Contact Resistivity of Highly Doped Si:P, Si:As, and Si:P:As Epi Layers for Source/Drain Epitaxy

In this work we report on the contact resistivity of highly doped epitaxial Si:P, Si:As and Si:P:As layers grown on 300 mm Si (100) substrates. The contact resistivity was extracted using a Multi-Ring Circular Transmission Line Model for a Ti based contacting scheme. Both selective and non-selective epitaxy processes were used and the effect of a post-epitaxy millisecond laser anneal was studied. Excellent contact resistivities down to ~2E-9 Ohm.cm2 could be found at high doping levels. A clear correlation was observed between the resistivity/contact resistivity and activation levels obtained by micro-Hall measurements. Although As doping is not bringing substantially lower contact resistivities compared to P doping, we observe a small beneficial effect. As also remains an attractive dopant for extension liners because of its lower diffusion constant.