Barrier properties and failure mechanism of sputtered Zr-Si amorphous thin films of various compositions were studied for the application as a diffusion barrier for Cu metallization. X-ray diffraction (XRD) measurements show that the Zr-Si barriers have amorphous structure in the as-deposited state. The Cu/Zr-Si/Si structures were manufactured and annealed in Ar ambient at the temperature up to 650 degrees C for 1 h. XRD, scanning electron microscopy, and variations of Cu sheet resistance as a function of the annealing temperature were conducted to evaluate the barrier performance of Zr-Si films. The specimen including Zr42Si58 film is stable up to 600 degrees C and that with Zr36Si64 and Zr84Si16 film up to 650 degrees C. The experimental findings revealed that the failure mechanism of the studied films involved the crystallization of Zr42Si58 film that occurred at 650 degrees C. The grain boundary of the crystalline structure provides paths along which the copper atoms penetrate through the barrier layer to react with the underlying Si substrate to form the Cu3Si phase. The Zr36Si64 and Zr84Si16 films remain the amorphous structure even after annealing at 650 degrees C. This amorphous structure is beneficial for blocking rapid copper diffusion paths. (c) 2008 The Electrochemical Society. [DOI: 10.1149/1.2987938] All rights reserved.