Papers by Keyword: Dielectric Film

Abstract: A new technique is described by which ionic species can be rapidly transported into oxide films, and once there provide effective and stable field effect passivation to silicon surfaces. Field effect passivation in thermally grown oxide films has been achieved by embedding potassium ions using a combined drift and diffusion mechanism at high temperature. This process has been shown to be over 10 times faster than a pure diffusion process. The resulting passivation stable for periods exceeding 600 days, with lifetimes reaching 1.4 ms, equivalent to a surface recombination velocity (SRV) ≤ 5.7 cm/s, on 1 Ωcm, n-type, FZ-Si.

Abstract: An investigation of the parasitic surface recombination mechanisms in high-lifetime oxidized n-Si is presented. An approximate analytical expression describing recombination at the edge of square shaped specimens is derived. This shows that edge recombination can have a significant effect on the effective lifetime as measured using the transient photo-conductance technique and that for well passivated high quality material edge recombination can be the dominant mechanism in reducing the effective lifetime below the intrinsic level. For 3 x 3 cm² pieces of silicon measured using a Sinton photo-conductance lifetime instrument, it is shown that recombination at the edge of the sample results in an additional component to the measured lifetime of around 16 ms at an injection level of 10¹⁵ cm^-3. When this effect is taken into account measurements of 1 Ωcm FZ-Si show that a SRV as low as 1.5 cm/s is possible when the surface is passivated using a corona charge concentration of +2.2 x 10¹² q/cm² deposited on a 100 nm oxide layer.

Abstract: The new fabrication method of dielectric membrane structures for sensitive elements of gas sensors, based on the separation of anisotropic etching of silicon into two stages, is proposed. The preference etchant compositions, the preference elemental composition of membrane films and the acceptable thickness of the thermal silicon oxide underlay to obtain mechanically relaxed membranes are presented. The group technology for manufacturing of sensitive elements for gas sensors is developed, membrane structures are fabricated and their properties are studied.

Abstract: The article presents the properties study results of the dielectric membranes for sensitive elements of semiconductor gas sensors, obtained by different modes of the reactive magnetron sputtering of silicon with application of the two-stage unilateral anisotropic etching of silicon in the organic alkaline solutions. The qualitative analysis of the membranes stability to destructions and deformations in the course of their fabrication and heating is given. Optimum structures and modes of films formation for dielectric membrane structures are determined. The admissible thickness of the thermal silicon oxide underlay, which is does not promote to considerable membranes deformations in the course of their fabrication and heating, is identified.

Abstract: Metal-insulator-semiconductor (MIS) diodes with Si₃N₄/Al₂O₃ bilayer gate dielectric films deposited on an AlGaN/GaN heterostructure were fabricated, where the Si₃N₄ layer played a role of etching stopped layer to protect the Al₂O₃ film from being damaged. Compared with traditional Schottky diodes, a distinct suppression of gate leakage current was achieved for the MIS diodes both at forward and reverse bias, and the dominant leakage current mechanism is Fowler–Nordheim tunneling. The 2DEG density extracted from C-V curves was 3~7 ́10¹³cm^-2, in the same order of magnitude as Schottky diodes and hall measurement. Although the existence of the bilayer dielectric did not affect the 2DEG density at the interface of AlGaN/GaN, Si₃N₄ layer shared more gate bias and led to more gate bias required to deplete 2DEG and turn down the devices, moreover, Si₃N₄ layer had no effect on suppressing the forward or reverse gate leakage current due to its narrow band gap width and band bending compared with a single Al₂O₃ film. The experimental results provided a reference for the design of gate dielectric film structure for AlGaN/GaN high-electron-mobility transistors (HEMTs).

Abstract: Ba_0.5Sr0.5TiO₃ film was successfully fabricated by micro arc oxidation of titanium plate in aqueous solution containing Sr(OH)₂ and Ba(OH)₂ for 25 minutes. X-ray diffraction , energy dispersive spectrometer and scanning electron microscopy were used to characterize the crystalline structure, elements composition and surface morphology and HP4284 capacitance prober was used to analyze the dielectric properties of the film. The micro arc oxidation film is mainly composed of tetragonal Ba_0.5Sr0.5TiO3 phases and possesses both high dielectric constant of 454.2 and low dielectric loss of 0.052 at the frequency of 100Hz.The surface morphology appeares smooth and homogeneous except that some holes are uniformly distributed outwardly.

Abstract: Pure titanium plates as anode and mixture of solutions containing 0.2M Sr(OH)₂ and 0.2M NaOH as electrolyte, titanium plates were microarc-oxidated for 10 minutes. X-Ray Diffraction (XRD) analysis indicated that SrTiO₃ film was successfully deposited. The MAO film is composed mainly of tetragonal SrTiO₃ phases and found to possess high dielectric constant of 371.0 at the frequency of 1 kHz. Scanning Electron Microscopy (SEM) and portable roughness tester were used to characterize the surface morphology and roughness values(Ra), The influences of electrolyte concentration, current density and frequency on the surface morphology of SrTiO₃ film were investigated in detail . several rules were drawn from the results. A kinetics expression was established for the growth of film thickness and agreed well with the experimental results.