Optical characterization by spectroscopic ellipsometry of polycrystalline Si 1− xGe x of variable Ge composition up to 100% Ge

Abstract

Polycrystalline Si 1− x Ge x , has been recently shown as a favorable alternative to the poly-Si gate electrode for CMOS technology: the optical properties of this new material poly-Si 1− x Ge x alloys layers are investigated here. Spectroscopic ellipsometry (SE) analysis on samples with different Ge contents up to 100%, demonstrates both the composition dependency and the morphological change in the amorphous character of the material, while the x parameter increases. The technique is thus an easy and non-destructive method for layer composition as well as for material morphology control. These are important parameters for sub-micron (<0.18 μm) gate stacks material optimization. Layer morphology observation using XTEM and AFM are correlated here with SE, which in turn, would certainly be, in the near future, a routine control tool during the fabrication of the poly-SiGe gate structure.