Stable TiO x Submicrometer Channels J. Scarminio, a, * E. L. Rigon, b Lucila Cescato, b and A. Gorenstein b, * ,z a Departimento Fı ´sica, UEL, CEP 86051-970, Londrina, Pr, Brazil b Instituto de Fisica Gleb Wataghin, Unicamp, 13083-970, Campinas, SP, Brazil The fabrication of submicrometer, stable channels of radio-frequency sputtered metallic titanium and titanium oxide films with different stoichiometries is described in this work. The structure was obtained by coating the films on structures previously holographically recorded in photoresists on glass substrates, and subsequently dissolving the photoresist. Stable channel structures were obtained for all compositions of the TiO x films. For very thin films 10 nm thick the structures recorded on TiO 2 presented less stability. © 2002 The Electrochemical Society. DOI: 10.1149/1.1524614 All rights reserved. Manuscript submitted May 1, 2002; revised manuscript received July 1, 2002. Available electronicallyNovember 21, 2002. The advent of micro- and nanofabricated devices opened the pos- sibility for performing a vast range of new tasks in such areas as life science, biotechnology, environmental monitoring, etc. 1-4 Most of the systems are silicon-based, since Si patterning is the most mature technology. 5 Channel architectures of submicrometer sizes have po- tential applications in many fields. 5 In addition, titanium oxide films present electrical and optical properties that are adequate for explor- ing microelectronics, 6 solar energy conversion, 7 and photolysis, 8 as a few examples. In a previous work, 9 the patterning of stable, hollow submicro- metric structures in titanium oxide films deposited by plasma- enhanced chemical vapor deposition PECVD was described. The production of submicrometer, stable channels of radio frequency rf sputtered titanium oxide films with different stoichiometries is de- scribed in this work. The deposition of titanium oxide films by sput- tering allows a controllable change in their composition, from pure metallic Ti to stoichiometric TiO 2 films. Since the optical and elec- trical properties of TiO x films are dependent on the composition, this technique allows the production of films with properties ranging from opaque, conductive films to transparent, insulating materials. The ability to tailor these properties, allied to the channel structures, can be explored in different applications. Experimental The structures were obtained by holographically recording a pho- toresist relief grating structure on a glass substrate, depositing the TiO x film on the whole structure, and subsequently dissolving the photoresist. The photoresist AZ1518 from Hoechst diluted in the proportion 1:1 in AZ thinner, was spin-coated onto glass substrates 7059 Corn- ing glass, of dimensions 2.5  2.5 cm. In order to obtain channels with two distinct aspect ratios, the rotation speed was set at 1000 or 3000 rpm, generating photoresist films with average thickness of 790 and 480 nm, respectively. The photoresist film thickness were measured by profilometry Dektak 3. In order to evaporate the re- sidual solvent, the samples were submitted to a heat-treatment in an oven for 20 min at 70°C. The coated samples were then exposed in a holographic setup using the 457.9 nm line of an argon laser model 165, from Spectra Physics. Figure 1 presents the scheme of the holographic setup, which consists mainly of an interferometer, re- sponsible for a homogeneous fringe pattern generation in 25 cm 2 square area. This fringe pattern is frozen during the exposure by using a fringe locker system. 10 The exposure energy was about 350 mJ cm -2 depending on the photoresist film thickness, and the expo- sure time was about 200 s, depending on the laser intensity. After exposure, the samples were developed in AZ 351 developer from Hoechst diluted in the proportion 1:3 in deionized water. In sequence, films of titanium oxide were deposited by rf mag- netron sputtering from a titanium target, under an O 2 -Ar atmo- sphere. The equipment was a BAE-250 deposition system from Balzers Instruments. In order to obtain films with different stoichi- ometries, the samples were deposited at four different oxygen flow- rates , in the range 0 sccm standard cubic centimeter per minute to 2.2 sccm. The gas flow was controlled by means of a flowmeter model 825, BOC Edwards. The initial pressure was about 1.5  10 -6 mbar, and the total pressure during deposition was 7.0  10 -3 mbar. The power was maintained at 300 W. Spectral transmittance was measured with a Lambda-9 Perkin- Elmer spectrophotometer on nonpatterned films coated on glass sub- strates 7059 Corning glass plates. The thickness of the films was varied by controlling the deposition rate and deposition time, and was measured with an -step profilometer, Tencor Instruments. The X-ray diffraction measurements were done using a URD-6 Zeiss-Jena diffractometer, in the Bragg-Brentano geometry. All measurements were performed at room temperature within the range of 2  = 10-70° with step scanning mode, 0.05°/step and counting time of 10 s. The diffractometer was operated at 40 kV/30 mA using monochromatic CuK radiation 1.2 kW,  1.54 Å). The analy- sis showed that all films were amorphous or nanocrystalline. Finally, for removal of the photoresist, the samples were im- mersed in acetone. Investigation of the microstructure profile was carried out by a cross-sectional view of the samples using a scan- ning electron microscope SEM model JSM5410, from JEOL. For imaging, a 10 nm gold film was deposited on the films. * Electrochemical Society Active Member. z E-mail: annette@ifi.unicamp.br Figure 1. Holographic setup used to record the photoresist structures. BS is a beam splitter, DET is a detector, PZT is a mirror supported by piezoelectric crystals. The expanded and collimated beams generate a spot size of about 80 cm 2 . The setup is provided with an active stabilization system fringe locker which corrects the environmental phase perturbations through the movement of the PZT. Journal of The Electrochemical Society, 150 1 H17-H20 2003 0013-4651/2002/1501/H17/4/$7.00 © The Electrochemical Society, Inc. H17 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 143.106.1.143 Downloaded on 2014-09-05 to IP