3D IC success hinges on major foundries(2)

At the panel session, Abe Yee, a packaging expert at Nvidia, had some suggestions for the likes of Globalfoundries, Micron, SK Hynix, and TSMC.

“We’ve invested $2 billion in [the chip stacking] market already and haven’t got it back, but we continue to investand our suppliers need to think the same way,” Yee said.

“I don’t think Moore’s Law is going to last another 20 years, and even if it does we will still need to get memory closer to processors,” Yee added. “So this market is going to happen if you like it or not, and suppliers have to think about how they will invest in it,” he said.

Of course it’s always easier to tell the other guy to invest the next billion. Meanwhile, the other billion dollar question is, what will Samsung do?”

The Korean giant has all the piecesDRAM, flash, processors, and fabs. It has been selling as merchant products for some time 4GB memory stacks, so it has some 3D capabilities.

At ARM Tech Con last week, Samsung even teased attendees with a demo of a 3D stack of memory and its Exynos application processor using a Jedec Wide IO interface. It delivered significantly lower power than a traditional separate smartphone SoC and memory. But Samsung would not comment on if or when it would become a product.

There are a few problems with the “true” 3D stacks using through silicon vias to connect logic and memory for uses like smartphone SoCs. No one knows how to cool the logic, for instance, and the EDA tools and skills to lay out the TSVs are said to be immature.

In any case, Samsung’s engineers likely have a good idea when it is economical to make a 3D IC for smartphones. Given it is already pulling ahead of Apple in mobile device volumes, the pressure may be off for the moment to jump to a new and risky technology.

Meanwhile, a veteran engineer in the audience at the panel surprised everyone when he chimed in with a data point. He had done a teardown of the Apple A7 processor in the iPhone 5S. It uses a very, very simple six layer board-two layers each for signal, ground and signal, he said. The memory is essentially on the other side of the simple board.

His analysis suggests Apple has discovered a low cost path to 3D ICs. Put most of the smarts in the SoC and use a simple pc board as “a poor man’s 3D IC.”

Perhaps the next iPhone will use an even simpler layer between its SoC and memory chip such as a flex circuit or a glass or organic interposer. It’s a great way for a fabless company to compete with vertically integrated giant like Samsung.

So everyone is watching a few things very closely. What will Apple and Samsung do in mobile. And what will TSMC vs. Globalfoundries and Micron vs. SK Hynix do in 2.5D pricing.

Who do you think will blink first?

– Rick Merritt
??EE Times