Poly(styrene)-block-Maltoheptaose Films for Sub-10 nm Pattern Transfer: Implications for Transistor Fabrication.

Anette Löfstrand,Wen-Chang Chen,Reza Jafari Jam,Redouane Borsali,Tommy Nylander,Ivan Maximov,Karolina Mothander,Muhammad Mumtaz,Alexei Vorobiev

doi:10.1021/acsanm.1c00582

Abstract

Sequential infiltration synthesis (SIS) into poly(styrene)-block-maltoheptaose (PS-b-MH) block copolymer using vapors of trimethyl aluminum and water was used to prepare nanostructured surface layers. Prior to the infiltration, the PS-b-MH had been self-assembled into 12 nm pattern periodicity. Scanning electron microscopy indicated that horizontal alumina-like cylinders of 4.9 nm diameter were formed after eight infiltration cycles, while vertical cylinders were 1.3 nm larger. Using homopolymer hydroxyl-terminated poly(styrene) (PS–OH) and MH films, specular neutron reflectometry revealed a preferential reaction of precursors in the MH compared to PS–OH. The infiltration depth into the maltoheptaose homopolymer film was found to be 2.0 nm after the first couple of cycles. It reached 2.5 nm after eight infiltration cycles, and the alumina incorporation within this infiltrated layer corresponded to 23 vol % Al2O3. The alumina-like material, resulting from PS-b-MH infiltration, was used as an etch mask to transfer the sub-10 nm pattern into the underlying silicon substrate, to an aspect ratio of approximately 2:1. These results demonstrate the potential of exploiting SIS into carbohydrate-based polymers for nanofabrication and high pattern density applications, such as transistor devices.

Highlights

Block copolymer (BCP) lithography has received considerable interest for the fabrication of high-resolution nanostructures due to the ability of BCP films to self-organize into regular nanometer-sized patterns over large areas.[1−6] The BCP approach combines extremely high resolution with low-cost nanofabrication to form a variety of periodically arranged structures
The aspect ratio of critical dimension is, approximately 2:1. Both dynamic and semi-static SIS into MH and PS−OH polymer were investigated by ex situ neutron reflectometry (NR). This characterization method provided a quantitative measure of the infiltration depth of trimethyl aluminum (TMA) and water into MH homopolymer
The results showed an increase in neutron scattering length density (SLD) with the number of infiltration cycles

Summary

Introduction

Block copolymer (BCP) lithography has received considerable interest for the fabrication of high-resolution nanostructures due to the ability of BCP films to self-organize into regular nanometer-sized patterns over large areas.[1−6] The BCP approach combines extremely high resolution with low-cost nanofabrication to form a variety of periodically arranged structures. Some of these structures, e.g., cylinders, lamellae, or spheres, are of great interest in device fabrication, and BCPs have attracted attention for applications in nanoelectronics,[7−9] photonics,[10] bit-patterned media,[11] and other technologies.[12] In response to this interest, novel pattern transfer methods using BCP lithography in the sub-10 nm regime are needed, which is the foundation for further application development. As a Received: February 25, 2021 Accepted: April 29, 2021 Published: May 13, 2021

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Conclusion