Search

Ta2O5-based composite thin films formed by metalorganic decomposition have been investigated with respect to their dielectric properties. The dielectric and insulating properties of composite (1−x)Ta2O5−xTiO2 and (1−x)Ta2O5−xWO3 thin films are found to be improved compared to those of pure Ta2O5 thin films. In particular, thin films with x=0.08 composition of additive TiO2 or WO3 to Ta2O5 exhibited superior dielectric and insulating properties. The maximum dielectric constant and charge storage density of composite films are about 20 and 53.6 fC/μm2, respectively, higher than those of pure Ta2O5 films (about 13 and 34.5 fC/μm2). The temperature coefficient of the dielectric constant of composite films dramatically decreases from 65 ppm/°C for pure Ta2O5 to less than 11 ppm/°C. The leakage current density of composite films is lower than 1×10−9 A/cm2 up to an applied electric field of 3 MV/cm. The dominant conduction is Poole–Frenkel conduction in the films according to the measurement temperature dependen...

The physical properties and charge trapping behavior of rapid thermal N2O-oxynitrided (RTON) and rapid thermal NH3-nitrided (RTN) ultrathin SiO2 films have been investigated. The results of secondary-ion-mass spectrometry and Fourier transform infrared reflection measurements indicate that although nitrogen atoms are incorporated into the RTON and RTN films, only the RTN film shows a large number of NH bonds in the bulk SiO2. Using an analytical model, the number of oxide charge traps, the capture cross section, and the charge trap generation rate for the RTON and RTN SiO2 films were determined. Under high-field stress, the RTON SiO2 film has a much smaller number of electron and hole traps and a lower electron trap generation rate, resulting in a larger charge-to-breakdown QBD value compared to that of pure SiO2 film. In contrast, a large number of electron traps which originate from NH and SiH bonds is present in the RTN film. The differences in the charge trapping phenomena and oxide breakdown characte...

The interface trap density of states Dit of ultrathin SiO2 film has been investigated as a function of process variables. The process parameters used were oxidation temperature (1000–1200 °C), oxide thickness (4–10 nm), and annealing condition, including ambient (deuterium, argon, and in vacuum), temperature (500 and 900 °C), and time (10–120 s). Analysis of as‐grown SiO2 films showed that the Dit decreases with increasing oxidation temperature and/or oxide thickness. With annealing in argon or in vacuum at 900 °C, the Dit decreases exponentially at the initial stage, then starts to increase linearly with increasing time. Similar behavior was observed for 900 °C deuterium annealing. Deuterium annealing at 500 °C was more effective in the reduction of the Dit, whereas argon annealing at the same temperature did not affect the density at all. A possible model for annealing kinetics is proposed to explain the experimental results.

SiO2/Ge nanocrystal/SiO2 structures have been fabricated by deposition of Ge film on a SiO2 layer and subsequent oxidation of the structure at a temperature between 800 °C and 1000 °C. Secondary ion mass spectrometry results indicate that the Ge precipitates into the bulk SiO2 at a density of 1×1012 cm−2. Raman spectra show a sharp peak at 300 cm−1 for the nanocrystallized Ge. The nanocrystal diameter is determined to be 5 nm on average. In the metal–insulator–silicon structure, electron storage occurs in the SiO2/Ge/SiO2 potential well via electron tunneling into the oxide film. Capacitance-voltage measurements indicate that flatband voltage (VFB) shifts to 0.91 V after the electron injection. The VFB shift is attributed to the charge storing for a single electron per potential well.

The synchrotron radiation durability of SiOxNy films (about 10 nm) formed by rapid thermal processing in a N2O ambient was studied. No significant difference between the flat‐band voltage of SiOxNy‐metal‐oxide semiconductors (MOS) capacitors patterned by synchrotron radiation lithography (SR‐MOS) and that of capacitors patterned by conventional optical lithography (OP‐MOS) was observed. The midgap interface state density of the SR‐MOS was approximately one order of magnitude larger than that of the OP‐MOS. The differences between the SR‐MOS and the OP‐MOS were nearly independent of the SR dose in the range of 540–2700 mJ/cm2, and were eliminated by annealing in a hydrogen ambient at 400 °C for 30 min.

High‐resolution transmission electron microscopy (HRTEM) with 0.3‐nm resolution, scanning transmission electron microscopy using transmission electron diffraction and electron energy loss spectroscopy (EELS) with 0.7‐nm resolution have been employed to characterize the SiO2/Si(100) interface structure of ultrathin (5–12 nm) SiO2 films grown by rapid thermal oxidation (RTO) at 1100 °C. In the HRTEM image, the SiO2/Si(100) interface of ultrathin SiO2 film grown by RTO in dry oxygen ambient seems to be uniform. The TED patterns also showed that the atomic structure abruptly changes from the crystalline silicon to amorphous oxide network across the SiO2/Si interface. The EELS plasmon‐loss spectra showed that for 5‐nm‐thick SiO2 an intermediate oxide composition indicating a plasmon energy between Si (17.0 eV) and SiO2 (22.5 eV) is present, whereas it disappears for 12‐nm‐thick SiO2 film.

Hard hydrogenated amorphous carbon (a‐C:H) films were coated on amorphous silicon photoreceptors by the plasma decomposition of acetylene (C2H2). This overlayer proved to be a much better protective layer for the adsorption of external species compared to an a‐SiNx or a‐Si1−xCx overcoating layer, and the image degradation induced by such adsorption was considerably reduced. The highly protective properties were attributed to the hydrophobic nature of C–Hn (n=1–3) and C–C bonds contained in the a‐C:H film. The optical properties of the a‐C:H films are also described.