Why the secrecy surrounding TSI development?
That brings us to cost. Cost is, of course, always a huge issue. No exception here. “When you compute the target cost for a silicon interposer, you need to do it at the complete system level or at least die/package level to find the intrinsic cost of the interposer itself,” Yannou says.
Interested in a universal cost metric for a TSI? According to Yole’s cost simulations, it’s going to need to cost about 1 cent/mm2 or less for a TSI, otherwise it doesn’t stand a chance of becoming a competitive solution. Yannou determined that for an 8-in. depreciated fab that cost target could hardly be achieved, but shifting to a 12-in. fab can drop the cost even further down to 0.87 cent/mm2 —using three metal routing layers and TSVs filled with copper (100µm thickness) and a via diameter of 30µm.