ALD of YF3 thin films from TiF4 and Y(thd)3 precursors


ALD of YF3 thin films from TiF4 and Y(thd)3 precursors

Pilvi, T.; Puukilainen, E.; Munnik, F.; Leskelä, M.; Ritala, M.

Yttrium fluoride is a dielectric material with good light transmittance between ultraviolet (UV) and infrared (IR) range of wavelengths. In this paper we introduce the first use of atomic layer deposition (ALD) process of YF3 thin films. The films were grown at 175–325 °C. Y(thd)3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) was used as a cation source and TiF4 as a fluorine precursor. YF3 film growth characteristics as well as structural, optical, and electrical properties were studied. Different methods, such as spectrophotometry, X-ray diffractometry, scanning electron microscopy, atomic force microscopy, and elastic recoil detection analysis were applied to characterize the films. Electrical properties were analyzed from Al/YF3/indium-tin-oxide capacitor structures at room temperature. The growth rates of the films were between 1.1 and 1.7 Å/cycle. The films grown below 225 °C were amorphous, otherwise they were polycrystalline. Permittivities of the films were around 6. The surface roughness of the YF3 films increased with the deposition temperatures. The refractive indices were 1.51–1.59 (at λ = 580 nm), and high light transmittance was achieved from UV to IR region with the sample grown at 300 °C.

Keywords: Atomic layer deposition (ALD); Yttrium fluoride (YF3); Optical materials; Thin films

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Publ.-Id: 11437