Atom-Probe Tomography of Semiconductor Materials and Device Structures
- PDF / 627,248 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 101 Downloads / 235 Views
Tomography of Semiconductor Materials and Device Structures
Lincoln J. Lauhon, Praneet Adusumilli, Paul Ronsheim, Philip L. Flaitz, and Dan Lawrence Abstract The development of laser-assisted atom-probe tomography (APT) analysis and new sample preparation approaches have led to significant advances in the characterization of semiconductor materials and device structures by APT. The high chemical sensitivity and three-dimensional spatial resolution of APT makes it uniquely capable of addressing challenges resulting from the continued shrinking of semiconductor device dimensions, the integration of new materials and interfaces, and the optimization of evolving fabrication processes. Particularly pressing concerns include the variability in device performance due to discrete impurity atom distributions, the phase and interface stability in contacts and gate dielectrics, and the validation of simulations of impurity diffusion. This overview of APT of semiconductors features research on metal-silicide contact formation and phase control, silicon field-effect transistors, and silicon and germanium nanowires. Work on silicide contacts to silicon is reviewed to demonstrate impurity characterization in small volumes and indicate how APT can facilitate defect mitigation and process optimization. Impurity contour analysis of a pFET semiconductor demonstrates the site-specificity that is achievable with current APTs and highlights complex device challenges that can be uniquely addressed. Finally, research on semiconducting nanowires and nanowire heterostructures demonstrates the potential for analysis of materials derived from bottom-up synthesis methods.
Metrology Challenges in Highly Scaled Semiconductors Materials characterization of semiconductors plays an essential role in the steady improvements in semiconductor technology performance and costs. As device dimensions shrink, impurity atom diffusion is strongly affected by interface proximity and segregation. The structural three-dimensional effects on diffusion and impurity activation cannot be characterized by many conventional characterization tools. Secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM) have been the main sources of information on impurity 738
diffusion and materials structure, respectively. Shrinking device dimensions have, however, long surpassed the lateral resolution of SIMS, so diffusion studies are limited to planar structures. TEM-based techniques, including electron energy loss spectroscopy (EELS) and x-ray fluorescence, have a spatial resolution comparable to the probe diameter of 1 nm. While this spatial resolution is suitable for small geometry device analysis, sensitivity is limited for impurities; arsenic can be detected to 5 × 1020 cm−3 but not at the typical junction concentrations of ~5 × 1018 cm−3.
In contrast, the combined high sensitivity (~5 × 1017 cm−3 or 10 appm) and subnanometer-scale spatial resolution of atom-probe tomography (APT) suggest an important role for it in future device characterization
Data Loading...
