Business First

The real challenge in stacking die isn’t the technology. It’s the business of technology.

popularity

The move to stacked die poses some interesting technology challenges and promises significant technology benefits, but the real driver is business—and for this market to work, it has to continue being about business.

In the past it was technology first, business last. We are now at the stage where it is business first, technology last. Re-use of entire die as subystems, better use of design resources, predictable yields on older technologies and the ability to not have to re-design analog or standard IP at advanced nodes can provide enormous dollar savings to developers.

That doesn’t mean that technology gets left in the dust, of course. Wide I/O and shorter wires, rationalization of how memory gets used, connecting cores directly to memory bits and matching the needs of specific applications with right-sized processors are all important advances in SoC design. Performance can be boosted significantly, power can be cut and best-of-breed IP can be developed or purchased to make these chips even better.

But all of this has to be weighed against cost—including hidden costs such as time to market and fuzzy costs such as yield. The real formula to consider here is time to profitability and that will depend on a number of factors. Interposers in 2.5D stacks, or TSVs in true 3D stacks, need to be perfected and commoditized. Drilling through a thinner piece of silicon isn’t simple stuff. Understanding the impact on physical stress is still incomplete, and none of this has been done over time.

In addition, packaging needs to be competitive with existing packages—if not exactly in price, then at least close enough. Time to market with sufficient yields needs to be proven. Full characterization of IP and subsystems needs to be completed for a variety of implementations—particularly in stacks—to avoid nasty physical effects. And IP vendors need to make the necessary investment to make this happen. Moreover, standards need to be developed, particularly in areas such as layout and business responsibility and liability to make sure this all goes smoothly.

None of this will happen overnight, and some of it may be a chicken-and-egg decision where companies hold back on their investment until they see others taking steps in this direction. Market timing, yet another business element, is very important. But if the business of technology is to move forward, the business itself will have to make some important commitments. And in this case, time is of the essence.

–Ed Sperling