低熱預算生長石墨烯於金屬導線以提升導線可靠度

Abstract

在本研究中，我們在後端製程所使用之鈷及釕導線上直接成長石墨烯，形成鈷或釕-石墨烯異質結構導線。其中我們是透過熱燈絲輔助感應耦合型化學氣相沉積系統並搭配苯或乙炔作為前驅物於金屬導線上成長石墨烯。對於不同的金屬，會因為不同的對碳溶解率而有不同的成長機制，碳溶解率較高的金屬會傾向以偏析的方式成長石墨烯；而碳溶解率較低的金屬則會傾向以表面催化的方式成長石墨烯。 因此，在此研究中我們使用不同前驅物針對不同金屬進行石墨烯品質的優化。我們發現金屬-石墨烯異質結構導線有更低的電阻值，以鈷-石墨烯異質結構導線與鈷導線相比，阻值下降了3.04%；而釕-石墨烯異質結構導線與釕導線相比則下降了1.6%。可靠度量測的部分，異質結構導線有更高的最大耐受電流及導線可靠度，鈷-石墨烯異質結構導線最大耐受電流提升17.6%；釕-石墨烯異質結構導線則提升了10.6%。並且鈷-石墨烯異質結構導線在5 MA/cm2的高密度電流下，在200°C下的平均失效時間為純鈷導線的3倍；釕-石墨烯異質結構導線在40 MA/cm2的電流密度下，在200°C下的平均失效時間為釕導線的3倍。 總結來說，相較於金屬導線，金屬-石墨烯異質結構導線有更低的電阻值、更高的崩潰電流密度及更長的導線平均失效時間。

For this study, we demonstrate the fabrication of cobalt-graphene or ruthenium-graphene heterostructure wires by direct growth of graphene on BEOL interconnect. We use benzene or acetylene as a precursor to deposition multilayer graphene on cobalt or ruthenium wire through a hot filament-assisted inductively coupled plasma chemical vapor deposition system. For different metals, we find growth mechanisms can be different as carbon solubility changes. Metals with higher carbon solubility tend to deposition graphene by segregation; while metals with lower carbon solubility tend to form graphene by surface catalytic. Therefore, we improve the quality of graphene by using different precursors on different kinds of metals in the experiment. We find that metal-graphene heterostructure wires have lower resistance. The resistance of the cobalt wire and the ruthenium have dropped by 3.04% and 1.6% respectively after the graphene is capped on the surface. As far as the reliability measurement is concerned, the metal-graphene heterostructure wires have higher breakdown current and reliability. The breakdown current density of cobalt and the ruthenium wire both with graphene capping have increased 17.6% and 10.6%, respectively. Furthermore, the cobalt-graphene heterostructure wires have MTTF of 3 times that of pure cobalt wire at 200°C under a high current density of 5MA/cm2, and the ruthenium-graphene heterostructure wires have MTTF of 3 times that of ruthenium wire at 200°C under a high current density of 40MA/cm2. To summarize, metal-graphene heterostructure wires show lower resistance, higher breakdown current density, and longer mean time to failure, compared to metal wires.