High Growth Rate Process in a SiC Horizontal Reactor with HCl Addition: Structural and Electrical Characterization
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0911-B02-01
High Growth Rate Process in a SiC Horizontal Reactor with HCl Addition: Structural and Electrical Characterization Francesco La Via1, Giuseppa Galvagno1, Andrea Firrincieli1, Salvatore Di Franco1, Andrea Severino1, Stefano Leone2, Marco Mauceri2, Giuseppe Pistone2, Giuseppe Abbondanza2, Ferdinando Portuese2, Lucia Calcagno3, and Gaetano Foti3 1 CNR-IMM, Stradale Primosole 50, Catania, 95121, Italy 2 Epitaxial Technology Center, BIC Sicilia - Pantano d'Arci, Catania, 95030, Italy 3 Physics Department, Catania University, Via S. Sofia 64, Catania, 95123, Italy
ABSTRACT The growth rate of 4H-SiC epitaxial layer has been increased by a factor 19 (up to 112
µm/h) with respect to the standard process with the introduction of HCl in the deposition chamber. The epitaxial layers grown with the addition of HCl have been characterized by electrical, optical and structural characterization methods. The effects of different deposition parameters on the epitaxial growth process have been described in detail.. This process can be very promising for high power devices with a breakdown voltage of 10 kV.
INTRODUCTION In 1986 Matsunami et al.1 found that single crystalline 6H-SiC can be grown homoepitaxially on -off -oriented 6H-SiC (0001) at low temperatures (1400-1500 °C). This technique was named “step-controlled epitaxy”, since the politype can be controlled by surface steps existing on off-oriented substrates. Mirror surface is obtained, using this process, for C/Si ratios between 1.4 and 2.5. The growth rate is almost constant with these parameters and increases proportionally to the SiH4 flow rate. For high flow rates Si droplets are formed. The main limitation of this process is the low growth rate (6-7 µm/h) that is correlated to the slow silicon diffusion through the stagnant layer, and to the low Si/H2 ratio that cannot go over 0.05%; otherwise homogeneous nucleation of silicon droplets in the gas phase occurs. In the last years an increasing number of publications on high voltage devices with a breakdown voltage around 10 kV has been reported. This interest is due to the fact that in this range the silicon carbide devices do not suffer the competition with silicon power devices. In all these devices an epitaxial thickness around 80÷100 µm is needed to obtain a breakdown voltage
between 10 and 11 kV. To obtain this large thickness with a standard epitaxial growth rate of 6÷8 µm/h it is necessary a process time of more than ten hours with a high cost of the process. A new epitaxial process that overcomes this limitation and will produce a second breakthrough in the epitaxy process has been recently developed2,3. The growth rate has been increased with respect to the standard process increasing the silane flow with the
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introduction of HCl in the deposition chamber. In this work, the influence of several deposition parameters on the surface morphology, the optical and electrical characteristics of the epitaxial layers grown with the HCl addition have been discussed in detail.
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EXPERIMENT The epitax
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