[threatripper]

Heat removal is basically a 2D problem. A 3D pipe has a 2D cross section in which fluid can transport heat. Right now we are mostly limited by heat removal, so adding more height to the chip doesn't help anything with the heat. Also, the chips are already many layers thick and each layer means processing steps which means time and money.

If you look into flash memory which aren't limited by heat, they have dozens of functional layers already and then we also stack those silicon wafers.