The search for the most conductive metal for narrow interconnect lines
The search for the most conductive metal for narrow interconnect lines
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DOI：
10.1063/1.5133671
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发表时间：
2020-02-07
影响因子：
3.2
通讯作者：
Gall, Daniel
中科院分区：
文献类型：
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作者：
Gall, Daniel
集成电路继续小型化的一个主要挑战是尺寸不断减小的铜互连线的电阻率增加。替代金属有可能通过(A)促进镜面电子界面散射和可忽略的晶界反射或(B)使电阻率标度可以忽略的低体积平均自由程来缓解这一电阻率瓶颈。最近的研究表明，在互连金属和衬层之间的界面处的镜面电子散射需要在界面和衬层(即绝缘衬层)处具有低的态密度，并且需要光滑的外延金属-衬层界面或只有弱的范德华键，这是2D衬层材料的典型特征。如果晶界尺寸较大(宽导体和窄导体的晶界尺寸分别为200 nm或线宽的10倍)，或者由于相邻晶界的低能晶界和电子态匹配，电子反射系数较小，则晶界对室温电阻率的贡献可以忽略不计。第一性原理计算提供了金属(Rh、Pt、Ir、Nb、Ru、Ni等)的清单。体电阻率乘以体电子平均自由程Rho(O)xλ的乘积很小，这是抑制电阻率标度的指标。然而，外延层上的电阻率测量表明，对于许多金属来说，Rho(O)x Lambda的实验值相当大，这表明经典的输运模型在小(
A major challenge for the continued downscaling of integrated circuits is the resistivity increase of Cu interconnect lines with decreasing dimensions. Alternative metals have the potential to mitigate this resistivity bottleneck by either (a) facilitating specular electron interface scattering and negligible grain boundary reflection or (b) a low bulk mean free path that renders resistivity scaling negligible. Recent research suggests that specular electron scattering at the interface between the interconnect metal and the liner layer requires a low density of states at the interface and in the liner (i.e., an insulating liner) and either a smooth epitaxial metal-liner interface or only weak van der Waals bonding as typical for 2D liner materials. The grain boundary contribution to the room-temperature resistivity becomes negligible if the grain size is large (>200 nm or ten times the linewidth for wide or narrow conductors, respectively) or if the electron reflection coefficient is small due to low-energy boundaries and electronic state matching of neighboring grains. First-principles calculations provide a list of metals (Rh, Pt, Ir, Nb, Ru, Ni, etc.) with a small product of the bulk resistivity times the bulk electron mean free path rho(o) x lambda, which is an indicator for suppressed resistivity scaling. However, resistivity measurements on epitaxial layers indicate considerably larger experimental rho(o) x lambda values for many metals, indicating the breakdown of the classical transport models at small (