Texture analysis of damascene-fabricated Cu lines by x-ray diffraction andelectron backscatter diffraction and its impact on electromigration performance

The texture of electroplated Cu lines of 0.375, 0.5 and 1.5 mu m widths wit h Ta and TiN barrier layers was analyzed using x-ray pole figure and electr on backscatter diffraction (EBSD) techniques. Both techniques indicate a st rong (111) fiber texture relative to the bottom surface of the trench for s amples with a Ta barrier layer and a 400 degrees C, 30 min, postelectroplat ing anneal. Samples with a TiN barrier and no anneal exhibit a weak (111) t exture. For both barrier layers the quality of the texture, as measured by (111) peak intensity, fraction of randomly oriented grains and (111) peak w idth, degrades with decreasing linewidth. EBSD data also indicate (111) tex ture relative to the sidewalls of the trench in samples with a Ta barrier a nd postelectroplating anneal. Electromigration tests at 300 degrees C of 0. 36 mu m damascene Cu lines with the same process conditions show that sampl es with very weak (111) texture have median time to failures that exceed th ose of the strongly textured Cu lines. These results indicate that diffusio n at interfaces, such as the Cu/barrier and Cu/overlayer interfaces, along with diffusion along an electroplating seam play more dominant roles in ele ctromigration failure in damascene-fabricated lines than diffusion along gr ain boundaries within the interconnect. (C) 1999 American Institute of Phys ics. [S0021-8979(99)02905-9].