FDSOI Support in Abstract Generator

A Fully Depleted Silicon-On-Insulator (FDSOI) connectivity stack is formed when a thin, fully depleted Silicon channel (SOI) and the diffusion (RX) are insulated from the substrate and wells by a buried oxide (box).

Abstract Generator recognizes the FDSOI process nodes, and for such designs, it includes the FDSOI pseudo-gate area as part of the antenna data calculation.

Identification of FDSOI Process Nodes

Abstract Generator checks whether a design is a valid FDSOI process node by evaluating the following:

The status of the ExtractAntennaIsSOIProcess option is set to TRUE. The default value is FALSE.
The Geometry Specification values in the Layer Assignment for Antenna Extraction table are valid.

Alternatively, you can use ExtractAntennaLayers as shown in the following example.
The geometrical specifications for diffusion layers are set to conducting materials.
```
ExtractAntennaLayers = "(RX ((RX andnot Poly))) (RX2 ((RX2 andnot Poly)))"
```
If the geometrical specification is evaluated as empty, the design is an FDSOI node. If the geometrical specification is evaluated as non-empty, the design is a bulk node.
The Geometry Specification values in the Layer Assignment for Antenna Regions table are valid.

Alternatively, you can use ExtractAntennaDrain as shown in the following example.
ExtractAntennaDrain specifies the geometrical specification for each diffusion layer over bulk.
```
ExtractAntennaDrain = "(RX ((RX andnot Poly) and BOXOPEN)) (RX2((RX2 andnot Poly) and BOXOPEN))"
```
```
ExtractAntennaOxide = "(RX Oxide 1) (RX2 Oxide 2)"
```
The drain geometrical specification identifies the bulk diffusion nodes by inclusion of the box opening layer.
Ensure to specify the correct box opening layer as a part of the ExtractAntennaDrain geometrical specifications.

FDSOI Pseudo-gate Area Calculation

Pseudo-gates are gate areas characterized by the connectivity of associated adjacent FDSOI diffusion areas with regular unprotected gate areas. If the ExtractAntennaIsSOIProcess option is set to TRUE, the contribution of an FDSOI pseudo-gate area is included while determining the ANTENNAGATEAREA.

The following figure shows the inclusion of the pseudo-gate area during the antenna data calculation.

The FDSOI pseudo-gate area contributes to ANTENNAGATEAREA and not ANTENNADIFFAREA. This is because while transferring charge from diffusion to the adjacent gate, the presence of a buried oxide (insulator) prevents the charge from escaping into the bulk. Abstract Generator recognizes the presence of single and multiple adjacent pseudo-gates and calculates ANTENNAGATEAREA accordingly.

During FDSOI pseudo-gate area calculation, the gate area is considered only once if the gate is shared by the two nodes from the same net. The gate area is set to zero if the gate and drain are shorted.

Consider nodes A, B, and C. The following table shows how pseudo-gate area is calculated depending on the connectivity of adjacent diffusions to the gate.

Technology File Updates

To enable Abstract Generator to calculate antenna data, you need to update the antennaModels section of the foundry constraint group. You can specify the thickness value in the techLayerProperties subsection of the layerDefinitions section if antenna side area calculation is to be performed.

Abstract Generator supports the calculation of process antenna information for LEF versions 5.4 and above. It cannot compute process antenna information for LEF version 5.3.

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