Flow and Heat Transfer Analysis of Cooling Water in a Rotating Magnetron Cathode

회전형 마그네트론 음극의 냉각수 유동 및 열전달 해석

Abstract

We have developed a numerical model to analyze flow dynamics and heat transfer characteristics of the cooling water in a circular rotating magnetron cathode by a moving boundary grid method realized in a commercial multiphysics package, CFD-ACE+. The numerical model is composed of a target, dual mass rotating cathode and cooling water connections. When the inlet and outlet of the cooling water are offset by the same distance from the rotation axis, the temperature at the center is higher by $50^{\circ}C$ at maximum. At 5 mm away from the target surface, the temperature profile showed typical center high characteristic. At heat input of 30 kW, the maximum temperature change of the cooling water hits $6^{\circ}C$ within 0.5 sec under 60 rpm. With a cooling water configuration of center in/edge out, the temperature of the center region of the target gets lowered. Within 100 seconds of plasma operation time, the cooling water temperature keeps getting higher.

Fig. 2. Commercial magnetron modules with a difference cooling water connection (a) central inlet (b) peripheral inlet.

Fig. 1. A numerical model of a rotating magnetron cathode.

Fig. 3. Schematic diagram of a commercial magnetron sputtering system with a heart type magnet array and electro magnets.

Fig. 4. Relative motion of magnet and balancing module to cooling water connection

Fig. 5. Simulated cooling water traces from (a) inlet (b) outlet at right angle position

Fig. 6. Simulated cooling water traces from (a) inlet (b) outlet at in-line position

Fig. 7. Calculated torque variation with rotation angle

Fig. 8. Heat flux with moving boundary condition

Fig. 10. Cooling water flow and heat transfer analysis results (a) steady state temperature profile (b) flow pattern of a cooling water (c) traces of cooling water from connection line.

Fig. 11. Simulated results at 30 kW input power and 60 rpm with cooling water flow rate 36.6 liter/min. (a) water flow velocity, (b) temperature.

Fig. 12. Used multi-track magnet array module showing heat affected surfaces of magnets and fixing guide.

Fig. 13. Water drop type magnetron and discharge affected target surface profile.

Fig. 14. Heat flux and temperature distribution of the two rotating modules (30 kW, 60 rpm, cooling water 1kgf/cm² and 5 m/s.

Fig. 9. (a) Calculated transient temperature profile at 2.57 sec after ignition of plasma (b) temperature graph along radial cut line.