| AVS 57th International Symposium & Exhibition | |
| Energy Frontiers Topical Conference | Monday Sessions |
| Session EN+PS-MoM |
| Session: | Plasmas for Photovoltaics & Energy Applications |
| Presenter: | T. Tanaka, Applied Materials Inc. |
| Authors: | T. Tanaka, Applied Materials Inc. J. Kudela, Applied Materials Inc. E. Hammond, Applied Materials Inc. C. Boitnott, Applied Materials Inc. Z. Chen, Applied Materials Inc. J.A. Kenney, Applied Materials Inc. S. Rauf, Applied Materials Inc. |
| Correspondent: | Click to Email |
Processing a large area substrate in a capacitively coupled plasma (CCP) reactor is becoming increasingly more difficult as the driving frequency required by the process is becoming higher and the size of the substrates is becoming larger. At the VHF (very high frequency) range the wave length of the driving signal is approaching the size of the substrate, and the resulting standing wave causes a severely non-uniform process. In this presentation, we will present a novel approach using magnetic boundary conditions in conjunction with phase modulation between multiple power feed points to improve process uniformity for a CCP reactor operating in the VHF range. The substrate size we consider is Gen 8.5 (2.2 m × 2.6 m substrate) and the VHF power applied to generate the plasma is 40 and 60 MHz. At 60 MHz, with the vacuum wavelength of 5 m, the size of the substrate is approximately ½ of the vacuum wavelength. An electromagnetic simulation with a pseudo plasma showed that, when 60 MHz is applied in a conventional manner, i.e. it is fed from the center of the back of one of the electrodes, it generates a dome shape electromagnetic field profile, which falls off sharply to almost zero at the voltage node before rising again towards the edges. A similar field pattern was also generated even when the VHF was fed from two feed points located at the opposing edges. The plasma distribution pattern measured with a 4 × 8 grid of optical emission spectroscopic (OES) probes revealed that the plasma was localized in the center when VHF the signal applied to the feed points were in phase. To modify the wave propagation pattern to change the shape of the standing wave in the central area, we placed ferrite material along two of the edges (edges that are away from the feed points) of the powered electrode. In this case, the peak in the central area was significantly stretched towards the ferrite-lined edges. We also found that the stretched “bar” of plasma could be moved over the substrate area by dynamically modifying the relative phase between the feed points in a manner similar to the technique employed by Yamakoshi etal. [1], and effectively distribute the processing plasma to much larger area.
[1] H.Yamakoshi etal. Appl. Phys. Lett. 88, 081502 (2006)