Timing optimization is a critical component of deep submicrometer design an
d buffer insertion is an essential technique for achieving timing closure,
This work studies buffer insertion under the constraint that the buffers ei
ther: 1) avoid blockages or 2) are contained within preassigned buffer bay
regions. We propose a general Steiner-tree formulation to drive this applic
ation and present a maze-routing-based heuristic that either avoids blockag
es or finds buffer bays. We show that the combination of our Steiner-tree o
ptimization with leading-edge buffer-insertion techniques leads to effectiv
e solutions on industry designs.