ULTRA-THIN GATE OXIDE-GROWTH ON HYDROGEN-TERMINATED SILICON SURFACES

The atomic-scale surface morphology of hydrogen-terminated Si(100) surfaces obtained by the treatment in dilute HF, BHF or HF+H2O2 has been studied by Fr-IR-ATR and AFM. It is found that the ATR spectrum of an 0.1%HF+1%H2O2 treated surface exhibits a sharp SiH2 vibrational peak being characteristic of a relatively flat (100) surface, while a dilute HF-treated surface shows twin peaks consisting of a main SiH2 peak and a rather strong SiH3 peak. The AFM images for the two types of surfaces are almost identical because the horizontal resolution of AFM is in the nanometer rage. The built-in strain in the ultra-thin oxide measured by ATR has revealed that the Si-O-Si bonds are progressively strained as the oxide thickness increases up to about 3 nm and that the oxide layer is structurally homogeneous in the thickness range 1 to 3 nm. Current transport through ultra-thin gate oxide grown on 4.5%HF-treated Si(100) surfaces has been systematically investigated. It is shown that the direct tunneling current controls the transport through oxide thinner than 4.1 nm while Fowler Nordheim tunneling predominates the current for oxide thicker than 5.1 nm. The observed tunneling current quantitatively coincides well with the calculated one, indicating that nearly ideal tunneling transport is realized in MOS structures.