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 hydr ogenated 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 concent rations and hydrogen bonding configurations, were simultaneously annea led. Only a particular set of deposition conditions led to crystallisa tion. The a-Si:H thin film which was successfully crystallised was pre pared in an argon-hydrogen mixture, in which the last few minutes of f ilm 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 pr edominantly 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-temperatur e between each annealing step. This resulted in large grained (>10 mu m range) polycrystalline silicon after the 600 degrees C annealing ste p for a 1.1 mu m thick sample. Fourier transform infrared (FTIR) spect roscopy, elastic recoil detection analysis (ERDA) and scanning electro n microscopy (SEM) techniques were used to analyse samples before and after crystallisation. (C) 1997 Elsevier Science S.A.