Depth profiles of aluminum component in sequential infiltration synthesis-treated electron beam resist films analyzed by time-of-flight secondary ion mass spectrometry

Abstract

Sequential infiltration synthesis (SIS) is a promising method for organic-inorganic hybridization of organic polymer resist films in nanolithography. The understanding of the distribution of inorganic components in hybrid films is necessary for the practical use of SIS-treated resist films. In this study, we investigated the distribution of aluminum oxide in SIS-treated positive-tone electron beam resist films of poly(methyl methacrylate) and ZEP520A with thicknesses of 100, 40, and 20 nm by time-of-flight secondary ion mass spectrometry (TOF-SIMS). TOF-SIMS profiles revealed that the aluminum species of AlO − and AlO 2 − derived from aluminum oxide existed heterogeneously near the air/polymer surface, film inside, and polymer/substrate interface, and the distributions of respective species depended on film thickness. TOF-SIMS enabled the characterization of aluminum distribution in 20 nm thick resist films. It was suggested that the oxidation states of Al components were different between near the air/ polymer surface and near the polymer/substrate interface.

Reaction–Diffusion Transport Model to Predict Precursor Uptake and Spatial Distribution in Vapor-Phase Infiltration Processes

“…The presence of a substrate has been shown to influence infiltration in some systems, especially those with multiple alternating cycles of precursors and oxidants. 41 This may be due to physical differences in the polymer at the interface or chemical reactions that occur between the precursors and the substrates. However, in other infiltration systems, the substrate is not observed to have a significant influence on the spatial distribution or the overall uptake of the inorganic.…”

“…In addition to understanding the VPI process through mass uptake, it is worthwhile to investigate how infiltrated precursors are distributed throughout the depth of the polymer. Depth profiles are frequently created experimentally in the VPI community to help increase the understanding of VPI processes. − Additionally, the distribution of inorganic throughout the bulk of the polymer can play a role in material properties such as solvent stability . This section will show that the reaction–diffusion transport model can also create depth profiles to enhance understanding of VPI kinetics.…”

“…Within the vacuum science community, preliminary work has been done in this area with a focus on extracting fundamental parameters from experimental data. Kinetic parameters, such as diffusion coefficients, have been quantified, and general trends have been observed using in situ experimental techniques such as quartz crystal microgravimetry (QCM) − and spectroscopic ellipsometry , as well as ex situ techniques such as time-of-flight secondary ion mass spectrometry (TOF-SIMS), ,, cross-sectional electron microscopy paired with energy-dispersive X-ray spectroscopy (EDX) and spectroscopic ellipsometry . Additional information has also become available from these works, such as the observation of non-Fickian diffusion behavior in certain precursor–polymer systems, dependencies of diffusion coefficients on concentrations of reactive groups, and the influence of temperatures on both equilibrium sorption uptake and diffusion behaviors .…”

Recent Advances in Sequential Infiltration Synthesis (SIS) of Block Copolymers (BCPs)

“…It is based on the detection of characteristic X-rays produced from the interaction of high-energy electrons with the specimen atoms, allowing the univocal analysis of the elemental composition. This technique has been used for both in-plane and in-depth chemical characterization of the infiltrated polymer [ 31 , 43 , 51 , 59 , 61 , 62 , 63 ].…”

“…However, appropriate calibration standards are required for quantitative depth-profiling [ 68 ]. ToF-SIMS has been used to understand the depth distribution of oxides after SIS treatment, usually adopted in homopolymer layers such as PMMA [ 56 , 63 ] and PS [ 56 ], PET film and fibers [ 54 ], but also in block copolymers layers such as PS- b -P2VP both as micellar films [ 58 ] and self-assembled nanodomains infiltrated with [ 43 ].…”