System on chip design methodology applied to system in package architecture

There are two competing technologies pursuing the 'holy grail' of complete system integration. Today, the most common method used to create the 'system' is to mount separately packaged ICs on a next-level substrate. Even with a low pin count, a package is typically several times larger than the IC, to accommodate the low wiring density on the PCB. High-performance systems, such as network processor systems, require high data bandwidth between key components and thus need an increased number of signal I/Os. Wide I/O busses switching at high speeds consequently require a larger number of power and ground pins to reduce switching noise. As a result, system performance is limited by increasing package size and the associated parasitic inductance and capacitance of the package and its connection on the PCB. System on chip (SoC) architecture attempts to integrate many functions, both analog and digital into a monolithic device. The successes are many, but so are the challenges. Many functions cannot be optimized due to the limitation of the semiconductor substrate used. Also, as defect density scales with area, the notion of integrating large scale functions (memory, switch fabrics) with small scale functions (rf devices) results in compounded yield impacts. System in Package (SiP) technology allows heterogeneous devices to be integrated into a small form factor. The integration technology includes embedded devices in the substrate and 3 dimensional chip-stacking approaches. By using a silicon based SiP, a copper/low K interconnect defined by lithographic processes on silicon offers very dense routing with high speed, low noise signal paths. The ICs used in the SiP can be designed to leverage the high density interconnect by optimizing both the core and the I/O of each device. Additionally, specialized devices can be designed specifically for the SiP architecture to take advantage of the high bandwidth and low latency features. Reducing chip-to-chip bus capacitance can dramatically decrease system power requirements and thermal dissipation. The lower bus power can be traded against higher bus frequency to improve performance at a fixed power level.