Evaluation of Process Damage to Crystalline Silicon by Transparent Conductive Oxide Film Deposition

We evaluated the damage to crystalline silicon (c-Si) induced by transparent conductive oxide film (TCO) deposition processes in indium tin oxide (ITO)/ hydrogenated amorphous silicon (a-Si:H)/Si structure. ITO was deposited by reactive plasma deposition (RPD) and sputtering techniques, respectively. After ITO deposition, the post-annealing at 200°C for 30 min in the air atmosphere was also carried out. Carrier lifetime of both samples decreases drastically after ITO deposition, and is significantly recovered by post-annealing both for RPD and sputtering. The plasma processes should produce recombination active defects on the sample surface or in the c-Si substrate resulting in carrier lifetime deterioration. These defects might be relatively small scale. Photoluminescence (PL) spectroscopy revealed the formation of so-called “irradiation-induced defects” that are formed typically after electron beam and ion irradiation with the peak positions at deep levels of 0.767 eV and 0.614 eV in the samples deposited by the RPD technique. Complex defects of impurity carbon and oxygen atoms were considered to be formed in c-Si by the RPD technique. These defects were eliminated after post-annealing. These irradiation-induced defects act as recombination active centers and may cause the deterioration of the conversion efficiency in c-Si solar cells.