Another critical step is bonding the chiplet within its pit.
Some early research has placed silicon chiplets into pits on an unpatterned silicon wafer, but a good deal of work also has been done in inserting chiplets of multiple species--silicon, GaAs, InP--on the same wafer.
He uses 4" silicon wafers, into which he etches pits for inserting the smaller chiplets. To date he has used both GaAs and silicon chiplets.
TSMC discussed its high-density large package using a six-layer redistribution layer (RDL) interposer to connect four silicon
chiplets and two HBMs.
The technology marshals chiplets into place using software-controlled electrical fields generated by arrays of wires beneath an assembly substrate.
For now, placement is aided by simple positive and negative charges added to chiplets before the wafers are minced.
Another big win Green hopes to score with the modular architecture championed by the CHIPS program is the ability to separate out onto individual chiplets the many IP blocks developed for and aggregated into commercial monolithic chips.
"The program is all about devising a physical library of component chips, or chiplets, that we can assemble in a modular fashion."