Papers by Keyword: Defect Density

Abstract: The hot-zone design using an air-pocket was adopted to produce uniform temperature gradient in horizontal direction. In order to investigate the change of temperature gradient toward horizontal direction with growth time, the front shape of SiC growing crystal was measured with different growth stages such as initial, growing and finished stage. While SiC ingot grown in conventional hot-zone design exhibited inhomogeneous growth front in the initial stage of growth and multi facet formation in final stage, which could result in increased defect density, a homogeneous temperature gradient and improved crystal quality was obtained in the modified hot-zone design. Based on the mapping measurement of FWHM (Full width at half maximum) value in X-ray rocking curve, the crystal quality of SiC crystals grown with the modified hot-zone design was observed to be definitely better than conventional design.

Abstract: In the aim of finding the optimal solar cell structure which allows better efficiency, stability and reduced cost, a general study of a Methyl Ammonium lead Iodide CH₃NH₃PbI₃ based perovskite solar cell is made. Three different electron transport material compounds ETMs; TiO₂, ZnO and SnO₂ are comparatively studied considering the same hole transport material HTM, Spiro-OMeTAD. The photovoltaic parameters, i.e. the open circuit voltage (V_oc), the short circuit current (J_sc) and the power conversion efficiency (PCE) are performed considering the ETM layers thicknesses, and the defect densities in both interfaces ETM/Perovskite and Perovskite/HTM. It is found that solar cell with SnO₂ present the highest PCE for almost all configurations. Finally, the optimized cell is simulated with different organic and inorganic HTMs such as PEDOT: PSS, Cul and CuSbS₂.

Abstract: In this work the intrinsic and induced defects related to the mechanical strength of 4H-SiC wafer have been investigated by considering substrates having different dislocation density and subjected to different treatments such as thinning process and high temperature bulk and laser annealing. Three point bending test has been performed on die extracted from the substrates in order to calculate the stress σ the die can withstand at breakage (flexural strength). The variation of intrinsic defect density seems does not act to modify the material flexural strength. Conversely, a considerable correlation between the induced defect density and flexural strength has been found.

Abstract: Mechanical alloying (MA) is a potential processing method for various equilibrium and non-equilibrium alloy phases such as supersaturated solid solution, metastable crystalline, amorphous, quasi-crystalline phases, nanostructures. Compared to conventional high temperature material processing such as melting and casting, improvement of solid solubility limit results from mechanical alloying at room temperature. The solid solubility increases with increase in milling time due to enhanced stress assisted atomic diffusion during particle refinement and reaches a saturation level at higher milling time. The extension of solid solubility is attributed to thermodynamic, dynamic or kinetic factors such as high dislocation density due to severe plastic deformation during particle refinement and enhanced diffusivity during MA. The review aims to discuss the insight of MA than other non-equilibrium processing in terms of achieving higher solubility, reasoning and mechanism of solubility improvement during MA of different alloy systems.

Abstract: This paper analyzed 44 metrics of application level, file level, class level and function level, and do correlation analysis with the number of software defects and defect density, the results show that software metrics have little correlation with the number of software defect, but are correlative with defect density. Through correlation analysis, we selected five metrics that have larger correlation with defect density. On the basis of feature selection, we predicted defect density with 16 machine learning models for 33 actual software projects. The results show that the Spearman rank correlation coefficient (SRCC) between the predicting defect density and the actual defect density based on SVR model is 0.6727, higher than other 15 machine learning models, the model that has the second absolute value of SRCC is IBk model, the SRCC only is-0.3557, the results show that the method based on SVR has the highest prediction accuracy.

Abstract: Spin rinse drying (SRD) and surface tension gradient drying (STG) are used to clean and dry wafers after wet processing. These methods are effective at removing surface fluid and fluid trapped by capillary forces in small (<1um) features. SRD and STG processes combine driven fluid flows with controlled evaporation of thin water films to leave a dry wafer with low defect density (i.e. a low number of physical particle process adders, or areas of haze or oxidation).

Abstract: We explain the experimental improvement in long wavelength response by hydrogen plasma treatment (HPT) in n/i interface. The absorption coefficient of the intrinsic microcrystalline silicon (μc-Si) is decreased in the low energy region (0.8~1.0 eV) by HPT, which indicates a lower defect density in μc-Si layer deposited with HPT than its counterpart without HPT. Simulation by one-dimensional device simulation program for the Analysis of Microelectronic and Photonic Structures (AMPS-1D) shows a higher long wavelength response in μc-Si solar cell if the defect density in intrinsic μc-Si layer is smaller. Our simulation results also disclose that the less defect density in intrinsic layer, the lower recombination rate and the higher electric field is. Higher electric field results in longer drift length which will promote collection of carriers generated by photons with long wavelength. Thus we deduce that HPT decreased defect density in absorber layer and improved the performance of μc-Si solar cells in long wavelength response.

Abstract: The result of positron lifetime measurements of a defected 5251 Al alloy is reported. Positron lifetime is measured as a function of the thickness reduction of the sample which shows a nearly linear increase and then becomes constant; which can be considered to be a reason for the defect movement saturation. The trapping rate, trapping efficiency, trapping cross-section, defect concentration and defect density of positrons are also measured for the sample concerned. The behaviors of these parameters are matched with theoretical calculations. Data are analyzed using the PATFIT88 computer program.

Abstract: Gate oxide shorts (GOS) defect is a critical factor in influencing yield or reliability of the wafer. Due to the conventional test vehicles are not appropriate to collect mass of testing data for GOS defect densities detection and have different manufacture process from the normal transistors resulting in the high testing cost. In this paper, a novel pseudo transistor matrix (PTM) is proposed for GOS density extraction which has almost the same structure as normal transistor. By assuming that GOS are completely independent, the defect density of GOS is extracted from the layout attributes and yield with PTM as a test vehicle to collect mass of testing data. Experimental results show that the extracted GOS defect density is in a good agreement with inline e-test data.

Abstract: We present a survey of the most important factors relating to an epitaxial SiC growth process that is suitable for bipolar power devices. During the last several years, we have advanced our hot-wall SiC epitaxial growth technology to the point that we can support the transition of bipolar power devices from demonstrations to applications. Two major concerns in developing a suitable epitaxial technology are epilayer uniformity and extended defect density. Our state-of-theart capability permits the realization of 1-cm2 area devices with exceptional yields. Another major concern is the stability of bipolar devices during forward conduction. We have developed proprietary substrate and epilayer preparation technologies that have essentially eliminated Vf drift as a significant barrier to the exploitation of SiC based bipolar devices.