RAPID THERMAL NITRIDATION OF TITANIUM ON CU/SI CONTACT SYSTEM

The TiN/TiSi2 bilayer formed on n(+)-p junction by rapid thermal annealing (RTA) process was investigated. The various thicknesses of titanium him (10-80 nm) were sputtered on the n(+)Si substrate, then annealed by RTA at a temperature of 850 degrees C for 30 s in a N-2 ambient (850 degrees C/30 s/N-2). Junction leakage current densities of the n(+)-p diodes with TiN/TiSi2 bilayers were about 10 nA/cm(2) for the initial Ti film thickness below 65 nm. The TiN/TiSi2 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/TiSi2/n(+)Si contact system after thermal stress on various temperatures (250-600 degrees 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 degrees C/30 s/N-2. It possessed the TiN (20 nm)/TiSi2 (100 nm) bilayer and the thermal stability temperature up to 475 degrees 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.