We approach this multidimensional characterization problem by developing measurement-based techniques to rapidly quantify all of the relevant properties of thin-film materials, interfaces, and microelectronic structures. We make extensive use of finite-element simulations, as well as linear and non-linear circuit models, in order to determine consistent material properties from measurements of ensembles of planar or microelectronic devices, and supplement device-based characterization with spatially-resolved measurements where possible. These measurement-based material descriptions can then be compared and combined with results of computational approaches to provide more complete models of complex systems, which are then used in the subsequent intelligent design and optimization of electronic materials, devices, and systems, and as a basis for new materials discovery.
Our measurement-based approach makes use of standardized, microfabricated test structures, such as planar transmission lines and simple lumped-element components. We then apply wafer-probe-based measurements as well as scanned-probe approaches to quantify different material parameters for a given material orientation. We have developed a comprehensive suite of measurements to access the multiple different material parameters most relevant for modeling device performance:
- Quantitative measurement of the broadband permittivity and permeability over the range of frequencies of interest for most electronic applications (several Hz to > 500 GHz);
- Measurement of spatially-resolved electromagnetic properties down to nanometer length scales;
- Electromagnetic measurements to quantify effects of temperature and strain on material properties;
- Determination of higher-order material coefficients from nonlinear measurements;
- Electromagnetic measurements in the presence of electric- and magnetic-field biases, to determine cross-couplings of different phenomena (magnetoelectric coefficient, piezoelectric coefficient, etc.);
- Electronic measurement of thermal properties.
We also possess the metrology expertise to carry out electromagnetic material characterization with atomic-scale spatial resolution. As the electronics, semiconductor, and storage technology industries scale down to features and components consisting of only a few atoms, this metrology is becoming more and more critical. At this scale, individual dopants and and defects critically influence behavior and modeling of electronic materials. In addition to the characterization of the atomic-scale systems themselves, we are studying approaches to interconnects and other signal-control strategies that may cross multiple length scales.