The hydrogenation of MOS diode structures was studied by means of high-frequency capacitance profiling. The results indicated that the irradiation of 40nm Al-gated diodes with 0.8 to 1.4keV H ions soon established a time-independent near-surface H concentration which was directly proportional to the ion flux and the implantation depth and was inversely proportional to the H diffusivity. The results (table 56) indicated a diffusion activation energy of 0.58eV. The results of the modelling of low-field and high-field data suggested that the positive charge state was occupied for only 10% of the time. The time dependence of the H penetration indicated that H became immobilized at other sites in Si. The density of these secondary trapping sites was related to the dopant population. It was concluded that additional H could become trapped near to already-passivated dopant atoms.

In situ Measurements of Hydrogen Motion and Bonding in Silicon. C.H.Seager, R.A.Anderson, D.K.Brice: Journal of Applied Physics, 1990, 68[7], 3268-84

Table 56

Diffusivity of H in Si