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

• Published in: Journal of semiconductors Vol. 36; no. 12; pp. 53 - 61
• Main Author: 韩超 张玉明 宋庆文 汤晓燕 郭辉 张义门 杨霏 钮应喜
• Format: Journal Article
• Language: English
• Published: 01.12.2015
• Subjects: 4H-SiC; Aluminum; Annealing; Contact; Contact resistance; Scanning electron microscopy; Semiconductors; Titanium; X-rays; X射线光电子能谱; 合金结构; 接触特性; 欧姆接触; 退火时间; 钛含量
• ISSN: 1674-4926
• DOI: 10.1088/1674-4926/36/12/123006

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.