Programm Photovoltaik Ausgabe 2008 ... - Bundesamt für Energie BFE

5/6
Large area cluster deposition systems
The KAI-M system has been assembled and started operation during the first 6 months of 2007.
Figure 5 shows the KAI-M deposition system installed in the clean room and fully operational (with one
chamber). The second half of 2007 has been used to check the system for various layer depositions.
Transfer of processes for a-Si:H and �c-Si:H from the KAI-S to the KAI-M has been performed as well
as first device fabrication. The system is now fully operational and can be used for R&D. The second
chamber which is already present will accommodate a modified version of the KAI-M plasma box and
be put in operation next year.
Fig. 5: picture of large area KAI-M cluster deposition tool with one operational chamber.
In this KAI-M system, two plasma diagnostic tools have been implemented and are used:
1. Optical emission spectroscopy (OES): This characterization tool allows a qualitative analysis of
the optical emission of plasmas used for silicon thin film deposition. The integrated intensity of
the H� and H� emission lines can be related to the electron temperature (under certain experimental
conditions) and allow a monitoring of the plasma conditions which are important for
�c-Si:H growth.
2. Peak to peak voltage measurement on RF driven electrode: The second characterization tool
allows a quantitative measure of the peak to peak voltage at the RF driven showerhead electrode
in the KAI-S deposition system. This parameter is useful as it is related to the plasma potential
Vp and to the potential drop across the plasma sheath. Thus, it can be used to estimate or
compare the ion bombardment energy on the surface of the growing film, provided some assumptions
are made as well.
Further diagnostics tools for powder formation as well as for silane depletion monitoring are being
considered and will probably being set-up next year.
Results on ultra-large area (> 1m 2 )
Even though not the topic of this report, it is worth mentioning the improvements at the industrial level
in this project. In particular the company OC Oerlikon, could demonstrate a first large area micromorph
module (1.3x1.4 m 2 ) at the 22 nd EUPVSC conference in Milano. This module with an apperature area
of 1.337 m 2 , had an initial aperture area efficiency of 9.46% (cf. Fig. 6). More details are reported in
[6].
ATHLET, N. Wyrsch, IMT Seite 59 von 288