Many of the world's 3D IC elite met last week at the 2^nd annual Georgia Tech 2.5D Interposer Conference which focused on the technology and performance of silicon and glass interposers.

Matt Nowak of Qualcomm, long a 3D advocate, reported that Qualcomm has now built "thousands of parts" and does not see anything stopping high-volume manufacturing (HVM) except cost. Nowak indicates that Qualcomm will require a price of ~ $2 for a 200mm² silicon interposer. The former is just out of the reach of those proposing "coarse" interposer fabrication, and the latter is significantly out of the pricing structure for dual damascene foundry-based fine interposers

Nagesh Vordharalli of Altera quoted an IMEC study which shows that the sweet spot for maximum bandwidth will come from interposers with RDL lines/spaces ~ 3μm. Nagesh feels that silicon-based interposers need to be in the 1-2 cents per mm² range to compete with future high-density laminate technology.

Yole reported that they expect revenues for 2.5D/3D interposers to reach $1.37B, or 15% of the packaging substrate market value, by 2017.

Yole sees interposer fabrication diverging by material (silicon vs. glass) at 300mm with silicon fabrication moving to 450mm wafers and glass fabrication moving toward flat-panel glass lines, both as a means of lowering cost. By 2017 Yole expects silicon interposers to exceed the revenue of their glass counterparts by at least 3.5:1. Most in attendance agreed that it was unlikely we will see todays OSATs buying flat-panel display lines to produce glass interposers, but rather could see current flat-panel producers entering the market if they perceive this as a financially sound move.

Subramanian Iyer of IBM -- clearly a silicon advocate -- brought attendees to laughter when he commented that "glass could be an acceptable substrate if you could remove the oxygen." Iyer astutely commented that 2.5/3D will not replace scaling, but rather is "orthogonal to scaling" and its most significant performance attribute is that it will significantly reduce power consumption, which would ultimately be the key driver for the portable electronics marketplace.



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