Virtuoso XL Layout Editor User Guide

Setting Up Device Abutment for Virtuoso XL Layout Editor

Creating CMOS Pcells to Use with Abutment

To create pcells that have a built-in abutment capability, follow these steps.

1.Create a pcell specifically for abutment.

Editing an existing pcell for abutment is much more difficult than creating a new one for the purpose.

2.Add the following abutment parameters to the pcell.

Conditional inclusion or exclusion of contacts

This parameter adds or removes the contact. You can conditionally include or exclude the contacts and connecting metal tab. You must conditionally exclude these features if you are creating a graphical pcell. The pcell parameter must remove all features that are required for metal hookup and leave only the diffusion material to be stretched. For CMOS device abutment, you add this property to both the drain and the source sides of the device.

Gate pin identification

This parameter identifies the gate pins so the abutment software knows where the edge of the gate is. In this example, the value G is the name of the gate net inside the pcell.

Virtuoso XL Layout Editor User Guide

Setting Up Device Abutment for Virtuoso XL Layout Editor

Access direction identification

This parameter identifies the abutment access direction. Valid access directions are left, right, bottom, and top. This variable should contain only reasonable values. If access is only from the right, then add only that value.

Note: Access is from the right or the left.

Stretchable material

This parameter stretches the material toward or away from the gate when the instance is altered for abutment. The default value of the stretch parameter must be the distance from the edge of the material to the edge of the gate. Numeric values are in user units.

Virtuoso XL Layout Editor User Guide

Setting Up Device Abutment for Virtuoso XL Layout Editor

list ("abutRule1Ext" 0.75) list ("abutRule2Ext" 1.0) list ("abutContactExt" 3.0))

The first element in the list drainStretch( ) is the name of the stretchable material parameter. You name this parameter yourself to identify the material to be stretched.

The second element in the list (abutMinExt) is the rule for minimum diffusion overhang from the edge of the poly gate. The argument to this element (0.5) is the rule value.

Virtuoso XL Layout Editor User Guide

Setting Up Device Abutment for Virtuoso XL Layout Editor

The third element in the list (abutRule1Ext) is the poly-layer-to-poly-layer rule. This rule is used when the net connecting the two instances does not share the net with any other pin.

The fourth element in the list (abutRule2Ext) is the poly-layer-to-diffusion rule. The rule is used when the gate width is different for the two instances being abutted.

The fifth element in the listabutContactExt( ) is the diffusion extension value used when one of the contacts needs to be added during the abutment process. With the contacts off by default, the abutment program needs to know how close to move the selected cell to abut properly.