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1.
Laser removal of copper particles from silicon wafers using UV, visible and IR radiation 总被引:6,自引:0,他引:6
J.M. Lee C. Curran K.G. Watkins 《Applied Physics A: Materials Science & Processing》2001,73(2):219-224
Laser removal of small copper particles from silicon wafer surfaces was carried out using Nd:YAG laser radiation from near-infrared
(1064 nm) through visible (532 nm) to ultraviolet (266 nm). It has been found that both 266 nm and 532 nm are successful in
removing the particles from the surface whereas 1064 nm was shown to be ineffective in the removal of particles. The damage-threshold
laser fluence at 266 nm was much higher than other wavelengths which provides a much wider regime for safe cleaning of the
surface without causing any substrate damage. The cleaning efficiency was increased with a shorter wavelength. The effect
of laser wavelength in the removal process is discussed by considering the adhesion force of the particle on the surface and
the laser-induced cleaning forces for the three wavelengths.
Received: 31 May 2000 / Accepted: 14 July 2000 / Published online: 20 June 2001 相似文献
2.
This paper is to investigate the mechanisms of micro-scale particle removal by surface wave, which was induced by a short pulse laser in a cleaning process. The authors analyzed the adhesive forces of particles on substrate surface and the clearance force produced by surface wave in laser cleaning. The physical model of particle removal by laser-induced surface wave was established to predict the removal area and the processing conditions of laser cleaning. In this research, a KrF excimer laser was applied to irradiate 304 stainless steel specimen distributed with copper particles to generate surface wave for copper particle removal. Considering that a time-varying and uniformly distributed heat source irradiates on material surface with thermao-elastic behavior, the displacement and acceleration of substrate induced by a pulsed laser were solved by an uncoupled thermal–mechanical analysis based on the finite element method. The processing parameters such as laser energy, laser spot size are discussed, respectively. A series of laser cleaning experiments were designed to compare with computation results. The results show that the removal area by surface wave beyond the laser spot increases with the laser energy and that, the surface acceleration decreases with the increase of the laser spot size. 相似文献
3.
Acoustic expressions have been derived for the thermal expansion of substrate surfaces due to irradiation by an exponential laser pulse. The result of acoustic effects on three substrates (silicon, glass and silica) with different absorptions has been calculated.It has been shown that for substrates having relatively low absorptions, like silica and glass, acoustic considerations substantially reduce thermal expansion of the substrate caused by irradiation by nanosecond laser pulses relative to a quasi-static expansion model. In particular, the expansion of the substrate occurs over a much longer time frame than when the quasi-static approximation holds. Consequently, acceleration of the substrate surface is greatly reduced and laser cleaning threshold fluences for particle removal are increased.The predictions of the model of Arnold et al. when developed for acoustic considerations give reasonable agreement with experimentally found threshold fluences for alumina particles on silica and glass substrates although it underestimates the ratio of the threshold cleaning fluences of silica and glass. This could be due to the model underestimating the contribution of surface expansion to the laser cleaning process. The influence of multiple reflections in the substrate and departure from one dimensionality in the heat conduction on the threshold fluence was found to be insignificant. Thermal contact between the particle and the substrate was also found to have little effect on laser cleaning threshold fluences. Another mechanism that may enhance surface expansion is the 3D focussing of radiation by the particles. PACS 42.62.Cf; 81.65.Cf; 42.55.Lt 相似文献
4.
Multimode Nd:YAG pulse laser was applied to remove micron and submicron particles by vaporizing a thin paint film pre-coated on super-smooth optical substrate surface. By analyzing the poor absorption of the optical glass substrate to the irradiative Nd:YAG pulse laser, the removal mechanism of contaminated colloidal particles from the super-smooth surface through vaporization of a volatile solid film is described. A limit analysis was proposed to determine the lower and the upper threshold of laser fluence for cleaning the SiO2 contaminants from super-smooth K8 optical substrate. Relevant experiments on laser cleaning of micron-polishing particles from super-smooth K8 optical substrate confirmed the usefulness of this method in assisting the selection of effective cleaning fluence for accomplishing high cleanliness, which was in a range of 80–90% of the predicted upper threshold. 相似文献
5.
S. Pleasants B.S. Luk’yanchuk D.M. Kane 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1595-1598
A three-dimensional model for laser cleaning of spherical, transparent particles on low-absorbing substrates has been developed. It takes into account near-field focussing of the laser radiation by the particles. The intensity distribution under a particle was found using Mie theory together with the geometrical optics approximation. This permits the estimation of the beam width at the substrate surface and the focal distance of the radiation coming from the spherical particle. These parameters are used to find the distribution of intensity within the low-absorbing substrate from the formula for a focussed Gaussian beam. This is in contrast with most other models of laser cleaning, which assume that all absorption occurs at the surface of the substrate. The energy criterion was used to calculate the threshold fluence. The model predicts threshold fluences of the order of 103 J/cm2 for silica spheres having a diameter of the order of a micron on silica substrates, assuming adhesion by van der Waals force. As this is well above the damage threshold for silica, it effectively predicts that laser cleaning of silica spheres from silica will be impossible. For glass slides the threshold fluence is predicted to be a factor of 10-4 times smaller than that for silica slides (about 0.1 J/cm2). This is due to the much higher absorption of glass compared to that of silica at 248 nm. PACS 42.62.Cf; 81.65.Cf 相似文献
6.
J. Graf B.S. Luk’yanchuk M. Mosbacher M.H. Hong C.T. Chong J. Boneberg P. Leiderer 《Applied Physics A: Materials Science & Processing》2007,88(2):227-230
In this paper a new laser-based technique for the removal of nanoparticles from silicon wafers, called matrix laser cleaning,
is introduced. In contrast to the already existing technique dry laser cleaning damages of the substrate can be avoided. Furthermore
no liquids are used, avoiding problems that occur, e.g. in steam laser cleaning and other wet cleaning techniques. We show
that damage free particle removal of polystyrene particles with diameters of at least down to 50 nm is possible with a cleaning
efficiency very close to 100% within a single shot experiment. Furthermore the cleaning threshold is independent of the particle
size.
PACS 64.70.Hz; 68.43.Vx; 81.65.Cf 相似文献
7.
We propose an experimental approach which allows the characterization of the dynamics of the ejected particles in dry laser cleaning. Submicron silica particles on silicon substrates were illuminated by single nanosecond laser pulses at fluences which lead to particle removal. Time- and space-resolved scattered signal detection was demonstrated as a suitable technique to perform time-of-flight analyses of the ejected particles. The determination of the resulting detachment velocity at the particle removal threshold fluence contributes to a better understanding of mechanisms involved in dry laser cleaning. In particular, the present study evidences that the removal efficiency of the laser process is not based on the thermal expansion of materials. PACS 42.62.b; 42.15.Eq 相似文献
8.
F. Lang M. Mosbacher P. Leiderer 《Applied Physics A: Materials Science & Processing》2003,77(1):117-123
The removal of particles from commercial silicon wafers by Steam Laser Cleaning was examined. Polystyrene colloids were used
as model contaminants due to their well defined size and shape. In contrast to previous studies, where the experimental conditions
on the surface were only roughly determined, special care was taken to control the amount of liquid applied to the surface.
We report measurements of the cleaning threshold for different particle sizes. The comparability of the results was ensured
by the reproducible conditions on the surface. Moreover, we studied the influence of different liquid film thicknesses on
the cleaning process. Investigations of laser induced liquid evaporation showed that the cleaning threshold coincides with
the fluence necessary for the onset of explosive vaporization. After particle removal, the surface was examined with an atomic
force microscope. These investigations demonstrated that near field enhancement may cause defects on the nm-scale, but also
showed that Steam Laser Cleaning possesses the capability of achieving damage-free removal for a large range of different
particle sizes.
Received: 14 January 2003 / Accepted: 16 January 2003 / Published online: 28 March 2003
RID="*"
ID="*"Corresponding author. Fax: +49-7531/88-3127, E-mail: florian.lang@uni-konstanz.de 相似文献
9.
M. Mosbacher V. Dobler J. Boneberg P. Leiderer 《Applied Physics A: Materials Science & Processing》2000,70(6):669-672
The efficiency of the "steam laser cleaning" process is examined. For the investigation of the physics of particle removal from the particularly interesting surface of silicon we have deposited well-characterized spherical polymer and silica particles of different diameters ranging from several tens to hundreds of nanometers on commercial wafers. As a result of our systematic study we observe a sharp threshold of the steam cleaning process at 110 mJ/cm2 (5=532 nm, FWHM=7 ns) which is independent of the size (for particles with diameters as small as 60 nm) and material of the particles. An efficiency above 90% after 20 cleaning steps is reached at a laser fluence of 170 mJ/cm2. Experiments with irregularly shaped alumina particles exhibit the same threshold as for spherical particles. 相似文献
10.
Y.F. Lu W.D. Song K.D. Ye M.H. Hong D.M. Liu D.S.H. Chan T.S. Low 《Applied Surface Science》1997,120(3-4):317-322
Pulsed laser cleaning was demonstrated to be an efficient way for removing submicron particles from the nickel-phosphorus (NiP) surface both experimentally and theoretically. Experimentally, it is found that using KrF excimer laser with a pulse width of 23 ns the cleaning threshold is about 20 mJ / cm2 for removing quartz particles from the NiP surface and laser cleaning efficiency increases rapidly with increasing laser fluence. The theoretical analysis shows that the peak cleaning force (per unit area) is larger than the adhesion force (per unit area) for submicron quartz particles on the NiP surface when it is irradiated by excimer laser with a fluence above 10 mJ / cm2. Therefore, it is possible to remove submicron quartz particles from NiP surfaces by laser irradiation. The difference between the cleaning force (per unit area) and the adhesion force (per unit area) increases with increasing laser fluence, leading to a higher cleaning efficency for quartz particles on the NiP surface. 相似文献
11.
D.J. Hwang N. Misra C.P. Grigoropoulos A.M. Minor S.S. Mao 《Applied Physics A: Materials Science & Processing》2008,91(2):219-222
Lasers have proved to be effective tools for material processing at the micron and nanometer scales. In particular, laser
interaction with nanostructures offers the unique advantage of highly localized excitation and heating. In this study, a short-pulsed
laser beam is coupled to a scanning electron microscope, without disturbing the microscopy function, in order to study in
situ laser cleaning of individual submicron particles from a silicon substrate. The substrate conditions before and after
particle removal were inspected by electron microscopy. The mechanisms of particle removal and the underlying dynamic coupling
of the laser radiation associated with particle cleaning are investigated.
PACS 42.62.Cf; 42.82.Gw; 81.65.Cf; 07.78.+s 相似文献
12.
KrF excimer laser dry and steam cleaning of silicon surfaces with metallic particulate contaminants 总被引:3,自引:0,他引:3
P. Neves M. Arronte R. Vilar A.M. Botelho do Rego 《Applied Physics A: Materials Science & Processing》2002,74(2):191-199
KrF excimer laser-assisted dry and steam cleaning of single-crystal silicon wafers contaminated with three different types
of metallic particles was studied. The laser fluence used was 0.3 J/cm2. In the dry process, for samples cleaned with 100 laser pulses the cleaning efficiency was 91, 71 and 59% for Au, Cu and
W particles, respectively, whilst in steam cleaning the efficiency is about 100% after 5 laser pulses, independently of the
type of contaminant.
The effects of laser irradiation on the Si surface are investigated by scanning electron microscopy (SEM), X-ray photoelectron
spectroscopy (XPS) and atomic force microscopy (AFM). Laser processing at 0.3 J/cm2 does not deteriorate the Si-wafer surface, either in dry or steam cleaning. However, the measured XPS intensity coming from
the metallic component is greater on the cleaned surfaces than in the initial condition. Quantification of the XPS results,
assuming a stratified overlayer model for the detected species and accounting for the presence of the metallic particles on
the surface, showed that the obtained results can be explained by the formation of a fractional metallic monolayer on the
cleaned surfaces, due to partial vaporisation of small particles initially present on the sample surface. This contamination
of the substrate could be considered excessive for some applications and it shows that the process requires careful optimisation
for the required efficiency to be achieved without degradation of the substrate.
Received: 14 January 2001 / Accepted: 19 February 2001 / Published online: 20 June 2001 相似文献
13.
Conditions for laser-induced plasma to effectively remove nano-particles on silicon surfaces
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Particles can be removed from a silicon surface by means of irradiation and a laser plasma shock wave.The particles and silicon are heated by the irradiation and they will expand differently due to their different expansion coefficients,making the particles easier to be removed.Laser plasma can ionize and even vaporize particles more significantly than an incident laser and,therefore,it can remove the particles more efficiently.The laser plasma shock wave plays a dominant role in removing particles,which is attributed to its strong burst force.The pressure of the laser plasma shock wave is determined by the laser pulse energy and the gap between the focus of laser and substrate surface.In order to obtain the working conditions for particle removal,the removal mechanism,as well as the temporal and spatial characteristics of velocity,propagation distance and pressure of shock wave have been researched.On the basis of our results,the conditions for nano-particle removal are achieved. 相似文献
14.
Aniruddha Kumar J.P. NilayaD.J. Biswas R.B. BhattMohd. Afzal J.P. PanakkalH.S. Kamath 《Applied Surface Science》2011,257(16):7263-7267
Pulsed laser assisted removal of uranium dioxide and thorium dioxide particulates from stainless steel surface have been studied using a TEA CO2 laser. Decontamination efficiency is measured as a function of laser fluence and number of pulses. Threshold fluence for the removal of UO2 particulates has been found to be lower than that required for the removal ThO2 particulates. Usage of a ZnSe substrate, that is transparent to the laser wavelength used here, enabled us to decouple the cleaning effect arising out of absorption in the particulates from that in the substrate and has contributed towards understanding the mechanism responsible for cleaning. The experimental observations are also corroborated by simple theoretical calculations. 相似文献
15.
A fluence advantage was achieved in dry/damp laser cleaning by reduction of the laser beam dimensions. 0.1 m Al2O3 particles were removed from glass slides using a KrF excimer laser (248 nm). As the width of the rectangular beam was reduced, a decrease in the threshold fluence required for particle removal was observed. Modelling based on the simplified thermal–mechanical response of the substrate and particle to the laser pulse does not describe the experimental results presented here. The case of dynamic expansion must be further considered, but it is believed that other mechanisms are involved in a full explanation. PACS 42.62.Cf 相似文献
16.
A.M. Chen 《Applied Surface Science》2010,257(5):1678-1683
The heating processes of the single-layer gold thin film and the two-layer film assembly of gold padded with other metal (silver, copper and nickel) irradiated by femtosecond laser pulse are studied by the two-temperature model. It is found that the substrate metal can change energy transport, which is corresponding to the temperature changing process, and the thermal equilibrium time. Compared with the single-layer gold film at the same laser fluence, the two-layer film structure can change the damage threshold of the gold surface. Our results indicate that we can maximize the damage threshold of the gold film surface by altering the thickness ratio of the gold layer and the substrate layer in the two-layer film assembly. 相似文献
17.
Yayun Ye Xiaodong YuanXia Xiang Wei DaiMeng Chen Xinxiang MiaoHaibing Lv Haijun WangWanguo Zheng 《Optics and Lasers in Engineering》2011,49(4):536-541
A Nd:YAG laser (1064 nm) induces optical breakdown of the airborne above the gold-coated K9 glass surface and the created shockwave removes the SiO2 particles contaminated on the gold films. The laser cleaning efficiency has been characterized by optical microscopy, dark field imaging, ultraviolet-visible-near infrared spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and the Image-pro software. The relationships between removal ratio and particle position and laser gap distance have been studied in the case of single pulse laser cleaning. The results show that the 1064 nm laser induced plasma shockwave can effectively remove the SiO2 particles. The removal ratio can reach above 90%. The effects of particle position and laser gap distance on the cleaning efficiency are simulated for the single pulse laser cleaning. The simulated results are consistent with the experimental ones. 相似文献
18.
19.
An energy model to explain particle removal mechanism has been developed. This model is based on a detailed investigation
of contact deformation of a particle on a solid surface, as well as particle motion during the process of substrate surface
expansion under uniform laser irradiation. Calculation results show that small particles mainly gain kinetic energy during
pulsed laser irradiation, whereas large particles mainly gain elastic deforming potential energy. The particle removal condition
is derived from the viewpoint of energy. The relationship of particle removal efficiency with laser fluence and particle size
is discussed. Theoretical results are compared with experimental results.
Received: 30 July 1998 / Accepted: 14 December 1998 / Published online: 17 March 1999 相似文献
20.
D. Eversole B. Luk’yanchuk A. Ben-Yakar 《Applied Physics A: Materials Science & Processing》2007,89(2):283-291
We present the fabrication of nanostructures ablated on silicon(100) by the plasmonic scattering of 780 nm, 220 fs laser pulses
in the near-field of gold nanospheres. We take advantage of the enhanced plasmonic scattering of ultrashort laser light in
the particle near-field to ablate well-defined nanocraters. Gold nanospheres of 150 nm diameter are deposited onto a silicon
surface and irradiated with a single laser pulse. We studied the effect of laser polarization on the morphology of ablated
nanostructures and estimated the minimum fluence for plasmonic nanoablation. When the polarization of the incident radiation
is directed at a 45° angle into the substrate surface, a near-field enhancement of 23.1±7.6 is measured, reducing the required
silicon ablation fluence from 191±14 mJ/cm2 to 8.2±2.9 mJ/cm2. Enhancements are also measured for laser polarizations parallel to the substrate surface when the substrate is angled 0°
and 45° to the incident irradiation, giving enhancements of 6.9±0.6 and 4.1±1.3, respectively. Generated nanocrater morphologies
show a direct imprint of the particle dipolar scattering region, as predicted in our theoretical calculations. The measured
near-field enhancement values agree well with the maximum field enhancements obtained in our calculations. The agreement between
theory and measurements supports that the nanocraters are indeed formed by the enhanced plasmonic scattering in the near-field
of the nanoparticles.
PACS 42.62.-b; 52.38.Mf; 81.65.Cf; 81.16.-c; 78.67.Bf 相似文献