Effect Of Laser Annealing Research Articles

Effect of laser annealing using high repetition rate pulsed laser on optical properties of phosphorus-ion-implanted ZnO nanorods

The effect of high repetition rate pulsed laser annealing with a KrF excimer laser on the optical properties of phosphorus-ion-implanted zinc oxide nanorods has been investigated. The recovery levels of phosphorus-ion-implanted zinc oxide nanorods have been measured by photoluminescence spectra and cathode luminescence images. Cathode luminescence disappeared over 300 nm below the surface due to the damage caused by ion implantation with an acceleration voltage of 25 kV. When the annealing was performed at a low repetition rate of the KrF excimer laser, cathode luminescence was recovered only in a shallow area below the surface. The depth of the annealed area was increased along with the repetition rate of the annealing laser. By optimizing the annealing conditions such as the repetition rate, the irradiation fluence and so on, we have succeeded in annealing the whole damaged area of over 300 nm in depth and in observing cathode luminescence. Thus, the effectiveness of high repetition rate pulsed laser annealing on phosphorus-ion-implanted zinc oxide nanorods was demonstrated.

Influence of pulsed laser annealing on the optical properties of ZnO nanorods

AbstractThe effect of pulsed laser annealing (PLA) on the photoluminescence (PL) properties of ZnO nanorods was investigated. As the fluence of pulsed laser increases, the UV PL in ZnO nanorods shows a general increasing trend, except at a range of fluences from 10 to 70 mJ/cm2. It is found that the treatment with the PLA at the fluence of 70 mJ/cm2 leads to a larger improvement of crystalline properties than that with rapid thermal annealing (RTA). The relationship between PL intensity and fluence of pulsed lasers can be well explained by a combination of the deterioration in surface crystallinity and the increased donor densities after PLA.

Ultra-High Tensile Stress Capping Layer Using Novel Excimer Laser Annealing Technology for 32nm nMOSFET and Beyond

A novel processing technology for stressed capping-layer by 248nm KrF excimer laser is reported. The treated tensile capping layer is composed of silicon nitride fabricated by normal PECVD. The effects of laser annealing with different conditions on tensile nitride are extensively investigated. The number of excimer laser pulses is from 3 to 15 and energy density from 500mJ/cm2 to 800mJ/cm2. Different from conventional post-processing techniques applied in current mainstream CMOS technology for tensile SiN curing, the excimer laser annealing demonstrated much higher energy efficency and as a result, the laser annealing broke more silicon-hydrogen and nitrogen-hydrogen bonds within a much shorter time during film curing. The maximum stress of this cured layer is about 2.2GPa through typical Raman spectroscopy measuring, which much larger than that just after tensile nitride film deposition. This new process supplies one of promising solution for stress-enhancement degradation in sub-32nm CMOS technology.

Electrical properties of textured carbon film formed by pulsed laser annealing

Previous works have showed that textured carbon film can be fabricated by applying suitable ion energy and substrate temperature. In this experiment, the effect of laser annealing on amorphous carbon films was studied. Atomic force microscopy shows the effect of laser irradiation on surface morphology of carbon film, and visible Raman spectroscopy shows that the G peak position shifted from 1540cm−1 to 1600cm−1, and the increase in I(D)/I(G) intensity ratio indicates the formation of more graphitic film at higher laser energy. High resolution transmission electron microscopy (HRTEM) shows the vertical alignment formation at suitable laser energy. Electrical measurement shows that the vertical aligned carbon films exhibit low resistance, ohmic current–voltage characteristics, which suggests that vertical aligned films formed by laser irradiation may be promising material for future nano-device interconnects.

Laser Annealing and Local Heating Effects during Raman Measurement of Hydrogenated Amorphous Silicon Films

Two possible side effects when evaluating the crystalline volume fraction of microcrystalline silicon films by Raman spectroscopy measurement have been investigated. Large laser power incident into the microcrystalline silicon film during measurement may cause some amorphous to crystalline phase transition. In addition, the local temperature rise during measurement also leads to some spectrum shift. Both effects results in incorrect or inaccurate evaluation of microcrystalline silicon film crystallinity. By changing the laser power during amorphous silicon film Raman measurement, it is found that the critical power density to induce crystallization of amorphous silicon is ~455kW/cm2. Furthermore, red-shift of the Raman peak due to local heating effect is observed.

Effect of laser annealing on defected silicon solar cells

The effect of pulsed Nd-YAG laser annealing (λ = 1.06 μm), on the efficiency of defected polycrystalline silicon solar cells has been studied. Cells performance measurement and microscopic structure examinations of the surface using optical and scanning electron microscopy (SEM) have been done before and after irradiation with different laser fluences (2.3 – 25 J/cm2) and for successive times until a steady state has been reached. It is found that the annealing causes a change in the topography of the cells, resulting in an increase in grain size at low fluences and beginning of crystal growth at higher fluences up to an optimum value of 7.5 J/cm2. These processes cause an improvement in the electrical output characteristics of the defect-rich solar cells; hence an increase in the cell efficiency is obtained. The maximum change in efficiency value is found to be about 5 times greater than its initial value. For fluences of more than 16 J/cm2, SEM micrographs show slightly deeper melt front penetration which affects the junction interface and a reduction in light output characteristics of the cells has been detected.

Characteristics of laser-annealed ZnO thin film transistors

We investigated the effects of laser annealing on ZnO thin film transistors (TFTs). ZnO layers were deposited on a bottom-gate patterned Si substrate by radio-frequency sputtering at room temperature. Laser annealing of the ZnO films reduced the full width at half maximum of the ZnO (002) diffraction peak from 0.49° to 0.1°. It reveals that the crystalline quality is improved by annealing effect. A SiO 2 formed in low temperature was used as the gate dielectric. Unannealed ZnO-TFTs were operated in enhancement mode with a threshold voltage of 21.6 V. They had a field-effect mobility of 0.004 cm 2/Vs and an on/off current ratio of 134. Laser annealing of the ZnO-TFTs by 200 laser pulses reduced their threshold voltage to 0.6 V and increased their field-effect mobility to 5.08 cm 2/Vs. The increase of mobility is originated from the crystallization enhancement of ZnO films after laser annealing.

Effects of Laser in situ annealing on crystal quality of NiSi film grown on Si(001) substrate

NiSi thin films grown on Si(001) substrates with a main crystal orientation of NiSi[200]//Si[001] were prepared and Raman spectroscopy was used to study effects of laser annealing on the NiSi thin films. Results show that the crystal quality of the NiSi films can be improved after laser annealing for 60 min at a laser power of 140 mW. We have shown that laser annealing can also be used to make structural phase transitions of NiSi domains under an annealing power of 480 mW for 10 min.

Excimer Laser Annealing Effects of Silicon-rich Silicon Nitride Films Prepared by Using Catalytic Chemical Vapor Deposition

We studied excimer laser annealing effects on silicon-rich silicon nitride films containing silicon quantum dots to develop silicon based flexible Light emitting diodes. The silicon-rich silicon nitride films were deposited by catalytic chemical vapor deposition system using a mixture of SiH4, NH3 and H2 gas. The substrate temperatures in all deposition process were less than 200 ° to use polyethersulphone substrate. The changing crystallity and density of silicon quantum dots were analyzed by photoluminescence spectra. The change in the luminescence behavior with nucleation of silicon quantum dots was observed after excimer laser annealing.

Effects of Thermal Annealing on ZnO Thin-Film Transistor Characteristics and the Application of Excimer Laser Annealing in Plastic-Based ZnO Thin-Film Transistors

In this paper, we present the effects of thermal annealing and excimer laser annealing (ELA) on the characteristics of zinc-oxide (ZnO) thin-film transistors (TFTs) fabricated by magnetron sputtering at room temperature. The transfer characteristics of the ZnO-TFTs are found to improve with increasing thermal annealing temperature. Results of in situ high-temperature X-ray diffraction and electron back scattered diffraction pattern analyses indicate that this phenomenon arises from the crystallization of a low-crystallinity region present in as-deposited ZnO films. Almost all low-crystallinity regions crystallize at temperatures above 500 °C. Furthermore, to achieve such high-performance TFTs on flexible plastic substrates, ZnO-TFTs on a plastic substrate were irradiated with an excimer laser to raise the temperature of the ZnO films. Because of the extremely short pulse width of the laser (25 ns), it is possible to selectively increase the temperature of the ZnO with negligible thermal damage to the plastic substrate. The ELA process has enabled us to produce flexible high-performance ZnO-TFTs with a field-effect mobility of 12 cm2 V-1 s-1.

Excimer Laser Annealing Effects of Silicon-Rich Silicon Nitride Films Prepared by Using Catalytic Chemical Vapor Deposition

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Electron microscopy of the barium strontium titanate film structure on Pt-Ti-SiO2-Si substrates after laser annealing

The effect of laser annealing on the structure of barium strontium titanate films prepared through chemical solution deposition has been investigated. It is demonstrated that the effect of laser radiation initiates processes of crystallization and recrystallization in the films and causes amorphization of the outer surface of the film.

Structural, magnetic, and transport properties of laser-annealed GaAs:Mn–H

We have investigated the effect of laser annealing on the structural, magnetic, and transport properties of hydrogenated Ga0.96Mn0.04As films. Irradiation with nanosecond laser pulses leads to significant recovery of hole-mediated ferromagnetism in these films. By tuning processing parameters such as laser fluence and number of pulses, one can control the electrical and magnetic properties—namely, resistivity, magnetic coercivity, and remnant magnetization—in the laser-activated region. Ion-beam analysis indicates that the structural integrity of the film is maintained upon hydrogenation and laser annealing with evidence for displacement of substitutional Mn ions toward interstitial sites due to hydrogen-complex formation. Laser annealing results in the relaxation of up to 50% of Mn atoms back to substitutional sites while the Curie temperature recovers to ∼60% of the TC prior to hydrogenation. Subsequent thermal annealing results in full relocation of Mn atoms to substitutional sites, yet the TC remains pinned at ∼60% of its original value, suggesting the formation of a defect complex involving substitutional Mn. Our numerical simulations elucidate the strong interplay between laser processing parameters and Mn–H dissociation.

Effect of laser annealing on the dynamics of hologram recording in self-developed dichromated gelatin layers

The dynamics of hologram recording in self-developed dichromated gelatin layers are analyzed for the case where the emulsion is synthesized using self-development technology with application of high-power IR radiation with a wavelength of 1.06 μm for the laser preexposure annealing of millimeter-thick colloid layers.

Tuning by means of laser annealing of electronic and structural properties of nc-Si/a-Si:H

We report the effect of laser annealing on the structural and electronic properties of nc-Si/a-Si:H samples grown close to the amorphous to nanocrystalline transition. The nc-Si/a-Si:H thin films were produced by low-energy plasma-enhanced chemical vapor deposition through a gas discharge containing SiH 4. The samples were subjected to different laser fluencies and were characterized for changes in their structural and electronic properties via Raman spectroscopy and photoluminescence measurements. The laser annealing effects are twofold: i) the nanocrystalline phase grows, during the laser treatment, respect to the amorphous phase; ii) the photoluminescence spectra show the suppression, after laser annealing, of the frequencies above the crystalline Si band–gap.

The effect of KrF laser annealing within an ultrashort time on metal-alumina-nitride-oxide-silicon-type flash memory devices

The effect of laser annealing (LA) within an ultrashort time on metal-alumina-nitride-oxide-silicon-type flash memory device is investigated. Conventional high-temperature annealing leads to the degrading quality of high-k blocking oxide due to the long annealing time. On the contrary, an optimized LA at an energy of 500 mJ/cm2 can effectively improve the blocking efficiency due to the reduction in leakage current density. Using the results of x-ray photoemission spectroscopy and high-resolution cross-sectional transmission electron microscopy, this improvement was attributed to the minimized decomposition of the Al2O3 layer and the interfacial layer growth between Al2O3 and Si3N4.

Laser Annealing of Implanted Semiconductor Layers – One Bridge to Nano-Processing

About 25years after inventing the laser annealing effects of ion implanted semiconductors a summary of the related physical phenomena is given. The field of application for short and selectively deposited energy pulses in controlled thermally activated processing is critically reviewed with the emphasis on electrical activation of implanted layers. Starting form the energy deposition and continuing to the excited transport phenomena a set of regimes can be described, which allows the classification of the variety of laser annealing methods and their different application. Within the scope of controlled thermally activated processes in nanometer dimensions old phenomena like phase transitions in strong non-equilibrium to create metastable states or producing dissipative structures by nonlinear coupling effects with self-organization are taken into account for device generations beyond 45nm. The challenges and disadvantages of laser annealing methods for planar semiconductor technology will be elaborated with respect to the current progress in laser development.

Laser Annealing on Ti Electrode: Impact on Ti∕HfO[sub 2]∕SiO[sub 2] n-Type MOSFET

Low-thermal-budget processes are required for Ti electrode in the present gate-first n-channel metal-oxide-semiconductor field effect transistor (nMOSFET) applications because of its thermal stability problem. In this article, the effects of laser annealing on Ti electrodes (in HfO 2 /SiO 2 nMOSFET) are discussed. The processes of Ti electrode degradation and HfO 2 crystallization are optimized effectively. HfO 2 /SiO 2 nMOSFET with Ti electrode displayed an effective work function (∼4.26 eV), corresponding to the conduction bandedge and an equivalent oxide thickness of 11.7 A by controlling the laser annealing.

Laser annealing effects on the structural, optical and magnetic properties of sputtered Zn 0.95Co 0.05O thin film

We have used reactive magnetron co-sputtering to grow Zn 0.95Co 0.05O dilute magnetic semiconductor (DMS) on 400 nm thick of (0 0 0 1) Al 2O 3 substrate at 600 °C. After deposition the films were irradiated by ArF excimer laser ( λ = 193 nm, τ = 20 ns) source, with energy density equal to 0.4 J/cm 2 for two shoots. The effects of laser annealing on structural, optical and magnetic properties of Zn 095Co 0.05O thin films on Al 2O 3 substrate were investigated using X-ray diffraction (XRD), IR absorption spectra, Raman spectroscopy, atomic force microscopy (AFM) and SQUID magnetometry. XRD analysis showed that the annealed film is textured with c-axis of the wurtzite structure along the growth direction . The IR absorption spectra of the sample showed three absorptions peaks before and after laser annealing due to the transitions between the crystal-field-split 3d levels of tetrahedral Co 2+ substituting Zn 2+ ions. Raman spectra showed the appearance of an additional mode which is an indicator for incorporation of Co 2+ ions into the ZnO matrix. The roughness R ms value of the film evaluated by AFM decreased after laser annealing indicates a good surface topography. Room temperature magnetization measurements performed by SQUID magnetometry showed the presence of ferromagnetism with a saturation magnetization increased after ArF excimer laser annealing.

Effect of laser annealing on crystallinity of the Si layers in Si/SiO 2 multiple quantum wells

We report on continuous-wave laser induced crystallisation processes occurring in Si/SiO 2 multiple quantum wells (MQW), prepared by remote plasma enhanced chemical vapour deposition of amorphous Si and SiO 2 layers on quartz substrates. The size and the volume fraction of the Si nanocrystals in the layers were estimated employing micro-Raman spectroscopy. It was found that several processes occur in the Si/SiO 2 MQW system upon laser treatment, i.e. amorphous to nanocrystalline conversion, Si oxidation and dissolution of the nanocrystals. The speed of these processes depends on laser power density and the wavelength, as well as on the thickness of Si-rich layers. At optimal laser annealing conditions, it was possible to achieve ∼100% crystallinity for 3, 5 and 10 nm thickness of deposited amorphous Si layers. Crystallization induced variation of the light absorption in the layers can explain the complicated process of Si nanocrystals formation during the laser treatment.