Structural properties of as deposited and annealed ZrO₂ influenced by atomic layer deposition, substrate, and doping

Thin ZrO₂ films are of high interest as high-k material in dynamic random access memory (DRAM), embedded dynamic random access memory, and resistive random access memory as well as for gate oxides. Actually, ZrO₂ is predicted to be the key material in future DRAM generations below 20 nm. Profound knowledge of pure and doped ZrO₂ thin films, especially of the structural properties, is essential in order to meet the requirements of future devices. This paper gives a detailed overview about the structural properties of ZrO₂ films in dependence of various process parameters. The study of atomic layer deposition (ALD) growth mechanisms of ZrO₂ on a TiN-substrate in comparison to a Si-substrate covered with native oxide exhibits significant differences. Furthermore, the structural properties crystallinity, surface roughness, and film stress are studied after the ALD deposition in dependence of the process parameters deposition temperature, layer thickness, and underlying substrate. Remarkable dependencies of the ZrO₂ crystallization temperatures on the substrates are figured out. The structural properties after various annealing steps are monitored as well. The influence of doping by SiO₂ and Al₂O₃ is studied, which is primarily used to keep the thin films amorphous during deposition.