Bushing unit with integrated conductor in ion accelerating device and related method

An ion accelerating device includes a series of bushing units and a series of resistor circuit units. Each resistor circuit unit is coupled to one bushing unit. A bushing unit includes three integrated conductors to establish connections to the coupled resistor circuit unit and to an immediately adjacent bushing unit such that a voltage to the bushing unit may be degraded by the resistor circuit unit before reaching the lens and that two bushing units may contact one another directly.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to ion implantation, and more particularly, to an ion accelerating device including a bushing unit with integrated conductors, and related method.

2. Related Art

Ion implantation is a standard technique for introducing conductivity altering impurities into, or doping, semiconductor wafers. A typical ion implantation process uses an energetic ion beam to introduce impurities (ions) into semiconductor wafers. During ion implantation, a source feed material is energized to generate an ion beam, and the generated ion beam needs to be accelerated by an acceleration column. An acceleration column is required to accelerate an ion beam of 670 kV. Preferably, the acceleration is accomplished by the ion beam passing through seven lenses internal to the acceleration column with voltages graded across the lenses. However, the currently available physical spacing between adjacent lenses is insufficient to follow the proper high voltage design rules under the conventional design practice for an acceleration column.

SUMMARY OF THE INVENTION

An ion accelerating device includes a series of bushing units and a series of resistor circuit units. Each resistor circuit unit is coupled to one bushing unit. A bushing unit includes three integrated conductors to establish connections to the coupled resistor circuit unit and to an immediately adjacent bushing unit such that a voltage to the bushing unit may be degraded by the resistor circuit unit before reaching the lens and that two bushing units may contact one another directly.

A first aspect of the invention is directed to an ion accelerating device of an ion implantation system, the ion accelerating device comprising: a first bushing unit including a first conductor, a second different conductor and a lens mounting plate; and a first resistor circuit unit coupled to the first bushing unit; wherein the first conductor connects an input terminal of the first bushing unit to an input terminal of the first resistor circuit unit, and the second conductor connects an output terminal of the first resistor circuit unit to an input terminal of the lens mounting plate.

A second aspect of the invention is directed to an accelerating column bushing unit, the bushing unit comprising: a lens mounting plate; and a first conductor and a second different conductor; wherein the first conductor connects an input terminal of the bushing unit to an input terminal of a resistor circuit unit coupled to the bushing unit, and the second conductor connects an output terminal of the resistor circuit unit to an input terminal of the lens mounting plate.

A third aspect of the invention is directed to a method of providing a voltage supply to a lens in an ion accelerating device, the method comprising: providing a series of bushing units and a series of resistor circuit units, each resistor circuit unit coupled to one bushing unit, each bushing unit including a first conductor, a second different conductor and a lens mounting plate; connecting an input terminal of one bushing unit to an input terminal of a respective resistor circuit unit using the first conductor; and connecting an output terminal of the respective resistor circuit unit to an input terminal of the lens mounting plate of the bushing unit using the second conductor to provide voltage to a lens installed on the lens mounting plate.

The foregoing and other features of the invention will be apparent from the following more particular description of embodiments of the invention.

DETAILED DESCRIPTION

1. Ion Implantation System Overview

With reference to the accompanying drawings,FIG. 1shows an illustrative ion implantation system10. Ion implantation system10includes an ion beam generating sub-system2for generating and transmitting an ion beam4, through ion beam filtering sub-system5, ion beam scanning sub-system6, to a target sub-system8. Ion beam generating sub-system2may include any now known or later developed ion beam generator such as those available from Varian Semiconductor Equipment Associates. Typically, target sub-system8includes one or more semiconductor targets12(e.g., a wafer) mounted to a platen14. Characteristics of platen14and, hence, target12, may be controlled by a platen drive assembly (not shown) that rotates target12, and by a target vertical scan position controller18that controls the vertical position of target12. Ion implantation system10may include additional components known to those skilled in the art. It will be understood that the entire path traversed by ion beam4is evacuated during an ion implantation.

Besides the above-described components, ion beam generating sub-system2may include a gas flow40, an ion beam source42, an extraction manipulator44, a source filter magnet46, and an accelerating/decelerating column48. Source filter magnet46is preferably positioned in close proximity to ion beam source42. Extraction manipulator44is positioned between source filter magnet46and ion beam source42. Acceleration/deceleration column48is positioned between source filter magnet46and mass analyzer50.

Ion beam filtering sub-system5may include a mass analyzer50including, for example, a dipole analyzing magnet52with a semicircle radius53, a mass resolving slit54having a resolving aperture56. As is well known in the art, ion beam4may include different combinations of ions in different stages of the path it traverses.

Scanning sub-system6may include, for example, a scanner60and an angle corrector62. Scanner60, which may be an electrostatic scanner, deflects filtered ion beam4.

Although an illustrative ion implantation system10has been illustrated above, it should be understood by those skilled in the art that any now known or later developed system to generate and scan ion beam4may be used for the current invention. It should be understood that the current invention can be used with any now known or later developed process and methods of ion implantation.

2. Ion Accelerating Device

Referring toFIG. 2, a schematic three-dimensional view of an ion accelerating device100is shown. Accelerating device100may implement accelerating/decelerating column48ofFIG. 1. According to one embodiment, ion accelerating device100includes multiple (or a series of) accelerating column bushing units (bushing unit)102(8 are shown) and multiple (or a series of) resistor circuit units104(7 are shown). Each resistor circuit unit104may be attached/coupled to one bushing unit102at the outside of the latter. Bushing units102and resistor circuit units104may not correspond one-to-one. For example, some bushing units102may not be coupled to resistor circuit units104. A resistor circuit unit104functions to, e.g., degrade an input voltage by a preset amount and output a degraded voltage at its output terminal. That is, an output voltage of a resistor circuit unit104is lower than an input voltage thereof by a preset amount. The preset degrading amount is controllable and adjustable. According to one embodiment, a resistor circuit unit104degrades an input voltage by approximately 95 kV.

According to one embodiment, as shown inFIG. 2, ion accelerating device100includes eight bushing units102(102ato102h) coupled at one end to, e.g., a filter magnet46ofFIG. 1, and coupled at the other end to, e.g., mass analyzer50ofFIG. 1. Each two immediately adjacent bushing units102, e.g.,102aand102b, contact one another directly. That is, there is no physical spacing between two immediately adjacent bushing units102. Seven resistor circuit units104(104a-104g) are coupled, one-to-one, to the first 7 bushing units102(102a-102g). InFIG. 2, the dotted lines indicate the direct contacts between the immediately adjacent bushing units102.

Turning toFIG. 3, a three dimensional view of a bushing unit102is shown with a cross-sectional view in the y-z plane (FIG. 2). As shown inFIG. 3, bushing unit102includes a hollow shaped base106of insulation materials. All other components of bushing unit102are all positioned within base106. Base106includes an exterior surface (outside)108that contacts the atmosphere, and an interior surface (inside)110that contacts a high vacuum interior environment.FIG. 3shows that bushing unit102, specifically base106, has an approximately circular overall shape for illustration purposes. It should be appreciated that other shapes of base106are also possible and are included in the invention. Resistor circuit unit104is coupled to, e.g., mounted to, bushing unit102at exterior surface (outside)108. Bushing unit102includes a lens mounting plate112on interior surface (inside)110. As is appreciated, lens mounting plate112functions to mount and provide voltage to a lens146(shown inFIG. 5).

As shown inFIG. 3, bushing unit102includes an input conductor114, an intermediate conductor116, and an output conductor118. The dotted lines of conductors114,116and118indicate that they are positioned within base106. Input conductor114connects an input terminal122of bushing unit102to an input terminal124of resistor circuit unit104. The connection may be implemented in any manner, and all are included in the invention. For example, input conductor114and input terminal122of bushing unit102may be integrated. That is, input terminal122is part of input conductor114. In addition, the connection between input conductor114and input terminal124of resistor circuit unit104may be implemented by mating features of the two. For example, input conductor114may include a threaded hole to mate with/receive a threaded fastener passing through input terminal124of resistor circuit unit104. Please note, in the current description, the terms “input terminal” and “output terminal” are all defined with respect to voltage paths to and through the respective units and components (e.g., bushing units102, resistor circuit units104, and lens mounting plates112). For example, input terminal122of bushing unit102receives voltage input to bushing unit102.

Intermediate conductor116connects an output terminal126of resistor circuit unit104and an input terminal128of lens mounting plate112. Similar to input conductor114, intermediate conductor116may be integrated to input terminal128of lens mounting plate112, and may have a mating feature, e.g., a projection portion, to be mated with a respective mating feature, e.g., a recess portion, of output terminal126of resistor circuit unit104. It should be appreciated that the scope of the invention is not limited by any specific manner of connection.

Output conductor118is coupled to an output terminal130of lens mounting plate112. According to one embodiment, output conductor118is integrated to output terminal130of lens mounting plate112. Output conductor118is also designed to be coupled to an input terminal122of another bushing unit102(shown inFIG. 4) such that when two bushing units102, e.g.,102aand102bofFIG. 2, are assembled together as in ion accelerating device100ofFIG. 2, output conductor118of bushing unit102aconnects output terminal130of lens mounting plate112of bushing unit102ato input terminal122of bushing unit102b. The coupling between output conductor118of bushing unit102aand input terminal122of bushing unit102bis direct such that bushing units102aand102binclude no physical spacing therebetween. According to one embodiment, output conductor118of bushing unit102aand input terminal122of bushing unit102binclude mating features to mate with one another. For example, output conductor118of bushing unit102amay include a projection portion, e.g., an alignment pin, to be received by a recess portion of input terminal122of bushing unit102b. According to one embodiment, the alignment pin of output conductor118is movable to facilitate the coupling between output conductor118of bushing unit102aand input terminal122of bushing unit102b.

FIG. 4shows a cross-sectional view at the x-z plane (FIG. 2) of output conductor118of bushing unit102acoupled to input terminal122of bushing unit102b. The dotted curved lines indicate thatFIG. 4shows only a portion of bushing units102aand102b. As shown inFIG. 4, output conductor118of bushing unit102aincludes an alignment pin132to be received/mated to recess134of input terminal122of bushing unit102b. According to one embodiment, bushing units102are similar to one another regarding output conductor118and input terminal122. As such, bushing units102can be coupled together to form ion accelerating device100ofFIG. 2. Adjacent to a contact136between each two immediately adjacent bushing units102, ion accelerating unit100includes a high vacuum seal-O-ring140. As is appreciated, high vacuum seal-O-ring140facilitates forming a high vacuum interior environment of ion accelerating device100(FIG. 2).

As described above, resistor circuit unit104degrades an input voltage by a preset amount.FIG. 5shows an illustrative example of this stepped voltage degrading achieved by the current invention. InFIG. 5, ion accelerating device100is shown in a cross-sectional view in the x-z plane (FIG. 2). For this illustrative example, seven resistor circuit units104(104a-104g) are coupled one-to-one to the first seven bushing units102(102a-102g), respectively. As such, voltages provided to lenses146mounted to bushing units102(specifically lens mounting plates112of bushing units102) degrade from bushing unit102ato bushing unit102gin a stepped manner. According to one embodiment, the voltages provided to lenses146of ion accelerating device100grade equally across lenses146ato146g. As such, each resistor circuit unit104degrades the respective input voltage by the same amount, for example, approximately 95 kV. According to one embodiment, an input voltage of 670 kV is provided to ion accelerating device100at the input terminal122(shown inFIG. 3) of the first bushing unit102a. The respective input conductor114(shown inFIG. 3) connects this input voltage to the respective resistor circuit unit104a. Resistor circuit unit104adegrades the voltage by 96 kV (i.e., approximately 95 kV) and outputs a voltage of 574 kV to lens mounting plate112aof bushing unit102athrough intermediate conductor116(shown inFIG. 3). This voltage of 574 kV is provided to the first lens146aof first bushing unit102a. Output of lens mounting plate112aof bushing unit102ais connected to input terminal122(seeFIG. 4) of bushing unit102bthrough output conductor118(seeFIG. 4) of bushing unit102a, and provides a voltage of 574 kV to bushing unit102b. The 574 kV voltage supply is then degraded by resistor circuit unit104bby 96 kV and a voltage of 478 kV is provided to the second lens146bof second bushing unit102b. Similarly, lenses146cto146gof bushing units102cto102g, respectively, receive graded voltages of 382 kV, 286 kV, 190 kV, 94 kV, and 0 kV, respectively. It should be appreciated that the specific voltage numbers provided in the above example are only for illustration purposes and do not limit the scope of the invention.

Bushing units102place all voltage paths to the respective lenses inside bushing units102(see, e.g.,FIG. 3), which greatly simplifies the assembly of ion accelerating device100. In addition, bushing units102can be bolted to one another with no metal flanges in between, which helps to maintain the high vacuum interior environment of ion accelerating device100(FIG. 2). Moreover, as lenses are connected as a complete in series electrical circuit with no wires or springs required to make electrical connections with the lenses, it is easier to monitor the voltage supplies to each lens to detect the operating conditions, e.g., a voltage drop out. Other advantages may also be appreciated based on the above described design of ion accelerating device100, bushing unit102and resistor circuit unit104.