Photoreflectance spectroscopic technique: a new model for estimation of plasma-induced defect density in Si substrate

In recent years, reactive ion etching (RIE) has been widely used in ULSI process technology. However, the Si surface exposure to plasmas during RIE causes the generation of defects or damage in the Si substrate due to the energetic ion bombardment and etching species penetration. This plasma-induced damage strongly affects ULSI device performance and reliability. Si substrate damage induced by CHF₃ -CF₄-Ar plasma processing has been characterized by photoreflectance (PR) spectroscopy. Moreover, the damage induced by Ar plasma has been characterized in-situ in the processing chamber. Both of the PR signal intensities decrease with the plasma treatment. The decrease in PR signal intensity is attributed to the decrease in modulation due to the introduction of the charged defects that changes the space charge density of the depletion layer. We propose a new model for the estimation of the defect density induced by plasma exposure. Using this model based on PR spectroscopy, the defect density can be quantitatively calculated