Microstructural interpretation of Ni ohmic contact on n-type 4H-SiC
Microstructural interpretation of Ni ohmic contact on n-type 4H-SiC
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DOI：
10.1116/1.1495506
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发表时间：
2002-07-01
影响因子：
1.4
通讯作者：
Lee, JL
中科院分区：
文献类型：
--
作者：
Han, SY;Shin, JY;Lee, JL
利用透射电镜（TEM）研究了n型4H-SiC表面Ni触点的微观结构随退火温度的变化。根据这些结果，解释了微观结构变化与电性能之间的相关性。经800℃退火后，形成了由Ni2Si和Ni31Si12组成的硅化物相。从微束衍射结果来看，Ni31Si12仍停留在表面，Ni2Si在接触中占主导地位，表明Ni2Si是通过Si原子的外扩散在界面处开始生长的。当样品在950℃退火时，表现出欧姆行为，层结构转变为富c层/Ni2Si/NiSi/n型SiC。观察NiSi期。这些结果表明，随着退火温度的升高，与SiC界面处的硅化镍中Si的成分增加。对表面石墨相的观察表明，C原子在950度时扩散到表面。这导致碳空位的形成，充当电子的供体。这表明碳空位的产生通过降低电子输运的有效肖特基势垒高度在欧姆接触的形成中起主要作用。(C) 2002年美国真空学会。
Using cross-sectional transmission electron microscopy (TEM), microstructural changes in Ni contacts on n-type 4H-SiC as a function of annealing temperature were investigated. From these results, the correlation between the microstructural change and electrical properties was interpreted. After annealing at 800 degreesC, which yielded rectifying behavior, the silicide phases were formed, composed of Ni2Si and Ni31Si12. From the results shown in microbeam diffraction patterns, Ni31Si12 remains at the surface and Ni2Si is dominant in the contact, indicating that Ni2Si started to grow at the interface through the outdiffusion of Si atoms. When the sample was annealed at 950degreesC, ohmic behavior was shown, and the layer structure was changed to a C-rich layer/Ni2Si/NiSi/n-type SiC. The NiSi phase was observed. These results imply that the composition of Si in nickel silicide at the interface with SiC increased with the increase of annealing temperature. The observation of the graphite phase at the surface indicates that the C atoms diffused out to the surface at 950 degreesC. This leads to the formation of carbon vacancies, acting as donors for electrons. These suggest that the production of carbon vacancies plays a major role in the formation of ohmic contact through the reduction of the effective Schottky barrier height for the transport of electrons. (C) 2002 American Vacuum Society.