We have reported a method of fabricating (111)-orientated nanotwinned copper (nt-Cu) by direct current electroplating. X-ray analysis was performed for the samples annealed at 200 to 350 • C for an hour. X-ray diffraction indicates that the (200) signal intensity increases while (111) decreases. Abnormal grain growth normally results from transformation of surface energy or strain energy density. The average grain size increased from 3.8 µm for the as-deposited Cu films to 65-70 µm after the annealing at 250 • C for 1 h. For comparison, no significant grain growth behavior was observed by random Cu film after annealing for an hour. This research shows the potential for its broad electric application in interconnects and three-dimensional integrated circuit (3D IC) packaging.
Nanotwinned copper
(nt-Cu) films with ⟨111⟩ crystal
orientation were electroplated on Si wafers by pulse plating, with
original grain size of ∼1.4 μm. By patterning and annealing
the nt-Cu film at 450–500 °C for 1 h, we can grow a large
number of ⟨100⟩-oriented quasi-single crystal Cu lines
that are 200 and 500 μm in length and 60 μm in width.
We perform anisotropic grain growth on a Si substrate to fabricate
quasi-single crystal Cu lines array of ⟨100⟩ crystal
orientation. These large ⟨100⟩ Cu single crystals may
have potential applications as interconnects in three-dimensional
integrated circuit technology.
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