zeropdk 20.12

PDK factory for klayout

ZeroPDK

This is a pure-python PDK factory that enables klayout scripted layout. It assists in photonic integrated circuit layout, which relies on having specialized curved waveguides and non-square-corner shapes.

Installation

This package is heavily based on python's klayout package, still in beta version as of this writing (Jul 2019).

Installation with pip (virtual environment is highly recommended):

pip install zeropdk

Installation from source:

python setup.py install

Features

KLayout extension

By importing zeropdk, klayout is patched with a few useful functionalities. For example:

import klayout.db as kdb
import zeropdk

layout = kdb.Layout()
plogo = layout.read_cell(cell_name='princeton_logo', filepath='gdslibrary/princeton_logo_simple.gds')

# plogo is a cell in the current layout. It can be inserted in the top cell.

Easy technology layers definition

Based on a KLayout's layout properties file (.lyp) containing layer definitions, it is easy to import and use all layers. For example:

from zeropdk import Tech
lyp_path = "examples/EBeam.lyp"
EBeam = Tech.load_from_xml(lyp_path)
layerM1 = EBeam.layers["M1"]
print(layerM1, type(layerM1))  # M1 (41/0) <class 'klayout.dbcore.LayerInfo'>

The file above belongs to a project called SiEPIC EBeam PDK, used in passive silicon photonic foundries.

Advanced PCell definition

PCells can be hierarchical, as described in Sec. IV.C of this article. One PCell can use another PCell in its definition, and the parent pcell should, in this case, inherit the child's parameters. an example taken from zeropdk.default_library.io is:

class DCPadArray(DCPad):
    params = ParamContainer(pad_array_count, pad_array_pitch)

    def draw(self, cell):
        # ...
        for i in range(cp.pad_array_count):
            dcpad = DCPad(name=f"pad_{i}", params=cp)
        return cell, ports

In this case, DCPadArray simply places an array of DCPad Pcells, and contains parameters pad_array_count and also pad_array_pitch, but also the parameters belonging to DCPad, such as layer_metal and layer_opening.

In the EBeam PDK example, one can edit adapt a standard library of pcells to its own parameter sets. For example, EBeam PDK uses particular layers for its metal deposition and oxide etch steps. So the DCPadArray can be changed via the following:

class DCPadArray(DCPadArray):
    params = ParamContainer(
        PCellParameter(
            name="layer_metal",
            type=TypeLayer,
            description="Metal Layer",
            default=EBeam.layers["M1"],
        ),
        PCellParameter(
            name="layer_opening",
            type=TypeLayer,
            description="Open Layer",
            default=EBeam.layers["13_MLopen"],
        ),
    )

TODO: adapt example provided here to zeropdk.

Photonics-inspired layout functions

Several assistive tools for handling photonic shapes. For example, it is desired, sometimes, to draw a waveguide with progressive widths (a taper).

from zeropdk.layout import layout_waveguide
wav_polygon = layout_waveguide(cell, layer, points_list, width)

Developer notes

This project is still under development phase. See the development notes for more information.