Experimental studies of dose retention and activation in fin field-effect-transistor-based structures

With emerging three-dimensional device architectures for advanced silicon devices such as fin field-effect-transistors (FinFETs), new metrology challenges are faced to characterize dopants. The ratio of dopant concentration in the top surface and sidewalls of FinFETs may differ significantly, thereby influencing the performance of these devices. In this work, a methodology involving secondary ion mass spectrometry (SIMS) is presented to study the dose conformality in fins. However, SIMS is limited to probe the quantitative chemical dopant concentration (i.e., top/sidewall of fins). The fraction of the active dopant concentration determining the performance of FinFETs would still be unknown. Additionally, the concept based on SIMS is unable to provide information on the lateral junction depth. Thus, to obtain the unknown active dopant concentration and their spatial distribution, the authors extend their study by measuring the cross section of the fins with scanning spreading resistance microscopy and extracting the quantitative active carrier concentration in the fins.