Unveiling dopant concentration in boron doped Si ultrathin film: Enhanced analysis using time-dependent second harmonic generation

The evaluation of dopant concentration is essential in fabricating advanced field-effect transistors. In this study, we effectively leverage the unique characteristics of boron traps in the in-situ boron (B) doped Si ultrathin film (DSUTF) to examine the evolution of electric field through time-dependent second harmonic generation (TD-SHG). During the laser irradiation, internal photoemission (IPE) occurs in our system due to multiphoton absorption which enable the electron injected from Si to SiO₂. Our findings demonstrate that the presence of oxygen molecules weakens the electric field, resulting in a consequential reduction in SHG intensity. Therefore, we propose a model to elucidate the relationship between electrons and oxygen. Furthermore, we observe a robust monotonic correlation between the boron induced electric field and the dopant concentration. These results are consistent with first-principles calculation and capacitance-voltage measurement. Utilizing TD-SHG method for inspection of B dopant concentration in DSUTF provide a productive way for in-line inspection in semiconductor fabrication.