Aluminum-induced crystallization: Nucleation and growth process

The formation of polycrystalline silicon (poly-Si) films by Al-induced crystallization (ALILE process) was studied in situ by optical microscopy. The characteristic feature of this process is that nucleation is strongly suppressed after an initial nucleation period. The use of cooling periods in the course of annealing leads to enhanced nucleation and reveals that the formation of Si depleted regions around the growing grains prevents further nucleation. The growth mechanism is discussed starting from the phase diagram of the Al/Si system. It turns out that the critical parameter is the actual concentration of Si in Al and the value of supersaturation.