Processing Grinding-Damaged Silicon Wafers by High-Frequency Nano-Second Laser Irradiation

2009 ◽  
Vol 76-78 ◽  
pp. 451-456
Author(s):  
Ji Wang Yan ◽  
Sei Ya Muto ◽  
Tsunemoto Kuriyagawa
Keyword(s):  
Energy Density ◽  
Amorphous Silicon ◽  
Laser Irradiation ◽  
High Frequency ◽  
Laser Energy ◽  
Large Diameter ◽  
Silicon Wafers ◽  
Density Level ◽  
Transmission Electron ◽  
Beam Center

Ultraprecision diamond-ground silicon wafers were irradiated by a high-frequency nanosecond pulsed Nd:YAG laser equipped on a four-axis numerically controlled stage. The resulting specimens were characterized using a white-light interferometer, a micro-Raman spectroscope and a transmission electron microscope. The results indicate that around the laser beam center where the laser energy density is sufficiently high, the grinding-induced amorphous silicon was completely transformed into the single-crystal structure. The optimum conditions for one- and two-dimensional overlapping irradiation were experimentally obtained for processing large-diameter silicon wafers. It was found that the energy density level required for completely removing the dislocations is higher than that for recrystallizing the amorphous silicon. After laser irradiation, the surface unevenness has been remarkably flattened.

scholarly journals Carbon-coated magnetic particles increase tissue temperatures after laser irradiation

2015 ◽  
Vol 08 (05) ◽  
pp. 1550018 ◽  
Author(s):  
Shupeng Liu ◽  
Na Chen ◽  
Fufei Pang ◽  
Zhengyi Chen ◽  
Tingyun Wang
Keyword(s):  
Laser Irradiation ◽  
Magnetic Particles ◽  
Laser Energy ◽  
Thermal Therapy ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fbg Sensor ◽  
Transmission Electron ◽  
Carbon Coated

Purpose: This work focused on the investigation the hyperthermia performance of the carbon-coated magnetic particles (CCMPs) in laser-induced hyperthermia. Materials and methods: We prepared CCMPs using the organic carbonization method, and then characterized them with transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectrophotometry, vibrating sample magnetometer (VSM) and X-ray diffraction (XRD). In order to evaluate their performance in hyperthermia, the CCMPs were tested in laser-induced thermal therapy (LITT) experiments, in which we employed a fully distributed fiber Bragg grating (FBG) sensor to profile the tissue's dynamic temperature change under laser irradiation in real time. Results: The sizes of prepared CCMPs were about several micrometers, and the LITT results show that the tissue injected with the CCMPs absorbed more laser energy, and its temperature increased faster than the contrast tissue without CCMPs. Conclusions: The CCMPs may be of great help in hyperthermia applications.

Complete Recovery of Subsurface Structures of Machining-Damaged Single Crystalline Silicon by Nd:YAG Laser Irradiation

2008 ◽  
Vol 389-390 ◽  
pp. 469-474 ◽  
Author(s):  
Ji Wang Yan ◽  
Tooru Asami ◽  
Tsunemoto Kuriyagawa
Keyword(s):  
Nd:Yag Laser ◽  
Crystalline Silicon ◽  
Laser Energy ◽  
Recovery Process ◽  
Complete Recovery ◽  
Amorphous Layer ◽  
Boundary Region ◽  
Silicon Wafers ◽  
Near Surface ◽  
Transmission Electron

Ultraprecision diamond-cut silicon wafers were irradiated by a nanosecond pulsed Nd:YAG laser, and the resulting specimens were characterized using transmission electron microscopy and micro-Raman spectroscopy. The results indicate that at specific laser energy density levels, machining-induced amorphous layers and dislocated layers were both reconstructed to a complete single-crystal structure identical to the bulk region. Similar effects were confirmed for diamond-ground silicon wafers. Effects of overlapping irradiation were investigated and perfect crystallographic uniformity was achieved in the boundary region. The recovery process involved rapid melting of the near-surface amorphous layer, followed by epitaxial regrowth from the damage-free crystalline bulk.

The Shallow Implantation of Bismuth During the Growth of Bismuth Nanocrystals in Al2O3 by Pulsed Laser Deposition

2003 ◽  
Vol 780 ◽  
Author(s):  
A. Suárez-García ◽  
J-P. Barnes ◽  
R. Serna ◽  
A. K. Petford-Long ◽  
C. N. Afonso ◽  
...  
Keyword(s):  
Energy Density ◽  
Cross Section ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Laser Energy Density ◽  
X Ray ◽  
Continuous Layer ◽  
Transmission Electron ◽  
Order Of Magnitude

AbstractThe effect of the laser energy density used to deposit Bi onto amorphous aluminum oxide (a-Al2O3) on the growth of Bi nanocrystals has been investigated using transmission electron microscopy of cross section samples. The laser energy density on the Bi target was varied by one order of magnitude (0.4 to 5 J cm-2). Across the range of energy densities, in addition to the Bi nanocrystals nucleated on the a-Al2O3 surface, a dark and apparently continuous layer appears below the nanocrystals. Energy dispersive X-ray analysis on the layer have shown it is Bi rich. The separation from the Bi layer to the bottom of the nanocrystals on top is consistent with the implantation range of Bi species in a-Al2O3. As the laser energy density increases, the implantation range has been measured to increase. The early stages of the Bi growth have been analyzed in order to determine how the Bi implanted layer develops.

Excimer Laser Crystallized Amorphous Silicon Films: Effects of Shot Density and Substrate Temperature

1991 ◽  
Vol 219 ◽  
Author(s):  
R. I. Johnson ◽  
G. B. Anderson ◽  
S. E. Ready ◽  
J. B. Boyce
Keyword(s):  
Energy Density ◽  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Laser Energy ◽  
Silicon Films ◽  
Laser Energy Density ◽  
Laser Crystallization ◽  
Average Grain Size ◽  
Substrate Temperatures

ABSTRACTLaser crystallization of a-Si thin films has been shown to produce materials with enhanced electrical properties and devices that are faster and capable of carrying higher currents. The quality of these polycrystalline films depends on a number of parameters such as laser energy density, shot density, substrate temperature, and the quality of the starting material. We find that the average grain size and transport properties of laser crystallized amorphous silicon films increase substantially with laser energy density, increase only slightly with laser shot density, and are unaffected by substrate temperatures of up to 400°C. The best films are those processed in vacuum but films of fair quality can also be obtained in air and nitrogen atmospheres.

Laser Encapsulation of Metallic Films in SiO2

1995 ◽  
Vol 397 ◽  
Author(s):  
A. J. Pedraza ◽  
S. Cao ◽  
D. H. Lowndes ◽  
L. F. Allard
Keyword(s):  
Energy Density ◽  
Laser Pulse ◽  
Laser Energy ◽  
Substrate Material ◽  
Laser Energy Density ◽  
Cross Sectional ◽  
Metallic Particles ◽  
Transmission Electron ◽  
Encapsulation Process ◽  
Deposited Film

ABSTRACTThin films of gold, copper and iron deposited on silica were driven into the substrate by a laser pulse. This transport takes place only when the irradiation is performed at a laser energy density of 0.7 J/cm2 or lower. Cross sectional transmission electron microscopy (TEM) of the irradiated specimens reveals two distinctive stages in the encapsulation process. In the first, the film melts and clusters into small particles and in the second one the particles are driven into the substrate by the laser pulse. The particle size of encapsulated metal varies from 5 to 50 nm. Selected area diffraction of the large particles and lattice fringe images of the smaller particles reveal pure metals, e.g., gold, copper or iron. Titanium films laser irradiated are not encapsulated in silica; instead, these films react with silica forming an amorphous compound. Apparently, one of the conditions required for encapsulation is that the metal should not react with the substrate material. On subsequent irradiation at a laser energy density of 1.5 J/cm2, ablation of silica partially exposes the metallic particles. Strong bonding between a new film deposited after irradiation and the substrate is obtained because these particles anchor the freshly deposited film. Anchoring is clearly revealed by cross sectional TEM. The mechanisms of encapsulation are discussed using results from TEM and adhesion testing.

Er-Doping in Silicon by Pulsed Laser Irradiation

1993 ◽  
Vol 301 ◽  
Author(s):  
Kenshiro Nakashima
Keyword(s):  
Energy Density ◽  
Laser Irradiation ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Laser Energy Density ◽  
Er Doping ◽  
Erbium Ions ◽  
State Regime ◽  
Er Doped ◽  
Pulsed Laser Irradiation

ABSTRACTErbium ions were successfully doped in silicon by pulsed laser irradiation above the threshold laser energy density. Photoluminescence peaks at 1.54, 1.59 and 1.64 µm from Er-optical centers were observed after annealing of Er-doped samples. The intensity of the 1.54 µm Er-emission band increased upon increase in the laser energy density, and then gradually decreased after reaching the maximum, due to the laser sputtering of the silicon substrate. Oxygen atoms, which were unintentionally codoped with Er-ions, were found to be distributed in the same region as in Er-ions, and were suggested to play roles to activate Er-optical centers. The maximum concentration of Er-ions doped in the solid state regime were estimated to be the order of 1018 cm−3 by the Rutherford backscattering measurements.

Electrical Properties of Solid Phase Crystallized Silicon Films

2001 ◽  
Vol 664 ◽  
Author(s):  
Tadashi Watanabe ◽  
Hajime Watakabe ◽  
Toshiyuki Sameshima
Keyword(s):  
Heat Treatment ◽  
Electrical Conductivity ◽  
Energy Density ◽  
Laser Irradiation ◽  
Carrier Mobility ◽  
Crystalline Silicon ◽  
Solid Phase ◽  
Laser Energy ◽  
Silicon Films ◽  
Laser Energy Density

ABSTRACTIn this study, the carrier mobility and density for solid phase crystallized (SPC) silicon films fabricated at 600 °C for 48 hours are analyzed by free carrier optical absorption. The carrier mobility is 40 cm2/Vs for SPC films doped with 6×1019-cm−3-phosphorus atoms. This analysis suggests the SPC films have fine crystalline grains closed to single crystalline silicon. In addition, initial carrier density was 3×1019 cm−3, which increased to 6×1019 cm−3by XeCl excimer laser irradiation of 500mJ/cm2. The inactivated regions in SPC films are reduced by laser irradiation. However, the electrical conductivity after laser irradiation for SPC films doped with 6×1018-cm−3-phosphorus atoms decreased from 3.3 to 0.018 S/cm as laser energy density increased to 500mJ/cm2. On the other hand, the electrical conductivity increased from 14.7 to 31.3 S/cm with similar increase of laser energy density after H2O vapor heat treatment at 260°C for 3 hours with 1.3 MPa. Furthermore, the characteristics of n-channel TFTs fabricated with initial SPC films as well as SPC films which was irradiated by laser at 425mJ/cm2 are also researched. The threshold voltage is decreased from 3.8 to 2.0 V by laser irradiation. Threshold voltages of both cases are decreased from 3.8 to 2.4 V for no-laser irradiation and from 2.0 to 0.8 V for laser irradiation, after H2O vapor heat treatment at 310°C for 1 hour with 9.0MPa. Based on the above trial, the defect reduction method combining laser irradiation and H2O vapor heat treatment has proved to be very effective for SPC films and SPC TFTs.

Low-Energy, Pulsed-Laser Irradiation of Amorphous Silicon: Melting and Resolidification at Two Fronts

1984 ◽  
Vol 35 ◽  
Author(s):  
W. Sinke ◽  
F.W. Saris
Keyword(s):  
Amorphous Silicon ◽  
Laser Irradiation ◽  
Surface Segregation ◽  
Crystalline Silicon ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Surface Region ◽  
Low Energy ◽  
Double Peak Structure ◽  
Pulsed Laser Irradiation

ABSTRACTAfter low-energy pulsed-laser irradiation of Cu-implanted silicon, a double-peak structure is observed in the Cu concentration profile, which results from the occurrence of two melts. From Cu surface segregation we calculate the depth of the surface melt. Cu segregation near the position of the amorphous-crystalline interface gives evidence for a self-propagating melt, moving from the surface region towards the crystalline substrate. Measurements of As-redistribution and of sheet resistance as a function of laser energy density in As-implanted silicon are consistent with the crystallization model which is derived from the effects as observed in Cu-implanted silicon.The results imply a large difference in melting temperature, heat conductivity and heat of melting between amorphous silicon and crystalline silicon.

Doping of GaAs From Silane Decomposition Under Pulsed Laser Irradiation

1983 ◽  
Vol 29 ◽  
Author(s):  
D. Pribat ◽  
D. Dieumegard ◽  
B. Dessertenne ◽  
J. Chaplart
Keyword(s):  
High Pressure ◽  
Energy Density ◽  
Laser Irradiation ◽  
Sheet Resistance ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Compensation Mechanism ◽  
Yag Laser ◽  
Oxygen Penetration ◽  
Pulsed Laser Irradiation

ABSTRACTWe have studied silicon incorporation in GaAs subsequent to Nd-YAG laser irradiation through high pressure silane atmospheres. The process involves SiH4 pyrolysis at contact with a laser-melted GaAs surface, and incorporation of the released Si atoms in the melt. SIMS analyses have allowed us to study silicon incorporation as a function of SiH4 pressure, laser energy density and number of laser shots. The high sheet resistance of the doped layers indicates that the silicon atoms are poorly electrically activated. A compensation mechanism is discussed based on oxygen penetration from native GaAs oxide layers.

Laser Dehydrogenation of PECVD Amorphous Silicon

1993 ◽  
Vol 297 ◽  
Author(s):  
Ping Mei ◽  
J.B. Boyce ◽  
M. Hack ◽  
R.A. Lujan ◽  
R.I. Johnson ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Laser Energy ◽  
Film Structure ◽  
Maximum Temperature ◽  
Transient Phenomena ◽  
Silicon Thin Films ◽  
Transmission Electron ◽  
Hydrogenated Amorphous ◽  
Melt Duration ◽  
Low Temperature Process

A low temperature process for laser dehydrogenation and crystallization of hydrogenated amorphous silicon has been studied. The key feature of this process is the removal of hydrogen from the amorphous silicon thin films while crystallizing the films at the same time. Studies of transient phenomena, hydrogen loss, and crystallinity, using transient reflectivity analyses, transmission electron microscopy and quadrupole mass spectrometry, find that hydrogen out-diffusion depends strongly on film structure and the melt duration controlled by the laser energy density. Utilizing this process, for which the maximum temperature is 350 °C, both high quality polycrystalline and amorphous silicon TFT's have been fabricated on the same Corning 7059 glass substrate.

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