Local strain measurements in shallow trench insulator structures using near-ultraviolet Raman spectroscopy: Simulation and experiment
Résumé
Shallow trench insulator (STI) stress induced in active lines has been investigated both by near-ultraviolet (UV) Raman spectroscopy and mechanical modelization. Two different STI processes have been compared. The influence of the linewidth is also studied. After adjusting some instrumental and material parameters, all components of the stress tensors have been determined accurately. The polarization of the incoming light is discussed, showing that the selection rules are no longer respected at the edges of the STIs. Some of the limitations in spatial resolution of the Raman spectroscopy have been overcome, making use of the mechanical model and taking benefit from the higher spatial resolution of the UV excitation. In turn, the mechanical model has been refined from comparisons with experiments. It is therefore suggested that coupling these techniques may provide a relevant method to measure stress in the silicon for the integrated circuit industry. From a practical viewpoint, it is demonstrated that the use of the subatmospheric chemical vapor deposition process allows significant reduction of the compressive stress in the center of the active lines.