Masque README

Masque is a Python module for designing lithography masks.

The general idea is to implement something resembling the GDSII file-format, but with some vectorized element types (eg. circles, not just polygons) and the ability to output to multiple formats.

• Source repository
• PyPI

Installation

Requirements:

• python >= 3.11
• numpy
• klamath (used for GDSII i/o)

Optional requirements:

• ezdxf (DXF i/o): ezdxf
• oasis (OASIS i/o): fatamorgana
• svg (SVG output): svgwrite
• visualization (shape plotting): matplotlib
• text (Text shape): matplotlib, freetype

Install with pip:

pip install 'masque[oasis,dxf,svg,visualization,text]'

Overview

A layout consists of a hierarchy of Patterns stored in a single Library. Each Pattern can contain Refs pointing at other patterns, Shapes, and Labels.

masque departs from several "classic" GDSII paradigms:

• Layer info for Shapess and Labels is not stored in the individual shape and label objects. Instead, the layer is determined by the key for the container dict (e.g. pattern.shapes[layer]).
  • This simplifies many common tasks: filtering Shapes by layer, remapping layers, and checking if a layer is empty.
  • Technically, this allows reusing the same shape or label object across multiple layers. This isn't part of the standard workflow since a mixture of single-use and multi-use shapes could be confusing.
  • This is similar to the approach used in KLayout
• Ref target names are also determined in the key of the container dict (e.g. pattern.refs[target_name]).
  • This similarly simplifies filtering Refs by target name, updating to a new target, and checking if a given Pattern is referenced.
• Pattern names are set by their containing Library and are not stored in the Pattern objects.
  • This guarantees that there are no duplicate pattern names within any given Library.
  • Likewise, enumerating all the names (and all the Patterns) in a Library is straightforward.
• Each Ref, Shape, or Label can be repeated multiple times by attaching a repetition object to it.
  • This is similar to how OASIS reptitions are handled, and provides extra flexibility over the GDSII approach of only allowing arrays through AREF (Ref + repetition).
• Labels do not have an orientation or presentation
  • This is in line with how they are used in practice, and how they are represented in OASIS.
• Non-polygonal Shapes are allowed. For example, elliptical arcs are a basic shape type.
  • This enables compatibility with OASIS (e.g. circles) and other formats.
  • Shapes provide a .to_polygons() method for GDSII compatibility.
• Most coordinate values are stored as 64-bit floats internally.
  • 1 earth radii in nanometers (6e15) is still represented without approximation (53 bit mantissa -> 2^53 > 9e15)
  • Operations that would otherwise clip/round on are still represented approximately.
  • Memory usage is usually dominated by other Python overhead.
• Pattern objects also contain Port information, which can be used to "snap" together multiple sub-components by matching up the requested port offsets and rotations.
  • Port rotations are defined as counter-clockwise angles from the +x axis.
  • Ports point into the interior of their associated device.
  • Port rotations may be None in the case of non-oriented ports.
  • Ports have a ptype string which is compared in order to catch mismatched connections at build time.
  • Ports can be exported into/imported from Labels stored directly in the layout, editable from standard tools (e.g. KLayout). A default format is provided.

Glossary

• Library: A collection of named cells. OASIS or GDS "library" or file.
• Pattern: A collection of geometry, text labels, and reference to other patterns. OASIS or GDS "Cell", DXF "Block".
• Ref: A reference to another pattern. GDS "AREF/SREF", OASIS "Placement".
• Shape: Individual geometric entity. OASIS or GDS "Geometry element", DXF "LWPolyline" or "Polyline".
• repetition: Repetition operation. OASIS "repetition". GDS "AREF" is a Ref combined with a Grid repetition.
• Label: Text label. Not rendered into geometry. OASIS, GDS, DXF "Text".
• annotation: Additional metadata. OASIS or GDS "property".

TODO

• Better interface for polygon operations (e.g. with pyclipper)
  • de-embedding
  • boolean ops
• Tests tests tests
• check renderpather
• pather and renderpather examples