Paper MS+AS-TuM11
Characterization of Electrical Properties of Si and GaN Devices using Scanning Microwave Impedance Microscopy (sMIM) and Nano-scale Capacitance-voltage Curves

Tuesday, November 8, 2016, 11:20 am, Room 103A

The use of Atomic Force Microscopy (AFM) electrical measurement modes is a critical tool for the study of semiconductor devices and process development. A relatively new electrical mode, scanning microwave impedance microscopy (sMIM), measures a material’s change in permittivity and conductivity at the scale of an AFM probe tip [1]. sMIM provides the real and imaginary impedance (Re(Z) and Im(Z)) of the probe sample interface. By measuring the reflected microwave signal as a sample of interest is imaged with an AFM we can in parallel capture the variations in permittivity and conductivity and, for doped semiconductors, variations in the depletion layer geometry. An existing technique for characterizing doped semicondutors, scanning capacitance microscopy, modulates the tip-sample bias and detects the tip-sample capacitance with a lock-in amplifier. A previous study compares sMIM to SCM and highlights the additional capabilities of sMIM [2].

In this talk we focus on the detailed mechanisms and capabilities of the nano-scale C-V curves that can be obtained using sMIM to measure the tip-sample capacitance as a tip-sample bias is swept. Analogous to traditional macro-scale capacitance-voltage experiments, the nano-scale C-V curves probe properties such as doping concentration through their influence on the voltage dependent geometry of the depletion layer. In particular, in this talk we will address the ability to extract semiconductor properties, such as doping concentration, from the C-V curves. This study includes analytical and finite element modeling of tip-bias dependent depletion layer geometry and impedance. These are compared to experimental results on reference samples for both doped Si and GaN doped staircases to validate the systematic response of the sMIM-C channel to the doping concentration.

[1] S. Friedman, O. Amster, Y. Yang, “Recent advances in scanning Microwave Impedance Microscopy (sMIM) for nano-scale measurements and industrial applications.” Proceedings of the SPIE, Volume 9173, id. 917308 8 pp. (2014)

[2] B. Drevniok, St.J. Dixon-Warren, O. Amster, S.L. Friedman, and Y. Yang, “Extending Electrical Scanning Probe Microscopy Measurements of Semiconductor Devices Using Microwave Impedance Microscopy”, Proceedings of the 41st International Symposium on Testing and Failure Analysis (2015), pp. 77.