In UV-NIL, a substrate is spin coated or drop dispensed with a UV-curable monomer or oligomer. Imprinting is carried out with a transparent template (quartz glass or soft working stamps) and the imprinted structures are cured by UV-light exposure, which cross-links the resist. Subsequently, the template is released from the imprinted substrate. The use of quartz glass stamps is regarded as hard UV-NIL whereas the use of soft working stamps refers to soft UV-NIL.
EVG’s strongest differentiation factor in UV- nanoimprinting technology lies in its SmartNIL technology. SmartNIL enables manufacturing of extremely small features down to less than 40 nm, a wide range of structure sizes and shapes (including 3D) and nanopatterning of high-topography or rough surfaces. Since SmartNIL incorporates multiple-use soft stamp processing, it enables unmatched throughput with considerable cost-of-ownership advantages while preserving scalability and maintenance-friendly operation. In addition, the lifetime of the master template is extended to periods comparable to masks used for optical lithography. EVG’s SmartNIL redeems the long-term promise of nanoimprinting being a low-cost and high-volume alternative lithography technology for mass manufacturing of micro- and nanoscale structures.
Full-Field Large-Area UV-Nanoimprinting
A dispensed UV-curable material is imprinted at a pre-programmed contact force with UV-transparent stamps. UV irradiation cures the polymer. Both soft and hard stamps can be used on EVG systems. UV-transparent hard stamps are usually made of quartz glass (SiO2). Soft stamps are similar to those used in micro contact printing (e.g. PDMS) where the stamp is mounted on a thin/conformal or a thick/rigid backplane. Soft stamps are typically used for large area imprinting applications. The release process, after curing, is supported by an anti-sticking layer (only with hard stamps) as well as by a non-parallel release mechanism.
Step-and-Repeat Large-Area UV-Nanoimprinting
The EVG770 NIL Stepper is designed for step-and-repeat UV-NIL processes and is compatible for 100 mm to 300 mm wafers. The special features of the EVG770 include a dual-stage alignment approach and the capability to imprint in a lower pressure environment (patented technology), which enables greater pattern fidelity compared to other technical solutions that imprint at ambient pressure. The step-and-repeat NIL system achieves < 500 nm overlay alignment accuracy and a lithography resolution in the sub-30 nm range.
The EVG600 Series precision alignment systems support stamp-to-substrate alignment for subsequent hot embossing. Stamp and substrate are brought in contact inside an EVG500 Series vacuum chamber. A precisely controlled temperature profile (typically up to 350°C, the system supports up to 650°C) and contact force sequence (up to 360 kN) create an imprint of the stamp on the substrate. Imprint areas up to 300 mm in diameter with high resolution features down to 50 nm have been demonstrated on the EVG500 hot embossing systems. Typical stamps are made out of Si, SiO2 or metals (e.g. Ni). Substrates are typically polymer substrates or coated polymers on semiconductor wafers. The high-temperature option enables imprinting into materials where elevated temperatures are needed (e.g. glass substrates).
Micro Contact Printing (µ-CP)
In a µ-CP process, inked chemicals are transferred from an elastomeric stamp to a novel metal surface to build up a Self Assembling Monolayer (SAM). A SAM can be used as an etching mask or act as a precursor for binding specific molecules covalently. In most cases, thioles are transferred to gold surfaces on silicon wafers. Other common inks used are proteins for biological or biotechnological applications.
Honeycomb texturing of
Multicrystalline Silicon (mc-Si)
Courtesy of Fraunhofer ISE
50 nm resolution pattern utilizing
Courtesy of Quantiscript Inc.
12.5 nm half pitch L/S test structures
20 µm TOPAS hot embossed micro fluidic structures utilizing soft working stamp polymers
50 nm hot embossed resolution lines replicated with soft working stamps Source: EVG