Note on Process Design Kit

Introduction

A Process Design Kit (PDK) is a collection of design layouts that serve as reusable modules, helping to accelerate the design and development of integrated circuits. This guide explains how to embed a PDK into a GDS design layout using the gdspy Python library.

Suppose you have a PDK packaged in a GDS file named test_pdk.gds. The following example shows how to import the PDK and insert it at a specific location in your design:

import gdspy

# Create a new GDS library and main cell
lib = gdspy.GdsLibrary()
main_cell = lib.new_cell('main_cell')

# Import the PDK from the GDS file
pdk_lib = lib.read_gds("test_pdk.gds")

# Remove the context info cell to avoid conflicts
lib.remove("$$$CONTEXT_INFO$$$")

# Specify where to place the PDK cell in the layout
port_position = (0, 0)

# Reference the cell to import from the PDK and add it to the main cell
pdk_cell_ref = gdspy.CellReference(
pdk_lib.cells["cell_to_import"],
port_position
)
main_cell.add(pdk_cell_ref)

# Write the resulting design to an output GDS file
lib.write_gds("output.gds")

Explanation:

The code creates a new design layout with a cell named main_cell. It reads the PDK from test_pdk.gds and removes the $$$CONTEXT_INFO$$$ cell to prevent layer name conflicts. The PDK cell (cell_to_import) is inserted at the specified position (port_position) within the main cell. The final layout, with the PDK included as a subcell, is saved to output.gds.

This approach allows you to modularly incorporate PDK elements into your integrated circuit designs, streamlining the development process.