High-power Excimer Laser Research Articles

Histological evaluation of vascular changes after excimer laser angioplasty for neointimal formation after bare-metal stent implantation in rabbit iliac arteries.

Excimer laser is used to treat coronary artery disease, especially in case of lesions with thrombus and in-stent restenosis (ISR). However, there are no in vivo preclinical studies that have evaluated the pathological reactions of the vessel wall after excimer laser ablation. Bare-metal stents were placed in the external iliac arteries of six healthy rabbits. Twenty-eight days later, excimer laser ablation was performed with low-power (45 (fluency)/25 (rate)) in one side, and high-power (60/40) in the opposite side, followed by optical coherence tomography (OCT) evaluation. Rabbits were sacrificed 15min after the procedure, and histological assessment was performed. Morphometry analysis of OCT showed similar stent and lumen size between low-power and high-power group. Histological evaluation suggested endothelial cell loss, fibrin deposition, and tissue loss. The low-power group showed significantly less pathological changes compared with the high-power group: angle of endothelial cell loss, 32.4° vs. 191.7° (interquartile range, 8.8°-131.7° vs. 125.7°-279.5°; p < 0.01); fibrin deposition, 1.1° vs. 59.6° (0.0°-70.4° vs. 31.4°-178.4°; p = 0.03); and tissue loss 0.0° vs. 18.2° (0.0°-8.7° vs. 0.0°-42.7°; p = 0.03). The pathological changes in neointima were more prominent after high-power excimer laser ablation than after low-power excimer laser. To improve safety in clinical practice, understanding the pathological changes of tissues after excimer laser in lesions with ISR is essential.

Numerical Analysis of Corona Pre-Ionization for High-Power Discharge-Pumped XeCl* Excimer Lasers

The working gas of discharge-pumped excimer lasers is generally a mixture of rare gases and monohalide. Typically, the working gas is preconized to generate reproducible uniform glow discharge. In high-power (more than 100 W) excimer lasers, this pre-ionization is achieved through spark discharge in the discharge chamber. In this study, a high-power discharge-pumped XeCl* excimer laser with corona preionisation was designed to investigate the feasibility of applying corona preionisation in high-power excimer lasers as well as analyse the correlation of corona discharges characteristics with laser discharge properties. The electron avalanche triggered by ultraviolet preionisation in the laser was numerically studied by creating 2D models. The simulation results revealed that the additional ionisation induced by the secondary electron emission of the cathode together with the dielectric constant of the corona bars significantly affect the discharge current of the principal electrodes. Under the condition of the design values, the peak preionisation electron density between electrodes was approximately 108 cm−3, and the laser discharge was quite uniform, which theoretically proved the feasibility of using corona preionisation instead of spark discharge preionisation in high-power practical devices.

Numerical Analysis of Gas Flow Field of High-Power Excimer Laser

Numerical Analysis of Gas Flow Field of High-Power Excimer Laser

Iron Doped Zinc Oxide Thin Films Based Thermoelectric Temperature Sensors for Industrial Applications

Summary In the present work, thermoelectric properties of pulsed laser deposited (PLD) Iron doped Zinc Oxide (Fe:ZnO) thin films of varying thickness have been utilized for the fabrication of temperature sensor. An optimum thickness of 380 nm of Fe:ZnO thin film showed the maximum values of Seebeck coefficient, figure of merit and power factor of 94.6x10-3 mV/K, 2.7x10-3 and of 8.9x10-3 W/K2-m respectively at room temperature. These results indicate use of thermoelectric (Fe:ZnO) thin films as temperature sensor for the industrial applications. Introduction In many industrial applications continuous monitoring of temperature is needed. Typical temperature sensors are based on thermocouples or resistance elements made up of metals. However, these are not always suitable for many applications such as temperature sensors for liquids or gases in pipelines. Standard sensors inside such a fluid flow have an influence on the flow itself or hinder a cleaning of the pipeline system. Thus, novel thermoelectric temperature sensor based on metal oxide have been fabricated. Research efforts have been focused to determine best possible thermoelectric material to achieve highly efficient temperature sensor. The factors that contribute to find better thermoelectric materials include light weight, low noise or vibration and environment friendliness in addition to higher figure of merit. Thermoelectric materials can be in the form of bulk or thin film. Thin films are, however, expected to have lower thermal conductivity values as compared to the bulk materials due to the presence of strong phonon scattering at their interfaces. Thermoelectric thin films demonstrate improvement in thermoelectric efficiency and the possibility of their applications in flexible microelectronic devices. Experimental Fe doped ZnO (Fe:ZnO) thin films were deposited over corning glass substrates by Pulsed Laser Deposition (PLD) technique using ceramic Fe doped ZnO target. Fe:ZnO target was prepared by adding Fe2O3 (5%) to the Zinc oxide powder using solid state reaction method. A high power Excimer Laser (energy =100mJ), operating at a wavelength, λ=248 nm has been used for ablating the targets. Deposition of thin films was carried out in 100% O2 environment at 20 mTorr pressure. Thickness of Fe:ZnO thin films was varied from 200 nm to 480 nm. Thermoelectric measurements of the prepared thin films were carried out an indigenously developed set-up. The two ends of the sample were kept at different temperatures and the temperature was measured using thermocouples. After maintaining the temperature gradient at ends of the sample the voltage generated was measured using the precision digital multimeter. The measured voltage could be used for the calibration of temperature measurement. Results and Discussion Figure 1 shows the variation in thermoelectric voltage generated as a function of temperature gradient at the ends of the Fe:ZnO thin films. It can be observed from fig. 1 that with the increase in the temperature gradient from 5K to 30K, the induced thermoelectric voltage is found to be increasing from 0.1 mV to 8 mV in Fe:ZnO thin films. It is also observed that with increase in thickness from 200 nm to 380nm the thermoelectric voltage is found to be increasing upto 8 mV. However, with further increase in thickness to 480 nm the voltage generated is decreasing. . An optimum thickness of 380 nm of Fe:ZnO thin film showed the maximum values of Seebeck coefficient, figure of merit and power factor of 94.6x10-3 mV/K, 2.7x10-3 and of 8.9x10-3 W/K2-m respectively at room temperature. The obtained high value of Seebeck coefficient indicates the sensor could be calibrated to give measurements of temperature with great precision. These results indicate use of thermoelectric material (Fe:ZnO) thin films as temperature sensor for industrial applications. Conclusion The thermoelectric studies of Fe:ZnO thin films have been exploited for the development of temperature sensor. Thickness of Fe:ZnO thin films has been varied from 200 nm to 480 nm. An optimum thickness of 380 nm of Fe:ZnO thin film showed the maximum values of Seebeck coefficient, figure of merit and power factor of 94.6x10-3 mV/K, 2.7x10-3 and of 8.9x10-3 W/K2-m respectively at room temperature. Thus the thermoelectric voltage generated in the prepared Fe:ZnO thin film could be calibrated for the development of temperature sensor. Figure 1

Fine Line Routing and Micro via Patterning in ABF Enabled by Excimer Laser Ablation

Abstract Fan-Out technologies continue to be the main driver for advanced packaging, be it on wafer level (FOWLP) or panel level (FOPLP). There is a continuing need for higher density routing and heterogeneous integration of different devices, but also for continuous cost reduction. While traditional organic flip-chip substrates using semi-additive processes (SAP) have not been able to scale to ultra-fine RDL pitches and via opening below 10um, photo-sensitive spin-on dielectrics and RDL processes used for wafer level packaging do not sufficiently address the cost reduction need, and also face serious technical challenges. This paper presents the latest results from an innovative package RDL and micro via processes using excimer laser ablation in an especially developed non-photo sensitive material, to meet the market's most stringent requirements. To enable panel and wafer based interposers to reduce RDL cost and scale interconnect pitch to 40um and below, excimer laser ablation is introduced as a direct patterning process that uses proven industrialized excimer laser sources to emit high-energy pulses at short wavelengths to remove polymer materials with high precision and high throughput. The combination of a high-power excimer laser source, large-field laser mask and precision projection optics enables the accurate replication and placement of fine resolution circuit patterns without the need for any wet-processing. With excimer laser patterning technology the industry gains a much wider choice of dielectric materials (photo and non-photo) to help achieve further reductions in manufacturing costs as well as enhancements in interposer and package performance. In this paper, we propose a novel patterning process that uses excimer laser ablation to integrate via and RDL traces in one patterning step, followed by seed layer deposition, plating and planarization. The capability of this excimer laser patterning process in non-photo materials Ajinomoto Build-up Film, which is abbreviated to “ABF” in this paper, will be discussed, and its technical robustness and commercial advantages are demonstrated. We will present electrical and reliability data of Via and RDL traces patterned by excimer laser in ABF material.

Embedded RDL formation in Non-Photo Polymers using Excimer Laser Ablation

Abstract The continuous trend towards miniaturization, increasing performance and mobility of electronic devices drives interconnect density and integration, not only at the chip level, but also at interposer and package level. Silicon interposers coming from wafer foundries using back end of line (BEOL) redistribution layer (RDL) processes have been introduced successfully. However, there is a continuing need for low cost interposers based on large organic or glass panels. While traditional organic flip-chip substrates using semi-additive processes (SAP) have not been able to scale to ultra-fine RDL pitches, photo-sensitive spin-on dielectrics and RDL processes used for wafer level packaging do not sufficiently address the cost reduction need, This paper presents the latest results from cost effective and innovative package RDL processes using excimer laser ablation, to meet the market's most stringent requirements. To enable panel and wafer based interposers to reduce RDL cost and scale interconnect pitch to 40um and below, excimer laser ablation is introduced as a direct patterning process that uses proven industrialized excimer laser sources to emit high-energy pulses at short wavelengths to remove polymer materials with high precision and high throughput. The combination of a high-power excimer laser source, large-field laser mask and precision projection optics enables the accurate replication and placement of fine resolution circuit patterns without the need for any wet-processing. In addition, with excimer laser patterning technology the industry gains a much wider choice of dielectric materials (photo and non-photo) to help achieve further reductions in manufacturing costs as well as enhancements in interposer and package performance. In this paper, we propose new process that uses excimer laser ablation to integrate via and RDL traces in one patterning process step, followed by seed layer deposition, plating and planarization steps. A new integration process flow is proposed, and its technical robustness and commercial advantages have been demonstrated. The capability of this excimer laser process to extend the current material portfolio to non-photo materials will be discussed, and its commercial benefits as compared to the current process of record (POR) will be highlighted.

Selective Fabrication of SiC/Si Diodes by Excimer Laser Under Ambient Conditions

This letter presents SiC/Si diodes fabricated by the selective growth of SiC on Si substrate under ambient (atmospheric) conditions. The selective growth of $\beta $ -SiC was obtained by irradiating a high-power KrF excimer laser beam on a polymethyl methacrylate (PMMA)-coated Si wafer. The laser decomposed carbon atoms from the PMMA, which dissolve into molten Si to form SiC. The Raman spectrum of the grown samples shows a dominant band in the range of 930–990 cm $^{-1}$ , i.e., the spectral region characteristic for $\beta $ -SiC. The quality of SiC can be optimized by changing the induced power. The best performing SiC/Si diode shows a good rectification ratio of $\sim 3 \times 10^{4}$ (±1 V), a low leakage current density of $\sim 1~\mu \text{A}$ /cm2 (−1 V), and high breakdown (>200 V), which confirms the high quality of the SiC/Si interface. The doping of SiC was calculated from 1/ $C ^{2}$ versus $V$ plot and found to be $\sim 5 \times 10^{15}$ cm $^{-3}$ . In addition, the measured photoelectric response shows a short circuit current density of 17 mA/cm2, an open circuit voltage of 0.33 V, and a fill factor of 62%.

连续分振幅式高功率准分子激光角多路编码光路设计

连续分振幅式高功率准分子激光角多路编码光路设计

About Losses in Pumping Generators of High-Power Electrodischarge Excimer Lasers

Energy losses in pumping systems of discharge high-power lasers are investigated. To estimate the losses, the discharge circuit operation was modeled, and its calculation was performed using the program PSpice. Results of measurements and calculations demonstrate that the resistance of a rail gap with electric field distortion exceeds several times the resistance of a single-channel gap without field distortion. A difference in the resistances is explained by different mechanisms of discharge burning: in the first case diffusion mechanism and in the second case the spark mechanism. The low efficiency of the high-power excimer lasers (~1%) is explained by high energy losses in the rail gap that reach more than 50% of the initially stored energy.

高功率准分子激光MOPA系统中的三路激光准直技术研究

高功率准分子激光MOPA系统中的三路激光准直技术研究

高功率准分子激光MOPA系统光束平滑技术研究

高功率准分子激光MOPA系统光束平滑技术研究

基于电光开关的高功率准分子激光MOPA系统ASE抑制

基于电光开关的高功率准分子激光MOPA系统ASE抑制

高功率准分子激光系统光学设计

高功率准分子激光系统光学设计

高功率准分子激光系统光束指向稳定性模拟

高功率准分子激光系统光束指向稳定性模拟

Effect of hydrogen plasma treatment on the field emission of diamond-like films deposited by high power excimer laser ablation

The effect of hydrogen plasma treatment on the electron field emission of diamondlike carbon films (DLCs) deposited by high frequency and high power pulsed XeCl excimer laser ablation of pyrolytic graphite targets at room temperature was studied. Results indicated that the films exhibited improved electron emission, with the threshold field of the films decreased from 26 to 19 V/μm. Meanwhile, the current density increased considerably after the treatment. Two factors were responsible for the results. One was that the graphiterich DLC film surface formed with low energy carbon atoms or clusters during growth process was removed by the hydrogen plasma with the formation of a new surface comprised of high density sp3 bonded carbons, which exhibited a low electron affinity and good field emission . The other was that the dangling bonds of the carbon atoms on the film surface were saturated with Hatoms after the treatment, which further decreased the electron affinity.

New excimer lasers advance coated conductor upscaling

High power excimer lasers designed for use in pulsed laser deposition (PLD) of thin films, including coated conductor layers allow faster deposition rates and eventually faster tape feed rates than before. Throughput increase depends on the individual PLD system design and can be driven mainly by excimer laser repetition rate or by pulse energy. Intelligent beam delivery as well as substrate-target scanning algorithms will leverage the full potential of the latest generation of high power excimer lasers.

10.1007/s11455-008-3002-6

We have studied the action of nanosecond-pulsed high-power KrF excimer laser radiation on the composite layer of a soda-lime-silicate glass containing ion-synthesized silver nanoparticles, with the purpose of modifying the material properties by changing the size of metal particles. It is established that, as the number of laser pulses increases, the treatment leads to a decrease in the average size of silver nanoparticles in the ionimplanted layer. However, after the almost complete disintegration of silver particles, a further increase in the number of pulses leads to new growth and a coarsening of the metal particles. The observed phenomena are interpreted in terms of heating of the surface layer of glass and silver particles by nanosecond laser pulses and the related increase in the diffusion mobility of silver atoms in the glass matrix.

Improvement of green cathodoluminescence of zinc oxide stacked films prepared by high-power excimer laser irradiation of sol–gel-derived precursors

Zinc oxide (ZnO) stacked films were prepared by repeating a procedure involving KrF excimer laser irradiation at various energy fluences ( E f) of sol–gel-derived precursors. All the stacked films are wurtzite-type and highly c-axis oriented on glass substrates. The green cathodoluminescence (CL) efficiency of the films is strongly influenced by the preparation conditions. Especially, laser E f and stacking number are important control factors. The stacked film prepared under optimized preparation conditions consists of large grains and indicate low electric resistivity. The green CL efficiency of the stacked film is 0.0139 lm/W, which is higher than those of ZnO thin films prepared by a single stacking.

Fabrication of crystalline Si spheres with atomic-scale surface smoothness using homogenized KrF excimer laser reformation system

A technique applying the homogenized KrF excimer laser reformation to fabricate Si spheres on the silicon on insulator platform is presented. High-power excimer laser was used to illuminate the Si rods which were fabricated using typical procedures. The Si rods were then melted and reshaped to spheres due to surface tension. This method is capable of fabricating submicrometer Si spheres with extremely smooth surface. Atomic force microscopy was used to reveal the atomic-scale surface smoothness of the fabricated Si spheres. It shows that root-mean-square roughness is smaller than 0.1nm. In addition, tunneling electron microscopy was used to investigate crystalline property of the Si spheres, showing that single-crystalline Si with lattice plane spacing of about 0.24nm was formed after the transformation of the Si rod into the sphere.

Uniform Square Polycrystalline Silicon Fabricated by Employing Periodic Metallic Pads and SiON Absorption Layer for Thin Film Transistors

The poly crystalline silicon with regular square grains is fabricated by employing metallic (Cr/Al) periodic pads as the heat sinks and with underlying silicon oxynitride (SiON) as the heat absorption layer. The maximum lateral growth length of the poly-Si is 1.78 mum by this method. If the metal pads are periodically arranged, the poly-Si can grow to regular square grains following the high power excimer laser annealing. After removing the metallic pads, the low power laser shot transfers the a-Si:H under the original metallic pads to poly-Si without destroying the square grains. The TFTs fabricated by this method achieve a field effect mobility of 450 cm2/Vmiddots and an on/off current ratio exceeding 107. It is found that the TFT with smaller channel width and length results in a better subthreshold swing because it contains fewer grain boundaries and defects.