AVS 50th International Symposium
    Manufacturing Science and Technology Monday Sessions
       Session MS-MoM

Paper MS-MoM2
Development of Low Resistance Copper Thin Films Using a Strain Enhanced Grain Growth Technique

Monday, November 3, 2003, 8:40 am, Room 309

Session: Process and Equipment Integration and Development
Presenter: M. Moriyama, Kyoto University, Japan
Authors: M. Moriyama, Kyoto University, Japan
M. Shimada, Kyoto University, Japan
H. Masuda, Kyoto University, Japan
M. Murakami, Kyoto University, Japan
Correspondent: Click to Email
Copper is attractive as interconnect materials of future Si-ULSI (Ultra-Large Scale Integrated) devices with linewidth of less than 100nm. The advantage of using copper (over conventional Al-alloy) as the interconnect materials is that copper has lower electrical resistivity and higher reliability. However, we have serious concern with resistivity of the ultra-narrow Cu interconnects, because the resistivity of interconnects was observed to increase rapidly by reducing the linewidth of the interconnects. The reason is believed to be due to the relatively long mean free path (~39nm) of the conducting electrons of copper. When the linewidth is less than 100nm, the electron scattering by the surface (or interface) and grain boundary becomes dominant, causing significant increase in the resistivity of the copper interconnects. In order to realize nano-scaled Si-devices, development of low resistance ultra-narrow copper interconnects is essential. The purpose of the present experiment was to explore the possibility to prepare low resistivity copper interconnects, which satisfy the designer's requirement, by determine the primary factor (film thickness or mean grain size) which controls the electrical resistivities of copper films. The film microstructures were observed by atomic force microscopy and scanning ion microscopy. The film resistance was measured by a DC four-point probe method. Our experimental result concluded that the grain boundary scattering primarily increased the resistivity of the Cu thin films, indicating that large grained films were essential for low resistivity ultra-narrow copper interconnects. We succeeded to prepare the copper thin films with giant grains by the strain enhanced grain growth technique. This technique will be promising to develop the low resistance copper interconnects for the future Si-ULSI devices.