OPTICAL CHARACTERIZATION BY SPECTROSCOPIC ELLIPSOMETRY OF POLYCRYSTALLINE SI1-XGEX OF VARIABLE GE COMPOSITION UP TO 100-PERCENT GE

Polycrystalline Si1-xGex, has been recently shown as a favorable alter native to the poly-Si gate electrode for CMOS technology: the optical properties of this new material poly-Si1-xGex alloys layers are invest igated here. Spectroscopic ellipsometry (SE) analysis on samples with different Ge contents up to 100%,, demonstrates both the composition d ependency and the morphological change in the amorphous character of t he 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-mi cron(< 0.18 mu m) gate slacks material optimization. Layer morphology observation using XTEM and AFM are correlated here with SE, which in t urn, would certainly be, in the near future, a routine control tool du ring the fabrication of the poly-SiGe gate structure. (C) 1998 Elsevie r Science S.A.