Effects of Phosphorus Doping and Postgrowth Laser Annealing on the Structural, Electrical, and Chemical Properties of Phosphorus-Doped Silicon Films

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.