Workflow#

You’ll need 2 windows:

  1. A text editor or IDE (Visual Studio Code, Pycharm, Spyder, neovim, Atom, Jupyterlab …)

  2. Klayout to Visualize the GDS files.

Component.show() will stream the GDS to klayout so klayout needs to be open. Make sure you also ran gf tool install from the terminal to install the gdsfactory to klayout interface.

1. Python Driven flow#

  1. You write your Pcells in python.

  2. You execute the python code.

  3. You visualize the GDS Layout in Klayout.

windows

2. YAML driven flow#

For building masks and complex circuits you can also use the netlist driven flow.

The best way to run the netlist driven flow is using a file watcher, where you keep a live process that updates your GDS file live.

  1. You write your netlist in YAML. It’s basically a Place and Auto-Route.

  2. You execute the file watcher gf yaml watch FolderName.

  3. You visualize the GDS Layout in Klayout.

yaml

Layers#

Each foundry uses different GDS numbers for each process step.

We follow the generic layer numbers from the book “Silicon Photonics Design: From Devices to Systems Lukas Chrostowski, Michael Hochberg”.

GDS (layer, purpose) layer_name Description
1 , 0 WG 220 nm Silicon core
2 , 0 SLAB150 150nm Silicon slab (70nm shallow Etch for grating couplers)
3 , 0 SLAB90 90nm Silicon slab (for modulators)
4, 0 DEEPTRENCH Deep trench
47, 0 MH heater
41, 0 M1 metal 1
45, 0 M2 metal 2
40, 0 VIAC VIAC to contact Ge, NPP or PPP
44, 0 VIA1 VIA1
46, 0 PADOPEN Bond pad opening
51, 0 UNDERCUT Undercut
66, 0 TEXT Text markup
64, 0 FLOORPLAN Mask floorplan

Layers are available in gf.LAYER as gf.LAYER.WG, gf.LAYER.WGCLAD

You can build PDKs for different foundries. The PDKs contain some foundry IP such as layer numbers, minimum CD, layer stack, so you need to keep them in a separate private repo. See UBC PDK as an example.

I recommend that you create the PDK repo using a cookiecutter template. For example, you can use this one.

pip install cookiecutter
cookiecutter https://github.com/joamatab/cookiecutter-pypackage-minimal

Or you can fork the UBC PDK and create new cell functions that use the correct layers for your foundry. For example.


from pydantic import BaseModel


class LayerMap(BaseModel):
    WGCORE = (3, 0)
    LABEL = (100, 0)
    DEVREC: Layer = (68, 0)
    LABEL: Layer = (10, 0)
    PORT: Layer = (1, 10)  # PinRec
    PORTE: Layer = (1, 11)  # PinRecM
    FLOORPLAN: Layer = (99, 0)

    TE: Layer = (203, 0)
    TM: Layer = (204, 0)
    TEXT: Layer = (66, 0)
    LABEL_INSTANCE: Layer = (66, 0)


LAYER = LayerMap()