Low energy electron induced X-ray emission spectrometry (LEXES) and secondary ion mass spectrometry (SIMS) sensitivity studies to ultra shallow arsenic implants

Abstract

CMOS device sensitivity to process variation is becoming increasingly important as devices are scaled down to smaller sizes. As a result, there is a growing demand for ion implantation and annealing tools to increase accuracy and repeatability. In parallel, there is also an increasing challenge on the metrology equipments to exhibit greater sensitivity to implant and annealing process variations.In this work we will focus on studying metrology sensitivity to NMOS junctions formed with ultra shallow arsenic implants. For the sensitivity to energy variation, the arsenic is implanted at energies from 1800eV to 2200eV by steps of ±20eV, ±50eV, ±200eV around arsenic 2keV at 1×1015ions/cm2. To study the sensitivity to dose variation, a second set of wafers were implanted with arsenic at 2keV with different doses ranging from 1×1014 to 2×1015ions/cm2.Low energy electron induced X-ray emission spectrometry (LEXES) is used to monitor dose sensitivity before and after annealing, secondary ion mass spectrometry (SIMS) is used to monitor the dose and profile sensitivity after anneal. AR-XPS was also used to monitor the native oxide thickness before and after annealing, and the oxidation state of arsenic.