Niagara2 employs an extensive Design for Manufacturing
(DFM) methodology. Single poly-orientation was used everywhere
except I/O cells which had to be rotated by 90 degrees
between perpendicular sides of the die. Larger-than-minimum
design rules were used in certain cases (e.g., to reduce the
effects of poly/diffusion flaring, near stress-prone topologies
to reduce chances of dislocations in Si-lattice, etc). A limited
number of gate-poly pitches were used so that the Optical
Proximity Correction (OPC) algorithm could be optimized for
them to yield better gate-CD control. Dummy polys were used
extensively to shield gates to reduce gate-CD variation. OPC
simulations of critical cell layouts were performed to ensure
sufficient manufacturing process margin. Statistical simulations
were extensively used to reduce unnecessary design margin
that could result from designing to the FAB-supplied corner
models. Redundant vias were placed and metal overlap of
contacts/vias was increased wherever possible. Most of the
Niagara2 design uses a static cell-based design methodology.
All custom designs, which also used nonstatic circuit design
styles, were proven on test chips prior to first silicon.