Effects of Epitaxial Layer Growth Parameters on the Defect Density and on the Electrical Characteristics of Schottky Diodes F. La Via 1,a , F. Roccaforte 1 , S. Di Franco 1 , A. Ruggiero 2 , L. Neri 2 , R. Reitano 2 , L. Calcagno 2 , G. Foti 2,b , M.Mauceri 3 , S. Leone 3 ,G. Pistone 3 , G. Abbondanza 3,c , G. Abbagnale 4,d G.L. Valente 5 and D. Crippa 5,e . 1 CNR-IMM sezione di Catania, Stradale Primosole 50, 95121 Catania, Italy 2 Physics Department, Catania University, Via S. Sofia 64, 95123 Catania, Italy 3 Epitaxial Technology Center, c/o BIC Sicilia – Pantano d’Arci, 95030 Catania, Italy. 4 STM, Stradale Primosole 50, 95121 Catania, Italy. 5 LPE,Via Falzarego 8, 20021 Bollate (Mi), Italy. e-mail: a francesco.lavia@imm.cnr.it, b gaetano.foti@ct.infn.it, c g.abbondanza@etc-epi.com, d giovanni.abbagnale@st.com, e danilo.crippa@lpe-epi.com Keywords: epitaxial growth, KOH etch, Schottky diodes, DLTS Abstract. The effects of the Si/H 2 ratio on the growth of the epitaxial layer and on the epitaxial defects was studied in detail. A large increase of the growth rate has been observed with the increase of the silicon flux in the CVD reactor. Close to a Si/H 2 ratio of 0.05 % silicon nucleation in the gas phase occurs producing a great amount of silicon particles that precipitate on the wafers. The epitaxial layers grown with a Si/H 2 ratio of 0.03% show a low defect density and a low leakage current of the Schottky diodes realized on these wafers. For these diodes the DLTS spectra show the presence of several peaks at 0.14, 0.75, 1.36 and 1.43 eV. For epitaxial layers grown with higher values of the Si/H 2 ratio and then with an higher growth rate, the leakage current of the Schottky diodes increases considerably. Introduction Silicon carbide (SiC) power devices may offer big advantages with respect to other semiconductor devices because of the outstanding properties of this material, such as a high-critical electric field and a wide bandgap [1]. Recent developments in substrate production by the sublimation technique and epitaxial growth of high quality films by chemical vapour deposition (CVD) [1], enable the production of suitable material for high power devices. In particular, Schottky diodes are quite attractive for power conversion applications requiring high breakdown voltage (> 600 V) and low sheet resistance [2]. Nevertheless even if promising devices have been realized, the characteristics of large area diodes (> 1 mm 2 ) show high reverse current density with respect to the thermoionic emission theory and low yield. This excess of current and the low yield of the large devices can be due to defects present in the epitaxial layer. These defects can be reduced by an accurate study on the CVD reactor geometry and process operation. Regarding the growth rate of SiC epitaxy it has been observed that it is essentially limited by the silicon concentration in the gas source. At the process temperature of 4H-SiC (1500-1600°C) a stagnant layer above the surface is formed that limits the diffusion of silicon and carbon species to the surface. After these species are adsorbed on the surface, they have to move and reach a step before nucleating on a terrace. It has been calculated that gas diffusion through the stagnant layer is slower than adatoms diffusion on the solid surface, besides silicon species diffuse slower than carbon species [3]. Since the total growth rate depends on the slower step of a process, from these calculations it is possible to determine that the SiC growth rate is proportional to the silicon Materials Science Forum Vols. 483-485 (2005) pp. 429-432 online at http://www.scientific.net © 2005 Trans Tech Publications, Switzerland Licensed to - Bologna - Italy La Via (francesco.lavia@imm.cnr.it) - CNR-IMM - Italy All rights reserved. No part of the contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net . (ID: 192.167.160.16-03/02/05,16:18:25)