title: Selective growth of titanium dioxide by low-temperature chemical vapor deposition.
abstract: A key factor in engineering integrated optical devices such as electro-optic switches or waveguides is the patterning of thin films into specific geometries. In particular for functional oxides, etching processes are usually developed to a much lower extent than for silicon or silicon dioxide; therefore, selective area deposition techniques are of high interest for these materials. We report the selective area deposition of titanium dioxide using titanium isopropoxide and water in a high-vacuum chemical vapor deposition (HV-CVD) process at a substrate temperature of 225 °C. Here—contrary to conventional thermal CVD processes—only hydrolysis of the precursor on the surface drives the film growth as the thermal energy is not sufficient to thermally decompose the precursor. Local modification of the substrate surface energy by perfluoroalkylsilanization leads to a reduced surface residence time of the precursors and, consequently, to lower reaction rate and a prolonged incubation period before nucleation occurs, hence, enabling selective area growth. We discuss the dependence of the incubation time and the selectivity of the deposition process on the presence of the perfluoroalkylsilanization layer and on the precursor impinging rates—with selectivity, we refer to the difference of desired material deposition, before nucleation occurs in the undesired regions. The highest measured selectivity reached (99 ± 5) nm, a factor of 3 superior than previously reported in an atomic layer deposition process using the same chemistry. Furthermore, resolution of the obtained patterns will be discussed and illustrated.
authors.affiliation: Laboratory for Advanced Materials Processing, Empa, Swiss Federal Laboratories for Materials Science and Technology, Feuerwerkerstrasse 39, CH-3602 Thun, Switzerland.|Laboratory for Photonic Materials and Characterization, Ecole Polytechnique Fédérale de Lau-sanne, Station 17, CH-1015 Lausanne, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Reinke
authors.affiliation: Laboratory for Advanced Materials Processing, Empa, Swiss Federal Laboratories for Materials Science and Technology, Feuerwerkerstrasse 39, CH-3602 Thun, Switzerland.|Laboratory for Photonic Materials and Characterization, Ecole Polytechnique Fédérale de Lau-sanne, Station 17, CH-1015 Lausanne, Switzerland.
authors.forename: Yury
authors.initials: Y
authors.lastname: Kuzminykh
authors.affiliation: Laboratory for Advanced Materials Processing, Empa, Swiss Federal Laboratories for Materials Science and Technology, Feuerwerkerstrasse 39, CH-3602 Thun, Switzerland.|Laboratory for Photonic Materials and Characterization, Ecole Polytechnique Fédérale de Lau-sanne, Station 17, CH-1015 Lausanne, Switzerland.
authors.forename: Patrik
authors.initials: P
authors.lastname: Hoffmann
keywords: atomic layer deposition; chemical vapor deposition; selective area growth; self-assembled monolayer; silanization; titanium dioxide; titanium isopropoxide