Pulse-extended excimer laser annealing of lead zirconate titanate thin films

Excimer laser annealing is a promising method for the crystallisation of ferroelectric layers, such as PZT, in low thermal budget integrated device fabrication processes. A technique is described whereby the problem of very high surface temperatures in PZT is overcome by the use of temporal pulse extension, where the effective laser pulse length is increased from 24ns to 374ns. Modelled temperature profiles through a PZT thin film structure during laser irradiation illustrate the benefit of pulse extension due to enhanced heat propagation into the PZT. The modelling also shows that underlying silicon is not heated significantly even with pulse extension. Initial results show that PZT can be crystallised into the perovskite phase from the top downwards with minimal surface damage.