contact with the plasma formed in interior area  34   i  and, once more, therefore this layout deteriorates the integrity of filament  36  such that it eventually fails in response to this contact. The deterioration may be improved as compared to architecture  10  since filament  36  does not extend to the absolute center of interior area  34   i , but nonetheless the direct exposure of filament  36  to the plasma will cause an ultimate failure of filament  36 . As with prior art architecture  10 , such a break prohibits further use of architecture  30  until a satisfactory repair is achieved, thereby presenting the expense and other burdens associated with a considerable down time in the operation of architecture  30 . 
     As still further background, FIG. 3 illustrates an alternative prior art ion source architecture  40 . Architecture  40  includes an ion source  42  which is sometimes referred to in the art as an indirectly-heated cathode source for reasons more clear. With one exception, architecture  40  is the same as architecture  30  and, thus, for simplicity the common components and their reference numbers are carried forward from FIG. 2 to FIG. 3, with the reader being assumed familiar with the earlier discussion of such components. Looking to the one difference between architectures  40  and  30 , filament  36  in ion source  42  is protected from interior area  34   i  by a cathode  44 . Thus, filament  36  may extend into interior area  34   i , but to the extent that it does so it is encased within the interior  44   i  defined by cathode  44 . Typically, cathode  44  has a metallic end  44   e , and its sides  44   s  are insulated from arc chamber  34  either by forming them from an insulating material or by separating cathode  44  from arc chamber  34  with air (i.e., by permitting a space between arc chamber  34  and cathode  44 ). The operational description below provides further insight as to the reasons for choosing such materials and the desirability of this insulating effect Lastly in connection with power to cathode  44 , cathode  44  is biased by a positive terminal of a cathode power supply  45 , where that positive terminal is also connected to the negative terminal of arc power supply  24 . The negative terminal of cathode power supply  45  is connected to the positive terminal of filament power supply  22 . 
     The operation of architecture  40  is similar in various respects to that of architecture  30  in that, once again, each of power supplies  22 ,  24 , and  26  is energized, wafer  16  is set at a potential which is low relative to that imposed on arc chamber  34 , filament  36  heats, and an ion beam  14  is extracted toward wafer  16 . More particularly, however, for architecture  40  the heating of filament  36  transfers heat to cathode  44  and, thus, cathode  44  emits electrons. In this manner, therefore, the heat from filament  36  indirectly causes the emission of electrons into interior area  34   i , thereby giving rise to the earlier-introduced “indirectly-heated” identifier used in the art with respect to ion source  42 . In any event, these indirectly generated electrons proceed in the same manner as described above and, thus, are directed toward the center of interior area  34   i  due to the operation of reflector  38  as well as the bias on arc chamber  34  and the source magnets (not shown). 
     Architecture  40  provides an improvement over architectures  10  and  30 , but it also provides drawbacks. Turning first to the improvement, filament  36  is not exposed directly to the plasma within interior  34   i  because filament  36  is encased within cathode  44 . Thus, the encasing effect of cathode  44  around filament  36  initially protects filament  36  from the plasma-created deterioration described above with respect to architectures  10  and  30 . However, cathode  44  is itself exposed to the plasma; as a result, and as a drawback of architecture  40 , at some point an aperture or other passage will form within cathode  44  and filament  36  is then exposed to the plasma. Accordingly, eventually filament  36  also will fail and, at that time, architecture  40  requires down time for repair. 
     As a final example, FIG. 4 illustrates an alternative prior art ion source architecture  50 . Architecture  50  includes an ion source  52  which is sometimes referred to in the art as a double Bernas source since ion source  52  doubles the interior elements of the Bernas ion source  32  shown in FIG.  2 . Thus, in addition to those elements shown in FIG. 2 (and carried forward into FIG.  4 ), an arc chamber  51  has an ion source  52  which includes a second filament  54  having a pigtail  54   ptl  and a second reflector  56 , where these devices are formed in the same manner as filament  36  and reflector  38 , respectively, discussed above in FIG.  2 . The positioning of these devices differ, however, in that reflectors  38  and  56  are at opposing ends of arc chamber  51  while filaments  36  and  54  are in the same side of arc chamber  51  and they also are on the opposite side of arc chamber  34  as compared to the side in which arc slit  51   s  is formed. Lastly, note that filaments  36  and  54  are electrically connected in parallel to filament power supply  22 . 
     The operation of architecture  50  is quite similar to that of architecture  30 , with the example of a duplicate effect provided by using dual filaments and dual reflectors. Thus, once the power and potentials as described above relative to FIG. 2 are provided, each of filaments  36  and  54  emits electrons into interior area  51   i , and those electrons are further directed toward the center of interior area  51   i  due to the electrical bias imposed on arc chamber  51  as well as the reflective action of reflectors  38  and  56  and the source magnets (not shown). Once more, these electrons may be combined with one or more gases in interior area  51   i  to create a final plasma from which ion beam  14  may be extracted. 
     Architecture  50  provides both improvements and drawbacks relative to various of the architectures described above. As an improvement, the use of dual filaments  36  and  54  improves the plasma density that may be achieved within interior area  51   i  of architecture  50 . As a result, higher beam currents are associated with ion beam  14  of architecture  50 . However, note that the drawbacks of architecture  50  are similar to those of architecture  30 . For example, each of filaments  36  and  54  extends within interior area  51   i  and, thus, each filament is unprotected from the plasma and will wear as a result of such exposure. Indeed, this aspect may be more troublesome when there is reliance on dual components. In other words, the benefit of the dual filaments is lost if either one of filaments  36  or  54  fail and, thus, to the extent that both are needed then architecture  50  is limited in operation until the first failure of either filament, at which time the other filament may be effectively useless because ion source  52  will require down time to service at least the first-failed filament. 
     In view of the above, there arises a need to address the drawbacks of the prior art and to provide an improved integrated circuit ion source architecture, as is achieved by the preferred embodiments discussed below. 
     BRIEF SUMMARY OF THE INVENTION 
     In the preferred embodiment, there is an ion implanting architecture. The architecture comprises an arc chamber having an interior area. The architecture also comprises a plurality of electron sources disposed at least partially within the interior area. Each of the plurality of electron sources comprises a conductive plate operable to emit electrons into the interior area and a heating element for transferring heat to the conductive plate. Other circuits, systems, and methods are also disclosed and claimed. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 illustrates a general view of a prior art ion source architecture having an ion source with a filament passing through the center of the arc chamber; 
     FIG. 2 illustrates a general view of a prior art ion source architecture having an ion source with a filament having a pigtail portion within the interior of the arc chamber and a reflector disposed at an opposite end of the arc chamber; 
     FIG. 3 illustrates a general view of a prior art ion source architecture having an ion source with a filament having a pigtail portion encased within a cathode that extends within the interior of the arc chamber, and further includes a reflector disposed at an opposite end of the arc chamber; 
     FIG. 4 illustrates a general view of a prior art ion source architecture having an ion source with two filaments disposed along a side of the arc chamber, where each filament has a pigtail portion within the interior of the arc chamber, and further includes a pair of reflectors disposed at opposite ends of the arc chamber; 
     FIG. 5 illustrates a general view of a first inventive ion source architecture having an ion source with two electron source assemblies, where each assembly is alternately operable to emit electrons or reflect electrons based on the configuration of a switch connected between the assemblies and a single set of power supplies; and 
     FIG. 6 illustrates a general view of a second inventive ion source architecture having an ion source with two electron source assemblies, where each assembly is operable, either alternately or concurrently, to either emit electrons or reflect electrons based on the configuration of switches connected between the assemblies and a dual set of power supplies. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 through 4 were discussed earlier in the Background Of The Invention section of this document and the reader is assumed familiar with such discussion. 
     FIG. 5 illustrates a first inventive ion source architecture  60 . As in the case of the architectures described above, note that architecture  60  may include other components and could be illustrated and presented in greater detail; however, the illustration as shown and discussion below should be satisfactory to present one skilled in the art with a sufficient understanding of the preferred embodiments. Turning to architecture  60 , it includes an ion source  62  which, using a different apparatus and methodology than the prior art, also permits extraction of ion beam  14  through an aperture  28   a  of extraction plate  28  and toward an integrated circuit wafer  16 . Looking in greater detail, ion source  62  includes an arc chamber  64  formed using a conductive material and which is electrically connected to a positive terminal of an arc power supply  65 . Arc chamber  64  has an interior area  64   i  for ion activity and an arc slit  64   s  which is an aperture through which ions may exit interior area  64   i  in the form of ion beam  14 . At opposing ends of arc chamber  64  are structurally identical indirectly-heated ion source assemblies  66  and  68 , where the structure and functionality of such assemblies differs from the prior art in various respects as detailed below. Briefly noting some of the distinctions, each of assemblies  66  and  68  is operable to perform a dual functionality not provided by the prior art, the preferred orientation of assemblies  66  and  68  differs from the prior art, and the electrical connections of assemblies  66  and  68  differs from the prior art. Each of these differences will be apparent by the conclusion of the remaining discussion of the structure and operation of architecture  60 . 
     Looking now in more detail to assembly  66 , it includes a filament  70  having ends  70   p  and  70   n  which are connected to terminals  71   1  and  71   3 , respectively, of a switch  71 . Filament  70  also preferably includes a pigtail portion  70   ptl . Filament  70  is encased relative to interior area  64   i  by a cathode  72 , that is, filament  70  in disposed within interior  72   i  of cathode  72 . Thus, cathode  72  may be shaped in the form of a hollow container with an open end to receive filament  70  and a closed end toward interior area  64   i , or in some other configuration whereby cathode  72  protects filament  70  from exposure to the plasma formed within interior area  64   i . Cathode  72  includes an emitter/reflector portion  72   er  as well as insulating sides  72   s . In the preferred embodiment, emitter/reflector portion  72   er  is formed by a conductor, such as a metal. Also in the preferred embodiment, insulating sides  72   s  are formed using an electrical insulator, although sides  72   s  also may be metal or some other conducting material so long as there is a gap or some other insulating mechanism between arc chamber  64  and emitter/reflector portion  72   er . Further, cathode  72  is electrically connected to a terminal  71   5  of switch  71 . In this regard, terminal  71   5  is shown generally connected to side  72   s  of cathode  72 ; however, it should be understood that if side  72   s  is an insulator, the connection is sufficient to provide a potential to emitter/reflector portion  72   er , such as by a separate conductor (not shown). 
     Having introduced some of the connections relative to assembly  66  and switch  71 , the remaing connections relative to those devices are now explored. Switch  71  further includes three terminals  71   7 ,  71   8 , and  71   9  that are connected to power supplied included in architecture  60 . More particularly, terminal  71   7  is connected to the negative terminal of a filament power supply  74 ; accordingly, when switch  71  is in its upward position as shown in FIG. 5, then end  70   n  of filament  70  is electrically connected, via switch  71 , to the negative terminal of filament power supply  74 . Similarly, terminal  71   8  is connected to the positive terminal of filament power supply  74  (and also to the negative terminal of a cathode power supply  76 ); accordingly, when switch  71  is in its upward position as shown in FIG. 5, then end  70   p  of filament  70  is electrically connected, via switch  71 , to the positive terminal of filament power supply  74 . Terminal  71   9  is connected to the positive terminal of cathode power supply  76 , and also to the negative terminal of arc power supply  65 ; accordingly, when switch  71  is in its upward position as shown in FIG. 5, then cathode  72  is electrically connected, via switch  71 , to the positive terminal of cathode power supply  76  (and to the negative terminal of arc power supply  65 ). Finally, note that switch  71  includes three floating terminals  71   2 ,  71   4 , and  71   6 , that is, each of these terminals is not connected to a load or power supply. Thus, and for reasons more clear below, when switch  71  is in its downward position, assembly  66  is not connected to either filament power supply  74  or cathode power supply  76 . 
     Assembly  68 , as mentioned above, is structurally identical to assembly  66 , although its electrical connection differs as may its operation, with the latter two aspects being detailed later. Briefly noting the structural identity, assembly  68  includes a filament  78  having ends  78   p  and  78   n  and a pigtail portion  78   ptl . Filament  78  is encased relative to interior area  64   a  by a cathode  80 , where cathode  80  is a hollow container with an open end to receive filament  78  and a closed end toward interior area  64   i  (or again, some other configuration that protects filament  78  from exposure to the plasma). Cathode  80  includes an emitter/reflector portion  80   er  as well as insulating sides  80   s , where each of these items is formed of like materials relative to assembly  66 . 
     Assembly  68  is electrically connected relative to power supplies  74  and  76  in a manner differing from that of assembly  66 , which is also explored in the operational discussion below. Looking now to the specific electrical connections relative to assembly  68 , end  78   n  of filament  78  is connected to terminal  71   2  of switch  71  and end  78   p  of filament  78  is connected to terminal  71   4  of switch  71 . Cathode  80  is connected to terminal  71   6  of switch  71 . Given these connections, one skilled in the art should appreciate that when switch  71  is in its downward position, then end  78   p  of filament  78  is electrically connected, via switch  71 , to the positive terminal of filament power supply  74 , end  78   n  of filament  78  is electrically connected, via switch  71 , to the negative terminal of filament power supply  74 , and cathode  80  is electrically connected, via switch  71 , to the positive terminal of cathode power supply  76 . However, switch  71  is in its upward position, assembly  68  is not connected to either filament power supply  74  or cathode power supply  76 . 
     The operation of architecture  60  is now discussed in detail. Initially, switch  71  is placed in either its upward or downward position; for the sake of example, assume that switch  71  is initially placed in its upward position as shown in FIG.  5 . At this point, each of power supplies  65 ,  74 , and  76  is connected to the corresponding devices shown in FIG.  5 . Thus, a bias is applied across filament  70  which thereby causes filament  70  to heat and that heat is transferred to cathode  72  and, particularly, the heat is transferred to emitter/reflector  72   er . Given the material selected to form emitter/reflector  72   er , at this point it operates primarily as an emitter of electrons, and those electrons are emitted into interior area  64   i . Additionally, arc power supply  65  provides a bias to arc chamber  64  which relative the bias imposed on cathode  72  causes the electrons emitted from emitter/reflector  72   er  to travel primarily toward the center of interior area  64   i . Still further, given that switch  71  is in its upward position, note at this time that emitter/reflector  80   er  is electrically floating; additionally, given the material selected to form emitter/reflector  80   er , at this point it operates as a reflector of the electrons emitted by emitter/reflector  72   er . More particularly, the floating emitter/reflector  80   er  develops a negative charge from the electrons initially emitted from emitter/reflector  72   er , and thereafter the negative charge on emitter/reflector  80   er  causes additional electrons emitted from emitter/reflector  72   er  to return toward, and concentrate within, the center area of interior area  64   i . Lastly, once a concentrated plasma is formed (e.g., also by adding gas to interior area  64   i ), ion beam  14  is extracted due to the potential applied by extraction power supply  26  to extraction plate  28 , and ion beam  14  therefore passes through aperture  28   a  toward integrated circuit wafer  16 . 
     Following the preceding operation of architecture  60 , switch  71  is later placed in its downward position. At this point, arc power supply  65  continues to bias arc chamber  64 , but filament power supply  74  now biases filament  78  and cathode power supply  76  now biases cathode  80 . Accordingly, one skilled in the art will appreciate that electrons are now emitted and reflected in the opposite fashion as that described above with respect to switch  71  in its upward position. More particularly, when switch  71  is in its downward position, filament  78  heats which causes emitter/reflector  80   er  to emit electrons into interior area  64   i , while emitter/reflector  72   er  is then initially floating and charged by electrons emitted by emitter/reflector  80   er  so that emitter/reflector  72   er  at this point serves a reflector function. Once more, therefore, ion concentration is maintained primarily in the center of interior area  64   i , and these ions may be extracted in the form of ion beam  14  for implanting them (or selected ones of them) into integrated circuit wafer  16 . 
     The alternative positions of switch  71  and the resulting operation described may be selected according to various needs. As one preferred method for such selection, in one approach switch  71  may be placed in one position (e.g., upward) and architecture  60  may thereafter operate until there is a failure of filament  70 . Such a failure will be anticipated to occur over time because cathode  72 , having been exposed to the plasma within interior area  64   i , will eventually erode due to that exposure, and the erosion will then cause plasma to reach filament  70  so that it will eventually fail. However, continuing with the preferred method, when this failure occurs, switch  71  may be placed in the opposite position (i.e., downward) and architecture  60  is then immediately available for operation using filament  78  to emit electrons and emitter/reflector  72   er  as a reflector to improve central plasma concentration. 
     The alternatives presented in the preceding preferred methodology of moving switch  71  provide greatly improved efficiency in terms of the amount of time between required repair downtime of the ion source. Specifically, when a first filament fails, there is a very small amount of down time to switch in the manner described and then to use the second filament, where this small amount of time may be contrasted to the considerable down time required to stop operation of a prior art ion source and repair it once its filament (or one of its filaments) fails. In theory, therefore, the overall life expectancy of ion source  62  is twice that of a prior art source. As a result, a fabrication facility may be considerably more efficient in providing implanted integrated circuit wafers. 
     FIG. 6 illustrates a second inventive ion source architecture  90 . Architecture  90  shares many of the same components as architecture  60  and, thus, like reference numbers are carried forward from FIG. 5 to FIG. 6 with respect to these components. Further, architecture  90  also ultimately operates so that its ion source  92 , using one of a few selected methodologies, also permits extraction of ion beam  14  via an extraction plate  28  and toward an integrated circuit wafer  16 . Introducing now the differences between architectures  60  and  90 , architecture  90  includes two sets of power supplies with respect to powering the filaments and cathodes of ion source  92 ; for purposes of comparison, these supplies use the same reference numbers as in FIG. 5, but subscripts are added to those reference numbers for further distinction. Thus, ion source  92  includes a first filament power supply  74   1  and a second filament power supply  74   2 . Further, ion source  92  includes a first cathode power supply  76   1  and a second cathode power supply  76   2 . In addition to having these dual supplies, the manner in which either set of supplies is connected to ion source  92  differs from the connections of filament power supply  74  and cathode power supply  76  in FIG. 5, as detailed below. Other than these supplies and their respective connections, however, ion source  92  uses the same structure as ion source  62  and, thus, the reader is assumed familiar with the earlier detail and such information is not re-stated here for the sake of simplifying the remaining discussion. 
     Turning first to filament power supply  74   1  and first cathode power supply  76   1 , the negative terminal of first filament power supply  74   1  is connected to a terminal  94   1  of a switch  94  and the positive terminal of first cathode power supply  76   1  is connected to a terminal  94   2  of switch  94 . The positive terminal of first filament power supply  74   1  is connected to the negative terminal of first cathode power supply  76   1 , and these two terminals are further connected to a terminal  94   3  of switch  94 . Further with respect to switch  94 , it includes six additional terminals numbered  94   4  through  94   9 . Of these terminals, terminals  94   5 ,  94   7 , and  94   9  are not connected to any other load or connection, while terminal  94   4  is connected to end  70   n  of filament  70 , terminal  94   6  is connected to end  70   p  of filament  70 , and terminal  94   8  is connected to cathode  72 . Given the connections of switch  94 , one skilled in the art should therefore appreciate that when switch  94  is in its downward position, the potentials of first filament power supply  74   1  and first cathode power supply  76   1  are not connected to any component of ion source  92 ; to the contrary, when switch  94  is in its upward position (as shown in FIG.  6 ), filament  70  is connected to the bias produced by first filament power supply  74   1  while cathode  72  is connected to the bias produced by first cathode power supply  76   1 . 
     Turning to second filament power supply  74   2  and second cathode power supply  76   2 , the negative terminal of second filament power supply  74   2  is connected to a terminal  96   1  of a switch  96  and the positive terminal of second cathode power supply  76   2  is connected to a terminal  96   2  of switch  96 . The positive terminal of second filament power supply  74   2  is connected to the negative terminal of second cathode power supply  76   2 , and these two terminals are further connected to a terminal  96   3  of switch  96 . Switch  96  includes six additional terminals numbered  96   4  through  96   9 . Of these terminals, terminals  96   4 ,  96   6 , and  96   8  are not connected to any other load or connection, while terminal  96   5  is connected to cathode  80 , terminal  96   7  is connected to end  78   p  of filament  78 , and terminal  96   9  is connected to end  78   n  of filament  78 . Given the connections of switch  96 , one skilled in the art should therefore appreciate that when switch  94  is in its upward position (as shown in FIG.  6 ), the potentials of second filament power supply  74   2  and second cathode power supply  76   2  are not connected to any component of ion source  92 ; to the contrary, when switch  96  is in its downward position, filament  78  is connected to the bias produced by second filament power supply  74   2  while cathode  80  is connected to the bias produced be biased by second cathode power supply  76   2 . 
     Architecture  90  may operate according to various different methods, where the selection of a particular method is made according to the positions of switches  94  and  96 . In a first method, assemblies  66  and  68  are enabled alternately in a manner comparable in various respects to architecture  60  of FIG.  5 . In a second method, assemblies  66  and  68  are enabled concurrently. Each of these two methods is explored in greater detail below. 
     In a first method of operating architecture  90 , switches  94  and  96  are placed in a same position thereby enabling one of assemblies  66  and  68  to supply ions, while the non-activated one of assemblies  66  and  68  operates to reflect ions. For example, assume that switches  94  and  96  are placed in a same upward position. From the earlier discussion of the connections to these switches, one skilled in the art will appreciate that the upward positioning of switch  94  enables assembly  66  by connecting first filament power supply  74   1  to filament  70  and first cathode power supply  76   1  to cathode  72 . Consequently, filament  70  heats and thereby transfers heat to emitter/reflector  72   er , which in response emits electrons into interior area  64   i . In addition, the upward position of switch  96  causes assembly  68  to electrically float. As a result, filament  78  is not heated by an electrical bias and emitter/reflector  80   er  accumulates charge from electrons emitted by emitter/reflector  72   er  and, thereafter, reflects additional electrons toward the center of interior area  64   i . Also in this first method, switches  94  and  96  may be placed in a same downward position. In response, assemblies  66  and  68  are connected in a manner opposite of that described when switches  94  and  96  are in the upward position. Briefly, therefore, when switches  94  and  96  are in downward positions, assembly  68  is electrically enabled so that filament  78  heats and emitter/reflector  80   er  emits electrons into interior area  64   i , while assembly  66  electrically floats and, thus, after some initial charging, emitter/reflector  72   er  reflects electrons toward the center of interior area  64   i . As with architecture  60 , this first method of operation of architecture  90  may be used in a manner whereby in a first instance one assembly is energized until its filament fails, followed by a second instance where the opposing assembly is energized until its filament fails. Once more, therefore, the amount of time between significant downtime should be considerably increased over the prior art and, indeed, may be on the order of twice that of the prior art. 
     In a second method of operating architecture  90 , switches  94  and  96  are placed in a opposite positions. For example, if switch  94  is upward and switch  92  is downward, then both of assemblies  68  and  92  are disabled, as is useful when it is desired to turn off the ion source. As another example, if switch  94  is downward and switch  92  is upward, both of assemblies  68  and  92  are enabled. When assemblies  68  and  92  are both enabled, then each of filaments  70  and  78  heats, and each of emitter/reflectors  72   er  and  80   er  emits electrons. In this manner, therefore, the plasma density in interior area  64   i  is increased relative to that which is achieved using only one assembly. As a result, higher beam currents may be extracted from ion source  92 . 
     From the above, it may be appreciated that the above embodiments provide numerous distinctions and benefits over the prior art. For example, relative to all of the prior art embodiments described earlier, the present embodiments greatly extend the operational time between time periods required for filament replacement or the like. As another example relative to architectures  10 ,  30 , and  50 , the present embodiments do not expose the filaments directly to plasma. As another example relative to architecture  40 , the present embodiments achieve an electron reflective functionality using only electron source assemblies, and do not require the additional hardware and complexity of a separate reflector. As another example, the present embodiments permit an architecture having multiple filaments and a method of operation whereby less than all of the filaments are operated at a time; indeed, in this regard, note that the preferred embodiment has been shown with two filaments (and corresponding emitter/reflectors), but many of the present teachings may apply to a configuration with more than two filaments. As still another example relative to all of the prior art embodiments described earlier, architecture  90  provides different methods of operation, where each of the prior art architectures contemplate only a single method of operation. As a final example, while the present embodiments have been described in detail, various substitutions, modifications or alterations could be made to the descriptions set forth above without departing from the inventive scope; for example, while architecture  90  illustrates how dual power supplies may be used to provide for different operating methods, the single power supply example of architecture  60  could be used in connection with alternative switching configurations to also provide for either alternating or concurrent operation of the source filaments (assuming sufficient power availability from the single power supplies). Still other examples will be ascertainable by one skilled in the art, and such a person should therefore readily appreciate the inventive scope as defined by the following claims.