Semiconductors have always lived in a two-dimensional world. But with the rising use of three-dimensional (3D) stacking technology, chips are making a foray into the third dimension. Today's systems-on-a-chip (SoCs) often contain a diverse range of functions, each served best by a different process technology.
As silicon moves to 90-nm and smaller geometries, the cost of adding embedded capabilities like analog or flash memory to a logicbased process becomes a burden. The additional process steps make the whole wafer more expensive to accommodate the needs of what may be a very small percentage of the final die area. In some cases, these steps may degrade the speed, area requirements, or power consumption of the majority of the device.
Recent efforts have tried to address these issues by stacking semiconductor die on top of each other inside a single package. Traditional wire-bonded stacked semiconductor solutions have found initial acceptance in mobile phones and other applications in which large amounts of functionality must fit into small spaces.
The next step is adding a vertical interconnect directly between the die. Such an approach can link a base chip with several die, including DRAM, flash, programmable logic, and microprocessors. The additional die are produced using functionally optimized processes, such as memory or analog, which do not integrate smoothly with the digital logic base chip.
Although some 3D chips now are available, iSuppli's Emerging Technologies and Products service believes the market is now quite small, amounting to less than $10 million in 2005. Yet the ultimate potential is extremely high, as significant numbers of ASICs, applicationspecific standard products (ASSPs), programmable logic devices (PLDs), microcontrollers, microprocessors, and memory eventually could be included within larger devices using 3D technology.
Worldwide 3D chip revenue is expected to rise to $1.3 billion in 2010 and to $6.1 billion in 2015. But the market could easily exceed this level and grow to as much as $17.3 billion in 2015.