Deposition Rate Stability Research Articles

Preparation of YBCO thin film by MOCVD method using new liquid metal organic precursors

New low melting point yttrium, barium, and copper complexes were synthesized for metalorganic chemical vapor deposition (MOCVD), tris(2,2,6,6-tetramethyl-3,5-octandionato)yttrium (Y(TMOD)/sub 3/), Ba(TMOD)/sub 2/, and bis(6-ethyl-2,2-dimethyl-3,5-octanedionato)copper (Cu(EDMOD)/sub 2/). The melting point of Y(TMOD)/sub 3/, 95/spl deg/C, is 80/spl deg/C lower than that of the conventional tris(dipivalaylmethanato)yttrium (Y(DPM)/sub 3/). The melting point of Cu(EDMOD)/sub 2/ is 78/spl deg/C, which is 120/spl deg/C lower than that of Cu(DPM)/sub 2/. For fabrication of YBa/sub 2/Cu/sub 3/O/sub y-/spl delta// thin films, these complexes were used in the liquid state where a stable deposition rate could be obtained; the Y(TMOD)/sub 3/ and the Cu(EDMOD)/sub 2/ were heated at 105/spl deg/C and 90/spl deg/C, respectively, and the mixture of Ba(DPM)/sub 2/ and Ba(TIMOD)/sub 2/ in the ratio of 4 to 1 was used at 215/spl deg/C. Single crystal STO(100) was used as a substrate. Substrate temperature was 800/spl deg/C. Thin films, of thickness 200 nm, were obtained. The XRD patterns of all the samples showed the preferred orientation of the c-axis normal to the substrate surface. The superconductivity was confirmed at 78 K.

Control of the structure and properties of aluminum oxide coatings deposited by pulsed magnetron sputtering

Alumina coatings offer the potential to protect metallic components operating in hostile corrosive, or oxidative environments. Until recently, though, the high rate deposition of fully dense, defect-free oxide coatings has proved extremely difficult. Oxide coatings can be produced by the reactive direct current (dc) sputtering of a metallic target in an oxygen atmosphere, or by radio frequency sputtering of an oxide target. The latter process results in very low deposition rates and is difficult to scale up for commercial applications. Reactive dc sputtering of highly insulating materials, such as alumina, is also problematic. The build up of an insulating layer on the surface of the target causes arcing. Arc events affect the stability of the deposition process and can adversely effect the structure and properties of the growing film. However, a new technique, pulsed magnetron sputtering, has been developed which significantly increases the viability of producing this type of material. It has been shown that pulsing the magnetron discharge in the 10–200 kHz range prevents the formation of arcs at the target. The process is stable and high deposition rates can be achieved. This technique has, therefore, been used to deposit coatings with compositions ranging from pure aluminum to stoichiometric Al2O3. The coatings were characterized by scanning and transmission electron microscopy, x-ray diffraction, four-point probe, and nano-indentation techniques. The observed variations in structure and properties are considered in terms of the composition of the coatings and expressed schematically in the form of a novel structure zone model.

Hydrogen Chloride Effects on the CVD of Silicon Carbide from Methyltrichlorosilane

A comprehensive experimental investigation of the effects of hydrogen chloride concentration on the deposition rate and stoichiometry of SiC films produced through thermal decomposition of methyltrichlorosilane (MTS, CH3SiCl3) is carried out in a gravimetric hot wall reactor of tubular geometry. The study is conducted under subambient pressures and in the temperature range 1173–1473 K. Deposition rate measurements are carried out with HCl added to the MTS/H2 feed mixture to simulate the depletion of gas phase deposition precursors and the formation of HCl along the length of the reactor. The effects of HCl addition are studied at different locations in the CVD reactor for reactive mixture flow rates in the range 200–400 cm3/min, and 1:10 or 1:20 MTS/H2 ratio. Very strong effects of HCl on the deposition process are suggested by the experimental results. It is also found that for certain values of the other operating parameters of the process, two stable deposition rates, differing by more than an order of magnitude, may be encountered at the same value of HCl concentration. A simple expression is formulated for the deposition rate of SiC in terms of the gas phase concentrations of MTS and HCl, and the temperature. This expression is employed in a simple plug-flow reactor model, and the predicted results are compared to the experimental measurements of deposition rate and HCl concentration levels needed to stop the deposition of SiC.

Fabrication and characteristics of rugate filters deposited by the TSH reactive sputtering method

Theoretical investigations on rugate filters have recently received much attention. For the most efficient use of the rugate filters, the deposition processes such as EB coevaporation, reactive ion beam assisted deposition and chemical vapor deposition methods, have been investigated as the most importance to achieve our objective. However, since periodic rugate filters manufactured in these manners require sophisticated and precise control of the process, they cannot sufficiently offer either the required stable deposition rate, wide variation of refractive index, or a particularly long-time constant deposition process. In this experiment, the two-stage high-rate reactive sputtering method, called TSH reactive sputtering, is used to fabricate such rugate filters. Their spectral performance, elemental composition ratio, and cross-section morphology have been investigated.

Special speleothems in cement-grouting tunnels and their implications of the atmospheric CO 2 sink

Based on the analyses and comparisons of water chemistry, stable carbon isotopes and deposition rates of speleothems, the authors found that there are two kinds of speleothems in the tunnels at the Wujiangdu Dam site, Guizhou, China, namely the CO2-outgassing type and the CO2-absorbing type. The former is natural, as observed in general karst caves, and the product of karst processes under natural conditions. The latter, however, is special, resulting from the carbonation of a cement-grouting curtain and concrete. Due to the quick absorption of CO2 from the surrounding atmosphere, evidenced by the low CO2 content in the air and the high deposition rate of speleothems (as high as 10 cm/a) in the tunnels, the contribution of the carbonation process to the sink of CO2 in the atmosphere is important (in the order of magnitude of 108 tons c/a) and should be taken into consideration in the study of the global carbon cycle because of the use of cement on a worldwide scale.

New Liquid Precursors of Yttrium and Neodymium for Metalorganic Chemical Vapor Deposition

New precursors, 2,2,6,6-tetramethyl-3,5-octanedionato (TMOD) yttrium and neodymium complexes were synthesized for metalorganic chemical vapor deposition (MOCVD). The melting points of the TMOD complexes were much lower than those of the conventional dipivaloylmethanato (DPM) complexes. These complexes can be used in the liquid state where a stable deposition rate can be obtained. It was confirmed that the oxide thin films, Y2O3 and Nd2O3, could be fabricated by an MOCVD method using these complexes.

Deposition of stable, low κ and high deposition rate SiF 4-doped TEOS fluorinated silicon dioxide (SiOF) films

Fluorine doped silicon dioxide (SiOF) is recognized as a potential intermetal dielectric (IMD) film for sub-half micron devices, due to its low dielectric constant ( κ) and good gap-fill capabilities. For the first time, physically stable and high deposition rate (1550 nm/min) SiOF films were deposited using a parallel-plate plasma CVD–single wafer DxZ reactor, involving SiF 4/TEOS/O 2 chemistry. The analytical results indicate that these SiOF films, having a F concentration up to 3.0%, contain only Si–F bonding, do not absorb moisture and show stable dielectric constants. A typical highly stable SiOF film has F concentration and dielectric constant values of 2.4% and 3.5, respectively. This film is thermally stable up to 600°C and can be used as a low cost cap layer for HDP–CVD oxides and other low κ spin-on-glass materials, as well as an IMD layer for damascene applications.

PC-based digital apparatus with temperature compensation for measurement of thin films during deposition

We present an apparatus for controlling the deposition of thin films. The apparatus is based on a quartz resonator whose frequency is controlled digitally by a computer. Temperature variations of the quartz during the evaporation process, attributed to the exothermic heat of condensation and radiation heating from the evaporation source, are compensated. A very stable deposition rate and a good film thickness evaluation are obtained.

Rugate filter fabrication using neutral cluster beam deposition

Neutral cluster beam deposition (NCBD) is shown to be memethod directly applicable to rugate filter fabrication. NCBD provides the necesarry stable low deposition rates and control (±0.1 Å s −1) required for thin rugate layers (typically 80 Å). This paper specifically describes use of NCBD for co-evaporation of ZnS and BaF 2 producing digtal rugate filter structures with a range of effective refractive indices. Automated process control aspects to achieve the necessary tolerances for rugates will be described. This is demonstrated via the excellent agreement between theoretical and experimental rugate performance. Process scalability and production issues are addressed.