Effect of sputtering power on surface topography of dc magnetron sputtered Ti thin films observed by AFM

Titanium films were deposited on glass substrates at room temperature by direct current (dc) magnetron sputtering at fixed Ar pressure of 1.7 Pa and sputtering time of 4 min with different sputtering power ranging from 100 to 300 W. Atomic force microscopy (AFM) was used to study topographic characteristics of the films, including crystalline feature, grain size, clustering and roughening. The amorphous-like microstructure feature has been observed at 100-150 W and the transition of crystal microstructure from amorphous-like to crystalline state occurs at 200 W. The increase in grain size of Ti films with the sputtering power (from 200 to 300 W) has been confirmed by AFM characterization. In addition, higher sputtering power (300 W) leads to the transformation of crystal texture from globular-like to hexagonal type. The study has shown that higher sputtering power results in the non-linear increase in deposition rate of Ti films. Good correlativity between the surface roughness parameters including root mean square (RMS) roughness, surface mean height (Ra) and maximum peak to valley height (P-V) for evaluating the lateral feature of the films has been manifested. Surface roughness has an increasing trend at 100-250 W, and then drops up to 300 W.