Papers by Keyword: Laser Cleaning

Abstract: For EUV lithography, a reflective mask is essential because of use of the strong energy, wavelength of 13.5 nm. The EUV mask consists of multi-layered, multi-material structure and is susceptible to various contaminants. Since EUV lithography process should be used in a high vacuum environment, an electrostatic chuck (ESC) is used to fix or hold the EUV mask using electrostatic force. In general, in order to use ESC chuck, it needs a thin conductive layer (CrN layer) on the backside. However, the contact points of the electrostatic pin chuck can make exfoliation of conductive CrN layer producing CrN particles. If these particles are present on the backside of the mask, CD or DOF may be affected during EUV exposure. The 1 μm particle can leads to a gap radius of 42mm [4]. Moreover, these backside particles may travel to the front side. Therefore, backside cleaning should be performed to remove particles from the mask backside surface.

Abstract: In this work, nanomaterials were used as consolidants and protective layers for artistic stones. Synthetized nanocomposites were applied on marble and their performances as protective and water repellent coating were characterized. For the preparation of the novel nanocomposites, SiO₂ and TiO₂ nanoparticles were synthesized by laser pyrolysis and were dispersed in acrylic polymer and silicon-based resin. To evaluate the retreatability of water repellent treatments, the capability of laser to remove protective layers was explored. Laser cleaning tests with different working parameters have been carried out to optimize the effectiveness of the process. The effects of laser treatments on stone surfaces and on the applied nanocomposites were estimated by using confocal optical microscopy and Laser-Induced Fluorescence (LIF).

Abstract: This work aims to obtain the well-implemented laser cleaning to remove polypropylene (PP) contamination of sizes ragne 10-60 µm on magnetic head slider by excimer laser at 248 nm. The finite element: FEM [1] simulations shows non-destructive cleaning at laser fluence of 100mJ/cm². The experiment shows that laser fluence is non-destructive at 70mJ/cm² and can remove 15-40% of polypropylene (PP) contamination.

Abstract: Nowadays, hard disk drives (HDD) technology are being developed continuously in order to increase the capacity, and reduce the size of HDD to meet user requirements. To increase the capacity which is equivalent to increasing read/write ability, the flying clearance must be reduced. Current new HDD models show that the fly height is lower than 0.3 μm. If the height of a particle or contamination is higher than 0.3 μm, the magnetic head will scratch the magnetic disk surface. However the process of cleaning in the HDD industry cannot remove particles with size smaller than 0.3 μm [1]. Therefore laser cleaning is selected first because this method can remove small particles [2]. and it does not damage the magnetic head. This research compares the range of temperature needed for cleaning the magnetic head between two types of heat source’s profile. The technique used is the heat transfer by finite element: FEM[3]. This technique provides an important factor of the laser cleaning method that increases the efficiency of particle removal. It is also a non-destructive method for cleaning the surface of the magnetic head slider.

Abstract: Laser cleaning is a non-contact, green and environmental cleaning method, which can effectively remove particulate contaminations of sizes as small as 0.1 μm without damage to the optics. But most laser cleaning devices are large and heavy, also expensive due to using large lasers such as CO2 laser, YAG Laser etc. In this work a low power LD was tried to clean fingerprint and dust contaminated on the surface of the attenuator glasses plates. In the laser cleaning experiment with low power diode the fingerprint grease can be efficient to be cleaned, but there is no evident effect for cleaning inorganic dust. The cleaning different degree of fingerprint contaminations was investigated at the variable laser parameters, including laser power and irradiation time. An optical microscope was used to analyze the cleaning effect. The results show that low power LD can effectively remove the fingerprint on the surface of absorptive-type attenuator glass plates. On the premise that the attenuator optics glasses are not damaged, the cleaning area increases with the increase of radiation time and laser power. The cleaning area doesn't change much with the variation of laser frequency when the other parameters are the same.

Abstract: The use of high power laser technology in the cleaning and dressing of grinding wheels has been the subject of several research projects worldwide and over the last 30 years. Several projects have reported beneficial outcomes however the process has not been implemented in production. The arrival of fibre lasers may provide a viable laser source for cleaning, and ultimately dressing, of wheels. This paper reports on some preliminary data confirming this potential and that supports the need for further research effort.

Abstract: With the rapid development of modern optics and correlative science and technology, hard-brittle materials such as optical glass, optical crystal and glass ceramic have very important applications in the fields of military, space and aviation, electronics and so on. It is of great importance to research optical machining method for hard-brittle materials for the development of science and technology. Different kinds of ultra precision machining methods have been developed to meet different industry requirement. Such as chemical mechanical polishing, precession polishing and magnetorheological finishing, etc. Under most conditions the optical surface after ultra precision machining would have certain contaminant particles and this would affect its working ability in future use. Formerly the polished workpiece is cleaned by flowing water or ultrasonic cleaning and the contaminant particles couldn’t be totally removed. Laser cleaning is brought forward in this paper and good results could be anticipated.

Abstract: Magnetorheological finishing (MRF) is a novel precision optical machining technology. Owing to its flexible finishing process, MRF can eliminate subsurface damage, smooth rms micro roughness and correct surface figure errors. Through proper designing of numerical control, sphere and asphere optics can be machined by magnetorheological finishing with high quality. Owing to it’s excellence in optical manufacturing, MRF has gained more and more application in industry. Under most conditions the optical surface after MRF would have certain contaminant particles and this would affect its working ability in future use. Formerly the polished workpiece is cleaned by flowing water or ultrasonic cleaning and the contaminat particles couldn’t be totally removed. Laser cleaning is brought forward in this paper and good results could be anticipated.

Abstract: A new dry cleaning methodology named laser shock cleaning and optical inspection technique has been applied not only to remove the particles from the surfaces of image sensors but also to inspect the surfaces automatically before or after the cleaning. In the packaging of CMOS and CCD image sensing modules, the particles generated during the assembly process should be removed from the surfaces of image sensors in order to ensure clear image as well as to enhance the yield. The different kinds of particles were removed from the surfaces by the laser shock cleaning technique which utilizes the airborne shock wave induced by intense laser pulse. For the quantitative evaluation of cleaning performance, number, shape and size of the particles on the surfaces of image sensors were measured by vision inspection technique before and after cleaning. It was found that most particles on the surfaces were successfully removed after the treatment of laser-induced shock waves. The average removal efficiency of the particles was over 95 %. It is interestingly found that the remaining particles after the cleaning are based on organics, which are probably attached during the bonding process.