ＴｉＮ薄膜の応力負荷に伴う破壊形態のその場ＡＦＭ表面観察

Abstract

Fracture behaviors of TiN thin films and their dependence on substrate materials are clarified by in-situ surface observations of TiN thin films under tensile stress using AFM (Atomic Force Microscopy). The system has the ability to observe surface structures with atomic resolution under uni-axial tensile force. Specimens of TiN thin films on Si, Au and Pt substrate materials were prepared. The TiN thin films were deposited on Si test chips by electron beam evaporation in Na atmosphere. The Au and Pt substrates were prepared on the test chip before TiN deposition by magnetron spattering. Three types of surface patterns that depended on the elasticity and thickness of substrate materials were observed. TiN thin films deposited on Si, Pt substrates showed periodic cracks that were perpendicular to the tensile force irrespective of substrate thickness. The periodicity in TiN thin films was explained by the Grinfeld instability. However, TN films on Au substrate showed strong dependence with substrate thickness. When the substrate thickness was below 20 run, the same crack patterns were observed, but the crack length tended to be repressed with increasing thickness. TIN films on Au substrates that were thicker than 60 nm exhibited a large number of small dotted cracks. These dramatic changes of fracture patterns were attributed to the stress relaxation of substrate materials.