Macroscopic Alignment of Block Copolymers on Silicon Substrates by Laser Annealing

Abstract

Laser annealing is a competitive alternative to conventional oven annealing of block copolymer (BCP) thin films enabling rapid acceleration and precise spatial control of the self-assembly process. Localized heating by a moving laser beam (zone annealing), taking advantage of steep temperature gradients, can additionally yield aligned morphologies. In its original implementation it was limited to specialized germanium-coated glass substrates, which absorb visible light and exhibit low-enough thermal conductivity to facilitate heating at relatively low irradiation power density. Here, we demonstrate a recent advance in laser zone annealing, which utilizes a powerful fiber-coupled near-IR laser source allowing rapid BCP annealing over a large area on conventional silicon wafers. The annealing coupled with photothermal shearing yields macroscopically aligned BCP films, which are used as templates for patterning metallic nanowires. We also report a facile method of transferring laser-annealed BCP films onto arbitrary surfaces. The transfer process allows patterning substrates with a highly corrugated surface and single-step rapid fabrication of multilayered nanomaterials with complex morphologies.

Green Nanofabrication Opportunities in the Semiconductor Industry: A Life Cycle Perspective

“…Energy cost depends on the ODT required for the process [ 115 ]. Laser-initiated self-assembly is very rapid but high costs can be incurred depending on laser power [ 127 , 128 ]. ALD can also be used.…”

Developing Anisotropy in Self‐Assembled Block Copolymers: Methods, Properties, and Applications

“…PDMS pads were adhered to BCP films prior to laser annealing which, upon exposure to thermal gradients from the laser annealing process, produced shear forces responsible for aligning the BCP domains. [103] Notably, the case studies discussed here do not often quantify the applied shear stress and its effect on the orientation of the BCP domains. Register et al systematically studied the effect of varying shear stress and polymer characteristics on the progression of alignment in cylinder forming PS-b-PHMA thin films.…”

“…While most current photothermal methods require a light-absorbing layer placed underneath the BCP film, a very recent study shows the capability to produce macroscopic alignment of BCPs on silicon substrates using laser-based annealing methods. [103] The expansion of processing windows, as well as substrate selection, would be useful to further enhance the value of these techniques. Additionally, reducing the defect density of BCP films is of paramount importance for their practical implantation into microelectronic applications, which has been explicitly discussed in many research articles.…”

“…[82][83][84][85][86][87][88] This methodology also enables manipulation of nanostructural orientation by varying processing parameters such as solvent selection and vapor removal rate, [89][90][91][92] which will be discussed in detail in the next section. Readers who are interested in other emerging methods for rapid ordering of block copolymers, such as thermal-assisted solvent vapor annealing, [93][94][95] direct solvent immersion annealing, [96][97][98] microwave annealing, [94,[99][100][101] and laser annealing, [102,103] can be directed to an excellent review by Majewski and Yager for relevant fundamentals of BCP ordering kinetics with different annealing approaches. [80] The advantages of bottom-up control over order, including low manufacturing costs and widely tunable morphologies, render BCPs to be critical structure-directing agents for a wide array of nanotechnology applications (Figure 3).…”

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

“…Compared to optical and electron lithography, the self-assembly of BCPs relies on the in-parallel self-registration of amphiphilic BCPs, driven by the chemical incompatibility between the constituent blocks. A high degree of control on self-assembled nanostructures, in terms of orientation [ 12 , 13 ], long-range ordering [ 14 , 15 , 16 ], morphology [ 17 ] and feature size [ 18 , 19 ] is related to the ability to finely tune the substrate functionalization, annealing conditions and the characteristic parameters of BCPs (i.e., molecular weight and composition). The potential use of BCPs for several semiconductor industry technologies was recently assessed by Liu et al [ 10 ].…”