在本研究中，於(001)Si以及(001)SiGe晶片上鍍製 Co/Au/Co三明治薄膜結構進行二矽化鈷(CoSi2)成長與反應機制之研究，並探討不同熱退火溫度對鈷矽化物生成的影響。 在Co/Au/Co/(001)Si試片上，低電阻的CoSi2成核溫度較一般讓CoSi2成長所需的溫度降低了100-190 ℃，此結果可由傳統成核理論加以說明。此外，由二次離子質譜儀(SIMS)與X光能量散佈光譜儀(EDAX)分析結果顯示，在矽化反應過程中，金原子會自原位置處擴散進入CoSi2層及CoSi2晶界中。與Co/Au/(001)Si試片比較，利用Co/Au/Co/(001)Si結構所成長之CoSi2層，無論在CoSi2薄膜表面或是CoSi2/Si界面處的粗糙度都得到明顯的改善。 而在Co/Au/Co/(001)SiGe試片上，經550 ℃退火後已可生成十分平整的CoSi2薄膜。與一般Co/(001)SiGe試片相較，當有金中間層存在時，CoSi2生成溫度可降低200 ℃以上。由XTEM與EDAX分析的結果顯示在矽化反應過程中，僅有少量鍺偏析於CoSi2/(001)SiGe界面處，金原子則擴散進入CoSi2層及CoSi2晶界中。此外，實驗結果顯示利用Co/Au/Co三明治結構在SiGe晶片上生成之CoSi2薄膜，其薄膜之粗糙度受到明顯改善。 由一連串的實驗結果顯示，未來極有可能將Co/Au/Co三明治結構應用在先進的Si與SiGe元件中，於低溫下生成平整的低電阻CoSi2接觸。 The formation and growth mechanism of cobalt silicides in the Co/Au/Co sandwich thin films on (001)Si and (001)SiGe substrate after different heat treatments have been investigated. The nucleation temperature of low-resistivity CoSi2 phase in the Co/Au/Co/(001)Si samples was found to be lowered by about 100-190 ℃ compared to what is usually needed for the growth of CoSi2. The results can be explained in the context of the classical nucleation theory. From EDAX and SIMS analysis, the Au atoms were found to diffuse from their original position to disperse in CoSi2 layer and in the grain boundaries during silicidation reactions. In addition, compared with the Co/Au/(001)Si sample, the surface and interfacial roughness of CoSi2 film was effectively improved by using the Co/Au/Co sandwich structure on (001)Si. In the Co/Au/Co/(001)SiGe samples, an uniform CoSi2 thin film was found to form after annealing at 550 ℃. Compared with the Co/(001)SiGe samples, the present of Au interposing layer was found to decrease the nucleation temperature of CoSi2 by about 200 ℃. From XTEM and EDAX analysis, during silicidation reactions, only a small amount of Ge atoms were found to segregate at the CoSi2/(001)SiGe interface and the Au atoms were found to diffuse into the CoSi2 layer and grain boundaries. In addition, the Co/Au/Co sandwich structure is shown to significantly improve the roughness of CoSi2 thin films grown on SiGe substrate. These results present the exciting prospect that with appropriate controls, the Co/Au/Co sandwich structure promises to be applicable to the formation of uniform and low-resistivity CoSi2 contacts in advanced Si and SiGe devices at low temperature.
