Layout versus Schematic with Design/Magnetic Rule Checking for Superconducting Integrated Circuit Layouts

Abstract

The IARPA SuperTools program has accelerated the development of superconductor integrated circuit design tools. Superconductor integrated circuits contain Josephson junctions and rely heavily on inductive interconnects and coupled inductors, all of which are not adequately supported by conventional semiconductor layout-versus-schematic verification (LVS) tools. Such circuits are also susceptible to failure in the presence of magnetic fields above about one tenth of the Earth's field strength and to magnetic flux trapped in layout structures during cool-down, so that magnetic rule checking (MRC) is essential. Under SuperTools we developed an open-source LVS framework, SPiRA, which allows for the parametric creation, alteration and verification of superconductor and quantum circuit layouts. SPiRA is a Python-based framework developed to aid the process of creating parameterized layouts while simultaneously taking into account design rule (DRC) as well as magnetic rule checking. SPiRA is designed to accept any process through a rule deck database (RDD) Python-based PDK schema from which cells are spawned as objects with inherent properties. This process allows rapid implementation of changes to layouts with the ability to extract an electrical netlist that can be simulated, and parameter extraction performed upon. SPiRA creates layouts in the GDSII layout format and allows quick visualization of the layout using the Gdspy library. We present extraction results for examples created parametrically with SPiRA, compare those to results for layouts created by hand and evaluate the capabilities of SPiRA. Finally we show how SPiRA improves models for inductance and compact model extraction with the inductance extraction tool InductEx.