Hydrogen Diffusion Study via Phosphorus Deactivation in n-Type Silicon

Abstract

Using the hydrogen deactivation of the phosphorus donor in silicon based Schottky diodes, the diffusion of hydrogen is investigated. Hydrogenation is performed by microwave plasma discharge involving an electron cyclotron resonance system (MW-ECR) to observe the variation in different operational parameters of diodes such as starting phosphorus concentration. The analysis of this variation has been carried out by capacitance–voltage (C–V) measurements to monitor the doping activation/deactivation profiles. From these profiles, hydrogen diffusion coefficients are calculated for different dopant concentrations. They clearly show that the rates and depth of deactivation were obtained in the low starting phosphorus-doped silicon sample. Our data are explained with the assumption that hydrogen diffusion is limited by trapping at the donor sites. In this case, H⁺ the dominant atomic species in the MW-ECR plasma reactor becomes H⁰ and prefers to gain an electron to become a negative ion H⁻ which interacts with the ionized atomic phosphorus P⁺ to form the PH complex. Therefore, no deeper hydrogen migration is detected for high starting phosphorus concentration. This is clarified by the build-up of a large amount of molecular hydrogen beneath the surface, which strongly hinders the diffusion of the hydrogen in the bulk. The values of hydrogen diffusion coefficient obtained in our study are in close agreement to those reported in literature.