Control and optimization of thermal oxidation processes for industrial solar cell fabrication

We present a systematic process control procedure that enables an integrated process optimization of wet chemical cleaning and subsequent thermal oxidation processes. Our approach uses distinct experiments to reveal the impact of individual parameters on the effective minority carrier lifetime. Special focus is put on an application in a production line. Therefore, both wetchemical processing and thermal oxidation take place in industry-size equipment. On 1 cm p-type floatzone (FZ) wafers with sawdamage etched surfaces, surface recombination velocities as low as (26±3) cm/s directly after oxidation and (13±1) cm/s after annealing in forming gas are achieved for an optimized process sequence.