Process Optimization of CoSi₂ Formation on P-Doped Poly-Si by Hot Wall-Based Rapid Thermal Annealing

Abstract

To achieve low resistivity contacts, the effect of annealing temperature and time on the resulting resistivity of CoSi2 contacts with P-doped poly-Si was investigated using a single wafer furnace-based (hot wall) rapid thermal annealing (RTA) system. The hot wall RTA resulted in significantly (>20%) lower sheet resistance (Rs) from the equivalent RTA process using conventional tungsten halogen lamp-based (cold wall) RTA systems over a very wide process window. Dopant (P) depth profiling results by secondary ion mass spectroscopy (SIMS) revealed that the P atoms in the CoSi2 film and at the CoSi2/P-doped poly-Si interface, redistribute very differently under different RTA conditions. The CoSi2 formation process was optimized utilizing characteristics of P pile-up near the CoSi2/P-doped poly-Si interface to suppress P depletion from the P-doped poly-Si layer.