| Abstract |
| 60 nm- and 20 nm-thick hydrogenated amorphous silicon (a-Si:H) layers were deposited on 200 nm SiO2/Si substrates using ICP-CVD (inductively coupled plasma chemical vapor deposition). A 10 nm-Ni layer was then deposited by e-beam evaporation. Finally, 10 nm-Ni/60 nm a-Si:H/200 nm-SiO2/Si and 10 nm-Ni/20 nm a-Si:H/200 nm-SiO2/Si structures were prepared. The samples were annealed by rapid thermal annealing for 40 seconds at 200~500℃ to produce NiSi(x). The resulting changes in sheet resistance, microstructure, phase, chemical composition and surface roughness were examined. The nickel silicide on a 60 nm a-Si:H substrate showed a low sheet resistance at T (temperatures) >450℃. The nickel silicide on the 20 nm a-Si:H substrate showed a low sheet resistance at T>300℃. HRXRD analysis revealed a phase transformation of the nickel silicide on a 60 nm a-Si:H substrate (δ-Ni2Si→ζ-Ni2Si→(NiSi+ζ-Ni2Si)) at annealing temperatures of 300℃→400℃→500℃. The nickel silicide on the 20 nm a-Si:H substrate had a composition of δ-Ni2Si with no secondary phases. Through FE-SEM and TEM analysis, the nickel silicide layer on the 60 nm a-Si:H substrate showed a 60 nm-thick silicide layer with a columnar shape, which contained both residual a-Si:H and Ni2Si layers, regardless of annealing temperatures. The nickel silicide on the 20 nm a-Si:H substrate had a uniform thickness of 40 nm with a columnar shape and no residual silicon. SPM analysis shows that the surface roughness was<1.8 nm regardless of the a-Si:H-thickness. It was confirmed that the low temperature silicide process using a 20 nm a-Si:H substrate is more suitable for thin film transistor (TFT) active layer applications. (Received January 19, 2009) |
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| Key Words |
| Nickel silicide, ICP-CVD, hydrogenated amorphous silicon, nano-thick process, RTA |
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