Vacuum Ultraviolet Spectrometric Ellipsometry Application to Optical Metrology of High-κ Dielectrics and Metal Gate Materials

Abstract

Nowadays an accurate measurement of the high-k dielectrics (HK) and metal gate (MG) material thickness and properties is becoming more and more important for beyond 40nm technology. Traditional optical broad band spectrometric ellipsometry (BBSE) (wavelength range 240~800 nm) thickness metrology is suffering from poor accuracy among initial layer (IL), HK layer and MG layers in multi-layer stacks and poor repeatability. By extending wavelength down to 150nm, KLA-Tencor Aleris 8500 Vacuum Ultraviolet SE (VUVSE) greatly improves measurement performance, and enables deduction of film energy bandgap and defect information from offline spectra analysis. In this work, the measurement performance on HKMG stacks with BBSE and advanced VUVSE were compared systematically. The better performance of VUVSE in metrology accuracy and repeatability was displayed. The results of measurement can be highly correlated with film production process conditions, including both in multi-layer stack thickness measurement and in HK material band gap and defects study.