Papers by Author: Roland Madar

Abstract: In this paper, an overview of the SiC bulk growth processes is given with a special focus on the most recent results related to growth and modeling. In addition, even if SiC growth is a very old topic and that it is now considered as an « industrial development problem », we will show that there are still many open questions of both fundamental and technological importance related to its crystal growth. Process chemistry and surface mechanisms will be more specifically discussed.

Abstract: We present the results of an optical investigation performed using low temperature photomuminescence and Raman spectroscopy on bulk 3C-SiC samples grown with the Continuous-Feed Physical Vapor Transport technique, using a small diameter neck to filter the defects and improve the as-grown material.

Abstract: The Continuous Feed-Physical Vapor Transport Technique (CF-PVT) was optimized by considering the heating, thermal insulation and the geometry of growth cavity. The effects of seeds on the surface morphology of the grown layer have been discussed. We successfully grew 3C-SiC bulk with a diameter of 7.0 mm and 3.3 mm in height with a high growth rate of 0.8 mm/h by the CF-PVT technique.

Abstract: The control of the nucleation step is a critical issue for a future development of 3C-SiC bulk growth. The possibility to get very high quality 3C-SiC single crystal through self-nucleation on graphite was already demonstrated but the large number of nuclei limits the growth of only one crystal. In this study, we have investigated different configurations that help improving the nucleation step. For that, the “necking” stage, well established in Bridgman or Czochralski growth processes, has been successfully applied to the growth of 3C-SiC with the CF-PVT technique. This has allowed getting only one 3C-SiC crystal. The enlarged parts, after having passed the neck, are of high structural quality.

Abstract: The dislocation-induced birefringence of Silicon Carbide (SiC) is analytically and quantitatively modelled by using the adequate SiC data. A good agreement can be obtained between theory and experiment, provided that a background residual (uniaxial) stress is added to the local dislocation-induced stress. Observations are compatible with or predictable from the Burgers vector values, so that birefringence reveals an interesting tool for probing the nature of the dislocations associated, e.g., to micropipes, also faster than and complementary to the more involved transmission electron microscopy (TEM) technique.

Abstract: The main problem for the development of 3C-SiC electronics is the lack of an adapted bulk growth process. The seeded sublimation method is not very adapted for the 3C polytype because of the solid-state transition from cubic to hexagonal that occurs at high temperature (above 1800°C). In this paper, we propose a new experimental set-up for the development of a solution route for the growth of high quality 3C-SiC crystals. By a coupled approach involving experiments and global process modeling, we have addressed the problems of dissolution and crystallization, elimination of parasitic nucleation and stabilization of the growth front. With an appropriate control of the different convection mechanisms, a stable growth front is demonstrated, with a growth rate of a few tens of µm/h at 1650°C. Further improvements and potentialities of this approach are discussed.

Abstract: The conditions to succeed in growing 3C-SiC single crystals are first, make available large 3C-SiC seeds and second, develop a suitable growth process. In this paper, we will address those two issues by reviewing the most recent results in the field. Nucleation, growth, structural quality and doping results will be presented. New insights on 3C bulk growth will be discussed with respect to a future development of real bulk 3C-SiC ingots.

Abstract: We have investigated through birefringence microscopy, a set of 3C-SiC crystals grown with the CF-PVT process, starting from different seeds and under different growth conditions. Through self nucleation experiments, the stable growth of very high quality 3C-SiC crystals at high temperature (2100°C) and at high rate (roughly 0.2 mm/h) is demonstrated. The possibility to develop bulk growth of 3C-SiC crystals is discussed.

Abstract: Modeling and simulation of the SiC growth processes, Physical Vapor Transport (PVT), Chemical Vapor Deposition (CVD), are sufficiently mature to help building new process equipment or up-scaling old ones. It is possible (i) to simulate accurately temperature and deposition distributions, as well as doping (ii) to quantify the limiting phenomena, (iii) to understand the important role of different precursors in CVD and hydrogen additions in PVT. The first conclusion of this paper is the importance of the "effective" C/Si ratio during CVD epitaxy in hot-wall reactors and its capability to explain the doping concentrations. The second conclusion is the influence of the C/Si ratio in alternative bulk growth technique involving gas additions.

Abstract: QuaSiC TM substrates can be obtained by transferring a single crystal SiC layer onto a poly SiC substrate using the Smart Cut TM technology. In order to overcome the difficulty of limited thickness, an important improvement has been demonstrated, which consists in obtaining thick SiC structure by growing epitaxial SiC layers on top of transferred layers. The aim of this work is a structural analysis of such layers by Transmission Electron Microscopy and Photoluminescence.