Pulsed Force-Scanning Spreading Resistance Microscopy (PF-SSRM) for High Spatial Resolution 2D-dopant Profiling.

Abstract

AbstractScanning Spreading Resistance Microscopy (SSRM) is now widely used for two-dimensional doping profiling with high spatial resolution. The need for a high force between the tip and the sample in order to obtain a good electrical contact, leads to a fast degradation of the tip (and the sample) while scanning. Tip damage is mainly due to the shear force occurring while scanning in contact mode at high forces leading to breakage (cleavage) of sharp tips or a rapid increase of tip radius (wear). The latter adversely affects the accuracy of the electrical measurements, as the contact radius is a determining parameter for quantification. The strong abrasive force also necessitates the use of tips composed of very hard material such as doped diamond, which has however a limited resistivity, and so far prevented the use of metallic probes. In addition the high force also prevents the simultaneous acquisition of high quality topography data. The solution to these problems is obtained by implementing the Modulated Force Principle (MFP). The latter consists of applying a variable (for instance pulsed) force while scanning, reducing the force during the lateral movement of the tip and synchronizing the electrical measurements with the high force periods. The latter results in lower lateral forces and introduces a quasi multi point contact mode. MFP also allows to obtain a better topography image by synchronizing the topography measurement with the low force part of the force cycle. The MFP leads to a drastic reduction of the surface and probe damage while maintaining high quality electrical data. The implementation of multiplexed detectors within the force cycle further enables the simultaneous acquisition of spreading resistance and topography during one scan, and/or the combination with multiple linear current detectors, capacitance sensors or tunneling current measurements.