Three-Dimensional Nanoscale Mapping of State-of-the-Art Field-Effect Transistors (FinFETs)

Abstract

The semiconductor industry has seen tremendous progress over the last few decades with continuous reduction in transistor size to improve device performance. Miniaturization of devices has led to changes in the dopants and dielectric layers incorporated. As the gradual shift from two-dimensional metal-oxide semiconductor field-effect transistor to three-dimensional (3D) field-effect transistors (finFETs) occurred, it has become imperative to understand compositional variability with nanoscale spatial resolution. Compositional changes can affect device performance primarily through fluctuations in threshold voltage and channel current density. Traditional techniques such as scanning electron microscope and focused ion beam no longer provide the required resolution to probe the physical structure and chemical composition of individual fins. Hence advanced multimodal characterization approaches are required to better understand electronic devices. Herein, we report the study of 14 nm commercial finFETs using atom probe tomography (APT) and scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (STEM-EDS). Complimentary compositional maps were obtained using both techniques with analysis of the gate dielectrics and silicon fin. APT additionally provided 3D information and allowed analysis of the distribution of low atomic number dopant elements (e.g., boron), which are elusive when using STEM-EDS.

Examining the Effect of Evaporation Field on Boron Measurements in SiGe: Insights into Improving the Relationship Between APT and SIMS Measurements of Boron

“…This offset is particularly problematic because rather than adding clarity to the analysis of three-dimensional structures via a new perspective, the APT measurements can become confusing and/or require the addition of a scaling factor in order to compare side-by-side data with SIMS. APT has matured rapidly in the field of semiconductor devices and is increasingly used to provide advanced measurements directly on the source/drain SiGe of devices, particularly fin-shaped field-effect transistors (FinFETs) (Takamizawa et al, 2012; Kambham et al, 2013; Grenier et al, 2014; Martin et al, 2016; Parikh et al, 2017; Martin et al, 2018). However, these long held concerns over the accuracy of APT measurements of B due to discrepancies with SIMS analysis (Thompson et al, 2006; Estivill et al, 2017) need to be better understood and, if possible, resolved.…”

Correlative microscopy and techniques with atom probe tomography: Opportunities in materials science

“…Such insights can help improve the interpretation of APT data and help to better understand limitations of APT and current reconstruction algorithms, which will be crucial as the material systems analyzed by APT become highly heterogenous and complex. 36,37 Perspectives: Efforts to develop in situ combined instruments…”

Segregation mechanism of arsenic dopants at grain boundaries in silicon

“…Silicon (Si) crystals in most electronic devices, including field effect transistors (FETs) and sensors, are doped with III or V-group elemental impurities in order to achieve specific electrical properties. The characteristic size of the devices is scaling down over the past decades, and it is now below a few tens of nanometres, by using Si nanostructures such as nanowires [1][2][3] and nano-fins [4][5][6]. At this nanometres scale, three-dimensional (3D) distribution of dopant atoms has an important impact on the reliability and performance of individual devices, since a localized dopant fluctuation is increasingly affecting the electrical characteristics [7].…”