Study On Preparation And Characterization Of Silicon Carbonitride Films

SiCN thin films is a new ternary elements films, it has many good properties, such as high hardness, wide optical band gap, anti-oxidation at high temperature and anti-erosion, and so on. It has wide applications to micro-electron semiconductor and computer industry. In this paper, we study the bonds structure and properties of the SiCN thin films affected by different sputtering conditions.The SiCN thin films are prepared by twined charge chamber microwave ECR plasma enhanced unbalanced magnetron sputtering system. The high pure argon (99.99%) was used as sputtered gas, high pure nitrogen (99.99%) was used as both sputtered and reacted gas, high pure silicon (99.99%) and graphite (99.99%) were used as sputtering targets materials. The SiCN films grew on the silicon (100) were obtained through changing the experiment conditions, such as silicon target sputtering power and the flow ratio of nitrogen. The structure and properties of SiCN films were measured by FT-IR, XPS, Nanoindenter and ellipsometers.Result showed that the processing parameters were very important effects on the films chemical structure, mechanical and optical properties. The silicon and oxygen content in the films was controlled by changing the silicon target sputtering power. At the lowest Si target sputtering power of 100 W, the content of the O impurity in the films was as large as 10.63%, and the O impurity mainly comes from the chemical adsorption in the open air due to the loosen structure of the films. The O content decreased with increasing Si target sputtering power. At higher Si target sputtering powers than 250W, the content of O impurity in the films was less than 4%, and the main component was C-O bond. In this condition, dense films could be obtained. The maximum hardness of the films was 29.4 GPa, and the refractive index of the films could reach to 2.43. While, the silicon content in the films reduced with the increasing of N₂ flow ratio, even with a high Si target sputtering power. That is because the target poisoning phenomenon on Si target, which was caused by high N₂ flow ratio. As a result, O content in the films decreased with the increasing of N₂ flow ratio. At the Si target sputtering power of 100 W, and N₂ flow ratio of 9 sccm, because of the loosen structure, the content of the O impurity in the films was as large as 14.6%. In this condition, the content of C-N bond in the films is 24%, more than that in the films deposited with only increasing Si target sputtering power. But most of the C-N structure was sp ²C=N and sp ¹C=N bonds. As a result, hardness of films deposited with higher N₂ flow ratio was reduced, the maximum hardness of the films was just 17.5Gpa. But in this condition, the refractive index of the films was lower than 2.0. That means increasing N₂ flow ratio could be good for depositing low dielectric constant SiCN thin films.