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The growth rate of 4HSiC epi layers has been increased by a factor 19 (up to 112 m/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. An optimized process without the addition of HCl is reported
for comparison. The Schottky diodes, manufactured on the epitaxial layer grown with the addition
of HCl at 1600 °C, have electrical characteristics comparable with the standard epitaxial process
with the advantage of an epitaxial growth rate three times higher.
Recently several works on high voltage SiC devices with breakdown voltages of about 10 kV have
been published. This voltage capability can be obtained using wide band gap materials like SiC and
consequently there is no competition with silicon power devices. These new devices include: power
DMOSFET [1], implanted VJFET [2], PiN diodes [3] and Schottky diodes [4]. To obtain a
breakdown voltage between 10 and 11 kV an epitaxial layer thickness in the region of 80100 m is
needed. Obviously to obtain this layer thickness with a standard epitaxial growth rate of 68 m/h a
process time of more than ten hours with a consequently high processing cost is required.
The homoepitaxial growth of α has been achieved by chemical vapor deposition (CVD)
methods. The epitaxial growth rate increases proportionally to the
flow but for high
flows
droplets are formed in the gas phase and are then deposited on the wafer [5].
A new epitaxial process that overcomes this limitation has been recently developed [5] and it
represents a breakthrough in the epitaxy process. The growth rate has been increased with respect to
the standard process by increasing the silane flow combined with the introduction of in the
deposition chamber. Now a much higher growth rate (112 m/h) with a good surface morphology
can be obtained. In this paper, 4HSiC epitaxial layers have been grown using both the process with
addition and trichlorosilane () as silicon precursor source together with ethylene as carbon
precursor source. is the typical precursor used in silicon epitaxy for its safety and stability in
industrial processes and should avoid the homogeneous nucleation of silicon droplets in the gas
phase. In fact, the simple replacement of
with
produces a significant alteration of
the species involved in the reaction whose key factor is represented by the shift from to
as
the most important silicon precursor. While the former is the main chemical species responsible for
the homogeneous nucleation of silicon droplets in the gas phase, the latter is very stable and thus
remains available to contribute to the film growth.
Materials Science Forum Vols. 556-557 (2007) pp. 157-160
online at http://www.scientific.net
© (2007) Trans Tech Publications, Switzerland
Online available since 2007/09/15
All rights reserved. No part of 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: 192.167.160.16-22/10/07,16:59:06)