TY - GEN A1 - Lechowski, Bartlomiej A1 - Kutukova, Kristina A1 - Grenzer, Joerg A1 - Panchenko, Iuliana A1 - Krueger, Peter A1 - Clausner, Andre A1 - Zschech, Ehrenfried T1 - Laboratory X-ray Microscopy of 3D Nanostructures in the Hard X-ray Regime Enabled by a Combination of Multilayer X-ray Optics T2 - Nanomaterials N2 - High-resolution imaging of buried metal interconnect structures in advanced microelectronic products with full-field X-ray microscopy is demonstrated in the hard X-ray regime, i.e., at photon energies > 10 keV. The combination of two multilayer optics—a side-by-side Montel (or nested Kirkpatrick–Baez) condenser optic and a high aspect-ratio multilayer Laue lens—results in an asymmetric optical path in the transmission X-ray microscope. This optics arrangement allows the imaging of 3D nanostructures in opaque objects at a photon energy of 24.2 keV (In-Kα X-ray line). Using a Siemens star test pattern with a minimal feature size of 150 nm, it was proven that features < 150 nm can be resolved. In-Kα radiation is generated from a Ga-In alloy target using a laboratory X-ray source that employs the liquid-metal-jet technology. Since the penetration depth of X-rays into the samples is significantly larger compared to 8 keV photons used in state-of-the-art laboratory X-ray microscopes (Cu-Kα radiation), 3D-nanopattered materials and structures can be imaged nondestructively in mm to cm thick samples. This means that destructive de-processing, thinning or cross-sectioning of the samples are not needed for the visualization of interconnect structures in microelectronic products manufactured using advanced packaging technologies. The application of laboratory transmission X-ray microscopy in the hard X-ray regime is demonstrated for Cu/Cu6Sn5/Cu microbump interconnects fabricated using solid–liquid interdiffusion (SLID) bonding. KW - X-ray microscopy KW - high-resolution radiography KW - nanostructure KW - advanced packaging Y1 - 2024 U6 - https://doi.org/10.3390/nano14020233 SN - 2079-4991 VL - 14 IS - 2 ER - TY - GEN A1 - Kutukova, Kristina A1 - Lechowski, Bartlomiej A1 - Grenzer, Joerg A1 - Krueger, Peter A1 - Clausner, André A1 - Zschech, Ehrenfried T1 - Laboratory High-Contrast X-ray Microscopy of Copper Nanostructures Enabled by a Liquid-Metal-Jet X-ray Source T2 - Nanomaterials N2 - High-resolution imaging of Cu/low-k on-chip interconnect stacks in advanced micro-electronic products is demonstrated using full-field transmission X-ray microscopy (TXM). The comparison of two lens-based laboratory X-ray microscopes that are operated at two different photon energies, 8.0 keV and 9.2 keV, shows a contrast enhancement for imaging of copper nanostructures embedded in insulating organosilicate glass of a factor of 5 if 9.2 keV photons are used. Photons with this energy (Ga-Kα radiation) are generated from a Ga-containing target of a laboratory X-ray source applying the liquid-metal-jet technology. The 5 times higher contrast compared to the use of Cu-Kα radiation (8.0 keV photon energy) from a rotating anode X-ray source is caused by the fact that the energy of the Ga-Kα emission line is slightly higher than that of the Cu-K absorption edge (9.0 keV photon energy). The use of Ga-Kα radiation is of particular advantage for imaging of copper interconnects with dimensions from several 100 nm down to several 10 nm in a Cu/SiO2 or Cu/low-k backend-of-line stack. Physical failure analysis and reliability engineering in the semiconductor industry will benefit from high-contrast X-ray images of sub-µm copper structures in microchips. KW - X-ray microscopy KW - radiography KW - image contrast KW - nanostructure KW - physical failure analysis KW - copper interconnects Y1 - 2024 U6 - https://doi.org/10.3390/nano14050448 SN - 2079-4991 VL - 14 IS - 5 ER -