A Study of Nitrogen Incorporation in PVT Growth of n+ 4H SiC |
| Journal |
Materials Science Forum (Volumes 527 - 529) |
| Volume |
Silicon Carbide and Related Materials 2005 |
| Edited by |
Robert P. Devaty, David J. Larkin and Stephen E. Saddow |
| Pages |
59-62 |
| DOI |
10.4028/www.scientific.net/MSF.527-529.59 |
| Online since |
October, 2006 |
| Authors |
D.M. Hansen,
Gil Yong Chung,
Mark J. Loboda
|
| Keywords |
4H-SiC, Bulk Growth, Nitrogen, PVT |
| Abstract |
A detailed understanding of the incorporation of N2 gas during PVT growth of SiC is
required to achieve high performance, low resistivity n+ SiC substrates necessary for power device
applications. In this report, nitrogen incorporation is investigated for growth of 4H SiC crystals
from 2” to 3” diameter in conditions ranging from unintentionally doped to low resistivity (0.015 -
cm). For a wafer in a particular boule a resistivity uniformity of ± 5% is typical although the
uniformity decreases when the wafer orientation is cut off axis from the bulk growth direction.
Within a boule growth, the nitrogen incorporation is found to be a function of growth time. As
growth continues, the resistivity of wafers cut further from the seed increases. A typical 3” on axis
sliced wafer has a within wafer resistivity uniformity of 5% compared with an average seed to tail
variation of 10%. Due to the axial resistivity gradient the within wafer resistivity uniformity of off
axis sliced wafers is 8%. These axial and radial gradients are thought to be a function of the
changing C/Si ratio during growth. Nitrogen incorporation as a function of PVT geometry, N2
partial pressure, and growth temperature are investigated and discussed. In particular, nitrogen
incorporation is found to depend on the crucible size and nitrogen partial pressure, but is not
strongly dependent on the absolute growth temperature, for growth temperature ranging over 150°C.
Modeling of PVT growth shows the axial resistivity gradient can be linked with a change in the C/Si
ratio versus time. Trends and N2 gas incorporation behavior will be discussed using resistivity
mapping, SIMS, and Hall effect data. |
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