An Electrical Failure Analysis (EFA) Flow to Quantitatively Identify Invisible Defect on Individual Transistor: Using the Characterization of Random Dopant Fluctuation (RDF) as an Example

An EFA flow is proposed to characterize a defective PMOS transistor that suffered abnormal high threshold voltage (Vth). Forward-Reverse (F-R) measurements observe asymmetric electrical characteristics in Id-Vg curves. Further body effect measurements confirm that the asymmetry symptoms are attributed to abnormal dopant concentration on well region, where RDF is suspected. Calculation shows that the well concentration of defective transistor is 1.8x of the well concentration of reference transistor. Technology Computer Aided Design (TCAD) and Simulation Program with Integrated Circuit Emphasis (SPICE) simulations all show that this 1.8x of well concentration will lead to a about 190 mV Vtsat increase, which explains 46% of the total Vtsat increase at T0. This study shows that RDF limits yield and performance on advanced IC technology. With the adopting of low implantation process and Fin structure, FinFET technology exhibits significant reduction on Vth variability and reaches unprecedented low value on minimum operating voltage (Vccmin).