Determination of titanium temperature and density in a magnetron vapor sputtering device assisted by two microwave coaxial excitation systems

We present an optical absorption diagnostic technique devoted to the simultaneous determination of titanium density and temperature during sputtering of Ti. These measurements were performed in a type of ionized physical vapor deposition reactor, consisting of a magnetron sputtering device assisted by two microwave systems for the ionization of the sputtered vapor of the magnetron. Our goal is to optimize the ionization in this reactor in order to improve the deposition process (film quality, recovery of the layers, etc.) compared to standard magnetron sputtering systems. In order to determine both titanium neutral and ion densities, we have used a titanium hollow cathode vapor lamp powered with pulsed power supply. Measurements were carried out at different positions in the reactor at different pressures (1–15 Pa). We have studied the effect of magnetron current from 100 mA to 2 A and of microwave power from 100 W to 1 kW. At lower pressures, we have shown that the titanium is not thermalized close to the magnetron, whereas it is thermalized at 10 Pa at all positions. The neutral titanium density is typically between $1010$ and $3×1011 cm−3,$ and the ion density is $∼109 cm−3.$ The effect of microwave power is the decrease of neutral titanium density and the increase of its temperature. At a position located 1 cm after the crossing of the microwave plasma area, we showed that the illumination of the microwave plasma increases the degree of ionization of Ti from 2% to 10%.