Abstract
Copper (Cu) electroplating is a mature technology, and has been extensively applied in microelectronic industry. With the development of advanced microelectronic packaging, Cu electroplating encounters new challenges for atomic deposition on a non-planar substrate and to deliver good throwing power and uniform deposit properties in a high-aspect-ratio trench. The use of organic additives plays an important role in modulating the atomic deposition to achieve successful metallic coverage and filling, which strongly relies on the adsorptive and chemical interactions among additives on the surface of growing film. However, the adsorptive characteristic of organic additives inevitably results in an incorporation of additive-derived impurities in the electroplated Cu film. The incorporation of high-level impurities originating from the use of polyethylene glycol (PEG) and chlorine ions significantly affects the microstructural evolution of the electroplated Cu film, and the electroplated-Cu solder joints, leading to the formation of undesired voids at the joint interface. However, the addition of bis(3-sulfopropyl) disulfide (SPS) with a critical concentration suppresses the impurity incorporation and the void formation. In this article, relevant studies were reviewed, and the focus was placed on the effects of additive formula and plating parameters on the impurity incorporation in the electroplated Cu film, and the void formation in the solder joints.
Highlights
Copper (Cu) has been receiving considerable attention in the microelectronic industry due to its superior electrical and thermal conductivity as a good conducting material
We have reviewed that the use of functional additives in the electroplating process results in an impurity incorporation in the electroplated Cu layer
Cu-plated layer containing a higher level of impurity residues, which led to severe void formation at the resultant solder/Cu interface subjected to thermal annealing
Summary
Copper (Cu) has been receiving considerable attention in the microelectronic industry due to its superior electrical and thermal conductivity as a good conducting material. In addition to Kirkendall void, the impurity incorporation in the Cu deposit causes the formation of voids in the electroplated-Cu solder joints [16,17,18,28,29,30,31,32]. The addition level of organic additives in the Cu-plating solution is low, the strong adhesion characteristic of the additives causes a non-negligible incorporation level of impurity in the Cu deposit, and a significant effect on the void formation and IMC growth in the solder/Cu joints [16,17,18,29,30,31,33,34,35]. The impurity effect on the void formation and IMC growth was discussed
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