Micro Four-Point Probe with High Spatial Resolution for Ion Implantation and Ultra-Shallow Junction Characterization

Abstract

The application of micro four‐point probe technique in ion implantation non‐uniformity mapping and analysis is demonstrated in this work. The technique uses micron‐size probes with electrode pitch of 10 μm to achieve greatly enhanced spatial resolution of sheet resistance (Rs) measurements. Rs non‐uniformities due to uneven dopant distribution or activation can be mapped with improved accuracy, making it easier to detect implanter scanning problems, dose and charge control malfunctions and annealer related non‐uniformities. The technique’s superior performance in spatial resolution over conventional four‐point probe measurements is demonstrated by zero edge exclusion sheet resistance measurements at the wafer edge. In addition, the technique is used to investigate potential Rs variations between equivalent As+ and As2+ implants with the same effective energy. Finally, repeatability and reproducibility are investigated by making multiple measurements on a selected ULE implanted and annealed wafer.