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Low-temperature poly-Si (LTPS) thin films formed by excimer laser annealing (ELA) are used as the channel material for thin film transistors (TFTs), which have an application as switching devices in flat panel displays. It is well known that one of the major problems in TFT manufacturing is the prominent ridges that form on LTPS thin films after ELA due to volume expansion by crystallization, which in turn induces gate leakage current in the TFTs. In this presentation, we report on the use of additional laser irradiation to reduce the height of the ridges and resulting changes in the electrical properties of LTPS-TFTs.

Selective laser annealing system was developed to realize fabrications of low-temperature poly-Si thin-film transistors (TFTs) even for large substrate, while the conventional excimer laser annealing system has the limitation in substrate size due to the difficulty in obtaining uniform beam line. In this paper, this new system was applied to fabricate poly-Si TFTs, using two laser exposure methods such as the static exposure and the scan exposure. Grain size increased as the laser energy density increased, and TFTs with the field-effect mobility larger than 100 cm2V−1s−1 with the ON– OFF ratio of drain current of approximately 106 could be obtained. Furthermore, for the scan exposure, periodic grain structure was observed resulting from the lateral solidification. In this condition, variations of electrical properties of TFT could be reduced compared to the case of the static exposure.

To integrate circuits into the organic light emitting diode displays, it is necessary to fabricate polycrystalline silicon (poly-Si) based thin-film transistors (TFTs) on the glass substrates. In this work we investigated the correlation between the electrical characteristics and the poly-Si morphology of the excimer laser annealed (ELA) TFTs in ultralow oxygen concentrations (~ ppm). The main feature of ELA poly-Si films is the protrusion at grain boundaries that makes the film surface rough. The surface roughness increases with an increasing oxygen concentration during the laser annealing and degrades the TFT characteristics in the on-state as well as the breakdown voltage of the gate insulator, while the off current is independent of process conditions. This result is attributed to the increased oxygen incorporation in the film in the case of an ELA process. Since oxygen increased the defect density in the polysilicon bandgap, controlling the oxygen concentrations in the process chamber helped to improve the performance of the ELA poly-Si TFTs. Based on these results, we discuss the relationship between performance of active matrix organic light emitting display panels and oxygen concentrations during ELA.

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.

The reliability of p-type excimer laser annealing (ELA) poly-Si thin-film transistor (TFTs) under respective pulse gate and drain bias stresses is investigated in this paper. Under the bipolar gate pulse stress, the device exhibits increased on-state current and the degradation is dominated by the dynamic mechanism. Under the negative drain pulse stress, the device also exhibits increased on-state current, but the degradation is dominated by the DC mechanism. Explanations to the observed degradation phenomena are proposed.

This work studies the effect of glass substrate thermal properties on the crystallization behavior and surface topography of polycrystalline silicon (poly-Si) films formed by a XeCl excimer laser annealing of amorphous silicon. Films of 60 nm hydrogenated amorphous silicon (a-Si:H) film were deposited on different glass substrates of varying thermal properties. A 500 nm SiO2 buffer layer was in between the glass and the silicon film. The silicon was crystallized by a XeCl excimer laser. The atomic force microscopy (AFM) and in-plane X-ray diffraction (IPXRD) were used to evaluate the surface topography, the surface roughness, and crystalline in-plane orientation of poly-Si, respectively. Grazing incidence X-ray diffraction (GIXRD) was employed to quantify the residual stress in poly-Si film. The film properties of poly-Si exhibit a small relationship with the glass thermal properties. The higher thermal conductivity of glass retards the poly-Si texture and reduced the residual tensile stress. The higher thermal diffusivity of the glass causes a decline in the poly-Si texture, the surface asymmetry and flatness. A light shield introduced between glass and buffer layer in the low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) structures, further weakens the impact of the glass substrate on excimer laser annealing (ELA) poly-Si properties.

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 x10-3 Ω.cm, and an average visible transmission of 85. ELA was found to result in noticeably reduced resistivity of 5x10-4 Ω.cm, and enhancing the average visible transmission to 90 when AZO is processed with 5 pulses at 125 mJ/cm2. 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.\ud \ud \ud Keywords : Aluminum; Annealing; Budget control; Excimer lasers; Fabrication; Fused silica; Magnetron sputtering; Optical films; Optical properties; Oxide films; Sputtering; Zinc; Zinc oxide, Al-doped zinc oxide; Electrical and optical properties; Excimer laser annealing; Fused silica substrates; Radio frequency magnetron sputtering; rf-Magnetron sputtering; Transparent conductive oxide (TCOs); Transparent conductive oxides, Thin films

Selective laser annealing system was developed, and applied to fabricate low temperature poly-Si thin film transistors. The new system performs the laser annealing only for the selective area of TFT region by adopting micro lens array, which can apply the laser annealing even for large substrate, contrary to the conventional excimer laser annealing system having the limitation in substrate size due to the difficulty in obtaining uniform beam line. In this study, selectively-annealed poly-Si film structure and their TFT performance were investigated. Grain size increased as an increase in the laser energy density, and TFTs with the field effect mobility larger than 100 cm2V−1s−1 with the on-off ratio of drain current of 106 or more could be obtained.

In this article we present the experimental optimization of thermophotovoltaic (TPV) cells fabricated by laser-diffused phosphorous emitters on p-Ge substrates. First, simulations done by PC1D software have helped to guide in the optimization process. Next, the emitter formation has been carried out experimentally by a fast and low thermal budget process based on excimer laser annealing in the melting regime of a phosphosilicate sol-gel layer deposited by spin coating. The n/p junction created has been characterized by Secondary Ion Mass Spectrometry (SIMS) and used to fabricate a TPV cell as a proof of concept.

Two new processes for deep junction formation have been demonstrated with low thermal budget UV excimer laser annealing using the melting regime: (i) in-depth controllable activation after high energy implantation and (ii) diffusion and recrystallization after heavily-doped Si deposition.

The influence of 248-nm KrF excimer laser annealing (ELA) with energy density between 0 and 400 mJ/cm2 on the electrical behavior of indium gallium zinc oxide (InGaZnO) thin-film transistors (TFTs) is investigated. The experimental results show that the saturation mobility and subthreshold swing are improved from 12.4 cm2/Vs and 100 mV/dec without ELA to 17.8 cm2/Vs and 75 mV/dec, respectively, by applying a 300 mJ/cm2 laser pulse after the source/drain deposition, while maintaining an almost unchanged turn-off voltage. Such improvements are attributed to the increase in the oxygen vacancies and reduction in the bulk traps in the InGaZnO channel.

A germanium n + /p shallow junction formed by a combination of low-temperature preannealing (LTPA) and excimer laser annealing at a low fluence of 150 mJ/cm 2 for phosphorus-implanted germanium is demonstrated. The LTPA step plays a critical role in annihilating the implantation damages and significantly suppressing phosphorus diffusion during laser annealing process, resulting in a very small dopant diffusion length with high activation level of phosphorus. A well-behaved Ge n + /p shallow junction diode with a record rectification ratio of ~10 7 and low leakage current density of 8.3 × 10 -5 A/cm 2 is achieved, which is greatly beneficial to the scaled Ge MOSFET technology.

Recent commercial success of high-resolution AMLCDs and AMOLED displays has led to accelerated adoption and scale-up of ELA, the preferred technique for creating LTPS films. Here, key aspects of the process are discussed; in particular, the formation of laser-induced periodic surface structures (LIPSS) and the super-lateral growth (SLG) phenomenon. Also, a novel upright-microscopy technique is described for characterization of ELA-processed films.

This paper presents an Advanced Excimer Laser Annealing (AELA) process for large-sized OLED displays. Achieving good uniformity and performance characteristics of LTPS TFTs using cost-effective processes are important issues for the production of OLED displays. The AELA uses a conventional ELA system, XeCl laser, large optics and positioning stage, with improved processes and existing technology such as a selective crystallization function. The selective crystallization function of the AELA process has been optimized to obtain uniform microstructure of the crystallized Si films at the TFTs and interconnection region. Specifically, the 7/20 (W/L) TFTs via AELA processed Si films have mobility of 73.81 cm2/V-sec, threshold voltage of −2.07 V and sub-threshold swing of 0.40 V/dec. 55″ FHD OLED displays have been fabricated using the AELA process. The advantages and challenges of AELA technology will be further discussed.

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.

High performance and device uniformity n-channel low-temperature poly-silicon (LTPS) bottom-gate (BG) thin film transistors (TFTs) with artificially-controlled lateral grain growth have been performed by excimer laser crystallization (ELC). The BG TFTs (W/L = 1.5 μm/1.5 μm) demonstrate field-effect-mobility of 323 cm2/Vs and high Ion/Ioff of 9.5 × 108. The proposed BG TFTs reveal the superior electrical characteristics, device uniformity, and reliability than conventional top-gate ones.

We introduce a new structure for low-temperature polycrystalline silicon thin-film transistors (TFTs). This bridged-grain structure can reduce the threshold voltage and the subthreshold swing, increase the on-off ratio, and suppress leakage current and kink effect of TFTs significantly. This technique can be applied to all polycrystalline silicon TFTs, including those made by solid-phase crystallization, metal-induced crystallization, metal-induced lateral crystallization, and excimer laser annealing.

Advanced processes for next generation power devices have been studied in this paper. For silicon (Si)-IGBT applications, a near-perfect deep activation of over 4μm depth has been demonstrated in a phosphorous (Ph) doped Si wafer. In addition, progresses of epitaxial regrowth and ohmic contact formation on a silicon-carbide (SiC) wafer have been reported.

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(10 nm) and n-doped nc-Si:H(60 nm) layers, deposited on a glass substrate, has also been experimentally analyzed. Temperature profiles caused by 193 nm radiation with 25 ns pulse length and energy densities ranging from 50 mJ/cm2 to 400 mJ/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., MICINN: Virtuslaser-MAT2008- 02350, Simbio-EUI2008-001177, Xunta de Galicia: CESOLAS- 07REM007V11PR

In this paper, we present an example of a new generation of laser-crystallization approaches that can crystallize Si films for large active-matrix displays at drastically increased effective crystallization rates. The particular scheme presented in this paper is referred to as the advanced excimer-laser-annealing (AELA) method, and it can be readily configured for manufacturing large OLED TVs using various available and field-proven technical components. As in ELA, it is mostly a partial-/near-complete-melting-regime-based crystallization approach; AELA can, however, eventually achieve greater than one order of magnitude increase in the effective rate of crystallization over that of the conventional ELA technique utilizing the same laser source. We discuss in this paper how and why such a dramatic increase can be attained, and some strategical and technological benefits and options that can be entertained regarding, and as a result of the availability of, the AELA technique.

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 0.312 mm/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.

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.

The Au/SnO 2 /n-LTPS MOS Schottky diode prepared on a glass substrate for carbon monoxide (CO) sensing applications is studied. The n-LTPS (n-type low temperature polysilicon) is prepared by excimer laser annealing and PH 3 plasma treatment of an amorphous Si thin film on glass substrate. The developed Schottky diode exhibits a high relative response ratio of ∼546% to 100 ppm CO ambient under condition of 200 °C and −3 V bias. The response ratio is better than the reported SnO 2 based resistive type CO sensors of 100% and 37%, respectively on poly-alumina and glass substrates or comparable to 390% of Pt-AlGaN/GaN Schottky diode CO sensor. Thus, the Au/SnO 2 /n-LTPS Schottky diode has the potential to develop a low cost high performance CO sensor.

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 1 μm, 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.

Excellent ultra-shallow p+n junctions have been formed by thermally treating the BF2+-implanted Si samples by excimer laser annealing (ELA) at 300–400 mJ cm−2 with post low-temperature long-time furnace annealing (FA) at 600 °C. A junction with a leakage current density lower than 20 nA cm−2 and a sheet resistance smaller than 200 Ω □−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 300–400 mJ cm−2, the resultant junction shows a leakage current density as high as 104 nA cm−2 and a peripheral leakage current density of 103 nA cm−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 0.2 nA cm−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.

Plasma doping (PLAD) process using PH3 plasma is presented to fabricate n+/p ultra shallow junction at room temperature. Directly after the PLAD, a pre-annealing has been conducted for 5 min at 500 {degree sign}C in thermal furnace. ArF excimer laser annealing (ELA) process was then followed with an increment of 20 mJ/cm2 in the laser energy ranging from 400 to 500 mJ/cm2. When the laser energy density was larger than 460 mJ/cm2, a reduced sheet resistance was observed. In order to examine the crystalline defects generated during PLAD, the transmission electron microscopy (TEM) and double crystal X-ray diffraction (DXRD) measurements have been made. With optimized PLAD and ELA conditions, junction depth of 30 nm and sheet resistance of 151.6 Ω/□ could be obtained.

We present different relaxation mechanisms of Ge and SiGe quantum dots under excimer laser annealing. Investigation of the coarsening and relaxation of the dots shows that the strain in Ge dots on Ge films is relaxed by dislocation since there is no interface between the Ge dots and the Ge layer, while the SiGe dots on Si0.77Ge0.23 film relax by lattice distortion to coherent dots, which results from the obvious interface between the SiGe dots and the Si0.77Ge0.23 film. The results are suggested and sustained by Vanderbilt and Wickham's theory, and also demonstrate that no bulk diffusion occurs during the excimer laser annealing.

By the SOP (system-on-panel) technology with laser crystallization process, all the driver circuits required for 6-bit color QVGA (320 × RGB × 240) LCD are integrated on panel. The integrated data driver comprises a new ramp-driven 6-bit DAC. The characteristics and uniformity of the LTPS (low temperature polycrystalline silicon) has been remarkably enhanced by applying multi-shot ELA (excimer laser annealing) process and surface treatment. The characteristics of the poly-Si TFTs for integration of driver circuits are following: (1) in NMOS, V th ∼ 1 V and mobility ∼ 240 cm 2 /V s, (2) in PMOS, V th ∼ −1.8 V and mobility ∼ 100 cm 2 /V s.

A low temperature doping technique to be applied in poly‐Si TFT's on plastic substrates was investigated. Heavily‐doped amorphous silicon layers were deposited on poly‐Si and the dopant atoms were driven in by subsequent excimer laser annealing. The entire process was carried out under a substrate temperature of 120 Ĉ, and a sheet resistance of as low as 300 O/sq. was obtained.

A novel fabrication process for low-temperature (

Two μm long polycrystalline silicon (poly-Si) grains were obtained by irradiating a XeCl excimer laser beam on metal induced laterally crystallized (MILC) poly-Si films due to gradual melting temperature decrease of the MILC poly-Si near the nickel-rich metal induced crystallized (MIC) poly-Si. Poly-Si thin film transistors (TFTs) fabricated by employing the large poly-Si grains, exhibited considerably improved field effect carrier mobility and ON/OFF current ratio compared with conventional MILC and/or excimer laser annealed (ELA) poly-Si TFTs due to reduction of defect density in the poly-Si channel. Our experimental results showed that the combination of ELA and MILC might be beneficial for practical device application.

Formation of shallow junctions has been investigated by using excimer laser annealing in combination with two implantation schemes: BF2-ions at 20 keV and B-ions at low energies (