Modeling of hydrogen diffusion in silicon crystals

One of the principal trends in modern silicon electronics is a tendency to use low-energy ion implantation of hydrogen from plasma sources to achieve the required parameters of silicon materials and devices. For analysis of hydrogen diffusion in silicon substrates a two-stream model with a corresponding system of diffusion equations is proposed. The model takes into account all the basic peculiarities of hydrogen behavior in silicon crystals: (i) the formation of bound hydrogen near the surface; (ii) the presence of “slow” and “fast” components of diffusion; (iii) interaction of diffusing hydrogen with defects and electrically active dopant atoms. It is supposed that atomized hydrogen in different charge states and/or nonequilibrium two-atom hydrogen molecules and “hydrogen atom–point defect” pairs govern “fast” and “slow” diffusion, respectively. Computer simulation using the proposed equations has shown very close coincidence of experimental and calculated hydrogen profiles for intrinsic silicon and allowed the parameters describing hydrogen diffusion to be extracted.