Wednesday, April 4, 2018

ALD of ZrO2 from zirconium tetraiodide and ozone

Please use the free month at ECS and download this excellent paper by Kaupo Kukli et al on probably the best zirconium ALD precursor in the world - behold the Zirconium tetraiodide (ZrI4)! Previously ZrO2 ALD employing ZrI4 has been proven using H2O, H2O/H2O2 and O2 so now the reies is almost compelte - just O2+ missing.

Wikipedia states "The compound was once prominent as an intermediate in the purification of zirconium metal." Refereing to the van Arkel Process, taht is Pyrolysis of zirconium tetraiodide gas by contact of hot wire and that was the first industrial process for the commercial production of pure ductile metallic zirconium. The process was developed by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925, both Dutch chemists. By many this process is a chemical transport process and it relies on two basic chemical reactiosn at elevated temperatures:
M + 2I2 (>400 °C) → MI4
MI4 (1700 °C) → M + 2I2
... and that´s about all the information you need to go ahead and move on to HVM with this one ;-)

Atomic Layer Deposition of Zirconium Dioxide from Zirconium Tetraiodide and Ozone
Kaupo Kukli, Marianna Kemell, Kenichiro Mizohata, Marko Vehkamäki, Kristjan Kalam, Helena Castán, Salvador Dueñas, Joosep Link, Raivo Stern, Mikko Ritala, and Markku Leskelä
Abstract : ZrO2 thin films were grown by atomic layer deposition using alternate surface reactions of ZrI4 and O3 precursors in the temperature range of 250–400°C to the thickness in the range of 5–100 nm. The films were dense, continuous, and consisted of mixed monoclinic and metastable polymorphs with significant contribution from cubic ZrO2. The ZrO2 films possessed permittivity up to 19. The capacitor structures based on these films also demonstrated tendency to resistive switching behavior. The ZrO2 films exhibited saturative magnetization under external magnetic fields.