Plasma enhanced activation of ion implanted dopants

A plasma-enhanced annealing (PEA) process for activating ion implanted dopants at ultralow temperatures was investigated utilizing a radio frequency capacitively coupled plasma through argon. Silicon substrates implanted with either arsenic, phosphorus, or boron were subjected to argon ion bombardment at controlled ion energy and dose. Our study spanned a range of substrate-temperature conditions and compared results obtained isochronally with and without plasma enhancement (ion bombardment). The wafers were characterized by four-point probe, secondary-ion mass spectrometry, and Raman spectroscopy. The four-point probe measurements showed that PEA treatments reduced the sheet resistance of samples processed at temperatures below 600 °C. Raman spectroscopy of PEA samples had increased peak intensities at 520 cm−1 compared to thermal annealing (TA) samples suggesting enhanced recrystallization of the near surface in addition to the enhanced dopant activation. The data indicate that a PEA process can enable dopant activation and achieve low sheet resistance at reduced temperatures compared to the TA process. The low-temperature PEA process is expected to also exhibit a reduced amount of dopant in-diffusion.