Changing The Flow Of Technology

A mad scramble is underway—quietly, of course, because it involves competitive positioning—to prepare for stacked die. No one wants to be left out of this transition, regardless of whether they’ve branded it as pure fiction in the past. And no one wants to be caught unprepared, even though they’re not sure exactly when this shift will take place.

But what’s particularly interesting underneath is exactly how companies are jockeying for position. Rather than working at the latest technology node, which is where most battles have been fought in the past, stacked die involves lots of older process nodes as well as the newest stuff. As a result, the race is happening in multiple areas—at the bleeding edge of technology and as far back as 250nm. All process technology is being retrofitted with new techniques for manufacturability, yield, test, and power. In fact, what is happening at the forefront of Moore’s Law is now being pushed backward instead of just the reverse.

The manufacturability and yield are relatively well established, even though they are being improved. Test may actually require a different sizing of die and some adjustments in layout and packaging. But the really big change is on the power side. Before 90nm, power was an afterthought. Computers were still the driving force for semiconductors and most of them were built for speed and plugged into a wall. Two hours of battery time was considered acceptable. Shutting down parts of a chips was considered ridiculous.

Fast forward to the present and energy is now a critical factor in everything from mobile electronics to data centers. That won’t change with stacked die, either. Power is an essential ingredient for success. Gaining efficiency or performance with Wide I/O while losing it with older analog or digital components in a multi-layer stack is a recipe for disaster, and changes are under way to make sure that doesn’t happen. The only question now is how quickly.