title: Controlling the crystallinity and roughness of atomic layer deposited titanium dioxide films.
abstract: The surface roughness of thin films is an important parameter related to the sticking behaviour of surfaces in the manufacturing of microelectomechanical systems (MEMS). In this work, TiO2 films made by atomic layer deposition (ALD) with the TiCl4-H2O process were characterized for their growth, roughness and crystallinity as function of deposition temperature (110-300 degrees C), film thickness (up to approximately 100 nm) and substrate (thermal SiO2, RCA-cleaned Si, Al2O3). TiO2 films got rougher with increasing film thickness and to some extent with increasing deposition temperature. The substrate drastically influenced the crystallization behaviour of the film: for films of about 20 nm thickness, on thermal SiO2 and RCA-cleaned Si, anatase TiO2 crystal diameter was about 40 nm, while on Al2O3 surface the diameter was about a micrometer. The roughness could be controlled from 0.2 nm up to several nanometers, which makes the TiO2 films candidates for adhesion engineering in MEMS.
authors.affiliation: VTT Technical Research Centre of Finland, P.O. Box 1000, Fl-02044 VTT Espoo, Finland.
authors.forename: Riikka L
authors.initials: RL
authors.lastname: Puurunen
authors.forename: Timo
authors.initials: T
authors.lastname: Sajavaara
authors.forename: Eero
authors.initials: E
authors.lastname: Santala
authors.forename: Ville
authors.initials: V
authors.lastname: Miikkulainen
authors.forename: Tapio
authors.initials: T
authors.lastname: Saukkonen
authors.forename: Mikko
authors.initials: M
authors.lastname: Laitinen
authors.forename: Markku
authors.initials: M
authors.lastname: Leskelä