Influence Of N Implantation On The 4H-SiC MOS Interface

As a significant new wide-gap semiconductor marterial, SiC has been treated as s substitution for a silicon material for its excellent performance under high temperature, high power and high pressure. Most importantly, SiO2 can be thermally grown on SiC, similarly to Si, which makes device on the SiC possible using the current ability of Si techniques and save the cost of R&D. So the research of the SiC marterial is of great significance. One of the problems of SiC development is that there are many states at the interface of SiC, much higher than that of Si/SiO2 MOS. At now, the research of the SiC material is not enough. This paper explores the influence of ion implantation on the interface of SiC MOS combining the simulation, process experiment and testing.This paper aims at reducing the interface states density of 4H-SiC MOS by ion implantation based on the current process. N induced by the ion implantation will be redistributed during the oxidation process and gather at the interface, and N at the interface will form Si-N/N-O band, broke the stable Si1-xCxO2, and slow down the interface stress, thus reducing the interface states density. Based on the current process, four samples are made:sample by wet oxidation and annealing in N2; sample by ion implantation (15 KeV/2×1012 cm-2), wet oxidation and annealing in N2; sample by ion implantation (15 KeV/1.5×1013 cm-2), wet oxidation and annealing in N2; sample by ion implantation (5 KeV/1×1015 cm-2), wet oxidation and annealing in N2.AFM, ellipsometry, C-V test are conducted to measure the result. The result shows that, 1) with the same ion implant energy, the higher ion implant dose corresponds to larger RMS; 2) with the same ion implant energy, the higher ion implant dose corresponds to more N in 4H-SiC epilayer, thus increasing the oxidation rate; 3) with the same ion implant energy, the higher ion implant dose corresponds to lower interface states density; 4) Terman is used to calculate the interface state density. Ion implantation which makes low amount of N in oxide and high N concentration at the SiC/SiO2 interface can reduce the interface state density effectively, as low as 1011 cm-2V-1. Besides, the higher dose corresponds to lower interface state density but more negative flat band voltage.5) Ion implantation which makes low amount of N in oxide and high N concentration at the SiC/SiO2 interface is more effective to reduce the interface state density than ion implantation which makes high amount of N in oxide and low N concentration at the SiC/SiO2 interface. So the experiment shows that the N at the SiC/SiO2 interface is the key to reduce the interface state density.