FLOW VISUALIZATION STUDIES FOR OPTIMIZATION OF THE GROWTH OF TIN BY PACVD

Gas flow visualization studies were performed in a vertical plasma-assisted chemical vapour depostion (PACVD) reactor. The flow patterns were made visible by illuminating TiO2 particles generated by the reaction of TiCl4 and H2O in the gas flow. The gas was injected through four different distribution systems. The deposition of TiN by a PACVD process was performed in a pulsed d.c. glow discharge at a total pressure of 250 Pa and a substrate temperature of 500 degrees C. Flow visualization experiments and depositions were carried out under similar flow conditions, in particular the same Reynolds number. The streamline patterns were used to interpret the deposition rate and chemical composition across the surface of the deposited TiN layer. The thickness and uniformity of the deposited films were determined. It can be demonstrated that well designed gas distribution systems enable uniform deposition of coatings on cutting tools with complex geometry.