Lei Chen

As semiconductor manufacturing advances toward three-dimensional (3D) integration architectures, the precise chemical mechanical polishing (CMP) of high-aspect-ratio (HAR) nanothrough-silicon vias (n-TSVs) utilizing cobalt (Co) interconnects has become critically important. However, achieving nanoscale, nondestructive, and accurate evaluation of Co core exposure and interfacial planarization during the CMP process remains a formidable metrological challenge. Herein, we report the reliable nanoscale compositional characterization of SiO2/TiN/Co n-TSV heterostructures across progressive CMP stages using a custom-built 405 nm photoinduced force microscopy (PiFM) system capable of simultaneously acquiring optical force amplitude and phase signals. By leveraging both amplitude and phase mapping, together with material-dependent variations in the relative contributions of repulsive photothermal expansion forces and attractive optical gradient forces, PiFM precisely tracks the nanoscale structural evolution of n-TSVs during CMP–specifically, the progressive removal of overlayers and the eventual unmasking of the Co core. Notably, we demonstrate that the optical force phase signal provides clearer material contrast and improved detection sensitivity compared to conventional optical force amplitude imaging. This phase-sensitive contrast enables reliable differentiation of complex heterogeneous interfaces and tracks localized Co core exposure, as well as subsequent material depletion due to overpolishing. Finally, correlative conductive atomic force microscopy validates the polishing progression and Co exposure logic inferred by PiFM. This work establishes 405 nm PiFM as a promising, facile, and nondestructive metrology tool. By leveraging both optical force amplitude and phase signals, it provides critical feedback for characterizing nanoscale material interfaces and evaluating polishing quality in Co-based n-TSV interconnects, thereby facilitating CMP process optimization and improving the reliability of next-generation 3D interconnect architectures.

Atomic surface of silicon (Si) wafers without particulate contamination achieved by chemical mechanical polishing (CMP) is highly desired for advanced chip manufacturing. Traditional CMP processes usually employ abrasive-containing slurries, resulting in significant particulate residues and high-cost post-treatments. To settle this challenge, a novel abrasive-free CMP slurry only including designated chain-length alkylamine was developed based on the observed dependence between the Si surface roughness and alkylamine chain length. After polishing by the long-chain hexylamine slurry, an atomic surface without particulate contamination is achieved with surface roughness as low as 0.13 nm, which is 85% lower than that obtained using short-chain methylamine slurry, while maintaining a material removal rate of 57.7 nm/min. Then, we established an atomic mechanistic framework that integrates interfacial chemistry with mechanical action to understand how alkylamine chain length modulates mechanochemistry in abrasive-free Si CMP. Density functional theory calculations show that long-chain alkylamines adsorb more readily but have a milder weakening effect on Si–Si bonds, whereas short-chain counterparts, despite weaker adsorption, more effectively weaken these bonds. Nanowear tests and X-ray photoelectron spectroscopy corroborate that the dynamic equilibrium between the adsorption strength and bond weakening promotes the formation of a mechanically vulnerable reaction layer composed by O_x–Si–N_y compounds amenable to abrasive-free removal for atomic smoothness. Our findings shift the mechanistic paradigm from conventional abrasive-involved interfacial interactions to abrasive-free, chemically driven, adsorption-controlled removal processes. These insights offer valuable theoretical guidelines for both academic research and industrial practice in ultra-precision manufacturing and advanced semiconductor processing.

The application of silicon carbide ceramic matrix composite (CMC-SiC) as hot-end components in next-generation advanced gas turbine is susceptible to corrosion by high-temperature, high-velocity water vapor present in combustion environments. Furthermore, its amorphous-crystalline composite structure results in a more complex corrosion response under water vapor exposure. Reactive molecular dynamics simulations were employed to investigate the differences in water corrosion behavior between crystalline and amorphous SiC over a temperature range of 1000-2000 K. At 1000 K, the amorphous SiC surface exhibits greater susceptibility due to its disordered atomic structure. In contrast, at 2000 K, the Si surface of 4H-SiC undergoes more severe corrosion. This reversal in corrosion behavior can be attributed to the formation and subsequent volatilization of the Si-O-Si network from the SiC slab. Specifically, the Si-O-Si network exhibits stronger bonding with the amorphous SiC surface, making it more resistant to corrosion by high-temperature water molecules. These findings offer valuable insights into the optimization of CMC-SiC hot-end components.