Low-Temperature Deposition of Polycrystalline Titanium Oxide Thin Film on Si Substrate Using Supercritical Carbon Dioxide Fluid

摘要

A novel technique for the deposition of oxide thin films using supercritical carbon dioxide (CO_2) fluid was proposed for the large-scale circuit integration on a silicon (Si) substrate at a low temperature. Thin films of titanium oxide (TiO_2) as a model material were fabricated from organometallic Ti(Oi-Pr)_2(dpm)_2 source on (100)Si substrates in supercritical CO_2 fluid. The film deposition was accomplished using a flow-type supercritical fluid deposition apparatus designed on the basis of metal-organic chemical vapor deposition (MOCVD) systems. Flat films were fabricated on (100)Si substrates at a faster source delivery (fluid flow rate: 2.0-10.0 cm~3/min), while granular deposits owing to homogeneous nucleation in the bulk supercritical CO_2 fluid appeared on the substrates at a slower source delivery (fluid flow rate: 1.0cm~3/min). The amount of TiO_2 deposited decreased gradually with increasing the temperature of CO_2 fluid, which would be related to the change in the density of CO_2 fluid. The crystalline TiO_2 film was deposited on the (100)Si substrate at a substrate temperature of 80-120℃ and fluid temperature/pressure of 40℃/8.0MPa, at which the decomposition of organometallic Ti(Oi-Pr)_2(dpm)_2 source was accomplished. These results indicated that the supercritical CO_2 deposition technique is suitable for the large-scale circuit integration on Si substrates.