AVS 72 Session TF2-WeM: VSHOP Applications II, Semiconductor Manufacturing

Over the last few years, HF-containing plasmas have been widely used for etching of Si-based dielectrics for various applications, including in the fabrication of 3-D NAND memory devices. During SiN_x etching with HF plasma, ammonium fluorosilicate (AFS) forms as a transient byproduct significantly influencing the etch behavior. While AFS formation during SiN_x etching has been known for several decades, the underlying mechanism for its formation and removal remains unclear. In this study, we have used in situ attenuated total reflection Fourier-transform infrared spectroscopy to study the changes in the chemical boning on the SiN_x surface during reactive ion etching, along with the AFS formation and removal dynamics. We will show that a thin polyurea layer grown conformally by molecular layer deposition can be used to protect the sidewalls during etching of SiO₂/SiN_x stacks in high-aspect-ratio structures. We will demonstrate the impact of the MLD film on etching of the underlying SiN_x and SiO₂ films in a direct versus remote HF plasma, and HF gas. We will also show how the polyurea film degrades in a plasma environment and how it influences the formation of AFS.

Atomic and molecular layer deposition (ALD, MLD) techniques boast precise control of film thickness, conformal growth, and a wide range of material compositions.Generally, ALD and MLD thin films are non-porous, yet introduction of porosity would enable a wide range of uses ranging from catalysis to low-k dielectrics for electronics.Here, we have examined the purposeful inclusion of organic molecules including bifunctional and monofunctional alcohols during the MLD/ALD process and their subsequent removal using thermal and/or UV treatment to induce porosity.We examined the evolution of various physical and electrical properties with thermal treatment as well as the composition of these films.We found that the density and dielectric constant of these materials are smaller than the parent dense ALD oxides.This strategy is thus promising for tailor made dielectrics based on sequential self-limiting surface reactions characteristic of the ALD and MLD processes.This development parallels other methods for forming porous inorganic oxides such as terpinene inclusion in silicon-based dielectrics or block copolymer templating of inorganic solids.

As the semiconductor industry demands ever-smaller critical dimensions, extreme ultraviolet (EUV) lithography has become essential for next-generation patterning. However, conventional organic resists suffer from poor sensitivity under EUV exposure; therefore, hybrid resists have emerged as a promising strategy to address this challenge. In this work, we prepared a hybrid resist via sequential infiltration synthesis (SIS) into poly(methyl methacrylate) (PMMA) using trimethyl indium and trimethyl gallium as metal precursor, with water and ethylene glycol as co-reactants. Due to the scarcity of EUV light sources, electron beam lithography (EBL) was employed as a surrogate tool to evaluate resist performance. Compared to pristine PMMA, SIS resists exhibit improved sensitivity for negative tone behavior and achieve high-resolution patterning down to sub-50 nm linewidth. To investigate the mechanism of improved sensitivity, μ-Raman spectroscopy, μ-X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy were employed. Based on the comprehensive characterization data, we propose molecular-level structural model of the PMMA–InOₓ hybrid resist that explains its enhanced sensitivity.