Si3H8 Based Epitaxy of Biaxially Stressed Silicon Films Doped with Carbon and Arsenic for Cmos Applications

Abstract

AbstractArsenic doped Si:C films were grown epitaxially using Silcore® (Si3H8), methylsilane and arsine as source gases with growth rates up to 90 nm/min at 550°C. We observed a strong dependence of C and As incorporation on growth rate, caused by a growth rate dependent surface segregation behavior of C and As. High-resolution x-ray diffraction measurements of the epi layers reveal a perpendicular lattice constant as low as 5.323 Å. This corresponds to a biaxial stress of more than 2 GPa. Grazing exit (224) x-ray diffraction reciprocal space maps show the full tetragonal strain expected from the C content, suggesting that no relaxation of the films has occurred. Spectroscopic ellipsometry (SE) spectra were acquired in the 0.74 to 6.6 eV photon energy range. For intrinsic Si:C alloys, the E1 critical point shows the expected blueshift due to the alloying. For Si:C:As, a strong broadening of the E1 and E2 transitions exists, due to scattering of Bloch electrons in the crystal by As atoms. Additionally, free carrier effects lead to a decrease (increase) of the real (imaginary) part of the dielectric function in the near-infrared, consistent with a free carrier concentration in excess of 5×1020 cm-3. Transmission electron microscopy (TEM) of As doped Si:C films confirmed single-crystal epitaxial growth.