Thin Solid Films, Vol.310, No.1-2, 67-74, 1997
Large-grain polycrystalline silicon thin films obtained by low-temperature stepwise annealing of hydrogenated amorphous silicon
Large grained polycrystalline silicon thin films have been prepared by low-temperature solid phase crystallisation of sputter-deposited hydrogenated amorphous silicon (a-Si:H), with relatively short processing times, and a considerably low thermal budget. Various a-Si:H samples, deposited under different conditions and with varying hydrogen concentrations and hydrogen bonding configurations, were simultaneously annealed. Only a particular set of deposition conditions led to crystallisation. The a-Si:H thin film which was successfully crystallised was prepared in an argon-hydrogen mixture, in which the last few minutes of film deposition occurred in a hydrogen-rich atmosphere. For that film, the hydrogen concentration profile resulted in a much higher hydrogen content on the sample surface than in the bulk, and H-Si bonds were predominantly of the weak type. Crystallisation was accomplished by low-temperature stepwise annealing from 200 degrees C to 600 degrees C at 100 degrees C steps, with samples being cooled down to room-temperature between each annealing step. This resulted in large grained (>10 mu m range) polycrystalline silicon after the 600 degrees C annealing step for a 1.1 mu m thick sample. Fourier transform infrared (FTIR) spectroscopy, elastic recoil detection analysis (ERDA) and scanning electron microscopy (SEM) techniques were used to analyse samples before and after crystallisation.
Keywords:CHEMICAL-VAPOR-DEPOSITION;H CLUSTER FORMATION;A-SI-H;BONDING CONFIGURATIONS;SUBSTRATE-TEMPERATURE;CRYSTALLIZATION;RECRYSTALLIZATION;IMPLANTATION;NUCLEATION