Rapid thermal nitridation of titanium on Cu/Si contact system

Abstract

The TiN/TiSi 2 bilayer formed on n +- p junction by rapid thermal annealing (RTA) process was investigated. The various thicknesses of titanium film (10–80 nm) were sputtered on the n +Si substrate, then annealed by RTA at a temperature of 850°C for 30 s in a N 2 ambient (850°C/30 s/N 2). Junction leakage current densities of the n +- p diodes with TiN/TiSi 2 bilayers were about 10 nA/cm 2 for the initial Ti film thickness below 65 nm. The TiN/TiSi 2 bilayer was used as a diffusion barrier between Cu and n +Si. Leakage current density and specific contact resistance measurements were performed on the Cu/TiN/TiSi 2/ n +Si contact system after thermal stress on various temperatures (250–600°C). The thermal stability temperature increasing with initial Ti film thickness was found. The optimum diffusion barrier for Cu n + Si contact system was the sample with initial Ti film thickness 50 nm after RTA 850°C/30s/N 2. It possessed the TiN (20 nm)/TiSi 2 (100 nm) bilayer and the thermal stability temperature up to 475°C for the Cu n + Si contact system. We also displayed cross-section transmission electron microscopy and glancing angle incident X-ray diffraction data at various sintering temperatures and studied the failure mechanism.