Interface annealing characterization of Ti/Al/Au ohmic contacts to p-type 4H-SiC  

作　　者：韩超 张玉明 宋庆文 汤晓燕 郭辉 张义门 杨霏 钮应喜 

机构地区：[1]School of Microelectronics, Xidian University, Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices [2]School of Advanced Materials and Nanotechnology, Xidian University [3]State Grid Smart Grid Research Institute

出　　处：《Journal of Semiconductors》2015年第12期53-61,共9页半导体学报（英文版）

基　　金：supported by the Key Specific Projects of Ministry of Education of China(No.625010101);the Specific Project of the Core Devices(No.2013ZX01001001-004);the Science Project of State Grid(No.SGRI-WD-71-14-004)

摘　　要：Ti/Al/Au ohmic contacts to p-type 4H-SiC in terms of a different annealing time and Ti composition are reported. At 1050 ~C, proper increase in annealing time plays a critical role in the Schottky to ohmic contact conversion. With the optimized annealing time, the contact with a high Ti content yields a lower specific contact resistivity （Pc） of 6.4 × 10^-5 Ω.cm2 compared with the low-Ti contact. The annealed surface morphology and phase resultants were examined by scanning electron microscopy （SEM） and X-ray diffraction （XRD）, respectively. For the better ohmic contact, element distribution and chemical states were qualitatively identified by X-ray photoelectron spectroscopy （XPS） depth analysis. In particular, the presence of C and a Si-related phase was discussed and associated with the change in the surface status of the as-grown epilayer of 4H-SiC during annealing. The results reveal that the out-diffused C and Si atoms, with an approximate atomic ratio of 1 ： 1 in the contact layer, can combine to form an amorphous Si-C state. The polycrystalline graphite instead of an unreacted C cluster in the whole alloyed structure and an extra nanosize graphite flake on the outermost surface of the annealed contact were confirmed by Raman spectroscopy.Ti/Al/Au ohmic contacts to p-type 4H-SiC in terms of a different annealing time and Ti composition are reported. At 1050 ~C, proper increase in annealing time plays a critical role in the Schottky to ohmic contact conversion. With the optimized annealing time, the contact with a high Ti content yields a lower specific contact resistivity （Pc） of 6.4 × 10^-5 Ω.cm2 compared with the low-Ti contact. The annealed surface morphology and phase resultants were examined by scanning electron microscopy （SEM） and X-ray diffraction （XRD）, respectively. For the better ohmic contact, element distribution and chemical states were qualitatively identified by X-ray photoelectron spectroscopy （XPS） depth analysis. In particular, the presence of C and a Si-related phase was discussed and associated with the change in the surface status of the as-grown epilayer of 4H-SiC during annealing. The results reveal that the out-diffused C and Si atoms, with an approximate atomic ratio of 1 ： 1 in the contact layer, can combine to form an amorphous Si-C state. The polycrystalline graphite instead of an unreacted C cluster in the whole alloyed structure and an extra nanosize graphite flake on the outermost surface of the annealed contact were confirmed by Raman spectroscopy.

关 键 词：4H-SIC P-TYPE ohmic contact TITANIUM ALUMINUM GOLD 

分 类 号：TN304.2[电子电信—物理电子学]