Layer Reassignment for Antenna Effect Minimization in 3-Layer Channel Routing


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Abstract

As semiconductor technology enters the deep submicron em, reliability has
become a major challenge in the design and manufacturing of next generation
VLSI circuits. .ln this paper we focus on one reliability issue - the antenna
effect in the context of s-layer channel routing. We first present an antenna effect
model in Z-layer channel routing and, based on this, an antenna effect cost
function is proposed. A layer reassignment approach is adopted to minimize this
cost function and we show that the layer reassignment problem can be formulated
as a network bipartitioning problem. Experimental results show that the
antenna effect can be reduced considerably by applying the proposed technique.

Introduction

Continued advances in IC technology along with the development of packaging technologies
with superior thermal characteristics enable an increase in the level of integration of
VLSI systems. In this process, the aggressive scaling of device and interconnect dimensions
has played, and in the foreseeable future will still play, an important role in achieving
significant improvements in VLSI performance and circuit density. However, scaling has
a detrimental effect on reliability due to increase in current density, electric field, leakage
currents and oxide breakdown [l]. As a result, reliability has become a major issue
and challenge in the design and manufacturing of next generation deep-submicron VLSI
circuits [2, 3, 4, 51.

Antenna Effect in 3-Layer Channel Routing

The basic channel routing problem can be formulated as follows. Given a rectangle
channel, which has horizontal grid tracks and vertical columns, and a netlist, which is
usually represented by two lists of net terminals on the top and bottom of the channel,
respectively, we are asked to connect alI the nets such that the height of the channel
is minimized. The constraint that must be observed during the routing procedure is that
wires of different nets cannot overlap or intersect in the same layer. Among all the terminals
for each net, one terminal is the driver or source of the signal, and the remaining terminals
are receivers. We distinguish between driver and receiver because they play an important
role in determining the antenna effect as will be elaborated later in this paper.
We study 3-layer channel routing in this paper.