Silicon Carbide Epitaxy

Recently there are been numerous books written on SiC, which is a demonstration of the importance of this material and its potential impact on society. The majority of these books attempt to cover all the aspects of the technology from the growth, to the processing and the devices. In this book, instead, we will focalize on the epitaxial growth of 4H silicon carbide and on the hetero-epitaxial growth of 3C-SiC on different substrates. I think, in fact, that in the last ten years a large evolution of the epitaxial and hetero-epitaxial processes of silicon carbide has been made. The introduction of chloride precursors, the epitaxial growth on large area substrate with low defect density, the improvement of the surface morphology, the understanding of the CVD reactions and epitaxial mechanisms by advanced simulations are just the main results obtained in the homo-epitaxy process of 4H-SiC. Also in the hetero-epitaxy process of 3C-SiC on different substrates several important steps have been made. A more advanced knowledge on the strain formation during epitaxial growth and on the evolution of different defects has produced a large improvement of the material grown on silicon or on the hexagonal polytipes. After this large progress in the process of SiC epitaxial growth it is time to collect this knowledge in an e-book that can be easily accessible from all the silicon carbide community and that can be a reference point for the future work in this interesting field. Then I have decided to contact all the major experts of this field to write ten chapters on the growth, defects reduction and simulations of both 4H-SiC and 3C-SiC. The structure of the book is the following. After an introduction chapter on the evolution and history of the epitaxial growth of 4H-SiC on large area substrate, the introduction of chlorinated precursors in the epitaxial process is reviewed and explained in detail and the effect of this new process on Schottky diodes characteristics is shown. The improvement of the epitaxy process is strictly related to the improvement of the simulation of the growth that helps the researchers to understand the effect of different parameters on this complex process. Then the third chapter is dedicated to the simulations of the CVD systems, the reaction in the gas phase of the different precursors and the surface reaction models. The fourth chapter shows some important results obtained by simulation on the study of different growth parameters that influence the formation of defects and their evolution both on 4H-SiC and 3C-SiC. Some of these defects and the reduction of costs focus the research toward the reduction of the off-axis angle and finally to growth on an on-axis substrate. Then a chapter is dedicated to this important aspect of the growth and shows all the difficulties and the parameters of the epitaxy process that should be changed to obtain a good material on these substrates. Both homoepitaxy (4H on 4H) and heteroepitaxy (3C on hexagonal substrate) are addressed. Finally the section on the homo-epitaxy of 4H-SiC is finished with a chapter that explain the influence of different process parameters on the formation or the reduction of the principal defects that are observed in the epitaxial layers. The section on the hetero-epitaxy of 3C-SiC starts with a chapter on the growth of 3C-SiC on large area silicon wafers. In this chapter it is described the typical process and the defects and strain that are generated during the growth on this substrate. After this introduction chapter to the hetero-epitaxy problematic, the next chapter show a possible approach for the realization of a bulk 3C-SiC growth by CVD. In this chapter it is shown the effect of different type of defects on the devices and several techniques to reduce this defects to a level compatible with the devices realization. While in the two previous chapters the hetero-epitaxy is realized on a silicon substrate, in the ninth chapter the process is realized on a hexagonal SiC politype. In this way the lattice and thermal mismatch is reduced but is also reduced the diameter of the wafer and the cost of the final wafer is greatly increased. Furthermore in this way only (111) 3C-SiC can be obtained and this can be a problem for the realization of MOSFET devices. Finally, in the last chapter of the e-book, an interesting application of the 3C-SiC material is presented in the field of advanced biomedical devices that could be one of the most interesting applications of 3C-SiC.