Thomas Stauden

Large-area fabrication of TiN nanoantenna arrays for refractory plasmonics in the mid-infrared by femtosecond direct laser writing and interference lithography [Invited]

Robust plasmonic nanoantennas at mid-infrared wavelengths are essential components for a variety of nanophotonic applications ranging from thermography to energy conversion. Titanium nitride (TiN) is a promising candidate for such cases due to its high thermal stability and metallic character. Here, we employ direct laser writing as well as interference lithography to fabricate large-area nanoantenna arrays of TiN on sapphire and silicon substrates. Our lithographic tools allow for fast and homogeneous preparation of nanoantenna geometries on a polymer layer, which is then selectively transferred to TiN by subsequent argon ion beam etching followed by a chemical wet etching process. The antennas are protected by an additional Al2O3 layer which allows for high-temperature annealing in argon flow without loss of the plasmonic properties. Tailoring of the TiN antenna geometry enables precise tuning of the plasmon resonances from the near to the mid-infrared spectral range. Due to the advantageous properties of TiN combined with our versatile large-area and low-cost fabrication process, such refractory nanoantennas will enable a multitude of high-temperature plasmonic applications such as thermophotovoltaics in the future.

A First Implementation of an Automated Reel-to-Reel Fluidic Self-Assembly Machine

A first automated reel-to-reel fluidic selfassembly process for macroelectronic applications is reported. This system enables high-speed assembly of semiconductor dies (15 000 chips per hour using a 2.5 cm-wide web) over large-area substrates. The optimization of the system (>99% assembly yield) is based on identification, calculation, and optimization of the relevant forces. As an application, the production of a solid-state lighting panel is discussed, involving a novel approach to apply a conductive layer through lamination.

Effective collection and detection of airborne species using SERS-based detection and localized electrodynamic precipitation.

Three different delivery concepts (standard diffusion, global electrodynamic precipitation, and localized nanolens-based precipitation) and three different SERS enhancement layers (a silver film, a nanolens-based localized silver nanoparticle film, and the standard AgFON) are compared. The nanolens concept is applied to increase the SERS signal: a factor of 633, when compared to a standard mechanism of diffusion, is observed.

Surface Tension Directed Fluidic Self-Assembly of Semiconductor Chips across Length Scales and Material Boundaries

This publication provides an overview and discusses some challenges of surface tension directed fluidic self-assembly of semiconductor chips which are transported in a liquid medium. The discussion is limited to surface tension directed self-assembly where the capture, alignment, and electrical connection process is driven by the surface free energy of molten solder bumps where the authors have made a contribution. The general context is to develop a massively parallel and scalable assembly process to overcome some of the limitations of current robotic pick and place and serial wire bonding concepts. The following parts will be discussed: (2) Single-step assembly of LED arrays containing a repetition of a single component type; (3) Multi-step assembly of more than one component type adding a sequence and geometrical shape confinement to the basic concept to build more complex structures; demonstrators contain (3.1) self-packaging surface mount devices, and (3.2) multi-chip assemblies with unique angular orientation. Subsequently, measures are discussed (4) to enable the assembly of microscopic chips (10 μm–1 mm); a different transport method is introduced; demonstrators include the assembly of photovoltaic modules containing microscopic silicon tiles. Finally, (5) the extension to enable large area assembly is presented; a first reel-to-reel assembly machine is realized; the machine is applied to the field of solid state lighting and the emerging field of stretchable electronics which requires the assembly and electrical connection of semiconductor devices over exceedingly large area substrates.

Approaching Gas Phase Electrodeposition: Process and Optimization to Enable the Self‐Aligned Growth of 3D Nanobridge‐Based Interconnects

A nanowire bonding process referred to as gas-phase electrodeposition is reported to form nanobridge-based interconnects. The process is able to grow free-standing point-to-point electrical connections using metallic wires. As a demonstration, programmable interconnects and an interdigitated electrode array are shown. The process is more material efficient when compared with conventional vapor deposition since the material is directed to the point of use.

Millimeter Thin and Rubber‐Like Solid‐State Lighting Modules Fabricated Using Roll‐to‐Roll Fluidic Self‐Assembly and Lamination

A millimeter thin rubber-like solid-state lighting module is reported. The fabrication of the lighting module incorporates assembly and electrical connection of light-emitting diodes (LEDs). The assembly is achieved using a roll-to-roll fluidic self-assembly. The LEDs are sandwiched in-between a stretchable top and bottom electrode to relieve the mechanical stress. The top contact is realized using a lamination technique that eliminates wire-bonding.

Consequences of plasma oxidation and vacuum annealing on the chemical properties and electron accumulation of In2O3 surfaces

The influence of oxygen plasma treatments on the surface chemistry and electronic properties of unintentionally doped and Mg-doped In2O3(111) films grown by plasma-assisted molecular beam epitaxy or metal-organic chemical vapor deposition is studied by photoelectron spectroscopy. We evaluate the impact of semiconductor processing technology relevant treatments by an inductively coupled oxygen plasma on the electronic surface properties. In order to determine the underlying reaction processes and chemical changes during film surface–oxygen plasma interaction and to identify reasons for the induced electron depletion, in situ characterization was performed implementing a dielectric barrier discharge oxygen plasma as well as vacuum annealing. The strong depletion of the initial surface electron accumulation layer is identified to be caused by adsorption of reactive oxygen species, which induce an electron transfer from the semiconductor to localized adsorbate states. The chemical modification is found to be ...

Tuning Residual Stress in 3C-SiC(100) on Si(100)

Germanium modified silicon surfaces in combination with two step epitaxial growth technique consisting in conversion of the Si(100) substrate near surface region into 3C-SiC(100) followed by an epitaxial growth step allows the manipulation of the residual strain. The morphology and the residual strain in dependence on the Ge coverage are only affected by the Ge quantity and not by the growth technique. The positive effect of the Ge coverage is attributed to changes in the morphology during the conversion process, as well as to a reduced lattice and thermal mismatch between SiC and Si in consequence of alloying the near surface region of the Si substrate with Ge.

High-Resolution XRD Investigations of the Strain Reduction in 3C-SiC Thin Films Grown on Si (111) Substrates

In this work the biaxial stress of 3C-SiC thin films epitaxia lly grown on Si(111) substrates has been investigated by using x-ray diffraction methods. The influence of the resulting strain on the electrical properties of SiC/Si heterojunctions was an lyzed. Different methods to prepare the surface prior to the SiC deposition were compared: (i) ex situ carbonization, (ii) interface modification by deposition of Ge prior to epitaxial growth and (iii) annealing of the silicon surface. The x-ray measurements revealed the lowest strain in ex situ carbonized samples, showing a transition from tensile to compressive strain when off-axis substrates were used. The highest strain appeared in SiC layers grown on a thin Ge intermediate layer whi ch was deposited prior to SiC growth without an additional annealing step of the substrate. The strai n in the SiC layer is directly correlated with the reverse current through the heterojunction. Introduction Epitaxially grown mismatched semiconductor heterostructures are of increasing importance for microand optoelectronic devices or circuits. Lattice mismatched layers can be elastically strained by pseudomorphic growth on the substrate. Alternatively the strain can be relieved by relaxation of the epilayer due to formation of misfit dislocations resulting in a n in-plane lattice parameter of the epitaxial film close to that of the bulk material. If epitaxia l l yers of 3C-SiC are grown on Si substrates the large mismatch in the lattice constants and the thermal expansion coefficients lead to a substantial residual tensile strain. A significant part of the 20% mismatch in lattice constants can be released by the formation of a dislocation network. However, the mis match in thermal expansion coefficients of SiC and Si introduces an additional strain into the s yst m during the cooling down process after growth. This strain results in a strong degradation of the layer properties and a wafer warpage, limiting the use of SiC/Si hetrostructures for device a pplications and as pseudo substrate for the deposition of group III-nitrides. In this work we analyze the e ffect of different techniques to minimize the residual strain of the SiC layers and to improve the structural and electrical properties of the grown heterostructures. Experimental The 3C-SiC thin films (thickness ~120 nm) were grown by solid-source mol cular-beam epitaxy (MBE) on (111)-oriented onand off-axis Si crystal wafers at a substrate temperature of 1000°C with a growth rate around 1 nm/min. Prior to epitaxial growth the Si( 111) substrates were prepared by different methods. The first method uses an ex vacuo carbonization process at 1280°C in a propane-hydrogen atmosphere inside a rapid thermal processing (RTP) sy stem [1]. The MBE Materials Science Forum Online: 2003-09-15 ISSN: 1662-9752, Vols. 433-436, pp 233-236 doi:10.4028/www.scientific.net/MSF.433-436.233

Approaching Roll-to-Roll Fluidic Self-Assembly: Relevant Parameters, Machine Design, and Applications

This paper presents the implementation of an automated roll-to-roll fluidic self-assembly system based on the surface tension driven self-assembly with applications in the field of macroelectronics. The reported system incorporates automated agitation, web motion, component dispensing, and recycling. The process enables the assembly and electrical connection of semiconductor dies/chips in a continuous and parallel fashion over wide area substrates. At present, the method achieves an assembly rate of 15000 chips per hour and an assembly yield exceeding 99%, testing assembly of standard square-shaped dies, 300-1000 μm size. Scaling the system to any desired throughput is possible due to the parallel manner of selfassembly. The identification and the modeling of the relationship between process parameters and forces have been studied and experimentally verified by testing the effect of the web angle, agitation on assembly, and detachment rates. As an application, we demonstrate the realization of a solid-state lighting module. This particular application requires the assembly of a conductive multilayer sandwich structure, which is achieved by combining the introduced assembly process with a novel lamination step.