Evidence for energy coupling from the Si–D vibration mode to the Si–Si and Si–O vibration modes at the SiO2/Si interface

In order to verify Van de Walle and Jackson’s theory on the isotope effect of the Si–H/D bonds resistant to hot-electron excitation [C. G. Van de Walle and W. B. Jackson, Appl. Phys. Lett., 69, 2441 (1996)], we measured the Si–H, Si–D, and other vibrational modes in the oxidized silicon wafers annealed in hydrogen and deuterium using Fourier-transform infrared (FTIR) spectrometry. Our FTIR data suggest that the frequency for the Si–D bending mode at the SiO2/Si interface is 490 cm−1. Our experimental data support Van de Walle and Jackson’s theory with some modification. Their theory is correct for the experiments of breaking Si–H/D bonds using scanning tunneling microscope where no oxide involves. In the SiO2/Si case, the de-excitation of the Si–D bond may be due to the energy coupling from the Si–D bending mode to two vibrational modes, i.e., Si–O TO mode and the Si–Si TO phonon mode. Van de Walle and Jackson only pointed out coupling to Si–Si TO phonon mode. The strongest coupling might happen between the Si–D mode and the Si–O TO mode. Therefore, the oxide may play a crucial role in energy dissipation of the Si–D bond in metal–oxide–semiconductor devices.