The problems in the thinning of Oxide/Nitride/Oxide (ONO) films for memory capacitors of DRAM are reviewed. There are two key points in forming the ONO films of excellent leakage current characteristics, that is, the improvement of the surface before nitride deposition and of the nitride deposition parameter. These points were investigated by using XPS and RBS. The native oxide layer grows up at the surface of poly-crystalline silicon film playing a roll as an electrode for the memory capacitor. This layer is changed into oxynitride by NH3 annealing, and silicon-rich transition layer formed in the early stage of nitride deposition disappears as a quantity of nitrogen involved in the native oxide film saturates. The resistance of nitride film in thermal oxidation is improved in a nitrogen-rich film. The composition of nitride film depends not only on the flow rate of NH3 and SiH2Cl2 but also on a deposition temperature. Nitride films deposited at the temperatures near 750°C showed good performance.
The Kelvin probe method has become very common in the study of the atmospheric corrosion since it was suggested that the method can be applied to the surface potential measurement as a non contacting method. The accuracy of the method is insufficient in detecting and discussing the corrosion initiation from the inclusions less than few microns. We applied the Kelvin force method (KFM) which is one of the AFM methods for the study of corrosion. First we examined the effect of the gap between the tip and specimen and found that the gap of less than 20 nm does not affect the potential distribution. The potential distribution of iron corroded in air was measured accurately. The irregularity of potential was caused by the small dust particles or scratches that become the nucleation sites of corrosion. A series of AFM observations show the atmospheric corrosion proceeded by micro-galvanic cell.
The effect of residual elements and micro allyed elements on high temperature oxidation of carbon steels and stainless steels were introduced. The mechanism of the effect of these elements were also introduced. Furthermore, it was also introduced that new high temperature oxidation resistant stainless steels were developed and applied commercially by controlling these elements.
X-ray photoelectron spectroscopy (XPS) has been used to investigate the Si(100) surfaces exposed to 02 at room temperature and subsequently heated to various temperatures ranging from 200°C to 800°C. Each 01s spectrum observed was deconvoluted into two Gaussian curves with peaks at (531.8 ± 0.3) eV and (533.6 ± 0.3) eV. The surface density of high binding energy component (533.6 ± 0.3) eV decreased with increasing temperature up to 400°C. On the other hand, the surface density of low binding energy component (531.8 ± 0.3) eV increased with increasing temperature up to 400°C. Furthermore high binding energy component increased as a result of heating at a high temperature above 400°C, and all of the oxygen adsorbed were removed from the surface by heating at temperatures above 750°C. The change of the surface density of the two components with temperature was discussed in relation to the bonding states of oxygen to silicon surfaces.
We have calculated the rates of the erosion reaction by the steady-state approximation to confirm its isotope effect at C:H film surfaces observed experimentally. The isotope effect is due to the difference between activation energies of C-H and C-D bond breakings along the reaction coordinate. Calculated results are in good agreement with experimental ones.
A study has been made of the depth profiling of carbon-implanted titanium by AES combined with argon sputtering. Implantation of12C+ ions is performed at doses of 5 × 1017, 1 × 1018 and 1.5 × 1018 ions/cm2 at an energy of 100 keV. Variation of peak-to-peak intensities of carbon KLL AES spectra with sputtering time is considered to correspond to the depth distribution of atomic concentration of carbon atoms. The variation shows a Gaussian distribution predicted by the range theory at the dose of 5 x 1017 ions/cm2, and trapezoidal one at the dose of 1 x 1018 ions/cm>2 or more. XPS studies reveal, however, that the depth distribution of carbon atom concentration is Gaussian at the dose of 1 x 1018 ions/cm2. Observed titanium LMM AES intensity of TiC mostly agrees with the value calculated by a matrix correction of that of titanium without chemical effect. On the other hand, carbon KLL intensity of TiC is about 2.6 times as large as the value calculated from that of glass-like carbon. The results suggest that the change in intensity of carbon KLL AES spectrum according to the chemical bonding states of carbon atoms makes the depth distribution of carbon atoms a trapezoidal shape at high doses. In conclusion, it is said that the depth distribution of carbon atoms is Gaussian as predicted by the range theory even at very high doses over 1 x 1018 ions/cm2. Therefore, the composition depth profiling of titanium implanted with carbon ions at high doses by AES alone is difficult because of the chemical effect of carbon KLL transition.
The mechanism of ESD (electron stimulated desorptions) has been experimentally examined for organic molecules on Al and Au by irradiating the surfaces with middle energy (0.5 to 3.0 keV) electron beams. ESD of neutrally desorbed molecules has been observed in a UHV chamber installed with a SEM/AES and a 0-mass spectrometer. ESD molecules from adsorbed polystyrene or rosin are measured from a practical view point. It is found that ESD efficiency depends upon the incident electron energy and molecular species, and there are three different ESD desorption mechanisms, i.e., direct and indirect ESD mechanisms and electron induced thermal desorption. It is concluded that the present method of ESD using middle energy electron beams is of practical use to analyze the surface organic contaminants in submicron areas.
An investigation of the deposition of a-SiC:H films in a remote H plasma environment using tetramethylsilane, hexamethyldisilane and tetrakis(trimethylsilyl)silane was carried out. All these monomers produce a-SiC:H films in the presence of atomic hydrogen. The stoichiometry and Eopt of the films deposited are found to depend on the substrate temperature. All the films deposited show photoluminescence (PL) when excited with 325 nm laser light. Films deposited at room temperature shows a blue-white PL. The PL intensity drops with an increase of substrate temperature used for the deposition. Further a red shift of the PL is observed with an increase of substrate temperature. In addition, a reaction scheme for the film formation is modeled through the generation of Me2Si=CH2 precursor.