Two-photon polymerization (2PP) is now an established technique for nanofabrication. Conventional fabrication processes using laser 2PP commonly use a single point beam delivery system in order to write artifacts in the volume of a resin. Complex shapes such as micro-models, woodpile photonic structures and spiral structures have been realized in several material systems including, sol-gels, organically modified ceramics and resins. One area of current interest in 2PP micro fabrication is the introduction of more complex beam delivery systems, aimed at introducing a degree of parallel processing to the writing method. In this paper we describe two alternative parallel processing approaches to beam delivery that demonstrate the use of diffractive and refractive optics to shape the laser before focusing. Firstly a Fraunhofer diffractive optical element to generate a linear array of 4 spots of equal intensity thus writing four structures simultaneously. Secondly an axicon lens is used to form an annulus in the focal plane of the focusing element. This enables complete three dimensional annular structure fabrication without the use of scanning stages. For all experiments, a Ti:sapphire laser was used to initiate 2PP microfabrication. The materials system used was a Zr/PMMA hybrid prepared by the sol-gel method on a glass substrate.

The application of laser based materials processing for precision micro scale manufacturing in the electronics and fiber optic industry is becoming increasingly widespread and accepted. This presentation will review latest laser technologies available and discuss the issues to be considered in choosing the most appropriate laser and processing parameters. High repetition rate, short duration pulsed lasers have improved rapidly in recent years in terms of both performance and reliability enabling flexible, cost effective processing of many material types including metal, silicon, plastic, ceramic and glass. Demonstrating the relevance of laser micromachining, application examples where laser processing is in use for production will be presented, including miniaturization of surface mount capacitors by applying a laser technique for demetalization of tracks in the capacitor manufacturing process and high quality laser machining of fiber optics including stripping, cleaving and lensing, resulting in optical quality finishes without the need for traditional polishing. Applications include telecoms, biomedical and sensing. OpTek Systems was formed in 2000 and provide fully integrated systems and sub contract services for laser processes. They are headquartered in the UK and are establishing a presence in North America through a laser processing facility in South Carolina and sales office in the North East.

Laser supported processes can be used to modify the properties of ceramic substrates locally. These processes are characterised by a strong thermal interaction between the laser beam and the ceramic surface which leads to localised melting. During the dynamic melting process second phase particles are introduced into the melt pool in order to modify the physical properties. LTCC (Low Temperature Co-fired Ceramics)-substrates were laser alloyed and coated by laser cladding using nanoscaled powders of WO₃ and CuO. Depending on the process parameters and the powders used modified areas with different geometries could be fabricated with a complex multiphase microstructure. Particle agglomerates, small crystals as well as grains covered with reaction phase could be found inside the microstructure, in parts with typical length scales in the submicron range. The properties of the laser modified tracks differ significantly from that of the substrate. In particular the thermal and electrical properties were changed. An enhanced thermal conductivity could be detected in laser tracks alloyed with the nano-scaled CuO- and WO₃-powders. The electrical resistivity showed a semiconducting behaviour with a negative temperature coefficient, i.e. it decreases with increasing temperature.

The concept of combining the Laser MicroJet^(R) (LMJ) water jet-guided laser with a standard industrial diamond blade saw was first proposed early in 2006. The idea has now been taken a step forward with a joint project between Synova SA and Disco Hi-Tech Europe GmbH. The hybrid machine being developed integrates an LMJ module in place of the second blade saw on a Disco dual-spindle machine. The resulting machine will be fully capable of sequencing the different processes to carry out dicing of complex and layered semiconductors wafer, in any possible combination. It will be possible to program both processes to run independently in parallel or allow sequential operation during the same cutting pass. This extraordinary flexibility, combined with the speed advantages, quality of material cutting and simplification in processing in a fully automatic mode for up to 300 mm wafers, all now available in a single machine, will greatly benefit the manufacturing community. This paper will provide some insight into the design and operation of the hybrid machine and some examples of the improvements gained from its use.

Raman spectroscopy (RS) is a key tool to characterize residual stress in silicon devices because the vibrational frequencies of a silicon substrate change with its stress. However, due to the intrinsic optical diffraction limit, conventional micro-Raman spectroscopy can only have a probe resolution of around 1 μm², which is not sufficient for nanotechnology-oriented electronic industry. Low sensitivity is another problem to be solved to maximize the potential of this technique. In this study, a novel Raman spectrometer, which can overcome the optical diffraction limit, was built with the attempt to improve the resolution as well as the detection sensitivity. This approach instrument, which is based upon tip-enhanced near-field effects, has a nanoscale resolution by deploying a silver-coated tungsten tip mounted on a scanning tunneling microscope (STM) with side illumination optics. It features fast and reliable optical alignment, versatile sample adaptability and effective far-field signal suppression. The performance was evaluated by observing the enhancement effects on silicon substrates and single-walled carbon nanotubes (SWCNTs). It was found that apparent enhancement as high as 120% on silicon substrates could be achieved using the depolarization technique. It is believed that this technique is promising for future diagnosis of semiconductor materials and devices at nanoscales, especially for stress mapping of semiconductor devices.

The laser-induced cleavage of LCD glass is free from the generation of cullet and micro-crack, dispensing with the subsequent processes of grinding and cleansing. This paper deals with the theory and experiment of this technology which can improve the manufacturing of flat panel displays. Different from the preceding technology using CO₂ laser irradiation which can realize surface absorption and scribing only, we have realized the surface/inward absorption of laser beam inside glass by matching the absorption characteristics of glass and the emission wavelengths of appropriate lasers and have succeeded in realizing the full-body cleavage of LCD glass. We have also succeeded to develop the technologies, which can eliminate the shortcomings so far considered to be inherent to this full-body cleavage, i.e. size effect. The completion of the full-body cleavage in this way can simplify the manufacturing process of LCD.

A potential method for precise and fast dicing of display glass plates is proposed in this study. This technique facilitates the micromachining of cavities in both front and rear surfaces for a single pass of laser beam. The influences of focusing depth, input pulse energy, and scanning speed of the laser beam are investigated to study the morphology of the front and rear surface cavities. A commercial femtosecond laser with pulse duration of 172 fs, center wavelength of 780 nm, and repetition rate of 1 kHz is used for introducing the cavities.

Lighting applications like OLED or on silicon for electro-optical applications need a reproducible sealing process. The joining has to be strong, the permeability for gasses and humidity very low and the process itself has to be very localized not affecting any organic or electronic parts inside the sealed region. The actual sealing process using glue does not fulfil these industrial needs. A new joining process using ultra-fast laser radiation offers a very precise joining with geometry dimensions smaller than 50 μm. Ultra-fast laser radiation is absorbed by multi-photon absorption in the glass. Due to the very definite threshold for melting and ablation the process of localized heating can be controlled without cracking. Repeating the irradiation at times smaller than the heat diffusion time the temperature in the focus is increased by heat accumulation reaching melting of the glass. Mowing the substrate relatively to the laser beam generates a seal of re-solidified glass. Joining of glass is achieved by positioning the laser focus at the interface. A similar approach is used for glass-silicon joining. The investigations presented will demonstrate the joining geometry by microscopy of cross-sections achieved by welding two glass plates (Schott D263 and AF45) with focused IR femtosecond laser radiation (wavelength λ = 1045nm, repetition rate f = 1 MHz, pulse duration t_p = 500 fs, focus diameter w₀ = 4 μm, feeding velocity v= 1-10 mm/s). The strength of the welding seam is measured by tensile stress measurements and the gas and humidity is detected. A new diagnostic method for the on-line detection of the welding seam properties will be presented. Using a non-interferometric technique by quantitative phase microscopy the refractive index is measured during welding of glass in the time regime 0-2 μs. By calibration of the measured refractive index with a relation between refractive index and temperature a online-temperature detection can be achieved.

Global warming is a current topic all over the world. CO₂ emissions must be lowered to stop the already started climate change. Developing regenerative energy sources, like photovoltaics and fuel cells contributes to the solution of this problem. Innovative technologies and strategies need to be competitive with conventional energy sources. During the last years, the photovoltaic solar cell industry has experienced enormous growth. However, for solar cells to be competitive on the longer term, both an increase in efficiency as well as reduction in costs is necessary. An effective method to reduce costs of silicon solar cells is reducing the wafer thickness, because silicon makes up a large part of production costs. Consequently, contact free laser processing has a large advantage, because of the decrease in waste materials due to broken wafers as caused by other manufacturing processes. Additionally, many novel high efficiency solar cell concepts are only economically feasible with laser technology, e.g. for scribing silicon thin-film solar cells. This paper describes laser hole drilling, structuring and texturing of silicon wafer based solar cells and describes thin film solar cell scribing. Furthermore, different types of lasers are discussed with respect to processing quality and time.

Surface structuring with ultrashort laser pulses provides the flexibility to generate micro- and nano-sized structures in desired patterns on metal surfaces - also on non-flat objects. The structures largely preserve the strength of the native material, since they are formed with minimal thermal effects on the surrounding regions. This talk will demonstrate the capabilities with and flexibility of short-pulse surface structuring. Recent results encompass tailoring material surfaces for optimal adhesion in specific industrially important applications and laser structuring of medical implant surfaces to improve their biocompatibility.

Two types of laser patterning are of interest for application in microsystem technology: direct ablation of polymer material for the generation of two or three dimensional shapes such as microfluidic channels, curved shapes or micro-holes and alternatively photo-induced change of chemical or physical properties. An appropriate choice of laser and process parameters enables new approaches for the fabrication of lab-on-chip devices with integrated functionalities. We will present our current research results in laser-assisted ablation and modification of polystyrene (PS) with respect to the fabrication of polymer devices for high throughput planar patch clamping. Patch clamping is a highly sensitive technique used to measure the electrical activity of a cell. It is used in applications which include drug screening where there is demand for high throughput systems (HTS). While there are a few commercially available HTS patch clamping systems on the market using traditional patch clamping materials, there are no systems on the market using novel materials, or for dealing with cell networks - a physiologically important consideration for the developing fields of tissue engineering and understanding cell to cell interactions. This paper presents potential design approaches and processes for producing a polymer based automated patch clamping system. For this purpose laser micro-drilling of PS and subsequent surface functionalization was investigated as function of laser and process parameters. A high power ArF-excimer laser radiation source with pulse length of 20 ns (repetition rate up to 40 Hz) as well as high repetition ArF- and KrF-excimer laser sources with pulse lengths of 4-6 ns (repetition rates up to 500 Hz) were used in order to study the influence of laser pulse length on laser drilling and laser-induced surface modification. Micro-drilling of PS with diameters down to 1.5 μm were demonstrated. Furthermore the localized formation of chemical structures suitable for improved adhesion of single cells and cell networks was achieved on PS surfaces. A photolytic activation of specific areas of the polymer surface and subsequent oxidization in oxygen or ambient air leads to a chemically modified polymer surface bearing carboxylic acid groups well-suited for controlled competitive protein adsorption or protein immobilization. Finally, distinct areas for cell growth and adhesion are obtained. The combination of laser ablation and modification will be discussed for the laser-assisted fabrication of polymer devices for patch clamping.

We demonstrate the fabrication of three-dimensional (3-D) hollow microstructures embedded in photostructurable glass by a femtosecond (fs) laser direct writing. Fs laser direct writing followed by annealing and successive wet etching in dilute hydrofluoric (HF) acid solution resulted in the rapid manufacturing of microchips with 3-D hollow microstructures for the dynamic observation of living microorganisms in fresh water. The embedded microchannel structure enables us to analyze the continuous motion of Euglena gracilis. A microchamber with a movable microneedle demonstrates its ability for the elucidation of the information transmission process in Pleurosira laevis. Such microchips, referred to as nano-aquariums realize the efficient and highly functional observation of microorganisms.

The interference of three coherent laser beams of a HeCd-laser with a wavelength of 325 nm was used to create a periodic intensity distribution into the photo-resist AZ4562. The beam configuration for the laser beam interference was carefully chosen, so that well defined patterns of two-dimensional periodicity were generated in the photo-resist. Moulding tools were fabricated from the generated nano-structures via electroforming processes, allowing for a fast replication of the nano-structured surfaces via hot embossing. Hot embossed polymers were used to increase the effective surface of micro-fluidic devices like e.g. Polymerase-Chain-Reaction(PCR)-chips. The Nano-structured surfaces were characterized concerning their contact angles when wetted with de-ionized water. It was found that the nano-structures influenced the wetting behaviour of micro-fluidic chip surfaces clearly, especially Polypropylene (PP) surfaces showed a superhydrophobic behaviour.

Laser based joining technologies for optical assemblies overcome the limitations of standard fixation technologies such as adhesive or wafer level bonding. By applying the laser energy locally and for a limited time these technologies enable for higher stability of optical joints as well as additional functionality. Working without intermediate layers laser splicing creates highly stable transparent joints that are suitable for the transmission of high power, e.g. in fiber laser assemblies. In contrast, laser beam soldering of optical components as an alternative with a metallic intermediate layer is non-transparent, but creates flexible and stress-compensating joints as well as thermal and electrical interconnects.

We demonstrate a laser-based micro-bonding method for Vertical Cavity Surface Emitting Lasers (VCSELs) that enables practically sufficient joint strength, while securing the output power before bonding. VCSELs have great potential for optical interconnects because of their low threshold current and high-speed modulation capability. As for packaging of VCSELs, flip-chip bonding (FCB), among others, has been investigated because it facilitates the coupling of laser emission into fibers and waveguides. Conventional schemes for FCB, however, entail thermo-compressing stages and therefore the thermal and mechanical stresses involved are prone to cause defects in the lasing media, leading to quality defects. To overcome this problem, we have come up with a modified FCB method that can reduce such stress by employing laser irradiation to efficiently heat joints minimizing heat-affected regions. A micro-bonding system used in the experiments has an infrared fiber laser for heating, a diffractive beam splitter for parallel processing, a mounting head, and a slider for precise alignment and translation. VCSEL pads are kept in contact with counter pads on a substrate with AuSn solder placed between them. The split and focused beams by the element are guided to strike the joining points through the substrate, heating and melting the solder to attain a tight joint.

The requirement to make low profile ohmic contacts to a piezo-resistive MEMS pressure sensor has highlighted limitations of ultrasonic wire bonding technology. Wire bonding typically uses 25-50 μm diameter gold or aluminium wire and ultrasonic welding to the contact pads of micro-electronic devices results in a contact wire proud of the pad surface. If the application involves the MEMS pressure sensor and contacts being encapsulated, then repetitive changes in pressure flexing the contact wires can lead to fracture. A possible solution is to scale down laser welding technology to fuse materials at the micron scale. For this purpose a precision ophthalmic surgical laser system has been modified to investigate optimum conditions for laser welding, both at the micron scale and for the typical geometries involved. Typical requirements involve a cylindrical contact wire to be bonded to a thin contact pad on the MEMS device. Since the pad size is of similar dimension to the wire, and the requirement for a low profile stable configuration, a keyhole welding strategy is required. The Nd:YAG based ophthalmic laser has been modified, the Q-switch removed and the output pulse width and energy controlled principally via control of the flashlamp.

A laser based process was developed for brazing different ceramics to steel with the focus on the improvement of the wetting behavior of silicon carbide SSiC which exhibits a poor wetting behavior in comparison to oxide ceramics. Therefore, the wetting behavior of this SSiC was investigated with different active braze fillers in detail. Two commercially available braze fillers were used, an AgCuTi - foil and an AgCuInTi - foil and SnAgTi - pellets produced in our institute in varying compositions were examined concerning their wetting and joining behavior towards SSiC. For improving the wetting behavior surface structures and conditioning were diversified additionally. The ceramic - steel - compounds were heated up by CO₂ - laser - scanning - system. The steel sided heating calms the thermal shock for the ceramic sample and the local heat input concentrating on the joining area reduces the compound stresses to a minimum. The interfacial areas of the wetted ceramic surfaces and of the joined ceramic - steel systems were evaluated by microscopic investigations of polished cross-sections. For a better understanding of the brazing process measurements with a differential scanning calorimeter (DSC) have been performed. Moreover the compound strength of the brazed joints was determined by shear tests. In context of the strength investigations the influence of different laser induced structures (Nd:YAG) of the ceramic surfaces on the shear strength was evaluated.

Pulsed-laser deposition (PLD) is an excellent technique to grow thin films and multi-layers of complex oxide materials. We present our recent results on deposition, characterization and nano-patterning of novel oxide high-temperature superconductors (HTS) and piezoelectric materials. HTS thin films of improved superconducting properties are fabricated from ceramic targets consisting of Y₂Ba₄CuMO_y (M = metal) nano-particles embedded in YBa₂Cu₃O₇ (YBCO) matrix. The nano-composite ceramics are UV-laser ablated and the optical plasma emission is monitored by laser - induced breakdown spectroscopy. The HTS films reveal superconducting critical current densities that depend on target composition and are strongly enhanced as compared to phase pure YBCO films. Application of HTS layers in future nano-electronic devices requires novel techniques for nano-patterning. Masked ion-beam structuring enables the nano-patterning of YBCO thin films in a direct and single-step process. Gallium orthophosphate (GaPO₄) thin films and piezoelectric ZnO multi-layers are reported also. GaPO₄ is an outstanding piezoelectric material with very high transition temperature (~ 970 °C). Epitaxial GaPO₄ films are fabricated on quartz substrates by PLD and thermal post-annealing. Long-term annealing at high temperature does not degrade the GaPO₄ films. Multi-layers of Al and Li doped ZnO are pulsed-laser deposited on various substrates and investigated for applications in thin film sensors.

Pulsed-laser deposition (PLD) is a versatile technique for thin film deposition. The generation and propagation of laser-induced plasmas have been extensively studied. Other plasma sources have been combined with PLD to improve the film qualities. The knowledge about the interactions between the laser-induced plasmas and additional plasmas and their effects on film growth is still limited. We have investigated the optical emission spectra from the interaction region of low-pressure ECR microwave plasmas and pulsed-laser-induced plasmas. In this region, the spatial and temporal distributions of the laser-ablated species were altered while very few collisions were expected in the ambient gas due to the low pressure. The results were compared with those with laser ablation or ECR microwave discharge along. The mechanisms and effects of the interactions were discussed.

Excited C₂ and CH species occur abundantly in diamond growth using C₂H₂/O₂, C₂H₂/C₂H₄/O₂ and C₂H₄/O₂ flames. The irradiation of some flames by a continuous-wave (CW) CO₂ laser beam has resulted in increased optical emission intensity from the excited species and a change in the physical appearance of the flames due to resonant absorption of laser energy. Gas temperature in the flames is one of the most important parameters in the application of diamond growth. In atmospheric plasmas, the gas kinetic temperature is closely related to the rotational temperature of radical species in the plasmas. Optical emission spectroscopy (OES) was used to obtain molecular spectra of the excited C₂ and CH species in the flames for a fixed gas of C₂H₂/C₂H₄/O₂ flame at several laser energies. The rotational temperatures of CH were calculated using the Boltzmann plot method. In addition, synthetic C₂ molecular spectra were compared with the experimental spectra to obtain temperature by the intensity ratio of selected spectrum components. For each condition, the temperatures obtained using these methods were correlated with the quality, grain size, and growth speed of diamond films on cemented tungsten carbide (WC-Co) substrates.

Controllable growth of self-aligned single-walled carbon nanotubes (SWNTs) was developed using laser-assisted chemical vapor deposition (LCVD) method. By integrating both electrical-field and gas-flow induced orientation effects in the LCVD process, SWNT growth direction was decided. According to Raman measurements, narrow diameter distribution of the SWNTs was realized by controlling reaction temperature and catalyst size. Individual SWNT bridging opposite Mo electrodes was achieved by creating local electrical field using point-to-point electrodes. Back-gated single-walled carbon nanotube based field-effect transistors (SWNT-FETs) were fabricated using LCVD method, and showed typical p-type behavior.

SiO₂-TiO₂ planar optical waveguides are fabricated on silicon wafer substrate by dip-coating technique with the Sol-Gel solutions, based on which the stripe optical waveguides are patterned by laser direct writing of the Sol-Gel films using an Ytterbium fiber laser and followed by chemical etching. The effects of the laser processing parameters on the microstructure of the core layer films are investigated. The relative chemical etching rates of the non-irradiated area in Sol-Gel films that are haeted at different temperature are characterized. The optical fields and propagation losses of the optical waveguides at the wavelength of 1550 nm are characterized by multi-channel fiber/waveguides coupling system. The experimental results demonstrate that the composition, the post heat treatment temperature and laser power density have a big effect on the widths of the stripe optical waveguides, and the minimum widths about 25 μm can be fabricated with the suitable parameters. The core layer of the planar optical waveguides as received by Sol-Gel method is loose in structure, and a shrinkage concave groove forms in the laser irradiated area. The microstructure and forming mechanisms of the stripe waveguides by laser direct writing Sol-Gel films are discussed. The minimum propagation loss of the fabricated stripe waveguides is about 1.77dB/cm at 1550nm. Better results are expected by improving the film composition and laser processing parameters further.

Laser direct micro-machining processes are used in a variety of industries like inkjet printing, semiconductor processing, solar technology, flat-panel display production and medicine. Various kinds of materials, e.g. ceramics, metals, isolators, oxides, organics and semiconductors are being structured. In most cases pulsed single mode solid state lasers with an inhomogeneous Gaussian beam profile are employed, like YAG lasers and their harmonics. However, the quality and functionality of the generated structures and micro-systems as well as the speed of the process can be improved by the utilization of homogeneous top hat profiles. The beam shaping principle of refractive Gaussian-to-top-hat converters is shown. Compact beam shaper modules based on this principle have been developed - supporting most direct laser micro-machining applications. The resulting process advantages are demonstrated by selected application results, namely the drilling of holes and patterning of trenches for different kinds of materials.

We describe maskless rapid prototyping of a micro-fluidic branching network on a silicon wafer with laser direct writing (LDW). The branching micro-channel network is designed as a blood oxygenator following Murray's law and satisfying the necessity of equal path lengths. In development of such micro-fluidic structures, this maskless process will reduce time and cost compared with the conventional photolithography based technique. The flexibility of laser direct writing facilitates creating a multi-depth structure of the branching network, ranging from a few microns to a few hundred microns in depth. In order to create such a wide range of feature sizes, a nanosecond pulsed Nd-YAG laser and a femtosecond pulsed fiber laser are used together. The femtosecond fiber laser is used to create micro-channels with a depth of less than 50μm. As post-processing, a chemical etching in a solution of HF and HNO3 is applied to smooth the laser ablated surface. To realize an optimized design of micro-fluidic structures, influences of operating parameters, such as the pulse energy, the focal position, the transverse speed, and the number of passes, on the depth of micro-channels and their surface quality are investigated. Using the laser machined silicon structures as a mold, a Poly(dimethylsiloxane) (PDMS) replica is created.

This paper will present the direct photo patterning of micro circuits and sensors with a XeCl excimer laser photo ablation system. The working principle and the ablation equipment for photo ablation of conductive thin film on polymer are described. Both large sheets and reel-to-reel webs can be ablated on this excimer laser photo ablation system. The ablation strategies and alignment strategies for the micro circuits and sensors are introduced. The test results show ablation results with high resolution, high throughput, high yield and cost-efficiency. This clearly shows that excimer laser photo ablation of the conductive materials on polymer substrates is a good choice for industrial mass product fabrication of low priced, disposable micro circuit and sensor devices.