| Silicon Carbide(Si C) is a future alternative to silicon for high power, high temperature, high frequency power electronic devices due to its superior properties like a wide bandgap, high breakdown field, a good thermal conductivity and high electron saturation velocity. Si C-based Schottky barrier diode(SBD) has already shown a great potential due to its low on-resistance and high switching speed. Efficient termination structure and suitable process parameters are the key to obtain SBDs in high breakdown voltage.Junction termination extension is one of the efficient terminations with the advantages of high efficiency, small area, easiness to be fabricated,etc.This thesis presents the fabrications of 1700 V 4H-Si C SBD with different terminations, including no termination, field plate(FP) termination, JTE termination and combined termination of FP and JTE. Forward and reverse electrical characteristics have been tested, and the results have verified the effectiveness of designed JTE termination and that the variation of breakdown voltage with the JTE length. Through statistical analysis of breakdown voltage of SBDs with JTE termination and FP+JTE termination, a conclusion can be drawn that the combined termination have shown advantages of higher breakdown voltage and more stability in SBD fabricating process than single JTE termination.Firstly, the reverse characteristics of SBDs with field plate and junction termination extension have been simulated by utilizing Sentaurus-TCAD, based on the epitaxy parameters of SBD in the 1700 V level. Then, to fabricate SBD devices, JTE doping concentration has been designed based on twice ion implantation simulated by Trim. Layouts are designed, including devices with no termination, JTE termination, FP(field plate) termination,FP+JTE termination and devices to measure CV characteristics, meanwhile, in order to verify the effects of JTE’s length on reverse electrical characteristics, different JTE lengths are designed, from 20μm to 100μm, step by 20μm.Next,devices are taped out and key processes are supervised and recorded, electrical characteristics for the fabricated devices have been tested. Turn-on voltage, specific on-resistance, ideal factor and barrier height have been extracted, which represent the forward electrical features of devices, likewise, breakdown voltage and reverse leakage current have shown the reverse electrical features. According to the comparison of breakdown voltage distribution of SBDs with JTE termination andFP+JTE termination, higher breakdown voltage and more stability in process is shown in fabricating SBDs with combined termination.Test results show that all the breakdown voltages are deviated from the design. To analyze the reasons, actual doping distribution of the implanted ions have been measured by SIMS, and reverse electrical characteristics of SBD have been simulated once more, for the efficiency of JTE termination is sensitive to JTE’s doping concentration. The results of simulations based on actual doping and different artificial activation rate show that the main reason leading to the low breakdown voltage is the lower ion implantation dosage than the design, meanwhile, the effect of annealing and interface charges may influence the breakdown voltage, too. Despite of these discrepancies, variation of reverse breakdown voltage on the JTE length is verified, which has been proven by the coincidence of tested results and the simulated ones at the activation rate of 70%.In conclusion, the experimental results have proven the function of JTE termination designed and has verified the effect of JTE length on the breakdown voltage, The advantages of higher breakdown voltage and more stability of SBDs with combined termination compared to single JTE termination have been proved by statistical analysis, what is more, the experiences of manufacturing SBD with JTE termination in this experiment will be a valuable reference to the next design and experiment. |
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