A New Process for the Fabrication of SiC Power Devices and Systems on SiCOI (Silicon Carbide On Insulator) Substrates

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A New Process for the Fabrication of SiC Power Devices and Systems on SiCOI (Silicon Carbide On Insulator) Substrates François Templier, Nicolas Daval1, Léa Di Cioccio, Daniel Bourgeat, Fabrice Letertre1, Dominique Planson2, Jean-Pierre Chante2 and Thierry Billon CEA-LETI, 17 rue des Martyrs 38054 Grenoble, France 1 SOITEC Silicon On Insulator Technologies, Parc Technologique des Fontaines 38190 Bernin, France. 2 CEGELY, INSA de Lyon, Bat. Léonard de Vinci, 20 avenue Albert Einstein 69621 Villeurbanne, France. ABSTRACT Feasibility of 4H-SiC epitaxy on SiCOI substrates has been demonstrated, with high quality of obtained layers. Power Schottky diodes were designed and fabricated on these new structures, and exhibited very interesting electrical performance, particularly in reverse mode, with Vbr ~ 1000 V. This technology is very promising for the realization of monolithic SiC power systems. INTRODUCTION After years of promising development, Silicon Carbide power devices are now on the potentially high volume market of discrete components, with the first commercially available Schottky diodes. However, the small size, high cost of SiC substrates are still disadvantages which limit fast expansion of such devices. In another hand, in the field of integrated power systems, SiC hasn’t yet emerged. For power systems, SOI (Silicon On Insulator) substrates can be used for the realization of monolithic circuits such as power amplifiers for automotive audio application, with power range up to ~ 100 W [1]. Considering the low breakdown field (0.3 MV/cm) and rather poor thermal conductivity (1.3 W/cm.K) of Silicon, it seems difficult to forecast higher power with this technology. SiCOI (Silicon Carbide On Insulator) material, made by the Smart Cut process, is a promising substrate for power applications, providing the excellent breakdown field and thermal conductivity of 4H-SiC, on 4-in. or more wafer sizes, which are silicon line compatible. The first demonstration of a SiCOI substrate was made by LETI in 1996 [2]. This first wafer was followed by an active research in order to recover the semiconductor properties of the transferred SiC layer [3]. Nowadays those improvements allow the fabrication of power devices. Recently we presented the first demonstration of power Schottky diodes on 4” SiCOI substrate [4]. The thickness of the SiC transferred layer is in the order of 0.5 µm. By designing an original structure involving a sloped Schottky contact, we targeted a 600 V / 1A rectifier. After full fabrication of the devices on a 4” silicon line, reverse characteristics with Vbr ~ 300 V were obtained, while forward current was much lower (~ 1/100th) than expected. This low current was interpreted as the result of failure in the ohmic contact process step. This first achievement was interesting, however we were convinced that the limited thickness of the transferred layer is not intrinsically very favourable for high current densities. In this paper we present an important improvement for the SiCOI substrates, which consis

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