Analysis of Si substrate damage induced by inductively coupled plasma reactor with various superposed bias frequencies

Plasma-exposed Si surface related to Si recess in source/drain region was investigated in detail for various superposed bias configurations with frequencies of 13.56 MHz and 400 kHz. Two different bias powers were utilized by an inductively coupled plasma reactor (ICP). The surface layer (SL) and the interfacial layer between the SL and Si substrate (IL) were analyzed by spectroscopic ellipsometry (SE), photoreflectance spectroscopy (PR) and capacitance-voltage (C-V) measurement. The SE identified the interfacial layer growth by an optimized optical model, and the PR, the structural strain change and carrier trap site generation in IL, in accordance with a bias power and a superposed bias configuration. The aerial trap site density was estimated on the basis of a PR-based model. Also C-V measurement confirmed the surface and interfacial layer growth and carrier trap site generation in the vicinity of plasma-exposed surface. The obtained findings imply that superposed bias configurations, widely believed inevitable for future plasma processing, should be optimized in terms of Si substrate damage quantitatively estimated by the methods presented in this article.