Phosphorus has low solubility in silicon, but nonequilibrium incorporation of phosphorus exhibits unusual high strain and low contact resistance for advanced Si-based metal-oxide-semiconductor field-effect transistors. Despite recent technological breakthroughs, the origin of tensile strain and electrical deactivation in P-doped Si films is not yet fully understood. Here, by using a combination of experiments and first-principles calculations, we investigate the effect of nonequilibrium phosphorus incorporation into Si lattices and subsequent annealing on structural, electrical, and bonding properties of P-doped Si films. Quantitative structural analyses reveal that the high tensile strain is generated by the incorporation of P into Si substitutional sites irrespective of the distribution of P atoms. More importantly, we found that advanced postgrowth annealing lead to significantly enhanced electrical properties while keeping the same physical states without loss of induced strain. To explore the reason for improved performances, we conducted the comprehensive theoretical calculations that present the contributions of dopant incorporation and vacancy formation to structural, chemical, and electrical properties, thereby providing atomic insights into the underlying physical mechanism of the electrical deactivation. Our findings indicate that the tensile strain can be controlled by manipulating the number of substitutionally incorporated P atoms, and electrical properties may be enhanced by reducing the vacancy concentration using advanced postannealing processes or low temperature growth conditions.

In situ phosphorus‐doped epitaxial silicon films have attracted significant attention as source and drain materials because low specific contact resistivities have been achieved on such films by increasing the active carrier concentration using millisecond laser annealing. However, the active phosphorus concentration that can be achieved using millisecond laser annealing is much less than the incorporated concentration. To increase the activation efficiency, nanosecond laser annealing with a dwell time ≈104 times shorter than that of millisecond laser annealing is investigated and the diffusion, strain, microstructure, and electrical properties of single‐ and multipulse nanosecond laser‐annealed samples are examined. The melting depth simulation classifies the energy density regions and explains the limited diffusion in nanosecond laser annealing. After multipulse nanosecond laser annealing, more phosphorus is activated without diffusion than by millisecond laser annealing. Moreover, almost all the incorporated phosphorus atoms are activated by the nanosecond laser, which melts in situ phosphorus‐doped epitaxial silicon films without major strain loss. The increased active carrier concentration presents an opportunity to achieve low contact resistivity characteristics.

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Highly phosphorus-doped silicon source/drains are investigated to improve the performance of N-type metal-oxide-semiconductor field-effect transistors by decreasing their resistance and imparting strain to their channels. To find effective high temperature annealing for the activation of phosphorus in the source/drains, we apply single- and multi-pulse nanosecond laser annealing on highly phosphorus-doped silicon. The microstructure, strain, and electrical properties of highly phosphorus-doped silicon before and after laser annealing are analyzed. Our results demonstrate that the defects in both the recrystallized silicon and the end of range are decreased with 600 mJ cm−2 10-pulse annealing while considerable increase in phosphorus activation is achieved.