Papers by Keyword: ALCVD

Abstract: Al2O3 grown by Atomic Layer Chemical Vapour Deposition (ALCVD) on n-type 4H-SiC with a nominal thickness of 100nm has been characterized by Grazing Incidence X-Ray Diffraction (GIXD) and Specular X-Ray Reflectivity (SXR) measurements. After post-deposition, the samples were annealed at different temperatures and durations in argon atmosphere. The GIXD results reveal crystallization at temperatures above 900°C, most likely in the form of θ-Al2O3 or γ-Al2O3. However, the formation of a new, non-stoichiometric Al2O3 phase cannot be excluded. The crystalline domain size, evaluated from the peak FWHMs after subtraction of the instrumental broadening, is found to be almost equal (18±1nm), independent of T in the range 900°C≤T≤1100°C and time in the range 1h≤t≤3h. From SXR, mass density profiles are derived. Whereas the as grown film exhibits the lowest mass density, at 800°C a low-density interface layer forms. At the same time, it appears that the initial crystallization starts at the surface. At 900°C, the density increases sharply (this process involves film crystallization) and the film thickness correspondingly reduces. Whereas the density increase and thickness reduction still continue for T>900°C (tendency to the density α-Al2O3), the density of the interfacial layer has a minimum at 900°C and gradually increases for higher temperatures. From Atomic Force Microscopy (AFM) investigations it could be revealed that the starting of the crystallization at 900°C is accompanied with a substantial surface roughening. For annealing at higher temperatures, the surface roughness is in the range of the one of the as-grown sample (about 6Å).

Abstract: Al2O3 has been grown by Atomic Layer Chemical Vapour Deposition (ALCVD) on ntype 4H-SiC using O3 as an oxidant and tri-methyl-aluminum (TMA) as a precursor. After deposition, annealing at 1000°C during 3h in different atmospheres (Ar, N2 and O2) was performed. Interface properties were studied by Capacitance-Voltage (CV) and Thermal Dielectric Relaxation Current (TDRC) measurements. The highest near-interface trap density (Nit) was deduced to be 4x1012 eV-1cm-2 between 0.36 eV and 0.5 eV below the conduction band, Ec, for O2 annealed samples, 2.8x1012 eV-1cm-2 between 0.42 eV and 0.56 eV below Ec for Ar annealed samples and 2.2x1012 eV-1cm-2 between 0.4 eV and 0.6 eV below Ec for N2 annealed samples. Only samples annealed in Ar exhibit a nearly trap free region close to Ec. Annealing in N2 is found to decrease Nit between 0.3 and 0.7 eV but shows a slightly higher Nit close the conduction band compared to the Ar case.

Abstract: Al2O3 has been grown by Atomic Layer Chemical Vapour Deposition (ALCVD) on ntype 4H-SiC using O3 as an oxidant. After post-deposition, annealing at high temperature (1000°C) in Argon atmosphere for different time periods (1h, 2h, 3h) was performed. Bulk and interface properties of the as-grown as well as the annealed films were studied by electrical measurements (CV, IV, DLTS) and Secondary Ion Mass Spectrometry (SIMS) measurements. The electrical measurements show a decreasing shift of the flatband voltage indicating a diminution of the negative oxide charges with increasing annealing time. After annealing at 1000°C for 3h, the flatband voltage shift has decreased to 6V. The SIMS measurements indicate a double interface with a SiOx (x ≤ 2) interlayer in the as-grown samples while only one interface is observed after annealing, leading to improved electrical behavior of the Metal-Oxide-Semiconductor devices.

Abstract: In this study, electrical properties of Al2O3 deposited by Atomic Layer Deposition (ALCVD) on n-type 4H-SiC were investigated. Metal-Oxide-Semiconductor (MOS) capacitors were characterized by various electrical techniques such as Capacitance-Voltage (CV), Current- Voltage (IV) and Deep Level Transient Spectroscopy (DLTS) measurements. Two different oxidants, H2O and O3, have been used for the oxide deposition. After deposition, the flat-band voltage shift is much less using O3 than H2O (~ 7V versus ~ 20V). Annealing treatment has been carried out at different temperatures in Ar atmosphere up to 700°C. Whereas the flat-band voltage shift can be reduced by annealing, the leakage current remains rather high.