Nanoimprint Lithography Tool Research Articles

Development and Implementation of a Rotating Nanoimprint Lithography Tool for Orthogonal Imprinting on Edges of Curved Surfaces

Uniform molding and demolding of structures on highly curved surfaces through conformal contact is a crucial yet often-overlooked aspect of nanoimprint lithography (NIL). This study describes the development of a NIL tool and its integration into a nanopositioning and nanomeasuring machine to achieve high-precision orthogonal molding and demolding for soft ultraviolet-assisted NIL (soft UV-NIL). The process was implemented primarily on the edges of highly curved plano-convex substrates to demonstrate structure uniformity on the edges. High-resolution nanostructures of sub-200-nm lateral dimension and microstructures in the range of tens of microns were imprinted. However, the nanostructures on the edges of the large, curved substrates were difficult to characterize precisely. Therefore, microstructures were used to measure the structure fidelity and were characterized using profilometry, white light interferometry, and confocal laser scanning microscopy. Regardless of the restricted imaging capabilities at high inclinations for high-resolution nanostructures, the scanning electron microscope (SEM) imaging of the structures on top of the lens substrate and at an inclination of 45° was performed. The micro and nanostructures were successfully imprinted on the edges of the plano-convex lens at angles of 45°, 60°,and 90° from the center of rotation of the rotating NIL tool. The method enables precise imprinting at high inclinations, thereby presenting a different approach to soft UV-NIL on curved surfaces.

33‐6: Roll‐To‐Plate Nano‐Imprint Lithography for High‐Volume Production of AR Glasses: Equipment, Materials, and Processes

Today, the prevailing AR‐glasses displays are using waveguides. The light in‐ & outcoupling structures that these glasses contain can be made by UV nanoimprint lithography. Nanoimprint lithography tools have typical cycle times of around 40 imprints per hour, roughly resulting in 8M eyepieces per year made on 300mm wafers. To serve the projected mass market adoption, hundreds of imprint tools will be needed. An important question is how the eyepieces can be made more efficiently and cost‐effectively. The Morphotonics' Roll‐to‐Plate imprint technology enables high volume production, having the opportunity for large‐area imprinting, manufacturing multiple products in a single imprint step.

Overlay improvement in nanoimprint lithography for 1×-nm patterning

Nanoimprint lithography (NIL) is becoming a promising technique for fine-patterning with a lower cost than other lithography techniques. High overlay accuracy is one of the issues in NIL. Using die-by-die alignment with moiré fringe detection, an NIL alignment measurement accuracy below 1 nm and an overlay accuracy below 5 nm have been reported. On the other hand, the requirement for overlay in 2020 is estimated to be 3–4 nm for dynamic random access memory, flash and logic devices. In order to make the overlay accuracy requirement qualify from the semiconductor industry, a lot of technology enhancements, such as the improvement of overlay control accuracy for NIL-tools, image placement accuracy improvement for NIL templates, mix and match technique of NIL, and other lithography tools such as immersion exposure ones, are needed. In this paper, the authors describe the evaluation of the NIL overlay performance using up-to-date NIL tools, and discuss the potentials of NIL overlay in the future. Alignment accuracy, precision, and overlay correction performance of NIL tools, NIL-to-NIL and NIL-to-optical lithography tool distortion matching performance and overlay error structure analysis, are discussed. From these analyses based on NIL overlay data, the authors discuss the possibility of NIL overlay evolution to realize the adaptation to mass production for the 1×-nm device.

Theory and simulations of peel demolding for large-area nanoimprint lithography

Nanoimprint lithography (NIL) is an emerging nanopatterning approach for producing large-area micro/nano scale structures with low cost, high throughput and high resolution. Demolding has now been considered as one of the most challenging issues for large area NIL, and a bottleneck hindering the industrialization of full wafer NIL. Peel demolding mode has been proven to be an effective way implementing large area nanoimprinting. This paper investigated the theoretical model and numerical simulation of peel demolding for large are NIL. A general model estimating demolding force was established based on the combination of the strain energy method and the conservation of energy in demolding stage. The required separating force for vertical demolding of grating patterns was achieved using the proposed model. Furthermore, the influence of the properties of mold materials and the aspect ratio of feature patterns for peel demolding was revealed by numerical simulation using ABAQUS software. These findings are valuable in providing a theoretical basis for large area NIL, optimizing demolding process and further enhancing the performance of full wafer NIL tool.

Fabrication of a nano-scale embedded metal electrode in flexible films by UV/thermal nanoimprint lithography tools

Nanoimprint lithography (NIL) which is well-known as a type of next-generation lithography, is a promising technology to produce sub-50 nm half-pitch features on several types of substrates. Particularly, ultraviolet (UV) nano-imprint lithography technology has the advantages of a simple process with low pressure of less than room temperature, a low cost, high replication fidelity, and relatively high throughput [1,2]. Recently, many researchers have applied the NIL technique to fabricate metal patterns on a flexible film substrate. Although a flexible film as a substrate has many advantages, most types of flexible polymer film incur weakness caused by the chemicals during the metal lift-off and/or metal etching processes. In this paper, a fabrication method is proposed to create nanoscale metal electrode patterns on a UV-curable polyurethane resist using a UV/thermal nanoimprint lithography processes. A replica fabrication process using the fabricated polyurethane stamp is also proposed. Second- and the third-generation replicas with 30 and 100 nm dot patterns are fabricated using UV and thermal nanoimprint lithography tools.

Nanoimprint lithography technology with automatic alignment

Nanoimprint lithography (NIL) is recognized as one of the most promising candidates for the next generation lithography (NGL) to obtain sub-100 nm patterns because of its simplicity, high-throughput and low-cost. While substantial effort has been expending on NIL for producing smaller and smaller feature sizes, considerably less effort has been devoted to the equally important issue—alignment between template and substrate. A homemade prototype nanoimprint lithography tool with a high precision automatic alignment system based on Moire signals is presented. Coarse and fine pitch gratings are adopted to produce Moire signals to control macro and micro actuators and enable the substrate to move towards the desired position automatically. Linear motors with 300 mm travel range and 1 μm step resolution are used as macro actuators, and piezoelectric translators with 50 μm travel range and 1 nm step resolution are used as micro actuators. In addition, the prototype provides one translation (z displacement) and two tilting motion(α and β ) to automatically bring uniform intact contact between the template and substrate surfaces by using a flexure stage. As a result, 10 μm coarse alignment accuracy and 20 nm fine alignment accuracy can be achieved. Finally, some results of nanostructures and micro devices such as nanoscale trenches and holes, gratings and microlens array fabricated using the prototype tool are presented, and hot embossing lithography, one typical NIL technology, are depicted by taking nanoscale gratings fabrication as an example.

NIL—a low-cost and high-throughput MEMS fabrication method compatible with IC manufacturing technology

Current MEMS fabrication technology cannot satisfy the simultaneous needs of 3D structure fabrication and compatibility with IC manufacturing technology, which have impeded the development of MEMS industrialization to a certain extent. Nanoimprint lithography (NIL) provides a new MEMS fabrication method that is compatible with IC manufacturing technology and bears high throughput and low cost. This paper presents an in-house prototype NIL tool with a high precision automatic alignment system based on moiré fringe signals. Some printing results of nanostructures or micro-devices using the prototype are presented, and hot embossing lithography, one typical NIL technology is depicted in detail by taking microlens array fabrication as an example. High fidelity and fine uniformity demonstrate NIL will be a new method to fabricate 3D structures of MEMS.

Polyvinyl alcohol templates for low cost, high resolution, complex printing

Templates for imprint lithography and MxL (molecular transfer lithography) are generated by adhesion of a spin-cast film of polyvinyl alcohol (PVA) to a carrier comprised of materials selected for conformability or distortion reduction. Template formation using both polymeric carrier materials and rigid materials, including quartz and glass carrier materials, is demonstrated. The absence of a carrier material altogether to form a suspended thin film is shown to be feasible. The rigid template material is formed by bonding the PVA patterned film to a rigid carrier while still connected to the master pattern, and it is demonstrated that separation occurs at the PVA-silicon master pattern interface. Form factors for the templates include a 25mm×25mm patterned film attached to a 65mm×65mm glass substrate, a full 100 mm pattern bonded to a quartz substrate, and a 100 mm mask of Mylar™ bonded with a patterned PVA film for MxL applications. These carrier materials are developed in a form factor compatible with commercial nanoimprint lithography tools, and for standard contact aligners adapted to perform MxL processing.