DSP Systems Using Three-Dimensional Integration Technology - Signal Processing Systems - page 820

integration and reduced overall costs. As a result, 3D integration appears to be a
viable enabling technology for future integrated circuits (ICs) and low-cost multi-
functional heterogeneous integrated systems.
As 3D integration technology is quickly maturing and entering mainstream
markets, it clearly provides a new spectrum of opportunities and challenges for
circuit and system designers, and warrants significant rethinking and innovations
from circuit and system design perspectives. Existing work mainly came from
two research communities, i.e., electronic design automation (EDA) and computer
architecture. In the context of EDA, a significant amount of research has been done
in the areas of physical design (e.g., see [ 1 , 16 , 28 , 58 , 67 ] ) and thermal analysis
and management (e.g., see [ 13 , 24 , 36 , 64 , 66 ] ). As pointed out in [ 5 ] , architectural
innovations will play an at least equally important role as EDA innovations in order
to fully exploit the potential of 3D integration. At the architectural front, existing
work predominantly focused on high-performance general-purpose microprocessors
(e.g., see [ 7 , 19 , 31 , 41 , 49 - 51 , 65 , 76 ] ), as 3D integration clearly provides a promising
solution to address the looming memory wall problem [ 78 ] in computing systems.
Due to the demands of an ever-increasing number of signal processing ap-
plications that require high throughput at low power, digital signal processing
(DSP) integrated circuits, including both programmable digital signal processors
and application-specific DSP circuits, have become, and will continue to be, one of
the main drivers for the semiconductor industry [ 69 ] . Nevertheless, little attention
has been given to exploiting the potential of 3D integration to improve various
programmable and/or application-specific DSP systems. This chapter represents
our attempt to fill this missing link and, more importantly, motivate greater future
efforts from DSP system research community to explore this new and rewarding
research area. In this chapter, after briefly reviewing the basics of the 3D integration
technology, we first discuss the rationale and opportunities for DSP systems, both
programmable digital signal processors and application-specific signal processing
circuits, to exploit the 3D integration technology. In particular, we advocate a 3D
logic-DRAM integration paradigm, i.e., one or multiple DRAM dies are stacked
with one logic die, for 3D DSP systems, and present an approach for 3D DRAM
architecture design. Then we present two case studies on applying 3D logic-DRAM
integration to clustered VLIW (very long instruction word) digital signal processors
and application-specific video encoders in order to quantitatively demonstrate the
promise of 3D DSP system design.

2 Overview of 3D Integration Technology

The objective of 3D integration is to enable electrical connectivity between multiple
active device planes within the same package. Various 3D integration technologies
are currently pursued and can be divided into the following three categories:

1. 3D packaging technology : It is enabled by wire bonding, flip-chip bonding, and
thinned die-to-die bonding [ 14 ] . As the most mature 3D integration technology,