Pick and Place: To create a 3-D IC, one chip, or die, called a donor [top image] is placed on top of another, called the host. The host can be on a whole wafer before it is cut into single chips, or it can be sliced off a wafer and placed in a waffle pack.

In Step 1 [bottom image], a standard pick-and-place tool aligns the faces of the donor and host dies. Signals between the chips go through the redirect layer, a new wire to which the host's global interconnects are routed and that runs just beneath the host's top surface.