Method for Identifying Donut-Shaped Metal Wiring in VLSI Graphic Data
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
In the back end of a semiconductor processing line, metal wiring is often deposited using a lift-off process. The removal of the metal can not be guaranteed for a donut-shaped metal line. These donut-shapes must be flagged before the mask design is submitted to manufacturing so that the integrity of the design is not compromised. The previous method of flagging these donut-shapes is to first union the metal level and then check the resulting shapes for inside topologies, as shown in Fig. 1. The inside topologies are then brought to the layout person's attention so that the design may be corrected. The following problems could cause the layout to be uncheckable for donut-shaped wiring: 1. In order for shapes to be unionized, the layout data must be unnested. Unnesting of layout data can generate large amounts of "flattened" data.