Materials and thermal stability of tantalum carbide layers for metal gate applications

Phase compositions and thermal stability of different TaC_x layers deposited by PVD is studied using in-situ high-temperature XRD (HT-XRD). It is found that the phase composition of the as-dep. layers and those during annealing at high temperatures strongly depends on their chemical compositions. Low carbon layers (~Ta₄C) are amorphous below 700degC, and crystallize into hexagonal Ta₂C in 700-900degC. At 1150degC, the Ta₂C is replaced by TaSi₂. Stoichiometric Ta₂C are also dominantly amorphous below 900degC and starts to form cubic TaC at 900degC, and TaSi₂ at 1100degC. The as-dep. TaC layers are crystalline, with a dominant cubic TaC phase. At 1000degC, the TaC is replaced by TaSi₂