Silicon interposers used to be exotic technology, but they have become more common as fabrication practices have improved. It was used in high-end FPGA solutions like Xilinx’s Virtex-7 2000T where it delivered 10,000 connections between multiple die in a 2.5D architecture. Altera used a slightly different approach to link its high-speed serial interfaces to the FPGA fabric.
Silicon interposer system design tends to be less complex that an SoC design, but it is still a challenge. Up until now it hasn’t put the technology into the same realm as PCB design, but a company called zGlue is looking to change this—at least on a small scale.
zGlue has developed a programmable silicon interposer fabric that targets compact applications (e.g., wearable tech) that includes applications such as medical devices. It allows developers to combine die onto the fabric, resulting in a much smaller compact form factor.
The programmability of the underlying structure speeds the implementation process allowing chips to be delivered in as little as eight weeks while reducing the form factor by a factor of 10.
The zGlue interposer comes in one size at this point, but it can be used for any number of die that will fit on it. Developers can provide their own and work with zGlue to incorporate them into a chip, or they can take advantage of BGA “chiplets” that are die already approved by zGlue (see figure 2).