Study of dislocations and stress in silicon-on-insulator tubs using transmission electron microscopy and finite element modelling

The stress resulting from the fabrication of trenched and refilled SOI tubs was modelled using Finite Elements to attempt to predict the resultant slipped structure. High resolution TEM has been used to investigate this slip and the dislocations introduced into the structure during fabrication. The stress is found to be significantly greater at the corners of the trench than the bulk silicon in the tub prior to filling with TEOS and polysilicon. In the completed structure the corners of the tubs remain at higher stress than the bulk of the tub. Tubs showing surface slip were examined using TEM and clear evidence of dislocations originating from the tub corners could occasionally be seen. However on the whole it was found that few dislocations remained in the tub following processing and a step on the surface indicated that those produced had propagated out to the surface.