There's still a lot of confusion about 3D ICs. Let's start by considering the way of the world before they existed.
System-on-chip (SoC) devices
Having large quantities of individually packaged silicon chips was not a major problem when it came to electronic products that were the size of filing cabinets, weighed a thousand or so pounds, and were powered by a cable plugged into the wall. These days, however, there's a strong drive toward creating smaller products that offer humongous performance while consuming very little power. This is particularly true for handheld, battery-powered products like smartphones and tablets.
All of this led to the development of system-on-chip devices (SoC), in which all of the functions are implemented on a single die, as illustrated below.
A bird's-eye view of a circuit board with a SoC device.
It's perhaps worth mentioning that different people have different definitions of SoC. A digital logic designer might say it contains one or more processor cores, memory blocks, peripheral functions, and hardware accelerators, all created on the same piece of silicon. By comparison, a system architect, who is looking at things from a slightly higher vantage point, might say it is a single device that combines digital logic, memory, and analog/RF functions on the same die.
The advantage of an SoC is that you get the highest performance with the lowest power consumption -- at least for the digital portions of the device. However, creating one of these little rascals is horrendously complicated, extremely resource intensive, and terribly time-consuming. Also, adding analog and RF functions on the same die as the digital logic may mean that the analog/RF functions aren't as robust as they could be if implemented using a dedicated process, and you can run into all sorts of noise and isolation problems. You also have to consider the time and expense involved in re-spinning the design in the future to enhance functionality or add features.
To Page 3 >