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Tergeo plasma cleaner operator’s manual
Revision: B3, Year 2020
8.14 Process uniformity in the chamber.
There are many factors that can impact the process uniformity. Uniformity can be influenced by the
plasma radical production and recombination, gas transportation and sample loading effect. The gas
comes in from the holes on the front right side of the chamber. Uniformity will be better if the samples
is placed far away from the gas entrance port, especially for remote mode plasma processing. We
recommend placing the sample around or beyond the middle point in the chamber.
For remote mode plasma, place the samples deeper into the chamber. If necessary, place the samples
vertically to improve the uniformity. In the remote mode plasma processing, the atomic oxygen and
hydrogen radicals are generated in the remote plasma source, the radicals will then enters the main
chamber. If the pressure in the main chamber is too high, the atomic radicals will recombine to become
more stable molecules and loss the efficacy. At the pressure of 1.0 Torr, the mean free path is only
around 0.1mm. The mean free path will increase to 1mm when the pressure is reduced to 0.1 Torr.
Therefore, the density of the radicals will gradually reduce from the front of the chamber (the holes for
the remote plasma source) to the back of the chamber (pumping port). Placing the samples vertically
deep in the chamber can improve the process uniformity for remote mode plasma processing. In the
remote mode plasma process, keep the chamber pressure below 1.0Torr to reduce the recombination
loss. Otherwise, there won’t have much reactive radicals left beyond the entrance port of the remote
plasma source.
The uniformity of the direct mode plasma is usually better than the remote mode plasma because the
radicals are produced throughout the chamber space. For uniformity critical process, place the sample
flat on the quartz sample holder at a location around or slightly over the middle point of the chamber.
