Site-Selective Deposition and Micropatterning of SrTiO₃ Thin Film on Self-Assembled Monolayers by the Liquid Phase Deposition Method

We have succeeded in site-selective deposition of SrTiO 3 (STO) thin films on patterned self-assembled monolayers (SAMs) by the liquid phase deposition (LPD) method. SAMs of heptadecafluoro-1,1,2,2,-tetrahydrodecyltrichlorosilanes [HFDTS, CF 3 (CF 2 ) 7 (CH 2 ) 2 SiCl 3 ] were prepared on Si wafers and modified by UV irradiation through a photomask. This SAM template was composed of HFDTS surfaces (Si−CF 3 ) and silanol surfaces. The patterned SAM-covered substrate was then immersed into a (NH 4 )TiF 6 /Sr(NO 3 )/H 3 BO 3 aqueous solution at 50 °C to deposit a solid phase. (NH 4 ) 2 TiF 6, which could form [Ti(OH) n F 6 - n ] 2 - slowly in an aqueous solution, was selected as a source of TiO 3 2 - . H 3 BO 3 was a scavenger of fluorine and was used to control the reaction rate. The STO films were selectively deposited in the silanol regions. The as-deposited film was amorphous containing fluorine as a main impurity. With annealing at 500 °C for 2 h in air, the as-deposited film was crystallized into SrTiO 3 and the fluorine was eliminated. Film morphology was characterized by both SEM and AFM. Metal-oxide-semiconductor (MOS) devices were prepared by using an as-deposited film or a crystallized film as a gate oxide. The dielectric constant of SrTiO 3 thin films and the leakage current of the MOS device were evaluated. These results indicate that the SrTiO 3 film fabricated by a combination of the SAM technique with LPD method through a one-step process is promising for application to dielectric films.