A Novel Method for Simultaneous on Wafer Level Monitoring of Ion Implantation Energy and Dose

Semiconductor technology needs the control of processes on wafer level. For ion implanation control there are two well established methods, namely the photothermal response techniques on as-implanted product or monitor wafers and the determination of resistivity via sheet resistance measurement on as-implanted and annealed wafers. In fact, both methods are sensitive to implant dose but rather insensitive to implant energy. In particular the established methods are not capable to distinguish between effects of dose and energy. Especially in a high energy regime above 1 MeV it is of high interest to verify the implant energy on wafer level. This is in principle achievable by spreading resistance profiling (SRP) or secondary ion mass spectroscopy (SIMS) with the disadvantage of long feedback times, expensive processing and limited ability of resolution. It was shown that the wide frequency sweep used in the photothermal heterodyne equipment TWIN can be sensitive to the depth of damage profiles. In this study we present a developed energy and dose sensitive method based on a specially designed tool TWIN-SC4 produced by PVA Metrology&Plasma Solutions GmbH. Making use of the unique ability to vary the modulation frequency of the excitation laser enables inspection of different regions of the respective implant damage profiles. Consequently, we propose a method, combining measurements with two modulation frequencies and being sensitive to energy and dose which requires only a single as-implanted wafer.