Biomimetic Micropatteming of Titanium Dioxide Thin Films for Gate Dielectrics

We have succeeded in fabricating micropatterns of TiO2 thin films on self-assembled monolayers (SAMs). SAMs of OTS (octadecyltrichlorosilane) were formed on Si wafers and modified by UV irradiation using a photomask to generate octadecyl/silanol-pattern. They were used as templates to deposit TiO2 thin films by the use of TDD (titanium dichloride diethoxide) dissolved in toluene. Amorphous films were selectively deposited on silanol regions. Line width variation of the pattern was improved to be well below the current electronics design rule, 5%. Dielectric constant of an as-deposited TiO2 thin film, dielectric properties of TiO2/SiO2/Si interface and leakage current density were evaluated by measuring I-V and C-V characteristics of the MOS (metal-oxide-semiconductor) device. Rather low leakage current was observed under high electric fields and the TiO2 thin film with the thickness ～18 nm showed dielectric constant of ～22 at 100 kHz, which is more than 5 times as large as that of a usual SiO2 dielectric layer. However, the resistivity of the TiO2 film was estimated to be not high enough and the dielectric constant depended on frequency, both of which are disadvantages for a gate dielectric