Mechanical Properties of Sputtered Ti Thin Films : A TEM Observation of Microstructures of Ti Thin Films

The effect of sputtering gas (Ar gas) pressure on the growth and the structure of Ti thin film membranes of 0.3-0.4μm thickness, microfabricated by magnetron sputtering, has been studied by transmission electron microscopy. In the present investigation, sputtering gas pressure was varied from 0.2 Pa to 2.0 Pa. The as-deposited Ti films showed very fine structures. The Ti films deposited at 0.2-1.1 Pa had hcp structures with preferred orientation. On the other hand, the Ti films deposited at 2.0 Pa appear to be a mixture of a random hcp structure and a cubic structure. The Ti films deposited at lower Ar gas pressures had dense structures with smooth flat surfaces, however, the rough surfaces of Ti films were promoted by elevated Ar gas pressures. Shadowing played a very important role in the coating growth of the Ti films. The lower tensile strength values of Ti films deposited at higher Ar gas pressures can be explained in terms of shadowing.