紫外激光对触摸屏产品中不可视区域刻蚀实验研究

采用紫外激光对触摸屏产品中不可视区域进行刻蚀分析,探究了紫外激光刻蚀原理,讨论了银浆薄膜激光刻蚀与传统印刷工艺异同点,并在此基础上完成一套紫外激光刻蚀系统方案的设计和建造。实验结果表明,选用波长为355nm的紫外激光器,当激光器功率为10W,重复频率100kHz,刻蚀速度为1500mm/s,刻蚀次数1次时,薄膜被完全刻蚀,最终获得功能良好的银浆线路。经测试后发现,所刻蚀后银浆线条平直而光滑,边缘热影响区域较小,最小刻蚀线宽可以达到10μm,基板未受到损伤;与传统印刷工艺相比较,简化了工艺步骤,产品良品率得到提升,是一种无排放的绿色环保先进的刻蚀工艺。     

Variable linewidth high-power TEA CO2 laser

A variable linewidth high-power TEA CO2 laser, utilizing a multiple-prism beam expander in conjunction with a Littrow-mounted grating, is described. Linewidths of approximately 250-MHz (FWHM) at a total output energy exceeding 250 mJ have been obtained at the P20 (00 degrees 1-10 degrees 0), lambda = 10.59-microm line. Laser linewidths can be varied continuously in the 250-650-MHz range for a corresponding change in output energy from 250 to 400 mJ. The present frequency selectivity method, which employs ZnSe prisms, can be applied directly to considerably higher-power CO2 lasers.     

Deep reactive ion etching and focused ion beam combination for nanotip fabrication

We have studied the fabrication of high-aspect ratio silicon tips by a combination of deep reactive ion etching and focused ion beam. The reactive ion etching is used to obtain so-called “rocket tips” which can be fabricated with a high aspect ratio. The rocket tips are further processed by using a focused ion beam to obtain nanotips at their apex. Typical results obtained are nanotips with a basis radius of 200 nm and a height of 2.5 μm, with an apex radius of 5 nm, located on top of a 3 μm wide and 9 μm high silicon column. The process would allow however obtaining column heights of several tens of microns.     

Etching processes of transparent carbon nanotube thin films using laser technologies

Carbon nanotubes (CNTs) have potential as a transparent conductive material with good mechanical and electrical properties. However, carbon nanotube thin film deposition and etching processes are very difficult to pattern the electrode. In this study, transparent CNT film with a binder is coated on a PET flexible substrate. The transmittance and sheet resistance of carbon nanotube film are 84% and 1000 Ω/□, respectively. The etching process of carbon nanotube film on flexible substrates was investigated using 355 nm and 1064 nm laser sources. Experimental results show that carbon nanotube film can be ablated using laser technology. With the 355 nm UV laser, the minimum etched line width was 20 μm with a low amount of recast material of the ablated sections. The optimal conditions of laser ablation were determined for carbon nanotube film.     

One Step Lithography of Polypyrrole

Large areas of polypyrrole (PPy) thin films deposited onto inert polymeric substrates are structured by direct laser interference patterning (DLIP). Several square millimeter areas could be produced with one single (10 ns) pulse, at room temperature and atmospheric pressure. Nanometric arrays of lines (>600 nm) or grids of PPy deposited on dielectric polymers polypropilene or polypirrol (PP or PE) are fabricated by DLIP at 355 nm. The period of the lines structures, measured by white light interferometry (WLI), is 3.5 µm. Regular structures are analyzed using scanning electron microscope (SEM) and a focus ion beam (FIB) tomography. It is shown that only the PPy film is structured while the PP or PE substrate remains unaltered. Fourier transform infrared spectroscopy (FTIR) and UV‐vis spectroscopy, permit to ensure that PPy chemical structure remains unaltered after the structuration process. The width of PPy lines can be tailored by controlling the fluence of the laser beam. Contact angle measurement shows that the wettability is affected by the structuring, making the surface more hydrophobic. The structuring technique seems to be suitable for the fabrication of PPy regular structures over various substrates.     

Optical parametric properties of ultraviolet-pumped cesium lithium borate crystals

We report the optical parametric properties of cesium lithium borate (CLBO) crystals pumped by UV radiation of the fourth-harmonic generation at 266 nm and the third-harmonic generation at 355 nm of a picosecond Nd:YAG laser. A special optical design was used to avoid damage to the optical elements by the UV-pumped beam at 266 nm. The optical parametric generator (OPG)/optical parametric amplifier (OPA) of the 266-nm-pumped CLBO covers the tuning range from 347 nm in the UV to 1137 nm in the near IR. The 355-nm-pumped CLBO OPG/OPA, on the other hand, is tunable from 447 to 1725 nm. The experimental tuning curves for each CLBO OPG/OPA were measured and compared with the theoretical tuning curves. With a double-pass OPG configuration and a pumping intensity of approximately 6 GW/cm2, the maximum conversion efficiency, including both the signal and the idler, was approximately 11% for the 266-nm-pumped CLBO and is greater than 16% for the 355-nm-pumped CLBO without taking into account the surface losses from the uncoated elements. The bandwidth of this double-pass CLBO OPG at various wavelengths was measured and compared with other optical parametric systems. Because of the small angular dispersion of CLBO, the bandwidth of the OPG and OPA systems is exceptionally narrow, especially for the 266-nm-pumped system. Without the use of any dispersion element, the bandwidth of the 266-nm-pumped system can be as narrow as 0.22 nm at wavelengths far from the degenerate point. Comparison between the experimental bandwidth and the theoretical calculation shows that the bandwidth of the UV-pumped CLBO OPG/OPA is limited mainly by the divergence of the pump beam.     

Cavity ring-down spectroscopy for detection in liquid chromatography: extension to tunable sources and ultraviolet wavelengths

In earlier studies, it was demonstrated that the sensitivity of absorbance detection in liquid chromatography (LC) can be improved significantly by using cavity ring-down spectroscopy (CRDS). Thus far, CRDS experiments have been performed using visible laser light at fixed standard wavelengths, such as 532 nm. However, since by far most compounds of analytical interest absorb in the ultraviolet (UV), it is of utmost importance to develop UV-CRDS. In this study, as a first step towards the deep-UV region, LC separations with CRDS detection (using a previously described liquid-only cavity flow cell) at 457 and 355 nm are reported for standard mixtures of dyes and nitro-polyaromatic hydrocarbons (nitro-PAHs), respectively. For the measurements in the blue range a home-built optical parametric oscillator (OPO) system, tunable between 425 and 478 nm, was used, achieving a baseline noise of 2.7 x 10(-6) A.U. at 457 nm, improving upon the sensitivity of conventional absorbance detection (typically around 10(-4) A.U.). An enhancement of the sensitivity can be seen at 355 nm as well, but the improvement of the baseline noise (1.3 x 10(-5) A.U.) is much less pronounced. The sensitivity at 355 nm is limited by the quality of the UV-CRDS mirrors that are currently available: whereas the ring-down times as obtained at 457 nm are around 70-80 ns for the eluent, they are only 20-25 ns at 355 nm. Critical laser characteristics for LC-CRDS measurements, such as pulse length and mode structure, are given and prospects for going to shorter wavelengths are discussed.     

Narrow linewidth templates for nanoimprint lithography utilizing conformal deposition

Nanoimprint lithography has the potential to cost efficiently realize patterns with extremely narrow linewidth over a large area. A significant challenge to achieving this target is the fabrication of nanoimprint templates. The cost and writing time of conventional electron beam lithography for direct writing of the templates rapidly increases as the patterned area increases and the linewidth decreases. We have developed a novel process for creating narrow linewidth nanopatterns. This process is based on conformal deposition of thin films on seed nanopatterns. We have demonstrated the process by fabricating nanosized loops and lines. The linewidth of the structures can be tuned precisely, and in our experiments it could be reduced to 20?nm. The closed loop structures are interesting, since this geometry is crucially important in many leading edge research fields such as negative refractive index materials, ultrahigh density memory applications and quantum rings. The fabricated template was subsequently used as a template in soft-stamp UV nanoimprint lithography to successfully replicate the structures in UV-curable resist.     

High-power tunable narrow-linewidth Ti:sapphire laser at repetition rate of 1 kHz

We report a high-power tunable narrow-bandwidth Ti:sapphire laser at a repetition rate of 1?kHz. The spectral linewidth of 0.4?pm with wavelength tuning range from 780?nm to 820?nm is obtained by a spectrum-compressing technique that consists of one grating and four fused silica prisms in the oscillator cavity. This narrow-bandwidth seed from the oscillator is further amplified to 6.5?W with pulse duration of 16?ns under the pumper power of 22?W. This high-power laser with narrow linewidth is candidate for isotope separation and accuracy spectrum analysis.     

Tunable kHz deep ultraviolet (193-210 nm) laser for Raman application

The performance characteristics of a kilohertz solid-state laser source for ultraviolet Raman spectroscopy are described. Deep ultraviolet (UV) excitation in the 193-210 nm region is provided by mixing of the fundamental and third harmonics of a Ti-sapphire laser, which is pumped by the second harmonic of a Q-Switched Nd-YLF laser. The combination of tunability, narrow linewidth, high average power, good stability, and kilohertz repetition rate makes this laser suitable for deep UV resonance Raman applications. The short pulse duration (approximately 20 ns) permits nanosecond time resolution in pump-probe applications. The low peak power and high data rate provide artifact-free spectra with a high signal-to-noise ratio. UV Raman cross-section and Raman excitation profiles are reported for gaseous O2 (relative to N), aqueous ClO4-, tyrosine, phenylalanine, tryptophan, histidine, and hemoglobin excited between 193 nm and 210 nm to illustrate laser performance.     

Laser Irradiation of Polymer-Doped Cryogenic Matrices

Interactions between intense (10¹⁹ photons/cm² per shot) UV laser light and doped ice matrices were studied by the Matrix-Assisted Pulsed Laser Evaporation (MAPLE) deposition technique. Water, isopropanol, acetone and toluene ice matrices have been used as hosts for the biotechnologically important polymer – polyethylene glycol (PEG). The polymer–matrix system was irradiated under vacuum conditions with high-intensity laser beam at 355 nm in the fluence range 2–10 J/cm². We have explored the ejection of material from the ices in terms of light absorption by the matrix and photochemical interactions between matrix and polymer molecules during the irradiation process. The transfer of polymer from the matrix to a substrate has been studied on the basis of deposition rates measured with a quartz crystal microbalance (QCM) and Fourier-Transform Infrared (FTIR) spectra recorded from the deposits.     

Anisotropic multi-step etching for large-area fabrication of surface microstructures on stainless steel to control thermal radiation

Abstract

Controlling the thermal radiation spectra of materials is one of the promising ways to advance energy system efficiency. It is well known that the thermal radiation spectrum can be controlled through the introduction of periodic surface microstructures. Herein, a method for the large-area fabrication of periodic microstructures based on multi-step wet etching is described. The method consists of three main steps, i.e., resist mask fabrication via photolithography, electrochemical wet etching, and side wall protection. Using this method, high-aspect micro-holes (0.82 aspect ratio) arrayed with hexagonal symmetry were fabricated on a stainless steel substrate. The conventional wet etching process method typically provides an aspect ratio of 0.3. The optical absorption peak attributed to the fabricated micro-hole array appeared at 0.8 μm, and the peak absorbance exceeded 0.8 for the micro-holes with a 0.82 aspect ratio. While argon plasma etching in a vacuum chamber was used in the present study for the formation of the protective layer, atmospheric plasma etching should be possible and will expand the applicability of this new method for the large-area fabrication of high-aspect materials.     

Sub-20 nm laser ablation for lithographic dry development

Pattern collapse of small or high aspect ratio lines during traditional wet development is a major challenge for miniaturization in nanolithography. Here we report on a new dry process which combines high resolution resist exposure with selective laser ablation to achieve high resolution with high aspect ratios. Using a low power 532?nm laser, we dry develop a normally negative tone methyl acetoxy calix(6)arene in positive tone to reveal sub-20?nm half-pitch features in a ～100?nm film at aspect ratios unattainable with conventional development with ablation time of 1-2?s per laser pixel (～600?nm diameter spot). We also demonstrate superior negative tone wet development by combining electron beam exposure with subsequent laser exposure at a non-ablative threshold that requires far less electron beam exposure doses than traditional wet development.     

Random lasing in a dye-doped polymer thin film waveguide deposited on a Si surface microstructured by femtosecond laser ablation

Random laser action with ~8 nm of bandwidth from a special waveguide structure is reported. The waveguide structure is composed of a layer of rhodamine 6G-doped PMMA film and a silicon substrate with a microstructured surface induced by a femtosecond laser. The silicon substrate featured two-dimensional island-like microstructures with average sizes ranging from 0.8 μm to 3 μm and average heights at about 0.7 μm. A red-shift of laser peak positions and decrease of threshold were observed with decreasing size of silicon surface microstructures. The spectra at different probe directions were also measured, and the results reveal that the waveguide laser action is strongly confined within ±10° from the direction of the edge. The lasing modes emitted from the edge of the waveguide are found to be mainly transverse electric-polarized. Our experiments demonstrate a promising method to achieve waveguide random lasers.     

长距离同轴度测量方法及实验

本文介绍了一种新型的自适应双频激光同轴度测量系统，该系统利用两个完全对称的渥拉斯顿棱镜，一个作为测量元件，另一个作为补偿元件，采用比相技术处理测量信号，因而测量元件可以暂时移出光路，能够进行同轴度的测量，系统的光学设计使激光光束的平衡和角漂不影响测量结果，对激光的漂移有自适应性，两束干涉光基本符合共光路原则，因而对大气湍流，空气扰动的影响具有更强的适应性，可用于长距离直线度，同轴度的测量。该系统与     

Single-frequency pulsed laser source with hybrid MOPA configuration

A unique approach with a hybrid master oscillator power amplifier configuration to obtain single-frequency, high-energy laser pulses at 1064 nm is presented. The setup consists of a single-frequency seed laser, a multistage fiber amplifier, and a four-pass crystal rod amplifier. Pulse energy of 10 mJ is obtained at the repetition rate of 100 Hz. The pulse width is about 110 ns with a transform-limited linewidth of 3.2 MHz. The M(2) factor of the output beam is about 1.5. To our knowledge, this is the first report of using a hybrid amplifier to obtain 10 mJ pulses with long pulse width and transform-limited linewidth.     

Coupling effect of multi-wavelength lasers in damage performance of beam splitters at 355 nm and 1064 nm

The coupling effect between a 355 nm laser and a 1064 nm laser in damage initiation and morphology formation was investigated on beam splitters. When extra 1064 nm pulse energy was low, 355 nm laser-induced damage thresholds (LIDTs) increased because of laser conditioning, and when 1064 nm pulse energy was high enough, 355 nm LIDTs decreased. Damage morphologies were also studied to explore the damage mechanism at respective wavelengths. For the entirely different electric field intensity distributions, 355 nm laser-induced damages were mainly from nanometer-sized absorbers at upper interfaces, while initiators for the 1064 nm laser were located at substrate-coating interface or substrate subsurface. Under simultaneous illumination, the sensitive defects were still the precursors, and damages also showed the representative damage characteristics induced by a single laser, namely, 355 nm laser-induced small pits and 1064 nm laser-induced large delamination. Further studies also showed that, although the 1064 nm laser fluence was kept unchanged, delamination area grew with the increase of pits, which were induced by the 355 nm laser. A possible mechanism was proposed to interpret the delamination area growth phenomenon.     

Periodic arrays of deep nanopores made in silicon with reactive ion etching and deep UV lithography

We report on the fabrication of periodic arrays of deep nanopores with high aspect ratios in crystalline silicon. The radii and pitches of the pores were defined in a chromium mask by means of deep UV scan and step technology. The pores were etched with a reactive ion etching process with SF(6), optimized for the formation of deep nanopores. We have realized structures with pitches between 440 and 750?nm, pore diameters between 310 and 515?nm, and depth to diameter aspect ratios up to 16. To the best of our knowledge, this is the highest aspect ratio ever reported for arrays of nanopores in silicon made with a reactive ion etching process. Our experimental results show that the etching rate of the nanopores is aspect-ratio-dependent, and is mostly influenced by the angular distribution of the etching ions. Furthermore we show both experimentally and theoretically that, for sub-micrometer structures, reducing the sidewall erosion is the best way to maximize the aspect ratio of the pores. Our structures have potential applications in chemical sensors, in the control of liquid wetting of surfaces, and as capacitors in high-frequency electronics. We demonstrate by means of optical reflectivity that our high-quality structures are very well suited as photonic crystals. Since the process studied is compatible with existing CMOS semiconductor fabrication, it allows for the incorporation of the etched arrays in silicon chips.     

标准硅球直径测量中的光路对准

针对标准单晶硅球直径精密测量的需要,本文在介绍标准硅球直径测量系统原理并分析其光路特点的基础上,根据建立的数学模型,对激光束斜入射标准板时产生的椭圆干涉图像进行了分析,并对不同入射角度时干涉环中心点带来的直径测量误差进行了研究.分析结果显示,在给定的实验条件下,当入射角为10~(-3) rad时,误差已达6.6nm.提出了一种精确调整光束垂直入射平板的方法,实验结果表明,此方法能够使光束入射角的调整优于10~(-5)rad,满足系统测量的要求.     

A systematic study of DRIE process for high aspect ratio microstructuring

Various MEMS devices like Accelerometers, Resonators, RF- Filters, Micropumps, Microvalves, Microdispensers and Microthrusters are produced by removing the bulk of the substrate materials. Fabrications of such Microsystems requires the ability to engineer precise three-dimensional structures in the silicon substrate. Fabrication of MEMS faces multiple technological challenges before it can become a commercially viable technology. One key fabrication process required is the deep silicon etching for forming high aspect ratio structures. There is an increasing interest in the use of dry plasma etching for this application because of its anisotropic etching behavior, high etch speed, good uniformity and profile control, high aspect ratio capabilities without having any undesired secondary effects i.e. RIE lags, Loading, microloading, loosing of anisotropic nature of etching as aspect ratio increases, micro-grass and even etch stalling. Developing a DRIE micro-machining process requires a thorough understanding of all plasma parameters, which can affect a silicon etching process and their use to suppress the secondary effects. In this paper our intention is to investigate the influence of etching gas flow, etching gas pressure, passivation gas pressure, ICP coil power, Platen power and etch and passivation time sequence on etch rate and side wall profile. Parameter ramping is a powerful technique used to achieve the requirements of high aspect ratio microstructures (HARMS) for MEMS applications by having high etch rate with good profile/CD control. The results presented here can be used to rationally vary processing parameters in order to meet the microstructural requirements for a particular application.