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We applied excimer laser annealing (ELA) on indium-zinc oxide (IZO) and IZO/indium-gallium-zinc oxide (IGZO) heterojunction thin-film transistors (TFTs) to improve their electrical characteristics. The IZO and IZO/IGZO heterojunction thin films were prepared by the physical vapor deposition method without any other annealing process. The crystalline state and composition of the as-deposited film and the excimer-laser-annealed films were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy. In order to further enhance the electrical performance of TFT, we constructed a dual-heterojunction TFT structure. The results showed that the field-effect mobility could be improved to 9.8 cm2/V·s. Surprisingly, the device also possessed good optical stability. The electron accumulation at the a-IZO/HfO, HfO/a-IGZO, and a-IGZO/gate insulator (GI) interfaces confirmed the a-IGZO-channel conduction. The dual-heterojunction TFT with IZO/HfO/a-IGZO-assisted ELA provides a guideline for overcoming the trade-off between high mobility (μ) and positive VTh control for stable enhancement mode operation with increased ID. [ABSTRACT FROM AUTHOR]

The need of cheap and easy to use biosensors for rapid diagnostics is a crucial challenge in medicine: indeed, devices must offer multiple properties such as fast response, high sensitivity, reduced need of sample processing, etc. In this respect, optical biosensors remain a promising class of biodevices. Here we present an extensive investigation of the surface properties of silver-coated zinc oxide disordered nanostructures as efficient biosensing platform to detect complex organic profiles via Raman spectroscopy. In particular, we combine low temperature and large area manufacturing techniques to offer a low-cost tool for rapid detection of untreated organic samples like human blood avoiding the usage of expensive manufacturing methods to grow ordered nanostructures and providing safer materials respect the implementation of metal nanoparticles thus opening the possibility to adopt these devices also in vivo. After an accurate study using rhodamine, comparing Raman response for as deposited and lasered surfaces, different metal layers (gold vs silver) and different metal thicknesses (from 25 to 150 nm), we successfully validate the performance of the silver-coated lasered platform on untreated human blood obtaining high resolved response and identifying several organic signatures attributable to hypoxanthine, glucose and lipoprotein.

We applied excimer laser annealing (ELA) on indium-zinc oxide (IZO) and IZO/indium-gallium-zinc oxide (IGZO) heterojunction thin-film transistors (TFTs) to improve their electrical characteristics. The IZO and IZO/IGZO heterojunction thin films were prepared by the physical vapor deposition method without any other annealing process. The crystalline state and composition of the as-deposited film and the excimer-laser-annealed films were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy. In order to further enhance the electrical performance of TFT, we constructed a dual-heterojunction TFT structure. The results showed that the field-effect mobility could be improved to 9.8 cm2/V·s. Surprisingly, the device also possessed good optical stability. The electron accumulation at the a-IZO/HfO, HfO/a-IGZO, and a-IGZO/gate insulator (GI) interfaces confirmed the a-IGZO-channel conduction. The dual-heterojunction TFT with IZO/HfO/a-IGZO-assisted ELA provides a guideline for overcoming the trade-off between high mobility (μ) and positive VTh control for stable enhancement mode operation with increased ID.

The diffusion and the activation of phosphorus in phosphorus and fluorine co-implanted Ge after being annealed by excimer laser are investigated. The results prove that the fluorine element plays an important role in suppressing phosphorus diffusion and enhancing phosphorus activation. Moreover, the rapid thermal annealing process is utilized to evaluate and verify the role of fluorine element. During the initial annealing of co-implanted Ge, it is easier to form high bonding energy F n V m clusters which can stabilize the excess vacancies, resulting in the reduced vacancy-assisted diffusion of phosphorus. The maximum activation concentration of about 4.4 Ă— 1020 cmâˆ'3 with a reduced diffusion length and dopant loss is achieved in co-implanted Ge that is annealed at a tailored laser fluence of 175 mJ/cm2. The combination of excimer laser annealing and co-implantation technique provides a reference and guideline for high level n-type doping in Ge and is beneficial to its applications in the scaled Ge MOSFET technology and other devices. [ABSTRACT FROM AUTHOR]

This letter investigates degradation during alternating current (AC) operations in low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) produced using the selective excimer laser annealing (ELA). Different degrees of degradation, on-current increase and threshold voltage (Vth) shift were observed after AC operation stress in three devices with different ELA energies. Although a higher ELA energy device has a higher on-current, this will lead to higher protrusion and a stronger electrical field in the active layer. This stronger electrical field will cause serious electron trapping in the grain boundary trap (Ntrap), leading to more serious degradation than that found in the lower ELA energy devices. Finally, COMSOL simulations and C-V measurements were executed to verify the physical mechanism. [ABSTRACT FROM AUTHOR]

The effect of electro‐thermal stress on the electrical performance of flexible, low‐temperature polysilicon (LTPS) thin‐film transistors (TFTs) after mechanical‐folding stress aiming to improve the reliability of foldable display backplanes is studied (IG). Herein, for the first time, the significant increase of gate leakage currents upon the negative bias temperature stress (NBTS) or positive bias temperature stress (PBTS) after the out‐folding test on excimer laser annealing (ELA) TFTs is reported. Out‐folding stress increases the drain current, shifts the threshold voltage (ΔVTH) by 2.4 V, and increases the subthreshold swing without affecting the (IG). However, the ΔVTH is 1.8 V upon NBTS, and the negative ΔVTH is −4.7 V upon PBTS after out‐folding stress along with a drastic increase in IG. A thermal annealing at 250 °C for 10 h for the electro‐thermal stressed TFTs after out‐folding is performed, and initial electrical characteristics recovery is achieved; except the abruptly increased IG. These results are correlated with charge trapping at the damaged grain boundary and (GI). A model with moisture/water molecule diffusion through the nanocracks generated by out‐folding is proposed. The ionized charges (H+, OH−) captured at the nanocrack‐induced trap sites in poly‐Si and GI appear to be the origin of abnormal ΔVTH and IG. [ABSTRACT FROM AUTHOR]

This letter investigates degradation after negative bias temperature instability (NBTI) stress applied to LTPS TFTs with different polycrystalline-silicon grain sizes. The initial characteristics of the LTPS TFTs are similar regardless of grain size; however, we observed a different degree of degradation after NBTI depending on grain size. In general, after NBTI, both grain boundary traps and interface traps were generated. We found that the degree of NBTI degradation is dominated by the concentration of grain boundary traps, which themselves are a result of the different grain sizes that occur due to excimer laser annealing energy. At initial, dangling bonds in the grain boundaries and at the interface are passivated by hydrogen atoms, hence the initial characteristics are similar. Since the large grain of poly-Si initially generates more dangling bonds in the grain boundaries, after NBTI, hydrogen depassivation generates more grain boundary traps and causes much more serious degradation in device performance. [ABSTRACT FROM AUTHOR]

The dehydrogenation process, which is one of the important processes for manufacturing low temperature polycrystalline silicon (LTPS) devices in the industry, requires high temperature over 430–470 °C. In this paper, the hydrogen content in the a‐Si film was reduced by excimer laser annealing (ELA) at lower temperature compared with the conventional dehydrogenation process using a furnace. Not only dehydrogenation but also crystallization of a‐Si was performed in the same chamber to make poly‐Si Grain size and shape of poly‐Si seemed similar to those of poly‐Si obtained from the conventional high‐temperature furnace process. A thin film transistor (TFT) with poly‐Si channel was fabricated via this low‐temperature dehydrogenation process, and the characteristic value of the device was enough to drive the display panel. As a result, a 5.46 inch QHD panel was successfully demonstrated. It was confirmed that the optical properties of the fabricated QHD panel were at the same level as compared with control sample, which was fabricated by using the furnace process. We regard that low temperature dehydrogenation using ELA in this research is promising approach for low‐temperature process, such as transparent flexible substrates. [ABSTRACT FROM AUTHOR]

Integration of nanostructures of semiconducting materials such as zinc oxide with flexible substrates represent a great opportunity to obtain unique sensing platform especially for the biomedical market. However, the attractive optical and electrical properties of ZnO are usually obtained by growing or annealing nanostructured films at relative high temperatures (>400 °C), which are not suitable to substrates made of polymeric materials. We demonstrate in this work that high quality ZnO nanostructures can be processed at relative low temperature (<100 °C) by combining low temperature deposition process and XeCl excimer laser (wavelength 308 nm), used to locally anneal and recrystallize ZnO without affecting the underlying polymeric substrate. We obtain unique post-annealed ZnO nanostructures, grown and processed both on rigid and flexible substrates, that show comparable optical and structural properties of ZnO films that are processed at high temperatures. We discuss the effect of the laser energy density on the nanostructure by analyzing the recrystallized ZnO films through photoluminescence and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The crystallization of hydrogenated amorphous silicon (a-Si:H) is essential for improving solar cell efficiency. In this study, we analyzed the crystallization of a-Si:H via excimer laser annealing (ELA) and compared this process with conventional thermal annealing. ELA prevents thermal damage to the substrate while maintaining the melting point temperature. Here, we used xenon monochloride (XeCl), krypton fluoride (KrF), and deep ultra-violet (UV) lasers with wavelengths of 308, 248, and 266 nm, respectively. Laser energy densities and shot counts were varied during ELA for a-Si:H films between 20 and 80 nm thick. All the samples were subjected to forming gas annealing to eliminate the dangling bonds in the film. The ELA samples were compared with samples subjected to thermal annealing performed at 850–950 °C for a-Si:H films of the same thickness. The crystallinity obtained via deep UV laser annealing was similar to that obtained using conventional thermal annealing. The optimal passivation property was achieved when crystallizing a 20 nm thick a-Si:H layer using the XeCl excimer laser at an energy density of 430 mJ/cm2. Thus, deep UV laser annealing exhibits potential for the crystallization of a-Si:H films for TOPCon cell fabrication, as compared to conventional thermal annealing.

We investigated the characteristics of excimer laser-annealed polycrystalline silicon−germanium (poly-Si1−xGex) thin film and thin-film transistor (TFT). The Ge concentration was increased from 0% to 12.3% using a SiH4 and GeH4 gas mixture, and a Si1−xGex thin film was crystallized using different excimer laser densities. We found that the optimum energy density to obtain maximum grain size depends on the Ge content in the poly-Si1−xGex thin film; we also confirmed that the grain size of the poly-Si1−xGex thin film is more sensitive to energy density than the poly-Si thin film. The maximum grain size of the poly-Si1−xGex film was 387.3 nm for a Ge content of 5.1% at the energy density of 420 mJ/cm2. Poly-Si1−xGex TFT with different Ge concentrations was fabricated, and their structural characteristics were analyzed using Raman spectroscopy and atomic force microscopy. The results showed that, as the Ge concentration increased, the electrical characteristics, such as on current and sub-threshold swing, were deteriorated. The electrical characteristics were simulated by varying the density of states in the poly-Si1−xGex. From this density of states (DOS), the defect state distribution connected with Ge concentration could be identified and used as the basic starting point for further analyses of the poly-Si1−xGex TFTs.

By using the spectroscopic ellipsometric technique, we investigated the excimer laser annealing (ELA) effect on the electronic properties of indium tin oxides (ITO) films fabricated by the DC-sputtering method, which is the one of the most commonly known methods for the commercial ITO films. We found that while the ELA process was helpful for enhancing the electronic property of the sputtered films, the degree of the enhancement was not so sizable as the case of the sol-gel films. This result appeared to originate from the difference in the physical properties of the sol-gel and sputtered amorphous films. We also examined the thermal annealing (TA) effect on the sputtered amorphous films in various ambient conditions, and compared their physical properties with those of the TA sol-gel films. [ABSTRACT FROM AUTHOR]

High quality transparent conductive oxides (TCOs) often require a high thermal budget fabrication process. In this study, Excimer Laser Annealing (ELA) at a wavelength of 248 nm has been explored as a processing mechanism to facilitate low thermal budget fabrication of high quality aluminium doped zinc oxide (AZO) thin films. 180 nm thick AZO films were prepared by radio frequency magnetron sputtering at room temperature on fused silica substrates. The effects of the applied RF power and the sputtering pressure on the outcome of ELA at different laser energy densities and number of pulses have been investigated. AZO films deposited with no intentional heating at 180 W, and at 2 mTorr of 0.2% oxygen in argon were selected as the optimum as-deposited films in this work, with a resistivity of 1×10 −3 Ω.cm, and an average visible transmission of 85%. ELA was found to result in noticeably reduced resistivity of 5×10 −4 Ω.cm, and enhancing the average visible transmission to 90% when AZO is processed with 5 pulses at 125 mJ/cm 2 . Therefore, the combination of RF magnetron sputtering and ELA, both low thermal budget and scalable techniques, can provide a viable fabrication route of high quality AZO films for use as transparent electrodes. [ABSTRACT FROM AUTHOR]

Phosphorus that had been implanted into silicon-on-insulator (SOI) substrates was activated using different annealing techniques to investigate phosphorus deactivation at low temperatures. A combination of amorphization and excimer laser annealing (ELA) greatly enhanced phosphorus activation. However, heavy doping with phosphorus reduced the thickness of the amorphous layer. Furnace annealing at 350 °C following ELA induced significant deactivation and the deactivation behavior was similar to that following rapid thermal annealing (RTA). The temperature-dependence of phosphorus deactivation in samples that were implanted with a dose of 5×10 16 cm −2 showed a transition at 400 °C. The deactivation behavior was more sensitive to temperature below 400 °C than above it. Samples with an implantation dose of 5×10 15 cm −2 exhibited only a weak temperature-dependence of deactivation at temperatures above 400 °C, implying that the transition of temperature-dependence is caused by the change of the deactivation mechanism with the phosphorus activation level. [ABSTRACT FROM AUTHOR]

We report on the effect of the excimer laser annealing on the electronic properties of indium tin oxide (ITO) sol–gel films by using spectroscopic ellipsometric technique. We found that the excimer laser annealing effectively induces the crystallization as well as condensation of the sol–gel film. As the laser power increased, the carrier concentration and the relaxation time of photo-annealed films increased, with the bandgap shifting to higher energies. Simultaneously, the extinction coefficient values in the visible region were reduced significantly. We suggest that the excimer laser annealing should be a promising method for low temperature preparation of the ITO film on heat-sensitive substrates via the sol–gel process. [ABSTRACT FROM AUTHOR]

193 nm Excimer laser assisted growth and crystallization of amorphous Si/Ge bilayer patterns with circular structures of 3 μm diameter and around 25 nm total thickness, is presented. Amorphous patterns were grown by Laser induced Chemical Vapor Deposition, using nanostencils as shadow masks and then irradiated with the same laser to induce structural and compositional modifications for producing crystalline SiGe alloys through fast melting/solidification cycles. Compositional and structural analyses demonstrated that pulses of 240 mJ/cm 2 lead to graded SiGe alloys with Si rich discs of 2 μm diameter on top, a buried Ge layer, and Ge rich SiGe rings surrounding each feature, as predicted by previous numerical simulation. [ABSTRACT FROM AUTHOR]

Based on the heat diffusion equation we describe the temperature profile of a silicon nanoparticle thin film on silicon during excimer laser annealing using COMSOL Multiphysics. For this purpose system specific material parameters are determined such as the silicon nanoparticle melting point at 1683 K, the surface reflectivity at 248 nm of 20% and the nanoparticle thermal conductivity between 0.3 and 1.2 W/m K. To validate our model, the simulation results are compared to experimental data obtained by Raman spectroscopy, SEM microscopy and electrochemical capacitance–voltage measurements (ECV). The experimental data are in good agreement with our theoretical findings and support the validity of the model. [ABSTRACT FROM AUTHOR]

A germanium (Ge) n+/p shallow junction photodiode fabricated by a combination of low-temperature preannealing and excimer laser annealing of the phosphorus-implanted p-type Ge is demonstrated. The Ge photodiode shows a high responsivity of 0.48 A/W at the 1.55- \mu \textm wavelength and an extremely low leakage current density of 1 pA/ \mu \textm^2 at room temperature, over two orders of magnitude lower than that of diodes formed by the rapid thermal annealing process. In addition, the reverse leakage current is close to the theoretical limitation of Ge diodes dominated by the ideal carrier diffusion model. The well-controlled dopant profile of the Ge shallow junction should be beneficial for improving the performance of the diodes, which may also be used in making the source and drain of scaled Ge nMOSFET. [ABSTRACT FROM PUBLISHER]

Thin amorphous silicon (a-Si) films were crystallized into polycrystalline silicon (poly-Si) by combining solid phase crystallization (SPC) and subsequent excimer laser annealing (ELA). Then thin film transistors (TFTs) were fabricated by using the poly-Si formed in the single and double excimer laser scanned area. The device performance of the TFTs fabricated with the excimer laser energy density of 230 mJ/cm 2 is almost equal for the single and double scanned area. This observation indicates that the overlapping laser irradiation with the laser energy density below 230 mJ/cm 2 does not change the characteristics of TFTs. Based on this result, we discuss the correlation between performance of active matrix organic light emitting display (AMOLED) panels and excimer laser energy density during ELA for SPC treated and non-treated poly-Si films. [ABSTRACT FROM AUTHOR]

Abstract: The use of a combined excimer (XeCl=308nm) laser annealing (ELA) and chemical etching process (dubbed the “LaText” process) to generate textured ZnO:Al thin films suitable for thin-film silicon photovoltaic applications has been previously shown, but the evolution of the material during the laser annealing and texturing steps has not been thoroughly examined. In this work, we examine in detail the evolution of the properties of room-temperature sputtered ZnO:Al thin films during such a process. We reveal (i) the bulk structural changes induced during laser annealing through X-ray diffraction measurements (XRD) and Raman spectroscopy, (ii) the dramatic changes in surface morphology and macroscopic electronic properties before and after each step of the LaText process, through Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Hall effect measurements, and (iii) the exceptional light scattering properties of these films in both air and in a cell configuration, as measured by optical transmission and reflection measurements. In all, we show that the electronic transport properties in the final state are acceptable for thin film PV applications, and the optical properties are exceptional and demonstrate great potential for light-trapping performance for both a-Si:H and µc-Si:H solar cells. [Copyright &y& Elsevier]

Low-Temperature Polycrystalline Silicon (LTPS) is the enabling backplane technology for AMOLED displays and small to medium sized high-resolution AMLCDs. Recently, Excimer Laser Annealing (ELA) equipment has made significant progress in scaling for cost-effective large-scale production. In this paper, we discuss the key elements of ELA equipment and the recent and future milestones for LTPS on large substrates. [ABSTRACT FROM AUTHOR]

Abstract: We report on the excimer laser annealing (ELA) induced temperature gradients, allowing controlled crystallization and dehydrogenation of boron-doped a-Si:H/nc-Si:H multilayers. Depth of the dehydrogenation and crystallization process has been studied numerically and experimentally, showing that temperatures below the monohydride decomposition can be used and that significant changes of the doping profile can be avoided. Calculation of temperature profiles has been achieved through numerical modeling of the heat conduction differential equation. Increase in the amount of nano-crystals, but not in their size, has been demonstrated by Raman spectroscopy. Effective dehydrogenation and shape of the boron profile have been studied by time of flight secondary ion mass spectroscopy. The relatively low temperature threshold for dehydrogenation, below the monohydride decomposition temperature, has been attributed to both, the large hydrogen content of the original films and the partial crystallization during the ELA process. The results of this study show that UV-laser irradiation is an effective tool to improve crystallinity and dopant activation in p+-nc-Si:H films without damaging the substrate. [Copyright &y& Elsevier]

This paper presents a lateral-transistor test structure for evaluating the effectiveness of surface doping techniques used to fabricate ultrashallow diodes and ohmic contacts. The test structure requires very limited processing, and simple I–V measurements provide a separation of the hole and electron currents across the junction under investigation. The theoretical behavior is verified by Sentaurus simulations. The ability to discern between Schottky-like and pn-junction diodes is demonstrated by the measurement of a series of junctions fabricated by arsenic dopant deposition plus laser annealing. The activation and drive-in of the deposited arsenic is tuned by the laser energy. The anomalous behavior theoretically predicted for very thin, lightly-doped junctions is observed experimentally. Considerations for an optimal design of the test structures are given. [ABSTRACT FROM AUTHOR]

Abstract: We present an enthalpy-based model for pulsed excimer laser annealing of crystalline silicon in the melting regime that integrates into the technology computer-aided design (TCAD) suite Sentaurus Process of Synopsys. The currently one-dimensional model includes laser absorption, a transient simulation of the heat flux, melting of the surface layer, and undercooling during recrystallization. To verify the model, its predictions for a laser pulse with a duration of ∼150ns and a wavelength of 308nm were compared to those of a phase-field implementation of melting laser annealing by La Magna et al. The two models show a good agreement for the melt depth, melt duration, and melt front dynamics. In a second step, model predictions were compared to melt depths extracted from SIMS measurements of ion implanted and excimer-laser-annealed silicon samples. They were found to agree within the experimental error. Variation of the beam parameters indicated a strong influence of laser energy density fluctuations on the melt depth. [Copyright &y& Elsevier]

Abstract: UV excimer laser annealing (UV-ELA) is an alternative annealing process that, during the last few years, has gained enormous importance for the CMOS nano-electronic technologies, with the ability to provide films and alloys with electrical and optical properties to fit the desired device performance. The UV-ELA of amorphous (a-) and/or doped nano-crystalline (nc-) silicon films is based on the rapid (nanoseconds) formation of temperature profiles caused by laser radiation that is absorbed in the material and lead to crystallisation, diffusion in solid or even in liquid phase. To achieve the desired temperature profiles and to optimize the parameters involved in the processing of hydrogenated nanocrystalline silicon (nc-Si:H) films with the UV-ELA, a numerical analysis by finite element method (FEM) of a multilayer structure has been performed. The multilayer structures, consisting of thin alternating a-Si:H(10nm) and n-doped nc-Si:H(60nm) layers, deposited on a glass substrate, has also been experimentally analyzed. Temperature profiles caused by 193nm radiation with 25ns pulse length and energy densities ranging from 50mJ/cm2 to 400mJ/cm2 have been calculated. Numerical results allowed us to estimate the dehydrogenation process of the different layers and the diffusion of phosphorous (P) in Si layers as well as their structural modifications as a function of the applied laser energy density. Numerical results are compared with exhaustive characterization of the experimental results. [Copyright &y& Elsevier]

Abstract: Today, the collection of generated charges is a limiting problem for the realization of UV sensors. Indeed, the native silicon oxide of the surface acts as a region of recombination centers . Then, the sensors exhibit a low sensitivity in the UV wavelengths. An approach to overcome this drawback is the realization of a few nanometers thick passivation layer at the surface by creating an ultra-shallow junction (USJ) with a high activation level. The realization of such junctions requires two steps: first, the implantation of dopants which consists in introducing impurities at the surface of the substrate, then the thermal activation of these dopants to obtain the electrical characteristics of the junction. The Plasma Immersion Ion Implantation (PIII) process allows us to implant dopants in a very thin layer (10–20nm) into the silicon substrate . These impurities are located in interstitial sites in the silicon, and need an activation process to modify the electrical properties of the layer. The step is performed by means of an excimer laser annealing process (ELA) to melt a very thin layer of the silicon substrate and then activate the dopants without diffusion. In the framework of the ALDIP project (Laser Activation of Dopants implanted by Plasma Immersion), IBS Company has developed with its partners a cluster to realize these two steps with industrial production rates and cleanliness. Four-point probe measurements and SIMS analyzes have been used to characterize the junctions realized with this process. We have reached a sheet resistance lower than 500Ω/sq for a junction depth of 29nm and an abruptness of 3nm/dec. Nevertheless, electrical measurements on diodes have revealed a significant leakage current of around 10−5 A/cm2, revealing the presence of defects inside the junction. Light Beam Induced Current (LBIC) characterization has shown that these defects are localized at the edge of the laser beam. [Copyright &y& Elsevier]

Abstract: The structural and morphological transformations of TiO2 nanotube arrays (TNAs) treated by excimer laser annealing (ELA) were investigated as a function of the laser fluence using parallel and tilted modes. Results showed that the crystallinity of the ELA-treated TNAs reached only about 50% relative to that of TNAs treated by furnace anneal at 400°C for 1h. The phase transformation starts from the top surface of the TNAs with surface damage resulting from short penetration depth and limited one-dimensional heat transport from the surface to the bottom under extremely short pulse duration (25ns) of the excimer laser. When a tilted mode was used, the crystallinity of TNAs treated by ELA at 85° was increased to 90% relative to that by the furnace anneal. This can be attributed to the increased area of the laser energy interaction zone and better heat conduction to both ends of the TNAs. [Copyright &y& Elsevier]

Abstract: Excimer laser annealing (ELA) is a widely used technique for producing polycrystalline silicon (poly-Si) thin films. An optical inspection system with simple optical arrangements for rapid measurement of recrystallization results of poly-Si thin films is developed in this study. The recrystallization results after both frontside ELA and backside ELA can be easily visible from the profile of peak power density distribution using the optical inspection system developed with an optimized moving velocity of 0.312mm/s of the specimen. The method of backside ELA is suggested for batch production of low-temperature polycrystalline silicon thin-film transistors due to higher laser beam utilization efficiency and lower surface roughness of poly-Si films. [Copyright &y& Elsevier]

Good-quality ultrashallow n p junctions are formed using 5-keV amorphizing As implantations followed by a single-shot excimer laser anneal for dopant activation. By using an implant that is self-aligned to the contact windows etched in an oxide isolation layer, straightforward processing of the diodes is achieved with postimplantation processing temperatures kept below 400°C. A possible source of junction leakage at the perimeter caused by dip-etch enlargement of the contact window, also confirmed by transmission electron microscopy (TEM) analysis, is identified, and diode performance is improved by increasing the junction/contact window overlap. The optimum performance in terms of low leakage, shallow junctions, and low resistivity is achieved for 30° tilted implants and by applying a thin laser-reflective aluminum layer. This work isolates the minimum requirements for achieving low-leakage diode characteristics. [ABSTRACT FROM AUTHOR]

Abstract: Excimer laser annealing (ELA) is frequently employed to fabricate low-temperature polycrystalline silicon films on glass substrate. The grain size and crystallinity of polycrystalline silicon films are significantly affected by the resolidification behavior during ELA. A real-time in situ time-resolved optical measurement system is developed to record the rapid phase transformation process during ELA. The average solidification velocity of liquid-Si is calculated from these optical spectra using MATLAB and Excel softwares. Field emission scanning electron microscopy images reveal maximum grain size of poly-Si films with a diameter of 1μm, which is obtained in the complete melting regime of both frontside ELA and backside ELA. Recrystallization mechanisms of complete melting of Si thin films in frontside ELA and backside ELA are demonstrated. Resolidification scenarios of partial melting, near-complete melting and complete melting in frontside ELA and backside ELA are proposed. [Copyright &y& Elsevier]

Abstract: Excellent ultra-shallow p+n junctions have been formed by thermally treating the BF2 +-implanted Si samples by excimer laser annealing (ELA) at 300–400mJcm−2 with post low-temperature long-time furnace annealing (FA) at 600°C. A junction with a leakage current density lower than 20nAcm−2 and a sheet resistance smaller than 200Ω□−1 can be well achieved. No considerable dopant diffusion is observed by using this low-thermal-budget annealing process. However, by simply using the ELA treatment at 300–400mJcm−2, the resultant junction shows a leakage current density as high as 104 nAcm−2 and a peripheral leakage current density of 103 nAcm−1. The large junction leakage is primarily due to the leakage current generated within the junction region near the local-oxidation-of-silicon (LOCOS) edge, and which is substantially caused by the ELA treatment. The large peripheral junction leakage current density can be significantly reduced to be about 0.2nAcm−1 after a post low-temperature FA treatment at 600°C. As a result, the scheme that employs ELA treatment with post low-temperature FA treatment would be efficient for forming excellent ultra-shallow p+n junctions at low thermal budget. [Copyright &y& Elsevier]

Abstract: Implementation of plasma doping and nanosecond laser annealing in the non-melt regime has shown to hold great promise for the realization of ultra shallow junctions, designed for the sub 45nm node. This work includes extensive simulation of these two emerging techniques using the Synopsys Sentaurus Process software tool, in direct comparison with experimental data for each step involved in the process. Analytical calculations were performed in order to investigate the interaction of the KrF Excimer Laser Annealing and silicon regarding the temperature gradients induced into silicon and the boron diffusion kinetics. On the other hand, analytically obtained surface temperature profiles of each annealing condition, were used as input to KMC calculations of the boron diffusion and activation behavior. Simulation predictions, in accordance with SIMS measurements revealed very limited dopant profile movement (maximum 2.5nm), combined with high levels of electrical activation close to the maximum theoretically predicted ones. As the results obtained by calculations are in consistency with the experimental, it is evident that the combination of both analytical and Kinetic Monte Carlo tools, allows for sufficient physical understanding of the underlying mechanisms for these advanced process steps. [Copyright &y& Elsevier]

Abstract: XeF excimer laser-induced melting and recrystallization of amorphous silicon was investigated using in situ on-line time-resolved reflection and transmission measurements with a nanosecond time resolution. Explosive crystallization was observed for 900Å thick amorphous silicon on SiO2 deposited on non-alkali glass substrate upon 25ns pulse duration of excimer laser by continuous-wave He-Ne probe laser. Three distinct regrowth regimes were investigated on the basis of various excimer laser fluences. Scanning electron microscopy, Raman spectroscopy and atomic force microscopy were used to evaluate the excimer laser-irradiated region of the sample. Grain size, surface roughness and melt duration as a function of various laser fluences are also determined. [Copyright &y& Elsevier]

Abstract: Rare earth oxides are emerging candidates for gate oxide films as they have high dielectric constants as well as promising crystal and electronic structures. Lanthanum oxide is one of them but, even if many of its properties are known, no data exist in literature on its thermal conductivity. In this work, La2O3 thermal diffusivity has been measured by laser flash technique in the temperature range 300 K–1600 K and, from it, its thermal conductivity has been derived. Thermal diffusivity showed a decreasing trend from 2.7⁎10−6 m2/s to 0.7⁎10−6 m2/s while thermal conductivity decreases from 6 W/m/K to 2.1 W/m/K in the studied temperature range. Results have been applied to the thermal analysis of excimer laser annealing of La2O3/Si and a-Ge/La2O3/c-Si structures. [Copyright &y& Elsevier]

Abstract: A novel low-temperature process for the crystallization of silicon is proposed: excimer laser annealing (ELA) of amorphous silicon (a-Si) with a hydrogen-modulation-doped layer (ELHMD). The effects of hydrogen on low-energy crystallization by conventional ELA and by ELHMD were investigated. As the hydrogen concentration increases, the crystallinity of the polycrystalline silicon prepared at a low-energy density improves. Nucleation is enhanced by the energy of desorption of hydrogen from Si–H2 bonds during melting of the Si. In addition, film exfoliation can be suppressed by using hydrogen-modulation-doped a-Si film. H modulation doping has the effect of controlling the presence of nucleation sites in the direction of the film thickness. [Copyright &y& Elsevier]

Abstract: We have used reactive magnetron co-sputtering to grow Zn0.95Co0.05O dilute magnetic semiconductor (DMS) on 400nm thick of (0001) Al2O3 substrate at 600°C. After deposition the films were irradiated by ArF excimer laser (λ =193nm, τ =20ns) source, with energy density equal to 0.4J/cm2 for two shoots. The effects of laser annealing on structural, optical and magnetic properties of Zn095Co0.05O thin films on Al2O3 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 Co2+ substituting Zn2+ ions. Raman spectra showed the appearance of an additional mode which is an indicator for incorporation of Co2+ 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. [Copyright &y& Elsevier]

Abstract: The application of the striking electrical and optical properties of amorphous and nano-crystalline silicon in photovoltaic, photonic and nano-electronic devices is attracting increasing attention. In particular, its use both on polymeric substrates and in Integrated Circuit technology for the development of enhanced new devices has shown that processing techniques to produce amorphous hydrogenated and nano-crystalline silicon films avoiding high substrate temperatures are of great importance. A promising strategy to achieve this purpose is the combination of Hot-Wire Chemical Vapor Deposition at 150°C with Excimer Laser Annealing, thus maintaining the substrate at relatively low temperature during the complete process. In this work we present a numerical analysis of Excimer Laser Annealing, performed at room temperature, of a multilayer structure of thin alternating a-Si:H and nc-Si films deposited on glass and grown by Hot-Wire Chemical Vapor Deposition. A set of two different layer thicknesses a-Si:H (25nm)/nc-Si (100nm) and a-Si:H (30nm)/nc-Si (60nm) were analysed for a total structure dimension of 900nm. The aim is to determine the probable temperature profile to achieve controlled localized in depth dehydrogenation. Temperature distribution has been calculated inside the multilayer during the irradiation by a 193nm Excimer laser, 20ns pulse length, with energy densities ranging from 50 to 300mJ/cm2. Calculations allowed us to estimate the dehydrogenation effect in the different layers as well as the structural modifications of the same layers as a function of the applied laser energy. The numerical results have been compared to the experimental ones obtained in similar multilayer structures that have been analysed through Raman spectroscopy and TOF-SIMS in depth profiling mode. [Copyright &y& Elsevier]

Abstract: This work gives an overview of the different developments for silicon germanium (Si1−x Ge x ) from a MEMS post-processing perspective. First, the maximum processing temperature that does not introduce any damage or degradation into the standard characteristics of the CMOS driving electronics is specified. Then, the optimal type of silicon and germanium gas sources and deposition technique that results in an economical process are identified. Next, the selection criteria for a low thermal budget doping method and doping species are discussed. Finally, the advantage and disadvantage for the different approaches implemented for enhancing the physical properties of poly Si1−x Ge x at a CMOS backend compatible temperature are highlighted. It is shown that the optimal method depends on the application requirements and the CMOS technology used for realizing the driving electronics. [Copyright &y& Elsevier]