Self-assembled nanolayers as interfacial diffusion barriers for thermally stable and low contact resistance Cu source/drain electrode in a-Si:H TFT-LCDs

We demonstrate that mercaptoundecanoic acid (MUA) organic layers enhance adhesion and prevent Cu diffusion in Cu/Si structures; the Cu/MUA/Si structures are thermally stable at 200°C and exhibit strong adhesion of Cu to Si due to the strong chemical interaction of Cu with the S terminal groups as well as to the interaction of Si with the -COOH group of MUA. The specific contact resistance of the Cu/MUA/n+-Si structures is in the range of 6.8×10−3−1.84 Ω-cm2, depending on the dopant concentration of n+-Si. The fabricated Cu/MUA source/drain (S/D) electrode a-Si:H TFTs exhibit an electron mobility of 0.79 cm2/V-s, Ion/Ioff ratio of 3.78 × 106, and specific contact resistance of 1.84 Ω-cm2, revealing the successful application of the SAM-based diffusion barrier to the S/D contacts of Si devices.