Infrared spectroscopy is used to compare the Si/SiO2 interfaces created by thermal oxidation of a standard Si(100) substrate and of an ordered, (1×1) Si(100) substrate. The thermal oxides (approximately 25 Å) examined in this study are etched in dilute hydrofluoric acid and the resulting films analyzed spectroscopically. The behavior of the dominant optical phonon modes as a function of film thickness provides strong evidence that the ordered Si(100) substrate provides a template for an Si/SiO2 interface with a higher degree of homogeneity in the Si–O bonding environment of the intervening substoichiometric SiOx layer than does the standard Si(100) substrate.
Articles you may be interested inExperimental study of electron-and ion-beam properties on the BNL electron-beam ion source and comparison with theoretical models Rev. Sci. Instrum. 77, 03A910 (2006); 10.1063/1.2149377 Theoretical and experimental study of large aperture low energy ebeam source for semiconductor processing Ion beam oxidation (lBO) is a low temperature growth technique where a directional low energy (,;;; 1 keY) ion beam introduces the oxygen into the substrate and athermally activates the chemical reaction leading to the oxide growth. In this work, IBO of Si, Ge, Si l _ xGe x was investigated experimentally as a function of ion energy from 100 eV to 1 keY. The results show a strong dependence of the materials properties such as phase formation, stoichiometry, and thickness upon the ion energy. To investigate the kinetics of IBO and to account for the observed relationship between ion energy and films properties, three models were successively developed taking progressively into account: (1) ion implantation and sputtering (model IS), (2) replacement and relocation events, i.e., ion beam mixing effects (model ISR) and (3) oxygen diffusion (model ISRD). The simulation results show that the model IS based only on implantation and sputtering cannot explain the oxide thickness dependence upon ion energy observed experimentally, but can give qualitative information on the phases formed by IBO. Ion beam mixing effects in the model ISR lead to spatial redistribution of the elements in compound targets and account for the evolution of stoichiometry as a function of depth. Thermal and point defect mediated diffusion of free oxygen and the strong driving force for oxidation must be considered to account for the observed thicknesses, sharp interfaces and kinetics of IBO growth in three stages.
Articles you may be interested inWet oxidation of nitride layer implanted with low-energy Si ions for improved oxide-nitride-oxide memory stacks Appl. Phys. Lett. 90, 263513 (2007); 10.1063/1.2752769Room-temperature growth of crystalline indium tin oxide films on glass using low-energy oxygen-ionbeam assisted deposition
Wafer bonding can be substituted for heteroepitaxy when manufacturing specific heterojunction-based devices. Devices manufactured using wafer bonding include multijunction solar cells, integrated sensors, heterogeneously integrated photonic devices on Si (such as high-performance laser diodes), Mach-Zehnder modulators, photodetectors, optical filters, and surface acoustic wave devices. In these devices, creating heterointerfaces between different semiconductors with heavily mismatched lattice constants and/or significant thermal expansion mismatch presents significant challenges for heteroepitaxial growth. High costs and poor yields in heavily mismatched heteroepitaxy can be addressed by wafer bonding in these optoelectronic devices and sensors, including the LiTaO3/Si and LiTaO3/SiO2 heterostructures. In the present work, heterostructure formation between piezoelectric LiTaO3 (100) and Si (100) and α-quartz SiO2 (100) is investigated via wafer bonding. Direct bonding is selected instead of heteroepitaxy due to a significant thermal expansion mismatch between LiTaO3 and Si-based materials. The coefficient of thermal expansion (CTE) of LiTaO3 is 18.3 × 10−6/K. This is 1 order of magnitude larger than the CTE for Si, 2.6–2.77 × 10−6/K and 25–30 times larger than the CTE for fused SiO2 and quartz (which ranges 0.54–0.76 × 10−6/K). Thus, even at 200 °C, a 4 in. LiTaO3/Si bonded pair would delaminate with LiTaO3 expanding 300 μm in length while Si would expand only by 40 μm. Therefore, direct wafer bonding of LiTaO3/Si and LiTaO3/SiO2 is investigated with low temperature (T < 500 K) Nano-Bonding™, which uses surface energy engineering (SEE). SEE is guided by fast, high statistics surface energy measurements using three liquid contact angle analysis, the van Oss/van Oss–Chaudhury–Good theory, and a new, fast Drop Reflection Operative Program analysis algorithm. Bonding hydrophobic LiTaO3 to hydrophilic Si or SiO2 is found to be more effective than hydrophilic LiTaO3 to hydrophobic Si or SiO2 temperatures for processing LiTaO3 are limited by thermal decomposition LiTaO3 into Ta2O5 at T ≥ 180 °C due to Li out-diffusion as much as by LiTaO3 fractures due to thermal mismatch.
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