Profiling of ultrashallow junctions

Abstract

Ultrashallow profiles challenge the capabilities of all characterization techniques. In this article, three diagnostic techniques are tested, secondary ion mass spectrometry (SIMS), capacitance–voltage (C–V) profiling and spreading resistance analysis (SRA). SIMS is used to measure the impurity concentration profiles, C–V is used to measure carrier concentration profiles directly and SRA is used to measure resistivity profiles, from which carrier concentrations can be derived. Both SIMS and SRA are calibrated techniques that relate the measured parameter to concentration or resistivity via calibration standards. C–V derives the carrier concentration directly through a mathematical model and calculation. Some of the assumptions, procedures, and limitations of these three techniques for ultrashallow profiles are reviewed and discussed. For this article these diagnostic techniques were used to examine six wafers that had been plasma doped followed by a rapid thermal anneal and three wafers that had been beamline implemented followed by a soak anneal.