The contact resistance reduction of Cu interconnects by optimizing the crystal behavior of Ta/TaN diffusion barrier

作者：Wang Wei Lin^*; Peng Kuo Tzu; Kuo Hsien Chang; Yeh Ming Hsin; Chien Hung Ju; Ying Tzung Hua

来源：Materials Science in Semiconductor Processing, 2014, 27: 860-864.

DOI：10.1016/j.mssp.2014.08.035

• Ta/TaN diffusion barrier
• Plasma
• Cu interconnects
• XRD
• TEM

Ta/TaN bi-layer films, commonly used as diffusion barriers in Cu interconnects, have been deposited by self-ionized plasma system with various plasma conditions in this study. The variations of TaN compositions are revealed by secondary ion mass spectrometer. The structural properties of Ta/TaN films have been systematically investigated by X-ray diffraction patterns and transmission electron microscopy. On amorphous TaN film with low N concentration, Ta film consists of alpha-phase Ta (alpha-Ta) and beta-phase Ta (beta-Ta). The sheet resistance of Ta film with the mixture of alpha-Ta and beta-Ta is decreased by the expansion of alpha-Ta content. The formation of pure alpha-Ta film can be achieved by increasing the N concentration of underlying amorphous TaN film. For alpha-Ta film, the enlargement of grain size can reduce the sheet resistance. In the practical application of Ta/TaN diffusion barrier, Kelvin contact resistance of Cu dual damascene interconnects is successfully reduced by the combination of alpha-Ta film with enlarged grains and amorphous TaN film with high N concentration.

• 出版日期2014-11