We present studies of the consequences of simultaneous exposure of inorganic single crystals to radiation and water. The first case consists of a biomineral namely CaHPO₄ 2H₂O which is a wide band gap, hydrated inorganic single crystal. We examine the laser induced ion and neutral emissions accompanying 248-cm excimer laser radiation. Both types of emission are several orders of magnitude higher following exposure to 2 keV electrons at current densities of 200 (mu) A/cm² and dose of 10²- 10³ mC/cm². We show that the enhancements in emission are strongly correlated with e-beam induced morphology changes on this unusual surface. We then examine similar effects on 'dry' crystals such as NaCl and NaNO₃ which are exposed to 10^-5 Pa partial pressures of H₂O. Again dramatic enhancements in radiation induced emissions are exhibited along with the generation of unique morphological structures with nanometer scale dimensions.

With the widespread application of excimer lasers for micro- processing, optically transparent materials in the UV region have become more important as optical components. The transparent materials currently available commercially are silica glass and fluoride crystals, CaF₂ and MgF₂. The resistance of these materials against cumulative irradiation of excimer lasers is required from the viewpoint of application, and it is important to clarify the mechanisms of the optical damage on these materials. In this paper, we report the onset of laser ablation, that is, the initiation of optical breakdown and plume formation, in CaF₂ crystal under cumulative irradiation of an ArF excimer laser. When the laser fluence is below the ablation threshold, a blue luminescence due to self-trapped exciton is observed from the whole laser-irradiated region. When the fluence ins increased near the threshold, successive irradiation finally cause a bright, localized luminescence due to the initiation of laser ablation. SEM images of the laser-damaged region show two features: (1) a small bump with pits of the order of 0.1 micrometers formed by UV laser absorption and following local heating, (2) small cracks with triangular fragments caused by mechanisms stress under local heating.

We have developed a new visualization technique named as re- decomposition laser-induced fluorescence (ReD-LIF) technique, clusters or nano-particles synthesized in the laser ablation plume are decomposed by laser irradiation and the atoms generated by the decomposition are visualized by LIF. This technique is very sensitive than the other visualization technique, because we can use the sensitive LIF technique. Decomposition of nano-particles by the laser irradiation is considered theoretically and the characteristics of ReD-LIF technique are compared with other visualization techniques such as laser-induced fluorescence and Rayleigh scattering. The ReD-LIF technique has been applied for the visualization of the Si nano-particle synthesis process. Based on the result, the particle dynamics in the ablation plume generated in the background gas during Si nano-particle synthesis are described besides the basic characteristics of the ReD-LIF signal.

The experimental studies of laser-induced plasma accompanying the laser ablation of material have been conducted with the developed shadow-interferometric technique. High intensity single picosecond pulses of YAP:Nd laser were applied to ablate tested samples and time-delayed probing pulses of second harmonic illuminating the interaction area were used to make snap-shots of the expanded plasma plume. Both shadow and interferometric images of hot plasma were captured simultaneously with a CCD camera providing approximately equals 1.5 micron spatial and approximately equals 10 ps temporal resolution of the investigated processes. By varying the intensity of ablating pulses and the time-delay of probing pulses it was possible to study a highly inhomogeneous small-scaled plasma density and refractive index distribution within the plume. The longer time-delays allowed study of laser-initiated shock wave expansion in the surrounding atmosphere. A special attention was paid to the plasma formation arising at a through-hole laser drilling process was observed. In particular, it was shown that the cluster explosion can efficiently block the laser radiation resulting in decreasing the ablation rate. A computer modeling of optical visualization of small-scale plasma objects has been conducted. The analysis si of the experimental and numerical results has revealed a number of characteristic features of plasma images that should be taken into account at the qualitative and quantitative evaluations of the plasma parameters.

Laser ablation of polyimide and polycarbonate by 3rd harmonic Nd-YAG laser is studied using secondary ion mass spectrometry (SIMS) and confocal microcopy. The ablated debris' were collected on an H-terminated Si substrate and then analyzed using SIMS. Mass resolved images of collected debris showed near-hemispherical distribution of hydrocarbon, nitrogen containing compounds with radius up to 0.7 mm. Ablation in different gases revealed that the nitrogen and oxygen containing compounds are formed because of a reaction of the hot plume with air in the course of thermal dissociation of O₂ and oxygen-assisted dissociation of N₂. The shape and size of the microvia were measured using confocal microscopy through a polished edge of the polymer target. The via drilled in pulse-by- pulse ablation (PBPA) was found to be deeper than that drilled in continuous ablation (CA) with the same number of pulses. This is due to shading of the laser light by the plume from the preceding pulse. In result, explosive boiling occurs during PBPA, while normal vaporization dominates during CA. Several mechanisms of etching of side walls are discussed.

The material transfer from the target to the substrate involved in pulsed laser deposition is described with respect to chemical reactions in the processing gas atmosphere in order to derive the laser parameters and the processing variables necessary for the deposition to thin films with application-adapted properties. The heating and removal are described by the conversion of the optical energy into internal energy followed by a phase transition form the condensed to the gaseous state. The delivered energy becomes distributed into different channels of decomposition in accordance to the temperature. The dynamics of the volatile species is calculated by the use of non- dissipative continuum mechanical equations of the conversion laws of mass, momentum, and energy. The flow field patterns of the gas phase during the material transfer of the polymers PE, PP and PMMA and the ceramic Al₂O₃ are calculated. The modeling calculating are direction towards the spatial and temporal dependence of the total and partial pressures either of the materials to be processed or of the processing gas species. The mathematical models are applied to the polymers PE, PP, and PMMA and to the ceramic Al₂O₃ following the chemical composition in thermodynamic equilibrium. The main emphasis of the calculations is to derive parameters and processing variables for pulsed laser film deposition in the case of other material properties.

Surface of solids play a leading role in any process of interaction between solids, solids-liquids, solids-gases and solids-plasma. Microgeometry is a key parameter of the solids surface which influence a lot mechanical, optical, electronic, chemical, thermical and other characteristics. Nowadays the laser-based technologies is a great challenge to improve a surface microgeometry (SM) quality and controllability. Different laser-based surface processing are considered: (i) surface microstructuring and control of roughness by laser ablation; (ii) surface microstructuring based on creation of surface electromagnetic waves (SEW) and surface periodic structures (SPS); (iii) surface smoothing and microstructuring based on laser heating til melting and further phenomena in a melted phase. Some examples of laser applications to improve optical, tribological and other surface characteristic are considered and analyzed. Future prospects of this field are discussed.

Highly accurate resistances can be made by iteratively laser inducing diffusion of dopants from the drain and source of a gateless field effect transistor into the channel, thereby forming an electrical link between two adjacent p-n junction diodes. We show that the current-voltage characteristics of these new microdevices are linear at low voltages and sublinear at higher voltages where carrier mobility is affected by the presence of high fields. A process model is proposed involving the calculation of the laser melted region in which the dopant diffusion occurs. Experimental results are well described by the proposed model.

Photoluminescence analysis has been implemented to investigate the crystalline properties of Gallium Nitride layers ablated with an XeCl excimer laser. The measurements were carried out on craters up to 1 micrometers deep, which corresponded to almost half the thickness of the deposited film. The craters were etched in an air environment with laser fluences in the range of 99-231 mJ/cm². In the 350-1200 nm spectral range, the near-band-edge emission, and the donor-acceptor pair recombination were identified. All spectra were dominated by the excitonic recombination. The analysis revealed that during the ablation, the full width at half maximum of the donor-bound luminescence line remained almost independent of both the depth of the crater and of the laser fluence. Also, the donor-acceptor pari recombination, which manifests its presence through a weak yellow luminescence observed in the vicinity of the 600 nm wavelength, has been consistently observed in the spectra. A relative decrease in the excitonic emission indicated that a thin layer of altered material with lower crystalline quality was formed at the surface of the ablated material.

Excimer-based ablative patterning of Indium Tin Oxide (ITO) thin film on flexible substrates has been evaluated for large format display applications. In display package manufacturing, excimer-based ITO ablation can provide a great advantage over conventional photolithographic processing. It can eliminate many steps from the manufacturing cycle, resulting in significant cost reduction. Flexible substrate display packaging is desirable for at least two reasons. It allows roll-to-roll low cost, large volume manufacturing. Its low weight provides for an easy scale up to larger format displays. An XeCl excimer, 1x, amplitude mask pattern projection, scan-and-repeat system was utilized in the evaluation work. The mask pattern had line groupings of line-widths varying from 8 to 30 micrometers with line length of 44 mm. Lines from all the groupings were simultaneously ablated in 150 nm-thick ITO layer on a flexible 100 micrometers thick Polyethylene terephtalate (PET) substrate using scanning with optimized dwell duration of 10 pulses and optimized fluence level of 350 mJ/cm². Lines ablated with mask line groupings of line-width greater than or equal to 11 micrometers showed complete electrical isolation indicating complete ITO removal. Scanning electron Microscopy (SEM) showed the presence of a slight curling effect at ablated line edges. The effect was studied as a function of wavelength and imaging resolution. A CO₂ cleaning method was evaluated for removing the extruding curled material.

The pyrolysis of polysilazanes by laser power represents an innovative technique for the generation of ceramic-like coatings and structures. The dissolved polysilazanes can be easily applied by painting techniques such as dipping or spraying. In the following pyrolysis the polysilazane layer transforms into an amorphous ceramic-like coating. The laser power is absorbed in the precursor layer, which leads to the latter's ceramization without damaging the substrate by thermal load. While plane laser pyrolysis creates a protective coating, selective pyrolysis creates a raised and adherent ceramic-like structure that remains after the unexposed polymer layer has been removed. The flexibility of a writing laser system in conjunction with a suitable handling system makes it possible to inscribe any kind of 2D structure on nearly any complexly shaped part. Some of the chemical, magnetic, and electrical structure properties can be adjusted by the pyrolysis parameters and special types of filler particles. Especially the possibility to control electric conductivity should make it possible to create structure dielectric films or planar resistors, inductors or capacitors, which are basically written on the surface of the part. Because of their ceramic nature of the structures are resistant against high temperatures and corrosive media. Thus, this new additive structuring technique could finally strike a new path in creating corrosion resistant high- temperature sensors and control systems.

Carbonous nano-particles basically consisting of PPN, one of the low dimensional conducting polymers, are prepared on substrates at various temperatures by excimer laser ablation of 3, 4, 9, 10-perylenetetracarboxylic dianydride using a 308nm pulsed excimer laser beam. Particles deposited on the substrates are applied to anode electrodes for ultra thin rechargeable Li ion batteries. Substrate temperature dependence of effective capacitance of lithium ions at first cycle are investigated. In addition, in-situ Raman spectroscopy of the particles under lithium ion doping and undoping is performed to elucidate the storage mechanisms of lithium ion at cis-polyacetylene-type edge of PPN structure. Reversible change of the spectrum in the region related C-H bending of PPN structure in lithium doping and undoping process supports a lithium insertion mechanism proposed by Zheng et al where lithium atoms bind on the hydrogene- terminated edged of hexagonal carbon fragments.

Pulsed laser deposition (PLD) in background gases is a promising method of preparing multicomponent functional thin films, because interactions between the ablated species and the background gases promote not only physical collisions but also chemical reactions, and affect the characteristics of the deposited films. The properties of indium oxide (In₂O₃) thin films prepared by PLD in background gases were characterized in relation to the background gas pressures. Transparent crystalline In₂O₃ thin films could be obtained at background gas pressures above 1.0 Torr on unheated glass substrates. This result can be accounted for by the background gas effects. The stoichiometric In₂O₃ nuclei should be formed in the nonequilibrium high-pressure and high-temperature region generated by the shock front excited by the pulsed laser. Microstructures of the deposited thin films were also investigated using a cross-sectional transmission electron microscope. Initially, amorphous-like layers with a thickness of about 50 nm were formed on the substrates. Subsequently, strongly textured crystalline columns grew on the amorphous-like layers. We discuss the mechanism of thin film growth in PLD.

The German federal government started the funding of a national project intended to exploit the potential of femtosecond technology. In a forgoing competition five research consortia had been successful and have started now together with an adjoin research consortium their investigations in the following fields: (i) micro-machining of technical materials for microstructuring and drilling, (ii) medical therapy in: ophthalmology, dentistry, neurology and ear surgery, (iii) metrology, (iv) laser safety, (v) x- ray generation. Lasers, systems and technologies required in these potential fields of applications will be investigated. The program aims at industrial success and is dominated by industrial partners, therefore. The more fundamental research is done in university institutes and research centers.

Laser ablation of nitrogen solid film deposited on a copper plate at 10 K was investigated by the irradiation of a picosecond UV laser at 263 nm in vacuum. Photo-dissociation of nitrogen molecule in the solid film was confirmed by the optical emissions, which were ascribed to atomic nitrogen, during the laser irradiation at the fluence of 5 J cm^-2 pulse^-1. This photolysis was discussed by the comparison with laser-induced breakdown of nitrogen gas. At the fluence over ca. 10 J cm^-2 pulse^-1, the ablation of the frozen nitrogen film was observed. Employing the ablation plume including a reactive species such as nitrogen atoms, the surface reaction of a graphite oriented pyrolytic graphite plate and silicon wafer was studied. XPS analysis indicated that nitrides were formed on the surfaces by the treatment. The ps-laser ablation of nitrogen solid film provides a novel technique for surface modification of materials.

Holes drilled in Aluminum using nanosecond and femtosecond laser pluses are characterized by Transmission Electronic Microscopy (TEM). Hence we present a method for quantifying the dimensions of the heat affected zone (HAZ) surrounding micro-holes by analyzing the grain size evolution. Drilled samples investigations are performed after electrolytic thinning down to 100 nm. The experiments require a real time imaging system to shot close to the located thinner zone with an accuracy in the micrometers range. Thin Al samples are drilled both in nanosecond and femtosecond regimes using het same pulses number and the same Ti-Sapphire laser source. The regeneratively amplified ultra-short pulses are utilized at a low fluence regime, while the longer pulses are obtained from the regenerative amplifier without oscillator seeding. The main conclusion is that a 40 micrometers wide HAZ is induced by nanosecond pulses, whereas the femtosecond regime does not produce any TEM observable HAZ. It has to be noticed that the width of the femtosecond HAZ is roughly less than 2 micrometers , which is our observation limit.

We report the observation of 3/2-frequency generation during an Optically-induced failure of silica under femtosecond laser pulse irradiation. The origin of 3/2-frequency generation is due to a two-plasmon decay instability, which occurs at the quarter critical density of free charge carriers. We observed this emission during the optical damaging of glasses by tightly focused femtosecond laser pluses. The pulse duration at the irradiation spot was about 0.35 ps, the energy 25-250 nJ, and the damage was recorded in a single shot event inside the glass. The emission at about 530 nm was only present in the spectra measured during an optical damage by 795 nm irradiation with the pulse energy 9 times and more higher than the threshold. We observed a new phenomenon applicable for microstructuring of glass. The high energy fs pulses were focused by a plano- convex lens on the exit surface of a glass plate. The surface was ablated and the ablation was transferred into a volume of glass by translation of a 'plasma spark'. The length of such a channels can by up to few-cm and with a diameter of tens-of-micrometers. The mechanisms and application of high-fluence fs fabrication in dielectrics is discussed.

We performed ablation studies on multi-layer systems at different wavelength - pulse duration combinations. The multi-layer systems of interest, 150 nm thin indium tin oxide (ITO), 200 thin polyaniline (PANI) on 1 micrometers thick photo resist, and 280 nm PPV/pedot layer-combination on 150 nm thin ITO are optically transparent and used for a variety of industrial applications. One important goal of the study was to determine the possible process window for a complete removal of only the top layer, leaving the remaining layer basically unharmed. The investigations were conducted with the following wavelength - pulse duration combinations: 800 nm and 180 fs, 800 nm and 5 ps, 266 nm and 150 fs, 266 nm and 5 ns, 532 nm and 5 ns. We generated micro dots, lines and areas to determine the damage threshold, the processing quality and the processing speed for the specified application of selective layer removal. The structures were analyzed by means of optical and atomic force microscopy. In some cases, we observed a strong pulse duration dependence in the ablation threshold, an indication for the observed difficulties using laser pulse in the ns range. Comparative studies at different wavelengths demonstrate that laser pulses in the UV are not necessarily always a first choice to achieve a precise removal of the optically transparent top layer.

Recently, the semiconductor substrates for integrated circuits have been required to become as thin as 50 micrometers , because the many electronics devices are strongly demanded to be miniaturized and light-weighted. Machining of such thin substrates with conventional dicing techniques is very difficult. Therefore, we have proposed to process them using femtosecond laser ablation, expecting advantage of efficient etching without undesirable mechanical and thermal damages such as cracking and melting is expected. In this work, we have investigated the influence of the laser conditions such as pulse duration and fluence on the cutting depth and diameter in order to develop a new photo-dicing technique for very thin ICs. Within the range of pulse energy used in the present experiments, the dependence of the pulse duration did not seem to be significant. It was also found that the lower energy of the laser pulses, the smaller and the deeper, i.e., the sharper holes were formed. The typical cutting depth and diameter for 0.20 mJ/pulse and 5 shots were 17 micrometers and 40 micrometers , respectively. These values are very promising for the practical dicing applications.

Using tightly focused femtosecond laser pulses waveguides are fabricated inside glasses and crystalline materials. The guiding and attenuation properties at different wavelengths as well as the micro morphology of the irradiated samples are studied. We demonstrate the fabrication of single- and multi-mode waveguides with damping losses well below 1 dB/cm in fused silica. In crystalline quartz we found that the irradiated area has become amorphous due to the absorption of the laser radiation. In this case waveguiding is observed in a stress-induced region surrounding the irradiated, amorphous area.

When femtosecond laser pulses are tightly focused inside the bulk of transparent materials, the intensity in a focal volume become high enough to produce submicrometer-scale structural modifications. The modifications has been applied to fabricate 3D photonic structures. Tightly-focused femtosecond laser pulses create voids, which are surrounded by densified material. In this paper we show that the shapes of voids can be controlled by the spatial profile of incident laser pulse. We also show that the diffraction intensities due to the fabricated arrays of voids depend on the polarization-states of the readout beam. Finally, we demonstrate that irradiation of femtosecond laser pulses moves a void inside calcium fluoride and silica glass without any mechanical translations of the optical system. In situ observation revealed that a void moves towards incident direction of laser pulses as long as 2 micron.

Fundamental questions arise regarding the possibility and nature of melting and the ensuring mechanism of ablation in femtosecond laser processing of materials. A comprehensive experimental study is presented to address these issues in depth and detail. The mechanisms of ultra-fast laser-induced phase-transformations during the laser interactions with materials have been investigated by time-resolved pump-and- probe imaging in both vacuum and ambient environment. The temporal delay between the pump and probe pulses is set by a precision translation stage up to about 500 ps and then extended to the nanosecond regime by an optical fiber assembly. Ejection of material in the form of nanoparticles is observed at several picoseconds after the main pulse. The ignition of surface-initiated plasma into the ambient air immediately following the pump pulse and the ejection of ablated material in the picosecond and nanosecond time scales have been proven by high-resolution, ultra-fast shadowgraphy. To further dissect the origin and evolution of the ablation process, a double pulse experiment has been implemented, whereby both the pump and probe pulses are split into two components each separated by variable temporal delays. A diffractive optical element is used to fabricate micro-channels in silicon wafers.

Femtosecond laser ablation of borosilicate glass has been studied to machine fluidic micro-channel geometries not possible through traditional micro-lithographic techniques. Utilizing a 1 kHz repetition rate femtosecond laser system and a long-working distance 5x objective lens, groove patterns 10 micrometers wide and as deep as 30 micrometers have been produced. The experiments were performed in air and the samples were cleaned after the ablation with sodium hydroxide dissolved in water to remove the debris. The substrates were mounted on a computer controlled x-y translation stage. The quality of the micro-channels showed dependency on the scanning speed of the sample. The surrounding area of the channels was smooth at scanning rates greater than 400 micrometers /s and smaller than 10 micrometers /s. Whereas, cracks appeared around the channels at scanning rates between 200 to 50 micrometers /s. Surface morphology is studied using optical, electron and atomic force microscopies. For a quantitative evaluation of ablation threshold and ablation rates, single-shot experiments in vacuum were performed. We found that the damage threshold for borosilicate glass is around 1.7 J/cm². With single pulse laser fluence of 30 J/cm², a 600 nm deep crater could be ablated. A ring, high than the surface, appeared around the craters and was most probably created by adiabatic compression of glass due to the high-pressure plasma generated in the early stages of the process.

Theoretical and experimental studies of the surface quality in 157 nm F₂ laser-ablated glasses are reported. Limitations set by statistical fluctuations in the multi- mode beam and by stationary beam non-uniformity are explored together with materials issues such as laser-induced surface cracking. Experimental work on ablating polymethyl methacrylate, used as a low threshold medium for recording of the VUV beam, and soda lime glass are described. Use is made of the probe beam deflection technique to determine ablation thresholds, and a variety of methods adopted for characterizing and assessing the quality of ablated surfaces e.g. scanning-electron microscopy, mechanical and optical interference profiling and atomic force microscopy. Preliminary roughness measurements are compared with theoretical expectations and the implication for glass micromachining with the F₂ laser discussed.

The F₂-laser Nano fabrication Facility at the University of Toronto delivers high-fluence 157-nm radiation at high resolution to micro fabricate high-finesse silica-based optical components. The 7.9-eV photons drive strong material interactions near the band-edge states of fused silica and related glasses that help avoid microcrack formation, a common limitation of longer wavelength laser. The strong interactions provide for small and smooth excisions, offering depth control on a scale of tens of nanometers. A 157-nm beam homogenization system and a 25x Schwarzschild lens provided a uniform on-target fluence of 9 J/cm² in a 0.25 mm by 0.25 mm field. Larger work are was enabled by synchronously driving the projection mask and target motion stages. The 0.4 NA lens supported the formation of high- aspect channel walls and surface-relief features as small as approximately 500 nm. Both mask projection and direct writing technique were employed. The novel aspects of the optical beam delivery system are presented together with results on fabricating micro-channels, cutting optical fiber, fabricating surface relief grating and cylindrical lens. The results demonstrate broad application directions for fabricating telecommunication devices, general optical and photonic components, and biological devices.

Using lasers at different wavelengths, the optical and geometrical properties of waveguides can be affected via photochemical, thermo-chemical and diffusion effects. In this paper we review several of these options and show experimental results. Among others, we report on refractive index modification and buried waveguide formation by UV-VUV laser irradiation and on controlled tapering of channel waveguides by thermal laser treatment.

Novel materials processing by a multiwavelength excitation process using F2 and KrF excimer lasers for highefficiency and high-speed refractive index modification of fused silica is demonstrated. We find that this process is essentially superior to single-wavelength F2 laser processing. The multiwavelength excitation process achieves twice of diffraction efficiency compared with that of single F2 laser irradiation sample at the same number oftotal photons supplied to the sample. This high-efficiency and high-speed modification is realized within ns ofthe delay time ofeach laser beam irradiation. In addition, the refractive index change of the multiwavelength sample was increased by 8.2x 1 Ø3, which is 1 .78 times larger than that of single wavelength F2 laser irradiation sample at same irradiation time. This superiority of the multiwavelength excitation process is attributed to resonance photoionization-like process based on excited state absorption in fused silica.

Buried optical waveguides have been fabricated directly in pure bulk fused silica with a novel high-resolution 157-nm optical processing system. Refractive index changes of > 10^-4 were induced within the small focal volume of large numerical-aperture optics, removing the need for ultrafast laser interactions. Single-mode guiding was inferred from Gaussian-like near-field and far-field intensity distributions of 635-nm guided light. The results demonstrate a useful extension of writing buried 3D refractive index structures inside glasses with nanosecond duration UV lasers.

Modifications and microstructures are generated on the surface and in the volume of silicate glasses using pulsed UV laser radiation of small pulse length. During the interaction of pulsed excimer laser radiation and frequency-trippled Nd:YAG laser radiation with intensities below the removal-threshold of the cerium- and silver-doped multi-component silicate glass absorption centers in the UV are induced. Subsequent thermal treatment and wet chemical etching results in crystallization of the laser-illuminated absorbing region and in the fabrication of microstructures on the surface. Processing of sodalime- and boro-silicate glass with pulsed ArF excimer laser radiation and frequency-doubled Nd:YAG laser radiation with intensities above the removal-threshold leads to microstructures including the generation of microcracks on the surface and in the bulk. The dynamics and the transmission of the expanding plasma and changes in the refractive index of the glass are investigated with speckle photography using the pump and probe method. The determination of plasma emission and crack generation is carried out using high speed and Nomarski photography. Morphological and chemical properties of the debris generated under defined processing gas atmospheres are investigated with REM, white light interferometry, XPS and EPMA. Induced absorption and changes of the crystalline- phase are probed using optical-spectroscopy and XRD as well REM. On the basis of these investigations the processes of the generation of induced absorption centers and crystallization on the one hand and the generation of cracks and debris on the other hand as well as the quality of the produced microstructures is discussed.

Photostructurable glass-ceramic materials have received significant attention due to their utility in aerospace engineering and micro technology. For example, the ability to fabricate structures in glass is important in the design and integration of micro scale electronic, optical and fluidic devices. Direct-write pulsed UV laser processing techniques have been utilized recently to create patterned 3D microstructures in a lithium-aluminosilicate glass. The direct-write microfabrication process involves the formation of an initial latent image in the glass via UV laser radiation. Thermal-induced ceramization is utilized to develop the latent image into a permanent image. Material removal and microstructure fabrication are then accomplished by preferential isotropic etching of the developed regions.

Laser-induced -plasma-assisted ablation for crack-free laser processing of glass substrate is investigated. Different form laser breakdown at high laser fluence, a pulsed green laser is used to achieve the glass processing in air at much lower laser fluence. Laser beam goes though eh substrate first and then irradiates on a solid target behind. For laser fluence above target ablation threshold, plasma generated from target behind. For laser fluence above target ablation threshold, plasma generated from target ablation flies forward at a high speed. At a small target-to- substrate distance, there are strong interactions among laser light, target plasma and glass substrate at its rear side surface. With the target materials deposition on the glass surface or even doping into the glass substrate, light absorption characteristic at the near side surface is modified. The laser processing result is closely related to target-to-substrate distance, laser scanning speed and its repetition rate. Color marking, glass metalization and structuring can be achieved with the fine tune of the laser processing parameters.

Excimer lasers are proven tools to machine 2½-D microstructures with variable lateral dimensions. Therefore developed techniques are limited in the vertical dimension since material is removed along the optical axis perpendicular to the target plane. This paper presents 3D structures produced with such UV-lasers. In contrast to optical set-ups for machining 2½-D structures, this approach tilts the target plane and ablates material underneath the target superficies. The tilting angle adds two major difficulties to laser machining: the distortion of the image on the target and the alteration of the ablation cross section. These two difficulties were studied in experiments with different tilting angles β _L between target plane and optical axis of the laser. The impact of β _L was identified on the achieved geometry of 3D structures. A first theoretical approximation integrates the material reflectance and the target cross-section in order to give an estimation of the influence of further effects within the ablation process. This theoretical analysis is a starting point for producing undercutting structures and can additionally be applied to changeable shaped surfaces. Such compel 3D structures have the potential to be sued in micro- tribology as well as in micro guidance systems and are estimated being an important step in micro-mechanics.

This work demonstrated using pulsed and CW lasers for microscale bending of brittle materials, including glass, ceramic, and silicon. Based on the absorption characteristics of these materials, different types of laser were used for achieving bending. Experimental studies were conducted to find out relations between bending angles and laser operation parameters.

A pulsed UV laser volumetric direct-write patterning technique has been used to fabricate the structural members and key fluidic distribution systems of a miniature 100 gm mass spacecraft called the Co-Orbital Satellite Assistant (COSA). A photostructurable glass ceramic material enables this photo-fabrication process. The COSA is a miniature space vehicle designed to assist its host ship by serving as a maneuverable external viewing platform. Using orbital dynamics simulation software, a minimum (Delta) V solution has been found that allows a COSA vehicle to eject from the host and maneuver into an observation orbit about the host vehicle. The result of the simulant show that a cold gas propulsion system can adequately support the mission given a total fuel volume of 5 cm³. A prototype COSA with dimensions of 50 X 50 X 50 mm has been fabricated and assembled for simulation experiments on an air table. The vehicle is fashioned out of 7 laser patterned wafers, electronics boards and a battery. The patterned wafers include an integrated 2-axis propulsion system, a fuel tank and a propellant distribution system. The electronics portion of the COSA vehicle includes a wireless communication system, 2 microcontrollers for system, 2 microcontrollers for system control and MEMS gyros for relative attitude determination. The COSA vehicle is designed to be mass producible and scalable.

Excimer laser micromachining provides a flexible means for the manufacture and rapid prototyping of miniaturized systems such as Biofactory-on-a-Chip devices. Biofactories are miniaturized diagnostic devices capable of characterizing, manipulating, separating and sorting suspension of particles such as biological cells. Such systems operate by exploiting the electrical properties of microparticles and controlling particle movement in AC non- uniform stationary and moving electric fields. Applications of Biofactory devices are diverse and include, among others, the healthcare, pharmaceutical, chemical processing, environmental monitoring and food diagnostic markets. To achieve such characterization and separation, Biofactory devices employ laboratory-on-a-chip type components such as complex multilayer microelectrode arrays, microfluidic channels, manifold systems and on-chip detection systems. Here we discuss the manufacturing requirements of Biofactory devices and describe the use of different excimer laser micromachined methods both in stand-alone processes and also in conjunction with conventional fabrication processes such as photolithography and thermal molding. Particular attention is given to the production of large area multilayer microelectrode arrays and the manufacture of complex cross-section microfluidic channel systems for use in simple distribution and device interfacing.

New technical approaches in biotechnology call for fast, cost efficient and precise patterning techniques in order to realize first polymeric prototypes in a small-scale production. For this purpose a new promising replication procedure was developed: in the first processing step UV- laser radiation is used for direct precision pattering of chemically stable polymer bulk material such as PSU, PEEK, and PI. In the second processing step thin metallic layers are deposited onto the polymer surface. Finally, in the third processing step these laser generated molds are used for replication of PMMA prototypes via UV-light induced reaction injection molding. The metallic layers on the polymeric surface have to suppress or to avoid an undesired chemical interaction between the polymer surface and the MMA/PMMA resin which is used in photo molding. The deposition of a thin Pt/Au layer system leads to a significant increase of mold inset lifetime form 1-5 up to 20 replication cycles for structures with high aspect ratios. Structures with aspect ratios of larger than 10 can be achieved with a minimal lateral dimension of about 6 micrometers . For this rapid tooling technique the actual impressive technical performances compared to other mold insert fabrication techniques will be presented with respect to the prototyping of microdevices made of PMMA.

Bimetallic thermal resist Bi/In has shown many applications in the areas of microfabrication, photomasks and data storage. Optical modeling shows that this class of thermal resist is wavelength invariant, and Bi/In can perform even better at 13.4 nm than at 248 nm due to the increase of absorption and the reduction of reflection. Images were successfully made on Bi/In films with both proximity and projection exposures with Nd:YAG laser running at 2nd harmonic wavelength. A new kind of developing solution used at room temperature was found to be more effective in descumming than nitric acetic acid solution. Both have the etching selectively of unexposed area to exposed areas > 60:1. Developed Bi/In resists shows good conductivity, which can be used as both a metal plating masking and seeding layer, 2 to 10 micrometers wide CU and Ni lines and squares were successfully plated on the developed Bi/In patterns on glass slides and silicon wafers. Shelf test shows that the properties of Bi/In film do not change after being kept in a humid temperature-lifted environment for 10 days. Large optical transmission changes indicate Bi/In can be used for direct-write photomasks and data storage media. Heat- treatment enhances the OD exposed/unexposed OD change.

This paper outlines investigations into a potentially revolutionary approach to tissue engineering. Tissue is a complex 3D structure that contains many different biomaterials such as cells, proteins, and extracellular matrix molecules that are ordered in a very precise way to serve specific functions. In order to replicate such complex structure, it is necessary to have a tool that could deposit all these materials in an accurate and controlled fashion. Most methods to fabricate living 3D structures involve techniques to engineer biocompatible scaffolding, which is then seeded with living cells to form tissue. This scaffolding gives the tissue needed support, but the resulting tissue inherently has no microscopic cellular structure because cells are injected into the scaffolding where they adhere ta random. Wee have developed a novel technique that actually engineers tissue, not scaffolding, that includes the mesoscopic cellular structure inherent in natural tissues. This approach uses a laser-based rapid prototyping system known as matrix assisted pulsed laser evaporation direct write to construct living tissue cell-by- cell. This manuscript details our efforts to rapidly and reproducibly fabricate comlpex 2D and 3D tissue structures with MAPLE-DW by placing different cells and biomaterials accurately and adherently on the mesoscopic scale.

We employ a novel laser forward transfer process, Matrix Assisted Pulsed Laser Evaporation Direct Write, in combination with UV laser micromachining, to fabricate mesoscale ultracapacitors and micro batteries under ambient temperature and atmospheric conditions. Our laser engineering approach enables the deposition of hydrous ruthenium oxide films with the desired high surface area morphology, without compromising the electrochemical performance of this high specific capacitance material. We compare three different desorption formulations incorporating ethylene glycol, glycerol, or sulfuric acid. The best electrochemical performance is achieved using a mixture of sulfuric acid with RuO₂ 0.5 H₂O electrode material. Our ultracapacitors exhibit the expected linear discharge behavior under a constant current drain, and the electrochemical properties of these cells scale proportionately when combined in parallel and series.

The use of direct-write techniques in the design and manufacture of sensor devices provides a flexible approach for next generation commercial and defense sensor applications. Using a laser forward transfer technique, we have demonstrated the ability to rapidly prototype temperature, biological and chemical sensor devices. This process, known as matrix assissted pulsed laser evaporation direct-write or MAPLE-DW is compatible with a broad class of materials ranging form metals and electronic ceramics to chemoselective polymers and biomaterials. Various types of miniature sensor designs have been fabricated incorporating different materials such as metals, polymers, biomaterials or composites as multilayers or discrete structures on a single substrate. The MAPLE-DW process is computer controlled which allows the sensor design to be easily modified and adapted to any specific application. To illustrate the potential of this technique, a functional chemical sensor system is demonstrated by fabricating all the passive and sensor components by MAPLE-DW on a polyimide substrate. Additional devices fabricated by MAPLE DW including biosensors and temperature sensors and their performance are shown to illustrate the breadth of MAPLE DW and how this technique may influence current and future sensor applications.

A prototype workstation has been developed that allows the fabrication of passive electronic components at low temperatures using a laser direct-write process. The work station combines a variety of laser processing techniques onto a single, integrated platform. These techniques include material deposition, laser micromachining, laser sintering, and laser trimming. One particular process, referred to as 'mill and fill', combines the laser micromachining ability of the tool with 'off-the-shelf' conductor pastes to allow the fabrication of high density metalization at very low temperatures. The present work describes the details of the 'mill and fill' process and shows examples of prototype devices fabricated using this technique.

Failure analysis has come to play a key role in ensuring quality and reliability in semiconductor devices, associated packaging and printed wiring boards. Tools are increasingly available to those investigating high-density integrated circuits at the die level, particularly for edit and repair operations. Until recently however, this capability has been limited by the inherent low-resolution mechanical/manual processes used for destructive analysis on electronics packaging. A laser-based tool has been developed to selectively and locally enable access to traces and layers within packages and provide a way to perform edits to an area of interest.

The material processing of an industrial, short-pulse duration DPPS YAG laser producing peak powers greater than 0.2MW is discussed in this paper. This peak power provides sufficient materials processing capability to meet the micro machining needs in the automotive, semiconductor, micro- electronic, medical and telecommunication industries. All hard and soft materials including: plastics, metals, ceramics, diamond and other crystalline materials are suitable candidates for the processing capability of this laser. Micro level features can be machined in these materials to a depth in excess of 1mm with high quality results. In most applications feature sizes can be achieved that are not possible or economical with existing technologies. The optical beam delivery system requirements, and overall micro-machining set-up are also described. The drilling and cutting versatility down to feature sizes of less than 7 micrometers , as well as, complex shapes are shown. The wavelength, pulse length, and peakpower are described and relate to their effect on recast, micro-cracking and material removal rates. Material removal effects related to progressive penetration into the material will be reviewed. The requirements of this DPSS laser technology to meet the operational requirements for high duty cycle operation in industrial environments is covered along with processing flexibility and lower operating cost.

The use of ceramic cores of high dielectric constant is an essential part of a strategy to miniaturize GPS antennas for mobile telephones. The core reduces the guide wavelength of the conducting structures on the antenna, thereby creating a need for high-resolution imaging to maintain very accurate dimensions. It is for this principal reason that a novel laser imaging technology has been developed using a positive electrophoretic photoresist and UV excimer laser mask imaging to produce the conducting features on the surface of the antenna. Furthermore, a significant process challenge in producing this type of antenna concerns the reproducibility of the right-hand circular polarization performance and the bandwidth over which this can be achieved - which becomes progressively smaller as antenna size is reduce. It is therefore a vital requirement that the antennas have the point to be tuned by a laser trimming process at an automatic RF testing station. A galvanometer controlled Nd:YAG laser spot is used to trim the conductive pattern on the top of the antenna following an RF measurement to characterize the resonant frequencies of the four helical conductors. Results demonstrate the laser imaging and trimming techniques ensure a high-speed method of guaranteeing the antenna performance. The technique is appropriate for other antenna types such as GSM, Bluetooth and Wireless LAN.

The problem of laser pulse interaction with small solid particles in a gas atmosphere when detecting its parameters is a serous one in industrial and environmental applications. Previous investigations have shown the possibility of using the laser induced breakdown method. This method is very sensitive, but for a particle size of less than 0.1 micrometers the damage threshold of the solid target is very close to the breakdown point of pure gas. At breakdown, a small volume of dense hot plasma emits radiation by which the size and material of particles can be detected. We used an analytical model, simulation code and experiments to analyze this radiation and found that the emitted intensity varied with laser, gas and particle parameters. The increased dependence of SSP plasma emission rate on initial particle volume permits this method to be used for measuring small particle size by using emitted line spectrum at the late time stage.

In the present paper, Iodine XeI*, XeCl*, KrCl barrier, glow and capacitive discharge excilamps have been studied. Xe-I₂ or Xe-He-I₂ excilamps emit at iodine monatomic resonance lines in the range of 180-210 nm, and on XeI molecule band. Besides that, by varying pressure and mixture composition, it is possible to control relation between iodine monatomic lines and XeI* molecule band radiation intensity. The efficiency level is up to 12 percent. The lifetime in sealed-off excilamps was more 1000 h. It is shown that at barrier KrCl and XeCl excilamps excitation by short unipolar or bipolar voltage pulse the efficiency is higher than by sine pulses excitation. Output at (lambda) approximately 222 nm up to 100 W and at 308 nm up to 75 W from barrier discharge excilamps was obtained. Presence of filaments occurs to be a necessary condition to obtain high efficiency since in that case a demanded level of excitation specific power is being achieved. Radiation pulse delay relatively to excitation in the conditions of homogeneous discharge probably demonstrates low efficiency of KrCl* and XeCl* molecules formation at a low level of excitation power. Output at (lambda) approximately 222 nm up to 190 W and at 308 nm up to 91 W from glow discharge excilamps was demonstrated.

Silicon dioxide (SiO₂) thin films were deposited at room temperature by 193-nm ArF excimer laser ablation of silicone in oxygen atmosphere. Only the side chains of the target were photo-dissociated during ablation to deposit Si-O bonds on a substrate in high laser fluence at about 10 J/cm². Oxygen gas worked to oxidize the Si-O bonds ejected from the target to from SiO₂ thin films at the gas pressure of 4.4 X 10^-2 Torr, in addition to reducing the isolated carbon mixed into the films. We also found that the deposited rate could control refractive index of the films. The refractive index of the film deposited at 0.05 nm/pulse is greater than that of the film at 0.1 nm/pulse. Thus, a 0.2-micrometers thick SiO₂ cladding film deposited at 0.1 nm/pulse was firstly formed on the whole surface of a 100- micrometers -thick polyester film, and then a 0.6 micrometers -thick SiO₂ core film at 0.05 nm/pulse was fabricated in a line on the sample. The sample functioned as a waveguide device for a 633-nm line of He-Ne laser.

Laser-induced forward transfer (LIFT) was applied to eject m9icro-sized TiO₂ particles on gold thin film on SiO₂ substrate. The behavior of the ejected TiO₂ particles in the gas phase was imaged by light scattering method. The fastest velocity of the particles exceeded 700 m/s. In addition, laser dye film on SiO₂ substrate was transferred by LIFT and deposited on the other SiO₂ substrate, and it emitted fluorescence with excitation by second harmonic wave of YAG laser at 532 nm.

The use of lasers in packaging and materials processing is an increasingly attractive choice for high technology manufacturing. As we push for more demanding materials processing tasks and smaller dimensions, an understanding of the underlying physical and chemical aspects of problems becomes important. Here we discuss some of these issues relevant to materials processing.

In the past two decades, laser applications in the packaging of microelectronics and photonics have clearly made a mark in industrial processing. With the commercial availability of reliable UV and IR lasers, a wealth of techniques and methods have evolved: generation of vias, high resolution patterning of materials by etching and ablation, laser bonding and micro welding, stripping of insulation and cladding, deposition of conductors, creation of surface microstructures, cleaning of sensitive surfaces, and a variety of drilling, slicing, and dicing processes. The list goes on and on, and what new techniques may evolve is limited only by human ingenuity. In this presentation we will review several of these applications with particular emphasis on those that are industrially useful. Many interesting concepts in laser processing fill the pages of scientific and engineering journals, but few of these ideas are seriously considered for a manufacturing environment. In conclusion, we will attempt to answer just what makes an industrially successful laser process.

Diode pumped Nd:YAG lasers are becoming a potentially powerful tool for microelectronics packaging and micro- machining. One of the major advantages of such lasers is high brightness and pulse formatting capability. This offers a tool for controlled materials removal or micro-welding. The recently developed high power diode pumped Nd-YAG laser with Slab geometry opened the door for even higher power density. On the other hand, high brightness poses a challenge for management of laser-induced plasma for process stability and repeatability. In order to develop the fundamental understanding of the role of plasma during the laser micro-machining, one needs to fully characterize the plasma density. Laser absorption spectroscopy is a good tool for that purpose since it measures the events near the ground level where population is high and thus measurements are more accurate. This paper describes the technique and presents the results.

Singulation of packages is an important step in the manufacturing of IC devices. Presently, the most widely used technique is abrasive sawing. Due to the combination of different materials used in packages such as copper and mold compound, the saw rapidly blunts and also conventional laser cutting by a water-jet with the high precision and speed of a laser cut and is now applied into electronic package singulation.

New joining techniques are required for the variety of materials used in the manufacture of microsystems. Lasers are emerging as a useful tool for joining miniaturized devices. The beam can be focused to less than .001 inch allowing localized joining of very small geometries. There is minimal heat input into the part so distortion and change in material properties is minimal. The high quality of the laser welds and the precise process control enable hermetic sealing.

Micro structures in silicon are applied in different fields of industry, medicine and research. Examples are micro mechanical sensors for car security systems, nozzle plates for printer, and optical elements for x-ray beam splitting. Wherever the accuracy of etched silicon structures is not required, laser processes with short pulses and small wave length can be an option with the advantage of shorter process time. In this contribution the possibilities and limits of laser machining of Si by diode pumped Nd:YAG lasers with harmonics generation will be presented by means of structures processed by application of a scanner with f- theta-optic. The result will be discussed concerning the experimental setup and the laser parameters.

Laser welding of polymers using high power diode lasers offers specific process advantages over conventional technologies, such as short process times while providing optically and qualitatively valuable weld seams, contactless yielding of the joining energy, absence of process induced vibrations, imposing minimal thermal stress and avoiding particle generation. Furthermore, this method exhibits high integration capabilities and automatization potential. Moreover, because of the current favorable cost development within the high power diode laser market laser welding of polymers has become more and more an industrially accepted joining method. This novel technology permits both, reliable high quality joining of mechanically and electronically highly sensitive micro components and hermetic sealing of macro components. There are different welding strategies available, which are adaptable to the current application. Within the frame of this discourse scientific and also application oriented result concerning laser transmission welding of polymers using preferably diode lasers are presented. Besides the sue laser system the fundamental process strategies as well as decisive process parameters are illustrated. The importance of optical, thermal and mechanical properties is discussed. Applications at real technical components will be presented, demonstrating the industrial implementation capability and the advantages of a novel technology.

This paper presents results on machine and process development for laser welding of surface mounted devices on thermal resistant polymer based molded interconnect devices with copper layers of 35 micrometers and 70 micrometers thickness. Characteristics, advantages and problems of this technology are shown and possibilities to achieve reproducible results are discussed. The investigations are carried out with pulsed Nd:YAG-lasers wit a maximum average power of 300 W. Additionally, a process control concept evaluating the reflected process radiation is discussed.

This paper deals with a development of laser welding of colored plastics. Welding of thermoplastics using near-IR lasers has been seen in wide industrial application. Most of thermoplastics are transparent to near-IR laser. Particular characteristic of near-IR laser radiation has the ability to heat the interface between the transparent part and absorbent one colored with pigments. However, it is difficult to weld a pair of transparent materials by a laser beam, since there is no absorption region within them. In this paper, the influence of near-IR transparent plastics on the yield strength of their weldments has been studied: various colored plastics transparent to diode laser radiation were tested as the welding material. The heat transfer within a welding system was also analyzed and assessed the appropriate absorptivity and transmittance of overlapping colored plastic.

A system has been built for the fast control of the laser welding process in conduction regime. Based on a traditional Proportional Integral Derivative analysis, the system can regulate millisecond laser pulse. Besides, the interaction in this regime has been monitored with different diagnostics. Visible signal above target, IR signal from surface and visualization from CCM camera have been correlated as function of laser power density to distinguish the different phases of interaction. With this experimental set up, the detector used for control process could be calibrated. The integration of the system is shown for watch parts assembly.

The new welding technique 'SHADOW ' is introduced. SHADOW means the use of a single pulse to generate a quasi continuous weld of several millimeters in length. HET processing time is defined by the pulse duration of the pulsed laser. At present, a state-of-the-art laser is capable of a maximum pulse duration of 20 ms. The variation of the laser power depend on time is a vital capability of the pulsed laser to adapt the energy deposition into the workpiece. Laser beam welds of several watch components were successfully performed. Similar metals like crowns and axes made out of stainless steel have been welded using pulsed laser radiation. Applying a series of about 130 single pulses for the crown-axis combination the total energy accumulates to 19.5 J. The use of the SHADOW welding technique reduces the energy to 2.5 J. While welding dissimilar metals like stainless steel and bras, the SHADOW welding reduces drastically the contamination as well as the distortion. Laser beam welding of copper has a low process reliability due to the high reflection and the high thermal conductivity. SHADOW welds of 3.6 mm length were performed on 250 micrometers thick copper plates with very high reproducibility. As a result, a pilot plant for laser beam welding of copper plates has been set up. The work to be presented has partly been funded by the European Commission in a project under the contract BRPR-CT-0634.

This paper presents an overview and future prospects of the use of lasers for packaging by the microelectronics and photonics industry in Japan. Various kinds of lasers and material processing technologies have been developed and applied for manufacturing electronic and photonic devices to meet the strong demands for high-performance, lightweight, low energy-consumption mobile digital consumer electronics, broadband optical fiber communications, low-emission and fuel-efficient, easy-to-steer smart cars, etc. This paper emphasizes solid-state lasers as convenient and versatile light sources for packaging advanced compact devices with sensitive passive or active components having small feature sizes. Some of the representative material processing applications using solid-state lasers for electronic and photonic devices are, opaque and clear defects repairing of LCDs, trimming of functional modules, fine-tuning of optical characteristics of photonic devices, forming of various micro-vias for high-density interconnection circuits, laser patterning of amorphous solar-cells, and high-precision laser welding of electronic components such as optical modules, miniature relays and lithium ion batteries. The recent progress in high-power ultra-short pulse solid-state lasers seems to be rapidly increasing their processing capabilities such as for fine adjustment of optical filters, etc.

After the invention of the laser principle and its first application for drilling of jewels in watch movements, the laser was only used for marking. The still ongoing trend of miniaturization and automation opened a new field of application: laser beam micro welding. This paper gives an overview of the new application of laser beam welding in watch industry. The combination of dissimilar materials like brass and stainless steel is often needed in watch movements due to tribologic aspects. Here, laser beam micro welding offers an alternative to conventional joining techniques like press fit or gluing. Since the watch components are very small the locally limited heat input of the laser beam offers the possibility of weld seam widths < 200 micrometers . The depth and the width of the closed weld seam as well as the surface quality can be influenced especially at the end of the seam using the pulse forming capability of a pulsed Nd:YAG laser. Several watch components could be joined by means of laser beam micro welding. The width of the seam could be reduced to 100-200 micrometers . The joining geometries of an axis/wheel combination are in the range of 100 micrometers to 1 mm diameter of the axis and about 200 micrometers wheel thickness. The process of laser beam micro welding could be integrated in a fully automated assembly machine for watch movement parts. This paper will give an overview about some results of a European research project where the welding of microparts was investigated. The aim was to decrease contamination and distortion of the parts during the mending process. The work to be presented has been funded by the European Commission in a project under the contract BRPR-CT- 0634.

Laser processing has large potential in the packaging of integrated circuits (IC). It can be used in many applications such as laser cleaning of IC mold tools, laser deflash to remove mold flash form heat sinks and lead wires of IC packages, laser singulation of BGA and CSP, laser reflow of solder ball on GBA, laser marking on packages and on SI wafers. During the implementation of all these applications, laser parameters, material issues, throughput, yield, reliability and monitoring techniques have to b taken into account. Monitoring of laser-induced plasma and laser induced acoustic wave has been used to understand and to control the processes involved in these applications.

Pulsed laser ablation of mold compounds for IC packaging in air and with steam assistance is investigated. It is applied to decap IC packages and expose computer CPU dies for the device failure analyses. Compared with chemical decapping, the laser ablation has advantages of being fast speed, non- contact and dry processing. Laser ablation with the steam assistance results in higher ablation rate and wider ablated crater with much smoother surface morphology. It implies that the steam assisted laser ablation can achieve a faster and better quality laser processing. Audible acoustic wave and plasma optical signal diagnostics are also carried out to have a better understanding of the mechanisms behind. Light wavelength and laser fluence applied in the decapping are two important parameters. The 532 nm Nd:YAG laser decapping at a low laser fluence can achieve a large decapping area with a fine ablation profile. IC packages decapped by the laser ablation show good quality for the device failure analyses.

A novel method for laser welding for sheet metal. is presented. This laser spike welding method is capable of bridging large gaps between sheet metal plates. Novel constructions can be designed and manufactured. Examples are light weight metal epoxy multi-layers and constructions having additional strength with respect to rigidity and impact resistance. Its capability to bridge large gaps allows higher dimensional tolerances in production. The required laser systems are commercially available and are easily implemented in existing production lines. The lasers are highly reliable, the resulting spike welds are quickly realized and the cost price per weld is very low.

This paper discusses possible potentials of ultra short laser pules in the pulse width range < 10 picosecond from the perspective of laser micro processing. With the problems involved generating ultra short laser pluses at high average power it will be shown, that the most successful applications performed with ultra short pulse technology is associated with problems, where the precise energy localization plays a crucial role. The discussion is based on laser processing examples from the application laboratory at the LMTB GmbH comparing applications using q-switch Nd:YAG lasers with nanosecond pulse widths and mode-locked, amplified Ti:sapphire lasers.