Incident ion dose evolution of damaged layer thickness in Si substrate exposed to Ar and He plasmas

Abstract

The effect of ion flux on the formation of a damaged layer in a Si substrate was investigated in detail. An inductively coupled plasma source was used to control the flux (Γion) and energy (Eion) of incident ions. The progressive behavior of the total damaged layer thickness (ddam) estimated by spectroscopic ellipsometry primarily depends on the total ion dose (Dion = Γion × tpr, where tpr is the process time) and Eion. The evolution of ddam then saturates and becomes independent of Dion. The characteristic total ion dose (Ddam) is defined, which distinguishes the progressive and saturation phases. Experimental results suggest that Ddam is estimated to be in the range from 1 × 1016 to 3 × 1016 cm−2, regardless of Ar and He plasmas in the present study. This Dion-dependent behavior was also confirmed by transmission electron microscopy and capacitance–voltage measurements. The interface thickness dIL of the damaged layer was found to be independent of Dion. This result confirms that dIL can be used as a measure of the Eion-dependent plasma-induced damage (PID) for in-line monitoring. The present Dion dependence can be implemented in the conventional PID range theory, particularly, in the designs of high-density plasma sources.