Excimer Laser Patterning Research Articles

Flexible SERS substrate for portable Raman analysis of biosamples

Recent development of Surface-Enhanced Raman Spectroscopy (SERS) as an extremely sensitive analytical method requires the introduction of flexible SERS substrate for express, out- doors measurements. Herein, we demonstrate an approach for creation of flexible SERS substrate, exhibiting high reproducibility and reliability of analytical results. The flexible SERS substrates are produced by the excimer laser patterning of thin polymer films, followed by the deposition of thin Au layer. The thickness of polymer films allows their further self-adhesion to a targeted surface. The proposed method allows the creation of macroscopically large plasmon-active area on the polymer film. The effectivity of SERS substrate was optimized by proper choice of the parameters of laser pattering, the thickness of flexible polymer film and amount of the deposited gold. The substrates were optimized using the typical SERS analyte - R6G. Suitability of the present substrate for the detection of bio-objects (yeast cell) was demonstrated too. All SERS measurements were performed with portable Raman spectrometers and the possibility of the implementation of created SERS substrate for rapid and unpretentious outdoor analysis was demonstrated.

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.

Surface analysis of the selective excimer laser patterning of a thin PEDOT:PSS film on flexible polymer films

Fast patterning of highly conductive polymers like PEDOT:PSS (poly (3,4-ethylene dioxythiophene): polystyrene sulfonate) with lasers can contribute to the development of industrial production of liquid crystal displays on polymer foils. In this article, the selective UV laser patterning of a PEDOT:PSS film on flexible polymer films is investigated. Based on their optical properties, three polymer films are investigated: polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) and cellulose triacetate (TAC). Ablation parameters for a 110nm PEDOT:PSS film on these polymer films are optimized. A detailed study of the crater depth, topography and surface composition are provided using optical profilometry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The electrical insulation of the lines is measured and correlated to the crater analyses for different laser settings. Finally, potential ablation parameters for each of the polymer films are derived.

AFM study of excimer laser patterning of block-copolymer: Creation of ordered hierarchical, hybrid, or recessed structures

We report fabrication of the varied range of hierarchical structures by combining bottom-up self-assembly of block copolymer poly(styrene-block-vinylpyridine) (PS-b-P4VP) with top-down excimer laser patterning method. Different procedures were tested, where laser treatment was applied before phase separation and after phase separation or phase separation and surface reconstruction. Laser treatment was performed using either polarized laser light with the aim to create periodical pattern on polymer surface or non-polarized light for preferential removing of polystyrene (PS) part from PS-b-P4VP. Additionally, dye was introduced into one part of block copolymer (P4VP) with the aim to modify its response to laser light. Resulting structures were analyzed by XPS, UV–vis and AFM techniques. Application of polarized laser light leads to creation of structures with hierarchical, recessed or hybrid geometries. Non-polarized laser beam allows pronouncing the block copolymer phase separated structure. Tuning the order of steps or individual step conditions enables the efficient reorientation of block-copolymer domain at large scale, fabrication of hierarchical, hybrid or recessed structures. The obtained structures can find potential applications in nanotechnology, photonics, plasmonics, information storage, optical devices, sensors and smart surfaces.

“Artificial” chirality induced in doped polymer by irradiation with circularly polarized excimer laser light

Creation of artificial optical response, which is determined by the materials geometry rather than chemical composition, is one of the main challenges of modern physics. In this paper application of large-area chiral excimer laser patterning for the creation of artificial chirality is described. Polymethylmethacrylate was doped with chromophore (Fast Red ITR) and this film was irradiated with circularly polarized KrF excimer laser beam. Surface morphology of pristine and treated samples was studied by confocal and AFM microscopy, absorption was studied by FTIR and VCD spectroscopies. It was initially proposed, that surface structure induced by rotationally polarized laser beam will have chiral nature and response. Actual experiments indicate that circularly polarized light induces the formation of many microscopic spirals or more complex structures on the polymer surface. Shape and density of the surface structures were determined by experimental conditions and in all cases the initially non-chiral doped PMMA becomes equivalent to the classical, optically active media. In particular, created structures gave rise to a photoinduced circular dichroism response, with the response being determined by experimental conditions. The resulting chiral structures show long-time stability and offer interesting possibility to manipulate the light polarization.

Surface Plasmon Polaritons on Silver Gratings for Optimal SERS Response

One of the most important obstacles for the application of surface enhanced Raman spectroscopy (SERS) is the poor reproducibility of SERS active substrates: SERS intensity can be varied from one substrate to another and moreover along the one substrate surface. Reproducible SERS substrate can be prepared through introduction of highly ordered metal array, where light focusing is achieved through excitation of surface plasmon-polaritons (SPPs). In this work, excimer laser patterning of poly(methyl methacrylate) followed by silver evaporation is proposed as an effective way for the creation of reproducible and effective surface plasmon-polaritons (SPP)-based SERS substrate. Detailed theoretical and experimental studies were performed to optimize structure parameter for effective SPP excitation. It was found that the narrow range of grating periodicity and metal thickness exist, where SPPs can be most efficiently excited. Despite the fact that SERS response was almost always achieved, the enhancement factor ...

Excimer laser patterning of PEDOT:PSS thin-films on flexible barrier foils: A surface analysis study

Selective laser patterning of thin organic films is an important aspect in the roll-to-roll production of organic electronic devices such as organic light emitting diodes (OLEDs). An excimer laser is well suited for the patterning and structuring of polymer thin films as their UV absorption is significant. Selective removal of a transparent conducting polymer PEDOT:PSS (poly(3,4-ethylene dioxythiophene):polystyrene sulfonate) on a multilayered (inorganic–organic–inorganic) barrier and a flexible PEN (polyethylene napthalate) substrate has been studied using a KrF excimer laser. The ablation craters were characterized with electron microscopy and profilometry. For the first time, chemical surface analysis of the patterned area was performed with Time-Of-Flight Static Secondary Ion Mass Spectrometry (TOF-S-SIMS), providing a detailed insight of the surface composition after laser ablation and plasma post-treatments.

Excimer laser reduction and patterning of graphite oxide

A successful approach and the operational parameters necessary for reduction of graphite oxide (GO) to multilayer graphene using 248nm excimer laser irradiation in both vacuum and ultrahigh purity N2 background environments is described. The utility of excimer laser reduction is demonstrated by production of simple line and logo patterns using standard microscale lithographic patterning strategies. Multilayer graphene formation is confirmed with Raman and X-ray photoelectron spectroscopies, and the morphology of the processed GO sample is evaluated with scanning electron microscopy. Four-point probe measurements of the excimer laser reduced GO indicate typical sheet resistances of ∼100–500Ω/sq, which is a significant improvement over other values reported in the literature for other laser-based GO reduction methods.

UV laser modification and selective ion-beam etching of amorphous vanadium pentoxide thin films

We present the results on excimer laser modification and patterning of amorphous vanadium pentoxide films. Wet positive resist-type and Ar ion-beam negative resist-type etching techniques were employed to develop UV-modified films. V2O5 films were found to possess sufficient resistivity compared to standard electronic materials thus to be promising masks for sub-micron lithog-raphy

Direct Patterning of Silicon Nitride Thin Film by Projection Photoablation for Fabricating Thin-Film Transistor Liquid Crystal Displays

The direct patterning of silicon nitride (SiNx) thin films on glass substrates using a KrF 248 nm excimer laser has been investigated. The direct laser patterning process offers a cost-effective alternative to wet- and dry-etch lithographies for the fabrication of thin-film transistor liquid crystal displays (TFT-LCDs). It is demonstrated that direct laser patterning can effectively pattern 200 nm SiNx thin films at the laser energy density of 1350 mJ/cm2. We can therefore reduce the cost and process time by using excimer laser patterning and eliminating the need for wet- and dry-etch processes.

UV Ultrafast Laser Processing using Phase Masks

Based on the combination of short pulse duration with short wavelength, UV ultrafast lasers provide unprecedented material processing quality. A high power UV ultrafast laser system comprises a Ti:sapphire front-end laser whose frequency tripled pulses are amplified in a UV excimer gain module. In this way, subpicosecond pulses are obtained at 248 nm with an average power of up to 10 W. Such pulses are ideally suited for the treatment of solid surfaces with sub-micron precision. A combination of diffractive optical masks with conventional imaging systems allows the generation of complex 2D structures with typical feature sizes of ∼ 200 nm on all materials including metals, semiconductors and dielectrics. A new technique for the fabrication of the phase masks or diffractive phase elements used in the experiments is based on excimer laser patterning of dielectric layers. Such phase masks feature a large processed area, high efficiency for VUV to NIR radiation and can be customized e.g. for perfect zero order suppression.

Excimer laser patterning of epitaxial YSZ films grown on silicon

Epitaxial yttria-stabilised zirconia (YSZ) films grown on Si(1 0 0) were irradiated by KrF excimer laser (248 nm wavelength, 34 ns pulse length). 50 μm wide squares were patterned by imaging a mask under mild irradiation conditions and applying a varying number of laser pulses. The resulting morphology and chemical composition were studied. By increasing the number of pulses, the morphology of the irradiated area evolved from a cracked film surface to a final structure with exposed silicon over most of the surface, but also with YSZ globules that could not be removed by additional pulses. Of particular interest when using laser patterning with a high lateral resolution is the possibilty of the exclusively localisation of the damage within the irradiated area. The damaged lateral zone beyond the spot border was less than 1 μm after irradiation with thousands of laser pulses, and only around a few tenths of after a few pulses. We also prepared arrays of tracks (20 μm wide, 5 μm separation) by moving and irradiating the sample in a step-and-repeat process. The separation between tracks is not altered and suitable for selective epitaxial growth of other films.

Micropatterning of BiSrCaCuO Thin Films Using Excimer Laser

Micropatterning of BiSrCaCuO(BSCCO) superconducting thin films has been successfully accomplished by using a pulsed KrF excimer laser with a wavelength of λ=248 nm and a duration of 25 ns. The optimum energy density of the laser was 0.36 Jcm -2 for etching of these films. For example, a superconducting microstructure of BSCCO film with nominally 3 μm wide and 2 μm long, showed no degradation in T c and J c . Excimer laser patterning technique yields reproducible patterning without any degradation of superconducting properties. The etching bordering and surface morphology was examined using an atomic force microscope.

Excimer laser patterning of superconducting BiSrCaCuO thin films

Micrometre-wide patterning of BiSrCaCuO (BSCCO) superconducting thin films has been successfully accomplished using a pulsed KrF excimer laser with a wavelength of and a duration of 25 ns. Etch depth as a function of the number of laser pulses was almost linear over a wide range of incident laser energy densities. For example, a superconducting microstructure of BSCCO film, nominally wide and long, showed no degradation in or . The excimer laser patterning technique yields reproducible patterning without any degradation of superconducting properties. The etching bordering and surface morphology were examined using an atomic force microscope.

Diamond device delineation via excimer laser patterning

Excimer lasers are high peak power gas lasers, commonly operating in the UV region of the electromagnetic spectrum, i.e. between 157 and 351 nm. They have been extensively applied to patterning and machining of high performance materials, such as polymers and fibre-reinforced composites. The use of high power, UV excimer lasers offers an alternative route for structure delineation in electronic device fabrication, by providing a resist-free, patterned processing capability. This is in contrast to conventional etching processes, such as wet chemical, reactive ion or plasma-assisted methods. The effect of excimer laser radiation on chemical-vapour-deposited diamond has been studied to find the optimum conditions for device patterning. The effect of chemical-vapour-deposited diamond film quality (amount of sp 3-bonded carbon) on the etch rates and laser processing parameters (power, pulse rate and wavelength) also have been examined. A tentative mechanism for the ablation of diamond has been proposed.

Mechanisms of dehydrogenation during ArF excimer laser patterning of plasma-deposited silicon nitride films

Using Fourier-transformed infrared spectroscopy, we show that pulsed ArF excimer laser irradiation of plasma-deposited silicon nitride films causes a large reduction in NH (∼100%) and SiH (∼50%) in the top ∼500 Å, and further show that this is responsible for the large suppression of the etch rate in buffered HF solution. Temperature rise calculations qualitatively predict the observed maximum falloff in etch rate and in SiH and NH concentration at the surface of the film. The observed reduction of the effect in thin films, which is due to the heat-sink effect of the underlying substrate, is also predicted. Both are strong indications that NH and SiH bonds are broken in a laser heating process. H2 has been detected as a product evolved during laser irradiation; however, most H2 remains trapped in the film.

Excimer laser patterning of high-T/sub c/ superconducting thin films of YBCO

The patterning by excimer laser ablative etching of thin superconducting films of YBCO on MgO and fused silica substrates which were fabricated by laser sputtering is discussed. The etch rate as a function of laser fluence, wavelength, and number of pulses has been investigated. Although etched film surfaces were found to be considerably smoother than annealed films, the laser etching itself was found not to be a totally thermal process. >