Fuquan Song

Advanced cyclopentadienyl precursors for atomic layer deposition of ZrO2 thin films

ZrO2 thin films were grown onto silicon (100) substrates by atomic layer deposition (ALD) using novel cyclopentadienyl-type precursors, namely (CpMe)2ZrMe2 and (CpMe)2Zr(OMe)Me (Cp = cyclopentadienyl, C5H5) together with ozone as the oxygen source. Growth characteristics were studied in the temperature range of 250 to 500 °C. An ALD-type self-limiting growth mode was verified for both processes at 350 °C where highly conformal films were deposited onto high aspect ratio trenches. Signs of thermal decomposition were not observed at or below 400 °C, a temperature considerably exceeding the thermal decomposition temperature of the Zr-alkylamides. Processing parameters were optimised at 350 °C, where deposition rates of 0.55 and 0.65 A cycle−1 were obtained for (CpMe)2ZrMe2/O3 and (CpMe)2Zr(OMe)Me/O3, respectively. The films grown from both precursors were stoichiometric and polycrystalline with an increasing contribution from the metastable cubic phase with decreasing film thickness. In the films grown from (CpMe)2ZrMe2, the breakdown field did not essentially depend on the film thickness, whereas in the films grown from (CpMe)2Zr(OMe)Me the structural homogeneity and breakdown field increased with decreasing film thickness. The films exhibited good capacitive properties that were characteristic of insulating oxides and did not essentially depend on the precursor chemistry.

An Ab Initio Evaluation of Cyclopentadienyl Precursors for the Atomic Layer Deposition of Hafnia and Zirconia

Thin film dielectrics based on hafnium or zirconium oxides are being introduced instead of silica to increase the permittivity of insulating layers in nanoelectronic transistor and memory devices. Atomic layer deposition (ALD) is the process of choice for fabricating these films, and the success of this method depends crucially on the chemical properties of the precursor molecules. Much promise is shown by Hf and Zr metallocenes, i.e. precursors that contain cyclopentadienyl (Cp) ligands [1].