Understanding the effect of confinement in scanning spreading resistance microscopy measurements

Abstract

Scanning spreading resistance microscopy (SSRM) is a powerful technique for quantitative two-and three-dimensional carrier profiling of semiconductor devices with sub-nm spatial resolution. However, considering the sub-10nm dimensions of advanced devices and the introduction of three-dimensional architectures like FinFETs and nanowires, the measured spreading resistance is easily impacted by parasitic series resistances present in the system. The limited amount of material, presence of multiple interfaces and confined current paths may increase the total resistance measured by SSRM beyond the expected spreading resistance, which can ultimately lead to an inaccurate carrier quantification. Here, we report a TCAD assisted experimental study to identify the different parameters affecting the SSRM measurements in confined volumes. Experimentally, the two-dimensional current confinement is obtained by progressively thinning down uniformly doped blanket SOI wafers using scalpel SSRM. The concomitant SSRM provides detailed electrical information as a function of depth up to oxide interface. We show that the resistance is most affected by the interface traps in case of a heterogeneous sample, followed by the intrinsic resistance of the current carrying paths. Further, we show that accurate carrier quantification is ensured for typical back-contact distances of 1 µm if the region of interest is at least 9 times larger than the probe radius.

Apparent size effects on dopant activation in nanometer-wide Si fins

“…Additionally, scanning spreading resistance microscopy (SSRM) 2,11,12 measurements are difficult to quantify for such nanometer scaled features, as the measured spreading resistance is easily impacted by parasitic series resistances. 13 As such, a correlative approach, i.e., combining the information obtained with different techniques, is generally proposed as a solution to collect reliable information on the (size-dependent) electrical properties of these nanoscale objects. 14,15 In this article, we propose a novel correlative approach to study apparent size-dependent dopant activation in nanometerwide B doped Si fins.…”

Mapping of integrated PIN diodes with a 3D architecture by scanning microwave impedance microscopy and dynamic spectroscopy

“…Scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM) [3][4][5] are modes widely used for the detection of charge carriers, carrier types, and density of defects. These modes provide sub-10 nm two-dimensional maps of the electrical properties of doped semiconductor layers [1,[6][7][8] when a fixed bias is applied to the nanoscale contact.…”