A laterally segregated diffusion barrier was investigated for Cu metallization. In this scheme, the intended final structure was composed of 2 different barrier materials; one was the parent barrier layer (TiN, in the present case) and the other (Al2O3, in this case) was 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, were effectively passivated. To realize this type of barrier experimentally, the TiN(5nm)/Al(2nm)/TiN(5nm) structure was fabricated by sequential sputtering and compared with TiN(10nm) 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 650C, which was 250C higher than achieved by a TiN(10nm) barrier.

Improved Diffusion Barrier by Stuffing the Grain Boundaries of TiN with a Thin Al Interlayer for Cu Metallization. K.T.Nam, A.Datta, S.H.Kim, K.B.Kim: Applied Physics Letters, 2001, 79[16], 2549-51