First-principle-based Investigation Of Carbon Cluster On SiC Surface

Most of the traditional integrated circuit technologies using silicon devices are not able to be operated in extreme conditions such as high temperature, high frequency, high power and high radiation. As a material that is potentially well-suited for many extreme conditions operation, much attention has been given to Silicon Carbide (SiC). Although SiC materials have many advantages, the quality of metal/SiC and SiO2/SiC interfaces is hindered by the poor surface properties of SiC. The problems associated with SiC surface such as surface dangling bonds, contamination and the irregular atoms arrangement result in high surface defect density, which seriously limit the development of the SiC devices. Compared with Si, the surface states of SiC are much more complex. A large fraction of carbon contaminants are still left on the SiC surface by the traditional RCA cleaning. In order to reduce surface states caused by C-related contaminants, the SiC surface cleaning methods including high-temperature annealing treatment and RF plasma treatment and electron cyclotron resonance (ECR) microwave plasma treatment were put forward by home and abroad. All these cleaning processes produce positive effect on eliminating C cluster contaminants. Some theoretical researches just made on the passivation of SiC surface dangling bonds. However, the passivation mechanism of carbon clusters which is one of the main defects on SiC surface is still ambiguous, so it is necessary to make further study in theory.In this paper, we investigated the passivation mechanism of the carbon clusters on4H-SiC (0001) surface by using the first principles plane wave pseudopotential method based on density functional theory.3×3×14H-SiC slab model was selected to investigate the thermodynamically stable configuration of C cluster adsorption on SiC surface and study the passivation of the (0001) Si face of SiC by H and N atoms respectively. The calculation results show that the carbon clusters adsorbing at BB site on SiC surface is the most thermodynamically stable configuration, and the core level binding energy shift of the carbon atoms in this structure is close to the experimental data, which demonstrates the reliability of the configuration. C clusters could be effectively passivated by H and N atoms. The passivation results are as follows:(1) Most of C-C contaminants were removed from SiC surface as volatile CxHy species by hydrogenation, and the mechanism of this reaction path is Cx+Hyâ†'CxHy↑;While the few residual carbon atoms on SiC surface interacted with H by forming C-H bonds. And the surface states induced by the C clusters were reduced obviously by H passivation. (2) If SiC surface dangling bonds were passivated by N atoms firstly, the passivation of C-C bond would produce better effect. The most thermodynamically stable structure was5N+3configuration, and the adsorption energy was higher than others. The surface states density of N adsorption systems were also reduced effectively.