Radiant energy – Inspection of solids or liquids by charged particles – Analyte supports
Reexamination Certificate
1999-04-20
2001-03-27
Nguyen, Kiet T. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Analyte supports
C250S492210
Reexamination Certificate
active
06207959
ABSTRACT:
FIELD OF THE INVENTION
This invention is concerned with improvements in or relating to ion implanters.
BACKGROUND OF THE INVENTION
Ion implanters are commonly used in the manufacture of semiconductor and metallic products for implanting ions into semiconductor or metallic substrates to change the conductivity of the material in such substrates or in predefined regions thereof. Ion implanters generally comprise an ion beam generator for generating a beam of ions, and means for selecting a particular species of ions in the ion beam and for directing the ion beam through a vacuum chamber onto a target substrate supported on a substrate holder.
In typical prior art implanters, for sequentially processing single wafers, such as are disclosed in U.S. Pat. Nos. 4,929,840, 4,975,586 and 5,003,183, the substrate holder is mounted for rotation so as to rotate the holder in front of the ion beam, with the substrate holder being rotatable about a first axis extending substantially along a wafer diameter in the plane defined by the wafer surface, and about a second axis perpendicular to the first axis and extending through the centre of the wafer. The drive systems providing for rotation of the wafer support are described as being operable independently of one another and include stepper motors mounted outside the vacuum chamber.
The motor for rotating the wafer holder about the wafer axis is coupled to the wafer holder via two relatively lengthy drive shafts coupled by a belt transmission, the final of the two drive shafts being coupled to the wafer holder by a bevel gear arrangement.
In U.S. Pat. No. 5,229,615, there is disclosed a single wafer ion implanter in which a substrate holder, or platen assembly, is mounted for rotation about the wafer axis on an arm and is coupled to a motor by a chain drive system. The arm has a housing containing the motor and is arranged also to enclose the chain drive system. The resulting arm is bulky in cross-section and relatively heavy.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide an implanter with a scanning arm assembly, enabling rotation of the wafer holder about the wafer axis, which is lighter and more reliable.
The invention provides an ion implanter for sequentially processing single semiconductor wafers, comprising a scanning arm extending along a first axis between an outer end and an inner end, a wafer holder mounted on the inner end of said arm to hold a wafer in a plane generally parallel to said first axis and arranged for rotation relative to the arm about a second axis centered on and perpendicular to the plane of a wafer on the wafer holder, a scanning mechanism connected to the outer end of said arm for repeatedly reciprocating the arm transversely of said first axis to scan a wafer on the wafer holder to and fro across an ion beam, a rotary motor mounted in the scanning arm inwardly of said outer end thereof, the rotary motor having its axis of rotation extending in the direction of said first axis and perpendicular to said second axis, and a right angle rotary drive mechanism connecting the motor to the wafer holder for controlling rotation of the wafer holder about said second axis.
By mounting the drive motor for the wafer holder in the scanning arm with the axis of the motor aligned with the scanning arm axis, the cross-sectional profile of the scanning arm can be substantially reduced. Importantly also, the right angle drive mechanism connecting the motor to the wafer holder is less bulky, extends over a shorter distance, and is more reliable.
Preferably the right angle rotary drive mechanism comprises a right angle direct drive gear driven by the motor and a belt drive interconnecting the right angle gear and the wafer holder.
The rotary drive mechanism may provide a reduction ratio of R:1 (where R is >1), between the motor and the wafer holder, and further include a hard stop limiting rotation of the motor to a range of substantially R turns, such as to limit rotation of the wafer holder to a maximum of just over 360°.
In some applications, the wafer holder may include electrical components, such as electrodes on the platen of the wafer holder for holding the wafer to the wafer holder by electrostatic force. A flexible conductor element may then be employed to provide electrical connections from the scanning arm to the electrical components of the wafer holder, said flexible conductor element being coiled about said second axis to accommodate rotation of the wafer holder by coiling and uncoiling.
The present invention also provides an ion implanter for sequentially processing single semiconductor wafers comprising a wafer holder mounted for rotation about an axis centred on and perpendicular to the plane of a wafer on the wafer holder, a rotary motor, and a drive mechanism connecting the motor to the wafer holder to control rotation thereof about said axis, said drive mechanism providing a reduction ratio R:1, where R is >1, between the motor and the wafer holder, and a hard stop limiting rotation of the motor to a range of substantially R turns such as to limit rotation of the wafer holder to a maximum of just over 360°.
The invention still further provides an ion implanter for sequentially processing single semiconductor wafers comprising a wafer holder including electrical components and mounted for rotation about an axis centred on and perpendicular to the plane of a wafer on the wafer holder, a motor, a drive mechanism connecting the motor to the wafer holder for controlling rotation thereof about said axis, and a flexible conductor element to provide electrical connections to the electrical components of the wafer holder, said flexible conductor element being coiled about said axis to accommodate rotation of said wafer holder by coiling and uncoiling.
The present invention still further provides an ion implanter for sequentially processing single semiconductor wafers, comprising a scanning arm extending along a generally horizontal axis between an outer end and an inner end, a wafer holder mounted on the inner end of said arm to hold a wafer in a plane generally parallel to said horizontal axis, a scanning mechanism connected to the outer end of said arm for applying a repeated reciprocating linear motion to the arm maintaining said axis generally horizontal, said linear motion being transverse to said axis to scan a wafer on the wafer holder to and fro through an ion beam, and a tilt adjusting mechanism for rotating the scanning mechanism about an axis parallel to said horizontal axis of the scanning arm for adjusting the angle to the vertical of said linear reciprocating motion applied by said scanning mechanism, wherein the outer end of said scanning arm is mounted for rotation of the arm about said horizontal axis of the arm relative to said scanning mechanism.
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patent: WO9913488 (1999-03-01), None
Satoh Shu
Smick Theodore H.
Applied Materials Inc.
Boult Wade & Tennant
Nguyen Kiet T.
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