Effect of carbon contamination enhanced by micro-roughness on gate oxide integrity

We evaluated the effect on gate oxide integrity of increased carbon contamination due to the microroughness of the Si surface. Carbon contaminants introduced into the sacrificial oxide film during ion implantation are removed during the pre-gate oxidation cleaning, but redeposit on the surface. A rough surface has many physically and chemically active sites, so more carbon adsorbs on a rougher surface. The adsorbed carbon forms Si-C bonds during the preheating step under N/sub 2/ ambient before the thermal oxidation process and degrades the integrity of the gate oxide.