Akiko Kobayashi

Optimization of copper CVD film properties using the precursor of Cu(hfac)(tmvs) with variations of additive content

It has been found that CVD copper film properties are strongly influenced by their precursor constitution. Pure trimethylvinylsilyl hexafluoro-acethylacetonate copper (Cu(hfac)(tmvs)) was a commonly used precursor in the past but was replaced by a blend precursor due to its poor thermal stability at room temperature. A typical blend precursor of Cu(hfac)(tmvs) contains additives of 5 wt% trimethylvinylsilane (tmvs) and 0.4 wt% hexafluoroacetylacetone dihydrate (Hhfac/spl middot/2H/sub 2/O), in which tmvs is used to stabilize the processor while Hhfac/spl middot/2H/sub 2/O is used to activate the precursor. We have found that Cu CVD film properties are very sensitive to the Hhfac/spl middot/2H/sub 2/O content. CVD copper films deposited using a Cu(hfac)(tmvs) blend precursor containing 5 wt% tmvs without addition of Hhfac/spl middot/2H/sub 2/O showed rough particulate accumulation, while films deposited using a typical blend precursor showed a smooth surface but high resistivity and high impurities. A further problem was micro-voids formed in the film using the typical blend precursor. Good quality CVD Cu films without micro-voids could be obtained by optimizing precursor Hhfac/spl middot/2H/sub 2/O content to within a range from 0.01 to 0.1 wt%. The formation of micro-voids seems to result from excess Hhfac/spl middot/2H/sub 2/O in the precursor. A similar phenomenon was observed in films when water vapor is delivered into the CVD reactor chamber during Cu deposition, which can be interpreted by generation of Hhfac from hydrolysis of Cu(hfac)(tmvs) in the presence of water. Films with good properties without micro-voids were obtained by controlling the water vapor delivery period.

Uniform (111) textured Cu CVD on vacuum annealed Cu seed layer

The vacuum anneal effects of the Cu seed on Cu CVD have been investigated. The vacuum anneal removes the surface oxide of the air-exposed Cu seed and enhances the (111) texture of the seed. The incubation period which has been observed with the air-exposed Cu seed has been eliminated by the vacuum anneal and better film morphology and improved sheet resistance uniformity has been obtained. Epitaxial CVD has been observed on the vacuum annealed seed and led to the enhanced (111) texture.