Probing doping conformality in fin shaped field effect transistor structures using resistors

For scaling complementary metal oxide semiconductor devices toward the ITRS goals for the 32 nm technology node and beyond, fin shaped field effect transistor (finFET)-based structures have shown immense potential due to their scalability by maintaining high drive current at scaled voltages and smaller gate dimensions. Due to the three-dimensional geometry of finFETs and the need to obtain identical lateral dopant profiles on the top and the sidewall of the fins, the classical doping strategies need to be reengineered as regular beam line implants would lead to large nonconformalities. The development of alternative doping processes such as plasma immersion doping requires the availability of methods to probe doping conformality. A methodology based on a dedicated resistor structure was developed, enabling the use of automated measurements to provide fast feedback on the degree of sidewall doping within different dies, across the wafer, and to study the wafer to wafer variation within a lot containing various splits. The methodology is validated by comparing the results with predictions based on a model describing the varying degree of conformality for beam line implants with different tilt angles.