Heat Transfer Analysis in ICP-Assisted Bipolar Pulsed DC Magnetron Sputtering

An AI-doped ZnO thin film is deposited by using a bipolar pulsed de magnetron sputtering method. An internal inductively coupled plasma (ICP) was used as a secondary plasma source and could produce a better quality thin film due to the high ionization and the low-energy ion bombardment. Polymer substrates for display products and solar cells require a low deposition temperature, a high deposition rate and high quality. High-density plasmas, such as an ICP, can heat a polymer substrate by ion bombardment, a flux of electron energy and heat released by recombination of ions at the substrate's surface. We developed a numerical model for heat transfer from the plasma and confirmed it by direct measurements with thermocouples. The sputtering Ar plasma raised the substrate temperature by 132 $^{\circ}C$ within 10 min for a pulsed de power of 200 W at 50 kHz. Major sources of heating were ion recombination and kinetic impact. When the ion recombination coefficient of 0.1 was used, the modeling result, 137 $^{\circ}C$, was in good agreement with the measured value, a temperature rise of 140 $^{\circ}C$ for an ICP power of 200 W at 2 MHz.