One of the early applications of lasers was marking electronics components. Today laser marking has found its way into a wide range of applications, from wafer marking at the chip scale package level to beer bottles and food package identifications, and to marking of the cloth buttons. In many cases, laser marking has become a standard manufacturing process. We will review the laser marking technology over the last four decades. This would include the review on evolution of the different laser technologies and beam delivery systems used in various laser-marking systems for the past 40 years. Finally, the latest laser marking technologies will be presented and future directions be discussed.

A necessary step in the fabrication of many different flat panel display types is the selective removal of a thin layer of indium tin oxide (ITO) or other transparent conductor from the substrate to create circuit patterns. The conventional method of performing this patterning utilizes photolithography. Specifically, an image of the desired pattern is projected on to a photoresist coated substrate, and this substrate is then developed and etched with wet chemicals. However, it is possible to use a laser to directly ablate ITO without damaging the substrate, and thus eliminate all the expense, time and environmental concerns associated with a multi-step wet chemical process. First generation laser based systems for ITO patterning were too slow to be competitive with traditional means, however, laser manufacturers are focused on developing sources that enable the required process speed, and also possess desirable characteristics in terms of lifetime, maintenance downtime, and overall cost-of ownership. This paper examines the requirements for an optimum laser source to service this emerging laser application.

Many materials e.g. diamond or silicon do not show sufficient absorption at one micron, the fundamental wavelength of Nd-based solid-state laser sources. Frequency conversion to the second and fourth harmonic allows the efficient processing of these materials. High beam quality is another important property for micro material processing with lasers. It facilitates small focus diameters and due to high Rayleigh length even at strong focusing drilling of holes with high aspect ratio. Together with high average output powers it allows fast processes with high quality. At least flexible pulse peak power and repetition rate is necessary to optimize the process. Two laser systems which fulfill these requirements are investigated. A pulse pumped Nd:YAP system which delivers an average output power of 124 W at the second harmonic and a Nd:YAG with an average output power up to 50 W in the second harmonic. Due to its active Q-switch the pulse peak power of this system is variable in a wide range. Efficient laser processing of different ceramics with these laser system are presented.

Laser milling of industrial materials like ceramics, dielectrics and metals is of significant commercial interest for microfabrication of micro-moulds and other micro-system devices. 2.5D laser machined structures were generated in alumina, tungsten and steel substrates using a nanosecond copper vapour laser (511nm) at 10 kHz. Preliminary results in fused silica, alumina and steel are also presented from a high repetition rate amplified mode-locked picosecond Nd:vanadate laser. It is shown that high quality surface finish can be achieved with both laser types; for example, average surface roughness, Ra ~ 300nm has been demonstrated in steel. Fused silica could only be processed with picosecond laser pulses. Volume removal rates are analysed, which are especially high for difficult materials like tungsten (~0.1mm³/min) and are greater compared to other milling technology like micro-EDM. Surface roughness measurements in these materials using white light interferometry are reported along with SEM analysis.

Producing micron level exit holes or vias interconnects for applications involving critical drug delivery and microelectronic packaging is no easy task. The design of excimer beam delivery optics, the physical system configuration, construction materials used and laser material interaction play significant roles in the ultimate process results. As a result of higher density microelectronic package designs and the critical nature of drug delivery, these processes need to be robust and repeatable to a 3σ level. Many companies who look to source new laser systems to meet these new demands come face to face with the reality of this dilemma. Matching laser process to material selection sets the stage for a successful integration, of most concern is the materials ability to resolve the features desired and the ease of cleaning the debris once the features are formed. This paper will present application specific laser beam delivery methods, focus/image stability techniques, beam shaping and inline inspection technology to stabilize such processes and present statistical and quality data on a process that was developed to form (1) one micron exit holes through 25 micron thick polyimide for a critical drug delivery application. The data will cover a 31 day period of processing.

Today's excimer lasers are well-established UV laser sources for a wide variety of micromachining applications. The excimer's high pulse energy and average power at short UV wavelengths make them ideal for ablation of various materials, e. g., polyimide, PMMA, copper, and diamond. Excimer micromachining technology, driven by the ever-shrinking feature sizes of micro-mechanical and micro-electronic devices, is used for making semiconductor packaging microvias, ink jet nozzle arrays, and medical devices. High-power excimer laser systems are capable of processing large areas with resolution down to several microns without using wet chemical processes. For instance, drilling precise tapered holes and reel-to-reel manufacturing of disposable sensors have proven to be very cost-effective manufacturing techniques for volume production. Specifically, the new industrial excimer laser-the LAMBDA SX 315C-easily meets the high demands of cost-effective production. The stabilized output power of 315 watts at 300 Hz (308 nm) and its outstanding long-term stability make this laser ideal for high-duty-cycle, high-throughput micromachining. In this paper, high-power excimer laser technology, products, applications, and beam delivery systems will be discussed.

Excimer laser ablation is used for microvia formation in the microelectronics packaging industry. With continuing advancement of laser systems, there is an increasing need to offset capital equipment investment and lower equipment downtime. This paper presents a neuro-fuzzy methodology for in-line failure detection and diagnosis of the excimer laser ablation process. Response data originating directly from laser tool sensors and the characterization of microvias were used as failure symptoms for potential deviations in four laser system parameters from their corresponding baseline values. The response characteristics consist of via diameter, via wall angle, and via resistance. Resistance measurements on copper deposited in the ablated vias were performed to characterize the degree to which debris remaining inside the vias affected quality. The laser system parameters include laser fluence, shot frequency, number of pulses, and helium pressure flow. The adaptive neuro-fuzzy inference system (ANFIS) was trained and subsequently validated for its capability in evidential reasoning using the data collected. Results indicated only a single false alarm occurred in 19 possible failure detection scenarios. In failure diagnosis, a single false alarm and a single missed alarm occurred.

Semiconductor manufacturing, is dominated by the relentless demand for electronic products with greater performance, minimized dimensions, increased sophistication, and higher speed, all at reduced process cost. Logic device manufacturers need to satisfy this demand by producing integrated circuits that meet the predicted density increase encapsulated in Moore's law. This has led to the use of low-κ dielectrics. For memory devices, thinner wafers are used to enable close stacking of multiple dies in a single low-profile package. And in a third market segment, newer photonic devices are using novel materials such as GaAs, SiC, GaN and sapphire. Traditional mechanical methods are struggling to meet the singulation needs in all three of these device types. Yet at the same time, market realities dictate that the effective cost for increased processing power, novel photonic performance, and higher memory density all continue to fall. As a result, laser-based methods are being adopted in all three areas. In this overview paper, we examine the drivers for each of these market segments and see how laser technology is meeting the singulation demands of current and future devices.

Dry and steam laser cleaning, DLC and SLC, of nano-and micro contaminant particles from UV/vis opaque and transparent critical substrates has been studied in front-side laser illumination geometry with the help of time-resolved optical techniques using a nanosecond IR CO2-laser and different energy transfer media (ETM) fluids. In the case of SLC, microscopic details of particle-ETM-substrate interactions in pre-deposited micron-thick ETM layers have been revealed preliminarily by means of time-resolved optical microscopy. Fundamental DLC and SLC mechanisms for removal of nano- and micro-particles from opaque and transparent critical substrates have been determined. Optimal conditions for nearly complete laser cleaning have been chosen for different combinations of contaminating nano- and micro-particles and substrates.

Laser annealing has become the primary method for producing the Low-Temperature-Poly-Silicon (LTPS) panels used in the Flat Panel Display (FPD) industry. Thin Film Transistor (TFT) backplanes based on LTPS substrates for Active Matrix Liquid Crystal Displays (AMLCD) offer substantial advantages over TFT backplanes based on amorphous silicon. The trend to higher pixel density, the integration of more driver and logic ICs on the glass, and the advent of Active Matrix Organic Light Emitting Displays (AMOLED) all have lead to significant interest in the laser annealing process. Currently, there are several different approaches to the annealing process based on excimer lasers, cw-green DPSS lasers, modelocked-green DPSS lasers and Q-switched Nd:YAG lasers. This paper reviews the various laser technologies and annealing techniques, such as the line beam method and Sequential-Lateral-Solidification (SLS). These approaches will be compared in terms of crystal quality, electron mobility, throughput, yield and operating cost.

We have previously shown that location-controlled single-crystal regions can be obtained by implementing a version of the sequential lateral solidification process referred to as dot-SLS. Performed on an amorphous Si precursor, however, the process results in regions having an apparently random surface crystal-orientation distribution that may negatively impact the uniformity of resulting devices. In this paper, we demonstrate one approach to control the surface orientation of dot-SLS processed regions. We accomplish this in a simple manner by performing the process on textured polycrystalline Si precursor films that were, in turn, obtained using laser processing of as-deposited amorphous Si films. This hybrid approach is possible and effective because the dot-SLS process allows for preserving the original texture of the "seed" crystals, while successfully removing all random high-angle grain boundaries within the laterally solidified regions. We identify and utilize two specific and well-known laser-processing techniques for obtaining highly (100) or (111) surface textured polycrystalline Si films. The results from dot-SLS experiments performed on (100) textured films- obtained through "mixed-phase" zone-melting recrystallization using a continuous-wave laser - were found to be particularly significant as the growth from {100} surface-oriented seeds resulted in single-crystal regions that were predominantly free of any planar defects.

Excimer lasers are unique ultraviolet laser sources ideally suited for a wide range of applications driving innovations in almost every branch of industry including microsystem manufacturing, flat panel display production and dense wavelength division and multiplexing to name a few. The success of fiber Bragg gratings in the last years is based on their unique properties which make them extremely valuable for numerous applications in optical telecommunication networks. Expectations for the continued growth of demand for internet services and more bandwidth show a promising future also for passive optical components. Components which serve not only one but several purposes have a good possibility to participate in this success proportionally. Excimer laser written fiber Bragg gratings (FBGs) stabilize the frequency of laser diodes, flatten the non-linear gain of fiber amplifiers, compensate for the fiber's dispersion and filter communication channels. Developments and optimization of 248 nm excimer laser systems for mass production environments are ongoing.

The low temperature fabrication of passive electrical components (conductor, capacitor) on the flexible polymer substrate is presented in this paper. A drop-on-demand (DOD) ink-jetting system was used to print gold nano-particles suspended in Alpha-Terpineol solvent and PVP in PGMEA solvent to fabricate passive electrical components on flexible polymer substrate. Short pulsed laser ablation enabled finer electrical components to overcome limitation of inkjet process. Continuous Argon ion laser was irradiated locally to evaporate carrier solvent as well as to sinter gold nano-particles. In addition, a self alignment technique for PVP layer was demonstrated taking advantage of the deliberate modification of surface wetting characteristics. Finally, a new selective ablation of multilayered gold nanoparticle film was demonstrated using the ablation threshold difference for sintered and non sintered gold nanoparticles.

Previous research showed that bimetallic Bi/In and Sn/In films exhibit good grayscale levels after laser exposure due to controlled film oxidation. While giving a large alteration in optical density (OD) from 3.0OD to 0.22OD at 365 nm, Bi/In and Sn/In films show a very nonlinear OD change with laser power, making fine control of grayscale writing difficult at some gray levels. This paper studies Zn and Zn alloy films as possible candidates for improved direct-write grayscale photomask applications. Zn and Zn alloys laser oxidation have been reported previously, but without grayscale optical measurements and applications. In this paper Zn films (50 nm ~ 240 nm), Sn/Zn (100 nm), Al/Zn (100 nm), Bi/Zn (100 nm) and In/Zn (100 nm) were DC- and RF-sputtered onto glass slides and then were scanned by argon ion CW laser (488 nm). Among these films, the highest OD change, 3OD (from 3.2OD before exposure to 0.2OD after laser exposure) at 365 nm, was found in the In/Zn (25/75 nm or 84at% Zn) film. The characterization of grayscale level to laser power modulation in Zn and Zn alloy films with various thickness or composition ratios were investigated. The Zn OD change versus laser power curve is more linear than those of Sn/In and Bi/In films. In/Zn films have better characterization of grayscale level versus laser writing power than pure Zn film. Among these four Zn alloy films, Zn/Al shows most linear relation of OD at 365 nm to laser power modulation.

DC-sputtered Sn/In and Bi/In bimetallic thin films oxidize and turn transparent under laser exposure. The film's transparency, or optical density (OD), changes smoothly with increasing laser power, from ~3.0OD (unexposed) to <0.22OD (fully exposed). Laser-induced oxidation of bimetallic films can be used to produce direct-write binary and analogue grayscale photomasks. In order to create high quality grayscale photomask and to improve our current laser writing process, requires real time measurement of OD values, and a greater understanding of the laser-induced oxidation process of the bimetallic thin films. An OD measurement system has been developed capable of providing real time optical density and exposure power changes for the bimetallic thin films. Three silicon-based PIN photodiodes were used to monitor the incident and transmitted beams powers, allowing us to measure the OD change as the film oxidizes, giving us a real time measure of the optical density changes of the bimetallic thin film. With this OD measurement system, real time OD data can be used to adjust the laser power to compensate any variations in laser output power, film characteristics and other variations in the laser writing system. Furthermore, with the incident beam focused, we can precisely measure OD level in areas as small as the laser spot size. Exposed Bi/In/O films show an immediate rapid -2OD/ms change in the first 0.5 ms of exposure. However, In/Sn and Zn films show an initial time delay before OD begins to change, and then a less rapid change of -0.56OD/ms or -0.32OD/ms respectively.

Tight focusing of ultrashort near infrared laser pulses in the bulk of various transparent materials induces significant modifications of the optical properties by locally changing the material refractive index. Such laser-induced phase objects are of major technological interest, notably for direct writing of embedded optical functions. While extensive studies have been reported on ultrashort pulsed laser induced modifications in several materials, especially with regard to focusing conditions, incubation effects, or the influence of the energy content of the pulse, we emphasize here the role of the temporal design of the excitation sequence. We present phase-contrast microscopy investigations of the resultant morphology and discuss the refractive index topological map induced by different temporal pulse intensity envelopes in various transparent materials. The consequences of temporal profiles generated by a pulse shaping apparatus on the morphology of the interaction zone are illustrated, emphasizing the benefits of the synchronization between the excitation temporal profile and the material response.

Due to a large material removal rate and a minimal collateral damage, subpicosecond laser pulse offers many advantages for material processing. Post-experimental examination of ultrashort laser material ablation shows that the heated surface of the bulk does not exhibit thermal damage. A lot of complicated physical processes follow intense laser irradiation and have often been modeled in over-simplified way to explain experimental results. Because a more complete understanding of the damage mechanisms would be very interesting and would open new applications in the scientific research community and industry. A detailed model of the ultrashort response to reproduce ablation process is presented, describing dynamical electronic properties such as temperature, pressure and energy. To simulate the interaction between the laser and the metallic target, these theoretical models are inserted inside a 1D Lagrangian hydrodynamic code. It is still a very challenging task to disentangle the cumulative/competitive effects of all physical processes if included at once in numerical simulations. Adding the different processes into numerical simulations on a one by one basis allow to assess their contributions to the quantity of ejected matter on a large range of laser intensity. Experimental results related to the influence of multi-pulses or tailored pulses for ablation efficiency with ultrafast pulses(pulse duration up to 5 ps) has been obtained. A significant improvement of the micro structuring quality in metals is demonstrated, and the theoretical approach presented allow to manage the optimal temporal shape of pulses. An efficient process control can be reached and the industrial applications will be evidenced.

New nanomaterials such as nanobump, nanomesh, nanobelt were generated by thin film processing by interfering femtosecond laser beams. To split and correlate femtosecond laser, a demagnification optical system with a transmission beam splitter was used. Different interference patterns can be generated depending upon the number of beam, magnification factor and period of the transmission grating. Using the system, a material surface can be processed according to the interference pattern. Metallic single- or multi-layered film was used as a target. A nanobump array was applied to field emission device. In addition, periodic structure could be generated inside transparent material in a single process. This scheme is a new technique to generate new nanomaterials and nanostructures using top-down technique.

Multi-beam laser interference (MLI) lithography is known to be one of the fabrication techniques of photonic crystals. In MLI lithography, laser beams are interfered on a scale of the wavelength of light and are irradiated to photosensitive films. We have paid attention to photosensitive TiO2-organic hybrid film, which has high refractive index. TiO2-organic hybrid periodic pillar patterns were fabricated by MLI lithography. The TiO2 hybrid film, which was prepared from Ti-alkoxide and β-diketone by the sol-gel method, was exposed to the interference pattern of femtosecond pulses at 800 nm wavelength. After laser irradiation, the unirradated portion was removed by the development and rinse. Two-dimensional periodic standing alone pillars and 2×2 and 3×3 top-gathering pillars, which were gathered at the top by means of self-organization were formed by changing conditions such as laser irradiation time and film thickness. The pillar patterns depended upon the rinse liquid, the diameter, and the height of pillars. The top-gathering pillars are applicable for diffractive optics.

Interaction between an intense laser pulse and a material is a key issue to understand and control photo-induced processes. It is, however, rather difficult to study the interaction in detail because it occurs in a very narrow area and a very short period. In addition, it is usually accompanied by plasma formation, which causes difficulties for the most of observation and measurement techniques. We have developed a time-resolved imaging technique which uses a pulse laser as a probe light and an ICCD camera as a recording devise, and successfully observed the dynamical change of the spatial distribution of laser induced transient stress fields by both shadowgraph and photoelasticity images using transparent materials. Recently, we have found that photoelasticity imaging of epoxy-resin observed under water provide clear images which allow us the semi-quantitative estimation of the magnitude of laser induced stress. We can make the semi-quantitative estimation of the laser-induced stress by comparing images to those obtained for designated pulse energies. Effect of surface roughness is examined. The effect of the confinement of laser ablation by water is shown semi-quantitatively. The interaction of laser to the metal surfaces is examined by using epoxy samples the surfaces of which are coated by several metals. Transient stress induced in inside of the bulk materials by focusing the laser at inside of transparent materials are dynamically observed and compared with permanent damages induced by the laser irradiation.

Due to hyperthermal particle energies, extremely high pulse deposition, and quenching rates the pulsed laser deposition (PLD) lies apart from all the other known deposition methods. The paper reviews the peculiarities of the cross-beam PLD (CBPLD), one of the most effective variant of high vacuum PLD with colliding ablation plumes. In addition to the reliable reduction of any form of macroparticle contamination it allows the fabrication of films with unexpected crystalline structure and unique physical properties, making the CBPLD a unique hyperthermal energy deposition technique.

We are proposing a method and system to mount and treat the surface of a fabricated micro-component to improve its tribological performance. By irradiating an infrared laser under ambient conditions, the heat will penetrate the micro-component's surface, causing it to melt and flow to reduce the amount of irregularity. This method can create a desired surface finishing with good repeatability on selected regions of the micro-components. It can also work on surfaces of various material types as well as internal surfaces of thin planar or circular structure. By changing the laser power, the repetition rate and the scanning speed, the process can deal with surfaces of different roughness. The final surface roughness can be improved from micro-meter level to sub-100nm level. The laser treated micro-components have improved tribological performance as the friction is reduced; the abrasion, heat and noise are also reduced. The improvement can enhance the lifetime of the micro-component when used in micro rotating or sliding mechanism.

We describe modification of various glasses by a CW Laser Backside Irradiation (CW-LBI) method. In this method, an absorbent which was attached on one side of a glass sheet, was irradiated from the other side through the glass with CW laser beam. Ar ion laser was used and copper foil was chosen as an absorbent. Silica, Pyrex and soda-lime glasses were tested as sample glasses. When the absorbent was irradiated, heated spot appeared in the glass adjacent to the absorbent and it ran to the other side of the glass in the path of laser beam. Then cylindrical modified zone that was transparent and crack-free was produced. Diameter of the modified column was 30~100 μm and the cylinder could grow up to 30 mm. The growth rate was approximately 200 mm/s. The dimension of modified zone depended on irradiation conditions, such as laser fluence or beam profiles. The threshold fluences for modification of the glasses were 1~2.5 × 105 W/cm2. Then the characteristics of modified zone were examined by etching in 5 wt. % HF solution. As a result, it turned out that modified zone consisted of two layers and etching rate of the inner part was lower than that of the outer part. The Raman spectroscopy revealed that the density of the inner part increased by the modification.

Various micro/nanoscale materials and devices are being developed for applications in biology, materials, electronics, chemistry, and physics. Areas such as micro/nanocomposites, molecular electronics, molecular motors, self-assembled nanoenergetics, and nanobiology are just a few examples. A major obstacle to making progress on the micro/nanoscale is the lack of powerful fabrication and diagnostic techniques that work effectively to make the structures and to determine the morphology, chemical composition, and electronic/optical properties. In particular, there is a lack of techniques to diagnose individual nanostructures to find their geometries, electronic properties, optical properties, and chemical compositions in a correlated manner. Laser material processing and characterization is traditionally used in microscale applications due to the diffraction limit of light. In order to apply laser-based techniques in nanotechnology, we have to develop methods which can overcome the optical diffraction limit. In this paper, we will review a few techniques developed in recent years, including laser-assisted scanning probe microscope, superfocusing by optical resonance in spherical particles, laser nanoimprinting, laser synthesis of quantum dots, laser annealing of ultrashow pn junctions, nanometer-order film thickness detection using rotational Raman spectroscopy, laser cleaning of nanoparticles, near-field-controlled material deposition, laser-assisted growth of carbon nanotubes, and laser synthesis of one-dimensional carbon structures.

Rapid progress in ultrafast laser systems opened many exciting possibilities for high-resolution material processing. These laser systems allow to control and deliver optical energy and laser pulses in time and space with unprecedented precision. It is not surprising that these high-quality optical pulses have revolutionized microfabrication technologies. Femtosecond lasers enabled processing of a wide range of materials (including heat sensitive and thermo reactive) with a sub-micrometer resolution. At present, nearly arbitrary shaped 2D and 3D structures can be produced by direct write photofabrication techniques using femtosecond laser pulses. In this paper we present a brief review of our recent progress in femtosecond (maskless, direct-write, nonlinear) laser lithography and 3D photofabrication technique.

Explosive crystallization of amorphous germanium of 0.89 and 1.80 microns in thickness deposited on quartz substrates was investigated. A scalloped, mixed, and columnar regime was observed. In situ images captured using dark field imaging reveal the shape of the explosive crystallization front. Crystallization was induced by a frequency tripled Nd:YAG laser (λ = 355 nm) focused to a tight line. A second Nd:YAG laser was frequency doubled (λ = 532 nm) and used as an illumination source for two time resolved pictures. The shape and speed of the explosive crystallization front is observed for various heat loss parameters and crystallization regimes and is generally in good agreement with the literature. Surface morphology is inspected by Atomic Force Microscopy (AFM) after explosive crystallization has completed.

We demonstrate the effect of N-doping in various phases, where N-doped states, bandgap shifts, and photocatalytic efficiencies are determined. The N-doped TiO₂ films were grown by pulsed-laser deposition using TiON targets. The crystal structures were analyzed using x-ray diffraction and Raman spectroscopy. The crystalline phases of TiO₂ were artificially controlled by choosing appropriate substrates. The anatase and rutile were epitaxially grown on (100) LaAlO₃ and (001) sapphire substrates. Rutile-anatase mixtured phase were grown on soda lime glass substrates. We here note that N-concentration strongly depends on the growth temperature, so that we kept the growth temperature at 300 °C in order to fix the N concentrations for respective specimens. Chemical bonding states of N within the matrix were investigated by x-ray photoelectron spectroscopy. The optical absorption and bandgap were measured using UV-VIS spectrometer. The photocatalytic activity of the films was evaluted by measuring the decompositon rate of methylene blue solution with the visible light illumination.

It is argued that the SWNT formation in laser-furnace technique is a kind of a liquid phase graphitization of non-graphitic forms of carbon catalyzed by molten metal-carbon nanoparticles. The melting of catalytic nanoparticles is a decisive condition for the SWNT nucleation and growth. It takes place at temperatures far below the respective eutectic temperature of the metal-carbon alloy and results from the enhanced dissolution of amorphous carbon in the metal nanoparticles. The acceleration of carbon diffusion in liquefied catalyst particles at one hand, and the competitive reduction of the free energy difference between the initial and the final carbon phases with temperature at the other hand can qualitatively explain the temperature dependencies of the SWNT yield and the observed SWNT growth rates. The results are summarized in the solid-liquid-solid model of the SWNT growth which is also applicable to the other physical and chemical methods of the SWNT synthesis.

We have developed an extreme sensitive trace element detection technique that has been labeled Laser ablation atomic fluorescence (LAAF) spectroscopy, and applied to a nanometer-scale solid surface analysis. The absolute weight of the detection limit of 870 ag (10^-18g) and high depth resolution of 3.6 nm had been demonstrated in trace sodium detection of polymethylmethacrylate. As a laser ablation was used in the LAAF spectroscopy, the behavior of the ablation plume is a very important factor for high sensitivity. So, we tried to control the plume by a buffer gas and an assist mask for more sensitive analysis. The diffusion velocity of the ablated particles was modified in collision with the gas molecules. Furthermore, it was found that the form of the plume was changed by the mask. Thus, improvement of the detection sensitivity of the LAAF is expected using this approach.

Measurements of ablation rate have traditionally been carried out only at normal incidence. However, in real-world applications ablation is often carried out at oblique angles, and it is useful to have prior knowledge of the ablation rate in this case. Detailed information about the angular dependence is also important for the development of ablation simulation tools, and can provide additional insight into the ablation mechanism. Previously we have reported on the angular dependence of direct-write ablation at 266 nm wavelength in solgel and polymer materials. In this paper we present a systematic study of angular dependence for excimer laser ablation of two polymer materials of interest for microfabrication: polycarbonate and SU8 photoresist. The results are used to improve simulation models to aid in mask design.

Various ablation processes including melt expulsion and debris deposition are demonstrated for intense laser ablation of bulk crystalline Si samples and thin copper films at different laser fluences by single tightly and multiple loosely focused laser pulses, respectively. Implications of our results to high-intensity femtosecond laser nano- and micro-machining of solids are discussed.

Surface micro-structuring of silica glass plates was performed by using laser-induced backside wet etching (LIBWE) upon irradiation with a single-mode laser beam from a diode-pumped solid-state UV laser at 266 nm. We have succeeded in a well-defined micro-pattern formation without debris and microcrack formations around the etched area on the basis of galvanometer-based point scanning system with the laser beam. The behavior of liquid ablation (explosive vaporization) was monitored by impulse pressure detection with a fast-response piezoelectric pressure gauge. LIBWE method is suitable for rapid prototyping and rapid manufacturing of surface microstructuing of silica glass as mask-less exposure system in a conventional atmospheric environment.

Selective area epitaxial (SAE) growth of strained SiGe:B (Boron) in the recessed source/drain (S/D) region of an MOS device is known to improve Si-PMOS performance due to enhancement of hole mobility and reduction of S/D resistance. However, the process may be adversely affected by pattern loading effects, SiGe relaxation, dislocation formation, dopant precipitation and contamination. These effects, if not controlled, will deteriorate device performance and yield. A nondestructive, in-line SAE process monitoring approach on patterned wafers is especially desired. A specialized, contact-less, carrier lifetime-based Room Temperature - Photoluminescence (RT-PL) method meets this demand. The RT-PL tool, which uses a novel excitation path design to achieve carrier confinement, device-suitable probing depth, submicron scanning resolution and a micron probe size, offers a quick, non-destructive assessment of strain, defects and contamination for SAE. In this paper, a systematic evaluation of blanket and selective growth layers is illustrated using layers with a Ge content of 15-25%, undoped and B-doped at ~10²⁰ cm^-3 concentration. For the as-grown conditions, we observed that SiGe remains in an unrelaxed state without extended dislocations being formed. These results suggest that SiGe composition could be further modified to optimize the associated mobility enhancement. Uniformity variations associated with SiGe composition and B-doping were identified. Excessive boron precipitation, metallic particle-originated defects and large contamination regions induced by processing tools were also exposed. The multiple and unique insights enabled through the RT-PL technique provide significant benefits towards decreasing process development and integration time, maintaining SiGe process in control and reducing device fabrication costs.

For many years, excimer laser are well established in industry as reliable UV light sources. For each application the beam characteristics have to fulfil different requirements and demands, in terms of technology and cost efficiency. One of the biggest advantages of the excimer laser is that it generates light at DUV-wavelengths and can produce high repetition rates at the same time. Many applications benefit from these characteristics. The trend toward smaller feature sizes in microlithography requires both a shift to shorter writing wavelengths, as well as the use of special techniques for photomask manufacture. These so-called Resolution Enhancement Techniques (RET) utilize more sophisticated mask making methods, thus increasing mask manufacturing costs. Furthermore, more advanced metrology methodologies must also be employed in order to inspect RET based masks, and this inspection much often be performed at the wavelength of use (193 nm) in order to accurately identify potential errors. Excimer lasers with high repetition rates and excellent beam characteristics are used for the detection and classification of mask defects in order to maximize yields during wafer fabrication. Excimer lasers are also used with spatial light modulators (SLM) to generate photomask patterns directly. This approach, as compared to conventional e-beam photo-mask writing technology, presents a way to manage the decreasing feature sizes with low operation cost. This technique also requires an excimer laser that delivers the high repetition rates necessary to sustain adequate process through put and extremely well stabilized energy output for writing accuracy. This paper reviews the performance and technology of high repetition rate excimer lasers specifically for use in photomask inspection and optical mask writing.

We investigate light concentration and field enhancement in nanometer-scale ridged aperture antennae. Resent numerical simulations have shown that nanoscale ridged apertures can concentrate light into nanometer domain. Most importantly, these ridge apertures also provide an optical transmission enhancement several orders of magnitude higher compared to regularly shaped nanoscale apertures. We employ the finite-difference time-domain (FDTD) method to design these apertures and fabricate them in thin metal films. A home-built near field scanning optical microscope (NSOM) is used to map the near-field intensity distribution of the light transmitted through these apertures. It is shown that the ridged apertures can produce a concentrated light spot far beyond the diffraction limit, with transmission enhancement orders of magnitude higher than regularly shaped apertures. Nanolithography applications of these nanoscale ridged aperture antennae are demonstrated.

We have investigated the deposition of biotinylated nano-beads on the surface of GaAs. The deposition procedure involved either direct coating of (001) GaAs with nano-beads, or binding the nano-beads with avidin immobilized on the surface of (001) GaAs through the interface of biotin and the NH₂ terminal group of 11-amino-1-undecanethiol (HS(CH₂)₁₁NH₂). The efficiency of binding was tested by washing the samples in a solution of a commercial detergent and by subjecting them to a deionized water ultrasonic bath. The results indicate that nano-beads deposited directly on the surface of (001) GaAs withstand the detergent washing test but they are easily removed by ultrasonic washing. In contrast, the nano-beads attached to (001) GaAs through the avidin-biotin-thiol interface survive the ultrasonic washing tests.

We present experimental results from second-harmonic generation studies of lithographically-prepared arrays of centrosymmetric gold nanorods, extending a previous treatment. The arrays serve as diffraction gratings, allowing control over the emission directions. The intrinsic radiation patterns from the nanoparticles are superimposed on the diffraction pattern, creating a unique angular distribution of second-harmonic light. The surface plasmon resonance mode of the particles is tuned to match the wavelength of the ultrafast Ti:sapphire excitation laser, dramatically enhancing the second-harmonic intensity but also increasing photodesorption effects. The details of the diffracted peak intensities depend sensitively on the geometry of the system and require a complex normalization of the data.

By irradiating glass containing spherical Ag nanoparticles successively with fs laser pulses at different wavelengths, we were able to produce three-dimensional, permanent anisotropic modifications based on shape deformations of the nanoparticles in this nanocomposite material. This novel method is able to create dichroism in the visible and near IR part of the spectrum by deformation of nanoparticles to oblong shapes oriented parallel to the laser polarization. Using samples with a vertical gradient of the fill factor of Ag nanoparticles in the glass substrate and an accordingly inhomogeneous broadening of the surface plasmon band, modifications in various depths can be made using different excitation wavelengths. The induced modifications are reversible: heating to ≈ 600^oC restores the spherical shape of Ag nanoparticles. This technique can be useful for manufacturing of different, 3D, polarization and wavelength selective micro-devices such as polarizers, filters, gratings, display and rewriting optical 3D data storage devices. As examples, we will demonstrate in this paper how (i) three areas of different color can be produced in three different depths of the sample and (ii) how a series of multicolor irradiations can be used to produce dichroic structures of high polarization contrast.

Sub-wavelength ripples are obtained by scanning a tightly focused beam (~1μm) of femtosecond laser radiation (λ=266, 400 and 800 nm, τ_p=100 fs) over the surface of various dielectrics, metals and silicon. The ripple pattern extends coherently over many overlapping laser pulses parallel and perpendicular to the polarisation. Investigated are the dependence of the ripple spacing on the lateral and temporal spacing of successive pulses, the direction of polarisation and the material. The evolution of the ripples is investigated by applying pulse bursts with N=1 to N=20 pulses. The conditions under which these phenomena occur are specified, and some possible mechanisms of ripple growth are discussed. The ripples have been continued not only in one dimension but also in two dimensions on the surface by several scans with an offset, resulting in the formation of an extended grating.

Self-assembled monolayers of the bidentate ferrocene containing ligands diisocyanoferrocene (1), bis(diphenylphosphanyl) ferrocene (2), and diisothiocyanatoferrocene (3) have been prepared and their adsorption kinetics on gold films were characterized with optical second-harmonic generation and ellipsometry. As opposed to ferrocenylfunctionalized ligands used in earlier studies, the redox-active moieties discussed here carry two anchor groups to "pin" them to the substrate in a well-defined orientation and distance to the surface. 1 and 3 show monolayer film formation that follows first order, while film assembly of 2 is best described by a second order Langmuir kinetics.

The interactions between an apertureless metal-coated tip and C-60 molecules have been studied by near-field Raman scattering technique. The electromagnetic and the chemical interaction through the local plasmon polaritons generated at the metallized tip apex provide an enhanced scattering and high spatial resolution much beyond the diffraction limits of the probing light. And additional enhancement under the gap-mode configuration, when C-60 molecules were sandwiched between a thin rough metal layer and metallized tip, was observed. Further, the mechanical interaction between the tip and C-60 molecules were studies by pressurizing C-60 molecules uniaxially by the tip. The photopolymerization of C-60 molecules was found to accelerate under high tip-pressure.

We demonstrate that ultraviolet light can be used to make sterically oriented covalent immobilization of a large variety of protein molecules onto either gold or thiolated quartz or silicium. The reaction mechanism behind the reported new technology involves light induced breakage of disulphide bridges in proteins upon UV illumination of nearby aromatic amino acids, resulting in the formation of free, reactive thiol groups that will form covalent bonds with thiol reactive surfaces. The protein molecules in general retain their function. The size of the immobilization spot is determined by the dimension of the UV beam. In principle, the spot size may be as small as 1 micrometer or less. We have developed the necessary technology for preparing large protein arrays of enzymes and fragments of monoclonal antibodies. Dedicated Image Processing Software has been developed for making quality assessment of the protein arrays. A multitude of important application areas such as drug carriers and drug delivery, bioelectronics, carbon nanotubes, nanoparticles as well as protein glue are discussed.