Hf-silicate films were deposited directly onto n-type Si (100) substrates and Pt-coated Si substrates by a pulsed laser deposition technique using a ceramic Hf-silicate target. The thermal stability and electrical properties of Hf-silicate films have been investigated by x-ray diffraction, differential thermal analysis, atom force microscopy, x-ray photoelectron spectroscopy, capacitance-voltage (C-V ) and leakage current-voltage (I -V ) measurements. The amorphous structure of Hf-silicate films was found to be stable up to at least 900˚C. A crystallization transformation from the amorphous phase to a polycrystalline tetragonal structure occurs under rapid thermal annealing for 3 min at 1000˚C. The amorphous Hf-silicate film exhibits a high dielectric constant of about 14.1 measured in a Pt/Hf-silicate/Pt capacitor structure. The smoothness and electrical properties of films have been improved by rapid thermal annealing in N 2 ambient at 900˚C for 30 s. A very small equivalent oxide thickness of 0.95 nm for 2.6 nm Hf-silicate film on the n-Si substrate and a low leakage current of 24 mA cm −2 at 1 V gate voltage were obtained. Thus, Hf-silicate films with good thermal stability can be one of the most promising candidates for future high-k gate dielectric applications.
We investigated the structural and electrical properties of HfO2 films fabricated by the pulsed laser deposition technique. HfO2 films were deposited directly on n-Si (100) substrates and Pt coated silicon substrates, respectively, at 300°C in a 20 Pa N2 ambient, and in situ post-annealed in a 20 Pa N2 ambient. X-ray diffraction indicates that films post-annealed at temperatures more than 500°C exhibit a polycrystalline monoclinic structure. High-resolution transmission electron microscopy images clearly show that an interfacial layer (IL) between an amorphous HfO2 layer and the Si substrate exists. An x-ray photoelectron spectroscopy measurement was performed to identify this IL as nonstoichiometric Hf-silicate. The dielectric constant of amorphous HfO2 was determined to be about 26 by measuring the Pt/HfO2/Pt capacitor structures. Capacitance–voltage measurements show that a small equivalent oxide thickness of 1.26 nm for the 5 nm HfO2 film on the n-Si substrate, with a leakage current of 2.2 mA cm−2 at 1 V gate voltage was obtained.
Strontium barium niobate (SBN) thin films were grown on Si (111) substrates coated with MgO buffer by the pulsed laser deposition (PLD) technique. The thickness of SBN and MgO films were of the order of 1200 nm and 840 nm respectively. X-ray energy dispersive spectrometry (XREDS) showed that SBN films have stoichiometric composition identical to the target material, and no Si diffusion into the SBN film was found. X-ray diffraction (XRD) scans indicated that MgO films were highly (111) textured, but the SBN films were polycrystalline without preferential orientation. The surface of the SBN film was smooth, dense and crack-free and no large droplets were observed when studied under a scanning electron microscope (SEM). A favourable optical waveguiding property of the bilayered films was demonstrated by a prism coupler method.
We have studied the formation of a high-quality LaAlO 3 (LAO) film directly on silicon substrates by the pulsed laser deposition method as a novel high-k gate dielectric. The LAO films can remain amorphous at temperatures up to 850˚C. An atomic force microscopy study indicated a very smooth surface of the deposited films with a rms of 0.14 nm for an 8 nm LAO film. The structures and electrical properties of metal-dielectric-semiconductor (Pt/LAO/Si) capacitors were investigated with LAO films deposited under different ambient conditions. High-resolution transmission electron microscopy indicated that interfacial reactions often occur for films of LAO deposited under oxygen ambient. A small effective oxide thickness of 1.2 nm was obtained for those films deposited under 20 Pa nitrogen ambient, with the corresponding leakage current density 17.1 mA cm −2 at +1 V gate voltage. It is proposed that amorphous LAO films are a novel promising alternative high-k gate dielectric material in future ultra-large scale integrated devices.
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