Self-aligned Patterns Research Articles

Self-aligned bilayer inkjet printing process for reducing shadow area by auxiliary electrodes in OLED lighting

Auxiliary electrodes are a key component for uniform luminance of large area organic light emitting diode (OLED) lighting. A shadow area is created by the auxiliary electrodes covering the light emitting area of ​​the OLED, reducing the light emitting area. To minimize the shadow area of ​​ printed auxiliary electrodes, we developed a self-aligned bilayer inkjet printing (SABP) process. A silver-insulator bilayer was self-aligned by a hydrophobic bank where the ink did not spread. Through the SABP process, the insulator was covered with a width that was about 400 nm wider than the width of the Ag electrode. In addition, electro-optical characteristics such as luminance, current density, current efficiency, and external quantum efficiency of 40 × 40 mm 2 OLED lighting were measured to confirm the effect of the fabricated auxiliary electrodes. The luminance non-uniformity of the OLED lighting with the printed auxiliary electrode was 17%. For OLED lighting, inkjet-printed auxiliary electrodes provide potentials comparable to those of vacuum-deposited auxiliary electrodes. • Self-aligned bilayer printing patterns the silver-insulator of an auxiliary electrode for OLED lighting. • The auxiliary electrode is printed with a height of 1.09 μm and a width of 21.1 μm. • The insulator covers the width of the Ag electrode with a margin of 400 nm wide. • Self-aligned bilayer printing is effective in reducing a shadow area by auxiliary electrodes. • The luminance non-uniformity of OLED lighting with printed auxiliary electrodes is 17%.

Area-Selective Atomic Layer Deposition: Understanding the Surface Processes on the Nongrowth Surface

With feature dimensions of state-of-the-art semiconductor devices moving toward the 5 nm node and beyond, device fabrication based on top-down approaches is becoming ever more challenging. Recently, area-selective atomic layer deposition (ALD) has evolved as a promising method to fabricate well-defined patterns from the bottom-up with atomic-scale accuracy. Within the different approaches for area-selective ALD, preparation of patterned substrates with material-selective organic functionalization offers a promising direction for achieving self-aligned patterns over large areas. In this talk, I will address the interaction of the ALD precursors with the nongrowth surface studied using in situ attenuated total reflection Fourier transform infrared spectroscopy and 4-wavelength ellipsometry. In particular, I will outline the mechanisms that lead to initiation of growth on the passivated nongrowth surface.

Scalable Directed Assembly of Highly Crystalline 2,7-Dioctyl[1]benzothieno[3,2- b][1]benzothiophene (C8-BTBT) Films.

Assembly of organic semiconductors with ordered crystal structure has been actively pursued for electronics applications such as organic field-effect transistors (OFETs). Among various film deposition methods, solution-based film growth from small molecule semiconductors is preferable because of its low material and energy consumption, low cost, and scalability. Here, we show scalable and controllable directed assembly of highly crystalline 2,7-dioctyl[1]benzothieno[3,2- b][1]benzothiophene (C8-BTBT) films via a dip-coating process. Self-aligned stripe patterns with tunable thickness and morphology over a centimeter scale are obtained by adjusting two governing parameters: the pulling speed of a substrate and the solution concentration. OFETs are fabricated using the C8-BTBT films assembled at various conditions. A field-effect hole mobility up to 3.99 cm2 V-1 s-1 is obtained. Owing to the highly scalable crystalline film formation, the dip-coating directed assembly process could be a great candidate for manufacturing next-generation electronics. Meanwhile, the film formation mechanism discussed in this paper could provide a general guideline to prepare other organic semiconducting films from small molecule solutions.

Self-aligned grating couplers on template-stripped metal pyramids via nanostencil lithography.

We combine nanostencil lithography and template stripping to create self-aligned patterns about the apex of ultrasmooth metal pyramids with high throughput. Three-dimensional patterns such as spiral and asymmetric linear gratings, which can couple incident light into a hot spot at the tip, are presented as examples of this fabrication method. Computer simulations demonstrate that spiral and linear diffraction grating patterns are both effective at coupling light to the tip. The self-aligned stencil lithography technique can be useful for integrating plasmonic couplers with sharp metallic tips for applications such as near-field optical spectroscopy, tip-based optical trapping, plasmonic sensing, and heat-assisted magnetic recording.

Transfer of self-aligned spacer patterns for single-digit nanofabrication

We report the transfer of sub-10 nm half-pitch grating patterns created through a combination of block copolymer directed self-assembly and sidewall spacer-based self-aligned double patterning into Si substrates. Low substrate bias reactive ion etching of TiOx conformally deposited onto carbon mandrels using atomic layer deposition renders distinct, pitch-halved spacers with minimal etch byproduct redeposition. Independent spacer and mandrel width control and the use of an underlying CrNx hard mask deposited by reactive sputtering facilitates etching of Si lines with low roughness and fine placement control. The insights into pattern transfer presented here are directly applicable to the fabrication of rectangular bit pattern nanoimprint templates at densities above 1.5 Td in−2.

Impact of process parameters on pattern formation of the self-aligned multiple patterning process.

Double patterning (DP) and multiple patterning (MP) are techniques employed to extend the useful life of optical lithography through higher density chip transistors. The self-aligned double patterning (SADP) and the self-aligned multiple patterning (SAMP) are promising technologies that can be expanded to 22 nm and 1 x nm patterns for the dynamic random access memory (DRAM) and NAND flash memory devices. It is important to understand how the final pattern is related to each SADP or SAMP step to optimize process parameters and develop those processes. In this paper, the SADP and the SAMP model the optical lithography process and the spacer-aligned process to reduce those complexites and optimize those critical dimension uniformities (CDUs). For the spacer-aligned process, deposition and etching were modeled using a ray-trace algorithm and a level-set method. For the SADP and the SAMP, simulation results similar to the experimental results allow the prediction of self-aligned patterns and the pattern effects of process parameters.

Helium beam shadowing for high spatial resolution patterning of antibodies on microstructured diagnostic surfaces

We have developed a technique for the high-resolution, self-aligning, and high-throughput patterning of antibody binding functionality on surfaces by selectively changing the reactivity of protein-coated surfaces in specific regions of a workpiece with a beam of energetic helium particles. The exposed areas are passivated with bovine serum albumin (BSA) and no longer bind the antigen. We demonstrate that patterns can be formed (1) by using a stencil mask with etched openings that forms a patterned exposure, or (2) by using angled exposure to cast shadows of existing raised microstructures on the surface to form self-aligned patterns. We demonstrate the efficacy of this process through the patterning of anti-lysozyme, anti-Norwalk virus, and anti-Escherichia coli antibodies and the subsequent detection of each of their targets by the enzyme-mediated formation of colored or silver deposits, and also by binding of gold nanoparticles. The process allows for the patterning of three-dimensional structures by inclining the sample relative to the beam so that the shadowed regions remain unaltered. We demonstrate that the resolution of the patterning process is of the order of hundreds of nanometers, and that the approach is well-suited for high throughput patterning.

Self-alignment method for solution-processable dielectric structures via joule heating

We present a versatile method to create self-aligned patterns of polymer dielectric on metal by the use of Joule heating. In contrast to global thermal or light based curing, the method self-aligns the dielectric to a metal pattern on the substrate. A current-induced temperature rise along a metal line cures the insulator locally; uncured material is then removed by rinsing with solvent. We have obtained very promising results for aligning thermally cross-linkable and selectively baked dielectrics. Alignment of cross-linkable polymers is less sensitive to the rinsing step than selectively baked dielectrics. Finite-element simulations were used to determine the range of suitable curing current. After optimization of the curing parameters high yield and low leakage dielectrics were obtained.

Unidirectional self-patterning of CaF2 nanorod arrays using capillary pressure

Abstract

Self-Aligned Nanogaps on Multilayer Electrodes for Fluidic and Magnetic Assembly of Carbon Nanotubes

A self-aligned nanogap between multiple metal layers has been developed using a new controlled undercut and metallization technique (CUMT), and practically applied for self-assembly of individual carbon nanotubes (CNTs) over the developed nanogap. This new method allows conventional optical lithography to fabricate nanogap electrodes and self-aligned patterns with nanoscale precision. The self-aligned nickel (Ni) pattern on the nanogap electrode works as an assembly spot where the residual iron (Fe) catalyst at the end of the CNT is magnetically captured. The captured CNT is forced to be aligned parallel to the flow direction by fluidic shear force. The combined forces of magnetic attraction and fluidic alignment provide massive self-assembly of CNTs at target positions. Both multiwalled nanotubes (MWNTs) and single walled nanotubes (SWNTs) were successfully assembled over the nanogap electrodes, and their electrical characteristics were fully characterized. The CNTs self-assembled on the developed electrodes with a nanogap and showed a very reliable and reproducible current-voltage (I-V) characteristic. The method developed in this work can envisage the mass fabrication of individual CNT-assembled devices which can be applied to nanoelectronic devices or nanobiosensors.

Easy mask-mold fabrication for combined nanoimprint and photolithography

Hybrid transparent working stamps with both a surface relief and absorbing mask pattern were fabricated by replicating nanostructures in an Ormostamp film on prepatterned glass substrates. By using a combined nanoimprint and photolithography process, self-aligned mixed patterns of nano- and microstructures can be generated within one single resist layer. In this article the authors present a simple process based on the organic-inorganic hybrid polymer Ormostamp by replication on prepatterned Borofloat substrates. Using these working stamps, grating arrays with 35 nm half pitch were replicated in thermoplastic UV-curable resist. The method is easy to employ for generating mesas with nanostructures on top or the backfilling with microstructures in thermal nanoimprint lithography applications.

Self-aligned patterns of multiple biomolecules printed in one step

We describe an adaptation of the microcontact printing technique for generating self-aligned patterns of two different molecules in one printing step. Elastomeric stamps exhibiting different levels of topography are designed and fabricated so that, by external pressure, their deformation enables two planes, selectively inked with two different molecules, to contact the surface. The fabrication of 1 μm wide biomolecular patterns aligned into 5 μm wide patterns of another biomolecule is demonstrated through fluorescence imaging and atomic force microscopy.

Self-Aligned Deposition Process for Ultrathin Electroless Barriers and Copper Films on Low-k Dielectric Films

A self-aligned, integrated plating technique based on plasma physics and colloidal-related chemistry is proposed to fabricate patterns of ultrathin (≤20 nm) Co-based barriers and copper films in a selective manner on dielectric (HOSP and SiO 2 ) films using electroless plating. High-resolution X-ray absorption spectroscopy, transmission electron microscopy, and atomic force microscopy reveal that, once properly pretreated by a gaseous plasma (O 2 or H 2 /N 2 ) and hydrogen peroxide (H 2 O 2 ) in a basic aqueous solution, the dielectric films can adsorb highly populated metallic (Ni) precipitates of sizes approximately from 2 to 4 nm to catalyze the deposition of electroless Co-based barriers. Finally, the capability of this technique to fabricate self-aligned patterns of barrier and copper is demonstrated and the importance of the plasma pretreatment and hydrogen peroxide (in SC-1 solution) is discussed.

A Single Expose Double Develop (SEDD) process for self-aligned lithographic applications

A Single Expose Double Develop process has been developed which incorporates the use of a tridensity mask to expose two self-aligned patterns in conventional photoresist with one masking step. This minimizes masking cycles and overlay errors which translates into increased yield. The resultant pattern can be customized for various applications, e.g. obtaining two dopant profiles with a single implant using a dual thickness photoresist pattern, transferring two patterns into underlying films with no alignment error using RIE or wet etching, etc... Experiments are shown which optimize the processing parameters of the photoresist to the density levels in the mask, utilizing characteristic curves for analysis. Process control is correlated to these curves through modelling and experiment. Examples of the applications of the SEDD process in VLSI devices and packaging are shown with SEM photographs.

Current crowding and misalignment effects as sources of error in contact resistivity measurements—Part II: Experimental results and computer simulation of self-aligned test structures

In this work we show that an accurate and straightforward extraction of the contact resistivity from contact resistance data can be achieved using properly designed self-aligned test patterns. In this way, the parasitic effects are minimized and the contact resistivity can be derived using simple one-dimensional models as confirmed by our computer simulation. Experimental results obtained in self-aligned structures are presented for Al/CoSi <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> Si and Al-Si/n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> Si contacts.