Nanoimprint lithography for large-scale
fabrication of micro- and nano-structures
Patrícia C. Sousa*1, José Fernandes1, Joana Santos1, Jordi Llobet1, Hélder Fonseca1,
Carlos Calaza1 and João Gaspar1
1

International Iberian Nanotechnology Laboratory
Av. Mestre José Veiga s/n4715-330 Braga, Portugal
E-mail: patricia.sousa@inl.int

Nanoimprint lithography is a high resolution patterning technique in which a master with nanoand/or micrometer scale features can be used to replicate several times a specific pattern. Thecombination of nanometer scale resolution, high throughput and low cost of fabrication makes thisnanopatterning process ideal for large volume manufacturing [1]. Since the seminal work of Chouet al. [2, 3], nanoimprint lithography has quickly evolved to become one of the most promising
nanopatterning techniques, widely employed in areas such as semiconductors, for fabrication ofmagnetic disk storage devices, photonics, for nanopatterned solar cells, biosensing, for detectionof various biomolecules, as well as in micro- and nanofluidics, to cite just few applications [4].
In this work, we present the complete fabrication method used for large volume manufacturing ofcomplex nano-structures at 8 inch wafer scale. In particular, a large area of nano-wells, requiredfor biochemical detection as well as manipulation of nanoparticles [5] was fabricated.
The fabrication process starts with the creation of a silicon mold by conventional micromachining
methods, namely e-beam and/or direct writing laser lithography followed by silicon reactive ionetching. The silicon mold is then used to obtain an Intermediate Polymer Stamp (IPS®, Obducat)
used for pattern replication under nanoimprint lithography using the Simultaneous Thermal andUV (STU®, Obducat) technology. The use of the intermediate stamp allows a longer lifetime ofthe silicon mold (only used to create the IPS®) and allows the fabrication of the same structures
existing in the original silicon mold with high fidelity. In a first step the IPS® is created from thesilicon mold by means of thermal nanoimprint, and in a second step, this IPS® is used to pattern
the STU® resist coated on test wafers with a simultaneous thermal and UV-curing process. In thiswork, a silicon mold composed of nano-wells has been employed. Wells are 1μm in diameter andabout 300 nm in depth, and are arranged in a hexagonal lattice with 2μm pitch, as shown in Fig.
1(a). The same structures were patterned by NIL (Eitre®8) in STU® resist using the IPS® obtained
from the silicon mold and then, the silicon substrates were etched in an Inductively Coupled
Plasma Etching – Reactive Ion Etching (ICP-RIE) tool to create a replica of the original nanowells as presented in Fig. 1(b). A comparison between Fig. 1(a) and Fig. 1(b) shows a goodagreement between the dimensions of the original silicon master and the replica obtained using theNIL process. Comprehensive analysis will be completed to assess consistency of the replica atwafer scale, as well as the possible consistency degradation related to the repeated use of a sameIPS® for the NIL process.
This work illustrates how a single nanoimprinting setup can be used for the fabrication of an IPS®
suitable for the STU® NIL process, leading to an inexpensive path for the large volume fabricationof devices with high resolution features, by extending the lifetime of original silicon molds.

(a)(b)Figure 1. Original silicon mold (a) and silicon replica (b) obtained using the STU® nanoimprint
lithography process.

References:[1] Schift, H. and Kristensen, A.; “Nanoimprint Lithography”, Handbook of nano-Technology,
Bhushan, B. ed., Springer, New York, 239-278.
[2] Chou, S. Y., Krauss, P. R. and Renstrom, P. J.; “Imprint of sub-25 nm vias and trenches inpolymers” Appl. Phys. Lett. 1995 67, (21) 3114-3116.
[3] Chou, S. Y., Krauss, P. R. and Renstrom, P. J.; “Nanoimprint lithography” JVST B Microelectronics and Nanometer Structures 1996 14, (6) 4129-4133.
[4] Traub, M. C., Longsine, W. and Truskett, Van N.; “Advances in Nanoimprint Lithography”
Annu. Rev. Chem. Biomol. Eng. 2016 7, 583–604.
[5] Tu, L., Li, X., Bian, S., Yu, Y., Li, J., Huang, L., Liu,P., Wu, Q. and Wang, W.;” Label-freeand real-time monitoring of single cell attachment on template-stripped plasmonic nano-holes”
Scientific Reports 2017 7, 11020.