Liquid-Cell Transmission Electron Microscopy Observation of Two-Step Collapse Dynamics of Silicon Nanopillars on Evaporation of Propan-2-ol: Implications for Semiconductor Integration Density

Abstract

Miniaturization of semiconductor devices has made structures more fragile, leading to potential collapses due to capillary forces during drying after wet cleaning. This has hampered the integration of transistors according to Moore's law. We have developed a method for preparing nanopillars in a liquid cell and have successfully observed their collapse by means of a crosssectional view in transmission electron microscopy. The dynamics of collapse as a result of capillary interactions involve two steps. First, the nanopillars collapse due to an imbalance in capillary forces caused by a difference in liquid levels at the gas−liquid interface. Second, a liquid pool formed between nanopillars maintains the collapsed state of the nanopillars through surface tension. The nanopillars recover on reimmersion in the liquid after the collapse. This method is effective, and is expected to contribute to the continued development of miniaturization and three-dimensionality of semiconductors.

Kinetics formulation for Two-Dimensional Growth Behavior of Water/Ice Interface on Si Substrate

“…Various strategies, including a novel sublimation drying method, have been devised to address this issue; however, it has proven to be insufficient for averting nanostructure collapse. , Sublimation drying consists of two primary stages: the formation of a solidification film of a sublimation agent onto a silicon (Si) substrate via cooling or precipitation, followed by drying it while maintaining it in the solid phase through the application of an inert gas spray. Furthermore, the complex phenomenon of nanostructure collapse during sublimation drying can be caused by a variety of factors, such as the high aspect ratio exhibited by nanostructures, types of sublimation chemicals, wet cleaning treatment, and inconsistent film properties across the substrate surface . Nevertheless, one of the most direct reasons underlying the collapse of nanostructures is solidification, particularly during the recalescence stage, when the ice crystal starts to propagate on the Si substrate.…”

New Formulas for Evaluation of Cyclohexanol Solidification on Substrates with Surface Nanostructures

“…Specifically, vertical nanostructures with a high aspect ratio (HAR) exhibit higher surface energy or increased nanoparticle activity . However, a primary obstacle in the production of these nanostructures is pattern collapse, which is a form of damage caused by capillary forces arising from various solution-based processes (also known as wet processes) employed during their fabrication. − These solution-based processes include wet etching, , hydrothermal synthesis, and chemical bath deposition …”

Microscopic properties of forces from ice solidification interface acting on silica surfaces based on molecular dynamics simulations

“…30 Elucidating the solidification state of water molecules in the QLL at the substrate-ice interface and revealing the microscopic forces exerted by the solidification phenomena on the solid wall are important for understanding the pattern collapse of semiconductor structures and the removal mechanism of particles attached to wafers on the nanometer scale, which in turn, is necessary for the development of semiconductor cleaning processes. [31][32][33][34][35][36] Although the QLLs on silica walls used as semiconductor substrates have been investigated experimentally [37][38][39][40] and analytically, 41,42 the details of the microscopic forces acting on the solid wall from the solidification interface have not been clarified on the nanometer scale.…”