True 3D-IC Problems

Placing logic on logic may sound like a small step, but several problems must be overcome to make it a reality. True 3D involves wafers stacked on top of each other in a highly integrated manner. This is very different from 2.5D integration, where logic is placed side-by-side, connected by an interposer. And there are some intermediate solutions today where significant memory is stacked on l... » read more