publications
Research and innovation in metrology and inspection with short wavelength light for semiconductor applications.
Scatterometry (ASML)Soft x-ray: novel metrology for 3D profilometry and device pitch overlay
Due to their increasingly complex 3D geometries, upcoming gate all around (GAA) devices pose new metrology challenges
for which there is not yet any established HVM metrology solution, in particular for various critical timed etch steps. Soft x-ray (SXR) scatterometry using 10-20 nm wavelength light is a promising next-generation metrology technique for 3D profile metrology and overlay (OVL) applications. This wavelength regime offers unique benefits over existing metrology techniques today.
Soft X-Ray Scatterometry: At-Resolution, 3D Metrology for the EUV Era
SXR scatterometry using 10-20nm wavelength light is a promising next-generation metrology technique with potential for overlay (OVL) and edge placement error (EPE) control, as well as 3D profile metrology applications and the outlook to have sufficient throughput for HVM. As EUV is to DUV lithography, we foresee SXR could relate similarly to optical scatterometry.
Nondestructive, high-resolution, chemically specific 3D nanostructure characterization using phase-sensitive EUV imaging reflectometry
Next-generation nano- and quantum devices have increasingly complex 3D structure. As the dimensions of these devices shrink to the nanoscale, their performance is often governed by interface quality or precise chemical or dopant composition.
General-purpose, wide field-of-view reflection imaging with a tabletop 13 nm light source
Lensless imaging with short-wavelength light is a promising method for achieving high-resolution, chemically sensitive images of a wide variety of samples. The use of 13 nm illumination is of particular interest for materials science and the imaging of next-generation nanofabricated devices. Prior to this work, there was an unmet need for a microscope that can image general samples with extreme ultraviolet light, which requires a reflection geometry. Here, we fulfill this need by performing lensless imaging using a 13 nm high-harmonic beam at grazing incidence, where most materials are reflective.
Quantitative Chemically Specific Coherent Diffractive Imaging of Reactions at Buried Interfaces with Few Nanometer Precision
We demonstrate quantitative, chemically specific imaging of buried nanostructures, including oxidation and diffusion reactions at buried interfaces, using nondestructive tabletop extreme ultraviolet (EUV) coherent diffractive imaging (CDI). Copper nanostructures inlaid in SiO2 are coated with 100 nm of aluminum, which is opaque to visible light and thick enough that neither visible microscopy nor atomic force microscopy can image the buried interface. Short wavelength high harmonic beams can penetrate the aluminum layer, yielding high-contrast images of the buried structures.
The soft X-ray source is based on high-order harmonic generation, which was discovered at the end of the 1980s (see: Ferray et al. and MacPherson et al.). This phenomenon is behind the generation of attosecond pulses of light, which led to the award of a Nobel Prize in Physics 2023 to Pierre Agostini, Ferenc Krausz and Anne L’Huillier. For more information about the history behind the source, you can listen to the Nobel Lecture by Anne L’Huillier: