Improved diffusion barrier by stuffing the grain boundaries of TiN with a thin Al interlayer for Cu metallization

A laterally segregated diffusion barrier was investigated for Cu metallization. In this scheme, the intended final structure is composed of two different barrier materials; one is the parent barrier layer (TiN, in our case) and the other (Al2O3, in this case) is segregated laterally along the grain boundaries of the parent barrier layer. As a result, the fast diffusion paths, the so-called grain boundaries of the parent diffusion barrier, are effectively passivated. To realize this type of barrier experimentally, the TiN(5 nm)/Al(2 nm)/TiN(5 nm) structure was fabricated by sequential sputtering and compared with TiN(10 nm) as a diffusion barrier against Cu. The etch pit test results indicated that the barrier with the Al interlayer prevented Cu diffusion into the Si up to 650 degreesC, which is 250 degreesC higher than achieved by a TiN(10 nm) barrier. (C) 2001 American Institute of Physics.