Opportunity at National Institute of Standards and Technology (NIST)
Nanoscale Stress Mapping Using Confocal Raman Spectroscopy and Electron Back Scattered Diffraction
Material Measurement Laboratory, Materials Measurement Science Division
Please note: This Agency only participates in the February and August reviews.
|Cook, Robert Francis
|Friedman, Lawrence H
Among the three modes of accommodating deformation-elastic, plastic, and fracture-quantifying material or structural resistance to these at the nanoscale is least advanced for fracture. This is in spite of the fact that most materials used in microelectronic, photonic, and microelectromechanical devices are still brittle at this length scale and fracture is one of the leading detractors of device yield and reliability. In addition, determining the state of deformation at the nanoscale is difficult. Optimizing the yield and reliability of devices that depend on nanoscale “strain engineering” is made difficult as is the identification of the “stress signatures” of plastic and fracture defects that control device performance and reliability. In this project a confocal Raman spectroscopy technique is being developed that allows stress measurement at the nanoscale, which in turn enables measurement of stress-intensity factors at crack tips and toughness to be estimated at the nanoscale. The technique is based on hyperspectral Raman measurements and both large-area and high-resolution methods are being developed using nanoindentations in Si and other materials as test vehicles. Advanced peak-fitting and super-resolution techniques are being developed to enable stress resolution of approximately 20 MPa (in Si) at nanoscale lateral spatial resolution and depth resolution of approximately 300 nm. Accuracy of the method is investigated by comparison of indentation and crack field stress distributions with both analytical expressions and strain measurements from electron back-scattered diffraction (EBSD), with which strains at the 1 x 10-4 level can be measured. Extension of the method to thin-film systems, microelectromechanical test structures, and stress-engineered surfaces is underway. This project provides an opportunity to advance state-of-the-art metrology in mechanics, optics, and EBSD analysis.
Confocal microscopy; Electron back scattered diffraction; Fracture; MEMS (Microelectromechanical devices); Microelectronics; Photonics; Raman spectroscopy; Stain engineering; Stress mapping; Toughness;
Open to U.S. citizens
Open to Postdoctoral applicants