In this installment of our 3D IC mini-series, we ponder the current state-of-the-art 3D IC technologies.
Active-on-active 3D ICs/SiPs with TSVs
The next step up the technology ladder is active-on-active 3D IC/SiPs, which involve at least one die being mounted on the top of another die, with the lower die employing through-silicon vias (TSVs) to allow the upper die to communicate with the lower die and the SiP substrate as illustrated below:
A simple active-on-active 3D IC/SiP using TSVs.
So, for example, we could have a memory die attached to a logic die (or vice versa), or an analog/RF die attached to a digital logic die, or… just imagine your own scenario.
The previous image showed the simplest possible implementation using this technology. In the not-so-distant future, we may expect to see multiple dice stacked on top of each other using TSVs, and multiple groups of dice connected together using a silicon interposer, all presented as a single SiP assembly as illustrated below:
A more complex 3D IC/SiP assembly.
Now, I know that this drawing looks a bit like a New York skyline and you may think it's all rather clunky, but -- as we previously noted -- you have to remember that the individual dice and the silicon interposer are only ~0.2mm to ~0.7mm thick, so the entire assembly shown above would be much smaller than you might suppose.
So just how prevalent is this technology? Is it for real, or is it all pie in the sky? Well, according to a 2012 report from Yole Développement:
Last year,* the market value of all the devices using TSV packaged in 3D in the 3DIC or 3D-WLCSP platforms (CMOS image sensors, Ambient light sensors, Power Amplifiers, RF and inertial MEMS) was worth $2.7B. It will represent 9% of the total semiconductor value by 2017, hitting almost $40B.
In my next installment in this miniseries we will consider alternative approaches involving esoteric materials and monolithic 3D IC technologies.
— Max Maxfield, Editor of All Things Fun & Interesting