The Effects of High Temperature Exposure on the Fracture of Thin Tantalum Nitride Films

Abstract

ABSTRACTContinuous microscratch testing was used in this study to determine the effects of elevated temperature exposure on the adhesion and toughness of thin tantalum nitride films. These films were sputter-deposited at room temperature on sapphire substrates to a nominal thickness of 600 nm with some films heated to 600°C in vacuum while others were heated to 600°C in air. The films heated in vacuum exhibited no changes in composition or structure while the films heated in air completely transformed to tantalum pentoxide. Comparison of the results shows that the interfacial fracture toughness increases from 0.5 MPa-m1/2 for as-sputtered films to 0.8 MPa-m1/2 for films heated in air. However, the toughness increases to more than 3.0 MPa-m1/2 when the films are heated in vacuum. The increase in toughness values follows the reduction in deposition defect content where formation of an oxygen deficient tantalum oxide layer in air from the as-sputtered film increases interfacial toughness slightly while full densification of the tantalum nitride films in vacuum increases toughness to very high levels.