Argon entrapment and evolution in sputtered TaSi₂ films

The use of tantalum disilicide over doped polycrystalline silicon (poly-Si) for gate and interconnect metallization is becoming an integral part of the design and processing of VLSI devices. Under certain sputtering and/or processing conditions, the silicide surface has been seen to exhibit sporadically blisters and voids during high temperature processing. In this study, we shall demonstrate that the occurrence of these defects in TaSi₂ is related to the entrapment of argon during deposition and the evolution of that gas during subsequent processing. This conclusion will be deduced by ascertaining, through a series of controlled experiments, the contributory effect of a wide range of processing parameters, by proposing a phenomenological model to explain the governing mechanism of blister and void formation, and by providing analytical evidence to verify this model.