Feature size control using surface reconstruction temperature in block copolymer lithography for InAs nanowire growth

Abstract

Here we present a method to control the size of the openings in hexagonally organized BCP thin films of poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) by using surface reconstruction. The surface reconstruction is based on selective swelling of the P4VP block in ethanol, and its extraction to the surface of the film, resulting in pores upon drying. We found that the BCP pore diameter increases with ethanol immersion temperature. In our case, the temperature range 18 to 60 °C allowed fine-tuning of the pore size between 14 and 22 nm. A conclusion is that even though the molecular weight of the respective polymer blocks is fixed, the PS-b-P4VP pore diameter can be tuned by controlling temperature during surface reconstruction. These results can be used for BCP-based nanofabrication in general, and for vertical nanowire growth in particular, where high pattern density and diameter control are of importance. Finally, we demonstrate successful growth of indium arsenide InAs vertical nanowires by selective-area metal-organic vapor phase epitaxy (MOVPE), using a silicon nitride mask patterned by the proposed PS-b-P4VP surface reconstruction lithography method.

Directed Self‐Assembly for Dense Vertical III–V Nanowires on Si and Implications for Gate All‐Around Deposition

“…The average diameter of the free self‐assembled BCP pore openings was measured in scanning electron microscope (SEM) to 16 nm (3 nm standard deviation σ) after 60 min surface reconstruction in ethanol at 40 °C, and to 28 nm (4 nm σ) after polymer residue dry etch in oxygen plasma (see Figure ), which is in line with previously reported results. [ 33 ] The SiN x film was patterned by initial dry reactive ion etching (RIE) in CHF 3 and N 2 plasma, and thereafter followed by wet etching in hydrofluoric acid (HF) (5%) to minimize damage to the InAs surface. The SiN x growth mask top opening average diameter was thereafter measured to 31 nm (5 nm σ).…”

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

“…The resulting self-assembled nanodomains can consist of morphologies ranging from cylinders to gyroids to spheres, depending on the predetermined self-assembly conditions [ 60 ]. In BCP lithography, one block can be selectively removed to leave an on-substrate etch masks; alternatively block selective insertion of metals from the vapour or solution phase can be used to create masks where both polymers can be removed simultaneously [ 61 , 62 ]. This ability to control specific properties such as morphology and feature size is the main advantage of BCP lithography as an aid for optical patterning of device elements for future IC developments [ 1 , 63 , 64 ].…”

Surface Nano-Patterning for the Bottom-Up Growth of III-V Semiconductor Nanowire Ordered Arrays

“…Block copolymer self-assembling consists of a spontaneous organization of polymer molecules into well-defined regular features in the 5–100 nm range, driven by the minimization of the free energy [ 158 ]. This technique has been applied to the realizations of InAs nanowire arrays [ 159 , 160 ]. This technique is still immature for the realization of engineered nanowires arrays, but it is a very promising candidate for low-cost substrate patterning over large areas [ 123 ].…”