Sheath overlap during very large scale plasma source ion implantation
- MS-E526, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
Measurements of plasma source ion implantation have been performed on a large target of complex geometry. The target consists of 1000 aluminum, automotive piston surrogates mounted on four racks; total surface area is over 16 m{sup 2}. The four racks are positioned parallel to each other, 0.25 m apart, in an 8 m{sup 3} vacuum chamber. The racks of pistons are immersed in a capacitive radio frequency plasma, with an argon gas pressure of 20{endash}65 mPa. Langmuir probe measurements indicate that the plasma density profile is highly nonuniform, due to particle losses to the racks of pistons. The plasma ions are implanted into the pistons by pulse biasing the workpiece to negative voltages as low as {minus}18 kV for up to 20 {mu}s. During the voltage pulse, the high-voltage sheaths from adjacent racks of pistons converge towards each other. At plasma densities less than 10{sup 9}thinspcm{sup {minus}3} the sheaths are observed to overlap. Measurements of the sheath overlap time are compared with standard analytic theory and with simulations run with a two-dimensional particle-in-cell code.
- OSTI ID:
- 664660
- Journal Information:
- Journal of Applied Physics, Vol. 84, Issue 11; Other Information: PBD: Dec 1998
- Country of Publication:
- United States
- Language:
- English
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