AVS 52nd International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS-ThM

Paper PS-ThM11
A Numerical Model for Profile Anomalies Caused by Surface Charging during Etching and Overetching of Polysilicon

Thursday, November 3, 2005, 11:40 am, Room 304

Session: Plasma-Surface Interactions II
Presenter: Y. Osano, Kyoto University, Japan
Authors: Y. Osano, Kyoto University, Japan
K. Ono, Kyoto University, Japan
Correspondent: Click to Email
The precise control of etched profiles in gate etch processes is one of the most important issues. However, the mechanism of etching processes is not fully understood; in particular, the particle transport and reaction processes in microstructures are considerably difficult to be understood, owing to a number of physical and chemical effects. Among these effects, the surface charging on insulating masks during etching causes the deflection of ion and electron trajectories in microstructures. Moreover, the charging on electrically floating poly-Si on SiO@sub 2@ films during overetching step causes a significant deflection of ion trajectories in microstructures. It is generally appreciated that the deflection of ion trajectories leads to the nonuniformity of ion fluxes onto the feature surfaces, which in turn results in profile anomalies such as bowing, microtrenching, and notching. In this paper, we present a phenomenological, pseudo atomic scale model to simulate the feature profile evolution of Si etching in Cl@sub 2@. The model incorporates the surface charging in microstructures, to investigate its influence on the profile evolution. The particle transport of Cl@super +@ ions, Cl neutrals, and electrons in microstructures onto etched substrates is analyzed by the Monte Carlo calculation. The model gives the electrostatic potential distribution, along with the differential charging that occurs on insulating masks, electrically floating Si, and SiO@sub 2@ films. The flux of ions and electrons onto feature surfaces is self-consistently analyzed by taking into account their deflection due to Coulomb interaction with charged feature surfaces. The feature profile evolution is presented by the cell removal method. The numerical simulation is performed with different incident ion energies and pattern widths. Emphasis is placed on the mechanism for the formation of microtrenching and notching, which are generally considered to be mainly caused by the surface charging.