Calculation and Measurement of Ion and Electron Shading Parameters and Comparison of Shading Effects with Computer Simulation

摘要

Electron shading is recognized as a major mechanism for plasma process induced damage in commercial plasma etch chambers. As the semiconductor industry moves to smaller feature sizes and thinner gate oxides, shading induced damage becomes a greater concern. The shading effect is known to be more severe with higher aspect ratio features and high density plasmas. Recently, V. Vahedi, et al, derived an analytic model capturing the main parameters involved in electron shading. Two of these parameters, the ion and electron shading ratios k_I and k_e, have not been measured to date, but are crucial to the model. This study uses patterned and unpatterned SPORT wafers to measure and derive these shading parameters. In addition PIC with estimated shading coefficients were compared with SPORT measurements. The simulation is able to account for charged resist structures that cause electron shading.