End of line spacing
end of line spacing与diff net via_cut spacing都代表着一类drc问题，根据tech file的相关约束确定具体的spacing要求。
end of line spacing指的是end of line edge与相邻的同层金属的spacing要求，其中end of line edge定义为两个相邻凸角的公共边宽度小于阈值时被称为end of line edge，如下图所示，此时end of line edge所在的金属线就被称为end of line wire。
根据tech file约束具体细分可以分为以下情况:
• End-of-Line to End-of-Line Spacing Rule
• One-Neighbor End-to-End Table-Based Spacing Rule
• One-Neighbor End-of-Line Spacing Rule
• Preferred and Nonpreferred End-of-Line Spacing Rule
• Two-Neighbor End-of-Line Spacing Rule
• Three-Neighbor End-of-Line Spacing Rule
• Three-Neighbor End-of-Line Cap Rule
• Single-Side Isolated Neighbor End-of-Line Spacing Rule
• Two-Sided End-of-Line Spacing Rule
• Two-Sided End and Joint Spacing Rule
• End-of-Line Two-Corner Keepout Rule
• End-of-Line Spacing Rule and Stub Modes
• Enhanced Dense End-of-Line Spacing Rule
• L-Shaped End-of-Line Spacing Rule
• End-of-Line to Concave Corner Spacing Rule
具体可以参考Synopsys Technology File and Routing Rules Reference Manual文档。