Silicon doping profile measurement using terahertz time domain spectroscopy.

摘要

Doping profiles in silicon greatly determine electrical performances of microelectronic devices and are frequently engineered to manipulate device properties. To support engineering studies afterward, essential information is usually required for physically characterized doping profiles.;Secondary ion mass spectrometry (SIMS), spreading resistance profiling (SRP) and electrochemical capacitance voltage (ECV) profiling are mainstream techniques for now to measure doping profiles destructively. SIMS produces a chemical doping profile through the ion sputtering process and owns a better characterization resolution. ECV and SPR, on the other hand, gauge an electrical doping profile from the free carrier detection in microelectronic devices. The major discrepancy between chemical and electrical profiles is at heavily doped (>1020 atoms / cm3) regions. At the profile region over the solubility limit, inactive dopants induce a flat plateau and only being detected by electrical measurements. Destructive techniques are usually designed as stand-alone systems for the remote usage. For an in-situ process control purpose, non-contact approaches, such as non-contact capacitance-voltage (CV) and ellipsometry techniques, are currently under developing.;In this dissertation, novel terahertz time domain spectroscopy (THz-TDS) is adopted to achieve an electrical doping profile measurement in both destructive and non-contact manners. For this brand new application, everything has been studied from bottom-up. Firstly, the measurement uncertainty from the change of a bulk wafer thickness and the recognition of the doping profile dissimilarity were proven experimentally. The phosphorus refractive index from 1.2x10 15 cm-3 to 1.8x1020 cm-3 levels was then generated physically for the modeling of the complex THz transmission and its shift to the Drude Model prediction is explained two scientific mechanisms. Through the experimental demonstrated of the proactical degeneracy, relative strategies were proposed to shrink or break it. The doping profile measurement was finally performed by both methods. We conclude that THz-TDS can be designed as either an either in-situ or stand-alone system to estimate a doping profile in semiconductor materials.