Study On Plasma Passivation Of Near-interface Oxide Traps And Voltage Stability In SiC MOS Capacitors

Silicon carbide?SiC?semiconductor has excellent physical and electrical properties.It has become the third generation of wide bandgap semiconductors due to its large bandgap width,high thermal conductivity,high breakdown electric field and high saturation drift rate.Widely used in extreme environment such as high temperature,high voltage and high power.At the same time,compared with other semiconductor materials,SiC is the only kind of compound semiconductor material that can grow silicon dioxide?SiO₂?by direct thermal oxidation.Therefore,SiC material is more suitable for processing to form metal-oxide-semiconductor field effect transistors?MOSFET?.However,in practical production and application,the excellent properties of SiC material are not well represented,due to the existence of a large number of defects and traps in the SiO₂ grown in the thermal oxidation process,especially the near-interface oxide layer traps?NIOTs?,the trapping and detrapping behavior under bias temperature stress seriously affects the voltage stability of silicon carbide metal oxide semiconductor?SiC MOS?devices.Therefore,the passivation of NIOTs and the voltage stability of SiC MOS devices have become important issues in the field of SiC MOS devices today.In this work,SiC MOS capacitors were fabricated combine with electron cyclotron resonance?ECR?microwave nitrogen plasma and ECR microwave nitrogen-hydrogen mixed plasma process.The passivation effects of NIOTs in SiC MOS capacitors by two plasma passivation processes were investigated in depth,and the microscopic mechanism of passivation of NIOTs by nitrogen and hydrogen were studied.In order to separate the effects of the oxide trap charges on the curve drift and evaluate the voltage stability of the SiC MOS capacitor,we proposed an improved low-temperature midgap voltage drift method.The experimental results show that the efficiency of passivated NIOTs and the voltage stability of the devices can be improved by increasing the passivation time of ECR microwave nitrogen plasma.However,excessive nitrogen passivation treatment produces deep-level interface and near-interface oxide traps,which cause the samples have a"bulge"phenomenon in the C-V curves under the high temperature negative stress test,thereby reducing the stability of the devices.A small amount of hydrogen in the mixed plasma passivation process can passivate it to solve this problem.The samples subjected to passivation treatment by the ECR nitrogen-hydrogen mixed plasma passivation process have a smaller voltage drift amount and higher device stability than the samples by the nitrogen plasma passivation process.However,the introduction of excess hydrogen also creates additional defects,making the stability of the MOS devices sensitive to the time of ECR nitrogen-hydrogen mixed plasma passivation.However,from the overall performance of the devices,the nitrogen-hydrogen mixed plasma passivation process is more suitable for passivating NIOTs.As long as the mixed plasma passivation time is appropriate,the voltage stability of the devices can be maximized.The above work provides a new idea for passivating NIOTs in SiC MOS capacitors and improving the voltage stability of the devices,which lays a good foundation for further exploring the reliability of devices.