圆柱靶溅射芯片铜导线中硅盘铜线的均匀度和对称性

Uniformity and symmetry during sputtering of cylindrical targets for copper interconnect

研究开发了一个角系数模型来模拟低气压下圆柱靶溅射沉积铜连线。研究包含靶上不同部位对铜连线的均匀性和对称性的影响，也包含圆柱靶溅射中的再沉积。研究发现下段柱筒的沉积量大，铜膜在硅盘边缘部分的沟槽中对称性好于上段，但硅盘上铜膜的不均匀性也最严重。当上段柱筒距硅盘距离足够远时，上段柱筒的角系数趋势起到部分抵消中段和下段角系数的不均匀趋势，对沉积铜在硅盘上的均匀性起帮助作用。圆柱顶端和柱筒上段需要提高溅射强度以降低再沉积的不良影响。但是提高柱筒上段的溅射强度会对硅盘边缘线路沟槽中的铜膜的对称性产生不良影响。

This study developed a view factor model to simulate the physical vapor deposition of copper interconnect in low pressure conditions using cylindrical targets. The study included the influence of different portions of the target on the film uniformity across the wafer and the film symmetry on the trench sidewalls, and the redeposition of the sputtered copper atoms onto the cylindrical target. It was found that the bottom portion of the cylindrical target has higher deposition rates and better symmetry than the middle and the upper portions, but less uniformity across the wafer. When the upper portion is far enough from the wafer, the trend in film thickness for the upper portion partially balances the trends for the middle and the bottom portions, and this is beneficial to the overall uniformity across the wafer. The redeposition study revealed that increasing sputter intensities of the top and the upper potions of the target could mitigate the nonuniform redeposition for the target but worsen the asymmetry for the film in the trenches at the outer region of the wafer.