Paper EM+PS-TuM1
Calibration of Capacitance Force Microscopy using Micro-scale Gold Dots

Tuesday, October 29, 2013, 8:00 am, Room 101 B

Capacitance force microscopy (CFM) is a variant of atomic force microscopy (AFM) and a powerful tool in characterization of metal-oxide-semiconductor capacitors (MOSCAPs). A high accuracy CFM system can be built by modifying a commercially available AFM, connecting the tip and sample to capacitance bridge of tunable frequency. The electric field distribution and, as a result, minority carriers’ response to the applied bias strongly depend on the contact area between the gate and oxide. Furthermore, the frequency dependence of the capacitance-voltage measurement (C-V) is a function of the electrode size due to the radial diffusion of minority carriers near the periphery of the electrode as the dimension shrinks to the size of AFM tips. Therefore, contact area between the tip and sample is a crucial factor in CFM measurements. An experimental method is required to determine the effect of contact area on the shape and frequency-dependence of C-V curves measured by CFM. Scanning capacitance calibration samples are being fabricated with gold dots of diameters ranging from 2 to 600 μm on heavily doped silicon with 100 nm thick SiO₂ grown on top. The capacitance of resulting Au/SiO₂/Si⁺ stacks with a 90000x range of area will be measured both by a conventional probe station (Agilent B-1500) and a CFM system (Veeco Multimode^® connected to an AH 2700A capacitance bridge). After calibration, second set of samples including gold dots of similar size on Al₂O₃ layers, grown by atomic layer deposition (ALD), on GaN substrates will be characterized by both the probe station and CFM systems.