Scaling considerations for sub-90 nm split-gate flash

A systematic methodology is presented to scale split-gate (SG) flash memory cells in the sub-90 nm regime within the presently known scaling constraints of flash memory. The numerical device simulation results show that the high performance sub-90 nm NOR-type SG cells can be achieved by a suitable channel and source-drain engineering. An asymmetric channel doping profile along with ultra-shallow source-drain junctions was used to achieve the target drain programming voltage (V_sp) for an efficient cell programming while keeping the cell breakdown voltage, BV > V_sp, with tolerable leakage currents. The study shows that with properly optimised technology parameters, 65 nm SG-NOR flash memory can be achieved with an adequate cell read current, a tolerable programmed cell leakage current at the read condition and efficient write and erase times.     

High-speed, sub-15 nm feature size thermochemical nanolithography

We report a nanolithography technique that allows simultaneous direct control of the local chemistry and topography of thin polymer films. Specifically, a heated atomic force microscope (AFM) tip can write sub-15 nm hydrophilic features onto a hydrophobic polymer at the rate of 1.4 mm per s. The thermally activated chemical reactions and topography changes depend on the chemical composition of the polymer, the raster speed, the temperature at the AFM tip/sample interface, and the normal load. This method is conceptually simple, direct, extremely rapid, achievable in a range of environments, and potentially adaptable to other materials systems.     

An optimization method for flexural bearing design for high-stroke high-frequency applications

A method for optimization of a high-stroke, high-frequency flexural bearing was completed. The main goal was to design a flexural bearing system as the energy restoration component of a one kW free piston linear engine alternator (LEA) operating at 90 Hz and maximum targeted displacement of 22 mm. Defined electricity output of 1 kW, with more than 30% efficiency, required engine operation under high speed and high stroke conditions. Under such challenging stroke and frequency requirements, a method of design was required to select between a wide range of parameters in flexural bearing design. A parametric CAD model was prepared and used in the optimization package of a finite element analysis (FEA) software. Four main parameters of flexural bearing geometry were identified and included the outer diameter, thickness, number of arms, and sweep angle of spiral cuts. Other design parameters including spiral gap width, shape factor and spiral start points angle were shown to be less important compared to these four main parameters in primary design and were examined separately. A neural network algorithm was used to investigate the interactions and effects of design parameters. The sensitivity of each parameter on output criteria such as maximum stress and natural frequency was examined and design charts developed. Methods for further modification of the spiral curve at end points were introduced to reduce the maximum stress level by up to 20%. Several steel alloys and a titanium-based alloy were identified as proper material candidates for high cycle applications and the final designed spring was manufactured and tested to validate the FEA results of axial stiffness and strain level throughout the flexure arms. The percent of the flexure’s moving mass was estimated to be 29% with FEA analysis and compared well with the experimental value of 31%. The stress/strain results of the FEA analysis matched with the experimental results – within ±5%.     

A nanocontact printing system for sub-100 nm aligned patterning

Though many aspects of contact printing have been explored extensively since its invention, there are still hurdles to overcome for multilayer printing in the nanometer regime. Here we report on an aligned nanocontact printing (nCP) system that has demonstrated a sub-100 nm alignment capability by means of moiré fringes and microspacers. To address issues in the stamp inking, we have devised a microfluidic apparatus based on the gradient capillary force for transport of ink solutions. The nCP system has been tested by printing nucleoside phosphoramidites on a nanopillar arrayed substrate. Although the nCP system was designed primarily for use in the fabrication of high density DNA nanoarrays, it has the potential to be applied to other fields of nanotechnology for nanoscale patterning.     

A nonlinear system model for electrospinning sub-100 nm polyacrylonitrile fibres

Solutions of polyacrylonitrile (PAN) were electrospun using a range of process parameters, resulting in fibre diameters from 10 to 320?nm. A nonlinear neural network system model was used to analyse the dependence of the fibre diameter on the process parameters, and used to simulate conditions for electrospinning 40-60?nm diameter fibres. These results indicated that flow rate is most important for determining fibre diameter. It was not possible to find the appropriate conditions for electrospinning sub-25?nm fibres. Precise control of the ambient temperature and relative humidity will be critical to producing electrospun fibres that are sub-25?nm. Further, it is unlikely that sub-25?nm fibres will be produced without significant changes in the electrospinning apparatus, for example, by use of focusing and jet-steering fields, alternate carrier gases to modify the discharge characteristics, or patterned electrospinning.     

Advanced colloidal lithography for sub-100 nm lift-off structures

We report on the fabrication of hexagonally ordered, sub-wavelength hole arrays (SWHA) by colloidal lithography combined with reactive ion etching and a lift-off process, and their characterization with scanning electron microscopy and ellipsometry.     

Fabrication of sub-10 nm planar nanotips for transport experiments of biomolecules

Electron beam lithography (EBL) and lift-off process have been used to fabricate two- and three-terminal nano-devices consisting of metallic (Cr/Au, Ti/Au or Ti/Pt) arrow-shaped electrodes on Si/SiO₂, with tip separation between 100 and less than 10 nm. Standard EBL process allowed us to obtain nanotips with separation around 40 nm. In order to reduce the tip separation down to about 20 nm, before the EBL process, we used the defocused e-beam to brush the PMMA resist for a precise time (10÷40 s). A further reduction of the tip gap (less than 10 nm) is obtained by Au electroplating deposition. The nanotips were electrically characterized by current–voltage (I–V) measurements in the range ±2 V. In a typical I–V measurement in air of an “open-circuit” nanodevice, no significant current is observed (current range −10÷+10 pA, “open circuit” resistance≈1 TΩ) confirming the success of the technological process.     

Scalable synthesis of sub-100 nm hollow carbon nanospheres for energy storage applications

Sub-100 nm hollow carbon nanospheres with thin shells are highly desirable anode materials for energy storage applications. However, their synthesis remains a great challenge with conventional strategies. In this work, we demonstrate that hollow carbon nanospheres of unprecedentedly small sizes (down to ～32.5 nm and with thickness of ～3.9 nm) can be produced on a large scale by a templating process in a unique reverse micelle system. Reverse micelles enable a spatially confined Stöber process that produces uniform silica nanospheres with significantly reduced sizes compared with those from a conventional Stöber process, and a subsequent well-controlled sol–gel coating process with a resorcinol–formaldehyde resin on these silica nanospheres as a precursor of the hollow carbon nanospheres. Owing to the short diffusion length resulting from their hollow structure, as well as their small size and microporosity, these hollow carbon nanospheres show excellent capacity and cycling stability when used as anode materials for lithium/sodium-ion batteries.

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Lithography-free sub-100 nm nanocone array antireflection layer for low-cost silicon solar cell

A high-density and -uniformity sub-100 nm surface-oxidized silicon nanocone forest structure is created and integrated onto the existing texturization microstructures on a photovoltaic device surface by a one-step high-throughput plasma-enhanced texturization method. We suppressed the broadband optical reflection on chemically textured grade-B silicon solar cells for up to 70.25% through this nanomanufacturing method. The performance of the solar cell is improved with the short-circuit current increased by 7.1%, fill factor increased by 7.0%, and conversion efficiency increased by 14.66%. Our method demonstrates the potential to improve the photovoltaic device performance with low-cost and high-throughput nanomanufacturing technology.     

Superparamagnetic sub-5 nm Fe@C nanoparticles: isolation, structure, magnetic properties, and directed assembly

A method for isolating single crystalline sub-5 nm carbon coated iron nanoparticles (Fe@C NPs) from a carbon nanotube matrix has been developed. The isolation of such particles allows for their characterization by high resolution electron microscopy methods and SQUID magnetometry. While the NPs are superparamagnetic at room temperature, at 10 K they exhibit a coercivity nearly 30 times greater than that of commercial Fe3O4 NPs of comparable size. A novel nanotemplate directed assembly method for manipulating the particles at the individual particle level is also reported.     

Design and performance of EUV resist containing photoacid generator for sub-100 nm lithography

To fulfill the SIA roadmap requirements for EUV resists, the development of entirely new polymer platforms is necessary. In order to address issues like Line Edge Roughness (LER) and photospeed, we have developed a novel chemically amplified photoresist containing a photoacid generator (PAG) in the main chain of the polymer. The incorporation of a cationic PAG unit, phenyl methacrylate dimethylsulfonium nonaflate (PAG), in the resist backbone showed increased sensitivity, when compared with analogous blend PAG resist samples. In addition, the overall lithographic performance improved by using the counter anion (nonaflate) in the PAG units. The newly synthesized polymer bound PAG resist, poly (4-hydroxystyrene-co-2-ethyl-2-adamantyl methacrylate-co-PAG) showed sub-50 nm features using EUV Lithography.     

SANTA: Self-aligned nanotrench ablation via Joule heating for probing sub-20 nm devices

Manipulating materials at the nanometer scale is challenging, particularly if alignment with nanoscale electrodes is desired. Here, we describe a lithography-free, self-aligned nanotrench ablation (SANTA) technique to create nanoscale “trenches” in a polymer like poly(methyl methacrylate) (PMMA). The nanotrenches are self-aligned with carbon nanotube (CNT) or graphene ribbon electrodes through a simple Joule heating process. Using simulations and experiments we investigated how the Joule power, ambient temperature, PMMA thickness, and substrate properties affect the spatial resolution of this technique. We achieved sub-20 nm nanotrenches, for the first time, by lowering the ambient temperature and reducing the PMMA thickness. We also demonstrated a functioning nanoscale resistive memory (RRAM) bit selfaligned with a CNT control device, achieved through the SANTA approach. This technique provides an elegant and inexpensive method to probe nanoscale devices using self-aligned electrodes, without the use of conventional alignment or lithography steps.

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An analysis of failure-time distributions for product design optimization

Analysis of experimental data is often a problem facing design and manufacturing engineers. Many experiments are run for the express purpose of making a decision between manufacturing process or material alternatives. Statisticians recommend replication in experimental design; however, methods of analysing experimental data, as presented in a majority of engineering curricula, generally review only the most basic situations (checking for a statistically significant difference between the means or variances of two samples, for example). If means and variances change with time, group comparisons may require more sophisticated analyses. This paper presents one method that takes into account shifts in group means and variances over time. Resistance temperature sensor drift data generated from six different design configurations are used as an illustration. This procedure takes into account all drift path information from multiple sensors in multiple groups.     

Crushing analysis and multi-objective optimization design for bionic thin-walled structure

Thin-walled structure has gained increasing attention and been widely used in the field of mechanical engineering due to their extraordinary energy absorption capacity and light weight. In this paper, we introduced a new energy absorbed structure named as bionic thin-walled structure (BTS) based on the structural characteristics of horsetails. In this study, six kinds of BTSs with different cross-sectional configurations under lateral loading conditions were investigated using nonlinear finite element method through LS-DYNA. According to the numerical results, it can be found that the cell number, inner wall diameter and wall thickness of the BTS had significant effect on the crashworthiness of the structure. In order to obtain the optimal design among the six kinds of BTSs, the six BTSs were optimized using a metamodel-based multi-objective optimization method which was developed by employing polynomial regression (PR) metamodel and multi-objective particle swarm optimization (MOPSO) algorithm. In the optimization process, we aimed to achieve maximum value of specific energy absorption (SEA) and minimum value of maximum impact force (MIF). Meanwhile, we also optimized the traditional thin-walled structures, i.e., the circular and square tubes. Based on the comparison of the Pareto fronts obtained by the multi-objective optimizations, we found that the crashworthiness of the BTSs was better than that of the circular and square tubes and the best BTS among the six kinds of BTSs was different when the limit of MIF was different. And, the optimal designs of the BTSs were found to have excellent energy absorption capacity under lateral impact and could be used in the future vehicle body.     

Dispersible gold nanorod dimers with sub-5 nm gaps as local amplifiers for surface-enhanced Raman scattering

We report the synthesis of solution-dispersible, 35 nm diameter gold nanorod dimers with gaps as small as ～2 nm for surface-enhanced Raman scattering (SERS). Using on-wire lithography (OWL), we prepared tailorable dimers in high yield and high monodispersity (～96% dimers) that produce both large and reproducible SERS signals with enhancement factors of (6.8 ± 0.7) × 10(8) for single dimers in air and 1.2 × 10(6) for ensemble-averaged solution measurements. Furthermore, we show that these structures, which are the smallest ever made by OWL, can be used to detect molecules on flat surfaces and in aqueous solutions. When combined, these attributes with respect to sensitivity, reproducibility, and tailorability lead to a novel and powerful local amplification system for SERS applications.     

Single sub-20 nm wide, centimeter-long nanofluidic channel fabricated by novel nanoimprint mold fabrication and direct imprinting

We report and demonstrate a new method to fabricate single fluidic-channels of uniform channel width (11-50 nm) and over 1.5 cm in length, which are essential to developing innovative bio/chemical sensors but have not been fabricated previously. The method uses unconventional nanofabrication (a combination of crystallographic anisotropic etching, conformal coating, and edge patterning, etc.) to create an imprint mold of a channel pattern and nanoimprint to duplicate such channel. The centimeter-long channel continuity is verified by flowing fluorescent dye-stained water and stretching and transporting DNAs. The 18 by 20 nm channel cross-section was confirmed by measuring the liquid conductance in the channel.     

Feature-based classifiers for design optimization

We present a design optimization method for systems with high-dimensional parameter spaces using inductive decision trees. The essential idea is to map designs into a relatively low-dimensional feature space, and to derive a classifier to search for high-performing design alternatives within this space. Unlike learning classifier systems that were pioneered by Holland and Goldberg, classifiers defined by inductive decision trees were not originally developed for design optimization. In this paper, we explore modifications to such classifiers to make them more effective in the optimization problem. We expand the notions of feature space, generalize the tree construction heuristic beyond the original information-theoretic definitions, increase the reliance on domain expertise, and facilitate the transfer of design knowledge between related systems. There is a relatively small but rapidly growing body of work in the use of inductive trees for engineering design; the method presented herein is complementary to this research effort.     

Non-stationary kriging for design optimization

Traditional surrogate modelling techniques, such as kriging, have been employed quite effectively within design optimizations. However, such models can fail to reproduce non-stationary responses accurately. This article explores the application of non-stationary kriging to design optimization and attempts to determine its applicability with regard to the optimization of both stationary and non-stationary objective functions. A series of analytical test problems and an engineering design problem are used to compare the performance of non-stationary and adaptive partial non-stationary kriging to traditional stationary kriging.