under the transistor is extremely thin; the problem did not exist at 0.35um. Even if the charge does not discharge to the body, it stays in the oxide as a hot carrier and shifts the threshold voltage.
Antenna elimination methods include splitting the metal and routing the offending portion on a higher layer, or inserting an antenna diode to provide a discharge path, which costs some area and routing.
Antenna ratio is the ratio of the physical conductor area to the total gate-oxide area it is electrically connected to. A higher ratio means a greater chance of failing due to the antenna effect; a typical metal antenna ratio limit is around 500.
Wire spreading is related: random particle defects during manufacturing can cause shorts or opens on routes and reduce yield. The regions prone to such shorts/opens are called critical areas. Spreading wires distributes them more evenly to improve yield against random particle defects. Pushing routes off-track by a fraction of a pitch can reduce short critical area but may increase open critical area; widening wires instead avoids increasing open critical area, and frozen nets are not moved.
KEY The antenna effect is gate-oxide damage from charge on floating interconnect; fix it with metal splitting, layer jumps or antenna diodes.
Wire Spreading Before Antenna Fixing
- It is not recommended because, after DRC, antenna fixing has the highest priority.
- Wire spreading pushes routes off-track and may not leave enough routing resources to fix antenna violations afterward.
KEY Wire spreading first can consume the routing resources needed to fix antenna violations, which take higher priority.
Wire Spreading and Metal Layers
- Wire spreading pushes wires off the track if space is available; it does not switch layers to enable that pushing.
- However, a Search and Repair run after wire spreading may make