Electrodeposition of Cu(111) onto a Ru(0001) seed layer for epitaxial Cu interconnects
Electrodeposition of Cu(111) onto a Ru(0001) seed layer for epitaxial Cu interconnects
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DOI：
10.1063/5.0063418
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发表时间：
2021-10
影响因子：
3.2
通讯作者：
Ryan R. Gusley;Quintin Cumston;K. Coffey;A. West;K. Barmak
中科院分区：
文献类型：
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作者：
Ryan R. Gusley;Quintin Cumston;K. Coffey;A. West;K. Barmak
研究了在含有稀硫酸铜 (II) 和氯离子的硫酸基溶液中将 Cu 电沉积到外延 Ru(0001) 种子层上的情况。使用-350 μA/cm2的恒电流沉积，Cu外延沉积到30 nm厚的Ru(0001)种子层上，尽管压缩失配应变在-6.9%和-8.3%之间，具体取决于Ru层的应变弛豫程度。然而，Cu 不是作为单晶沉积，而是作为双晶生长，具有共同的面外取向 Cu(111) 和两个等效的面内取向。 Cu晶粒尺寸较大，为微米量级，晶界为非共格Σ3{211}孪晶界。 Cu 最初生长为孤立的岛屿，合并成厚度约为 50 nm 的连续薄膜。铜膜很粗糙，并且整个电沉积区域的厚度和覆盖率各不相同。在初始岛生长之后，随着沉积物转变为在薄膜表面上生长纳米岛的平面薄膜，铜空隙率和薄膜粗糙度均随着厚度的增加而降低。然而，当厚度超过 200 nm 时，平面铜膜上大的多面铜岛的各向异性生长再次增加了表面粗糙度。与类似地电沉积到多晶Ru晶种上的多晶Cu相比，外延沉积的Cu双晶表现出电阻率的改进。
The electrodeposition of Cu onto epitaxial Ru(0001) seed layers was investigated from a sulfuric acid-based solution containing dilute copper(II) sulfate and chloride ions. Using galvanostatic deposition at −350 μA/cm2, Cu was deposited epitaxially onto a 30 nm-thick Ru(0001) seed layer, despite a compressive misfit strain between −6.9% and −8.3%, depending on the extent of strain relaxation of the Ru layer. However, rather than depositing as a single crystal, Cu grew as a bicrystal having a common out-of-plane orientation of Cu(111) and two equivalent in-plane orientations. The Cu grain size was large, on the order of micrometers, and the grain boundaries were identified as incoherent ∑3{211} twin boundaries. The Cu initially grew as isolated islands, coalescing into a contiguous film at thicknesses around 50 nm. The Cu film was rough, and thickness and coverage varied over the electrodeposited region. After the initial island growth, Cu void fraction and film roughness both decreased with thickness as the deposit transitioned into a planar film with nanometric islands growing on the film surface. However, at thicknesses exceeding 200 nm, anisotropic growth of large, faceted Cu islands on the planar Cu film again increased the surface roughness. The epitaxially deposited Cu bicrystal showed an improvement in resistivity when compared with polycrystalline Cu similarly electrodeposited onto a polycrystalline Ru seed.