Requirements for Antenna Calculation

This section describes the technology file requirements for using the antenna calculation capabilities of Abstract Generator.

In the technology file on OpenAccess 2.2, the antenna rules have been moved to the antennaModels section of the foundry constraint group. You specify a separate antennaModels group for each oxide type and can specify antennaModels for up to four oxide types.

If an alternate foundry constraint group (AFCG) is defined in the .cdsenv file, Abstract Generator replaces the foundry constraint group and uses the specified AFCG instead.

You can specify an AFCG by setting the following environment variable in your .cdsenv file:

cdba.layout AlternateFoundryCG string "AFCG_name"

The constraint specifies the antenna ratios for one oxide type corresponding to a specific thickness of the gate oxide. You can specify the thickness value in the techLayerProperties subsection in the layerDefinitions section if antenna side area calculation is to be performed.

In OpenAccess, you must specify either side antenna values or non-side antenna values. OpenAccess supports only one of them at a time.

During the Extract step, the following factors are supported while calculating the antenna value. These factors are defined in the antennaModels section of the foundry constraint group in the technology file.

(antennaCutFactor) cumulativeRoutingPlusCut
If this factor is found in the technology file, the values of the cumulative antenna ratio for CUT layers are dumped in the LEF file. In addition, the values of the cumulative antenna ratio for CUT layers are added to the cumulative antenna ratio values of the metal layers. This factor has a boolean value. By default, this factor is set to nil.
(antennaMetalFactor) diffArea
If this factor is found in the technology file, Abstract Generator uses the value of this factor to calculate the cumulative antenna ratio values for the metal layers. However, if this factor is not found in the technology file, Abstract Generator sets it to the default value 1.0 and calculates the cumulative antenna ratio values. This factor has float values.
(antennaDiffPlusFactor) diffPlus
If this factor is found in the technology file, Abstract Generator uses the value of this factor to calculate the cumulative antenna ratio values for the metal layers. However, if this factor is not found in the technology file, Abstract Generator sets it to the default value 0.0 and calculates the cumulative antenna ratio values. This factor has float values.
(antennaDiffMinusFactor)) diffMinus
If this factor is found in the technology file, Abstract Generator uses the value of this factor to calculate the cumulative antenna ratio values for the metal layers. However, if this factor is not found in the technology file, Abstract Generator sets it to the default value 0.0 and calculates the cumulative antenna ratio values. This factor has float values.
(antennaDiffAreaReduceFactor) diffAreaReduce
If this factor is found in the technology file, Abstract Generator uses the value of this factor to calculate the cumulative antenna ratio values for the metal layers. However, if this factor is not found in the technology file, Abstract Generator sets it to the default value 1.0 and calculates the cumulative antenna ratio values. The values for this factor are given in the form of 1-D table.

The formula used to calculate the cumulative antenna ratio values for the metal layers is as follows:

areaCar[j] += (((antennaMetalFactor*cumMetalArea) + (antennaCutFactor*cumCutArea)) * antennaDiffAreaReduceFactor - diffArea * antennaDiffMinusFactor)/(cumGateAreaSharingCharge_[j] + antennaDiffPlusFactor * diffArea);

Example

constraintGroups(
 ( "foundry"
   antennaModels(
   ;( model
   ;( ----
    ( "default"
      antenna(
      ;( ratioName           layer       value )
      ;( ---------              -----          ----- )
       ( areaRatio      METAL1         0.345                  )
       ( diffAreaRatio  METAL1   ((0.45 0.4)(0.55 0.6))      )
       ( areaRatio      VIA1           0.344                     )
       ( diffAreaRatio  VIA1     ((0.44 0.5)(0.57 0.8))      )
      ) ;antenna

      cumulativeMetalAntenna(
      ;( ratioName               value )
      ;( ---------               ----- )
       ( areaRatio         0.544 'side      )    
       ( diffAreaRatio     0.888               ) 
      ) ;cumulativeMetalAntenna

      cumulativeViaAntenna(
      ;( ratioName                             value )
      ;( ---------                             ----- )
       ( areaRatio         0.654 'side        )
       ( diffAreaRatio     0.884                              )
      ) ;cumulativeViaAntenna
    ) ;default

    ( "second"
      antenna(
      ;( ratioName           layer       value )
      ;( ---------              -----          ----- )
       ( areaRatio      METAL1         1.345 'side                )
       ( diffAreaRatio  METAL1   ((0.455 0.4)(0.555 0.65))      )
      ) ;antenna

antenna( 
( areaRatio "poly" <value> ) 
); antenna 

      cumulativeMetalAntenna(
      ;( ratioName               value )
      ;( ---------               ----- )
       ( areaRatio         3.564                ) 
       ( diffAreaRatio     7.888               ) 
      ) ;cumulativeMetalAntenna

      cumulativeViaAntenna(
      ;( ratioName                             value )
      ;( ---------                             ----- )
       ( areaRatio         7.654                              )
       ( diffAreaRatio     1.884                              )
      ) ;cumulativeViaAntenna
    ) ;second

    ( "third"
      antenna(
      ;( ratioName           layer       value )
      ;( ---------              -----          ----- )
       ( areaRatio      METAL1         0.343                      )
       ( diffAreaRatio  METAL1   ((0.43 0.3)(0.53 0.6))         )
      ) ;antenna

      cumulativeMetalAntenna(
      ;( ratioName               value )
      ;( ---------               ----- )
       ( areaRatio         9.765 'side      )    
       ( diffAreaRatio     0.188               ) 
      ) ;cumulativeMetalAntenna

      cumulativeViaAntenna(
      ;( ratioName                             value )
      ;( ---------                             ----- )
       ( areaRatio         3.22                                                       )
       ( diffAreaRatio    ((0.421 0.4)(0.7 0.64)(0.81 0.59))                   )
      ) ;cumulativeViaAntenna
    ) ;third

    ( "fourth"
      antenna(
      ;( ratioName           layer       value )
      ;( ---------              -----          ----- )
       ( areaRatio      METAL2         0.645 'side                )
       ( diffAreaRatio  METAL2   ((0.47 0.4)(0.55 0.7))         )
      ) ;antenna

      cumulativeMetalAntenna(
      ;( ratioName               value )
      ;( ---------               ----- )
       ( areaRatio         0.6                          )    
       ( diffAreaRatio     ((0.127 0.23)(0.32 0.7))     )    
      ) ;cumulativeMetalAntenna

      cumulativeViaAntenna(
      ;( ratioName                             value )
      ;( ---------                             ----- )
       ( areaRatio         9.67             )
       ( diffAreaRatio     0.684                   )
      ) ;cumulativeViaAntenna
    ) ;fourth

      ( "factors"
      ( cumulativeRoutingPlusCut "METAL1" t )
      ( area "METAL1" 0.50 )
      ( diffPlus "METAL1" 0.60 )
      ( diffMinus "METAL1" 0.70 )
      ( diffAreaReduce "METAL1" (
      ( 0.0 20.0 )
      ( 0.5 30.0 )
      ( 1.0 40.0 )
    ))
    ) ;factors
  ) ;antennaModels 
      
   ) ;antennaModels
 ) ;foundry
) ;constraintGroups

Virtuoso Abstract Generator User Guide
Product Version IC23.1, November 2023