This PDF file contains the front matter associated with SPIE Proceedings Volume 7590, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Ultrafast pulsed laser ablation is employed in laser-induced backward transfer for printing on transparent media. By combining a high pulse repetition rate of 1 MHz and an ultrashort pulse duration of 700 fs in an ultrafast fiber laser, we demonstrate printing of bitmap images and vector graphics with nearly continuous gray scales and high linear printing speeds up to 10 m/s. In addition, we find that the printing process preserves several original functional properties of the target material, and as an example of functional printing, we demonstrate printing of phosphorescent images.

The stochastic effects of assist gas in QCW and pulsed laser machining (percussion drilling) in steel are measured with a novel in situ high speed low coherence imaging system. Real-time imaging is delivered coaxially with machining energy and assist gas revealing relaxation and melt flow dynamics over microsecond timescales and millimeter length scales with ~10 micrometer resolution. Direct measurement of cut rate and repeatability avoids post cut analysis and iterative process development. Feedback from the imaging system can be used to overcome variations in relaxation and guides blind hole cutting.

In recent years, a major interest in surface as well as bulk property modification of semiconductors using laser irradiation has developed. A.Kar et al. [1][2] and E.Mazur et al. [3] have shown introduction and control of dopants by long-pulse laser irradiation and increased absorption due to femtosecond irradiation respectively. With the development of mid-IR sources, a new avenue of irradiation can be established in a spectral region where the semiconductor material is highly transparent to the laser radiation. The characterization of the light-matter-interaction in this regime is of major interest. We will present a study on GaAs and its property changes due to pulsed laser irradiation ranging from the visible to the mid-IR region of the spectrum. Long-pulse as well as ultra-short pulse radiation is used to modify the material. Parameters such as ablation threshold, radiation penetration depth and thermal diffusion will be discussed.

Radial and azimuthal polarizations have attracted new interest in the process development community due to improved beam propagation and absorption conditions in the ablation cavity. This paper presents our recent activities and results on polarization converted ultrashort laser pulses by use of segmented half-wave-plates for the generation of ripple structures with predetermined sub-patterns. The formation of ripples fabricated in metals, ceramics, and semiconductors is analyzed by the morphological investigation of the structures (spacing and orientation) as a function of the polarization state of the laser beam.

Lasers are used in micro manufacturing and microwelding applications. Manufacturing in micrometer scale features requires good laser beam properties, but also the axes of the laser machining system have to be accurate. One of the possible technologies is a scanner. Scanners are equipped often with galvanometric actuators, which enable accurate beam movement by changing the beam angle with mirrors and focusing the beam with a scanner lens. Both actuators and lens cause inaccuracy in the system. The optical shape of the lens is not ideal due to structure of the lens and lens grinding. Actuator performance is not ideal. One of the biggest reasons for scan angle error is drift, caused, for instance, by temperature changes. Because of these facts, laser scanner systems have to be calibrated regularly when at least some degree of accuracy is needed. In this paper is presented a solution to compensate the entire working field of the scanner accurately, and calibrate the scanner field to match the actual working field. In the calibration process, distortions are first compensated with parameter changes and after that more accurately by marking a point matrix, measuring the locations of points and generating a new correction file. According to experimental results good accuracy can be achieved using the method.

Thick multi-layer metal stacking offers the potential for fabrication of rectangular waveguide components, including horn antennas, couplers, and bends, for operation at terahertz frequencies, which are too small to machine traditionally. Air-filled, TE10, rectangular waveguides for 3 THz operation were fabricated using two stacked electroplated gold layers on both planar and non-planar substrates. The initial layer of lithography and electroplating defined 37 micrometer tall waveguide walls in both straight and meandering geometries. The second layer, processed on top of the first, defined 33 micrometer thick waveguide lids. Release holes periodically spaced along the center of the lids improved resist clearing from inside of the electroformed rectangular channels. Processing tests of hollow structures on optically clear, lithium disilicate substrates allowed confirmation of resist removal by backside inspection.

Six microlens arrays are fabricated in a single step process using diamond milling techniques, plunging and micromilling. Four of the lenses are cut using plunging, two each in poly(methyl methacrylate) and polystyrene (Rexolite 1422), and the other two are cut in polystyrene using 3D micro-milling. Half of the lenses are concave and the other half are convex. These are high power lenses having steep sag at the edges and radii between 2.0 - 2.1 mm for each array. The clear aperture diameters of the lenses are about 3.2 mm for plunged lenses and 2.6 mm for micro-milled lenses. The lenses are spaced 4 mm apart in a square grid. Setup and method of these techniques is described and the lens arrays are characterized based on radius (power) error, wavefront error, roughness, and grid position error. Micro-milled lenses are shown to be of high optical quality compared with standards for injection molded plastic lenses.

Diamond turning of steel parts is conventionally not possible due to the high tool wear. However this process would enable several different application with high economical innovative potential. One technology that enables the direct manufacturing of steel components with monocrystalline diamond is the ultrasonic assisted diamond turning process. This technology has been investigated over years within the Fraunhofer IPT and has proven its potential. Surface roughness in the range of Ra = 5 nm are reached and the diamond wear is reduced by a factor 100 or higher. Up to now this process has been investigated in lab conditions manufacturing only plane surfaces. In order to prove its industrial suitability, two relevant aspherical shapes, convex and concave respectively, have been defined and manufactured. The reached form accuracies and surface roughness values will be described in this paper.

For mass production of multiscale-optical components, micro- and nanostructured moulding tools are needed. Metal tools are used for hot embossing or injection moulding of microcomponents in plastics. Tools are typically produced by classical forming processes such as mechanical manufacturing e.g. turning or milling, laser manufacturing or electrical discharge machining (EDM). Microstructures with extremely tight specifications, e.g. low side wall roughness and high aspect ratios are generally made by lithographic procedures such as LIGA or DPW technology. However, these processes are unsuitable for low-cost mass production. They are limited by the exposure area and structure design. In cooperation with international partners alternative manufacturing methods of moulding tools have been developed at the Institute of Microstructure Technology (IMT). In a new replication procedure, mould inserts are fabricated using micro- and nanoscale optics. The multiscale structured prototypes, either in plastics, glass, metal or material combinations are used as sacrificial parts. Using joining technology, electroforming and EDM technology, a negative copy of a prototype is transferred into metal to be used as a moulding tool. The benefits of this replication technique are rapid and economical production of moulding tools with extremely precise micro- and nanostructures, large structured area and long tool life. Low-cost mass replication is possible with these moulding tools. In this paper, an established manufacturing chain will be presented. Multiscale and multimaterial optical prototypes e.g. out-of-plane coupler or microinterferometer were made by DPW or laser technology. The mould insert fabrication of each individual manufacturing step will be shown. The process reliability and suitability for mass production was tested by hot embossing.

In this work we report one simple fabrication process to build incandescent microlamps over silicon microtips. By taking advantage of the underetch observed when the Si substrate is anisotropically etched in KOH solutions, specific silicon microtips are created which serve as mechanical supports for the incandescent light sources. A thin film of chrome is deposited by sputtering technique above the microtip and defined by photolitography in order to create an electrical resistance. Consequently, the electrical energy transformed in heat is concentrated in a small spot achieving temperatures high enough to produce incandescent light similar to a blackbody spectrum. To reduce the heat loss caused by the high thermal conductivity of silicon, a layer of silicon dioxide (SiO₂) placed between substrate and metal was necessary to avoid the use of large electrical currents to generate the incandescence in the light source. A SiO₂ film is also used as a protection layer against moisture and specially oxygen, since at high temperatures chrome can easily oxidize losing its electrical conductivity. As the microtips are very tall compared to photoresist thickness, the lift-off process was needed in order to guarantee that the top of the microtip would be covered by chrome. The results showed that it is possible to produce light in all visible spectrum by applying electrical power higher than 4 W.

The plating characteristics of a commercially available indium plating solution are examined and optimized to help meet the increasing performance demands of integrated circuits requiring substantial numbers of electrical interconnections over large areas. Current fabrication techniques rely on evaporation of soft metals, such as indium, into lift-off resist profiles. This becomes increasingly difficult to accomplish as pitches decrease and aspect ratios increase. To minimize pixel dimensions and maximize the number of pixels per unit area, lithography and electrochemical deposition (ECD) of indium has been investigated. Pulse ECD offers the capability of improving large area uniformity ideal for large area device hybridization. Electrochemical experimentation into lithographically patterned molds allow for large areas of bumps to be fabricated for low temperature indium to indium bonds. The galvanic pulse profile, in conjunction with the bath configuration, determines the uniformity of the plated array. This pulse is manipulated to produce optimal properties for hybridizing arrays of aligned and bonded indium bumps. The physical properties of the indium bump arrays are examined using a white light interferometer, a SEM and tensile pull testing. This paper provides details from the electroplating processes as well as conclusions leading to optimized plating conditions.

As devices continue to increase in density and complexity, ever more stringent specifications are placed on the wafer scale equipment manufacturers to produce higher quality and higher output. This results in greater investment and more resource being diverted into producing tools and processes which can meet the latest demanding criteria. Substrate materials employed in the fabrication process range from Silicon through InP and include GaAs, InSb and other optical networking or waveguide materials. With this diversity of substrate materials presented, controlling the geometries and surfaces grows progressively more challenging. This article highlights the key parameters which require close monitoring and control in order to produce highly precise wafers as part of the fabrication process. Several as cut and commercially available standard polished wafer materials were used in empirical trials to test tooling options in generating high levels of geometric control over the dimensions while producing high quality surface finishes. Specific attention was given to the measurement and control of: flatness; parallelism/TTV; surface roughness and final target thickness as common specifications required by the industry. By combining the process variables of: plate speed, download pressure, slurry flow rate and concentration, pad type and wafer travel path across the polish pad, the effect of altering these variables was recorded and analysed to realize the optimum process conditions for the materials under test. The results being then used to design improved methods and tooling for the thinning and polishing of photonic materials applied to MOEMS-MEMS device fabrication.

TiO₂ nano-particles of anatase, useful as photosensitive initiators to induce free radical polymerization in acrylic monomers have been prepared by chemical synthesis. Appropriate surface modification of TiO₂ has been achieved to compatibilise the particles with the acrylic monomers to obtain an almost homogeneous distribution down to the primary particle size. The surface modification has been additionally fine tuned in such a way, that an efficient transfer of the electrons generated on TiO₂ during UV-exposure towards the monomer mixture could be achieved in order to start the polymerization reaction. In this direction, particles have been synthesized in-situ and ex-situ with the acrylic matrix using different precursors and surface modifiers. Ex-situ produced particles had to be dispersed finally into the acrylate monomer mixture. Residual solvent has been removed by distillation. The formation of the anatase modification could be shown by XRD. Particle sizes were determined by PCS, which showed a distribution between 1-10 nm depending on the used preparation method. Transmission electron microscopy prepared from the UV-polymerized coating layers proved the homogeneous distribution of the anatase nano-particles. Kinetic investigations on the photo-polymerization behavior have been accomplished by photo-DSC and IR. Curing time was determined in dependence on the materials composition.

In the present work the scope of using micro-electro discharge machining (micro-EDM) technique to generate metalnanoparticles is studied and thermal conductivity of the fluid with particles generated using micro-EDM is characterized. In the experiment, aluminum workpiece is machined with an aluminum tool electrode in deionized water. 40 to 96 V is applied for machining with pulse-on duration being varied between 10 and 100 microseconds. The particle count analysis reveals that low voltage and high pulse-on duration favors formation of smaller sized particles, as predicted by the developed model. A thermal conductivity measurements show 4% rise in thermal conductivity with the sample (0.004% by wt. in deionized water) produced by micro-EDM setup.

A micro-electro-discharge machine (Micro EDM) was developed incorporating a piezoactuated direct drive tool feed mechanism for micromachining of Silicon using a copper tool. Tool and workpiece materials are removed during Micro EDM process which demand for a tool wear compensation technique to reach the specified depth of machining on the workpiece. An in-situ axial tool wear and machining depth measurement system is developed to investigate axial wear ratio variations with machining depth. Stepwise micromachining experiments on silicon wafer were performed to investigate the variations in the silicon removal and tool wear depths with increase in tool feed. Based on these experimental data, a tool wear compensation method is proposed to reach the desired depth of micromachining on silicon using copper tool. Micromachining experiments are performed with the proposed tool wear compensation method and a maximum workpiece machining depth variation of 6% was observed.

Thermal oxidation of silicon is an important process step in MEMS device fabrication. Thicker oxide layers are often used as structural components and can take days or weeks to grow, causing high gas costs, maintenance issues, and a process bottleneck. Pyrolytic steam, which is generated from hydrogen and oxygen combustion, was the default process, but has serious drawbacks: cost, safety, particles, permitting, reduced growth rate, rapid hydrogen consumption, component breakdown and limited steam flow rates. Results from data collected over a 24 month period by a MEMS manufacturer supports replacement of pyrolytic torches with RASIRC Steamer technology to reduce process cycle time and enable expansion previously limited by local hydrogen permitting. Data was gathered to determine whether Steamers can meet or exceed pyrolytic torch performance. The RASIRC Steamer uses de-ionized water as its steam source, eliminating dependence on hydrogen and oxygen. A non-porous hydrophilic membrane selectively allows water vapor to pass. All other molecules are greatly restricted, so contaminants in water such as dissolved gases, ions, total organic compounds (TOC), particles, and metals can be removed in the steam phase. The MEMS manufacturer improved growth rate by 7% over the growth range from 1μm to 3.5μm. Over a four month period, wafer uniformity, refractive index, wafer stress, and etch rate were tracked with no significant difference found. The elimination of hydrogen generated a four-month return on investment (ROI). Mean time between failure (MTBF) was increased from 3 weeks to 32 weeks based on three Steamers operating over eight months.

Zinc oxide is used in many applications thanks to its various characteristics as well as photoresistivity, piezoelectricity, wide band gap for power components but also its capability for gas detection. In this article, we first present new process based on ZnO nanoparticles from Sigma Aldrich manufacturer; a stable ink obtained by mixing 10% weight of commercial powder with ethylene glycol, has been deposited by ink-jet printing on a silicon oxide substrate covered by platinum interdigitated electrodes. To obtain homogeneous deposits of nanoparticles, the working area of the sensor was bounded by functionalisation by the n-Octadecyltrichlorosilane. These deposits were optimized at 65°C. Then, the study was focused on the correlation between parameters of deposit and global resistance and gas sensitivity: conductivity for different operating temperatures under methane and isopropyl alcohol vapours. The best results have been obtained for thicknesses in the range of 0.5 and 2.5 μm. The ZnO resistance is stable under gas from 200°C and the relative sensitivity to methane and isopropyl alcohol are maximum and opposite at 225°C and 300°C respectively. This work shows that ink-jet is a promising technique to manufacture a new generation of low cost gas sensors at lower temperature deposition.

Microcontact printing (μCP) was successfully used to micropattern electrodes on large area substrates. An A4-size (210 mm × 297 mm) polydimethylsiloxane (PDMS) elastomer stamp was easily fabricated using an electroformed nickel mold. The micropatterns of poly(3,4-ethylenedioxythiophene)/poly(4-stylenesulfonate) (PEDOT/PSS) and silver (Ag) thin films, which were under 10 μm in width, were fabricated by transferring the thin films on the PDMS elastomer stamp to another substrate by μCP. Bottom contact (BC) organic thin film transistors (OTFTs) with PEDOT/PSS were fabricated as source and drain electrodes. The successful operation of fabricated OTFTs with a channel length of 10 μm was demonstrated. Results show that μCP is a promising process for use with various devices that require micropatterning on large area substrates.

Currently, sapphire is widely used in the field of optoelectronic devices and micro-mechanical components. One of the problems in using sapphire is the difficulty in cutting and micro-structuring due to the hardness of sapphire itself. In this paper, laser micromachining characteristics of sapphire are investigated using 157nm DUV laser micro-ablation system. Under laser fluence of 3-4 J/cm², the maximum ablation rate could reach to 400nm/s. For 3D laser ablation, it is necessary to select a proper combination of process parameters. Several 3D micro-structures are produced in sapphire wafers and sapphire fibers. As a whole, the ablation equality is good for use.