Excimer Laser Processing Research Articles

Principal Analysis and Application of Laser Technology in Integrated Circuits

Since the constant development of science and technology and the popularization of electronic devices, integrated circuits are also developing in the direction of large scale and high precision. This requires the processing of integrated circuits to be constantly refined. This also prompted the laser technology has become an important processing technology in the manufacturing process of large-scale integrated circuits. Laser processing technology is a non-contact processing, its beam diameter is small, high-energy density, high productivity, stable and reliable processing quality. This paper for the laser welding, laser direct writing, laser detection and laser cleaning overview of the four-laser technology in the application of large-scale integrated circuits. And the working principle, type and process characteristics of these laser technologies are discussed. The development of laser technology has also limited the production of large-scale integrated circuits in some aspects. With the semiconductor laser, excimer laser process continues to mature, laser technology in integrated circuits will continue to expand the scope of application and break through the obstacles.

Pulsed 193 nm Excimer laser processing of 4H–SiC (0001) wafers with radiant exposure dependent in situ reflectivity studies for process optimization

Pulsed 193 nm Excimer laser processing of 4H–SiC (0001) wafers with radiant exposure dependent in situ reflectivity studies for process optimization

Excimer laser processing of nanostructured SnO2 thin films and its impact on LPG sensing

KrF excimer laser (λ = 248 nm) has been employed to anneal nanocrystalline Tin oxide (SnO2) films deposited at 200 °C using spray pyrolysis. With the increase of irradiation laser fluence, the film crystallinity has been improved while the matrix stress decreased along all the crystal planes except (110) and (301), for an energy density of 150 mJ/cm2 as compared to non-irradiated films. The maximum liquid petroleum gas (LPG) response observed for a fluence 150 mJ/cm2 is 92.6% at 350 °C whereas a response is 4% at the onset sensing temperature of 100 °C. Moreover, the response and recovery times have also improved by the laser processing and the cross sensitivity for NH3 and NO2 gases are in a desirable range. FESEM images of irradiated films show polygonal shaped distributions of aggregated nanocrystalline particle-clusters with grain boundaries and nanovoids. XPS shows oxygen deficient lattice besides surface and/or pore-bound oxygen contributions. Raman analyses confirm the sub-stoichiometric SnO2-x phases and a high concentration of defects such as oxygen vacancies (OVs) on surface sites. Based on these observations, the gas sensing mechanism is discussed in brief.

Residual Image Suppression Through Annealing Process of Amorphous Indium Gallium Zinc Oxide Thin Film Transistor for Plastic Organic Light-Emitting Diode Display.

For the evaluation of the residual image suppression, the amorphous indium-gallium-zinc-oxide thin film transistor was manufactured with electric field shield metal on silicon oxide multi-buffer layer, without the need for a silicon crystallization process through the excimer laser process, and is advantageous for the manufacture of large-scale plastic organic light-emitting display. We conducted a study on the propensity to suppress a residual image according to the temperature of the annealing process in amorphous indium gallium zinc oxide. The evaluation divided by the ambient process temperature conditions to measure the change and restoration tendency of the gray current by the black/white current of thin film transistors, and for precise measurement of the current change intervals, the current was analyzed in 0.004 seconds per point. Through the study, residual image of amorphous Indium Gallium Zinc Oxide transistor was found to be suppressed as the temperature of the annealing crystallization increased from 250°C to 325°C, and there was no improvement effect on the 325°C or higher. The trend of threshold voltage shift of thin film transistors according to the two process temperature conditions, 250°C and 325°C, was analyzed by Two sample T analysis method, and the analysis confirmed that the trend of current deterioration is different through p-value 0.007.

Microfluidic array chip based on excimer laser processing technology for the construction of in vitro graphical neuronal network

To construct a graphical neural network in vitro and explore the morphological effects of neural network structural changes on neurons, this study aimed to introduce a method for fabricating microfluidic array chips with different graphical structures based on 248-nm excimer laser one-step etching. Through the comparative analysis of the graphical neural network cultured on our microfluidic array chip with the one on the glass slide, the morphological effects of the neural network on the morphology of the neurons were studied. First, the design of the chip was completed according to the specific structure of the neurons and the simulation of the flow field. The chips were fabricated by excimer laser processing combined with the casting technology. Neurons were cultured on the chip, and a graphical neural network was formed. The growth status of the neural network was analyzed by microscopy and immunofluorescence technology, and compared with the random neural network cultured on glass slides. The results showed that the neurons on the array chips grew in microchannels, and neurites grew along the direction of the channel, interlacing to form a neural network. Furthermore, when the structure of the neural network was graphically changed, the internal neuron morphology changed: on the same culture days, the maximum length of the neurites of the graphical neural network was higher than the average length of the neurites of the random neural network. This research can provide the foundation for the exploration of the neural network mechanism of neurological diseases.

Deep ultraviolet excimer laser processing for the micro via hole on semiconductor package

Moore's law has almost reached the limit of resolution on semiconductor die and, therefore, multidie packaging is one of the alternative solutions. Substrate materials currently use organic build-up films and silicon substrates [through silicon via (TSV)] in applications. But recently, organic films, too, have reached the resolution limit, and TSV is expensive. In this situation, nonalkali glass (glass) and fused silica (SiO2) substrates are expected to be good alternatives in high-frequency signal transfer applications like 5G telecommunication. But the via holes are hard to process with less defects (tips and cracks) on the glass and SiO2 substrates. Deep ultraviolet (DUV) excimer laser ablation is expected to have a finer (<10 μm) resolution with a shorter wavelength (248–193 nm) and also hard material processing with a higher photon energy (5–6.4 eV). Therefore, the authors have explored the application of the DUV excimer laser ablation process for a via hole on hard materials like glass and SiO2 substrates. In this study, they have investigated the via hole quality through the DUV excimer laser ablation process. The results show the possibilities of micromachining on both glass and SiO2 substrates. The authors have succeeded by achieving a value of <50 μm through the via hole grid aspect ratio of 6 on the glass substrate without any significant defects. As the ablation rate is quite an affordable value, DUV excimer lasers are expected to play a crucial role in the next-generation manufacturing process for semiconductor packages. The authors also investigate the SiO2 substrate with DUV excimer lasers.

Periodic Surface Nano-Structures on Silicon Solar Cells Produced by Non-Thermal Excimer Laser Processing

Periodic Surface Nano-Structures on Silicon Solar Cells Produced by Non-Thermal Excimer Laser Processing

Micro-structured optical fiber sensor for simultaneous measurement of temperature and refractive index

Abstract Through using micro-machining method for optical fiber sensor, a kind of miniature, compact and composite structural all-fiber sensor is presented. Based on manufacturing two micro-holes with certain distance in ordinary single-mode fiber Bragg grating (FBG) by excimer laser processing technique, we fabricate a dual Fabry–Perot-FBG (FP-FBG) composite fiber interferometric sensor, which can be used in simultaneous measurement for liquid’s refractive index (RI) and temperature change. Due to every micro-hole and the dual micro-holes in fiber acting as different Fabry–Perot (FP) cavities, this kind of sensor has not only different RI sensitivities but also different temperature sensitivities, which are corresponding to the wavelength shifts of the fine interference fringes and spectral envelope, respectively. The experimental results show that the spectral wavelength shift keep better linear response for temperature and RI change, so that we can select the higher temperature and RI sensitivities as well as the analyzed sensitivities of FBG to utilize them for constituting a sensitivity coefficients matrix. Finally, the variations of liquid’s temperature and RI are detected effectively, and the resolutions can reach to 0.1 °C and 1.0 × 10 - 5 RIU. These characteristics are what other single-type sensors don’t have, so that this kind of all-fiber dual FP-FBG composite fiber interferometric sensor can be used in extremely tiny liquid environment for measuring different physical quantities simultaneously.

Excimer Laser Processing of Cast Mg-Al-Zn (AZ91D) and Mg-Al (AM60B) Alloys for Improved Corrosion Resistance

Poor intrinsic corrosion resistance of Mg alloys is often attributed to recommended heterogeneous microstructures containing more electrochemically noble secondary phases resulting in the preferential dissolution of Mg. The investigation herein demonstrates the laser (excimer laser, λ = 248 nm, 25 ns) processing of cast Mg-Al-Zn (AZ91D) and Mg-Al (AM60B) alloys mitigates the impact β-Mg17Al12 and Al-Mn intermetallic particles have on the corrosion resistance. Control of the laser fluence reduced surface defects commonly formed while improving the corrosion lifetime. Scanning electron microscopy of laser processed specimens revealed significant dissolution of the β phase and Al-Mn intermetallic particles. The corrosion response showed that an order of magnitude reduction in H2 evolution reaction rate was achieved for all times of immersion. Electron impedance spectroscopy showed a 10-fold increase in the estimated polarization resistance with laser processed surfaces, exhibiting a corrosion lifetime of the...

Incubation phenomena during UV‐pulse excimer laser processing of silicone elastomers

ABSTRACTObservations of the interaction of poly(dimethylsiloxane) (PDMS) sheet (210 μm thick) with KrF excimer laser irradiation (λ = 248 nm), with low energy of 50 mJ/pulse are presented. The negative ablation or swelling of the material caused by low frequency pulse irradiation is characterized by optical microscopy, μ‐Raman spectrometry and X‐ray micro‐tomography. The appearance of defected areas in the form of cones inside the sheet and changes of material chemistry are discussed. These phenomena are considered as a precursor of the ablation occurring after passing a threshold of absorbed laser irradiation energy. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44541.

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.

Microlens beam homogenizer for excimer laser processing

This paper reports the results of developed microlens beam homogenizer for the 248 nm excimer laser. Excimer laser has a complex irradiance profile, and it is difficult to design a homogenizer for this kind of light source. We present a method to design microlens beam homogenizer according to the propagation properties of the irradiance profile. Since the intensity distribution image of excimer laser raw beam can be photographed by the laser beam analyzer, we use matlab to analyze the image and extract relevant information to calculate. With the calculated data, we simulate a virtual excimer laser source which has the same irradiance profile as the initial beam. According to the energy spatial distribution characteristics of the virtual excimer laser source, a microlens beam homogenizer is designed. The designed microlens homogenizer has been fabricated and tested. Measurements of the irradiance profile is presented and compared to the ideal design. After shaping and homogenization, a highly uniform beam spot is obtained finally. The profile of this beam spot is a square flat-top with dimensions of approximately 17 × 17 mm2. This optical system can transform approximately 80% of the total input beam power into the work plane of output beam, and beam uniformity of better than ±3% is realized. The successful development of this optical system can provide a technical support for the excimer laser processing with high quality and efficiency.

Embedded RDL Enabled by Excimer Laser Ablation

The continuous trend of the miniaturization, increasing performance and mobility of electronic devices drive the requirements of the chip itself but also its package type. The current integration process based on photolithography will be reaching the limit to develop cost effective and innovative package designs that meet the market requirements. In support of this technology trend and to address the industry problems Excimer laser ablation has been adopted in the semiconductor packaging industry and is now available as disruptive patterning technology. The complementary technology offers the promise of further reductions in manufacturing costs as well as enhancements in chip or package performance. Excimer laser ablation is a direct etching process that uses the advantage of the Excimer laser source to emit high energy pulses at short wavelengths. The combination of the Excimer laser source and dedicated projection optics ensures the capability of high resolution imaging. With this type of patterning technology the industry gets access to materials that do not require photo patterning. The paper proposes a new process based on the front end of line dual damascene integration flow for building multilayer RDL for Advanced Packaging using Excimer laser ablation. The new process uses Excimer laser ablation as the critical method to integrate via and RDL traces in one patterning process step, followed by seed layer deposition, plating and standard planarization processes. In this presentation, we will explain in detail the new proposed integration flow and further demonstrate its technical robustness for the chip interconnect combined with its commercial benefits to users. We will also cover the capability of this Excimer laser process to extend the material selection to non-photo materials.

The effect of microarc oxidation and excimer laser processing on the microstructure and corrosion resistance of Zr–1Nb alloy

The main purpose of this research was to investigate the effect of microarc oxidation (MAO) and excimer laser processing on the corrosion resistance of Zr–1Nb alloy in service environment. The pre-oxide film was fabricated on the surface of Zr–1Nb cladding tubes by MAO processing, and then subjected to KrF excimer laser irradiation. The surface morphology of the pre-oxide film was observed using a scanning electron microscope; phase compositions and quantities were determined using an X-ray diffraction; surface roughness was determined using a profilometer; and thermal expansion coefficient was measured using a dilatometer. Autoclave experiments were conducted for 94 days in an aqueous condition of 360 °C under 18.6 MPa in 0.01 mol/L LiOH solutions. The results showed that MAO + laser treatment resulted in a significant increase in the corrosion resistance of Zr–1Nb cladding tubes at high temperatures, because laser melting and etching could lead to a reduction in surface roughness and an increase in compactness of the pre-oxide film, and laser processing could promote the transformation of m-ZrO2 phase to t-ZrO2 phase. The best corrosion resistance was obtained when the pulse energy was 500 mJ, scanning speed was 0.13 mm/s, and pulse number was 2400.

Resin-dentin bonding interface after photochemical surface treatment.

The aim of this study is to elucidate the structure of the resin-dentin interface formed by photochemical dentin treatment using an argon fluoride (ArF) excimer laser. The ArF excimer laser processes material by photochemical reaction without generating heat, while also providing surface conditioning that enhances material adhesion. In the case of bonding between resin and dentin, we demonstrated in a previous study that laser etching using an ArF excimer laser produced bonding strength comparable to that of the traditional bonding process; however, conditions of the bonding interface have not been fully investigated. A dentin surface was irradiated in air with an ArF excimer laser followed by bonding treatment. Cross sections were observed under light microscope, transmission electron microscope (TEM), and scanning electron microscope, then analyzed using an energy dispersive X-ray spectroscope (EDS): EDS line profiles of the elements C, O, Si, Cl, P, and Ca at the resin-dentin interface were obtained. The density of C in resin decreased as it approached the interface, reaching its lowest level within the dentin at a depth of 2 μm from the resin-dentin interface on EDS. There was no hybrid layer observed at the interface on TEM. Therefore, it was suggested that the resin monomer infiltrated into the microspaces produced on the dentin surface by laser abrasion. The monomer infiltration without hybrid layer is thought to be the adhesion mechanism after laser etching. Therefore, the photochemical processes at the bonding interface achieved using the ArF excimer laser has great potential to be developed into a new bonding system in dentistry.

Laser perforated accordion nerve conduit of poly(lactide‐co‐glycolide‐co‐ɛ‐caprolactone)

Accordion nerve conduit of poly(lactide-co-glycolide-co-ε-caprolactone) with perforations was developed by excimer laser processing. We evaluated its in vivo function for nerve repairing and discussed the influence of pore size and density. It was found that perforations help inner nerve regeneration remarkably, which effect is unrelated to pore size or density, and is not parallel with revascularization increment. Inducing of permeability only to allow substance exchange but not vessel ingrowth could facilitate nerve regeneration too. Perforating micropores with the size of 100 μm and the density of 25/cm provides permeability and vessel ingrowth both, therefore promotes the axon extension the best, larger, and more pores do not advance axon regeneration more.

In situ monitoring of excimer laser annealing of tin-doped indium oxide films for the development of a low-temperature fabrication process

In this paper, in situ monitoring of excimer laser irradiation processing is examined for application to the production of thin films of transparent conductive oxides (TCOs) such as tin-doped indium oxide (ITO). Numerical simulations reveal that differences in the thin film state, for example, in the dopant levels, could greatly affect the proper laser fluence, suggesting the importance of in situ monitoring of the excimer laser processing. The thermal emission signals of ITO thin films under irradiation by a pulsed ultraviolet laser were successfully detected in situ with a near-infrared sensor on a nanosecond timescale. Non-monotonic decay of the thermal radiation from the ITO thin films was observed under XeCl laser irradiation above a certain fluence. At this fluence, the surface morphology of the ITO thin films observed by atomic force microscopy changed to a microstructure reflecting melting and solidification. This correspondence between the thermal radiation and morphology suggests that the observed non-monotonic decay was caused by recalescence upon solidification and that the in situ monitoring technique can be used to detect such phase changes.

Development of Minimally Invasive Microneedle Made of Tungsten – Sharpening Through Electrochemical Etching and Hole Processing for Drawing up Liquid Using Excimer Laser –

A tungsten needle was fabricated by electrochemically etching a thin wire with a diameter of 100 µm, with the goal of using it in minimally invasive medical treatments. The sharpness and smoothness of the tip were effective for easy insertion because they provided a large stress concentration and small amount of friction, respectively. An experiment involving the insertion of the fabricated needle into artificial skinmade of silicone rubber was carried out. The resistance force during the insertion was greatly reduced because of the small size of the needle, which was comparable to a mosquito’s proboscis. Despite the ultra-thin shape, the microneedle neither buckled nor broke because of the high hardness of the tungsten material. A hole was fabricated in the tungsten needle using excimer laser processing and electrochemical etching. Water and blood sampling were successfully achieved using this needle.

Excimer laser crystallization of amorphous silicon on metallic substrate

An attempt has been made to achieve the crystallization of silicon thin film on metallic foils by long pulse duration excimer laser processing. Amorphous silicon thin films (100 nm) were deposited by radiofrequency magnetron sputtering on a commercial metallic alloy (N42-FeNi made of 41 % of Ni) coated by a tantalum nitride (TaN) layer. The TaN coating acts as a barrier layer, preventing the diffusion of metallic impurities in the silicon thin film during the laser annealing. An energy density threshold of 0.3 J cm−2, necessary for surface melting and crystallization of the amorphous silicon, was predicted by a numerical simulation of laser-induced phase transitions and witnessed by Raman analysis. Beyond this fluence, the melt depth increases with the intensification of energy density. A complete crystallization of the layer is achieved for an energy density of 0.9 J cm−2. Scanning electron microscopy unveils the nanostructuring of the silicon after laser irradiation, while cross-sectional transmission electron microscopy reveals the crystallites’ columnar growth.

1A2-A09 直径30μmのタングステン中空マイクロニードルの作製(バイオミメティクス・バイオメカトロニクス(2))

Aiming at the use in low-invasive medical treatments, a tungsten hollow needle was fabricated by electrochemically etching a thin wire, the diameter of which is 30 μm, achieving an ultra-thin hollow needle equal to the labrum of mosquito stinger. Sharpness and smoothness of the tip are effective for easy insertion in the viewpoint of large stress concentration and small friction, respectively. An experiment of inserting the fabricated needle into an artificial skin of silicone rubber was carried out. The resistance force during insertion was much reduced due to its small size as mosquito's stinger. A hole was fabricated on the tungsten needle using excimer laser processing and electrochemical etching.