On surface temperatures during high power pulsed magnetron sputtering using a hot target

Abstract

A study of temperature of a magnetron target was performed for the case of high power pulsed magnetron sputtering (HPPMS) of titanium thin films, using a water-cooled target and a hot target. Temporal evolution and spatial distribution of surface temperature were investigated. Temperature measurements were made by an infrared camera for target diameter of 100 mm, pulse repetition frequencies of 1 and 10 kHz, and discharge average pulse currents of from 2.5 to 35 A. For the case of hot target, surface temperature of the erosion zone increased up to 1750 °C and melting occurred. Temporal evolution of temperature after the end of deposition revealed phase change in solid-state from β-Ti to α-Ti at 882 °C and, for the case of high average pulse currents, also solidification at 1670 °C. The solid state phase transformation plateau was used to determine an emissivity of Ti target for the present case, and therefore precisely calibrate infrared camera measurements. The target melting was analysed in detail. The dependencies of maximum temperature on average pulse current and on average target power density for the case of hot target revealed the existence of heat losses other than radiation (i.e. enhanced sputtering, sublimation, electron emission and evaporation) at temperatures above 1500 °C, which correlates with higher erosion and deposition rates shown in another work.