Bottom-Up Nanofabrication with Extreme-Ultraviolet Light: Metal–Organic Frameworks on Patterned Monolayers

Abstract

The fabrication of integrated circuits with ever smaller (sub-10 nm) features poses fundamental challenges in chemistry and materials science. As smaller nanostructures are fabricated, thinner layers of materials are required, and surfaces and interfaces gain a more important role in the formation of nanopatterns. We present a new bottom-up approach in which we use the high optical resolution offered by extreme ultraviolet (EUV) lithography to print patterns on self-assembled monolayers (SAMs). Upon radiation, low-energy electrons induce chemical changes in the SAM so that the projected image is transferred to the substrate surface. We use the chemical differences between exposed and unexposed regions to promote a selective growth of hybrid structures that can act as an etch-resistant layer for further pattern transfer or can be used as functional nanostructures. The EUV doses required to promote selective growth on exposed areas are close to industrial requirements. Furthermore, this method allows for the independent tuning of different steps in the EUV lithography process (photo-induced chemistry, spatially resolved chemical contrast, and formation of nanopatterns), an advantage over current resists, in which the same material plays all roles.

Tuning interfacial interactions for bottom‐up assembly of surface‐anchored metal‐organic frameworks to tailor film morphology and pattern surface features

“…Chemically patterned SAMs composed primarily of ODT or MHDA regions have been utilized to direct the assembly of surMOF films inhibiting and promoting film growth. [14][15][16][17][18][19] Previous research surveyed surMOFs formed by this method primarily utilizing SEM and typically investigating surMOF film thicknesses greater than 100 nm on chemically patterned SAM features that are 10-100 µm in width. [15][16][17][18][19] The investigation herein regarding surMOF growth on codeposited SAMs is especially relevant for directed surMOF assembly on µCP-patterned SAMs because the initially patterned chemical region often has some of the secondary component mixed within during the exposure of the sample to the secondary chemical component.…”

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25] To produce surface-anchored MOFs (surMOFs) with controlled thickness and surface coverage, films are commonly deposited by introducing the metal ion source and the organic linker in an alternating, sequential, solution-phase deposition process. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] For the incorporation of nanostructured MOFs into device architectures, design rules must be developed that allow for the directed formation of surMOF film structures with regard to patterning features and tailoring morphological parameters, such as film roughness or grain size. Toward the development of these rules to control the structure of surMOF films, this study investigates the impact of modifying the chemical composition of the coating on the substrate that anchors the MOF and explores chemical patterning techniques to selectively direct film formation.…”

“…Patterned SAMs generated by chemical patterning techniques, such as microcontact printing (µCP), [28][29][30][31][32][33] have been used to selectively direct the assembly of surMOF structures onto carboxylterminated regions and inhibit growth on methyl-terminated regions. [14][15][16][17][18][19] Typically, the chemical regions investigated are greater than 10 µm in width with surMOF film thicknesses greater than 100 nm, and characterization is done by scanning electron microscopy (SEM), which does not have the same nanoscale morphological characterization capabilities as AFM. A common challenge associated with chemical patterning, and µCP especially, is that it is common to have mixed chemical functionalities within certain regions of the pattern.…”

“…These properties for the MOF-14-based film differ from those observed for other surMOF systems in the literature. [12][13][14][15][16][17][18][19][20][21][22][23][24] Typically, surMOF film growth follows a Volmer-Weber growth mechanism with isolated crystallite nucleation and growth that does not continuously coat the underlying substrate until the film is greater than 100-nm thick. Compared to the MOF-14 system, these other surMOF films created by Volmer-Weber growth do not have nanoscale tunability in film thickness; they are considerably thicker, and their morphology is rougher with a higher defect density.…”

“…[1][2][3][4][5][6][7][8][9][10][11] By anchoring an MOF to a surface, the versatility and potential of this high surface area, supramolecular material can be directly integrated into architectures specific to the desired application. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] To produce surface-anchored MOFs (surMOFs) with controlled thickness and surface coverage, films are commonly deposited by introducing the metal ion source and the organic linker in an alternating, sequential, solution-phase deposition process. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] For the incorporation of nanostructured MOFs into device architectures, design rules must be developed that allow for the directed formation of surMOF film structures with regard to patterning features and tailoring morphological parameters, such as film roughness or grain size.…”