High‐Throughput and Etch‐Selective Nanoimprinting and Stamping Based on Fast‐ Thermal‐Curing Poly(dimethylsiloxane)s

Abstract

Nanoimprint lithography (NIL) is a patterning technique that has emerged as one of the most promising technologies for high-throughput nanoscale replication. [1,2] Several applications in electronics, photonics, magnetic devices, and the biological field have been developed using this simple, low-cost, and high-resolution technique. In the biological field, DNA, [3] proteins, [4][5][6] and guides for molecular motors have been patterned; [7] nanowire arrays have been fabricated for electronic applications; [8] new magnetic devices, such as patterned magnetic media [9,10] and high density quantized magnetic discs, [11] have been engineered; and wire grid polarizers, [12,13] lightemitting diodes, [14,15] and diffractive optical elements [16] have been developed for photonics. The success of NIL as a next generation lithographic technique strongly depends on the research for new materials that are better suited as the nanoimprint resist. Because imprint lithography makes a conformal replica of surface relief patterns by mechanical embossing, the resist materials used in imprinting should be deformed easily under an applied pressure. The most commonly used materials in the original NIL scheme are thermal plastic polymers, which become viscous fluids when heated above their glass transition temperatures (T g ). However the viscosity of the heated polymers is typically high and thus the imprinting process requires significant pressure. In addition, these thermal plastic resists normally have a high tendency to stick to the mold because of non-optimized chemistry and orientation of the polymer backbone structures, which seriously affects the fidelity and quality of the pattern definition. Furthermore they do not offer the necessary etch resistance. Therefore, a nanoimprint resist system with combined mold-release and etch-resistance properties that allows fast and precise nanopatterning is highly desirable.Thermally curable monomers are very attractive materials for nanoimprint applications because they present in the liquid state, making it possible for them to be imprinted in a short period of time under low pressure and temperature, in sharp contrast to thermal plastic polymers. As one of these materials, poly(dimethylsiloxane) (PDMS) has previously been used by several research groups for micropatterning, mainly in the context of soft lithography, [17][18][19][20][21] and has found numerous applications in fields as diverse as microelectrochemical systems (MEMS), biotechnology, photonics, and nanoelectronics. In addition to its well known transparency to UV and visible light along with its good biocompatibility, it has a low surface energy (18-21 mN m -1 ) [22] that allows easy mold release without causing any structural damage to the imprinted structures; moreover, it posses a high resistance to oxygen plasma because of a higher silicon content. However, the PDMS material made from commercial Sylgard 184 as precursor is not suitable for nanoimprint applications because of two significant drawbacks. Firstly, its cur...

Carbon nanotube composite optoacoustic transmitters for strong and high frequency ultrasound generation

“…15 Then, the as-prepared CNTs were spin-coated with PDMS which has a modified composition to enhance the elastic modulus. 16 The cross-sectional view confirms that the CNT strands are dense near the substrate. The planar AuNP array in Fig.…”

Nanoimprint Lithography: Methods and Material Requirements

“…Details of these material properties can be found elsewhere. [76] The crosslinked PDMS structures could also be used as molds for imprinting other resist materials or as stamps for microcontact printing, especially when sub-microscale features are desired. For example, earlier work [76] shows that the replicated PDMS sample can be used as a stamp to pattern the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) with sub-micrometer features by using a polymer inking and stamping technique.…”

“…[75] A fast, thermal-curable liquid resist that can be imprinted under a low pressure with a high precision and throughput was recently developed in our group. [76] This system is based on the same hydrosilylation chemistry of siloxane polymers and consists of four basic chemical components: a vinyl-terminated PDMS polymer, a silyl-hydride-based (Si-H) dimethylsiloxane crosslinker, a platinum catalyst, and an inhibitor. The inhibitor is an unsaturated organic ester that keeps the catalyst inactive until the application of heat, which quickly deactivates the inhibitor and releases the catalyst in its active form.…”

Highly Versatile and Robust Materials for Soft Imprint Lithography Based on Thiol‐ene Click Chemistry

“…As a result, the simplicity and generality of the process highlighted here allows for high throughput screening of materials with multiple stamp arrays being fabricated without advanced instrumentation or highly specialized facilities. [23] The performance of these new materials can be visually appreciated in Figure 2, which shows the scanning electron microscope (SEM) image of the original silicon master ( Fig. 2A).…”