We develop new approaches to optical microscopy and electromagnetic modeling to enable improved metrology of nanoscale structures with dimensions more than an order of magnitude below traditional resolution limits. New applications and standards produced from these methods include patterned semiconductor defect inspection and critical dimension metrology.
- Resolving critical issues in deep subwavelength linewidth and defect metrology for the U.S. semiconductor industry by enabling the world's smallest multi-dimensional measurements of objects using optical imaging
- Providing quantitative information from scattered light images at resolutions previously thought impossible.
Figure 2. Schematic of the 3-D electromagnetic scattering field above a periodic array.
This project develops new approaches to optical microscopy based on a high magnification optical platform that samples the full 3-D scattered field. Both the semiconductor industry and the evolving nanomanufacturing sector are facing enormous challenges measuring nanometer scale features over large areas, needed for effective manufacturing process control of products that incorporate billions of nanoscale features. Optical microscopy is a high-throughput metrology methodology that provides a unique advantage since it is a high-bandwidth measurement method that is inherently parallel.
Measurements with sensitivity to features less than one-twentieth the wavelength can be made by analysis of scattered light profiles and the use of physics-based modeling. Extensive electromagnetic modeling, developed in-house, enables quantitative metrology of nanoscale structures more than an order of magnitude below traditional resolution limits.
This project meets key NIST priorities in advanced manufacturing, energy, and photonics. We have had several contracts from the semiconductor industry as well as the Department of Energy for fuel-cell process control research. We have directly impacted semiconductor hardware platforms for optical overlay, defect, and critical dimension measurement. This project has also had a broad impact on the extensibility of optical methods for semiconductor manufacturing metrology.
Figure 3. Comparison between experimental and simulated differential images of a bridge defect.
Figure 4. Constructing a model for simulating the reflectivity from fuel cell membranes.
Figure 5. Loading a 200 mm wafer onto the world-class NIST 193 nm Microscope.
- Demonstrating to the semiconductor industry finite arrays of lines with areas much smaller than the microscope's field-of view, a key step towards more accurate measurement of critical dimensions such as the line width.
- Completing first major upgrade to the NIST λ = 193 nm microscope enabling 10x fluence, illumination and collection path filtering, and future interferometric solutions.
- Addressed the effects of line edge and line width roughness (LER, LWR) upon both defect measurements (e.g., false positives) and also optical parametric measurements of line width and height (e.g., systematic biases).
- Hybridized sub-20 nm wide arrays of lines from both Intel and from SEMATECH.
- Detected defects with widths as small as (16 ± 2) nm, or 1/12th the wavelength, without modeling using a new 3-D volumetric approach that uses all the scattered intensity data in xyz space.
- 2013 R&D 100 Award for "Quantitative Hybrid Metrology," a new method that enhances multiple measuring instruments by tying them together statistically in novel combinations. Hybrid adopted publically by IBM, GlobalFoundries, Nova, and others.
- 2013 Intel Outstanding Researcher in Metrology Award, noting "This work is both fundamentally unique and technically important to the industry… scatterfield microscopy helped spur industry wide interest."
Figure 1. Clean-room conditions for the NIST 193 nm Microscope allow scientists to measure state-of-the-art nanoscale features.
Lead Organizational Unit:
Source of Extramural Funding:
- U.S. Department of Energy
- Corning Specialty Materials
- University of Maryland
- Several additional partners in the U.S. Semiconductor Industry
- NIST 193 nm Microscope
- NIST Visible-Light Scatterfield Microscope
- NIST Overlay Tool
- NIST Spectroscopic Ellipsometer
- NIST Large-Angle Projection Scatterometer
- NIST Atomic Force Microscopes
- NIST Scanning Electron Microscopes
- Advanced Measurement Laboratory