An electron cyclotron resonance (ECR) plasma system was used to plasma oxidation. The plasma oxidation was studied into three catagories.
First, thin oxide films (4-12 nm) were grown on single-crystal silicon substrates at temperatures from 25 to 205℃ in a low pressure ECR oxygen plasma. The oxidation rate was studied as a function of oxidation time, substrate temperature, microwave power, and pressure. Oxidation rate increases with substrate temperature but decreases with pressure. The oxide thickness was not changed with microwave power. It is found that the plasma oxidation kinetics can be explained by the Cabrera-Mott model, in which the drift motion of ions is assumed, rather than by the Deal-Grove thermal oxidation model. These oxide films were found to have oxygen to silicon ratio 2 using auger electron spectroscopy (AES). From the ellipsometry measurements, these films shows a refractive index was around 1.46. High-frequency capacitance-voltage (C-V) and current-voltage (I-V) studies performed on 4.2 and 10.2 nm gate thickness capacitors. In case of 10.2 nm plasma oxide film, leakage current density at $1MVcm^{-1}$ was less than $1.0×10^{-8}Acm^{-2}$ and breakdown field (applied electric field at $10^{-6}A/㎠$) was more than $10MVcm^{-1}$. Also this film had the negative flat band voltage and effective dielectric constant was 3.85. These results indicate that high quality oxide films with properties that are similar to that of thermal oxide can be grown at low temperature.
Second, the interface layer ($SiO_2$) formed on a Si wafer during $Ta_2O_5$ deposition using ECR-PECVD is investigated. An $SiO_2$ layer is formed due to oxygen plasma and initial stage of $Ta_2O_5$ deposition. TEM observation shows that $SiO_2$ thickness increases with substrate temperature.
Third, the plasma oxidation is attempted tantalum oxide film as a postannealing. Because the plasma oxidation has a strong oxidation power, it can be supply oxygens to tantalum oxide film effectively. After the plasma oxidation as a postannealing, the electric properties of tantalum oxide film was improved. These results indicate that the plasma oxidation at low temperature can be used as a postannealing.
