Micro and Nano Engineering最新文献

The optical properties and geometry of EUV mask absorbers play an essential role in determining the imaging performance of a mask in EUV lithography. Imaging metrics, including Normalized Image Log Slope (NILS), Telecentricity Error (TCE), and Best Focus Variation (BFV) through pitch deteriorate because of Mask 3-Dimensional (M3D) effects in EUV lithography, which limits the production efficiency. Alternative absorbers, including alloys of Ru and Ta, are anticipated to reduce some of the M3D effects; however, patterning these materials is challenging due to their low etch rates and poor etch selectivity against the Ru mask capping layer. Therefore, we propose a Ru/Ta bilayer approach to EUV mask absorbers and investigate it from a patterning and imaging standpoint. The top Ru layer thickness is calculated using the thin film interference phenomena, and we determine the bottom Ta layer that can produce improved NILS by utilizing the total absorber thickness optimization methodology. We demonstrate the patterning of the Ru/Ta bilayer using a two-step etch; the top Ru layer is patterned with Cl₂-O₂ Reactive Ion Etch (RIE), and the bottom Ta layer with Cl₂-N₂ RIE. The geometry and morphology of the patterned bilayer stack are investigated using TEM (Transmission Electron Microscopy), and interdiffusion at the interface of Ru and Ta is studied using EDS-STEM (Energy Dispersive X-ray Spectroscopy-Scanning Transmission Electron Microscopy). The non-ideal traits of the Ru/Ta bilayer stack, determined by experimental characterization techniques, are used to simulate the imaging performance and then compared against an ideal Ru/Ta bilayer stack, along with the reference Ta-based absorber. Even when non-idealities are considered, the simulation findings demonstrate that the Ru/Ta bilayer absorber exhibits improved NILS and reduced BFV compared to the Ta-based absorber. The outcomes encourage further research into the possibilities of multilayer absorbers, to tailor their optical characteristics by varying the thickness of individual layers.

Fine tuning of the material properties requires many trials and errors during the synthesis. The metal nanoparticles undergo several stages of reduction, clustering, coalescence and growth upon their formation. Resulting properties of the colloidal solution thus depend on the concentrations of the reagents, external temperature, synthesis protocol and qualification of the researcher determines the reproducibility and quality. Automatized flow systems overcome the difficulties inherent for the conventional batch approaches. Microfluidic systems represent a good alternative for the high throughput data collection. The recent advances in 3D-printing made complex topologies in microfluidic devices cheaper and easily customizable. However, channels of the cured photopolymer resin attract metal ions upon synthesis and create crystallization centers. In our work we present 3D-printed system for the noble metal nanoparticle synthesis in slugs. Alternating flows of oil and aqueous reaction mixtures prevent metal deposition on the channel walls. Elongated droplets are convenient for optical and X-ray diagnostics using conventional methods. We demonstrate the work of the system using Ag nanoparticles synthesis for machine-learning assisted tuning of the plasmon resonance frequency.

Hybrid nanoplasmonics is one of the most promising branch of nanophotonics which aims, in particular, to control the energy transfer between donor and acceptor nano-emitters via surface plasmons. Recently, an approach of nano-emitters positioning was introduced. It is based on two-photon polymerization of a photosensitive material which contains quantum dots as nano-emitters. This technique allowed for the integration of green quantum dots on plasmonic silver nanowires. In this article, we report on the use of this approach for integrating both green and red quantum dots on silver nanowires. The coupling between nano-emitters and propagating surface plasmons that are supported by the silver nanowires is reported and observed through their scattering at the nanowire ends. For both colors, a parametric study of the distance between the quantum dots and the nanowire extremity shows that precise control of the position of the launching sites enables control of light intensity at the wire end, through surface plasmon propagation length. More interestingly, by integrating two kinds of quantum dots on the same nanowire, we realized an efficient donor-acceptor hybrid nano-system, where green surface plasmons polaritons (from donors) are transformed into red plasmons (from acceptors) at controlled sites of the plasmonic guides, as a result of a frequency conversion of the plasmons polaritons.

Plasmonic metal nanomaterials are usually supported by rigid substrates, typically made of silicon or glass. Recently, there has been growing interest in developing soft plasmonic devices. Such devices are low weight, low cost, exhibit elevated flexibility and improved mechanical properties. Moreover, they maintain the features of conventional nano-optic structures, such as the ability to enhance the local electromagnetic field. On account of these characteristics, they show promise as efficient biosensors in biological, medical, and bio-engineering applications. Here, we demonstrate the fabrication of soft polydimethylsiloxane (PDMS) plasmonic devices. Using a combination of techniques, including electroless deposition, we patterned thin membranes of PDMS with arrays of gold nanoparticle clusters. Resulting devices show regular patterns of gold nanoparticles extending over several hundreds of microns and are moderately hydrophilic, with a contact angle of about 80°. At the nanoscale, scanning electron and atomic force microscopy of samples reveal an average particle size of ∼50 nm. The nanoscopic size of the particles, along with their random distribution in a cluster, promotes the enhancement of electromagnetic fields, evidenced by numerical simulations and experiments. Mechanical characterization and the stress-strain relationship indicate that the device has a stiffness of 2.8 MPa. In biological immunoassay tests, the device correctly identified and detected anti-human immunoglobulins G (IgG) in solution with a concentration of 25 μg/ml.

Microfluidic devices hold enormous potential for the development of cost-effective and faster alternatives to existing traditional methods across life science applications. Here we demonstrate the feasibility of fabricating a microfluidic device by means of photolithography comprising a single cell trap, a delay structure and a chamber defined by micropillars. This device is aimed to be used for biological applications such as replicative lifespan determination (RLS) of yeast cells, where single cell trapping, and cell counting are essential. The novelty of the present work lies on the integration of the above-mentioned microfluidic structures in a single device by means of the established method of photolithography by fine-tuning critical parameters needed to achieve the desired high aspect ratio (1:5) employing commercially available resins. The fine-tuning of the fabrication parameters in combination with appropriately selected resins allows for patterning reproducibly micron-sized features. The design of the proposed device ultimately aims at replacing the very cumbersome assays still commonly used today for RLS determination in budding yeast by a methodology that is drastically simpler and more time efficient.

Water-based bio-sourced resists are promising candidates as alternatives for deep ultraviolet (DUV) lithography by replacing current photoresists issued from petro-chemistry for microelectronics application. Chitosan films produced from seafood industry wastes enable patterning processes free of organic solvent and alkali-based developers, by substitution with water. After demonstrating high-resolution patterning at lab-scale after transfer into silica 10 mm wafer, we investigate here the industrial pre-transfer chitosan-based photoresist on the 300 mm pilot line scale at CEA-Leti for 193 nm DUV lithography.

Microscope-based Laser Doppler vibrometers (LDV) are optical instruments using laser Doppler interferometry to measure the motion of vibrating structures. As laser vibrometers measure without contact, they are also widely used for the characterization of the vibrational dynamics of silicon based micro-electro-mechanical systems (MEMS). Because silicon is opaque for visible light, MEMS-devices must be prepared without encapsulation to enable vibration measurements with standard laser vibrometers. However, the encapsulation itself is a critical process step during MEMS fabrication, and the reopening of the encapsulation bears the risk of damaging the device or altering its characteristics. Due to the high refractive index of silicon, vibrometry using infrared light is compromised by the inevitable influence of interfering reflections from encapsulation and device boundaries on the measurement results.

A novel low-coherent measurement technique is presented allowing to effectively suppress spurious interferences. This way, highly accurate vibration measurements and thus reliable analysis of the device dynamics of encapsulated MEMS are possible.

We demonstrate the fabrication of sub-100 nm T-Gate structures using a single electron beam lithography exposure and a tri-layer resist stack - PMMA/LOR/CSAR. Recent developments in modelling resist development were used to design the process, in which each resist is developed separately to optimise the resulting structure. By using a modelling approach and proximity correcting for the full resist stack, we were able to independently vary gate length (50-100 nm) and head size (250-500 nm) at the design stage and fabricate these T-Gates with high yield.

The continuous downscaling of nanoelectronics devices requires metrology solutions with sub-nanometer spatial resolution. Electrical scanning probe microscopy (E-SPM) techniques such as scanning spreading resistance microscopy have become important tools to map the electronic properties of these devices at nanometer scale using conductive diamond tips. Yet, the spatial resolution that can be achieved in an E-SPM measurement critically depends on the sharpness of the tip being used. Although much progress has already been made in optimizing the tip sharpness, cost-efficiently fabricated high-aspect-ratio diamond tips with ultra-high sharpness are still missing. Therefore, we have developed in this work a dry etching process for super sharp high-aspect-ratio conductive diamond tips, called hedgehog full diamond tips (HFDT), starting from standard low-aspect-ratio full diamond tips (FDT). The distinctive feature of our approach is the self-patterning etch step which benefits the high-volume production of such tips. The self-patterned mask is formed by nanoparticles originating from the interfacial layer deposited during the initial stage of the diamond growth, and metal particles from the surrounding metal cantilever material. In this work, we present our newly developed HFDTs and provide evidence that these tips outperform other conducting tips in terms of spatial resolution during E-SPM measurements.

Through Random Telegraph Noise (RTN) analysis, valuable information can be provided about the role of defect traps in fine tuning and reading of the state of a nanoelectronic device. However, time domain analysis techniques exhibit their limitations in case where unstable RTN signals occur. These instabilities are a common issue in Multi-Level Cells (MLC) of resistive memories (ReRAM), when the tunning protocol fails to find a perfectly stable resistance state, which in turn brings fluctuations to the RTN signal especially in long time measurements and cause severe errors in the estimation of the distribution of time constants of the observed telegraphic events, i.e., capture/emission of carriers from traps. In this work, we analyze the case of the unstable filaments in silicon nitride-based ReRAM devices and propose an adaptive filter implementing a moving-average detrending method in order to flatten unstable RTN signals and increase sufficiently the accuracy of the conducted measurements. The τ_e and τ_c emission/capture time constants of the traps, respectively, are then calculated and a cross-validation through frequency domain analysis (Lorentzian fitting) was performed proving that the proposed method is accurate.