Spike Annealing as Second Rapid Thermal Annealing to Prevent Pure Nickel Silicide From Decomposing on a Gate

To create a nickel-monosilicide (NiSi) film with superior electrical properties, two-step rapid thermal annealing (RTA) was optimized. Using in situ chemical dry cleaning and increasing initial RTA temperature makes it possible to macroscopically transform nickel into NiSi without causing oxygen contamination. Nevertheless, di-nickel silicide (Ni₂Si) remaining on the top surface of NiSi on p⁺-doped gate degrades the electrical properties of the NiSi film. This top-surface Ni ₂Si is formed by decomposition of NiSi by conventional second RTA and appears as a disconnection of the NiSi film on the logic test device or agglomeration of silicon and nickel on the blanket NiSi film with activation energy of 2.92 eV. Using ldquospike RTArdquo with higher temperature suppresses the decomposition of NiSi and activates transformation of Ni₂ Si to NiSi. It is concluded that the proposed two-step RTA significantly improves the uniformity of the electrical properties of NiSi in 65-nm-node logic devices.