Heteroepitaxy and dry oxidation of silicon-germanium and silicon-germanium-carbon alloy thin films on silicon(100)

Heteroepitaxial silicon-germanium (Si1-xGex) alloys have found applications in Si-based technology. However, a good quality dielectric on Si1-xGex cannot be obtained by thermal oxidation. The goal of this study is to investigate the effect of carbon incorporation upon epitaxial growth and thermal oxidation of Si1-xGex alloys and its role on strain compensation in Si1-xGex alloys.;Both binary silicon-germanium (Si1-xGex) and ternary silicon-germanium-carbon (Si1-x-yGexCy) alloys with similar Si/Ge ratio are grown by Combined Ion and Molecular beam Deposition (CIMD) on P-type Si (100) substrate and compared. Prior to the epitaxial growth, a unique passivation technique is used to provide an ultra-clean and ultra-smooth Si (100) surface at low temperature. It involves a "modified RCA-type" pre-cleaning followed by HF/Methanol passivation and in situ thermal cleaning at a low temperature. As-deposited epitaxial films are then oxidized at three different temperatures by rapid thermal oxidation and furnace dry oxygen. The composition, structure, crystalline quality and surface morphology of binary and ternary alloys before and after oxidation are compared using a combination of Rutherford Backscattering Spectrometry (RBS) and ion channeling at 2.0 MeV, carbon Nuclear Resonance Analysis (NRA) at 4.3 MeV with 4He++ ions, Secondary Ion-Mass Spectrscopy (SIMS), Tapping Mode Atomic Force Microscopy (TMAFM), High-Resolution Transmission Electron Microscopy (HRTEM), and Fourier Transformation Infrared (FTIR) spectroscopy.;The study demonstrates that the hydroxide passivated Si (100) surface obtained by our passivation technique yields exceptionally smooth and ordered (1x1) Si (100) surfaces at room temperature, and ultra-smooth (2x1) ordering after in situ low temperature desorption.;We show that it is difficult to grow Si1-x-yGexC y films with quality comparable to binary Si1-xGex. Instead our results indicate a lower barrier to defect formation in Si 1-x-yGexCy than in Si1-xGex. We find that a growth temperature lower than 560°C is necessary to avoid the precipitation of a precursor phase to SiC in Si and in Si1-xGe x matrix, akin to Guinier Preston zones in the growth conditions used. The Si1-x-yGexCy films are considerably rougher than the Si1-xGex films of similar Si/Ge fractions. Roughness increases with increasing C fraction, indicating that the introduction of C lowers the barrier for the onset of Stranski-Krastanov type growth.;The importance of an independent and accurate measurement of the total and substitutional C fraction within the films is shown. This study also demonstrates the importance of using a combination of different analysis techniques for film characterization.;Dry oxidation of (Si1-xGex) and Si1-x-yGe xCy thin films leads to the formation of a conformal SiO 2 layer on the top surface, while Ge segregates towards the top surface and at the SiO2/Si1-xGex and SiO2/Si 1-x-yGexCy interfaces, in agreement with previous findings. However, we report the first time observation that dry oxidation rates in (Si1-xGex) decrease with increasing Ge fraction x for x > 0.20 and with increasing film minimum yield. Ion channeling analysis and strain measurements indicate that the incorporation of C rather than the amount of C itself affects the dry oxidation mechanism. Dry oxidation relaxes the previously strained (Si1-xGex) making the films more defective with a rougher surface. This is in contrast to the oxidation of Si (100) where oxidation always has a planarization effect. For relaxed Si1-xGex and defective Si1-x-yGexC y, dry oxidation does not have significant effect on the film crystalline quality and on the surface morphology.