Growth Characteristics of Atomic Layer Deposited TiO2 Thin Films on Ru and Si Electrodes for Memory Capacitor Applications

TiO2 thin films were grown by an atomic-layer-deposition process at growth temperatures ranging from 200 to 300DGC on Ru and Si substrates using Ti[OCH(CH3)2]4 and H2O as metal precursor and oxygen source, respectively, for metal-insulator-metal capacitor application in dynamic random access memories. The saturated film growth rate on Ru and Si substrates was 0.034 and 0.046 nm/cycle, respectively. The TiO2 film growth on a Ru substrate showed a rather long incubation period and the incubation period decreased with increasing Ti[OCH(CH3)2]4 pulse time, whereas the H2O pulse time had almost no influence on the incubation period. A growth rate transition, from low to high values, (thickness 7-8 nm) was observed when the films were grown at temperatures > 250DGC, whereas the films grown at lower temperatures did not show the transition. The transition was due to the structural change of the film from an amorphous/nanocrystalline to the well-crystallized polycrystalline anatase phase. The TiO2 films grown at temperatures > 250DGC showed a dielectric constant of ~35. A 14-nm-thick TiO2 film showed an equivalent oxide thickness of 1.7 nm and a leakage current density of 5 X 10-6 A/cm2 at 1 V.