Papers by Keyword: RTA

Abstract: In this work, a comparison of standard bulk 4H-SiC epi wafers and Soitec's SmartSiC™ wafers as well as the influence of RTA processing was conducted. For this, MOS capacitors were processed using thermal gate oxide paired with a polycrystalline gate electrode. Subsequent High temperature steps were avoided until an RTA process was performed on some of these wafers. To investigate the oxide quality on all wafer and process splits, CV-, time-zero dielectric breakdown and constant-current stress time-dependent dielectric breakdown measurements were carried out. For the examination of bulk wafers and SmartSiC™, no relevant differences in terms of yield, oxide quality, interface state density and reliability were found. In contrast, RTA processes seem to create a shift in flat band voltage and also lead to a reduction in oxide lifetime. The V_FB shift could partially, but not completely, be explained by addition activation of dopants in the polysilicon electrode. The influence on the oxide reliability, however, is still unclear.

Abstract: Photodynamic therapy (PDT) is a promising modern method for treatment of oncological, bacterial, fungal and viral diseases. However, its application is limited to diseases with superficial localization since the body tissues are not transparent for visible light. To address this problem and extend PDT application to abdominal diseases, an enhanced method of X-ray photodynamic therapy (XRPDT) is suggested, involving X-ray radiation easily penetrating the body tissues. The implementation of this approach requires the development of a pharmacological drug including a photosensitizer stimulated by visible light to yield active oxygen and a nanosized phosphor converting X-ray radiation into visible light with the wavelength required for the photosensitizer activation. This study is aimed at obtaining X-ray stimulated phosphors with nanosized particles suitable for XRPDT application. For this purpose, Y₂O₃:Eu phosphors were synthesized via hydrothermal processing of the corresponding mixed acetate followed by annealing. To prevent from the undesirable agglomeration of the particles in the course of hydrothermal synthesis and subsequent annealing, different techniques were used, including rapid thermal annealing (RTA), microwave annealing and addition of finely dispersed pyrogenic silica (aerosil) to the phosphor. The microwave annealing was carried out using a special installation including a resonance chamber for maintaining a standing wave of microwave radiation. The performed research allowed the determination of hydrothermal processing optimal duration affording the synthesis of phosphors with the highest luminescence brightness. The application of microwave annealing is found to provide phosphors with a more perfect crystal structure compared with RTA. The developed method of Y₂O₃:Eu phosphor synthesis involving pyrogenic silica addition to the autoclave allowed the preparation of samples with the amorphous structure and significantly reduced the particle size without a considerable decrease in the luminescence brightness. The particle size of the phosphor synthesized with aerosil addition is less than 100 nm that allows its implementation in pharmacological drugs for XRPDT.

Abstract: The preparation of ohmic contact with high stability and low resistance is critical, and the quality of ohmic contact will directly affect the performance of devices as the efficiency, gain and switching speed. In this work, the I-V characteristic of the 4H-SiC devices under rapid thermal annealing and pulsed laser annealing were compared, the pulsed laser annealing process could obtain the lower ohmic contact resistant. The surface morphology, material composition, and elemental analysis were clarified by optical microscopy (OM), X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS), respectively. This research suggests that more Ni₂Si and carbon vacancy can form at the interface under pulsed laser annealing.

Abstract: The application of special nanomaterials is promising for the development of new methods for the diagnostics and treatment of cancer. Photodynamic therapy (PDT) is a well-known and recognized method of cancer treatment. This type of therapy is less carcinogenic and mutagenic compared to radiation and chemotherapy, since the applied photosensitizers do not bind to DNA of the cells. However, currently this technique is only applicable to skin cancer, while its extension to the treatment of abdominal tumors requires the creation of pharmacological drugs for PDT, which along with a photosensitizer include a colloidal solution of nanosized luminescent phosphor emitting visible light with the required wavelength under the influence of infrared, X-ray or γ-radiation, which easily penetrates the body tissues. Since photosensitizers are already available as commercial products, the most important goal is the development of nanosized phosphors providing the required radiation convertion. In this study, the effects of hydrothermal synthesis, duration and the conditions of rapid thermal annealing (RTA) on Y₂O₃:Eu phosphor particle size were studied. The hydrothermal synthesis technique was carried out in two ways: chloride (precipitation from a chloride solution using NaOH and NH₄OH precipitators) and acetate (decomposition of mixed acetate either without a dispersant at 230° C for 24 hours, or using PEG-200 and PEG-2000 as dispersants at 230 °C for 12 hours). The rapid thermal annealing was performed either at 600 °C for 20 minutes, or at 800 °C for 5 minutes. The developed synthetic approaches afforded Y₂O₃:Eu nanosized phosphor samples with the particle size not exceeding 200 nm.

Abstract: An investigation of the electrical and microstructural properties of gold (Au)/p-type silicon (Si) contact was performed as a function of rapid thermal annealing (RTA) temperatures. Au films reacted with Si and produced Au₂Si and Au₃Si phases during the deposition of the films at room temperature. The electrical properties of the Au contact to p-type Si degraded with increasing RTA temperature. Such a degradation of the electrical properties could be associated with the degradation of the surface and interface morphology caused by the formation of Au-silicide clusters. The RTA process at 500 °C led to an increase in the size of the Au-silicide Island. This led to the further degradation of the electrical properties after annealing at 500 °C.

Abstract: Multi-wire sawing process with free abrasive slurry or called multi-wire slurry wire sawing (MW-SWS) process has been popularly adopted in slicing of silicon substrates for solar cell application. However, the chipping or edge cracking of thin thickness as 200 μm of such silicon substrates need to be improved in current mass production. The potential subsurface cracks induced by previous edge grinding or brush polishing of silicon brick may be the main cause. This paper is to develop a rapid thermal annealing (RTA) process for thermal annealing of the surface quality of silicon brick before MR-SWS. In this study, a RTA furnace is designed and used to improve the material property of surface of silicon brick. A quartz crucible is used as heating source with the maximum heated specimen size of 156×156×100 mm (W×H×L). The bulk silicon brick used in this study is selected with a size of 20×10×20 mm (W×H×L) and supplied by the Sino-American Silicon Ltd. (SAS) in Hsinchu, Taiwan. The nitrogen gas is also injected as a protective gas for target heating temperature around 550°C with rapid heating rate of 50°C per second. The micro-Vickers (Akashi MVK-H1) and SEM (JSM-6500F, JOEL) instruments have been used to observe the improvement of rectified material properties of bulk silicon substrate. Experiments of silicon wafers have been first performed for obtaining the recipe of RTA testing and then adjusting for silicon brick testing. Results have been verified by the lower surface hardness and larger crystal grain size after RTA treatment. Furthermore, such treated silicon brick can be further adopted for MW-SWS process to identify the effects of reducing chipping or edge cracking of silicon substrates for solar cell application.

Abstract: We have proposed, prepared, and characterized Pt-inserted Ga-doped ZnO (GZO) transparent electrodes of GZO/Pt/GZO (GPG) multilayers on glass substrates. The GZO and Pt films were in-situ deposited by RF and DC sputtering without breaking vacuum, respectively. The grain structure and deposition rate of the GZO films grown on the Pt insertion layer were different from those of the GZO films sputtered on glass substrates. Pt-inserted GZO electrodes showed remarkably decreased resistivity although the thickness of the Pt layer was as thin as 9 nm. However, the optical transmittance of the GPG electrodes was severely degraded with an increasing thickness of the Pt layer. The structural, optical, and electrical properties of GPG multilayered transparent electrodes were affected by post-annealing conditions such as environment and temperature. That may be associated with an increase in crystallinity and inter-diffusion between Pt and GZO films.

Abstract: The electrical and physical properties of ZnO-CeO₂ thin films on n-type Si (100) substrates have been examined by sol-gel method. In addition, the structures were heat treated at different temperatures from 600 to 700^oC using the RTA (Rapid Thermal Annealing) process and investigated the influence of RTA effect on their properties. The diffraction pattern showed that the deposited films exhibited a polycrystalline microstructure. All films exhibited ZnO-CeO₂ peaks orientation perpendicular to the substrate surface and the grain size with the dependent on annealing temperature. The dependence of the physical and electrical characteristics on various annealing temperatures was investigated.

Abstract: ZrO₂ films were deposited on C-face 4H-SiC substrates by using an RF sputter at a temperature of 200°C. Then, ZrO₂ films were treated with RTA (rapid thermal annealing) process in Argon (Ar) ambient at 600°C, 700°C and 800°C for 4 minutes, respectively. The samples with RTA process show the lower leakage currents. As the measure temperature increases from room temperature (RT) to 150°C, the dielectric breakdown voltage reduces from 3 V to 1 V. The difference between quasi C-V characteristics and high frequency C-V characteristics at 1 MHz becomes larger with increasing RTA temperature. The C-V curves also shift to the left side as the measure temperature increases from RT to 150°C. It also shows the ledge on the C-V curves of samples with RTA at elevated measure temperature.

Abstract: Two getter tests were carried out in order to study the getter efficiency of oxygen precipitates in silicon samples contaminated with low and high Cu concentration. The samples were pre-treated by RTA followed by annealing in the temperature range between 700 °C and 1000 °C for various times in order to establish different concentrations and different sizes of oxygen precipitates in the samples. From the analysis of the results of the normalized inner surface and the gettering efficiency, it was deduced that in highly contaminated samples Cu precipitates more easily at dislocations than at the surface of oxygen precipitates. Contrarily, in the samples contaminated with low Cu concentration the presence of dislocations does not improve the getter efficiency. Cu precipitates were found at the edge of a plate-like precipitate in a sample with low Cu concentration.