Papers by Keyword: Laser Ablation

Abstract: Silicon carbide (SiC) wafers are essential for next-generation power devices, however conventional dicing methods often induce cracks and Basal Plane Dislocations (BPDs), reducing device reliability. This study demonstrates BPD-free dicing of epitaxial SiC wafers using Water jet Guided Laser (WGL) processing. Full-thickness cutting was performed on 350 μm-thickness wafers with a 10 μm-thickness epitaxial layer using a YAG laser (532 nm wavelength, 200 ns pulse width, 10 kHz repetition rate, 30–80 W output) on an LB300 system. BPD evaluation was carried out by X-ray topography (XRT) with the-1-128 reflection before and after cutting. The results showed no generation or propagation of new BPDs, and pre-existing BPDs did not glide, confirming that WGL processing enables BPD-free machining. These results are attributed to the ablation-based nature of WGL with water assistance, which avoids mechanical stress on epitaxial SiC wafers.

Abstract: Adhesive bonding is widely employed for joining complex-shaped components due to its ability to distribute stresses uniformly, preserve material integrity, and eliminate mechanical fasteners. However, the permanent nature of conventional adhesives and the difficulty of clean disassembly hinder the reuse of bonded joints, limiting recyclability and sustainability. This study investigates laser cleaning as an enabling technology for re-bonding single-lap joints. An ultrashort pulsed laser was applied to remove residual epoxy adhesive from AA6061 aluminum alloy substrates after debonding. Surface characterization revealed that laser ablation produces micrometric roughness, and laser processing can be further tailored to generate laser-induced periodic surface structures (LIPSS), influencing morphology, chemistry, and wettability. Mechanical testing demonstrated that laser cleaning also improves the tensile lap-shear strength of re-bonded untreated joints. These findings confirm that laser cleaning effectively restores substrate surfaces and, when combined with controlled texturing, can enhance bonding performance. The proposed approach supports repair and recycling strategies, contributing to extended component lifecycles and circular economy objectives.

Abstract: Low-process damage dicing technologies are required to improve the reliability of silicon carbide (SiC) devices. Existing methods, such as ultrasonic diamond blade dicing, dry laser dicing, and stealth dicing, introduce mechanical or thermal stresses that lead to cracks and dislocations, including basal plane dislocations (BPDs), which degrade device quality. In this study, we assess the crystalline defects induced by water jet guided laser (WGL) processing on a SiC wafer using X-ray topography (XRT) and investigate the underlying processing mechanisms through Energy Dispersive X-ray Spectroscopy (EDX). The asymmetric contrast observed along the processed grooves in the XRT images was due to the X-ray irradiation direction, and no significant BPD formation was observed. The EDX results showed that the processed surface was oxidized by laser ablation. Thus, WGL processing can provide damage-free dicing of SiC wafers with minimal mechanical stress and defects.

Abstract: A damage-free SiC wafer dicing method has been strongly required for practical applications of power devices. In this research, we propose water jet guided laser processing as a novel dicing method. Water jet guided laser processing, which uses a high-pressure fine water jet as waveguide, could generate no cracks or dislocations in crystal. In this paper, water jet guided laser grooving quality was evaluated to demonstrate there should be no chippings and basal plane dislocations. Scanning electron microscopic and X-ray topography observations were conducted. The results indicated the superiority of water jet guided laser dicing to a conventional dicing method.

Abstract: Fiber laser of 1064 nm wavelength was employed for micro/nano machining process of silicon and quartz substrates. The experimental data reveal formation of silicon nanoparticles by pulse laser ablation in liquid. Various characterization techniques were used such as UV-Visible absorption, SEM morphology to examine silicon nanoparticles. Moreover, generation of microbeams from micro lens array was created by direct writing of fiber laser on quartz. Theoretical calculations using COMSOL software were adopted to estimate the surface temperature distribution at silicon and quartz surface and underneath. It is found that maximum temperature of about (4600 K) and (2400 K) for silicon and quartz respectively when 15 W laser power, 127 ns pulse duration, 30 KHz frequency and 100 mm/sec laser speed was used. Potential applications of silicon nanoparticles and microbeams array in optoelectronics and biological imaging can be conducted due to the controllable laser micro/nano machining process.

Abstract: The new laser ablation technique has been developed for analysis of metallic impurities in SiC and GaN wafers. Particles generated by a femto-second laser ablation were aspirated by an ejector and introduced to an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) via a Gas Exchange Device (GED) and analyzed. A Metal Standard Aerosol Generation (MSAG) was used for quantitation of metallic impurities in SiC and GaN wafers.

Abstract: The micromaching of silicon carbide using femtosecond laser pulses is becoming an important field of research. High-repetition-rate sub-pulse trains, so-called pulse bursts, are a particularly promising route towards completely new process regimes. We report on the results of micro-punching n-type 4H-silicon carbide wafers using GHz pulse burst in order to systematically investigate the influence of the temporal energy distribution on laser processing. Pulse-burst experiments are performed at a laser wavelength of λ= 1030 nm using a single GHz burst containing a varying number of pulses and then compared with standard single femtosecond pulse exposures. The pulse energy is swept across the ablation threshold. For each set of parameters, the micromachining efficiency is evaluated in terms of ablation efficiency and burr characteristics. Scanning electron micrographs provide qualitative information about the machining quality. The characteristics of the laser modification are discussed in relation to an increase in the number of pulses in a burst envelope and to an increase in pulse energy. We observe that, compared to a single pulse, a GHz burst comprised of 10 lower-energy pulses leads to an increase in the ablation rate by a factor of ≤ 10.

Abstract: Synthesis of silver nanoparticles (AgNP) by pulsed liquid laser ablation (PLAL) produces AgNPs that are better suited for biological applications compared to those prepared by standard wet-chemical methods. These were mainly achieved by water ablation with pulse widths in the nanosecond range. In the case of surface NP activation, we previously detected a strong surface-enhanced Raman scattering (SERS) signal from such AgNPs. To do this, we dilute Colloid slightly with LiCl. These surface alterations may have an effect on the NPs' capability to combat bacteria. every time, AgNPs with a median diameter of under ten nm were created., that has been incontestible in alternative studies to be the optimum size for germicidal activity.. Furthermore, minimum restrictive concentration (MIC) values for LiCl-modified AgNPs fell inside a slender vary of 1.1-3.8 g/mL, creating them the foremost efficient. This result's believed to be explained by the metal surface's enhanced surface reactivity, which is brought on by the existence of charged active sites.

Abstract: The present research shows the possibility of using an ytterbium nanosecond pulsed fiber laser for wear resistance improvement of carbon and alloy steels. The wear test was performed in accordance with the block-on-ring scheme with dry sliding friction on a friction machine. Surface dispersing/alloying was carried out from a boron carbide paste. This leads to a significant wear resistance improvement of steels. It was revealed that the mass loss during wear test reduced by several times after laser treatment compared to the non-treated samples. The wear mechanism differs depending on the type of steel and largely refers to their microstructure and composition. The tribo-oxide layer forms during the wear test.

Abstract: Gallium arsenide (GaAs) nanoparticles' optical and emission properties can be tuned bychanging their size across the visible spectrum. GaAs nanoparticles' optical characteristics aredegraded by oxidation on their surface. This work investigated the optical constants and the opticalband gap for a GaAs nanoparticle immersed in acetone using the laser ablation into liquids (LAL)technique after being exposed to a Nd: YAG pulsed laser operating at the wavelength (1064nm)10Hz frequency, and 7ns pulse width for a fixed flounce of 1.32 J/cm2, and the time of ablationwas 5 minutes. In order to calculate the optical conductivity (σ), refractive index (n), extinctioncoefficient (k), dielectric constant, absorption coefficient (α), and optical band gap, an opticalinvestigation was carried out utilizing a UV-Visible Spectrophotometer region in the wavelengthrange 300-1200 nm. The band gap energy was determined to be 3.8 eV, which is greater than thebulk Ga energy. The band gap energy of nanoparticles increases with increasing laser pulse energyand decreases with increasing pulse repetition rate. Transmission spectra increased as wavelengthsincreased, while optical absorption coefficients, extinction coefficients, and refractive coefficientsdecreased. The difference in optical constants is explained by defect states and the average bandenergy of the system. The acetone stability test reveals a peak at -0.69 mV, indicating low stabilityin nanoparticles.