Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/317—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation
  • H01J37/3171—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation for ion implantation
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/02—Details
  • H01J37/24—Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for
  • H01J37/241—High voltage power supply or regulation circuits
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/02—Details
  • H01J37/248—Components associated with high voltage supply
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
  • H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
  • H01J37/304—Controlling tubes by information coming from the objects or from the beam, e.g. correction signals

Definitions

• the present invention relates generally to ion implantation systems, and more particularly to an arc quenching circuit for extinguishing an arc that may form between high voltage electrodes within an ion implantation system, and to a method of repainting the ion beam to recover any dose losses during such arcing to attain more uniform ion implantations.
• Ion implantation systems are used to impart impurities, known as dopant elements, into semiconductor substrates or wafers, commonly referred to as workpieces.
• an ion source ionizes a desired dopant element, and the ionized impurity is extracted from the ion source as a beam of ions.
• the ion beam is directed ⁇ e.g., swept) across respective workpieces to implant ionized dopants within the workpieces.
• the dopant ions alter the composition of the workpieces causing them to possess desired electrical characteristics, such a may be useful for fashioning particular semiconductor devices, such as transistors, upon the substrates.
• the high voltage necessary to supply the ion source of such an ion beam is subject to occasional arcing between the various extraction and suppression electrodes and other nearby parts. This tendency for arcing often fully discharges one or more affected HV supplies until the arc naturally self-extinguishes at a much lower supply voltage. While arcing, the beam current may become serious erratic or may be interrupted until the supply voltage is restored, during which time ion implantation may experience intermittent or non-uniform ion implantation dose levels. Accordingly, there is a need for mitigating the effects of HV arcing associated with an ion source or the electrodes of an ion implanter to provide uniform implantation over such larger implantation angles and distances of the ion beam.
• the present invention is directed to a circuit for quenching an arc that may form between high voltage (HV) electrodes associated with the ion source of an ion implantation system to shorten the duration of the arc, to mitigate erratic ion beam current, and to mitigate non-uniform ion implantations, for example.
• the arcs that otherwise form in these areas have a tendency to substantially discharge the high voltage capacitors within such HV power supplies, for example, for the ion source or extraction electrode supply voltage (Vext), or the suppression electrode supply voltage (Vsup). Consequently, the ion beam current is dramatically affected by these "glitches" in the ion beam current (Ibeam), and accordingly takes considerable time thereafter for the supply voltages and beam current Ibeam to recover.
• the arc quench circuit of the present invention mitigates ion beam disruption and speeds beam current recovery.
• the circuit and method also facilitates repainting the ion beam over those areas where an arc was detected to recover any dose loss during such arcing.
• the circuit also comprises a motion control system operable to control horizontal and vertical scan motions of a wafer implanted by the ion implanter, to monitor horizontal and vertical scan positions associated with the detection of the arc, and to initiate a return to an initial position along a scan associated with the detection of the arc.
• the trigger control circuit of the present invention may also be further operable to receive a repaint command from the motion control system, and to force the HV switch on or off in response to the repaint command in order to repaint the ion beam between the initial position along the scan associated with the detection of the arc and a final position associated with the detection of the arc, thereby recovering any dose loss during such arcing.
• an arc quenching circuit for an ion source of an ion implantation system suitable for use in implanting ions into one or more workpieces is disclosed.
• the system includes one or more high voltage high speed (HS) switches connected in series with a HV power supply (HVPS) for the ion source (or one of several HV extraction or suppression electrodes), the HVHS switches operable to interrupt the HV power supply current to the ion source or electrodes to quench the arc, and further operable to reestablish the power supply current.
• the quantities of ions that can be extracted from the ion source are in the form of an ion beam having a beam current.
• the system also includes a trigger control circuit operable to detect a current or voltage change associated with the ion source or HV electrodes and to control the one or more HVHS switches to open or close based on the current or voltage change detection.
• One or more protection circuits are also included to protect the respective
• HVHS switch and are operable to operable to absorb energy from reactive elements external to the respective HV switch, and to clamp an over-voltage that may occur across the switch.
• system further comprises a synchronization circuit operable to synchronize and time the trigger control circuits of two or more arc quenching circuits for the opening and closing of two or more high voltage switches.
• the current or voltage change detection associated with the ion source comprises detecting one of a current surge in the HV power supply, a decrease in an ion beam current, a drop in a suppression electrode voltage, and a drop in an extraction electrode voltage.
• one of the protection circuits is connected in series with the HV switch it protects.
• one of the protection circuits is connected in parallel with the HV switch it protects.
• system further comprises an extraction suppression electrode located close to the ion source.
• current or voltage detection is accomplished during the ion implantation process to facilitate feedback or closed-loop adjustments to the ion source current or voltage.
• the current or voltage detection is accomplished prior to the ion implantation process to facilitate open loop adjustments to the ion source current or voltage.
• an arc quenching circuit for a high voltage power supply of an ion implantation system comprising a high voltage switch connected in series with a high voltage power supply for an electrode associated with the implanter, operable to interrupt and reestablish a current to the electrode, to quench an arc produced within the ion implantation system.
• the system also includes a trigger control circuit operable to detect a current or voltage change associated with the electrode and to control the one or more HV switches to open or close based on the detection.
• the system comprises one or more protection circuits, each protection circuit associated with one of the high voltage switches, operable to absorb energy from reactive elements external to the respective HV switch, and to limit an over-voltage across the switch.
• a method of quenching an arc in an ion implantation system and repainting the ion beam to recover any dose loss during such arcing using an arc quenching circuit associated with a high voltage supply for an electrode of the ion implantation system comprises horizontally scanning a wafer in front of the ion beam, vertically scanning the wafer in front of the ion beam, detecting a current or voltage change associated with an arc at the electrode, monitoring the horizontal and vertical scan positions associated with the detection of an arc, and monitoring the time duration associated with the detection of an arc.
• the method further comprises controlling a HV switch connected between the high voltage supply and the electrode to open when an arc is detected in order to interrupt an arc current to the electrode and to quench the arc, controlling the HV switch to close when the arc is not detected in order to connect the high voltage supply to the electrode and to establish the ion beam, and repainting the ion beam after an arc.
• the repainting process comprises moving the wafer to a first horizontal and vertical scan position associated with an initial detection of the arc, and closing the HV switch to enable the ion beam, and scanning the wafer horizontally and vertically in front of the ion beam until a second horizontal and vertical scan position associated with a final detection of the arc is encountered, and opening the HV switch to disable the ion beam.
• the method further comprises synchronizing two or more arc quenching circuits having two or more high voltage switches used to quench an arc between the electrodes of two or more respective high voltage power supplies for the ion implanter, and repainting the ion beam subsequent to detecting an arc from the electrodes.
• the repainting process is only accomplished if the time duration of the arc detected is longer than a predetermined interval.
• the repainting process is delayed until the ion beam scan returns to a load and unload position of the wafer. In yet another aspect, the repainting process is delayed until the ion beam scan completes a current horizontal scan movement.
• the horizontal and vertical scanning continue after the detection of an arc.
• the repainting process is delayed until the end of the ion beam scans, wherein one or more arc detections may be repainted collectively during one or more continuous scan movements.
• Fig. 1 is a schematic block diagram illustrating components of an ion implantation system according to one or more aspects of the present invention to quench an arc associated with an ion source of the ion implanter;
• Fig. 2 is a simplified block diagram of an exemplary ion implantation system such as may utilize the arc quenching circuit of the present invention
• Fig. 3 is a plot of the change in the beam current and the extraction and suppression voltages within an ion implanter during arcing of the high voltage electrodes of the ion implantation system of Fig. 2;
• Fig. 4 is a simplified schematic diagram of an exemplary suppression electrode high voltage supply circuit having a conventional arc suppression circuit such as may be used in an ion implantation system
• Fig. 5 is a simplified block diagram of an exemplary arc quenching circuit utilized in association with the high voltage supply of an ion source such as may be used in an ion implantation system in accordance with the present invention
• Figs. 6A and 6B are graphical representations depicting the arc quenching effects of opening and closing a HVHS switch of the arc quenching circuit of the present invention tested in the air and in a vacuum, respectively, during arcing of an extraction electrode associated with an ion source
• Fig. 4 is a simplified schematic diagram of an exemplary suppression electrode high voltage supply circuit having a conventional arc suppression circuit such as may be used in an ion implantation system
• Fig. 5 is a simplified block diagram of an exemplary arc quenching circuit utilized in association with the high voltage supply of an ion source such as may be
• FIG. 7 is a simplified schematic diagram of an exemplary arc quenching circuit used in an ion implanter, utilizing a HVHS switch in three high voltage supplies of the ion implanter, and utilizing a synchronization circuit to sequence and synchronize the reestablishment of the current and voltage to each of three electrodes and high voltage supply circuits illustrated and associated with an ion implantation system;
• Fig. 8 is a schematic diagram of an exemplary protection circuit such as may be used across or in series with a HVHS switch to absorb energy from reactive elements external to the respective HV switch, and to limit an over-voltage across the switch in accordance with one or more aspects of the present invention;
• Figs. 9A and 9B are simplified diagrams of relative scan motion between an exemplary ion beam and a wafer, wherein the wafer is moved simultaneously in a horizontal and vertical direction by a motion control system, and wherein when an arc is encountered, the ion beam may be disrupted either briefly creating a glitch hole, or for a longer duration creating a glitch strip having a corresponding loss of dose, such areas as may be repainted in accordance with one or more aspects of the present invention;
• Fig. 10A is another simplified block diagram of an exemplary arc quenching circuit utilized in association with the high voltage supply of an ion source such as may be used in an ion implantation system in accordance with the present invention, wherein the trigger control circuit has an external trigger input for externally controlling the triggering of the HVHS switch, for example, with a faraday cup current input;
• Fig. 10B illustrates waveforms of a faraday cup current as may be used to provide a trigger voltage to an external trigger input of the exemplary arc quenching circuit of Fig. 10A, such as may be used in accordance with one or more aspects of the present invention
• Fig. 11 is a simplified schematic diagram of an exemplary arc quenching controller used in an ion implanter, utilizing a HVHS switch between a high voltage supply and an electrode of the implanter, and utilizing a switch control circuit to sequence, control, and synchronize the reestablishment of the current and voltage to one or more electrodes, determine the duration of arc loss, and coordinate repaint commands from a motion control system or forced switch control commands from the ion implantation system in accordance with one or more aspects of the present invention;
• Fig. 12 is a flow diagram of an exemplary method for quenching an arc in an ion implanter, using an arc quenching circuit of the present invention in accordance with several aspects of the present invention
• Fig. 13 is a flow diagram of an exemplary method for repainting the ion beam to recover dose loss due to arcing in an ion implanter, for example, using the arc quenching controller of Fig. 11 in accordance with one or more aspects of the present invention.
• the present invention relates to quenching an arc that may form between high voltage extraction or suppression electrodes, for example, associated with an ion source of an ion implantation system.
• An arc quenching circuit is discussed that shortens the duration of the arc, thereby mitigating the duration of erratic ion beam current, and minimizing the non-uniformity of ion implantations, for example. Further, the circuit and method also facilitates repainting the ion beam over those areas where an arc was detected in order to recover any dose loss during such arcing.
• the circuit may also comprise or communicate with a motion control system operable to control horizontal and vertical scan motions of a wafer implanted by the ion implanter, to monitor horizontal and vertical scan positions associated with the detection of the arc, and to initiate a return to an initial position along a scan associated with the detection of the arc.
• a motion control system operable to control horizontal and vertical scan motions of a wafer implanted by the ion implanter, to monitor horizontal and vertical scan positions associated with the detection of the arc, and to initiate a return to an initial position along a scan associated with the detection of the arc.
• high voltage high speed (HVHS) switching circuits comprising HVHS switches (e.g., 65KV @ 200MHz MOSFET switches) are added in series with the high voltage supplies to the suppression and/or extraction electrodes, or ground electrodes, for example, to extinguish the harmful arcs.
• HVHS switches e.g., 65KV @ 200MHz MOSFET switches
• the high voltage capacitors of such HV power supplies may be substantially discharged. This deep discharge dramatically affects the ion beam current and requires considerable time thereafter for the power supply voltages and the ion beam current Ibeam to recover.
• Such high voltage high speed switches have just recently become available as a manufactured item, and thus find immediate use in such applications incorporating the arc quenching circuit(s) of the present invention.
• these HVHS switches also provide the ion implanter with the ability to simply turn the ion beam ON or OFF at will, either manually with a switch or via command from one of the implanters control systems, its computer, or by an external input.
• ion implanters may take a considerable time to sequence through a power up and warm up to a stable ion beam level that is useful for implantation, it is a tremendous advantage, after such a warm-up, to be able to turn the beam ON/OFF, for example, when loading or unloading a new wafer, at the start/end of each wafer scan, and if desired, even in portions of the over-travel regions of each row scan of a wafer.
• the system of the present invention facilitates this beneficial feature, known as "beam duty factor", which is the ratio of ON to OFF time of the ion beam.
• beam duty factor is the ratio of ON to OFF time of the ion beam.
• the high voltage switches are controlled by trigger circuits which detect current or voltages changes in the HV supplies to the electrodes, such changes as are associated with the formation of an arc at one of the electrodes.
• the arc quenching circuit also comprises one or more protection circuits for the HV switches to absorb excess energy from reactive components surrounding the HVHS switches and clamp any overvoltages from the HVHS switches.
• the protection circuits may be connected in parallel with and/or in series with a respective HVHS switch.
• the arc quenching circuits of the present invention may further comprise a synchronization circuit to sequence and synchronize the reestablishment of the current and voltage to each of three electrodes and high voltage supply circuits associated with an ion implantation system.
• the circuitry of the present invention also communicates with the motion control system of the ion implanter.
• the motion control system of the ion implanter In particular, during a typical implantation scan, horizontal (e.g., row) and vertical motion of the wafer in front of the ion beam (or the beam relative to the wafer) is monitored, typically by the motion control system.
• the initial and final horizontal and vertical positions associated with the arc detection are stored for a subsequent repaint process. Then, at the end of a particular row scan, or at the end of the wafer scan, for example, around the load/unload position, the motion control system initiates the repaint process.
• the ion beam is first disabled by opening the HVHS switch, and the wafer is moved to a first horizontal and vertical scan position associated with the initial detection of the arc.
• the beam may be scanned over the wafer if the implanter facilitates this type of scanning.
• the repaint process may return the wafer motion to the beginning of the row (horizontal) scan wherein the arc was initially detected, where the scan motion can begin a row as usual prior to the position of the initial arc detection. This variation may be preferable, as the scan motion would then be fully accelerated up to the same speed as that which was present when the arc was initially detected.
• the beam is enabled by closing the HVHS switch, while the wafer is horizontally and vertically scanned until a second horizontal and vertical scan position is encountered associated with a final detection of the arc.
• the HVHS switch is opened to disable the ion beam.
• HVHS arc quenching circuit of the present invention is illustrated and described in the context of ion sources and ion implanters, those skilled in the art may appreciate that such high voltage high speed arc quenching circuits may also be utilized in other applications requiring HV and high speed arc quenching, such as x- ray equipment, accelerators, other ion source applications, for example. In this manner, unwanted arc shorting of high voltage supplies may be quenched before the high voltage power supply has been significantly discharged and has had a chance to affect the output of related systems (e.g., the ion beam of an ion implanter).
• related systems e.g., the ion beam of an ion implanter
• an exemplary arc quenching circuit 100 for a high voltage supply of an ion source suitable for implementing one or more aspects of the present invention is depicted in block diagram form.
• the circuit 100 includes a high voltage power supply 102, a high voltage high speed HVHS switch 104, a current transformer (CT) 106 for detecting a change of current in the supply 102 to an ion source 120 for producing a quantity of ions that can be extracted in the form of an ion beam 130.
• CT current transformer
• HVHS switch 104 opens HVHS switch 104 when a current surge is detected.
• the HVHS switch 104 is protected by parallel and series protection circuits 110 and 115, respectively, to absorb energy from reactive components surrounding the switch 104 and protect the switch from over-voltage damage.
• the protection circuits 110 and 115 also protect the switch 104 and other components of the ion implanter, by dampening any ringing induced by switching transients and the reactive components external to the HVHS switch 104.
• the arc quenching circuit 100 may be used in any ion implanter, or other such applications as may use a high voltage supply subject to arc discharges at the output of the supply.
• arc quenching circuit 100 operates by detecting a current surge in CT 106 when an arc occurs within the ion source 120, at the extraction electrodes, or at the output of the ion source, for example, as in the ion beam current.
• the trigger control circuit 108 receives the current surge detection from the CT 106 and in turn controls the HVHS switch 104 to open. When HVHS switch 104 opens, the arc current through CT 106 drops to near zero and the arc extinguishes or "quenches".
• a delay time within the trigger control circuit or within a synchronization circuit, may provide such a delay, and will be discussed further infra.
• the switch may be allowed to repeatedly open and close until the arc no longer reoccurs.
• Fig. 2 illustrates an exemplary ion implantation system 200 such as may utilize the arc quenching circuit similar to that of 100 of Fig. 1 , of the present invention.
• ion implantation system 200 comprises an ion source 120 having several extraction electrodes 208, for providing a source of ions as an ion beam 130 for implantation system 200.
• the ions within ion beam 130 are initially analyzed in a first region 210 by a mass analyzing magnet 212 by way of magnetic deflection to filter ions of unwanted mass or energy.
• the mass analyzing magnet 212 operates to provide a field across the beam path 130 so as to deflect ions from the ion beam 130 at varying trajectories according to mass (e.g., charge to mass ratio). Ions traveling through the magnetic field experience a force that directs individual ions of a desired mass along the beam path 130 and deflects ions of undesired mass away from the beam path.
• ions of ion beam 130 having the desired mass and energy are then accelerated or decelerated in a second region 220, focused by resolving aperture and deceleration plates 232, measured by setup faraday cup 234, and in region 230, the beam is conditioned by a plasma shower 236 providing for space charge neutralization.
• the ion beam 130 enters an end station 240 for implantation in a wafer 242 the dose level of which is measured by a disk faraday cup 244.
• an arc 205 may occur between the high voltage extraction, suppression, or ground electrodes, for example, associated with the ion source.
• Fig. 3 illustrates a plot 300 of the change in the beam current which results when an arc occurs in the high voltage extraction and suppression voltages of an ion implanter similar to the ion implantation system of Fig. 2.
• Plot 300 of Fig. 3, for example, illustrates that an arc discharges extraction voltage 310 from about 2.2KV to near OV at a time 315 at about 0 ms.
• the suppression voltage 320 drops from about -9.3 KV to near OV while the beam current Ibeam 330 drops to near 0 mA.
• the extraction and suppression voltages 310, and 320, respectively fall to near 0 volts, the arc self extinguishes, thereby allowing these voltages to recharge toward their original voltage levels.
• the extraction voltage 310 overshoots this original voltage, and detrimentally delays the recovery of beam current Ibeam 330 until time 345 at about 67 ms wherein extraction voltage 310 has generally recovered. It may be observed from plot 300 that electrode voltage changes have a relatively large and lasting impact on beam current. Thus, Fig.
• the HVHS switch of the present invention accomplishes this goal.
• Fig. 4 illustrates a portion of an exemplary ion implantation system 400 having high positive voltage extraction supply 403 which feeds extraction slits 404, and a high negative voltage suppression supply 406 which feeds suppression electrodes 408 neighboring ground electrodes 409.
• the HV suppression supply 406 has a conventional arc suppression or protection circuit 410, which may use a current limiting resistor 412 to limit the arc current to the suppression electrodes 408, a capacitor 414 to filter and stabilize the voltage of the supply, and a fly-back diode 416 to limit any reverse voltages generated from reactive elements of the circuit during arc on-off cycling.
• the arc protection board 410 may also be used in association with the HVHS switch (e.g., 104 of Fig. 1 ) of the invention to protect the HVHS switch from damage.
• Fig. 5 illustrates an exemplary arc quenching circuit 500 utilized in association. with a high voltage supply of an ion source such as may be used in an ion implantation system in accordance with the present invention.
• arc quenching circuit 500 comprises a high voltage negative supply (Vb) 503 connected in series with a HVHS switch 504 (e.g., a series stack of MOSFET transistors) and a series switch protection circuit 510, which drives a load (e.g., an ion source 120).
• Vb high voltage negative supply
• HVHS switch 504 e.g., a series stack of MOSFET transistors
• a series switch protection circuit 510 which drives a load (e.g., an ion source 120).
• Arc quenching circuit 500 further comprises a current transformer CT 506 that detects a change of current in the supply 503 to the ion source 120, used for example, for producing a quantity of ions that can be extracted in the form of an ion beam (e.g., ion beam 130 of Fig. 1).
• Circuit 500 also includes a trigger control unit 508 for detecting a change of current in the supply current (Iext) 509 to the ion source 120. If a current surge indicative of an arc, is detected in supply current (Iext) 509 by the CT 506, then the trigger control circuit 508 controls HVHS switch 504 to open and quench the arc.
• a capacitance C1 518 within the load e.g., an ion source 120
• the voltage at the load Va
• Va at C1 514 of the load may discharge due to the occurrence of an arc, but the negative supply voltage Vb will remain generally charged at voltage due to isolation by the HVHS switch 504.
• the HVHS switch 504 is protected by parallel and series protection circuits 510 and 515, respectively, to absorb energy from reactive components external to the switch 504 and therefore protect the switch from over-voltage damage.
• the arc quenching circuit 500 of the present invention may be used in any ion implanter, or other such applications as may use a high voltage supply subject to arc discharges at the output of the supply.
• Figs. 6A and 6B illustrate the arc quenching effects of opening and closing a
• the arc as shown in plot 650 of Fig. 6B is much more easily extinguished in the actual vacuum environment than that of the arc tested in air. This is because of the extra heat generated in the ionized air around the arc produced in the air, relative to the arc in the actual vacuum environment.
• plot 600 of Fig. 6A is useful to illustrate the stabilizing effect that the HVHS switch circuit has on maintaining the Vb negative supply voltage even in this more difficult air filled environment.
• Fig. 6A illustrates a plot 600 of the arc quenching effects of opening and closing a HVHS switch 610 (e.g., 504 of Fig. 5) of the arc quenching circuit (e.g., 500 of Fig. 5) of the present invention during arcing of an extraction electrode (e.g., 208 of Fig. 2) associated with an ion source (e.g., 120 of Figs. 1 and 5), as tested in the air.
• FIG. 6A for example, illustrates a voltage 610 across a HVHS switch 504 when closed 610a and when open 610b, the high voltage supply Vb 630 at the supply 503, and the high voltage Va 620 as seen at the load (e.g., 120).
• the high voltage supply Vb 630 Prior to time 0.0, the high voltage supply Vb 630 is at about -6KV, and the high voltage supply Va 620 at the load is also about -6KV.
• an arc occurs on the high voltage supply Va 620 at the load, and the voltage quickly drops from about 6KV at 620a to about 1.6KV at 620b.
• the current detected by CT 506 is received by trigger control circuit 508 and controls HVHS switch 504 to open as shown at 610b. After about 0.6ms, the arc begins to extinguish because the HVHS switch is open, and the supply voltage at the load begins to recover some as shown by Va 620c, and switch voltage 610c.
• Va 62Od maintains at about 1.6KV at 620b until about time 1.75ms when the HVHS switch 504 again closes indicated by switch voltage 610a and Va 620 recharges to about 6KV at 620a.
• the quick recovery of Va 620 is possible because high voltage Vb 630 of HV supply 503 remains relatively stable, isolated by the quick switching action of HVHS switch 504 as controlled by the arc quenching circuit 500 of the present invention.
• Fig. 6B illustrates a plot 650 of the relative amplitude level of signals provided by an arc quenching circuit (e.g., 500 of Fig. 5), in accordance with the present invention during arcing of an extraction electrode (e.g., 208 of Fig. 2) associated with an ion source (e.g., 120 of Figs. 1 and 5), as tested in the actual vacuum environment, for example, of an ion implanter.
• Fig. 6B further illustrates the faraday current detected 660, during the opening and closing of a HVHS switch (e.g., 504 of Fig.
• a HVHS switch e.g., 504 of Fig.
• FIG. 6B further illustrates a voltage 670a across a HVHS switch 504 when the switch is closed at 670a and when the switch is open at 670b, the high voltage supply Vb 630 at the supply 503, and the high voltage Va 620 as seen at the load (e.g., 120).
• the detected faraday current l-faraday is measured at the extraction electrode voltage Vex 670, which is fed by a high positive supply voltage, and as triggered by a Vex trigger control signal 680 derived by the current in the Vex power supply (e.g., from CT 506) , and having a suppression voltage Vsup 690, which is fed by a high negative supply voltage.
• Fig. 6B further illustrates a voltage 670a across a HVHS switch 504 when the switch is closed at 670a and when the switch is open at 670b, the high voltage supply Vb 630 at the supply 503, and the high voltage Va 620 as seen at the load (e.g., 120).
• Vex trigger control signal 680 is at a high level 680a.
• an arc occurs on the high voltage supply (e.g., Va 620), for example, at the Vex electrode, and the. Vex 670 and Vsup 690 voltages quickly drop to low level voltages as shown at 670b and 690b, respectively.
• the current detected by CT 506, for example, is received by trigger control circuit 508 and provides a low level 680b on Vex trigger control signal 680 to control HVHS switch 504 to open as shown at 670b.
• the detected faraday current l-faraday 660 drops to a low current level 660b.
• the Vex trigger control signal 680 returns to the 680a level indicating that the arc has been extinguished, and Vex trigger control signal 680 controls the HVHS switch to re-close, and in response Vex 670 returns to the 670a level.
• the arc quench circuit of the present invention is able to quench an arc in the high voltages electrodes of an ion implanter, for example, and minimize the length of an ion beam glitch to about 0.7ms.
• Fig. 7 illustrates a simplified schematic representation of an exemplary arc quenching circuit 700 used in an ion implanter in accordance with several aspects of the present invention.
• Arc quenching circuit 700 is similar in several ways to that of Figs 1 , 4 and 5, and as such need not be completely described again for the sake of brevity.
• Circuit 700 utilizes HVHS switches (A, B 1 and C) 704 (e.g., a series stack of MOSFET transistors) in three separate high voltage power supplies (Vext 703, -
• Arc quenching circuit 700 also comprises current transformers (CT1 , 2, and 3) 706 for detecting current surges in each respective high voltage supply, and received by trigger control circuits 708 to control switches A, B, C 704 to open upon detection of the current surge indicative of an arc 725 at the respective ion beam electrode, for example, extraction electrode or arc slit 720, suppression electrodes 721 and 722, or ground electrodes 724.
• CT1 , 2, and 3 current transformers for detecting current surges in each respective high voltage supply, and received by trigger control circuits 708 to control switches A, B, C 704 to open upon detection of the current surge indicative of an arc 725 at the respective ion beam electrode, for example, extraction electrode or arc slit 720, suppression electrodes 721 and 722, or ground electrodes 724.
• each independent electrode supply (e.g., Vext 703, -Vsupi 731, and -Vsup2 732) may independently arc to ground or another electrode, thus each HV supply may be protected by another such HVHS switch.
• Arc quenching circuit 700 further comprises arc protection circuits 715 having a current limiting resistor (R1 , 2, and 3) 712, filter capacitor (C1 , 2, and 3) 714, and flyback diode (D1, 2, and 3) 716 to protect the HVHS switches 704 from switching transients and other such overvoltage damage induced by reactive components of the circuits associated with each HV supply.
• arc protection circuits 715 having a current limiting resistor (R1 , 2, and 3) 712, filter capacitor (C1 , 2, and 3) 714, and flyback diode (D1, 2, and 3) 716 to protect the HVHS switches 704 from switching transients and other such overvoltage damage induced by reactive components of the circuits associated with each HV supply.
• Circuit 700 also utilizes a synchronization circuit 740 to sequence and synchronize the reapplication of the supply voltage to each of three respective high voltage electrodes 720, 721 , and 722. For example, it may be determined that synchronization circuit 740 should re-close switches B and C 704 before re-closing switch A. Further, synchronization circuit 740 may provide time delays appropriate for reapplication of each individual HV supply. Any other sequence or timing relationships between the supplies is anticipated, including multiple switch reapplications and/or re-openings with any number of HVHS switches connected in series or parallel with each other or with each HV supply.
• self-adaptive switching and synchronization controls can be used as a variation of the synchronization circuit 740, within the context of the present invention, wherein changing currents, voltages, infrared or other wavelengths of light energy, or other such changes associated with or indicative of an arc 725, are monitored and used to adjust the sequence and/or timings of the synchronization to compensate or further mitigate such arc induced supply variations.
• the HVHS switches can be switched at one or more particular frequencies to modulate or otherwise provide dynamic pulse width control of the several electrode voltages, and/or the beam current in response to the detection of an arc.
• the detection and quenching of electrode arcs the
• HV power supply modulation may also be provided in response to some known non- uniformity in the system (e.g., where a particular beam current results in a predictable non-uniformity). It may also be appreciated that while one use of such modulation is to achieve a uniform dosage on a wafer, it could be used to achieve any predetermined dopant profile, where uniformity is a subset of the general case.
• arc quenching circuit of the present invention may be utilized prior to the implantation as well as during implantation.
• the beam current can be monitored to control the arc quenching circuit or to otherwise regulate a relatively constant beam current in response to HV supply variations when electrode arcing occurs.
• Fig. 8 illustrates an exemplary protection circuit 810 such as may be used across or in series with a HVHS switch 804 to absorb energy from reactive elements external to the respective HV switch 804, and to limit an over-voltage across the switch in accordance with one or more aspects of the present invention.
• the protection circuit 810 also protects the switch 804 and other associated components by dampening any ringing induced by switching transients from the HVHS switch 804.
• Protection circuit 810 is similar to the protection circuit 110 of Fig. 1 and 510 of Fig. 5.
• Protection circuit 810 comprises a series capacitor Cs connected in series with a parallel combination of series diode Ds and series resistor Rs, the protection circuit 810 being wired in parallel with a HVHS switch 804.
• the HVHS switch 804 comprises a HVHS switch (e.g., a series stack of MOSFET transistors) and a diode • Dp connected in parallel with the switch.
• the HVHS switch 804 may be provided, for example, with or without the parallel diode Dp.
• HVHS switches may be connected in series or parallel with each other or with a HV supply to quench an arc that occurs in association with an ion source, an ion implanter, or any other such equipment utilizing high voltage power supplies, for example.
• Fig. 9A and 9B illustrate simplified diagrams 900 and 950, respectively, of wafer scans of the relative scan motion between an exemplary ion beam 130 and a wafer 910, wherein the wafer 910 is moved simultaneously in a vertical direction 920 and a horizontal direction 930 by a motion control system.
• the resulting scan motion provided by the exemplary motion control system produces a compound motion which has a somewhat diagonal scan vector 936 across the wafer 910. These scans repeat each horizontal row and over-scan the edge of wafer 910 each horizontal scan until a load/unload position 935 is achieved past the edge of the wafer 910 at one end of the vertical scan 920. Dotted line 937 indicates an exemplary path of a next scan 937 after the ion beam 130 arrives at the load/unload position 935 at the lower end of the vertical scan 920.
• the ion beam 130 may be disrupted either briefly creating a glitch hole 940 (a short disruption), or for a longer duration creating a glitch strip 960, each glitch having a corresponding loss of dose. Such areas of dose loss may then be repainted in accordance with one or more aspects of the present invention.
• the encoder positions of the horizontal and vertical motors driven by the motion control system may be monitored, so that the initial detection position 940a and final detection position 940b associated with the arc may be recorded.
• the arc quenching circuit would function as previously described to quench the arc between initial detection position 940a and final detection position 940b. Subsequent to the arc detection and quenching, the wafer scanning and ion implantation may continue as usual.
• a repaint process may be initiated, for example, by a modified trigger control circuit (e.g., 508 of Fig. 5, or 708 of Fig. 7), or a modified synchronization circuit (e.g., 740 of Fig. 7), as previously described.
• a modified trigger control circuit e.g., 508 of Fig. 5, or 708 of Fig. 7
• a modified synchronization circuit e.g., 740 of Fig. 7
• Such a modification would further make a trigger control circuit operable to receive a command (see 508 of Fig. 10A, and 1108 of Fig. 11) from the motion control system or the implanter computer to initiate the repaint process.
• the repaint process initially includes turning OFF the ion beam 130 via the
• HVHS switch (e.g., 504, 704) for the ion source (e.g., 120 of Fig. 5) and the extraction/suppression electrodes 720, 722, for example.
• the ion beam 130 or wafer 910 is then moved or rescanned 945 to a first horizontal and vertical scan position (e.g., 940a or 960a) where the arc was initially detected, for example, by first returning the beam to the beginning of the row (horizontal) scan 936 wherein the arc was initially detected. In this way, the scan motion can begin a row as usual prior to encountering the position of the initial arc detection (e.g., 940a or 960a).
• the wafer will then be fully accelerated up to the same speed as that which was present when the arc was initially detected.
• the ion beam 130 is enabled by closing the HVHS switch (e.g., 504, 704), while the wafer 910 is horizontally and vertically scanned 930 and 920, respectively, in front of the ion beam 130.
• the HVHS switch 504, 704 is opened again to disable the ion beam 130.
• the ion beam may be rescanned 945 in the opposite direction of the initial scan direction, for example, starting from the final detection position 940b or 960b, and proceeding in a scan direction to the initial detection position 940a or 960a.
• This direction may not reproduce the dose losses as precisely as those achieved by repainting the ion beam 130 in the same direction as the original scan direction (see the original direction indicated by the arrow for short glitch hole 940 and long glitch strip 960).
• Fig. 10A illustrates an exemplary arc quenching circuit 1000 utilized in association with the high voltage supply 503 of an ion source 120 such as may be used in an ion implantation system (e.g., 200 of Fig. 2) in accordance with the present invention.
• the trigger control circuit 508 has an external trigger input 1010 for externally controlling the triggering of the HVHS switch 504, for example, with a faraday cup current (Ifaraday) input used as a sample of the ion beam current
• Fig. 10B illustrates a faraday cup current (Ifaraday) waveform 1060 such as may be used to provide a trigger voltage 1070 for the external trigger input 1010 to the exemplary arc quenching circuit 1000 of Fig. 10A, such as may be used in accordance with one or more aspects of the present invention.
• a faraday cup current (Ifaraday) waveform 1060 such as may be used to provide a trigger voltage 1070 for the external trigger input 1010 to the exemplary arc quenching circuit 1000 of Fig. 10A, such as may be used in accordance with one or more aspects of the present invention.
• the ion beam 130 is expected to produce a high level faraday current 1060a, and an expected low level trigger voltage 1070a.
• the faraday current 1070 would only be produced at a low level faraday current 1060b, and result in a high level trigger voltage 1070b, which when provided to external trigger input 1010, switches OFF HVHS switch 504 to quench the arc.
• Fig. 11 illustrates an exemplary arc quench controller 1100 having an arc quench circuit 1102, is used in an ion implanter (e.g., 200 of Fig. 2), utilizing a HVHS switch 504 between a high voltage supply 503 and an electrode (not shown) of the implanter 200.
• Arc quench controller 1100 is similar to the arc quenching circuits of
• the arc quench controller 1100 utilizes a switch control circuit 1108 to sequence, control, and synchronize the reestab ⁇ shment of the current and voltage to one or more electrodes from other switches 1110, to determine the duration of arc loss by long glitch detector 1120, and coordinate repaint commands 1130 from a motion control system 1150 or forced switch control commands 1140 from the ion implantation system in accordance with one or more aspects of the present invention.
• the other HVHS switches 1110 may be from other electrode supplies of the same ion implanter, or they may be from other HVHS switches of other similar arc quenching circuits (AQCs), which are not shown. These switches need to be synchronized to ensure the desired order and timing for opening and closing the switches 1110.
• the duration of a glitch, or loss of the ion beam may be detected by a long glitch detector 1120, to determine if the glitch is long enough to require the repaint procedure as described above. Conversely, if a glitch is short enough, a determination may be made to ignore the loss.
• Such a determination level may be set, for example, by the end user of the ion implantation system. If a long glitch (e.g., 960 of Fig. 9B) is detected and a repaint of the ion beam 130 is required, the HVHS switch 504 would be forced OFF during the glitch to quench the arc.
• the repaint process may be initiated upon assertion of the repaint command 1130 from the scan motion control system 1150.
• the HVHS switch control is forced ON/OFF in response to the repaint command 1130, and in response to the positions achieved by the motion control system 1150, and as described previously.
• the implanter system is also provided with the ability to simply turn the ion beam 130 ON or OFF at will, either manually with a switch or by way of command 1140 from one of the implanters control systems, its computer, or by an external input. This is particularly beneficial, after a substantial warm-up time, to be able to turn the beam 130 ON/OFF, for example, when loading or unloading a new wafer 910, during other types of wafer exchange, at the start/end of each wafer scan 936, or in the over-travel regions 965 of each row scan 936 of a wafer 910.
• the arc quench controller 1100 of the present invention facilitates reducing the "beam duty factor" should reduce the particle count on a wafer, because the beam will be used to a greater percentage usefully on the wafer 910 and less on the other surfaces of the implanter adjacent to the wafer 910 (e.g., in the over-travel regions 965).
• arc quench circuits and arc quench controller of the invention has been illustrated in association with a HV power supply for an ion source and an extraction electrode, it will be appreciated that such circuits may also be used in association with the other HV supplies and electrodes of an ion implanter, or other such ion sources and accelerators, including other HV applications subject to HV arcing and are anticipated in the context of the present invention.
• One aspect of the present invention provides a method of quenching an arc and repainting the ion beam is presented and described.
• One implementation of the present invention effectively quenches such high voltage arcs which occur at an electrode of an ion implanter and by opening a high voltage high speed switch wired in series between the electrode and a high voltage supply which provides the electrode potential to control the ion beam.
• the electrode potential is restored, before the HV supply has had a chance to fully discharge.
• any dose losses experienced during the arcing may be restored by returning the ion beam/wafer to the location where the arc occurred, repainting the ion beam over such areas, and toggling the ion beam ON/OFF during the repaint operation using the same HVHS switch.
• One such method 1200 is illustrated in Fig. 12, representing an exemplary method for quenching an arc in an ion implanter
• WMMMMMMM Although the example method 1200 is illustrated and described hereinafter as a series of acts or events, it will be appreciated that the present invention is not limited by the illustrated ordering of such acts or events. In this regard, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein, in accordance with the invention. In addition, not all illustrated steps may be required to implement a methodology in accordance with the present invention. It is further noted that the methods according to the present invention may be implemented in association with the wafers, wafer cassettes, wafer sensor, wafer handling system, and modeling system illustrated and described herein as well as in association with other apparatus and structures not illustrated.
• Method 1200 comprises an example arc quenching method that may be used to extinguish an arc that may occur at an ion beam controlling electrode of an ion implanter (e.g., 200 of Fig. 2), using an arc quenching circuit similar to circuit 1000 of Fig. 10A.
• a wafer 910 may be in the process of being horizontally 930 and vertically 920 scanned at 1210 with an ion beam 130 (either by the wafer or the ion beam moving).
• a current or voltage change e.g., Va 620 of Fig. 6A
• a faraday cup 244 to provide l-faraday 1060 of Fig. 10B associated with the ion beam current Ibeam) at an electrode (e.g., extraction electrode 208 of Fig. 2) of the implanter 200.
• the encoder positions of the horizontal and vertical motors driven by the motion control system (e.g., 1150 of Fig. 11) of the implanter 200 may optionally be monitored at 1230, so that the initial detection position 940a and final detection position 940b associated with the arc may be recorded for an optional repaint operation (e.g., method 1300 of Fig. 13).
• the duration of such an arc may be optionally detected (e.g., by detector 1120 of Fig. 11) and used to determine if a subsequent repaint is desired.
• the arc is quenched at 1250, by opening a HVHS switch 504 connected between a high voltage supply 503 and the electrode 208 of the implanter 200, thereby interrupting the arc current to the electrode 208 and quenching the arc.
• the HVHS switch 504 is again closed at 1260 to reconnect the high voltage supply to the electrode and to re-establish the ion beam.
• the wafer scanning and ion implantation may continue as usual, for example, until the end of a row scan 936, or the end of a vertical scan 920, for example, at the load/unload position 935, or until the end of all the scans anticipated for a wafer 910.
• a repaint process may be initiated, for example, by switch control unit 1108, or a modified synchronization circuit (e.g., 740 of Fig. 7), as previously described.
• the switch control circuit 1108 is operable to receive a command (see 508 of Fig. 10A, and 1108 of Fig. 11) from the motion control system 1150 or the implanter computer to initiate the repaint process.
• Fig. 13 illustrates an exemplary method 1300 for repainting the ion beam 130 to recover dose loss due to arcing in an ion implanter 200, for example, using the arc quenching controller 1100 of Fig. 11 in accordance with one or more aspects of the present invention.
• Method 1300 comprises an example ion repainting method that may be used to restore the ion dose loss during arcing in an ion implanter (e.g., 200 of Fig. 2), using an exemplary arc quenching controller 1100 of Fig. 11.
• an ion implanter e.g., 200 of Fig. 2
• the repaint process may be initiated.
• the ion beam 130 is again turned OFF, for example, using the HVHS switch ⁇ e.g., 504, 704) to the ion source (e.g., 120 of Fig. 5) and the extraction/suppression electrodes 720, 722, for example.
• the ion beam 130 or wafer 910 is then moved or rescanned 945 at 1320, to a first horizontal and vertical scan position (e.g., 940a or 960a) where the arc was initially detected, for example.
• This movement to the initial scan position 940a/960a may be done by first returning the beam to the beginning of the row (horizontal) scan 936 wherein the arc was initially detected. In this way, the scan motion can begin a row as usual prior to encountering the position of the initial arc detection (e.g., 940a or 960a).
• the wafer will then be fully accelerated up to the same speed as that which was present when the arc was initially detected.
• the ion beam 130 is also enabled at 1320 by closing the HVHS switch (e.g., 504, 704).
• the wafer 910 is horizontally and vertically scanned 930 and 920, respectively, in front of the ion beam 130 until a second horizontal and vertical scan position (e.g., 940b or 960b) associated with the final detection of the arc is encountered, and the HVHS switch 504, 704 is opened again to disable the ion beam 130.

Landscapes

• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Physical Vapour Deposition (AREA)
• Electron Sources, Ion Sources (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

Family

ID=38541616

Family Applications (1)

Country Status (3)

Cited By (4)

Families Citing this family (3)

Citations (4)

Family Cites Families (4)

• 2007
  • 2007-03-09 JP JP2009501446A patent/JP5805930B2/ja active Active
  • 2007-03-09 WO PCT/US2007/006069 patent/WO2007111822A2/en active Application Filing
  • 2007-03-14 TW TW96108749A patent/TWI425548B/zh active

Patent Citations (4)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events