Comparison of two-dimensional and three-dimensional models for profile simulation of poly-Si etching of finite length trenches

The development of two-dimensional (2D) profile simulators for fabrication of microelectronics features has significantly progressed during the past few years and now enables modeling of etch profile evolution for many different plasma processing conditions. Increasingly complex devices which have three-dimensional (3D) (that is, asymmetric) structures are now being designed. These structures require improved dimensionality in profile simulators to capture their most important features. Under many conditions, such as circular via etching, two-dimensional profile simulators can be used to address 3D structures. A legitimate issue is to what degree these 2D approaches can indeed be applied to truly 3D structures. In this article, we present results from a 3D profile simulator for the purpose of comparing profiles for innately 3D features to results obtained from a 2D profile simulation. It has been found that profiles obtained from the 3D simulators exhibit greater sidewall sloping in three-plane corners than predicted by the 2D simulator. The implication to process design is that a greater degree of overetching will be required to clear these corners than predicted by the 2D simulators. Asymmetries as well as the angular spread of the ion flux distribution are examined to determine their role in 3D profile evolution.