Papers by Keyword: Crystal Defects

Abstract: Several defects were analyzed through the manufacturing chain along with their impact on devices. High kill rate of micropipes were seen on both Diodes and MOSFETs as expected. The purity of micropipe detection was found to be affected by the presence of inclusions. Inclusions were successfully sub-classified and separated out from micropipes, based on their location depth from the wafer surface. The effect on devices was found to relate to how deep the inclusion was located, with the ones at the surface having the biggest impact. Various sources of Stacking Faults (SFs) were reported, with Basal Plane Dislocations (BPDs) in the crystal being a major contributor. Higher local densities of BPDs were found to have a more detrimental effect. SFs were sub-classified using the wavelength of each peak. The effect of both overall SFs and each SF sub-type on devices was determined, each sub-type having different effect on the device. Various ways of mitigating the effects of defects and dislocations are demonstrated. Reducing killer defects, SF nucleation probability, and BPDs propagation by epitaxial process optimizations are shown. Resilience up to 3500A/cm² against bipolar degradation is demonstrated by using an engineered buffer layer. Process and device design optimizations show high resiliency against crystal and epi defects and dislocations, with improved yield and lower leakage.

Abstract: Power devices electronics based on Silicon Carbide (SiC) are emerging as a breakthrough technology for various applications. The link between the quality of SiC substrates and device performance has been widely discussed [1]. Smart Cut™ technology offers the opportunity to integrate a high quality SiC layer on a low resistivity handle wafer. Moreover the crystal quality of a single donor wafer can be replicated multiple times to provide an epitaxy-ready substrate in high volume [2]. Nevertheless, some extended grown-in defects of SiC starting material, like micro-pipes or bulk inclusions, may generate surface defects called "Crystal Originated Defects" (COD) on transferred layers. This paper explains how SmartSiC™ defect density can be reduced by limiting the number of extended defects on donor wafers. Specific inspection recipes were developed to monitor the starting material and the replicated engineered substrate: COD root-causes and effects were analyzed. We demonstrated how a well-suited quality control of donor wafers plays a major role to guarantee defect-free SmartSiC™ wafers.

Abstract: The detection and classification of SiC Epitaxial extended defects was refined to separate out defective areas that influence device characteristics. Die level defect localization along with defect area calculations were performed on millions of die across product groups. A clear impact of non-killer defects was observed, especially with increasing density and defective area in the die. Specifically, all types of stacking faults caused higher leakage, lower blocking voltage, and increases in ON resistance and threshold leakage. Furthermore, MOSFET devices were affected to a much larger extent than diode devices. Testing die with higher numbers of defects provides insight on device reliability. Analyzing devices with specific counts of BPDs let us quantify the amount of bipolar degradation caused drift by product/voltage classes.

Abstract: The new relations in kinematics of the magnetoplasticity phenomenon in nonmagnetic materials based on the experimental studies and the computer simulations are presented. The movement of the crystal dislocations, the fundamental crystal defects responsible for plastic deformations, through the random distribution of the point defects, being the obstacles for the motion of the dislocation, is discussed. It is shown that the mean value of the obstacles on the dislocation line does not depend on their concentration C in the sample and the critical dispatching force is proportional to √C.

Abstract: In this work, the detection and characterization of various crystal defects in high doped silicon carbide by photoluminescence (PL) is explored. The detection of basal plane dislocations in high doped epitaxial buffer layers is demonstrated using the near ultraviolet (NUV) spectra. Several characteristic defects in high doped 150mm substrates like grain boundaries and screw dislocations are also detected and characterized using the NUV PL spectra. Further characterization using molten potassium hydroxide etching is presented.

Abstract: As the main substrate materials for solar cell, Czochralskisilicon (CZ-Si) has more crystal defects, higher impurities content and so on, which limit the further improvement of conversion efficiency (h). Floating zone melting silicon (FZ-Si) has excellent performance but the feed rod cost is much higher, so it is hardly used for solar cell widely. To solve this problem, we developed CFZ silicon monocrystal (CFZ-Si). First the poly was made into poly rod withΦ110~Φ130mm by CZ process and then made into CFZ-Si by FZ method. During FZ process, the resistivity is controlled by gas doping and the process is adjustable. CFZ-Si combines advantages of CZ-Si with FZ-Si. It has less crystal defects, lower impurities content especially oxygen content (<0.2 ppm) and excellent consistency of axial resistivity. Meanwhile, poly rod used has lower price and easier fabrication, so CFZ-Si cost is much lower and the further cost reduction is easy. Therefore, CFZ-Si has significant comprehensive advantages and broader prospect in the future photovoltaic field.

Abstract: The growth history of a large diamond crystal synthesized by HPHT temperature gradient method was reconstructed by the defects features in the crystal. The crystal defects were revealed using white synchrotron radiation topography. Dislocations originated from the surfaces of the seed and extended along the directions of <100> were observed within the crystal grown at the early stage. The crystal was then grown to the [00-direction at the middle growing stage and no dislocations were generated at this stage. A lot of dislocation bundles were generated at the last growth stage of the crystal and each bundle was composed of several straight extended dislocations originated from the same point and extended radially within a sector of about thirty degrees centigrade. The origins of the dislocation bundles were distributed near the surface of the crystal. Most of the dislocation bundles were generated near the (-100), (010) and (00-1) and extended to the [-10, [01 and [00-, approximately. The generation of the dislocation bundles was caused by the rapid descent of the temperature in the last growth stage of the diamond crystal.

Abstract: GaN crystals grown in supercritical ammonia by the ammonothermal method were studied by cathodoluminescence (CL), both in image and spectrally resolved modes. The main extended defects and the incorporation of point defects and impurities in different growth sectors were revealed. The influence of the seeds, the role of the growth planes and the changes in the crystal quality during the growth run are discussed.

Abstract: The pyrite in the nature, due to the differences of the semiconductor properties caused by crystal structure and the presence of defects, will be bound to seriously affect the surface state and surface-activity of the mineral, eventually make the process of electrochemical reaction and flotation behavior change in the solution. Starting from the microscopic point of view, this article would study the affect mechanism of crystal structure and defects on the pyrite surface properties and the electrochemical reaction process. Studies have shown, because of the existence of the strong Fe-S covalent bond and determinate equilibrium defects, make the Fermi level and valence state of partial surface element change, accordingly lead to special semiconductor and surface properties of pyrite, ultimately affect the process of pyrite electrochemical flotation.

Abstract: Large-diameter SiC single crystals are grown at II-VI by the sublimation technique. 100mm substrates of semi-insulating 6H SiC and n-type 4H SiC are produced as commercial products; in development, diameter expansion to 125mm has been achieved. Over the last two years, significant improvements have been made in crystal quality. The values of FWHM of x-ray rocking curves are typically 20-40 arc-seconds for 6H SI wafers and 12-30 arc-seconds for 4H n+ wafers. Micropipe density is less than 3 cm-2, and less than 0.1 cm-2 in best substrates. Electrical resistivity of SI substrates is, typically, of 10¹¹ Ω•cm or above. For 4H n+ substrates, the typical dislocation density is about 9×10³ cm^-2 and the typical BPD density is less than 1×10³ cm^-2.