Superconducting Technology Assessment - nitrd

CAD
PRESENT CAD CAPABILITY
The integrated circuit design software developed by Stony Brook University and the University of Rochester was
integrated into a single software suite at Northrop Grumman. The readiness of U.S.-based design methodology and
CAD tools will be described in detail using the Northrop Grumman capability as an example. While built upon the
academic projects, it also leverages the methodology and software that serves the commercial semiconductor ASIC
world. Where possible, semiconductor standards were adhered to.
Circuit Design
VHDL
Schematic
LVS
DRC
Layout
RSFQ Gate Library
Gate
Pcells
Lmeter
Schematic
Malt
WRSpice
Symbol
VHDL
Structure
Layout
Netlist
VHDL
Generic
Fig. 1. Circuit design and verification, top, is distinct from logic gate library development, bottom. The chip foundry publishes the gate library
to serve all users. Customers construct complex circuits from the gates, to satisfy their unique performance goals.
In the following description we will repeatedly distinguish between the gate library developer and the circuit
designer. Division of labor between these two roles, illustrated in Figure 1, is among the most important steps in
design methodology. The role of the circuit designer is to architect, simulate and verify complex designs. This can
be accomplished without knowledge of all of the details of the device physics, foundry process, or CAD software.
As in the commercial ASIC world, device and gate libraries are published by the foundry. These include, at
minimum, device models for physical-level simulation and parameterized-cell (Pcell) physical layout of devices and
gates. Commercial foundries emphasize formal verification of designs submitted for fabrication. Therefore, the
foundry typically provides CAD-based design verification rules for design rule checking (DRC) and layout-versusschematic
(LVS). Some commercial foundries require clean DRC and LVS verification run files to be submitted with
the design prior to fabrication. The foundry may also perform additional verification checks and require design
modifications to physical layout before tooling.
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