Plasma doping junction depth measurement using Therma-Probe system

As semiconductor devices shrink in size, demands for the formation of ultra-shallow-junctions (USJ) are increasing. Pulsed plasma doping (P²LAD) is a method for forming USJs in semiconductor wafers. In this study, wafer biases between -200 V and -2.0 kV with BF₃ source gas were used to implant boron into 200-mm diameter silicon wafers. The boron dose was approximately 10¹⁵ B/cm², and wafers were annealed at 1,000°C using a rapid thermal annealer (RTA). In this work, a non-destructive in-line metrology tool (Therma-Probe™) was used for characterizing the junction depth of the plasma-doped samples after annealing. The Therma-Probe utilizes a pump-probe technique where the reflected signal of the probe beam is used to track the junction depth. The measured Therma-Probe signals were correlated with SIMS-based junction depth values.