Collapse Mechanisms for High Aspect Ratio Structures with Application to Clean Processing

The fabrication of semiconductor devices includes the generation of high aspect ratio structures which are prone to lateral mechanical forces. Therefore, the mechanical stability of polysilicon line structures has been tested by an AFM technique for several line widths. Additionally, the damage has been evaluated and shows a uniform size distribution. These experimental results have been compared to numerical models, in which the influence of specific geometries and material present in the stack has been studied. A stress concentration region at the bottom of the line was observed and could be removed by corner rounding (fillet). Besides, the maximum stress is shifted away from the substrate. The experimental damage showed a stump at the bottom of the damage, thus confirming the numerical results.