KEYWORDS: Computer aided design, Silicon, Logic, 3D applications, Semiconducting wafers, Digital signal processing, Thermal modeling, 3D modeling, Clocks, Integrated circuits
3D stacking and integration can provide
system advantages equivalent to up to two technology
nodes of scaling. This paper explores memory rich
applications for 3DIC. It shows how memory power
and memory bandwidth can both be improved by an
order of magnitude through 3D integration, and
specifically explores a DSP application.
Ternary Content Addressable Memory (TCAM) has been an emerging technology for fast packet forwarding, commonly
used in longest prefix match routing. Large table size requirements and wider lookup table data widths have led to
higher capacity TCAM designs. However, the fully parallel characteristic of TCAM makes large TCAM design more
challenging and limits its capacity due to intensive power consumption. This paper proposes 3D IC technology as a
solution to reduce the power consumption by reducing the interconnect capacitances of TCAM. In 3D IC, multiple
wafers are stacked on top of each other, and the tiers are vertically connected through 3D vias. 3D vias reduce metal
interconnect lengths and parasitic capacitances, resulting in power reduction. In this paper, 3D vias are used to replace
matchlines, whose transition during parallel search operations is a major source of high power consumption in TCAM.
An analysis of parasitic interconnect capacitance has been done using a quasi-static electromagnetic field simulation
tool, Ansoft's Q3D Extractor, on a TCAM memory core in both conventional 2D IC structure and 3D IC structure with
the process parameters of the MIT Lincoln Labs 0.18μm FDSOI process. Field analysis and spice simulation results
using a capacitance model for interconnects show that a 40% matchline capacitance reduction and a 23% power
reduction can be achieved by using a 3-tier 3D IC structure instead of the conventional 2D approach.
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