I am looking for a comparison of a diffusion pump pumped vs. turbomolekular pumped chamber and the impact (graph) of resisual gas contamination rate, the leak- and desproption rate vs. sputter depsotion rate and their impact of the contamination on Aluminum film stress
Hi, seeing your question I am reminded of a general rule-of-thumb that at 10-6mbar a monolayer of contaminants per second can accumulate on a thin film. Your diffusion pump and turbo pump will typically reach these vacuum levels. Contamination of thin films is obviously impacted by residual gas pressure, so anything you can do to lower your residual gas pressure will help, i.e. chamber baking, cold traps etc. Other ways to reduce contamination includes, heated substrates and increased deposition rates. Regarding thin film stress, this can be addressed with sputter gas pressure where reflected neutrals can result in atomic peening or Ar impregnation, providing compressive or tensile stress. One way to assess residual thin film stress is to deposit onto Mica sheets and look how the Mica curls with your film.
I hope this helps, good luck.
some addition to what Martin wrote.
In the case of using a turbopump, the residual atmosphere consists mainly of water and hydrogen (see MS attached, 2 days of pumping with a turbopump). In the case of using a diffusion pump, the partial pressures of water and hydrogen should be less, but hydrocarbons (oil vapors) should appear. Accordingly, the composition of the films will be different impurities.
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