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The DNA-Transistor is a device designed to control the translocation of single-stranded DNA through a solid-state nanopore. Functionality of the device is enabled by three electrodes exposed to the DNA-containing electrolyte solution within the pore and the application of a dynamic electrostatic potential well between the electrodes to temporarily trap a DNA molecule. Optimizing the surface chemistry and electrochemical behavior of the device is a necessary (but by no means sufficient) step toward the development of a functional device. In particular, effects to be eliminated are (i) electrochemically induced surface alteration through corrosion or reduction of the electrode surface and (ii) formation of hydrogen or oxygen bubbles inside the pore through water decomposition. Even though our motivation is to solve problems encountered in DNA transistor technology, in this paper we report on generic surface chemistry results. We investigated a variety of electrode-electrolyte-solvent systems with respect to their capability of suppressing water decomposition and maintaining surface integrity. We employed cyclic voltammetry and long-term amperometry as electrochemical test schemes, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning, as well as transmission electron microscopy as analytical tools. Characterized electrode materials include thin films of Ru, Pt, nonstoichiometric TiN, and nonstoichiometric TiN carrying a custom-developed titanium oxide layer, as well as custom-oxidized nonstoichiometric TiN coated with a monolayer of hexadecylphosphonic acid (HDPA). We used distilled water as well as aqueous solutions of poly(ethylene glycol) (PEG-300) and glycerol as solvents. One millimolar KCl was employed as electrolyte in all solutions. Our results show that the HDPA-coated custom-developed titanium oxide layer effectively passivates the underlying TiN layer, eliminating any surface alterations through corrosion or reduction within a voltage window from -2 V to +2 V. Furthermore, we demonstrated that, by coating the custom-oxidized TiN samples with HDPA and increasing the concentration of PEG-300 or glycerol in aqueous 1 mM KCl solutions, water decomposition was suppressed within the same voltage window. Water dissociation was not detected when combining custom-oxidized HDPA-coated TiN electrodes with an aqueous 1 mM KCl-glycerol solution at a glycerol concentration of at least 90%. These results are applicable to any system that requires nanoelectrodes placed in aqueous solution at voltages that can activate electrochemical processes.

We report novel strategies to integrate block copolymer self-assembly with 193 nm water immersion lithography. These strategies employ commercially available positive tone chemically amplified photoresists to spatially encode directing information into precise topographical or chemical prepatterns for the directed self-assembly of block copolymers. Each of these methods exploits the advantageous solubility and thermal properties of polarity-switched positive tone photoresist materials. Precisely registered, sublithographic self-assembled structures are fabricated using these versatile integration schemes which are fully compatible with current optical lithography patterning materials, processes, and tooling.

We have demonstrated direct nanoscale transfer printing (nTP) of PdAu lines from a hard mold onto a hard substrate at room temperature without employing any flexible buffer layers or organic adhesion promoters or release agent layers. PdAu was evaporated onto the mold surface, and a Ti layer was deposited on top of the PdAu layer. By pressing the mold against a Si/SiO2 substrate, the PdAu/Ti sandwich structure was directly transferred onto the SiO2 surface. The molds used in these experiments were GaAs/AlGaAs sandwich structures fabricated by molecular beam epitaxy that we cleaved and selectively etched afterwards in order to generate 3-D grating structures with nanometer resolution on their edges. We fabricated positive multiline molds with different aspect ratios, linewidths between 15 and 100 nm, and spacings between lines ranging from 5 to 70 nm. We also fabricated negative single-line molds with a positive supporting structure comprising a single 16-nm-wide groove feature. The experiments revealed that direct hard-on-hard transfer of nanoscale structures from a mold onto a substrate can be used to fabricate PdAu gaps with widths down to 9 nm. We also performed electronic measurements on transfer patterns and demonstrated that transferred structures can be used as electrodes, which are electrically isolated by these gaps. Since isolation characteristics of gaps improved with decreasing gap length, we partitioned longer gap segments into multiple shorter ones by focused ion beam lithography and conventional optical lithography in combination with wet chemical or plasma etching of the mold or the substrate, respectively. In this paper, we give a detailed description of all technological aspects of the developed direct nTP technique, including mold preparation, patterning efficiency, short reduction techniques, and yield.

We have demonstrated single-step room temperature nanoimprint lithography (RTNIL) using polystyrene (PS, average molecular weights ranging from 13 to 97 kg/mol) as the imprint polymer layer on a silicon substrate for imprinting rectangular line patterns with varying aspect ratios, ranging from 11 to 500 nm wide. To accomplish this demonstration, we designed and built a tool that controllably pressed a mold into a stationary imprint sample applying imprint pressures between 280 and 700 MPa. The molds used in these experiments were GaAs/AlGaAs sandwich structures fabricated by molecular beam epitaxy (MBE) that we cleaved and selectively etched afterward in order to generate 3-D grating structures with nanometer resolution on their edges. We fabricated positive and negative molds comprising single- line as well as multiline patterns with different aspect ratios and linewidths between 9 and 300 nm.

We have demonstrated multistep room-temperature nanoimprint lithography (RTNIL) using polystyrene (PS, average molecular weight 97 kg/mol) as the imprint polymer layer on a silicon substrate for imprinting complex patterns. Single, double, and multiple (up to ten) sequential imprint steps were performed at imprint pressures between 1 to 30 MPa in separate experiments. We also transferred the imprinted patterns from the PS layer into the silicon substrate by means of an reactive-ion etching (RIE) process. To accomplish this demonstration, we designed and built a tool that controllably and repeatedly translated and pressed a sample into a stationary mold. The demonstrated interstep alignment accuracy of this tool ranged between 80 nm and 380 nm. These experiments revealed that polymer deformation results when nanoimprint is used to further deform a previously structured surface. The molds used in these experiments consisted of 400-nm-period diffraction gratings, as well as of rectangular structures of varying aspect ratios, ranging from 150 to 300 nm wide.

We use thermal and room temperature nanoimprint lithography (NIL) for directly patterning the photoactive polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) in the sub-50-nm region. Different types of molds were used to directly imprint the desired structures into P3HT thin films. Good pattern transfer is achieved independent of the presence of other underlying polymer layers or the type of substrate incorporated. Further, we discuss the future application of this technology to the fabrication of ordered heterojuction organic photovoltaic devices and demonstrate that the NIL process involved does not damage the polymer or alter its chemical or electrical properties.

In this work, the conventional via-first dual damascene (DD) patterning scheme is replaced by a cost-efficient Multi-Level Multiple Exposure (MLME) patterning and etching approach. A two-layer positive-tone photoresist stack is sequentially imaged using 193 nm dry lithography, to produce a DD resist structure that is subsequently transferred into an auxiliary dual organic underlayer stack, and then further into a dielectric layer. This novel integration approach eliminates inter-tool wafer exchange sequences as performed in a conventional litho-etch-litho-etch process flow, while simultaneously being applicable to all back-end-of-the-line (BEOL) levels, ensuring throughput increase. The top and bottom resist layers are chemically designed in such a way that they feature differential solubility in organic solvents making it possible to coat the top photoresist onto the bottom resist layer without intermixing to enable a strict litholitho- etch processing sequence. Independent registration of the via and trench structures in the bottom and top resist layers is achieved by selective photospeed decoupling of the respective layers, so that the bottom resist is largely insensitive at nominal resist exposure dose for the top resist. Imaging performance evaluation of the newly introduced MLME technology includes the resist materials selection process and their required properties (solvent compatibility, adhesion, photospeed, defectivity and correction of via dose bias due to trench exposure) as well as metrology work. Image transfer of the patterned DD resist structure into an underlying transfer layer stack and then further into a dielectric layer using Reactive Ion Etching (RIE) followed by electroplating, polishing and electrical testing was also thoroughly investigated and is described in detail in an accompanying paper.

In this paper, we will outline the approach for optimizing the illumination conditions to print three-dimensional images in resist stacks of varying sensitivity in a single exposure. The algorithmic approach for acheiving both optimal common and weakest window is presented. Results will be presented which demonstrate the ability of the technique to create threedimensional structures. The performance of the common and weakest window formulation will be explored using this approach. Additionally, due to physical restrictions there are limitations to the type of patterns that can be printed with a single exposure in this manner, thus the abilities of such a technique will be explored.

Challenges and issues of Nanoimprint Lithography (NIL) are addressed and discussed. In particular, imprinting properties of an innovative epoxy-based polymer have been investigated, which can be used for combined thermal and ultraviolet nanoimprinting (TUV-NIL) processes aiming at high-throughput nanoimprint lithography. Our recent progress in developing a new room-temperature nanoimprint (RTNIL) tool for the sub-10-nm region is shown.

Nanoimprint lithography (NIL) is a new technique for lithographic patterning of nanostructures, which has advantages of high resolution, high throughput and low cost. This technique is presenting great opportunities for innovation and discovery in many engineering and scientific areas, such as electronic, optoelectronic and magnetism. We will show how the combination of different NIL techniques can lead to the realization of optical components such as waveguide gratings, sub-wavelength gratings, wavelength filters and photonic crystals, which in turn can lead to the design of optical devices with enhanced performance.

We performed combined thermal and ultraviolet nanoimprint lithography (TUV-NIL) using a recently developed nanoimprint polymer (mr-NIL 6000 from Micro Resist technology GmbH) and achieved an imprinted feature size of 50 nm. We used commercially available 2-inch-diameter transparent quartz molds (NIL Technology, Denmark and Obducat, Sweden) comprising 150 nm to 190 nm-deep features of various shapes and aspect ratios with lateral dimensions ranging between 50 nm and 300 nm. The imprint polymer was spun onto a silicon substrate, covered with an oxide layer. After the TUV-NIL step, residual polymer layers at the bottom of the imprinted features were removed by oxygen plasma etching. Imprinted patterns were then transferred into the silicon oxide layer underneath by reactive ion etching (RIE). In a final step the residual polymer was stripped off the silicon oxide surface in an oxygen asher. All imprinted features as well as the corresponding pattern transfer results showed good surface and sidewall characteristics.

We have demonstrated multi-step room-temperature nanoimprint lithography (RTNIL) using polystyrene (PS, average molecular weight 97 kg/mol) as the polymer layer for imprinting complex patterns. In separate experiments, single, double, and multiple (up to 10) sequential imprint steps were performed at imprint pressures between 1 to 30 MPa. To accomplish this demonstration, we designed and built a tool that controllably and repeatedly translated and pressed a sample into a stationary mold. The demonstrated inter-step alignment accuracy of this tool was ∼500 nm. Results of these experiments revealed the polymer deformation that results when nanoimprint is used to further deform a previously structured surface. The molds used in these experiments consisted of 400-nm-period diffraction gratings, as well as of rectangular structures of varying aspect ratios, ranging from 150 to 300 nm wide.

Recently, application of nanopores to low-cost DNA sequencing has attracted great interest as there is great need to reduce the cost of sequencing a whole human genome to $1000. A key issue in the field of nanopore DNA sequencing is to control the DNA translocation. Here we will report the development of what we call a “DNA transistor”: a nanopore-based electrical device for controlling the translocation of DNA with single base resolution. The key part of this device is a free standing membrane, within which multiple layers of electrically addressable metal electrodes separated by dielectric layers are embedded. A 1-5 nanometer size pore is made through the membrane. We demonstrated that such a device is electrically viable for the electrode layer or the spacing dielectric layer as thin as 3 nm. Confirming the basic function of the device, induced electrical signals on the nano-electrodes by the translocating DNA, as well as the modulation of DNA translocation speed by the voltage bias applied on the nano-electrodes are also observed. Our ongoing experiments test if the modulated electrical field can trap or translocate DNA at a single base resolution.