Bean scanning and method of use for ion implantation

DETAILED DESCRIPTION OF THE INVENTION The present invention in the functional context of an ion implantation system may be seen in FIG.
1.
A high voltage terminal 2 is held at high potential relative to ground by high voltage power supply 4.
Terminal 2 houses the apparatus required to form a beam of ions of desired species.
In common practice a gaseous feedstock of the desired species is employed.
To this end, a source gas produced from gas handling system 6 is directed to ion source 8.
A typical ion source will require a power supply 10 to sustain an ionizing discharge, power supply 12 to impose an axial magnetic field across the discharge region, and extraction supply 14 and vernier 14' cooperating with extraction electrode 16 to shape the electric field at the aperture of the source for effective removal of a well defined high current ion beam.
A more detailed description of ion source techniques is outside the scope of this work.
See for example L.
Valyi, "Atom and Ion Sources, Wiley-Interscience, 1978.
" The beam 18 diverging from the ion source 8 is momentum analyzed in analyzer magnet 20, the latter energized from analyzer power supply 22.
Analyzed beam passes through analyzer exit slit 24 and then to accelerator tube 26 where it encounters a carefully designed field gradient from the high voltage terminal 2 to ground potential.
Optical elements, such as a quadrupole triplet 28, 30, 32, and associated control system 34, operate to produce a spatial-energy focus at a desired image plane.
Two sets of electrostatic deflection plates, 40 and 42, arbitrarily labeled y and x respectively serve to direct the beam over the desired area of the image plane.
The waveform applied to the respective deflection plates and their synchronization to form the appropriate scanning program is accomplished by scanning system 43.
The quiescent beam is deflected sufficiently to completely separate neutral beam 44 (arising from charge-exchange collisions with residual gases) from the charged beam.
Target chamber 46 contains beam defining apertures, beam monitoring and integrating apparatus and equipment for introducing the wafer substrate in the vacuum system and aligning same with respect to the target plane