Boosting Pin Accessibility through Cell Layout Topology Diversification

As the layout of standard cells is becoming dense, accessing pins is much harder in detailed routing. The conventional solutions to resolving the pin access issue are to attempt cell flipping, cell shifting, cell swapping, and/or cell dilating in the placement optimization stage, expecting to acquire high pin accessibility. However, those solutions do not guarantee close-to-100% pin accessibility to ensure safe manual fixing afterward in the routing stage. Furthermore, there is no easy and effective methodology to fix the inaccessibility in the detailed routing stage as yet. This work addresses the problem of fixing the inaccessibility in the detailed routing stage. Precisely, (1) we produce, for each type of cell, multiple layouts with diverse pin locations and access points by modifying the core engines i.e., gate poly ordering and middle-of-line dummy insertion in the flow of design-technology co-optimization based automatic cell layout generation. Then, (2) we propose a systematic method to make use of those layouts to fix the routing failures caused by pin inaccessibility in the ECO (Engineering Change Order) routing stage. Experimental results demonstrate that our proposed cell layout diversification and replacement approach can fix metal-2 shorts by 93.22% in the ECO routing stage.