CHARACTERIZATION OF TIN THIN-FILMS USING THE BULGE TEST AND THE NANOINDENTATION TECHNIQUE

In-plane mechanical properties of titanium nitride (TiNx) thin films h ave been investigated by performing bulge test experiments on square m embranes of side of approximately 2a = 4 mm. A layer of about 1 mu m t hickness of TiNx (x = 0.84 - 1.3) was deposited onto an n-type Si(100) wafer using radio frequency magnetron sputtering. Prior to TiNx depos ition, free-standing low-stress LPCVD silicon nitride (SiNx) thin film s were fabricated by means of standard micromachining techniques. The edges of windows were aligned with the [110] directions of underlying silicon wafer in order to make perfect squares bounded by (111) planes . The bulge test was first conducted on the silicon nitride films to d etermine its proper residual stress and Young's modulus, being sigma(x ) = 227 +/- 15 MPa and E = 225 +/- 10 GPa, respectively. Then, the com posite membrane made of TiNx together with underlying SiNy was bulged and the related load-displacement variation was measured. Finally, usi ng a simple rule of mixtures formula, the elastic mechanical propertie s of TiN, coatings were determined and compared to those obtained duri ng nanoindentation measurements. Both the Young's modulus and residual stress showed increasing values with increasing bias voltage, nitroge n-to-titanium ratio and coating density. The effect of substrate tempe rature below 600 degrees C was found to be less significant compared t o other parameters. These results are presented and discussed in terms of coating porosity, microstructure and chemical composition determin ed by means of electron probe microscopy. (C) 1997 Elsevier Science S. A.