Nanoimprint lithography (NIL) is a method of fabricating nanometer-scale patterns. It is a simple nanolithography process with low cost, high throughput and high resolution. It creates patterns by mechanical deformation of imprint resist and subsequent processes. The imprint resist is typically a monomer or polymer formulation that is cured by heat or UV light during the imprinting. Adhesion between the resist and the template is controlled to allow proper release.
History Nanoimprint lithography was invented by Stephen Y. Chou, who also introduced the terms nanoimprint lithography, nanoimprint, and imprint lithography. The method, its key underlying principles, and the discoveries that led to the invention were first disclosed in a 1995 Applied Physics Letters paper
and a 1995 patent application (later granted) .
Before this work, embossing techniques produced (1) only micron-scale features and (2) patterns in bulk materials or thick polymer films, leaving a thick residual layer. These approaches were unsuitable for nanopatterning because their feature pitches were larger—i.e., coarser (worse)—than the optical lithography resolution available in 1995 (≈350 nm half-pitch),Semiconductor Industry Association (SIA), National Technology Roadmap for Semiconductors (1994 or 1995 edition) and because they neither used a thin film on a substrate nor cleared the material beneath mold protrusions, thereby failing to produce a near-zero residual layer and a free-standing relief profile—both essential for nanolithography and many direct nanopatterning applications.
In the 1995 Applied Physics Letters paper, Chou introduced a new embossing approach using an ultra-thin polymer film (~50 nm) on a substrate and a mold with protrusions much deeper than the film thickness, with the mold material thermally matched to the substrate—rather than the thick polymer films, relatively shallow mold protrusions, and thermally mismatched nickel molds typical of earlier embossing methods. Using this approach, the study experimentally demonstrated that (a) sub-10-nm features—more than 30 times smaller than the optical lithography resolution limit at the time—could be produced by mechanical embossing, and (b) the mold protrusions displaced nearly all of the polymer beneath them, yielding an almost zero residual layer and a freestanding polymer profile (“fully transferred” patterns). These results constituted the first discovery that mechanical embossing could achieve nanometer-scale patterning with near-zero residual layers in thin resist films on a substrate, establishing, in principle, a new nanolithography and direct nanopatterning method for semiconductor integrated circuits, photonic devices, magnetic devices, and other nanostructures. Together with Chou's subsequent foundational work, the 1995 discoveries led to the invention of nanoimprint lithography and launched the field.
Following its introduction, nanoimprint lithography initially faced significant skepticism, as mechanical deformation–based patterning was widely viewed as impractical at nanometer scales. From 1995 to mid-1998, there were nearly no publications on the technique from groups outside the originating laboratory, whereas Chou and his students published numerous papers over the same period
and presented the work at many conferences and workshops. These publications and presentations, including one paper in Science, described advancement in solving key challenges, including new imprint press that does not use heavy solid plates, improved resist materials, and approaches achieved smaller feature sizes, improved uniformity, and higher throughput (including roller nanoimprint ). They also reported the first nanoimprint fabrications of various nanodevice, including nanotransistors, nanophotonic devices, and nanomagnetic structures. These advances—together with significant support from a few early sponsors and believers—helped dispel initial doubts. By late 1998, other groups began publishing in the field, marking the rise of a global community that turned the “impossible” into reality and propelled nanoimprint into one of the most transformative nanofabrication technologies of the 21st century.
Since 2009, the first nanoimprint press has been displayed at the Deutsches Museum in Munich—one of the world's major science and technology museums—in recognition of its historical and industrial importance. In 2003, MIT Technology Review named nanoimprint lithography one of the “10 Emerging Technologies That Will Change the World,” highlighting its early impact and potential.https://www.technologyreview.com/10-breakthrough-technologies/2003/ At the 24th International Conferences on Nanoimprint and Nanoprint Technology in 2025 (NNT2025), it celebrated 30 years of nanoimprint: reflected on nanoimprint's history, showcased the field's progress, awarded the key contributors to nanoimprint, and summarized nanoimprint impacts to a very wide range of fields and its future .https://nntconf.org/https://nntconf.org/awards/
Processes There are many but the most important processes are the following three:
thermoplastic nanoimprint lithography photo nanoimprint lithography resist-free direct thermal nanoimprint lithography.
Thermoplastic nanoimprint lithography Thermoplastic nanoimprint lithography (T-NIL) is the earliest nanoimprint lithography developed by Prof. Stephen Chou's group. In a standard T-NIL process, a thin layer of imprint resist (thermoplastic polymer) is spin-coated onto the sample substrate. Then the mold, which has predefined topological patterns, is brought into contact with the sample, and they are pressed together under certain pressure. When heated up above the glass-transition temperature of the polymer, the pattern on the mold is pressed into the softened polymer film. After being cooled down, the mold is separated from the sample, and the pattern resist is left on the substrate. A pattern transfer process (reactive ion etching, normally) can be used to transfer the pattern in the resist to the underneath substrate.
Alternatively, cold welding between two metal surfaces could also transfer low-dimensional nanostructured metal without heating (especially for critical sizes less than ~10 nm). Three-dimensional structures can be fabricated by repeating this procedure. The cold-welding approach has the advantage of reducing surface contact contamination or defect due to no heating process, which is a main problem in the latest development and fabrication of organic electronic devices and novel solar cells.
Photo nanoimprint lithography In photo nanoimprint lithography (P-NIL), a UV-curable liquid resist is applied to the sample substrate, and the mold is normally made of transparent material like fused silica or PDMS. After the mold and the substrate are pressed together, the resist is cured in UV light and becomes solid. After mold separation, a similar pattern transfer process can be used to transfer the pattern in resist onto the underneath material. The use of a UV-transparent mold is difficult in vacuum, because a vacuum chuck to hold the mold would not be possible.
Resist-free direct thermal nanoimprint lithography Different from the above-mentioned nanoimprint methods, resist-free direct thermal nanoimprint does not require an extra etching step to transfer patterns from imprint resists to the device layer.
In a typical process, photoresist patterns are first defined using photolithography. A polydimethylsiloxane (PDMS) elastomer stamp is subsequently replica-molded from the resist patterns. Further, a single-step nanoimprint directly molds thin film materials into desired device geometries under pressure at elevated temperatures. The imprinted materials should have suitable softening characteristics in order to fill up the pattern. Amorphous semiconductors (for example, chalcogenide glass) demonstrating high refractive index and wide transparent window are ideal materials for the imprint of optical/photonic device.
This direct imprint patterning approach offers a monolithic integration alternative with potentially improved throughput and yield, and may also enable roll-to-roll processing of devices over large substrate areas inaccessible using conventional lithographic patterning methods.
In thermal nanoimprint methods the trade-off between full pattern transfer and deforming the substrate creates limitations in quality of fabrication. Few approached have created other solvent-assisted methods for direct resistless nanoimprinting processes.
Schemes
Full-wafer nanoimprint In a full-wafer nanoimprint scheme, all the patterns are contained in a single nanoimprint and transferred in a single imprint step. This allows a high throughput and uniformity. An at least diameter full-wafer nanoimprint with high fidelity is possible.
To ensure the pressure and pattern uniformities of full-wafer nanoimprint processes and prolong the mold lifetime, a pressing method utilizing isotropic fluid pressure, named air-cushion press (ACP) by its inventors, is developed and being used by commercial nanoimprint systems. Alternatively, roll-on technologies (e.g. roll to plate) in combination with flexible stampers (e.g. PDMS) have been demonstrated for full-wafer imprint.
Step-and-repeat nanoimprint Nanoimprint can be performed in a way similar to the step-and-repeat optical lithography. The imprint field (die) is typically much smaller than the full-wafer nanoimprint field. The die is repeatedly imprinted to the substrate with certain step size. This scheme is good for nanoimprint mold creation.
Applications Nanoimprint lithography has been used to fabricate devices for electrical, optical, photonic and biological applications. For electronics devices, NIL has been used to fabricate MOSFET, O-TFT, and single-electron memory. For optics and photonics, intensive study has been conducted in fabrication of subwavelength resonant grating filter, surface-enhanced Raman spectroscopy (SERS) sensor, polarizers, waveplate, anti-reflective structures, integrated photonics circuit and plasmonic devices by NIL. In the context of opto-electronic devices such as LEDs and solar cells, NIL is being investigated for out- and incoupling structures. Sub-10 nm nanofluidic channels had been fabricated using NIL and used in DNA stretching experiment. Currently, NIL is used to shrink the size of biomolecular sorting device an order of magnitude smaller and more efficient.
Benefits
A key benefit of nanoimprint lithography is its sheer simplicity. The single greatest cost associated with chip fabrication is the optical lithography tool used to print the circuit patterns. Optical lithography requires high-power excimer lasers and immense stacks of precision-ground lens elements to achieve nanometer-scale resolution. There is no need for complex optics or high-energy radiation sources with a nanoimprint tool. There is no need for finely tailored photoresists designed for both resolution and sensitivity at a given wavelength. The simplified requirements of the technology lead to its low cost.
Silicon master molds can be used up to a few thousands imprints, while nickel molds can last for up to ten thousand cycles.
Imprint lithography is inherently a three-dimensional patterning process. Imprint molds can be fabricated with multiple layers of topography stacked vertically. Resulting imprints replicate both layers with a single imprint step, which allows chip manufactures to reduce chip fabrication costs and improve product throughput.