Scanning Force Microscopy on Laser Ablated Silicon Nitride Films

Abstract

Silicon nitride insulators are gaining increased interest and are being widely used for passivation, annealing masks and as a dielectric in metal—nitride--oxidesemiconductor (MNOS) structures for non-volatile memories. Silicon nitride films can be prepared by reactive plasma deposition (RPD), plasma-enhanced chemical vapour deposition (PECVD) or by low pressure chemical vapour deposition (LPCVD). Recently, new laser-based methods have been developed, such as: pulsed laser deposition (PLD), laser chemical vapour deposition (LCVD) and laser direct synthesis (LDS). For the present study, silicon nitride films were deposited by the laser reactive ablation (LRA) method. The laser reactive ablation method is derived from the pulsed laser deposition technique. PLD is used to deposit stoichiometric thin films of alloys or compounds by ablating already-prepared solid targets. Unlike PLD, in LRA, ablation occurs in a reactive gas atmosphere [1]. Thus, a solid target consisting of the material to be reacted is ablated in a reactive gas atmosphere. The resulting material is collected on a substrate placed at a given distance from the target [2]. Laser reactive ablation (LRA) is a new method, which combines (in one step) the synthesis of the compound and the deposition. The LRA method is