Thermal stability study of TiN/TiSi2 diffusion barrier between Cu and n +Si

• Published in: Journal of applied physics 1994-06, Vol.75 (12), p.7847-7851
• Main Authors: Chang, Tzong-Sheng, Wang, Wen-Chun, Wang, Lih-Ping, Hwang, Jenn-Chang, Huang, Fon-Shan
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.356568

The failure mechanism of the TiN/TiSi2 bilayers as diffusion barriers between Cu and n+Si was investigated. The TiN/TiSi2 bilayers were formed by either annealing Ti (50 nm)/n+Si via various rapid thermal processes or reactively sputtering TiN (50 nm) on TiSi2. The degradation study of the Cu/TiN/TiSi2/n+Si contact system was undertaken by scanning electron microscopy, cross-section transmission electron microscopy (XTEM), secondary-ion-mass spectrometry (SIMS), and diode leakage current and contact resistance measurements. Leakage current measurements indicated no deterioration of n+-p diode junctions up to 475 °C for 30 min in a N2 ambient. For the sintering temperature at 500 °C, the leakage current increased abruptly and SIMS profiles revealed a large amount of Cu atoms diffusing into the junctions of n+-p diodes. XTEM showed that the small pyramidal-shaped Cu3Si crystallite (with a size 0.25 μm) precipitated in the n+Si substrate. The formation of Cu3Si increased the occupied volume, then generated the gap between TiSi2 and n+Si, and gradually increased the specific contact resistance. The diffusion resistance, depending on the thickness of TiN film, was also observed.