Control of SC1 Wet Cleaning Process for Nano-Scale Gate Oxide Integrity

The effect of H2O:H2O2:NH4OH (SC1) pre-gate cleaning on the oxide thickness and Si etching were investigated. If the oxide thickness is more than 11 Å, etching of SiO2 is dominant, while the oxidation rate on Si surface is faster than the etch rate of Si, if the oxide thickness is less than 11 Å. The thickness of thin gate oxide is affected by SC1 cleaning and the photoresist removal method in a dual-gate-oxide integrity process. The etch rate of a hydrophobic silicon surface was five times faster than that of a hydrophilic surface in a 50°C 5:1:1 SC1 solution. If the surface was converted into hydrophilic, the etch rate of silicon dropped to 1.0 Å/min, and remained constant with the process time. The etch rate of silicon reflecting the etch rate of chemical oxide is higher than that of the thermal oxide, but lower than that of the plasma enhanced chemical vapor deposition (PECVD) tetra ethyl ortho silicate (TEOS) film.