High-quality global hydrogen silsequioxane contact planarization for nanoimprint lithography

The authors present a novel global contact planarization technique based on the spin-on-glass material hydrogen silsequioxane (HSQ) and demonstrate its excellent performance on patterns of 70 nm up to several microns generated by UV-based nanoimprint lithography. The HSQ layer (∼165 nm) is spin coated on the imprinted organic layer and planarized by pressing it with a flat wafer at room temperature. Before retracting the planarization wafer, the HSQ is hardened by baking at 120 or 70 °C, depending on the underlying material. Fluorine-based reactive ion etching (RIE) is used to etch the HSQ (etch-back) down to the top of the features in the organic imprint layer. Subsequently, oxygen-based RIE is used to etch the organic imprint layer in the exposed regions, thereby transferring the imprinted pattern down to the substrate. The etch selectivity between the HSQ and the underlying layers is found to be more than 1:100, enabling very accurate pattern transfer with excellent critical dimension control and well-defined undercut profile suitable for further metal liftoff processes. The dependence of the contact planarization quality on the HSQ spinning speed and pressure is investigated, achieving a global planarization degree as good as 93%, an improvement of 45% compared to standard spin-coating planarization

Broadband transmission grating spectrometer for measuring the emission spectrum of EUV sources

Extreme ultraviolet (EUV) light sources and their optimization for emission within a narrow wavelength band are essential in applications such as photolithography. Most light sources however also emit radiation outside this wavelength band and have a spectrum extending up to deep ultraviolet (DUV) wavelengths. This out-of-band radiation can be hazardous in the rest of the lithography process, hence monitoring of it is necessary. In this article we present a broadband spectrometer based on a transmission grating for spectral monitoring of EUV sources from EUV to DUV wavelengths. The transmission geometry enables a compact design and a straightforward alignment. Measurements that were carried out with the spectrometer at two different EUV sources provide detailed spectral information that is immediately available for analysis and optimization of the source conditions

Nanostructured Polymer Brushes by UV-Assisted Imprint Lithography and Surface-Initiated Polymerization for Biological Functions

Functional polymer brush nanostructures are obtained by combining step-and-flash imprint lithography (SFIL) with controlled, surface-initiated polymerization (CSIP). Patterning is achieved at length scales such that the smallest elements have dimensions in the sub-100 nm range. The patterns exhibit different shapes, including lines and pillars, over large surface areas. The platforms obtained are used to selectively immobilize functional biomacromolecules. Acrylate-based polymer resist films patterned by SFIL are first used for the selective immobilization of ATRP silane-based initiators, which are coupled to unprotected domains of silicon substrates. These selectively deposited initiators are then utilized in the controlled radical SIP of poly(ethylene glycol)methacrylates (PEGMA). Nanostructured brush surfaces are then obtained by removal of the resist material. The areas previously protected by the SFIL resist are passivated by inert, PEG-based silane monolayers following resist removal. PEGMA brush nanostructures are finally functionalized with biotin units in order to provide selective attachment points for streptavidin proteins. Atomic force microscopy and fluorescence spectroscopy confirm the successful immobilization of streptavidin molecules on the polymer grafts. Finally, it is demontrated that this fabrication method allows the immobilization of a few tens of protein chains attached selectively to brush nanostructures, which are surrounded by nonfouling PEG-functionalized areas

A common gate thin film transistor on poly(ethylene naphthalate) foil using step-and-flash imprint lithography

\u3cp\u3eIn this paper the fabrication of flexible thin film transistors (TFTs) on poly(ethylene naphthalate) foil is reported, with the source-drain layer patterned by step-and-flash imprint lithography (SFIL) as a first step towards fully UV-imprinted TFTs. The semiconductor was deposited by inkjet printing of a blend of TIPS-pentacene/polystyrene. The bottom contact, bottom gate TFTs were fabricated with the foil reversibly glued to a carrier, enhancing the dimensional stability and flatness of the foil to result in a thinner and more homogeneously distributed residual layer thickness. The obtained performance of the TFT devices, showing a mobility of μ = 0.56 cm\u3csup\u3e2\u3c/sup\u3e V\u3csup\u3e-1\u3c/sup\u3e s\u3csup\u3e-1\u3c/sup\u3e with an on/off ratio of >10\u3csup\u3e7\u3c/sup\u3e and near-zero threshold voltage, was found to be in good agreement with similar, photolithographically patterned state-of-the-art devices recently reported in literature. The results presented here show the feasibility of SFIL as a roll-to-roll compatible and down scalable patterning technique on flexible PEN foil for the fabrication of bottom-gate, bottom-contact flexible high-quality TFTs.\u3c/p\u3

Flexible thin-film transistors using multistep UV nanoimprint lithography

A multistep imprinting process is presented for the fabrication of a bottom-contact, bottom-gate thin-film transistor (TFT) on poly(ethylene naphthalate) (PEN) foil by patterning all layers of the metal-insulator-metal stack by UV nanoimprint lithography (UV NIL). The flexible TFTs were fabricated on a planarization layer, patterned in a novel way by UV NIL, on a foil reversibly glued to a Si carrier. This planarization step enhances the dimensional stability and flatness of the foil and thus results in a thinner and more homogeneous residual layer. The fabricated TFTs have been electrically characterized as demonstrators of the here developed fully UV NIL-based patterning process on PEN foil, and compared to TFTs made on Si with the same process. TFTs with channel lengths from 5 μm down to 250 nm have been fabricated on Si and PEN foil, showing channel length-dependent charge carrier mobilities, μ, in the range of 0.06-0.92 cm2 V-1 s -1 on Si and of 0.16-0.56 cm2 V-1 s -1 on PEN foil