Lithographic defect aware placement using compact standard Cells without inter-cell margin

Conventional standard cells contain extra space, called inter-cell margin, to prevent potential defects caused by lithography process. Margin is indeed necessary between some cell pairs, but there are also lots of cell pairs that do not yield any defects (or have very low probability of defects) when they are placed without margin. We address a new placement problem using standard cells without inter-cell margin. Placement should be done such that defect probability is made as small as possible while standard objectives such as wirelength is also pursued. The key in this approach is efficient computation of defect probabilities of all cell pairs and arranging them as a table that is referred to by a placer. We study how the cell pairs can be grouped by examining similar patterns along cell boundary, which greatly reduces the number of defect probability computation. The proposed placement method was evaluated on a few test circuits using 28-nm technology. Chip area was reduced by 10.8% on average with average and maximum defect probability kept below 0.4% and 4.1%, respectively.