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The built-in simple constraint definition oaCumMetalAntenna specifies the maximum antenna ratios for one or more antenna models (oxide thicknesses) for area values accumulated through all the poly and metal layers attached to a gate. This constraint holds a value that specifies the maximum allowed ratio of this cumulative sum to the gate area (gateAreaRatio), and specifies how that maximum ratio changes if a diode is present on the wire (diodeAreaRatio).
| Constraint type: | oaSimpleConstraint |
| Value types: | oaAntennaRatioValue, oaAntennaRatioArrayValue |
| Database types: | oaTech |
| Object types: | oaAppObject |
The following value types are supported by this constraint:
oacCumViaAntenna constraints have an oaAntennaRatioValue if only the default antenna model is represented. The oaAntennaRatioValue object has functions to set and retrieve both the gate and diode area ratios.
The gate area ratio is a float indicating the maximum cumulative antenna ratio, where the antenna area is the area of the metal wire that is not connected to the diffusion diode.
The diode area ratio is the maximum cumulative antenna ratio calculated where the antenna area is the area of the metal wire that is connected to the diffusion diode. This ratio can be dependent on the diode area and is represented by a one dimensional lookup table whose key is the diode area in database units squared, and value is the cumulative antenna ratio. In the simplest case, this table degenerates to one value.
The oaAntennaRatioValue object also contains isSide() method for indicating whether the antenna area should be calculated as the perimeter (the area of the sides of the process antenna) or the drawn area (the top surface area of the process antenna).
Units: Antenna
The oaAntennaRatioArrayValue is used when more than one antenna model is represented. The oaAntennaRatioArrayValue object simply represents a set of oaAntennaRatioValues that can be set and retrieved by antenna model.
Units: Antenna
Antenna rules limit the electrical charges that build up during metal processing, such as plasma etching processes. Without these limits, the probability that the built-up charges might break through gate oxides increases greatly. Some processes have multiple gate oxides. These different thicknesses allow for different amounts of charge resistance. This is why multiple oxide models are available.
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