Reliability Improvement of Diamond Film Cutting Tools by Two-step CVD Growth Technique

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In order to improve the reliability of diamond cutting tool, we have investigated two targets; to develop the cylindrical cavity type microwave (MW) plasma CVD system with high efficiency of production, and/or to establish the simple procedure of enhancement on the nucleation density compared with two-step growth technique.The novel MW plasma CVD system was developed using the cylindrical cavity with H11 mode. The conversion efficiency of MW power into plasma drastically increased by improving the mode converter and the MW guide.Using the developed system, the diamond films were successfully deposited. Either by increasing MW power or by adding Ar gas, the plasma volume was expanded, resulting in the enlargement of deposition area. The uniformity of substrate temperature was performed using the divided-concentric circle heater. In this study, the maximum difference of substrate temperature was reduced up to 50 degree. Using these techniques, the diamond film was successfully deposited … More in the area of φ90 with relatively uniform thickness.Since two-step growth technique, in which the adhesion strength, i.e., the reliability can be enhanced, has the complicated process, the production efficiency was much lower at the industrial level. Therefore, the pulse injection procedure was developed instead of the high supersaturation step in two step growth technique. Using the pulse injection procedure, we could achieve the enhancement of nucleation density as well as in the two-step growth technique. The pulse injection procedure had the advantage to skip the processes of the second plasma generation and the cleaning after deposition, resulting in the decrease of production cost.Moreover, the scale of developed system was dependent on the using MW wavelength. Although the using frequency was 2.45GHz in this study, 900MHz can be available in the industrial production system. Using 900MHz, the deposition area might be three times larger than this study, keeping the basic advantages. Less