Materials Science Forum Vol. 725

Abstract: An internally gettering bulk defect zone and a defect denuded zone of at least 5 µm below the wafer surface were generated by out-diffusion of interstitial oxygen during annealing at temperatures in the range 1075-1100 °C in argon atmosphere. The CZ silicon material used was optimized with respect to voids and contained a central OSF region and an outer Pv region. Due to co-doping of at least 3×10¹³ cm^-3 nitrogen, a laterally homogeneous bulk microdefect density was obtained which is independent of the temperature of the out-diffusion anneal. The internal getter created in this way efficiently getters nickel impurities as demonstrated in a getter test with 6.6×10¹¹ cm^-3 of intentional Ni contamination. In the central OSF region of the as-grown nitrogen co-doped wafers, the nuclei capable of generating OSFs also degrade the gate oxide integrity. Out-diffusion annealing at 1075-1100°C dissolves most of the defects capable of generating OSFs and it strongly improves the integrity of 5 nm gate oxides.

Abstract: Rapid imaging of the carrier density of n-type silicon (Si) was carried out at the rate of 2 s per point using a terahertz wave of 4.4 THz generated from a tunable terahertz source. Reflectance of 4.4 THz as a function of carrier density was calculated using a simple Drude model. The carrier densities obtained from the terahertz imaging were 1 × 10¹⁸ cm⁻³ and 3 × 10¹⁸ cm⁻³, respectively.

Abstract: There are two typical methods for silicon oxidation. One is pyrogenic oxidation using oxygen and hydrogen, the other is dry oxidation using oxygen. In this study various properties of these oxidation films were compared. The pyrogenic oxidation in turn could show better characteristic values in the all experiments. Furthermore, once dry oxidation was used even before gate oxidation, we found that dry oxidation made a source of defects generation at surface of the Si substrate.

Abstract: The effect of 2-MeV electron irradiation of Si_1-xGe_x S/D p-MOSFETs with different gate length and Ge concentration is studied. After electron irradiation, the maximum hole mobility decreases with increasing electron fluence for all gate lengths. In particular, after 5 x 10¹⁷e/cm² irradiation, the maximum hole mobility drastically decreases at short channel region for x = 0.3. Furthermore, a negative shift of the threshold voltage is clearly observed. These degradations can be explained both by the lattice defects and the stress relaxation in the Si channel created by atomic displacements.

Abstract: The influence of RTA pre-treatments on the morphology of oxygen precipitates in silicon wafers as deduced from haze getter tests was confirmed by FTIR and TEM investigations. Based on the results of the getter tests, the ratio between the density of plate-like and octahedral precipitates was calculated for RTA pre-treated silicon samples.

Abstract: Ge (100) thin film on Si (100) substrate is one of the new material technologies in the post scaling. In this study, we analyzed the stability of metal impurities of 4th row element around the interface of Ge (100) / Si (100) structure by using first-principles calculation. Considering the actual structure of the Ge thin film on Si (100) substrate, six calculation models were prepared. The calculated results showed that (1) Sc and Zn atoms are most stable at Ge surface, (2) Ti - Cr atoms are most stable in tensile plane-strained Si layer, (3) Mn - Cu atoms are most stable in compressive plane-strained Ge layer. These results indicate that the metal impurities concentrate on the strained region around the interface and/or Ge surface.

Abstract: This study is concerned with the effect of reduced Si₃N₄ coating during Si growth carried out by the directional solidification cast method. Three crystals were grown and compared in terms of cracking behavior and strain distribution. It was found, that the outer areas of the grown Si ingots exhibit much higher strain than the center pieces and this corresponds with the appearance of cracks in higher density in the outer edges of the crystals. It was also found that cracks mainly propagated in vertical direction and less in horizontal direction due to the temperature gradient during growth.

Abstract: Raman spectroscopy and photoluminescence were performed in order to understand the optical properties of nanocrystal Si in relation to quantum confinement effects. The nanocrystal Si (nc-Si) dots in the SiO2 layer were fabricated by the H2 plasma treatment and chemical vapour deposition followed by the oxidation of the nc-Si dots surface. The post-annealing was also performed to improve the crystalline quality of nc-Si at 1050 °C for 5 and 10 min. There is a good correlation of the quantum confinement effects between the results of Raman spectroscopy and photoluminescence. The Raman spectra from nc-Si were analysed using the model of Richter et al. As a result, the sizes of the nc-Si dots were consistent with those obtained by transmission electron microscopy and X-ray diffraction. Moreover, the compressive stress in the nc-Si dots were evaluated which was induced by the SiO2 surroundings.

Abstract: Si Nanowires (NWs) were studied by Raman microspectroscopy. The Raman spectrum of the NWs reveals important thermal effects, which broaden and shift the one phonon Raman bands. The low thermal conductivity of the NWs and the low thermal dissipation are responsible for the temperature enhancement in the NW under the excitation with the laser beam. We have modeled, using finite element methods, the interaction between the laser beam and the NWs. The Raman spectrum of Si NWs is interpreted in terms of the temperature induced by the laser beam excitation, in correlation with finite element methods (fem) for studying the interaction between the laser beam and the NWs.

Abstract: We investigated the spatial variation of energy band structure in a SrTiO₃ (001) bicrystal with the (100) 10° tilt boundary before and after the annealing process at 973 K under a vacuum of ~10^-7 Torr and after the subsequent forming process with electrical dielectric breakdown, using electron beam induced current (EBIC) method in the temperature range between 200 and 300K. Although the EBIC contrast at the tilt boundary was weak before and after the annealing, it became visible after the forming process and stronger as the observation temperature decreased to less than 260 K. It was found that the EBIC direction at the tilt boundary is opposite to that in the matrix, i.e. the single crystalline regions of both sides of the tilt boundary. In the matrix, the EBIC increased after the annealing and decreased again after the forming process. We propose energy band structures of the bicrystalline SrTiO₃ after the annealing and after the forming process.