IWLPC (Wafer-Level Packaging) Conference Proceedings


Authors: C. Truzzi, S. Lerner, F. Raynal, V. Mevellec, N. Frederich, D. Suhr, I. Bispo and B. Couturier
Company: Alchimer SA
Date Published: 10/11/2010   Conference: IWLPC (Wafer-Level Packaging)

Abstract: Fundamental limitations of ionized Physical Vapor Deposition (iPVD) copper seed, and Chemical Vapor / Atomic Layer Deposition (CVD/ALD) barrier coverage in deep Through Silicon Vias (TSV), coupled with unavoidable high capital investments, are holding back the industry-wide adoption of Three-Dimensional Integrated Circuit (3D-IC) solutions.

Electrografting (eG) [1] generates surface-initiated conformal films on (semi)-conducting materials – such films are adherent, uniform, thin and continuous. eG is a wetprocess technique, operated in standard plating tools, which has proven its efficiency to deposit copper seed layers for interconnect Back End Of Line (BEOL) [2] and TSV [3,4] applications. Chemical grafting (cG) is a similar technology, used to graft films on non-conductive surfaces.

Wet deposition of insulator, barrier and copper seed layers has been performed inside deep TSVs, using a combination of eG and cG. TSVs formed using these layers meet key unit process requirements such as conformality, uniformity, good electrical and mechanical properties, low contamination level and adhesion [5]. The present paper describes the integration of such layers in conventional TSVs metallization process flows (up to 300-mm Si wafers), focusing on Cu filling compatibility in various TSVs dimensions.

Conventional Electro Plating Deposition (ECD) performed after copper seed to complete via metallization shows weak properties associated to: strong acidic attack of the copper seed, high amounts of contaminants (Cl, S and C) and low uniformity when deposited on top of resistive seed layers. A new mildly basic TSV plating chemistry is presented here, to be deposited on top of various thin layers including electrografted films, with low attack of the seed layer, low contaminants and high uniformity on resistive seed layers.

Key words: Through Silicon Vias, TSV, electrografting, chemical grafting, polymer dielectric, ECD

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