Berlin 2015 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 26: Layer Properties: Electrical, Optical, and Mechanical Properties
DS 26.13: Vortrag
Mittwoch, 18. März 2015, 18:15–18:30, H 2032
Comparison of Al2O3 passivation layers by RF magnetron sputtering and ALD deposition — •Franz P. G. Fengler1, Daniel K. Simon1, Paul M. Jordan1, Thomas Mikolajick1,2, and Ingo Dirnstorfer1 — 1NaMLab gGmbH, 01187 Dresden, Germany — 2Lehrstuhl für Nanoelektronische Materialien, TU Dresden, 01187 Dresden, Germany
Decreasing wafer thicknesses of latest high efficient solar cells cause an increasing demand for superior surface passivations. Due to a high content of negative fixed charges Al2O3 became the material of choice for p-type silicon. Today it is mainly deposited by atomic layer deposition (ALD) and plasma enhanced chemical vapour deposition. Both processes are rather slow and require toxic gases e.g. Trimethylaluminum. An alternative is the physical vapor deposition (PVD) by means of magnetron sputtering. However, silicon passivated with PVD-films typically do not achieve lifetimes in the millisecond range. This study will investigate the reasons for the low performance by using structural, lifetime and capacitance-voltage measurements to analyze the difference of PVD- and ALD-layers. It will be shown that the content of oxygen and the distribution of hydrogen in the as-grown layers are crucial for the passivation performance. ALD and PVD layers significantly differ in density, which influences the hydrogen transport within the layer during the post deposition anneal. As a consequence, a PVD process with a low percentage of oxygen is needed in combination with an anneal in hydrogen containing atmosphere.