Experimental evidence of Si-H bond energy variation at SiO₂-Si interface

The threshold energy barrier for hydrogen desorption from the SiO₂-Si interface has been assumed to be the Si-H bond energy with the value of 3.6 eV. Based on the uniform Si-H bond energy and diffusion-limited degradation, the time-dependent hot-carrier degradation of metal-oxide-semiconductor (MOS) devices has been described by the so-called power law. In this letter, by investigating the degradation of submicron n-channel MOS devices at various stress conditions and over a large time scale (0.01-10000 s), we present experimental evidence that contradicts the uniform bond energy theory and supports the bond energy variation theory proposed recently by Hess and co-workers [Appl. Phys. Lett. 75, 3147 (1999); Physica B 272, 527 (1999)]. We find that, instead of a constant power factor of n = 0.5 predicted by the uniform bond/diffusion-limited energy theory, n varies from ∼0.8 at the initial stress stage to ∼0.2 at the final stress stage consistent with the bond energy variation theory.