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

Gas flow visualization studies were performed in a vertical plasma-ass isted chemical vapour depostion (PACVD) reactor. The flow patterns wer e made visible by illuminating TiO2 particles generated by the reactio n of TiCl4 and H2O in the gas flow. The gas was injected through four different distribution systems. The deposition of TiN by a PACVD proce ss was performed in a pulsed d.c. glow discharge at a total pressure o f 250 Pa and a substrate temperature of 500 degrees C. Flow visualizat ion experiments and depositions were carried out under similar flow co nditions, in particular the same Reynolds number. The streamline patte rns were used to interpret the deposition rate and chemical compositio n across the surface of the deposited TiN layer. The thickness and uni formity 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.