Self-assembled Nano layers 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 degrees 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 x 10(-3)-1.84 Omega-cm(2), 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 cm(2)/V-s, I-on/I-off ratio of 3.78 x 10(6), and specific contact resistance of 1.84 Omega-cm(2), revealing the successful application of the SAM-based diffusion barrier to the S/D contacts of Si devices.