Discussion of GDS format

Web data books

Further information

The cell layout is provided in GDS format in a file written from Magic. It can be viewed using Alliance Dreal. A README file in the cell directory can be sourced to set up the environment variables properly.

cd pharosc/magic/gds/vsclib013
source ./README

The REF layers which define the hit points for the place and route software are missing from the GDS file. This is because they are not present in the Magic file because they are not a real physical layer.

They aren't written in the CIF file from Magic either, but a script copies the geometries over from the Alliance CIF file.

The GDS layer mapping is shown below.

PWELL  41  P well
NWELL  42  N well
NDIF    3  N diffusion inside P well
PDIF    4  P diffusion inside N well
NTIE    5  N diffusion inside N well
PTIE    6  P diffusion inside P well
ACTIV  43  All diffusion layers
PIMP   44  P implant
NIMP   45  N implant
POLY   46  Polysilicon for gate and interconnect
CONT   25  Contact Metal-1 to poly and diffusion
ALU1   49  Metal-1
VIA1   50  Via Metal-1 to Metal-2
ALU2   51  Metal-2
VIA2   61  Via Metal-2 to Metal-3
ALU3   62  Metal-3
VIA3   30  Via Metal-3 to Metal-4
ALU4   31  Metal-4
VIA4   32  Via Metal-4 to Metal-5
ALU5   33  Metal-5
VIA5   36  Via Metal-5 to Metal-6
ALU6   37  Metal-6

Example of GDS cell showing the separate N and P diffusion layers.

GDS cell example with separate diffusions

Example of GDS cell showing a single diffusion layer and separate N and P implant layers.