Papers by Keyword: Epitaxial

Abstract: Electrical Wafer Sorting (EWS) on 12 000, 650 V SiC MOSFETs devices from 7 wafers of 200 mm 4H-SiC are compared with electrical deviations and defectivity of initial epitaxial layers measured using Charge biased non-Contact Voltage imaging, QUAD (Quality Uniformity And Defects), and optical surface detection with PL-imaging, respectively. We successfully demonstrate an increased prediction rate in both KR (kill-ratio) and YI (yield-impact) compared to conventional PL-imaging. It is also shown that QUAD not only supplements PL-imaging but supersedes it predicting failure in some electrical test conditions. We therefore show that the combination of QUAD and PL-imaging results significantly improves the accuracy of device failure prediction by uniquely locating faults in the wafers, and thus, improving foresight of successful device fabrication.

Abstract: Charge biased non-Contact Voltage imaging, QUAD (Quality Uniformity And Defects) is measured on epitaxial layers grown on 25 wafers of 200 [mm] 4H-SiC. Electrical data is analyzed and deviations in the ΔV signal are compared with defectivity observed by the optical surface detection system with UV-PL capability. Reliable statistical data of the relationship between decreasing voltage and defect classification show good detection of triangles and several other defects in the epitaxial layers. The QUAD mapping gives a good first indication of the electrical active defectivity of an epitaxial layer.

Abstract: Homo-epitaxial growth of 4H-SiC on 4^o off-axis 150 mm diameter substrates has been performed in a commercial warm-wall multi-wafer planetary reactor. Based on our well developed 100 mm 4H-SiC epitaxial growth process, which can achieve excellent thickness and doping uniformities (δ/mean) of <1% and <5%, respectively, the growth process and hardware were further fine-tuned and improved for 150 mm 4H-SiC homoepitaxy. After the improvement, the 6 to7 μm thick epilayer uniformity has reached 1.1% with a 5mm edge exclusion while the doping uniformity has improved to 16.5% (<10%) with an edge exclusion of 5 mm (10mm), respectively. Surface roughness of the as-grown 150 mm 4H-SiC epitaxial layer has an RMS value of 0.12 nm scanned by AFM on 20×20 μm² areas. Homo-epitaxial growth on C-face 150 mm 4H-SiC substrates has also been carried out. Other than the doping concentration and uniformity, the other results are very close to the epi-growth on Si-face.

Abstract: Homo-epitaxial growth of 50 μm-thick 4H-SiC on 4° off-axis 100 mm substrates have been demostrated by using a commercial warm-wall multi-wafer planetary reactor (Aixtron 2800 G4). With optimized process, epitaxial layer with an average thickness of 48.146 μm and doping level of 8.39×10¹⁴/cm³ are obtained. The thickness uniformity with an edge exclusion of 5 mm are 1.30% (σ/mean) and 2.17% (max-min/max+min), and the doping level uniformity are 4.66% (σ/mean) and 6.95% (max-min/max+min), respectively. Surface roughness of the as-grown 50 μm-thick epitaxial layer has an RMS value of 0.606 nm with one step bunching on the 20×20 μm² areas. This initial effort on thick 4H-SiC homoepitaxial growth indicates that this comercial multi-wafer planetary reactor has the potential for mass production of SiC epiwafers for 5000 V and above power devices.

Abstract: High-quality La_0.84Sr_0.16Ga_0.26Mg_0.74O_3-δ (LSGM) epitaxial thin films were successfully grown on (100)-SrTiO₃ (STO) substrates at a temperature of 800 °C by a pulsed laser deposition (PLD) method with KrF excimer laser pulses at an ozone pressure of 1.3 × 10³ Pa. X-ray diffraction rocking curve measurements showed that the LSGM films had a full-width at half-maximum (FWHM) value of 0.11 °for out-of-plane 002 reflection, which was smaller than that reported for LaGaO₃ films grown by atomic layer deposition methods (0.18 ^o). The reciprocal spaces mapping of 103 refraction showed that the LSGM films had a slightly larger lattice parameter a (out-of-plane) of 0.393 nm than a_// (in-plane) of 0.391 nm.

Abstract: The wide size distribution of the hexagonal etch pit of screw dislocations (SD) in 4H-SiC wafer was found in spite of the narrow size distribution of the SD pit in epitaxial film. Calculation on the basis of the strain energy equation indicated that etch pit size depends on the Burgers vector and dislocation tilt. Size variation of SD etch pits in 4H-SiC wafer fabricated by sublimation method is explained to be caused by the dislocation tilt by observing the sizes and the positions of etch pits from the surface of the epitaxial film to the inside of 4H-SiC wafer. The SDs in 4H-SiC wafer fabricated by sublimation method propagate to c-axis direction in macroscopic but changing tilt in microscopic.

Abstract: Biosensor diagnostics based on bio-functionalized semiconductor devices are an important development in ultrasensitive sensors for early detection of disease biomarkers. Electrochemical devices using chemically modified graphene (CMG) channels are excellent candidates for nanobiosensors. This paper presents the development of novel antibody functionalized epitaxial graphene devices for bio-sensing applications. Epitaxial graphene has been grown on silicon carbide (SiC) substrates under high vacuum and high temperature conditions (1200 – 1700°C). A generic electrochemical surface functionalisation chemistry, which can be used to attach a variety of “bio-receptors” to graphitic surfaces, has been developed. The attached bio-receptors are capable of specific and selective interaction with disease biomarkers. When a target biomarker molecule interacts with the “bio-receptor” functionalized surface, the charge density at that surface is affected. This change can be detected as an electrical signal from the biosensor, enabling highly sensitive (nM) detection of biomarker analytes. This paper reports the fabrication of graphene channel sensors for detection of disease biomarkers.

Abstract: The III-nitride compounds epitaxially grown on Si substrate have attracted more and more attentions and some progress have been achieved. Many methods have been tried to tackle the issue which caused by the large lattice mismatch and thermal expansion coefficient mismatches between silicon substrate and the III-nitride compounds. This paper presents buffer layer technology, selective area and lateral epitaxial over growth technology, and presents the researches about the III-nitride devices. Semi polar and non-polar GaN films grown on Si (such as Si(110), Si(112), Si(001) et al.) also have been instructed. At the end of this paper, the development trend of epitaxial technology has been discussed.

Abstract: A brief historical overview of one of Hungary's space projects on Soviet spacecrafts, the so-called "Eötvös" Project on semiconductor crystal growth, is given. Three experiments were proposed and performed: i) epitaxial growth of GaAs under flux, ii) seedless growth of GaSb, and as a control, iii) seeded growth of an InSb crystal. Because of thermal control problems of the furnace, only the growth of a structurally perfect GaSb bicrystal was a successful novelty. Results of structural and electrical analyses are briefly summarized. Finally, a list of related publications is given.

Abstract: We investigated electrical properties of epitaxial Mn doped bismuth ferrite BiFe0.97Mn0.03O3 (BFMO) thin films with different crystal orientations deposited on Si substrates with appropriate buffer layers. Epitaxial SrRuO3 (SRO) thin films with (001), (101), and (111) orientations were grown on CeO2/yttria-stabilized zirconia (YSZ)/Si(001) substrates and YSZ/Si(001), respectively, by the insertion of MgO and TiO2 atomic layers using pulsed-laser deposition (PLD). Using spin coating, we deposited BFMO thin films onto orientated SRO thin films. The BFMO orientation followed the SRO orientation. The Pr values of the BFMO were ordered as follows {111}>{110}>{100}, which is the same as that predicted by crystallographic considerations. The largest Pr value of the {111} orientation is 76 μC/cm2 at 100 kHz, 25°C.