Void formation in a TiW/AlSiCu metallisation scheme

The voiding behaviour of AlSiCu is described in an TiW/AlSiCu metallization scheme for submicron technology. A direct correlation was found between waiting time between TiW and AlSiCu deposition and voiding. Direct transfer of wafers between the two metal deposition systems enhances voiding. Analysis of the TiW/AlSiCu bilayer with several interface conditions revealed a rather clear correlation to voiding: Interaction between AlSiCu and TiW. It is proposed that the TiW-Al(SiCu) interaction enhances voiding in the AlSiCu interconnection due to formation of intermetallic phases at the Al grain boundaries. Volume effects of intermetallic phase formation enhances local strain at the Al grain boundaries and may initiate void formation.<
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