WO2002052609A2

WO2002052609A2 - Compact beamline and ion implanter system using same

Info

Publication number: WO2002052609A2
Application number: PCT/US2001/050844
Authority: WO
Inventors: Donald W. Berrian
Original assignee: Proteros LLC
Current assignee: Proteros LLC
Priority date: 2000-12-27
Filing date: 2001-12-27
Publication date: 2002-07-04
Anticipated expiration: 2003-06-27
Also published as: AU2002231340A1; WO2002052609A3

Abstract

Apparatus and a system using same for directing and purifying an ion beamline (102) through an acceleration column (114) that provides both desired acceleration (or deceleration) and deflection to filter or purify the ion beam. In a first preferred embodiment, the column comprises segmented sequences of electrodes (308, 314) above and below the plane of the scanned ion beam (102) and positioned through the acceleration column such that acceleration fields may be selectively produced between gaps in the sequence of electrodes as well as across opposing upper and lower electrodes. The structure of a system using the invention preferably includes a scanner component (108) to scan the beam prior to entry into the acceleration column (114) of the invention as well as an angle corrector (112) as needed to redirect and filter the beam prior to entry to the column (114). Selectively enabling application a controlled bias (310, 312, 316, 318, 320, 321) between selected upper and lower electrodes (308, 314) allows for flexible use of the acceleration column to accelerate the beamline, decelerate the beamline and/or purify the beam by deflecting the beamline through the column.

Description

APPARATUS FOR PRODUCING A COMPACT BEAMLINE AND ION IMPLANTER SYSTEM USING SAME

RELATED APPLICATIONS

This patent application hereby claims priority to United States Provisional Patent Application Number 60/258,352, entitled "A COMPACT BEAMLINE FOR A MEDIUM CURRENT ION IMPLANTER PROVIDING LARGE ENERGY RANGE, HIGH CURRENT AND LOW CONTAMINATION" filed December 27, 2000 and is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention The invention relates to ion implantation and in particular to an apparatus for directing and purifying an ion beam and in particular provides for an apparatus for accelerating or decelerating the beam in combination with purifying the beam in a short beam path length and a system using same.

2. Discussion of Related Art

In semiconductor fabrication, large wafers are fabricated with multiple circuits etched onto the wafer. In the process, it is common to implant ions on the wafer at various depths or layers in the fabrication process. The implanted ions (either positively or negatively charged) are referred to as "dopants" and the process of implanting such dopants is usually referred to as "doping."

The dopants are typically implanted by bombarding desired areas of the wafer with a directed ion beam comprising ions of the desired dopants. In a most common type of ion implanter device, the ion beam is generated by an ion source including an electron source generating a beam of electrons. The electrons bombard a precursor gas in an arc chamber of the ion source until the gas molecules become charged ions.

The charged ions, along with charged ions from impurities in the precursor gas exit the arc chamber through an aperture opening.

The energy level of the ions in the ion beam affects the depth at which the ions are implanted in the wafer. The ions are typically generated having an energy level of 10 KeV to 100 KeV. For particular doping operations, the energy level of the ions may need to be raised or lowered. Control of the energy level of the ions is therefore important to achieving the desired levels of dopant at various depths of the wafer circuits. Further, impurities in the ion beam can negatively affect the doping process. The impurities may also bombard the wafer if not removed from the ion beam and may thereby implant impurities in the wafer. Such impurities in the wafer can have a negative impact on the reliability of the circuits formed thereon.

An ion beam so generated is accelerated, decelerated and/or purified by electric or magnetic fields applied to the beam exiting the ion source. Such fields are generated by magnets or by electrostatic elements. One such field is often referred to as a "scanner" in that it directs the beam along a plane axis to scan over and intersect a corresponding line of the wafer. Other electric or magnetic fields purify the beam by isolating desired ions from undesired ions generated in the implanter system.

Different ions typically have different mass and charge levels and are therefore affected differently by such a field. The difference in movement of the different ions is used to separate the desired ions from the undesired impurities. Similar electric or magnetic fields are also used to accelerate, decelerate and direct the generated ions into a focused beam to bombard the wafer.

In a common ion implanter presently in use for eight-inch wafers, an ion beam is electrically scanned in one axis as the wafer to be bombarded is mechanically moved in the other axis. A slot acceleration column is used to accelerate or decelerate the beam after scanning to provide at wide range of energies for the resultant ion beam. United States Patent Number 4,922,106, filed April 8, 1987, teaches such a structure and is hereby incorporated herein by reference. Energy contamination of the resultant ion beam is a problem not well addressed in these prior implanters. Energy contamination results from a number of sources. First, there may be impurities in the precursor gas used to generate the ion beam in the ion source. Further, though ion implanters preferably operate in a substantial vacuum environment, the vacuum is not perfect and a number of background gases may seep into the vacuum environment of the implanter. As ions in the beam collide with these background gases, the ions may lose their charge (become neutralized) or may create other charged particles (so called "charge exchanged" components).

It is known that the slot acceleration column fails to provide any purification of its resultant beam. Rather, the slot acceleration column provides exclusively an axial force parallel to the ion beam axis to accelerate (or decelerate) the ions in the ion beam in the direction of the beam. The slot acceleration column permits the passage of the ion beam components that are neutralized or charge exchanged that have also passed through the scanning component of the ion implanter. Such contamination in the ion beam produces undesired ions bombarding the wafer and desired ions but with the wrong energy level and therefore implanted at an improper depth.

Some competing ion implanter designs attempt to reduce this problem by adding an electrostatic analysis component after the scanner and before the wafer. This component is operable to filter out undesired ions. This element is in addition to a scanner component and an electrostatic angle correction component all situated along the beam path. The addition of such a component utilizes similar electrostatic techniques to bend the path of the beam to eliminate undesired ion beam components. This solution further extends the length of the beam line - the length of the path the beam travels from its origin and the ion source to its destination at the wafer surface. This extended beam length can negatively impact the beam current performance especially in low energy implantation of ions. First, the longer beam path gives rise to more opportunities for ions in the beam to collide with impurities in the imperfect vacuum environment creating further undesired ions and neutrals. In addition, while the beam travels through such electrostatic fields, free electrons normally surrounding the ion beam are typically stripped away. Devoid of such surrounding electrons, ions in the beam tend to repulse one another and over time will have a tendency to defocus the beam - i.e., to "blow up" the beam as it is often called. It is therefore a problem to increase the length of the beam path. Other more recent implanter machines eliminate the need for a final acceleration column in hopes of reducing these negative effects discussed above. Rather, some more recent ion implanter machines deflect and scan the ion beam at the intended final energy level. United States Patent Number 5,672,879, filed June 12, 1995, teaches such a structure and is hereby incorporated herein by reference. Such designs tend to use large angles in the angle corrector of the scanning component so that charge exchanged or neutralized contaminated components will be deflected sufficiently to miss the wafer after passing through the angle corrector. Such dramatic changes in the direction and deflection of an ion beam require massive magnets to provide the requisite large angles for higher energy ion beam production. These massive magnets require significant physical space. Further, though the approach may reduce the number of electrostatic components in the implanter system, it still requires a long beam line length to permit sufficient deflection of contaminated beam components through field of the massive magnets to thereby assure sufficient separation of the intended ion beam from contaminated ion beam components.

Some variants of these more recent implanter machines utilize electrical deflection to avoid the requirement of massive physical magnets for beam deflection and separation. Electrical deflection in such a design also incurs numerous problems as above including beam blow up caused by neutralization of the beam through the deflectors at lower energy levels. This impact can be even more serious since of the beam travels through the entire length of the deflectors at the intended final energy level.

It is evident from the above discussion that a need exists for an improved structure for beam acceleration and control that permits flexible control of the energy of the beamline while reducing energy contamination of the beam and while maintaining a short beam length.

SUMMARY OF THE INVENTION The present invention solves the above and other problems, thereby advancing the state of the useful arts, by providing a ion implanter system including a column that combines the functions of electrostatic analysis to purify the ion beam with electrostatic features to accelerate or decelerate the beam thereby controlling the energy level of the beam. Another feature of the invention provides that an angle corrector applied to the input of the column may be a magnetic quadrapole component. Since the column of the present invention serves to purify the beam, this function does not fall on the angle corrector component as practiced in the prior art. The angle corrector component of the ion implanter of the present invention may therefore be a simpler design devoid of extreme angle deflection of the scanned ion beam. By combining the acceleration/deceleration function in the same component with the purification deflection function, the present invention provides a robust implanter system with shorter beam length than prior techniques and with lower energy consumption.

A first aspect of the invention therefore provides an ion implanter system having an acceleration column for controlling a scanned ion beam, the column comprising: an electrostatic deflector for controllably deflecting the ion beam in a direction substantially orthogonal to both the beam travel direction and the scan direction of the scanned ion beam; and an electrostatic field generator for controllably accelerating or decelerating the ion beam in the beam travel direction of the scanned beam.

Another aspect of the invention further provides that the electrostatic deflector and the electrostatic field generator are operable substantially simultaneously with the column. Yet another aspect of the invention further provides that the electrostatic deflector comprises: an upper electrode positioned above the plane defined by the beam travel direction and the scan direction of the scanned ion beam; a lower electrode positioned below the plane; and a source of electric potential coupled to the upper electrode and to the lower electrode to generate a potential difference between the upper electrode and the lower electrode. ^' Still another aspect of the invention further provides that the upper electrode comprises a plurality of upper electrodes and the lower electrode comprises a plurality of lower electrodes. The system further comprises: a network of resistors coupled intermediate the source of electric potential and the plurality of upper electrodes and intermediate the source of electric potential and the plurality of lower electrodes such that a potential applied to each electrode may vary in accordance with the resistor network configuration. Another aspect of the invention further provides that the electrostatic field generator comprises: a plurality of upper electrodes positioned above the plane defined by the beam travel direction and the scan direction of the scanned ion beam. The plurality of upper electrodes are positioned such that a gap is formed between adjacent pairs of the plurality of upper electrodes. The electrostatic field generator further comprises: a source of electric potential coupled to the plurality of upper electrodes to generate a potential difference in the gaps between adjacent electrodes of the plurality of upper electrodes. The potential difference creates an electric field imparting force on the scanned ion beam in a direction parallel to the beam travel direction to accelerate or decelerate the scanned ion beam.

Still another aspect of the invention further provides that the electrostatic field generator comprises: a plurality of lower electrodes positioned below the plane defined by the beam travel direction and the scan direction of the scanned ion beam. The plurality of lower electrodes are positioned such that a gap is formed between adjacent pairs of the plurality of lower electrodes. The electrostatic field generator further comprises: a source of electric potential coupled to the plurality of lower electrodes to generate a potential difference in the gaps between adjacent electrodes of the plurality of lower electrodes. The potential difference creates an electric field imparting force on the scanned ion beam in a direction parallel to the beam travel direction to accelerate or decelerate the scanned ion beam.

Yet another aspect of the invention provides further that the electrostatic field generator comprises: a plurality of upper electrodes positioned above the plane defined by the beam travel direction and the scan direction of the scanned ion beam. The plurality of upper electrodes are positioned such that a gap is formed between adjacent pairs of the plurality of upper electrodes. The electrostatic field generator further comprises: a plurality of lower electrodes positioned below the plane defined by the beam travel direction and the scan direction of the scanned ion beam. The plurality of lower electrodes are positioned such that a gap is formed between adjacent pairs of the plurality of lower electrodes. The electrostatic field generator further comprises: a source of electric potential coupled to the plurality of upper electrodes and coupled to the plurality of lower electrodes to generate a potential difference in the gaps between adjacent ones of the plurality of lower electrodes and in the gaps of the adjacent electrodes of the plurality of upper electrodes. The potential difference creates an electric field imparting force on the scanned ion beam in a direction parallel to the beam travel direction to accelerate or decelerate the scanned ion beam.

Another aspect of the invention further provides that the electrostatic deflector and the electrostatic field generator, in combination, comprise: a plurality of upper electrodes positioned above the plane defined by the beam travel direction and the scan direction of the scanned ion beam. The plurality of upper electrodes are positioned such that a gap is formed between adjacent pairs of the plurality of upper electrodes. The electrostatic deflector and the electrostatic field generator, in combination, further comprise: a plurality of lower electrodes positioned below the plane. The plurality of lower electrodes are positioned such that a gap is formed between adjacent pairs of the plurality of lower electrodes. The electrostatic deflector and the electrostatic field generator, in combination, further comprise: a first source of electric potential coupled to the upper electrode and to the lower electrode to generate a potential difference between the upper electrode and the lower electrode. The electrostatic deflector and the electrostatic field generator, in combination, further comprise: and a second source of electric potential coupled to the plurality of upper electrodes and coupled to the plurality of lower electrodes to generate a potential difference in the gaps between adjacent ones of the plurality of lower electrodes and in the gaps of the adjacent electrodes of the plurality of upper electrodes. The potential difference between the gaps creates an electric field imparting force on the scanned ion beam in a direction parallel to the beam travel direction to accelerate or decelerate the scanned ion beam.

Still another aspect of the invention further provides a network of resistors coupled intermediate the first and second sources of electric potential and the plurality of upper electrodes and intermediate the first and second sources of electric potential and the plurality of lower electrodes such that the potential applied to each electrode may vary in accordance with the resistor network configuration. Yet another aspect of the invention further provides a plurality of switches intermediate the network of resistors and the first and second sources of electric potential to permit reconfiguration of couplings between the first and second sources of electric potential and the plurality of upper electrodes and between the first and second sources of electric potential and the plurality of lower electrodes

In another aspect of the invention, the invention provides for a combined acceleration and deflection column in an ion implanter system for receiving a directed scanned ion beam defining an initial plane at entry to the column. The directed scanned ion beam having a maximum width, and for controlling the directed scanned ion beam for application to an end station. The column comprising: a plurality of upper electrodes such that each upper electrode has a substantially planar surface positioned substantially parallel to and above the initial plane defined by the scanned ion beam. The column further comprises: a plurality of lower electrodes such that each lower electrode has a substantially planar surface positioned substantially parallel to and below the initial plane defined by the scanned ion beam. The column further comprises: a source of electric potential controllably applied to the upper electrodes and to the lower electrodes to generate electric fields for controlling the scanned ion beam. Each of the upper electrodes and each of the lower electrodes has a width dimension substantially parallel to the maximum width of the scanned ion beam sufficient to generate a substantially uniform electric field across the maximum width of the scanned ion beam. The upper electrodes and the lower electrodes are positioned to enable generation of electric fields to deflect the scanned ion beam in a direction orthogonal to the direction of travel of the scanned ion beam and to enable generation of electric fields to accelerate or decelerate the speed of the scanned ion beam. Another aspect of the invention further provides control means coupled to the source of electric potential and coupled to the upper electrodes and coupled to the lower electrodes to control the electric potential applied to the electrodes to generate electric fields to control the scanned ion beam.

Still another aspect of the invention further provides that the control means includes: velocity control means to accelerate or decelerate the directed scanned electron beam in its direction of travel. T e velocity control means determines the potential difference between adjacent electrodes of the upper electrodes and between adjacent electrodes of the lower electrodes to generate an electric field to accelerate or decelerate the directed scanned ion beam in its direction of travel. The control means further includes: deflection control means to deflect the directed scanned ion beam in a deflection plane parallel to the direction of travel of the directed scanned ion beam and orthogonal to the initial plane. The deflection control means determines the potential difference between each an upper electrode of the upper electrodes and a corresponding lower electrode of the lower electrodes.

Yet another aspect of the invention further provides that the velocity control means and the deflection control means together comprise: resistor networks coupled between the source of electric potential and each of the upper electrodes and between the source of electric potential and each of the lower electrodes to determine field amplitudes and configurations of each the potential difference.

Another aspect of the invention further provides that the control means further comprises: switching means to configure the resistor networks for controlling the field amplitudes and configurations.

Still another aspect of the invention further provides that the source of electric potential includes: a first power supply coupled to the velocity control means; and a second power supply coupled to the deflection control means.

Yet another aspect of the invention further provides that the plurality of upper electrodes are positioned such that the substantially planar surface of each upper electrode is in an upper plane substantially parallel to the initial plane. The plurality of lower electrodes are positioned such that the substantially planar surface of each lower electrode defines a curved surface substantially parallel at all points in the axis of the maximum width and curving downward in the direction of travel of the directed scanned ion beam.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side view of components in an exemplary ion implanter system using a control column in accordance with the present invention.

Figure 2 is a top view of key components of the system of figure 1.

Figure 3 is a more detailed view of an exemplary preferred embodiment of the control column of the present invention used to controllably accelerate or decelerate an ion beam while also deflecting the beam in a short beamline length. Figures 4-6 are block diagrams of the control column of figure 3 configured to operate in an acceleration mode, a drift mode and a deceleration mode.

Figure 7 is a block diagram of functional elements for control of the column of figure 3 to effectuate desired velocity and deflection control of the scanned ion beam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Figure 1 is a block diagram depicting a side view of an improved ion implanter system 100 in accordance with the present invention. In general, ion implanter system 100 directs, focuses, and controls energy level of ion beam 102 initially generated by ion source 104 within the implanter system. Analyzer magnet 106 provides a first filtration of the generated ion beam 102 to eliminate undesired ions and impurities. As is known in the art, analyzer magnet 106 applies a magnetic field to redirect desired ion components in ion beam, 102 toward scanner component 108 of the implanter while undesired ions and other impurities are directed elsewhere (or undirected) and therefore prevented from proceeding further through ion implanter system 100. Scanner 108 receives the purified ion beam 102 and scans the beam into a horizontal plane orthogonal to the side view of figure 1. Figure 2 provides a top view of ion implanter system 100 showing essentially the same elements including ion beam 102 as it exits scanner 108 into a horizontal beam having a maximum width dimension ("D" of figure 2). Ion beam 102, as scanned into a horizontal plane by operation of scanner 108, then passes through a resolving aperture 110 configured as an aperture slot to further eliminate contaminants, neutrals and other impurities in the beam. Angle correction magnet 112 is preferably a standard quadrapole magnet and receives scanned ion beam 102 to correct the angles by drawing all incident beams back into coherent parallel beams. Operation and structure of such an angle correction magnet, scanner, analyzer magnet, and ion source are well-known to those of ordinary skill in the art and need not be discussed further here. The combination of these elements along with the control column 114 provides a small, simplified, energy efficient, ion implanter system by maintaining a relatively short beamline length (the total distance traveled by the beam) from ion source 104 through end station 118 (i.e., wafer target). A final aperture 116 showed in figure 1 provides a final slot for passage of the desired ion beam 102 while providing a stop to prevent further passage of undesired ions or neutrals exiting column 114. Ion beam 102 enters column 114 traveling generally in direction "T" as indicated on figure 2. This initial travel direction of ion beam 102 and the maximum width of the scanned beam marked "D" on figure 2 define an initial plane of the scanned ion beam at entry to column 114. A plurality of electrodes 115 within column 114 generate electric fields to affect the travel of scanned ion beam 102. Forces from fields generated by operation of column 114 may deflect the scanned beam 102 in a direction perpendicular to this initial plane (i.e., peφendicular to both "T" and "D" as indicated on figure 2). In addition, forces from fields generated within column 114 may accelerate or decelerate the scanned ion beam in the direction of travel "T" as indicate on figure 2.

Figure 3 is a diagram providing additional details in a side view of a preferred exemplary embodiment of column 114 as utilized in the ion implanter system 100 of figure 1 and 2. Control column 114 receives ion beam 102 as scanned into a horizontal plane (viewed on its edge in the side view of figure 3). The ion beam is a parallel scanned beam entering the column and preferably exits the column as a scanned parallel ion beam but deflected downward. To accomplish this, the column preferably has a uniform cross section as shown in figure 3 along the full width of the scan and for a distance beyond the ends of the scan greater than the vertical gap. An exemplary preferred shape and dimension of the electrodes is best viewed in the top view of figure 2 wherein it can be seen that the width of electrodes in column 114 is "W" — i.e., greater than the maximum scan width of the ion beam "D." This is necessary to ensure that the electric fields generated in the column lie in the plane of figure 2 and have no significant component along the direction that the beam is scanned (i.e., "D" in figure 2 or orthogonal to the plane of the sheet of figure 3). This also ensures that the fields have uniform magnitude and direction at different places in the scan direction ("D" of figure 2).

A first feature provided by beam control column 114 is that of ion beam deflection to filter the ion beam. Ion beam 102 is received by column 114 from the terminal vacuum chamber toward the left side of figure 3 (shown as a structural wall element 300 with a slot aperture opening 350 for receiving the ion beam). Control column 114 preferably includes a plurality of upper electrodes 308 each associated with a corresponding electrode of a plurality of lower electrodes 314. Each upper electrode 308 is coupled through a resistor 312 and switch 310 to acceleration potential source 321. Likewise, each lower electrode 314 is coupled through a corresponding resistor 316 and control switch 318 to selectively couple the electrode 314 to the difference of acceleration potential 321 and deflection potential source 320. Each upper electrode 308 and a lower electrode 314 may selectively be enabled to provide an electric field defined by the potential difference between the upper and lower electrodes. By enabling different combinations of upper and lower electrodes and varying the potential difference applied to each, and hence electric field magnitude between various opposing upper and lower electrodes, the amount of deflection force applied to the ion beam 102 may be varied. Depending upon desired energy levels for the ion beam the deflection forces generated by the various fields may be flexibly customized to any appropriate configuration and magnitude.

As shown in figure 3, an exemplary preferred deflection angle is fifteen degrees off the beam axis plane at entry to the beam control column 114. In this exemplary preferred embodiment, deflection of fifteen degrees is sufficient to allow isolation of desired ions in the ion beam 102 from any discharged neutrals that have accumulated in the ion beam 302. In this exemplary preferred embodiment, separating the desired ion beam 102 from neutral components 302 of the beam by fifteen degrees is sufficient to direct the neutral components into an exit aperture 116 to thereby further purify and direct the scanned ion beam 102. In other words, discharged neutrals proceed through column 114, on the initial plane at which they entered the column, unaffected by the electric fields produced by upper and lower electrodes 308 and 314 of figure 3. By selectively configuring switches 310 for upper electrodes 308 and switches 318 for lower electrodes 314, control column 114 may be configured to deflect ion beam 102 by the desired deflection angle at various energy levels.

Another aspect of control column 114 permits controlled acceleration and deceleration of ion beam 102 in addition to the controllable deflection of the beam. In particular, by varying the magnitude and polarity of accelerating supply 321 and therefore the potential between adjacent upper electrodes 308 and correspondingly between adjacent lower electrodes 314, further electric fields may be generated that serve to controllably accelerate or decelerate ion beam 102 as it passes through control column 114. As above, by selectively controlling switches 310 for corresponding upper electrodes 308 and switches 318 for corresponding lower electrodes 314, the number of gaps used for acceleration or deceleration can be varied. This allows the use of a shorter column and less deneutralized length where lower voltages are needed. By appropriate control of switches 310 and 318, and by varying potential source 320, control column 114 of the present invention provides increased flexibility in deflecting, and altering the energy level of, a scanned ion beam. By doing so within one simple device as compared to multiple devices (a first device for deflecting and a second device for controlling the energy level) control column 114 permits a shortened beamline length within an ion implanting system. As noted above, shortened beam path helps reduce potential for beam contamination and beam blow up.

Particular exemplary configurations of control column 114 are depicted and discussed further herein below with reference to figures 4 through 6. It will be noted by those of ordinary skill in the art that upper electrodes 308 are preferably positioned such that they form a substantially planar surface substantially parallel to the initial plane defined by the scanned ion beam at entry to control column 114 (indicated by the dashed line 352). Further, those skilled in the art will notice that the sequence of lower electrodes 314 are positioned such that they form a downward curving contour or curved surface, parallel to the width of the scanned ion beam, approximating the deflected path of ion beam 102 (indicated by dashed line 353). Though not required for operation of the column, such a placement of upper and lower electrodes provides added spacing for the deflected beam 102 to thus help avoid the possibility that the deflected ion beam would collide with the latter lower electrodes (i.e., rightmost electrodes) as the beam is deflected downward.

A suppression electrode 304 carrying a negative potential supplied by source 306 helps prevent entry into the control column 114 by free electrons potentially adrift in the end station vacuum chamber into which the ion beam exits. The end station vacuum chamber is represented in figure 3 by the end of wall structure 301 with an aperture 351 through which neutral components 302 of the beam as well as the deflected beam 102 may pass. In an exemplary preferred embodiment, electron suppression electrode 304 is formed as a ring having an aperture through which the deflected ion beam may pass as well as neutrals 302 passing undeflected through control column to 114.

In addition, those skilled in the art will note that upper electrodes 308 and similarly lower electrodes 314 are preferably designed to form a baffle like structure to protect an electrical insulating component (not shown) between the electrodes 308 or 314 and corresponding resistors (312 and 316, respectively). This insulator layer provides a vacuum seal of the chamber of the control column. The depicted staggered baffle structure helps isolate the insulation layer (not shown) from effects of the high- energy ion beam 102. Those skilled in the art will recognize a variety of similar structures and techniques for isolating the insulation layer.

Figure 7 is a block diagram functional elements of the control column used to reconfigure the column for desired deflection and acceleration/deceleration. Control circuits 700 determine the desired ion beam energy and deflection for the particular application. A velocity or energy control element 702 of control circuits 700 determines the appropriate configuration of the electrodes in control column 114 to provide the desired energy level (i.e., determines how much, if any, acceleration or deceleration force needs to be applied by electric fields in the control column). Deflection control element 704 of control circuits 700 determines the proper configuration of electrodes in column 114 to effectuate the desired deflection through column 114. These control elements effectuate changes in the switch networks associated with the electrodes of the control column. In particular, the control elements 700, 702 and 704 reconfigure the upper switch and resistor network elements 706 to control the fields generated by adjacent upper electrodes and generated by opposing upper and lower electrodes. In like manner, the control elements 700, 702 and 704 reconfigure the lower switch and resistor network elements 708 to control the fields generated by adjacent lower electrodes and generated by opposing upper and lower electrodes.

Those skilled in the art will recognize that control elements 700, 702 and 704 may be implemented as any of several equivalent control means including electronic circuits or as suitably programmed programmable devices, such as a general-puφose processor. Further, those skilled in the art will recognize that resistor and switch networks as shown are but one technique for effectuating application of desired potentials to each electrode in the control column. Separate power sources or programmable voltage sources may also be used to provide similar configurable structure. In addition, those skilled in the art will recognize that in the exemplary preferred embodiment of the control column shown in figure 3, control of the ion beam velocity and the deflection of the ion beam are tightly coupled. The magnitude of the electric field required to deflect the ion beam as desired is proportional to the velocity of the beam as received into the column and as accelerated or decelerated through the column. Therefore, as the beam energy is altered by reconfiguring the column electrodes to generate appropriate accelerating or decelerating electric fields, so must the electrode generated fields be altered to adjust the deflection of the beam accordingly.

Figures 4, 5 and 6 are simplified diagrams of control column 114 of figure 3 showing exemplary configurations for each of three different operating modes. Figure 4 depicts a first operating mode, an acceleration mode, in which control column 114 deflects ion beam 102 to purify the beam and simultaneously accelerates the ion beam to higher energy level. A first potential source 400 provides the desired potential difference between opposing upper and lower electrodes. A second source of potential 402 provides a different potential difference between gaps of adjacent upper electrodes and between gaps of adjacent lower electrodes for puφoses of accelerating ion beam 102. Figure 6 shows a similar structure whereby ion beam 102 is decelerated through control column 114. As above in figure 4, a first source of potential 600 provides the potential difference between opposing upper and lower electrodes to generate the desired deflection of ion beam 102. Second power supply 602 provides the desired potential difference between gaps of adjacent upper electrodes and between gaps of adjacent lower electrodes to provide the desired deceleration of ion beam 102. Figure 5 depicts a third mode of operation of control column 114 wherein the potential difference between opposing upper electrodes and corresponding lower electrodes is provided by power supply 500 to generate the desired deflection of ion beam 102. In this mode of operation there is no potential difference generated in the gaps between adjacent upper electrodes nor in the gaps between adjacent lower electrodes so that the ion beam is neither accelerated nor deceleration as it passes through control column 114. This mode of operation is also referred to herein as "drift mode."

Those skilled in the art will recognize a variety of switching configurations as described above in figure 3 to achieve the desired modes of operation described above with respect to figures 4 through 6. By enabling particular pairs of opposing upper and lower electrodes, by controlling the potential difference between across each pair, and by controlling the potential difference across gaps between adjacent upper electrodes and between adjacent lower electrodes, a variety of energy levels may be accommodated and generated while providing the desired deflection of the incoming scanned ion beam.

In the deceleration mode depicted by figure 6, a preferred embodiment would utilize a potential difference between gaps only in the last pair of adjacent upper electrodes and adjacent lower electrodes. This exemplary preferred approach helps minimize the length of the beamline path where the beam is decelerating to thereby reduce the possibility of the beam being neutralized or blowing up. Similarly only the last set of opposing upper and lower electrodes would be used to achieve the desired deflection for similar reasons.

The particular number of electrodes is a matter of design choice. Preferably, the potential difference between any pair of adjacent electrodes cannot exceed a maximum value that might cause arcing across electrodes. This design point maximum potential difference therefore will dictate the number of gaps generating electric fields to provide desired levels of acceleration (or deceleration). Similarly, the particular spacing and geometry of gaps between opposing upper and lower electrodes is a matter of design choice largely dictated by the degree of deflection desired in operation of control column 114 through the entire range of useful energy levels. In like manner, the specific number of power supplies utilized, the number and configurations of switches and resistor networks utilized and other parameters, dimensions and attributes of the design shown in figures 3 through 6 will be evident to those skilled in the art as a matter of design choice to achieve results in a particular application

While the invention has been illustrated and described in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only the preferred embodiment and minor variants thereof have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.

Claims

CLAIMS What is claimed is:

1. An ion implanter system having an acceleration column (114) for controlling a scanned ion beam, said column comprising: an electrostatic deflector (115) for controllably deflecting said ion beam in a direction substantially orthogonal to both the beam travel direction and the scan direction of said scanned ion beam; and an electrostatic field generator (115) for controllably accelerating or decelerating said ion beam in the beam travel direction of said scanned beam.

2. The system of claim 1 wherein said electrostatic deflector and said electrostatic field generator are operable substantially simultaneously with said column.

3. The system of claim 1 wherein said electrostatic deflector comprises: an upper electrode (115, 308) positioned above the plane defined by the beam travel direction and the scan direction of said scanned ion beam; a lower electrode (115, 3314) positioned below said plane; and a source of electric potential (320) coupled to said upper electrode and to said lower electrode to generate a potential difference between said upper electrode and said lower electrode.

4. The system of claim 3 wherein said upper electrode comprises a plurality of upper electrodes (308) and wherein said lower electrode comprises a plurality of lower electrodes (314) and wherein said system further comprises: a network of resistors (312, 316) coupled intermediate said source of electric potential and said plurality of upper electrodes and intermediate said source of electric potential and said plurality of lower electrodes such that a potential applied to each electrode may vary in accordance with said resistor network configuration.

5. The system of claim 1 wherein said electrostatic field generator comprises: a plurality of upper electrodes (308) positioned above the plane defined by the beam travel direction and the scan direction of said scanned ion beam wherein said plurality of upper electrodes are positioned such that a gap is formed between adjacent pairs of said plurality of upper electrodes; and a source of electric potential (321) coupled to said plurality of upper electrodes to generate a potential difference in the gaps between adjacent electrodes of said plurality of upper electrodes, wherein said potential difference creates an electric field imparting force on said scanned ion beam in a direction parallel to the beam travel direction to accelerate or decelerate said scanned ion beam.

6. The system of claim 1 wherein said electrostatic field generator comprises: a plurality of lower electrodes (314) positioned below the plane defined by the beam travel direction and the scan direction of said scanned ion beam wherein said plurality of lower electrodes are positioned such that a gap is formed between adjacent pairs of said plurality of lower electrodes; and a source of electric potential (321) coupled to said plurality of lower electrodes to generate a potential difference in the gaps between adjacent electrodes of said plurality of lower electrodes, wherein said potential difference creates an electric field imparting force on said scanned ion beam in a direction parallel to the beam travel direction to accelerate or decelerate said scanned ion beam.

7. The system of claim 1 wherein said electrostatic field generator comprises: a plurality of upper electrodes (308) positioned above the plane defined by the beam travel direction and the scan direction of said scanned ion beam wherein said plurality of upper electrodes are positioned such that a gap is formed between adjacent pairs of said plurality of upper electrodes; a plurality of lower electrodes (314) positioned below the plane defined by the beam travel direction and the scan direction of said scanned ion beam wherein said plurality of lower electrodes are positioned such that a gap is formed between adjacent pairs of said plurality of lower electrodes; and a source of electric potential (321) coupled to said plurality of upper electrodes and coupled to said plurality of lower electrodes to generate a potential difference in the gaps between adjacent ones of said plurality of lower electrodes and in the gaps of said adjacent electrodes of said plurality of upper electrodes, wherein said potential difference creates an electric field imparting force on said scanned ion beam in a direction parallel to the beam travel direction to accelerate or decelerate said scanned ion beam.

8. The system of claim 1 wherein said electrostatic deflector and said electrostatic field generator, in combination, comprise: a plurality of upper electrodes (308) positioned above the plane defined by the beam travel direction and the scan direction of said scanned ion beam wherein said plurality of upper electrodes are positioned such that a gap is formed between adjacent pairs of said plurality of upper electrodes; a plurality of lower electrodes (314) positioned below said plane wherein said plurality of lower electrodes are positioned such that a gap is formed between adjacent pairs of said plurality of lower electrodes; a first source of electric potential (320) coupled to said upper electrode and to said lower electrode to generate a potential difference between said upper electrode and said lower electrode; and a second source of electric potential (321) coupled to said plurality of upper electrodes and coupled to said plurality of lower electrodes to generate a potential difference in the gaps between adjacent ones of said plurality of lower electrodes and in the gaps of said adjacent electrodes of said plurality of upper electrodes wherein said potential difference between the gaps creates an electric field imparting force on said scanned ion beam in a direction parallel to the beam travel direction to accelerate or decelerate said scanned ion beam.

9. The system of claim 8 further comprising: a network of resistors (312, 316) coupled intermediate the first and second sources of electric potential and said plurality of upper electrodes and intermediate the first and second sources of electric potential and said plurality of lower electrodes such that the potential applied to each electrode may vary in accordance with said resistor network configuration.

10. The system of claim 9 further comprising: a plurality of switches (310, 318) intermediate said network of resistors and the first and second sources of electric potential to permit reconfiguration of couplings between the first and second sources of electric potential and said plurality of upper electrodes and between the first and second sources of electric potential and said plurality of lower electrodes

11. In an ion implanter system, a combined acceleration and deflection column (114) for receiving a directed scanned ion beam defining an initial plane at entry to said column, said directed scanned ion beam having a maximum width, and for controlling said directed scanned ion beam for application to an end station, said column comprising: a plurality of upper electrodes (308) wherein each upper electrode has a substantially planar surface positioned substantially parallel to and above said initial plane defined by said scanned ion beam; a plurality of lower electrodes (314) wherein each lower electrode has a substantially planar surface positioned substantially parallel to and below said initial plane defined by said scanned ion beam; and a source of electric potential (320, 312) controllably applied to said upper electrodes and to said lower electrodes to generate electric fields for controlling said scanned ion beam, wherein each of said upper electrodes and each of said lower electrodes has a width dimension (W) substantially parallel to said maximum width of said scanned ion beam (D) sufficient to generate a substantially uniform electric field across said maximum width of said scanned ion beam and wherein said upper electrodes and said lower electrodes are positioned to enable generation of electric fields to deflect said scanned ion beam in a direction orthogonal to the direction of travel of said scanned ion beam and to enable generation of electric fields to accelerate or decelerate the speed of said scanned ion beam.

12. The column of claim 11 further comprising: control^'means (700, 702, 704, 706, 708, 310, 312, 316, 318) coupled to said source of electric potential (320, 321) and coupled to said upper electrodes (308) and coupled to said lower electrodes (314) to control the electric potential applied to the electrodes to generate electric fields to control said scanned ion beam.

13. The column of claim 12 wherein said control means includes: velocity control means (702, 706, 708, 310, 312, 316, 318) to accelerate or decelerate said directed scanned electron beam in its direction of travel wherein said velocity control means determines the potential difference between adjacent electrodes of said upper electrodes (308) and between adjacent electrodes of said lower electrodes (314) to generate an electric field to accelerate or decelerate said directed scanned ion beam in its direction of travel; and deflection control means (704, 706, 708, 310, 312, 316, 318) to deflect said directed scanned ion beam in a deflection plane parallel to the direction of travel of said directed scanned ion beam and orthogonal to said initial plane wherein said deflection control means determines the potential difference between each an upper electrode of said upper electrodes (308) and a corresponding lower electrode of said lower electrodes (314).

14. The column of claim 13 wherein said velocity control means and said deflection control means together comprise: resistor networks (312, 316) coupled between said source of electric potential (321) and each of said upper electrodes (308) and between said source of electric potential (321) and each of said lower electrodes (314) to determine field amplitudes and configurations of each said potential difference.

15. The column of claim 14 wherein said control means further comprises: switching means (310, 318) to configure said resistor networks (312, 316) for controlling said field amplitudes and configurations.

16. The column of claim 13 wherein said source of electric potential includes: a first power supply (321) coupled to said velocity control means (702, 706, 708, 310, 312, 316,

318); and a second power supply (320) coupled to said deflection control means (704, 706, 708, 310, 312, 316, 318).

17. The column of claim 11 wherein said plurality of upper electrodes (308) are positioned such that the substantially planar surface of each upper electrode is in an upper plane (352) substantially parallel to said initial plane, and wherein said plurality of lower electrodes (314) are positioned such that the substantially planar surface of each lower electrode defines a curved surface (353) substantially parallel at all points in the axis of said maximum width (D) and curving downward in the direction of travel of said directed scanned ion beam (102).