CVD Growth And Characterization Of4H-SiC Epilayers

"SiC market is now a real industry, not a niche anymore. Yole Developpement,2011GLOBAL SiC INDUSTRYINTERGRATION AND RESHAPING HA VE STARTED.SKC bought Crysband;Infineon100%bought SiCed;Rohm bought SiCrystal;Fair Child bought TranSiC,Cree and Nippon Steel Corp signed a license agreement of global SiC materials; Power Integration announced$30M investment in SemiSouth's SiC technology.Cree and Rohm, as two top enterprises in semiconductor industry, mass-produced SiC MOSFET in2011, which is expected to spread SiC transistor and boost the SiC industry largely. Nowadays, more and more SiC devices, mainly SBD and MOSFET, have been applied into routine life and industrial production such as inverter air conditioner, motor drive and PV inverter.SiC, as a wide band gap semiconductor, has many outstanding physical and electronic properties such as high breakdown voltage, high electron saturation velocity and high thermal conductivity. It has long been extensively attracting a lot of attentions. However, quite a few problems in the growth of SiC, including polytype inclusion, stacking feults and other dislocations and defects, have been hindering the application of SiC for a long time. On the other hand, CVD has been widely used for the epitaxial growth of SiC due to its numerous advantages in the control of epilayer thickness, doping, growth rate and crystal quality.In this thesis,4H-SiC epilayers were grown on8o off-axis substrate by CVD method. Furthermore, optical microscopy, AFM, CV, FTIR, LTPL and TRPL were used to investigate the surface morphology, doping, thickness and crystal quality, indicating high-quality4H-SiC films have been synthesized. The thesis is focusing on:1. Epitaxy of4H-SiC on8o off-axis substrate by CVD method In this chapter, we have epi-grown4H-SiC on8o off-axis substrate and characterized all the samples by optical microscopy, AFM, FTIR, CV and LTPL. First of all, the influence of growth temperature, C/Si ratio and growth rate on the surface morphology of the epilayers was investigated:it was found the surface rougheness decreased significantly with the increase of growth temperature; meanwhile a small increase of surface roughness was noticed when C/Si ratio decreased or growth rate increased. On the other hand, LTPL spectra of all the epilayers were dominated by intense near band gap emission with free excition (FE) related lines and nitrogen bond excition (BE) related lines. Neither donor-acceptor pair (DAP) nor Ti-related luminescences were observed. This indicates SiC epilayers of high crystalline quality have been synthesized.2. The influence of growth temperature on the carrier lifetime of4H-SiC and related defects The influence of growth temperature on carrier lifetime of4H-SiC epilayers was investigated. It was observed that the average carrier lifetime in4H-SiC decreased from350ns to167ns when increasing the growth temperature from1490oC to1610oC. The correlation between Z1/2defect concentration and carrier lifetime indicated Z1/2defect could be a carrier lifetime killer, which determined the average carrier lifetime of4H-SiC epilayer. On the other hand, the comparison between optical microscope image and carrier lifetime mapping showed the local carrier lifetime was significantly reduced by the existence of morphological epitaxial defect.