Lateral Dopant Diffusion Length Measurements Using Silicon Microring Resonators

An electro-optic device in silicon such as a photodetector and a modulator requires doping to realize desired junctions. Doping Si is typically done using ion-implantation or the thermal diffusion process. Both processes rely on high-temperature anneal to either activate or drive the dopant into the bulk. As diffusion of dopants is a thermally driven process, knowledge of actual diffusion lengths is essential for efficient device designs. Unlike other methods, we present an integrated-silicon-photonic-device-based lateral diffusion length characterization technique. A silicon microring resonator is used as a test device for the demonstration in a silicon-on-insulator substrate. Lateral diffusion lengths of 0.35 and 0.69 μm have been obtained for the drive-in temperatures of 950 °C and 1100 °C, respectively. We also present process simulation results to validate the experimental result.