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Optical problems, related to the particle on the surface, i.e. optical resonance and near-field effects in laser cleaning are discussed. It is shown that the small transparent particle with size by the order of the wavelength may work as a lens in the near-field region. This permits to focus laser radiation into the area with the sizes, smaller than the radiation wavelength. It leads to 3D effects in surface heating and thermal deformation, which influences the mechanisms of the particle removal.

Laser processing has large potential in the packaging of integrated circuits (IC). It can be used in many applications such as laser cleaning of IC mold tools, laser deflash to remove mold flash form heat sinks and lead wires of IC packages, laser singulation of BGA and CSP, laser reflow of solder ball on GBA, laser marking on packages and on SI wafers. During the implementation of all these applications, laser parameters, material issues, throughput, yield, reliability and monitoring techniques have to b taken into account. Monitoring of laser-induced plasma and laser induced acoustic wave has been used to understand and to control the processes involved in these applications.

Pulsed laser ablation of mold compounds for IC packaging in air and with steam assistance is investigated. It is applied to decap IC packages and expose computer CPU dies for the device failure analyses. Compared with chemical decapping, the laser ablation has advantages of being fast speed, non- contact and dry processing. Laser ablation with the steam assistance results in higher ablation rate and wider ablated crater with much smoother surface morphology. It implies that the steam assisted laser ablation can achieve a faster and better quality laser processing. Audible acoustic wave and plasma optical signal diagnostics are also carried out to have a better understanding of the mechanisms behind. Light wavelength and laser fluence applied in the decapping are two important parameters. The 532 nm Nd:YAG laser decapping at a low laser fluence can achieve a large decapping area with a fine ablation profile. IC packages decapped by the laser ablation show good quality for the device failure analyses.

Effect of excimer laser irradiation at different fluences on Indium-Tin-Oxide films has been studied with the use of optical transmission, XRD, Mirco-Raman spectra and XPS. Surface modification at low fluence of 154mJ/cm 2 is observed to cause the increase of optical transmittance at initial several pulses of UV laser. At moderate fluence of 239mJ/cm 2 , UV laser irradiation results in apparent coloration and chemical compositional change on the ITO surface. XRD results show the grain size of ITO tends to decrease after irradiation. Novel features appear in Raman spectra, which involve the change of surface crystallinity and composition induced by UV laser irradiation. XPS analysis indicates peak shape of O bond is modified post irradiation and Sn/In ratio presents maximum corresponding to dark coloration. ITO films have also been patterned at high fluence of 1-2J/cm 2 using simple masks. The ablation rate on laser pulse demonstrates linear change. An alternative method for laser patterning is proposed by the combination of excimer laser coloration and visible laser patterning.

In this paper, we present a novel method of nanostructure fabrication using particle-enhanced near-field optical effect and lasers. For this purpose, spherical silica particles were deposited on a silicon surface. After laser illumination, hillocks with size of about 150 nm were obtained at the original position of the particles. The mechanism can be explained as the enhancement of light intensity near the contact area. Since the characteristic distance between particles and substrate is smaller than the radiation wavelength and the particle size is of the order of a wavelength, particle does not simply play the role of microfocusing lens as in far-field, but possess optical resonance effect in near-field. In our work, the light intensity on the surface under the spherical particle was calculated by solving the electromagnetic boundary problem 'particle on surface.'

Laser cleaning technology has been demonstrated to be an effective cleaning technique for removing particulate and film-type contaminants from solid surfaces in this paper. Dry and steam laser cleaning mechanisms and applications in semiconductor and disk drive industry will be addressed.

Using pulsed laser deposition (PLD), (001)-textured Nb-doped Pb (Zr0.52Ti0.48)O3 (PZT) films with highly restricted in-plane crystallographic alignments were successfully deposited on Si(001) wafers covered with amorphous SiO2. MgO and SrTiO3 (STO) films were used as buffer and seed layers, respectively, for growth of YBA2Cu3O7 (YBCO) and PZT layers. The YBCO layer can serve as a bottom electrode for activation of PZT films. Variations in the deposition conditions for the MgO films were found to play a key role in the subsequent deposition of the oriented PZT thin films. MgO films deposited at an O2 partial pressure of 200 mtorr, have a strong (100) texture, leading to subsequent deposition of PZT films with both a strong (100) texture and highly restricted in-plane orientations. Although the MgO and STO films show very strong crystallographic textures, their in-plane orientations are random. The restricted in-plane orientations were only observed in the YBCO and PZT films.

Laser Microprocessing, Data Storage Institute, Singapore 1 1 7608STO and subsequent YBCO thin films with different orientations have been grown on a single crystalMgO (100) substrate as well as a MgO on a 400nm amorphous Si02 covered Si (100) substrate usingpulsed laser deposition (PLD) technique. Cross-sectional transmission electron microscopy (TEM)showed an epitaxial growth of highly c-axis oriented YBCO(00l)/STO(100) on a single crystal MgO(100). TEM investigation on MgO/5i02 interface revealed a columnar growth of MgO film with acertain thin interlayer existing between 5i02 and MgO indicating interfacial reaction between 5102and MgO. Chemical reaction may be possible at the interface when films are hold at high temperaturebased on the calculation of Gibbs free energy. Auger electron spectroscopy (AES) showed that an up-hill diffusion of Ba from YBCO occured during deposition and post thermal treatment processes.Keywords: PLD, MgO, STO, YBCO, Epitaxial growth, Interface, Diffusion

Laser microprocessing has been extensively studies with applications in microelectronics and magnetic data storage. In addition to the fundamental aspects of laser materials interactions, we have investigated various possible applications of laser microprocessing in different areas. Laser cleaning has been studies systematically both theoretically and experimentally for dry surface cleaning and steam surface cleaning. This technology has been applied for cleaning magnetic head, magnetic sliders, suspension, laser mold cleaning and laser deflash for IC packages. Laser texturing and related processes such as laser bumping, laser tagging have been studied for magnetic recording applications. The future prospects of using laser microprocessing for applications in formation of ultrashallow (less than 50 nm) pn junction for next- generation MOS devices, laser generation of Si nanoparticles for quantum-dot flash memory, light emission devices and low cost and smart photonics devices will be addressed.Laser microprocessing has been extensively studies with applications in microelectronics and magnetic data storage. In addition to the fundamental aspects of laser materials interactions, we have investigated various possible applications of laser microprocessing in different areas. Laser cleaning has been studies systematically both theoretically and experimentally for dry surface cleaning and steam surface cleaning. This technology has been applied for cleaning magnetic head, magnetic sliders, suspension, laser mold cleaning and laser deflash for IC packages. Laser texturing and related processes such as laser bumping, laser tagging have been studied for magnetic recording applications. The future prospects of using laser microprocessing for applications in formation of ultrashallow (less than 50 nm) pn junction for next- generation MOS devices, laser generation of Si nanoparticles for quantum-dot flash m...

A method of laser scanning ablation for producing large area YBa2Cu3O7 superconducting films is presented. Uniformly thick, large area YBa2Cu3O7 superconducting films were obtained on 36‐mm‐diam (100) LaAlO3 substrates with a lens rotating radius of 9 mm. The Tc’s of the film center and edge were all 92 K and transition widths were less than 1 K. X‐ray diffraction studies showed complete c‐axis orientation of the films. The critical current density of 3.6×106 A/cm2 in zero field was measured at 77 K. A power law of voltage V versus current I of the YBa2Cu3O7 superconducting microbridge, V=1.363×10−32I11.224 49 was achieved.

To investigate the variation of neurotrophic factors expression in spinal cord and muscle after root avulsion of brachial plexus.Forty-eight Wistar rats were involved in this study and according to the observing time in 1st day, 1st week, 4th week, 8th week, and 12th week after avulsion, and the control, were divided into 6 groups. By immunohistochemical and hybridization in situ assays, the expression of nerve growth factor (NGF) on muscle, basic fibroblast growth factor(bFGF) and its mRNA on the neurons of corresponding spinal cord was detected. Computer image analysis system was used to calculate the result.After the root avulsion of brachial plexus occurred, expression of NGF increased and reached to the peak at the 1st day. It subsided subsequently but was still higher than normal control until the 12th week. While expression of bFGF and its mRNA increased in the neurons of spinal cord and reached to the peak at the 1st week. Then it dropped down and at the 12th week it turned lower than normal control.After root avulsion of brachial plexus, neurotrophic factors expression increase on target muscle and neurons of corresponding spinal cord. It maybe the autoregulation and may protect neuron and improve nerve regeneration.

The experimental analysis of dry laser cleaning efficiency is done for certified spherical particle (SiO2, 5.0, 2.5, 1.0 and 0.5 μm) from different substrates (Si, Ge and NiP). The influence of different options (laser wavelength, incident angle, substrate properties, i.e. type of material, surface roughness, etc.) on the cleaning efficiency is presented in addition to commonly analyzed options (cleaning efficiency versus laser fluence and particle size). Found laser cleaning efficiency demonstrates a great sensitivity to some of these options (e.g. laser wavelength, angle of incidence, etc.). Partially these effects can be explained within the frame of the Mie theory of scattering. Other effects (e.g. influence of roughness) can be explained along the more complex line, related to examination of the problem “particle on the surface” beyond the Mie theory. 0.5 μm spherical silica particles were placed on Silicon (100) substrate. After laser irradiation with a 248 nm KrF excimer laser, hillocks with size of about 100 nm were obtained at the original position of the particles. Mechanism of the formation of the sub-wavelength structures were investigated and found to be the near-field optical resonance effect induced by particles on surface. Theoretical prediction of the near-field light intensity distribution was presented, which was in agreement with the experimental result.

Laser directly writing of nanostrucrures on magnetic film surfaces with optical near field effects has been investigated. Spherical 0.99 m or 0.47 m silica particles were placed on Cr/CoCrPt multilayers. After laser illumination with an excimer laser for a single shot, pits were obtained at the original position of the particles using different laser fluences or particle size parameters. The mechanism of the formation of nanostructure pattern was discussed and found to be the near-field optical resonance effect induced by particles on the surface. A comparison with accurate theoretical calculations of near-field light intensity distribution showed good agreement with the experiment results. The method of particle enhanced laser irradiation allows the study of field enhancement effects as well as its potential applications for nanolithography.

Recently, the field of nanoelectonics has evolved into a major area of investigation. In this paper, we present a novel method of nanofabrication using pulsed lasers and near-field optical properties of sub-micron particles. For this purpose, spherical silica particles were deposited on a silicon surface. After laser illumination, hillocks with size of about 150 nm were obtained at the original position of the particles. The mechanism can be explained as the enhancement of light intensity near the contact area. Since the characteristic distance between particles and substrate is smaller than the radiation wavelength and the particle size is of the order of a wavelength, particle does not simply play the role of microfocusing lens as in far-field, but possess optical resonance effect in near-field. In our work, the light intensity on the surface under the spherical particle was calculated by solving the electromagnetic boundary problem “particle on suface”.

Laser cleaning as a new cleaning technique has emerged in order to effectively remove contaminants from solid surfaces. Two types of laser cleaning techniques have been developed recently, relying on pulsed laser heating of the surface without or with the presence of a thin liquid coating. Laser cleaning was demonstrated both theoretically and experimentally to be an effective cleaning technique for removing contaminants from solid surfaces without damage. For dry laser cleaning, two cleaning models were established for removal of particles from substrate surfaces from the viewpoint of energy and force. For steam laser cleaning, a cleaning model was established for removal of particles from substrate surfaces with a thin liquid layer by taking Van der Waals force, capillary force, cleaning force, and chemical bonding into account. The models not only explain the influence of incident direction, wavelength, fluence on cleaning efficiency, but also predict the cleaning thresholds. The experimental results show that the laser cleaning efficiency increases with increasing fluence and pulse number, but does not depend on the repetition rate. The surface cleanliness can be monitored in real time by acoustic, electric and optical means. Applications of laser cleaning to clean magnetic slider surface, magnetic media surface, silicon wafer and IC mold surface will also be addressed. Engineering efforts and technical barriers of laser cleaning will be discussed in detail.

Laser cleaning has emerged as an effective cleaning technique for removing contaminants from solid surfaces. Dry laser cleaning and steam laser cleaning have been developed recently, relying on pulsed laser heating of the heating of the surface without and with the presence of a thin liquid coating. Two cleaning models for the viewpoint of force and energy for dry laser cleaning and a cleaning model for steam laser cleaning were established for removal of particles from solid surfaces by taking Van der Waals force, capillary force and cleaning force into account. The models not only explain the influence of laser fluence on cleaning efficiency, but also predict the cleaning thresholds. Laser- induced removal of film-type contaminants has been studied and the surface cleanliness has been studied and the surface cleanliness can be monitored in real time by acoustic and electric means.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser cleaning was demonstrated both theoretically and experimentally to be an effective cleaning technique forremoving particulate and fihn-type contaminants from solid surfaces in this paper. The 1aserinduced removal offilm-type contaminants from IC (IntegTated Circuit) packages, IC mould, Printed Circuit Board and flexible circuitwas StUdied. The cleaning models were established for removal of particles from substrate surfaces without andwith a thin liquid layer by taking adhesion forces and cleaning force into account. The models not only explain theinfluence of laser fluence on cleaning efficiency, but also predict the cleaning thresholds. Laser-induced removalof particles from magnetic sliders and disk surfaces was investigated. Monitoring of laser cleaning by acousticwave, electric field signal and particle counter was also addressed.KEYWORDS: Laser cleaning, cleaning model, cleaning mechanisms, cleaning applications.

In this paper, we report our investigation on the kinetics of nanostructure fabrication on gold films and on H-passivated Ge surfaces. The relationship between the current and the tip-sample distance of the STM junction was measured for both gold films and H-passivated Ge surfaces. The tip-sample distance for gold films under a electrochemically etched W tip is approximately 2 nm, while that for H-passivated Ge sufaces is more than 27 nm. The thermal expansion length of the tip under laser irradiation was calculated. From the comparison of the thermal expansion length and the tip-sample distance, we can reach the conclusion that for gold films, thermal mechanical indention is the primary reason of nanostructure formation, while for H-passivated Ge surfaces, optical enhancement is the only reason.

Laser cleaning has emerged to effectively remove contaminants from solid surfaces. In this paper, recent progress on laser cleaning has been studied. First, a cleaning model is established for removal of particles from substrate surfaces. The model not only explains the influence of fluence on cleaning efficiency, but also predicts the cleaning thresholds. Following that, the optical resonance and near field effect are discussed for transparent particles with a size of α ∼ λ (radiation wavelength) which strongly influences the intensity distribution in the contacted area (substrate surface). The characterization of ejected particles during laser cleaning is finally investigated. It is found that the particle distribution curves closely fit to Gaussian curve.

Laser cleaning is an effective cleaning method that can be widely used in microelectronic industry. Mechanisms of laser induced removal of particulate contaminants from solid substrates, such as Si wafer, are of great concern. The previous works on laser cleaning are mostly based on perfectly flat surface model, while few of them are objected to the influence of surface morphology. In the IC process, however, the Si surface morphology will change dramatically after few steps of processing, therefore its influence to laser cleaning efficiency is inevitable.In this experiment, the cleaning efficiencies of 2.5 and 1.0 micrometers spherical silica particles from Si with different surface morphologies are investigated. These surfaces were achieved by anisotropic etching of Si wafers in KOH solvent, with etching times raging form 1 minute to 30 minutes. Atomic force microscope observation showed the Rp-v roughness of thus-processed Si surfaces ranges from 1.6 nm to 70 nm, and rms roughness ranges from 0.1 nm to 9.0 nm. For both kinds of particles, the cleaning efficiencies decrease with increasing surface roughness. The possible reason is that the rough surface may buffer the sudden thermal expansion of the substrate, making the particles more difficult to be removed.

Recently, scanning probe lithography by applying an electric field between the tip and the sample has been shown to be a promising technique for nanofabrication. In this paper, we present a novel method of nanofabrication, namely, nanolithography by tip-enhanced laser irradiation. Based on the operation of the laser-assisted scanning tunneling microscope (STM), we established a nanolithography system using tip-enhanced laser irradiation, which was developed from a commercial scanning probe microscope (SPM). In our investigation, the SPM was operated as an STM. During imagin and lithography, the STM is in a constant current mode. The tip is fixed and the sample moves via a tube scanner. Nanolithography software controls the scanner movement in the x and y direction. The SPM has an open architecture, allowing an external laser beam incident on the tip at an incident angle between 0 to 45 degrees. A vertical polarized Nd:YAG pulsed laser with a pulse duration of 7 ns was focused on the surfaces of the tip and the sample. An electrical shutter was introduced to switch the laser irradiation during lithography. Alignment of the laser to the tip-sample gap was performed under a high power charge coupled device microscope. Nanolithography was performed on hydrogen (H)-passivated Si (100) surfaces and H-passivated Ge (100) surface.s The Si samples and the Ge samples were passivated in HF solution. STM tips were homemade electrochemically form a 0.5-mm tungsten wire. Oxide features were created by tip-enhanced laser irradiation. The experimental result will be discussed.

Laser cleaning was demonstrated both theoretically and experimentally to be an effective cleaning techniques for removing particulate and thin film contaminants from electronic materials. Two types of laser cleaning techniques have been discussed, relying on pulsed laser of the surface without or with the presence of a thin liquid coating. For dry and steam laser cleaning, cleaning models were established for removal of particles from substrate surfaces without or with a thin liquid layer by taking adhesion forces and cleaning force into account. The models not only explain the influence of laser fluence on cleaning efficiency, but also predict the cleaning thresholds. The laser-induced removal of organic thin film contaminants is considered due to laser ablation of the contaminants. Applications of laser cleaning to clean magnetic sliders, magnetic media surfaces, IC mold and PCB will also be addressed.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser cleaning of disk surfaces was investigated both experimentally and theoretically. It was found that laser cleaning efficiency increases with increasing laser fluence and pulse number. The optimal cleaning conditions can be selected between the two boundaries of damage thresholds and critical cleaning thresholds (100% cleaning). A cleaning model was established for laser-induced removal of particles from substrate surfaces by taking Van der Waals force and cleaning force into account. The theoretical analysis shows that the cleaning force (per unit area) increases with increasing laser fluence, which leads to a higher cleaning efficiency for removing particles from disk surfaces. The experimental results can be explained by the model and simulation.

Dry and steam laser cleaning was investigated both theoretically and experimentally. The experimental results show that cleaning efficiency increases with increasing laser fluence or decreasing laser wavelength. The cleaning thresholds exist both dry and steam laser cleaning. A cleaning model was established for laser-induced removal of particles from solid surfaces by taking adhesion force, such as Van der Waals force and capillary force, and cleaning force into account. Laser cleaning forces are induced by fast thermal expansion of particles and/or solid surfaces irradiated by laser for dry laser cleaning and evaporating liquid film heated by laser irradiation for steam laser cleaning, respectively. It was found that laser cleaning forces increase with an increase of laser fluence. At the same laser fluence, cleaning forces increase with decreasing laser wavelength. Cleaning thresholds can be obtained by comparing cleaning force and adhesion force. The experimental results are good consistent with the theoretical analysis.

Carbon nitride thin films were deposited on silicon wafers by pulsed KrF excimer laser (wavelength 248 nm, duration 23 ns) ablation of graphite in nitrogen atmosphere. Different fluences of the excimer laser and pressures of the nitrogen atmosphere were used in order to achieve a high nitrogen content in the deposited thin films. Fourier Transform Infra-red (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to identify the binding structure and the content of the nitrogen species in the deposited thin films. The highest N/C ratio 0.42 was achieved at an excimer laser fluence of 0.8 Jcm -2with a repetition rate of 10 Hz under the nitrogen pressure of PN=100 mTorr. A high content of C=N double bond instead of C-N triple bond was indicated in the deposited thin films. Ellipsometry was used to analyze the optical properties of the deposited thin films. The carbon nitride thin films have amorphous-semiconductor-like characteristics with the optical band gap Eop, as high as 0.42 eV.

A theoretical model for removal of tiny particles from solid surface covered with a thin liquid film by laser cleaning is established by taking adhesion force and cleaning force into account. When pulsed laser irradiates on the solid surface coated with a thin liquid film, a sheet of liquid near the liquid/substrate interface can be superheated through thermal diffusion. The rapid growth of vapor bubbles inside the superheated liquid can generate transient stress wave with high pressure, large enough to expel micron and sub-micron particles from the contaminated surface. By calculating the adhesion force and cleaning force, the cleaning threshold of laser fluence can be predicted from this theoretical model. The difference between cleaning force and adhesion force increases quickly along with the laser fluence and leads to higher cleaning efficiency.

In this study, nickel-phosphorus (NiP) surface is irradiate by a KrF excimer laser beam. Atomic force microscope and x- ray diffraction are employed to study the surface morphology and the material structure. For laser fluence form 124 mJ/cm2, thin periodic structure morphology is formed in the irradiated region. When laser fluence exceeds 200 mJ/cm2, a microcosmic-smooth ripple morphology is obtained. The period of the second morphology is obviously larger than that of the first morphology. The morphology is dependent on the original surface condition, laser fluence and laser pulse number in the low laser fluence region and only laser fluence and laser pulse number in the high laser fluence region. 1D thermal conduction model is used to predict the temperature rise in the irradiated region. Surface melting is predicted to take place at laser fluence about 200 mJ/cm2. The interaction mechanism between laser beam and NiP surface is proposed based on the theoretical calculation and experiment.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A laser cleaning model was established for removal of non- absorbing particles from an absorbing solid surface by taking adhesion force and cleaning force into account. The cleaning force per unit area due to laser-induced thermal expansion of a substrate surface is (gamma) E (Delta) T(0, t), where (gamma) , E, and (Delta) T(0, t) are the linear thermal expansion coefficient, the elastic modulus and temperature rise at the substrate surface, respectively. The cleaning condition and threshold fluence can be obtained by comparing the cleaning force and the adhesion force. The theoretical analysis shows that cleaning force increases with increasing laser fluence, deducing the pulse duration, or decreasing laser wavelength, which leads to a higher cleaning efficiency at higher laser fluence, smaller pulse duration or shorter laser wavelength. The experimental results show that the cleaning threshold fluence for laser removal of quartz particles from silicon surfaces is about 135 mJ/cm2, which is in good consistency with the theoretical threshold fluence of 120 mJ/cm2. With increasing laser fluence, the cleaning efficiency increases, which has been predicted by our theoretical analysis.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A theoretical model for laser cleaning of microparticles from solid surface was established by taking adhesion force and cleaning force into account. The threshold fluence can be obtained from this model and verified by the experimental results. It was found that laser irradiation from the reverse side of transparent substrate is more effective to remove particles than that from the front side. Laser irradiation with shorter wavelength can result in higher cleaning efficiency and lower threshold fluence for removal of particles from solid surfaces. Keywords: Laser cleaning, microparticles, Van der Waals force, cleaning force, cleaning threshold

Audible acoustic wave generation during KrF excimer laser processing of microelectronic materials Si, Cu and Al is investigated. It is found that amplitude of the acoustic wave is closely related to laser pulse number and laser fluence. Due to the laser cleaning of surface contamination, the amplitude reduces to a steady level with laser irradiation up to a pulse number of 10. The first peak-to- peak amplitude of the acoustic wave at the steady condition is used to evaluate laser interaction with the materials. The amplitude analysis shows that there exists a threshold fluence. For laser fluence higher than the threshold, the amplitude increases with laser fluence. Threshold fluences are 1.1, 1.35 and 1.2 J/cm2 for Si, Cu and Al respectively. It also shows that the increase of the amplitude starts to saturate for laser fluence higher than 10 J/cm2. According to ablation rate measurement, these thresholds of fluences are the same as the ablation thresholds of the materials. Saturation of amplitude increase is due to plasma shielding effect during the laser ablation of the materials. Theoretical calculation agrees well with the experimental result. Acoustic wave measurement provides a simple method to detect the threshold fluences of laser ablation and plasma shielding. By proper calibration, it can also be used as a real-time measurement of laser ablation rate. By applying appropriate pulse number, the laser processing of microelectronic materials can be controlled in-situ.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In laser cleaning of micro-particles from solid surface, the adhesion force between the particles and the substrate surface and the thermal expansion of both particles and substrate play important roles in determining the threshold laser fluence. Taking Van der Waals force and cleaning force due to fast thermal expansion of particles and substrate surface induced by pulsed laser irradiation into account, a cleaning model was established for removal of tiny particles from substrate surfaces. The cleaning condition and cleaning threshold can be obtained from this model. This model can qualitatively and quantitatively predict how the laser cleaning process depending on laser incident direction, laser wavelength, particle size, particle material and substrate material. Theoretical predictions have been verified by the experimental results. Laser cleaning of micro-particle has wide applications in microelectronics and magnetic recording industries.

We show a method for studying diffusion barriers for phase change memory devices. The method involves placing a barrier layer between a phase change material like Ge2Sb2Te5 and Fe and taking note of the magnetization changes of the Fe layer before and after anneal. This results in a fast, sensitive but qualitative measure of various diffusion barriers. Based on this analysis, Ru was found to be good diffusion barrier comparable to the conventional TiW, while Pt is a poor barrier. These results were then reconfirmed by X-ray photoelectron spectroscopy depth studies.

Investigating the levels of lipid peroxidase (LPO) and superoxide dismutase (SOD) in serum, bronchoalveolar lavage fluid (BALF) and alveolar macrophage (AM) were determined in 40 chronic bronchitis patients with Pulmonary Qi Deficiency (PQD) Syndrome and 36 normal subjects. Results showed: (1) No significant differences were found between PQD syndrome and normal subjects on serum SOD or LPO levels. (2) Patients with PQD Syndrome. LPO level in BALF was significantly higher, and SOD significantly lower, when compared with normal subjects. (3) Through correlation analysis, it was found in BALF that SOD level was markedly correlated with AM, while LPO was significantly correlated with neutrophil. In short, SOD and LPO in BALF play an important role in the development of the PQD Syndrome, and are good indications in evaluating the PQD Syndrome.

Laser dry cleaning of ZrO2 particles from air bearing surface (ABS) of magnetic head sliders has been investigated. The experimental results show that the cleaning threshold of removing ZrO2 particles from ABS is about 100 mJ/cm2. For laser fluence larger than this threshold, cleaning efficiency increases with increasing laser fluence and pulse number, but does not depend on repetition rate up to 30 Hz. The mechanisms of this laser dry cleaning are laser-induced ABS vibration, particle thermal expansion and particle vibration, which produce forces strong enough to detach ZrO2 particles from ABS. With increasing laser fluence and pulse number, the average acceleration and vibration number of particles induced by laser increase respectively, so that it is easier to remove particles which corresponds to higher cleaning efficiency. For fixed laser fluence and pulse number, changing the repetition rate does not change the average acceleration or the vibration number of particles, therefore laser cleaning efficiency is almost the same for different repetition rates.

Phase change materials have become significantly attractive due to its unique characteristics for its extensive applications. In this paper, a kind of phase change material, which consists of Fe and Te components, is developed. The crystallization temperature of the Fe-Te materials is 180 °C for Fe1.19Te and can be adjusted by the Fe/Te ratio. High-speed phase change in the Fe-Te materials has been demonstrated by nanosecond laser irradiation. Comparing to conventional phase change materials, the Fe-Te materials exhibit an anomalous optical property that has higher reflectivity at amorphous than crystalline state, which is useful for data storage design. Published version

Serum cortisol levels and bronchoalveolar lavage fluid (BALF) from 105 patients with chronic obstructive pulmonary disease (COPD) and 36 normal subjects were examined and the relationship between cortisol inhibiting the TXB2 secreted by alveolar macrophage (AM) and the theory of Syndrome Differentiation in TCM was explored. Results showed: (1) No significant differences were found between chronic bronchitis and normal subjects on cortisol levels in serum, but in BALF, cortisol levels was significantly lower in Lung Qi Deficiency when compared with that in normal subjects. (2) the levels of cortisol inhibiting the TXB2 secreted by AM which were significantly lower in chronic bronchitis when compared with that in control. In short, the amount and function of cortisol in BALF were significantly different in various syndromes in TCM of chronic bronchitis.

Sn-doped Ge–Sb–Te material was prepared by laser synthesis. It has a rocksalt crystal structure for Sn doping content less than 30at.%. A phase change temperature tester was developed to in situ measure crystallization temperature and melting point of Sn-doped Ge–Sb–Te. The crystalliza-tion temperature of Sn-doped Ge–Sb–Te is close to that of Ge2Sb2Te5 while its melting point is much lower than that of Ge2Sb2Te5. The melting points of Sn9.8Ge20.3Sb28.4Te41.5 and Sn18.8Ge19.5Sb25.3Te36.4 are 475 and 450°C, respectively. The crystallization speed was tested by an ultraviolet light at pulse duration of 30ns. It exhibits a high crystallization speed.

A small anomalous Hall effect signal of a Zn1−xCoxO (x=0.05) thin film was observed, indicating that there presents sp-d interactions in the Zn1−xCoxO thin film. However, under a self-held setup, we did not obtain observable differences between the M-H curves when the near band electrons were changed. Integrated with our previous results, possible mechanisms for the magnetism of Zn1−xCoxO thin films were proposed based on a picture of spins in a carrier sea.

Dual beam pulsed laser deposition was used to synthesize Zn1−xCoxO thin films with a large range of Co concentrations. In this paper, the influence of growth temperature on the crystal structures, magnetic properties, and semiconductor properties of these films was studied. It was found that the growth temperature has a significant effect on dopant concentration, as well as the structure and properties of the films. The optimum growth temperature is around 650°C. The thin films were of single crystal especially at low Co concentrations. Epitaxial growth of the thin films was observed. No precipitates were observed at low Co concentrations. Magnetic hysteresis loops were observed at room temperature, indicating that magnetism can be realized with Co doped into ZnO. However, the improvement was limited. The Hall resistivity tended to increase, while carrier density tended to decrease with Co concentration until a certain Co concentration (10%) is achieved. When the growth temperature was greater than 650°C,...

We have investigated phase separation, silicon nanocrystal (Si NC) formation and optical properties of Si oxide (SiOx, 0

Pulsed-laser assisted nanopatterning of metallic layers on silicon substrates under an atomic force microscope (AFM) tip has been investigated. A 532 nm Nd:YAG pulsed laser with a pulse duration of 7 ns was used. Boron doped silicon tips were used in contact mode. This technique enables the processing of structures with a lateral resolution down to 10 nm on gold and copper layers. Nanopatterns such as pit array and multilines with lateral dimensions between 10 and 50 nm and depths between 2.5 and 21 nm have been created. The experimental results and mechanism of the nanostructure formation are discussed. The created features were characterized by AFM, scanning electron microscope, and Auger electron spectroscopy. The apparent depth of the created pit has been studied as a function of laser intensity or laser pulse numbers. The dependence of nanoprocessing on the geometry parameters of the tip and on the optical and thermal properties of the processed sample has also been investigated. Thermal expansion of...

Particle adhesion and removal are of great interest in IC process and high-density hard disk manufacturing. Increasing effort is required to remove submicron particles. We investigated the adhesion and removal of spherical silica particles from silicon (Si), germanium (Ge) and NiP substrates using a KrF excimer laser. Atomic force microscope (AFM) point-contact mode measurement showed that the tip adhesion force on Ge surface is greater than that on Si or NiP surface, and the Hamaker constant of NiP is about 2/3 of that of Ge substrate. The cleaning efficiency and cleaning thresholds for standard-size particles with a diameter of 1.0 µm were measured. The cleaning efficiency was sensitive to laser fluence. The threshold laser fluences for Si, Ge and NiP are 100, 30 and 8 mJ/cm2, respectively. The different cleaning curves are not only due to the difference in adhesion on the substrates, but also due to the different optical and thermal properties of the substrates.

Laser-induced removal of organic contaminants on IC mould surfaces was studied both experimentally and theoretically. The mould surfaces before and after cleaning were observed under an optical microscope and analysed by Auger electron spectroscopy (AES). It was found that the contaminants in the irradiated area were effectively removed by pulsed laser irradiation at a laser fluence greater than the cleaning threshold of 100 mJ/cm2. The cleaning efficiency increases with increasing laser fluence and the damage threshold of the mould surfaces is about 1.05 J/cm2, which is in good agreement with the theoretical damage threshold. We also demonstrated that the acoustic wave detection in real-time can be used to both monitor the surface cleanness during the laser cleaning process and determine the cleaning threshold and cleaning efficiency.

A theoretical model for removal of tiny particles from solid surface by laser cleaning with a thin liquid layer is established by taking adhesion force and cleaning force into account. When pulsed laser irradiates on the solid surface coated with a thin liquid film, a sheet of liquid near the liquid/substrate interface can be superheated through thermal diffusion. The rapid growth of vapor bubbles inside the superheated liquid can generate transient stress wave with high pressure, large enough to expel micron and sub-micron particles from the contaminated surface. Through calculating adhesion force and cleaning force, the cleaning threshold of laser fluence can be predicted from this theoretical model and the difference between cleaning force and adhesion force increases with increasing of laser fluence, leading to higher cleaning efficiency.

The wavelength effects in the laser cleaning process were studied both theoretically and experimentally. As the reflectivity and absorption coefficient depend on laser wavelength, different wavelengths will result in different temperature distributions in a particle or a substrate so that various cleaning forces and efficiencies are induced in the laser cleaning process. For laser-induced removal of copper and aluminum particles from quartz surfaces, the cleaning efficiency is higher and the threshold fluence is smaller for a shorter wavelength under the same cleaning parameters. This is because laser irradiation at a shorter wavelength causes a higher temperature rise and induces a greater cleaning force in a copper or aluminum particle, which results in higher cleaning efficiency and lower threshold fluence. The theoretical analysis can successfully predict and explain the experimental results.

Taking Van der Waals force and cleaning force due to fast thermal expansion of substrate surface induced by pulsed laser irradiation into account, a cleaning model was established for removal of tiny particles from substrate surfaces. The cleaning condition and cleaning threshold can be obtained from this model. Theoretical predictions have been verified by the experimental results for removing quartz particles from silicon substrate. For laser-induced removal of quartz particles from silicon substrate surfaces, the cleaning threshold is about 135 mJ/cm2. Cleaning efficiency increases with increasing laser fluence, and large particles can be removed more easily than small ones.

The dual-beam laser ablation of different targets for synthesizing new materials within the overlapping plasma area has been investigated. This method is termed ‘laser synthesis of new materials’ and it is flexible in tuning the composition of the new materials by varying the targets, the laser fluence on each target and the input gas as well as the substrate position within the overlapping plasma area. A new Ba–Fe–Y–O magnetic material has been synthesized by this method, which can be written as BaOkFe2-xYxO3, where k is either 6 or 11 and x is about 0.4 or 0.9 for BaFe9.2Y2.6O20 or BaFe12.3Y9.6O33.3 material. Both materials are permanent magnets and have hexagonal structure. The lattice parameters a and c are 0.551 nm and 2.337 nm for BaFe9.2Y2.6O20 and 0.747 nm and 2.332 nm for BaFe12.3Y9.6O33.3, respectively.