Pulsed Laser Annealing of Semiconductor Structures for Functional Devices

Abstract

We review our progress on the laser processing of semiconductor microstructures and nanostructures for functional devices. Fundamental research conducted to understand the melt-mediated phase transformations induced by nanosecond laser irradiation in thin semiconductor films is presented. A detailed experimental study analyzed the physical mechanisms of the explosive crystallization in amorphous germanium that produces large area self-sustained crystal growth. The double laser crystallization method that combines a nanosecond laser pulse and a modulated microsecond laser beam was shown to produce ultra-large grain polycrystalline silicon, enabling fabrication of thin film transistor devices of high performance from amorphous silicon films. The crystal growth process was imaged by temporally resolved photography. Non-melt Excimer Laser annealing of thin silicon-oninsulator films for dopant activation was demonstrated. Applying multiple laser pulses below the melting threshold effected solid phase annealing of the single crystalline silicon films. Semiconductor nanowires are one-dimensional nanostructures that have displayed the potential to be used with low-cost flexible plastic substrates for applications such as large-area displays and sensor arrays. The excimer laser annealing of silicon nanowires is demonstrated as an alternative to conventional thermal annealing for dopant activation. The optical absorption of the nanowires is discussed and the effect of parameters such as fluence and number of pulses is investigated. The interaction of laser pulses with silicon nanowires is investigated through numerical simulations. Schematic depiction of pulsed laser annealing of generic semiconductor structures. Specific structures are shown in bottom inset circles.