Chemical Vapor Deposition最新文献

Metal-organic (MO)CVD of ZrO₂ thin films is performed using the precursor [Zr(NMe₂)₂(guan)₂] (guan = η²-(ⁱPrN)₂CNMe₂) as the Zr source, together with oxygen. Film deposition is carried out on both Si(100) and glass substrates at various deposition temperatures. The resulting films are characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM) for investigating the crystallinity and morphology, respectively. Optical properties are measured by ellipsometry and UV-vis on Si substrates and glass substrates, respectively, showing a high average refractive index of 2.14 and transmittance of more than 80% in visible light for the film deposited at 500°C. The potential of ZrO₂ thin films as gate dielectrics is verified by carrying out capacitance-voltage (C-V) and current-voltage (I-V) measurements. Dielectric constants are estimated from the accumulation capacitance, and found to be in the range 12 - 19 at an AC frequency of 1 MHz, and a leakage current of the order of 10⁻⁶ A cm⁻² at the applied field of 1 to 2 MV cm⁻¹ is measured for the films deposited at temperatures from 500 to 700°C. The low leakage current and high dielectric constant implies the good quality of the film, relevant for high-k applications. The hardness of the film ranges from 4.2 to 6.3 GPa for the 400 nm thick film, as determined by nano-indentation measurements. The optimum dielectric and hardness is found for the film deposited at 600°C, while the highest refractive index is found to be 2.14 for the film deposited at 500°C, due to higher density of the layers.

Magnetic materials synthesized on the nanometer-scale level are essential for several applications, such as spintronics and magnetologic. As a successful nanofabrication approach, focused electron beam-induced deposition (FEBID) stands out as a direct-write technique. FEBID uses an electron beam to locally induce a CVD process, avoiding the use of masks and resists. In this work, Fe–based nanostructures are synthesized on Si(100) by FEBID, starting from iron pentacarbonyl. A systematic variation of FEBID parameters is performed, to study their influence on the geometry and composition of the deposit. Based on the results, specific deposition conditions are suggested for magneto-logic applications and fabrication of large structures.

Among various multi-metal combinations, Au-Fe nanoalloys are envisaged as prospective materials for data storage applications. Here we report on the first successful achievement of Au-Fe nanoalloys using focused electron beam-induced deposition (FEBID), exploiting the possibility of directly writing nanostructures at nanometer resolution. Gaseous organometallic precursors are injected simultaneously into the deposition chamber to co-deposit Fe and Au within the same nanostructure. Fabricated nanostructures show a spatially uniform elemental ratio of iron to gold that can be tailored by experimental conditions.

Atomic layer deposition (ALD) using (MeCp)PtMe₃ and O₂ gas or O₂ plasma is a well-established technique for the deposition of thin films of Pt, but the potential of ALD to deposit platinum oxide (PtO_x) has not yet been systematically explored. This work demonstrates how PtO_x can be deposited by plasma-assisted (PA)-ALD in a temperature window from room temperature (RT) to 300 °C by controlling the O₂ plasma and (MeCp)PtMe₃ exposure. With increasing substrate temperature, the thermal stability of PtO_x decreases and the reducing activity of the precursor ligands increases. Therefore, longer O₂ plasma exposures and/or lower (MeCp)PtMe₃ exposures are required to obtain PtO_x at higher temperatures. Furthermore, it is established that, during the nucleation stage, PtO_x ALD starts by the formation of islands that grow and coalesce during the initial ∼40 cycles. Closed-layer thin films of PtO_x with an O/Pt ratio of 2.5 can be deposited at 100 °C with a minimal thickness of only ∼2 nm. It is also demonstrated that a conformality of ∼90% can be reached for PtO_x films in trenches with an aspect ratio of 9 when using optimized O₂ plasma and precursor exposure times.

Atomic layer deposition (ALD) offers nearly pinhole-free, conformal, and with good thickness control, metal oxide nanometric thin films required for next-generation memory devices. Here we report on the ALD of VO_x thin films grown at about 100°C from a vanadium tri-isopropoxide (VTIP) precursor, with water as the co-reactant, followed by their post-growth treatments, for potential applications in resistive switching (RS) devices. As-grown VO_x films are amorphous, and transform into polycrystalline layers upon annealing. Capacitor structures fabricated from amorphous VO_x films show current-voltage (I-V) characteristics, interesting for RS applications. Depending on the electroforming conditions, bipolar-type memory switching with a resistance ratio R_OFF/R_ON > 10³ is obtained, as well as a combination of memory and threshold switching. The latter is attractive for its highly non-linear I-V characteristics, which is attributed to the temperature-induced insulator-to-metal transition (IMT) in vanadium dioxide.

The resistive switching (RS) properties of a thin Al₂O₃ layer and TiO_x/Al₂O₃ bilayers integrated into TiN/metal oxide/Pt crossbar devices are investigated for future memristive device (ReRAM) applications. The oxide bilayer stack is realized in consecutive atomic layer deposition (ALD) processes at 300 °C without any post-annealing step. Stoichiometric Al₂O₃ and oxygen-deficient TiO_x thin films are grown from dimethylaluminum isopropoxide [DMAI: (CH₃)₂AlOCH(CH₃)₂] and tetrakis-dimethlyamido-titanium [TDMAT: Ti(N(CH₃)₂)₄], respectively, as the metal sources, and water as the oxygen source. High insulating characteristics are confirmed for as-grown amorphous Al₂O₃ films with a dielectric permittivity of 8.0 and disruptive field strength of about 7 MV cm⁻¹, whereas the oxygen-deficient TiO_x shows semiconducting behavior. The bipolar-type RS characteristics of TiN/TiO_x/Al₂O₃/Pt cells show a strong dependence on both oxide layer thicknesses. A stable OFF/ON state resistance ratio of about 10⁵ is obtained for the bilayer structure of 5 nm TiO_x and 3.7 nm Al₂O₃.