Effect of Surface Energy Reduction for Nano-Structure Stiction

Abstract

Nano-structure stiction during drying has often occurred due to scaling of semiconductor devices. For less stiction drying technology, lower surface tension liquids such as isopropyl alcohol (IPA) or super critical fluid (SCF) have been developed, but are lacking in enough performance or maturity for 300 mm leading-edge device wafer treatment. Thus, we have focused on the surface energy reduction process which enables separation of the once adhering structures. We have evaluated the effect of the surface energy on the stiction with both calculation and experimental data, and have successfully demonstrated that the surface energy reduction process can suppress high aspect-ratio nano-structure stiction.

Enabling Ultrahigh-Aspect-Ratio Silicon Nanowires Using Precise Experiments for Detecting the Onset of Collapse

“…Theoretical models developed in the literature are summarized in this section, and further descriptions are provided in the Supporting Information (SI). The collapse of high-aspect-ratio nanostructures ,− is dependent on the mechanical properties of the material, as well as the forces acting on it. The main modes of failure that may cause the collapse of NWs made with MACE are (i) buckling due to the weight of the nanowire, and (ii) surface forces (these are phenomena that keep the features from returning to a vertical position after they have collapsed) that include (a) adhesion to the substrate (ground collapse) and (b) adhesion to neighboring nanowires (lateral collapse), and (c) capillary forces acting on the nanowire when the MACE wet etch solution is drying.…”

Amorphous SiO2 Surface Irregularities and their Influence on Liquid Molecule Adsorption by Molecular Dynamics Analysis

“…In this report, we obtained insights into the limited molecular adsorption onto silanol groups on a-SiO 2 surfaces due to steric hindrance caused by their random positioning. This knowledge will contribute to the prevention of nanostructure stiction, 14 a critical issue in the drying process of wet cleaning in semiconductor manufacturing. The stiction can be avoided through surface treatment using a SMA for c-SiO 2 surfaces with no irregularities by reducing the surface energy with the liquid.…”

“…13 Then, IPA has been extensively used over the several technology nodes by combining with an engineering method of surface modification. 9,14,15 Koide et al lowered the surface energy of line-patterned silicon oxide structures through treatment with surface modification agents (SMA) to weaken adhesion energy between sticking patterns so that the stiction of pattern is restored. 14 In a design of surface modification methods, it is important to understand the state of the pattern surface during the drying step, and in the current situation where the scaling of device structures have been miniaturized to the nanoscale, molecular-level insights are required.…”

“…9,14,15 Koide et al lowered the surface energy of line-patterned silicon oxide structures through treatment with surface modification agents (SMA) to weaken adhesion energy between sticking patterns so that the stiction of pattern is restored. 14 In a design of surface modification methods, it is important to understand the state of the pattern surface during the drying step, and in the current situation where the scaling of device structures have been miniaturized to the nanoscale, molecular-level insights are required. Molecular dynamics (MD) simulations, which can analyze and visualize the movements of molecules, are suitable for this purpose.…”

Extendibility Study of Conventional IPA Drying Process From Dynamic Fluid Model for Pattern Collapse

“…IPA (iso-Propyl alcohol) has been widely used in semiconductor manufacturing for drying silicon wafers to mitigate watermarks and keep the surface clean after the wet cleaning process. Thus, the IPA process has been extended by combining with the other engineering techniques such as surface modification treatment (SMT) to dry fragile nano-sized Si patterns (1). As the scaling of advanced semiconductor devices continues, however, pattern collapse is one of the most challenging issues for the IPA drying process today.…”