Influence of Macroscale Dimension on the Electrocrystallization of Cu Pad and Redistributed Layer in Advanced Packaging

Abstract

Equiaxed copper (EG Cu), copper with columnar nanotwinned grains (C‐NT Cu), and copper with mixed equiaxed and columnar grains (MG Cu) were electroplated on pads and redistributed layers (RDLs) with different dimensions. When the diameters of pads increased from 40 μm to 105 μm, the flatness of pads decreased from 34.5% to 24.0%. And the flatness gradually deteriorated from 16.5 % to 34.4 % with the increase of RDL width from 8 μm to 20 μm. In contrast, the flatness of C‐NT Cu and MG Cu fluctuated between 1 % and 5 %, showing a weak correlation on the dimension. In terms of microstructure, the EG Cu and MG Cu had a weak correlation with size change, and the grain orientation showed a randomness. However, the (111) texture component of C‐NT Cu differed greatly with different dimensions, especially in transition layer. The (111) texture component changed from 9.6% to 38.1% for ϕ 40‐105 μm pad, and from 14.3% to 18.9% for 8‐20 μm wide RDL. The study reveals the significant size effect on the deposited profile and microstructure of electrodeposited copper materials, which should give insights of the materials design in advanced packaging technology.This article is protected by copyright. All rights reserved.