Investigation of high-k dielectric stacks by C-AFM: Advantages, limitations, and possible applications

This chapter demonstrates the capability and the accuracy of tunneling atomic force microscopy (TUNA) and conductive atomic force microscopy (C-AFM) by comparing measurement results with data from conventional macroscopic current-voltage (I-V) methods. C-AFM/TUNA characterization complements conventional I-V measurements on metal-insulator-semiconductor (MIS) structures by accessing higher current densities. The chapter also addresses several limitations (e.g., parasitic capacitances in the pF range resulting from the cantilever of the probe and the probe holder and displacement current) which influence sensitivity and may be a possible obstacle for correct analysis of experimental data. The feasibility of these techniques and their ability to study phenomena at nanoscale is then demonstrated by several applications. The chapter further shows the great potential of C-AFM/TUNA technique to investigate changes in high-k film morphology. It presents an approach to evaluate the thickness of the thin interfacial SiO2 layer in high-k stacks and its change with the processing conditions.