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 metallizat ion. In this scheme, the intended final structure is composed of two differ ent barrier materials; one is the parent barrier layer (TiN, in our case) a nd the other (Al2O3, in this case) is segregated laterally along the grain boundaries of the parent barrier layer. As a result, the fast diffusion pat hs, the so-called grain boundaries of the parent diffusion barrier, are eff ectively passivated. To realize this type of barrier experimentally, the Ti N(5 nm)/Al(2 nm)/TiN(5 nm) structure was fabricated by sequential sputterin g 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 prevente d 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 Phys ics.