Morphology Control, Dopant Incorporation, and Selective Epitaxial Growth of 4H-SiC at Low Temperatures Using CH 3 Cl Gro
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0911-B02-02
Morphology Control, Dopant Incorporation, and Selective Epitaxial Growth of 4H-SiC at Low Temperatures Using CH3Cl Growth Precursor Yaroslav Koshka, Bharat Krishnan, Huang-De Lin, and Galyna Melnychuk Department of Electrical and Computer Engineering, Mississippi State University, Mississippi State, MS, 39762
ABSTRACT Low-temperature homoepitaxial growth of 4H-SiC using halo-carbon precursors was further investigated to address the problems limiting increase of the growth rate of the defect-free epilayers at growth temperatures below 13000C. Enhanced etching of Si clusters in the gas phase was achieved by adding HCl during the low-temperature growth. The effective Si/C ratio above the growth surface was increased as a result of reduced depletion of silicon vapor species by cluster condensation, which resulted in drastically improved epilayer morphology and significant increase of the growth rate. Intentional insitu nitrogen doping of epitaxial layers during 13000C growth on Si and C faces revealed more than order of magnitude higher nitrogen donor incorporation in the C-face epitaxial layers. Finally, a feasibility of selective epitaxial growth using low-temperature masking materials such as SiO2 was demonstrated.
INTRODUCTION Previously reported CVD epitaxial growth of high-quality 4H-SiC at temperatures down to and below 13000C using CH3Cl precursor [1] offered a promise of new device applications that could benefit from lower-temperature growth process (e.g., selective epitaxial growth (SEG) using conventional low temperature masking materials). However, the growth rate for specular epilayer surface morphology was limited by silicon vapor condensation and cluster formation in the gas phase and did not exceed 2-2.5 µm/hr in the particular growth system used [2]. Silicon clustering was responsible for depletion of silicon growth species, which complicated control of the effective Si/C ratio at the growth surface. The kinetics of the growth process and the presence of Cl-containing products of CH3Cl decomposition are likely to contribute to significant alleviation of the silicon clustering problem, which is in part responsible for our success in achieving high-quality epitaxial layers at lower temperatures. However, a possibility to further enhance cluster etching is expected. For example, it has been suggested (although not unambiguously proved) that significant droplet etching may take place when HCl is added during SiC homoepitaxy at regular growth temperatures [3,4]. In this work, we highlighted the main results of our efforts to establish feasibility of enhanced etching of Si clusters by providing additional Cl-containing vapor species. In addition, growth of highly doped n-type epitaxial layers at low growth temperatures and a possibility of using SiO2 mask for selective epitaxial growth (SEG) of 4H-SiC mesas were investigated.
EXPERIMENTAL DETAILS 4H-SiC substrates used in this study were commercial wafers from different manufacturers vicinally cut 80 towards the [11-20] direction. Epitaxial
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