by Jan Provoost, science editor, imec

May 25, 2011 – At the Imec Technology Forum (ITF, May 25-26 in Brussels), Pol Marchal introduced his talk on 3D chip technology by recalling some of the powerful trends in the semiconductor market. Each trend points to the next wave of applications using 3D chips with tightly integrated sensors.

One trend predicts that electronic devices will become smaller by a factor of 10 in the coming years. At the same time, new applications will require a bandwidth between memory and processor that can only be delivered by a tighter, on-chip integration of memory and processor cores.

A second trend is that applications will be integrated with forever more sensors. Think of the image sensors or movement sensors that come with nearly every phone nowadays. According to Marchal, smell will be next, calling for the integration of electronic noses, sensors that recognize hundreds of different vapors. To integrate these sensors, a tight 3D integration brings advantages: a smaller form factor, high IO density, reduced power consumption through much shorter connections with less parasity. In short, no technology compromises.

Imec is one of the research centers where 3D integration was pioneered. The technology flavor developed was 3D-SIC (3D stacked ICs), where dies are interconnected through the silicon with so-called TSVs (through-silicon vias). 3D SIC technology has now matured to a level where you will see products coming out of the fabs in the coming years.

But despite a maturing technology, the challenges to design and fabricate 3D SICs are still considerable. Marchal outlined how imec has recently build a first heterogeneous 3D design, a DRAM-on-logic test vehicle, with the goal to resolve 3D-related processing challenges, perform a first assessment of the compatibility of 3D & DRAM technology, "pipe-clean" the supply chain, and set up design rules for 3D.

According to Paul Marchal, the design and integration of sensor applications can benefit from a strong collaboration between the various supply chain partners — if it is focused on an attractive system roadmap for everyone involved.

Imec logic IC stacked on commercial DRAM, connected with TSVs and microbumps.