Polyarylenesulfonium Salt as a Novel and Versatile Nonchemically Amplified Negative Tone Photoresist for High-Resolution Extreme Ultraviolet Lithography Applications

The present report demonstrates the potential of a polyarylenesulfonium polymer, poly[methyl(4-(phenylthio)-phenyl)sulfoniumtrifluoromethanesulfonate] (PAS), as a versatile nonchemically amplified negative tone photoresist for next-generation lithography (NGL) applications starting from i-line (λ ∼ 365 nm) to extreme ultraviolet (EUV, λ ∼ 13.5 nm) lithography. PAS exhibited considerable contrast (γ), 0.08, toward EUV and patterned 20 nm features successfully.

Electric-Field-Induced Nanoscale Surface Patterning in Mexylaminotriazine-Functionalized Molecular Glass Derivatives

Nanoscale surface patterns were observed in thin films of mexylaminotriazine-functionalized glasses containing polar groups upon the application of an electric field at temperatures over their glass transition temperatures (Tg). This phenomenon occurred due to the surface deformation process initiated by external electric field instabilities on the films. The minimal surface deformation temperature (Tdewet) relative to Tg was found to increase as a function of the polarity of the substituents and the surface pattern roughness was observed to increase linearly with temperature for a fixed electric field and exposure time. Reversal of the electrical field polarity and the use of both hydrophilic and hydrophobic substrates did not significantly change the surface deformation behavior of the films, which is due to the deposition of charges at the free interface. The application of a mask between the electric field electrodes allowed to selectively pattern areas that are exposed. Furthermore, it was observed that this surface deformation behavior was reversible, since heating the films to a temperature above Tg in the absence of an electric field caused the erasure of all surface patterns.

Patterning highly ordered arrays of complex nanofeatures through EUV directed polarity switching of non chemically amplified photoresist

Given the importance of complex nanofeatures in the filed of micro-/nanoelectronics particularly in the area of high-density magnetic recording, photonic crystals, information storage, micro-lens arrays, tissue engineering and catalysis, the present work demonstrates the development of new methodology for patterning complex nanofeatures using a recently developed non-chemically amplified photoresist (n-CARs) poly(4-(methacryloyloxy)phenyl)dimethylsulfoniumtriflate) (polyMAPDST) with the help of extreme ultraviolet lithography (EUVL) as patterning tool. The photosensitivity of polyMAPDST is mainly due to the presence of radiation sensitive trifluoromethanesulfonate unit (triflate group) which undergoes photodegradation upon exposure with EUV photons, and thus brings in polarity change in the polymer structure. Integration of such radiation sensitive unit into polymer network avoids the need of chemical amplification which is otherwise needed for polarity switching in the case of chemically amplified photoresists (CARs). Indeed, we successfully patterned highly ordered wide-raging dense nanofeatures that include nanodots, nanowaves, nanoboats, star-elbow etc. All these developed nanopatterns have been well characterized by FESEM and AFM techniques. Finally, the potential of polyMAPDST has been established by successful transfer of patterns into silicon substrate through adaptation of compatible etch recipes.

Influence of physical ageing on rim instability during solvent-induced dewetting of a thin polymer film

Combining experiments with molecular dynamic simulation to examine the influence of physical ageing on rim instability during solvent-induced dewetting.

Unusual dewetting of thin polymer films in liquid media containing a poor solvent and a nonsolvent

We investigate the control of pattern size and kinetics in spontaneous dewetting of thin polymer films (polystyrene) that are stable to thermal annealing by annealing in a poor solvent (acetone)/nonsolvent (ethanol or n-hexane) liquid mixture. Dewetting occurs by the formation and growth of circular holes that coalesce to form droplets. The influence of the nature and the volume fraction of the nonsolvents on the contact angle of polymer droplets, number density of holes, and the kinetics of holes formation and growth is studied. Addition of ethanol greatly increases the hole density and slows down the kinetics substantially, while affecting only a small change in wettability. n-Hexane addition shows an interesting nonmonotonic response in decreasing the hole density and contact angle in the volume fraction range of 0-0.3 but an opposite effect beyond that. Although the two nonsolvents chosen cannot by themselves induce dewetting, their relative affinity for the solid substrate vis-à-vis acetone can strongly influence the observed dewetting scenarios that are not understood by the existing theoretical considerations. n-Hexane, for example, has great affinity for silicon substrate. In addition to the changes in wettability, viscosity, and film interfacial tension engendered by the nonsolvents, the possibility of the formation of adsorbed liquid layers at the substrate-polymer interface, which can modify the interfacial friction and slippage, needs to be considered.

Mechanically modulated dewetting by atomic force microscope for micro- and nano- droplet array fabrication

Organizing a material into well-defined patterns during the dewetting process provides an attractive micro-/nano-fabrication method without using a conventional lithographic process, and hence, offers potential applications in organic electronics, optics systems, and memory devices. We report here how the mechanical modification of polymer surface by an Atomic Force Microscope (AFM) can be used to guide thin film dewetting evolution and break the intrinsic spatial correlation of spontaneous instability. An AFM is used to implement the mechanical modification of progressively narrow grids to investigate the influence of pattern size on the modulation of ultrathin polystyrene films dewetting evolution. For films with different initial thicknesses, when grid size is close to or below the characteristic wavelength of instability, the spinodal dewetting is suppressed, and film rupture is restricted to the cutting trench. We will show in this paper it is possible to generate only one droplet per gridded area on a thin film subsequent to nucleation dominated dewetting on a non-patterned substrate. Furthermore, when the grid periodicity exceeds the spinodal length, the number of droplets in predefined areas gradually approaches that associated with unconfined dewetting.

Micropatterned Arrays of ZnSe Nanospheres as Antireflection Coatings

In this work, we demonstrate deposition of micro-arrays of ZnSe nanospheres on Si (100) substrate using simple thermal evaporation on a self-assembled sacrificial polystyrene (PS) mask. The results have been compared with the deposition on unpatterned gold catalyst- and SU-8 (negative photoresist)-coated Si substrates. The deposited ZnSe nanospheres properties were characterised by X-ray diffraction, atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman, photoluminescence, and UV-vis spectroscopies. The X-ray diffraction patterns of the films exhibited reflection corresponding to the cubic (111) phase and showed polycrystallinity with a cubic (zinc blende) structure. The SEM and AFM images indicated that the particles were well dispersed and spherical in shape. The micro-arrays of ZnSe nanospheres on a self-assembled sacrificial PS mask showed excellent structural, morphological, and optical properties and demonstrated its usage in photovoltaic devices as an improved superior antireflective coating. The reflectance of the micro-arrays of ZnSe nanospheres on a self-assembled sacrificial PS mask decreased to nearly half of that of the ZnSe nanospheres fabricated on Au- and SU-8-coated Si substrates in the range of 300–800 nm. Due to the well aligned and patterned surfaces, these noble textured ZnSe nanospheres may be suitable for low cost, large area photovoltaic devices and other antireflection applications.