In situ calorimetric temperature measurements of Cu, Cr, Ti targets during DC magnetron sputtering

Direct measurements of the temperature of Cu, Ti, and Cr targets (3 mm thick, Ø 55 mm) using thermocouples attached to the front (erosion zone) and back sides of the targets during magnetron sputtering (DC) were performed. The variables are the target mode (cooled or uncooled target), working gas (Ar, N₂), and discharge power density (q_in). It was shown that the target temperature reaches ∼730 K on the front and ∼530 K on the back sides of the cooled target, while for an uncooled one, it is ∼1050 and 950 K, respectively (Cu target). For both modes and all targets, the target temperature is slightly higher when sputtering in N₂. Calculations of the surface temperature based on measurements of the target temperature and its emissivity showed that for all targets, their surface temperature is significantly higher compared to the bulk of the target. Based on the temperature measurements on opposite sides of the Cu target, its dynamic thermal conductivity is calculated. It turned out that it is ∼100 times lower than the thermal conductivity of normal Cu. The above results are discussed based on a physical model that assumes the appearance and existence during sputtering on the target surface of a layer whose properties strongly differ from those of ordinary metals.