A THERMOCHEMICAL MODEL FOR THE PLASMA-ETCHING OF ALUMINUM IN BCL3/CL2 AND BBR3/BR2

This article describes a quantitative Recipe Map which has been constructed to target the controllable gas flows, wafer loading, and temperature settings predicted to result in the optimum BCl3/Cl2 and BBr3/Br2 plasma etching of aluminum for a given reactor and background oxygen pressure. The numerical predictions of this Recipe Map are based on modeling the plasma as a steady state flow system in which all thermodynamically predicted chemical reactions occur with collision limited kinetics, and where, in addition, physical sputtering removes material from the ion-bombarded surfaces. Anisotropic etching is caused by the sputtering of deposited oxide which allows the chemical etching of the underlying Aluminum. Although this model is very simple, its numerical predictions are in good qualitative agreement with the observed Al etching dependence on the processing parameters in both single wafer and hex etchers. In particular, the effect of wafer loading can be quantitatively evaluated using simple formulas.