Demonstration of high-resolution doping profile mapping using terahertz time domain spectroscopy with electrochemical anodization

In the previous work we presented results demonstrating the ability of transmission mode terahertz time domain spectroscopy (THz-TDS) to detect doping profile differences and deviations in silicon. Here we report follow up work demonstrating doping profile measurement by first precisely removing a thin layer (currently ∼ 20 nm) from the junction by anodization followed by selective oxide etching. The anodization-etching step is followed by measuring the terahertz transmission using THz-TDS. The anodization and terahertz measurement steps are then alternated. The doping profile can then be reconstructed using the resultant dataset. In this work we share results obtained on phosphorus doped silicon wafers. We find good agreement between the measured transmitted terahertz spectra and the simulated terahertz spectra for all etching cycles when the doping profile used in the simulations agrees with SIMS analysis. We conclude that anodization combined with THz-TDS can potentially be a high resolution destructive doping profile mapping method.