03/01/2002 09:00 AM
Electrical Engineering
To reduce fabrication process variation due to chemical-mechanical polishing, layout must be made uniform with respect to density criteria. Currently the layout density control is achieved by metal filling, which adds dummy metal geometries into the layout either at the foundries or by specialized verification tools. But because the added metal inevitably increases layout interconnect capacitance as well as the defect sensitivity, which reduces the manufacturability, the fill amount must be kept as small as possible. This paper presents a new solution for layout density control, named wire spacing and metal filling. Before adding dummy metal into the low-density area, we increase the wire spacing by moving wires from high-density areas toward low-density areas. The experimental results show that compared with stand-alone metal filling only, wire spacing followed by metal filling greatly reduces the total fill amount and also improves the manufacture yield.
