Parasitic extraction
Encyclopedia
In electronic design automation
, parasitic extraction is calculation of the parasitic effects in both the designed devices and the required wiring interconnects of an electronic circuit
: detailed device parameters, parasitic capacitance
s, parasitic resistances and parasitic inductances, commonly called parasitic devices, parasitic components, or simply parasitics.
The major purpose of parasitic extraction is to create an accurate analog model of the circuit, so that detailed simulations can emulate actual digital and analog circuit responses. Digital circuit responses are often used to populate databases for signal delay and loading calculation such as: timing analysis; circuit simulation; and signal integrity
analysis. Analog circuits are often run in detailed test benches to indicate if the extra extracted parasitics will still allow the designed circuit to function.
s the impact of the wiring was negligible, and wires were not considered as electrical elements of the circuit. However below the 0.5-micrometre
technology node resistance and capacitance of the interconnects started making a significant impact on circuit performance. With shrinking process technologies inductance effects of interconnects became important as well.
Major effects of interconnect parasitics include: signal delay , signal noise , IR drop.
run), and a cross sectional understanding of these layers. This information is used to create a set of layout wires that have added capacitors where the input polygons and cross sectional structure indicate. The output netlist contains the same set of input nets as the input design netlist and adds parasitic capacitor devices between these nets.
run), and a cross sectional understanding of these layers including the resistivity of the layers. This information is used to create a set of layout sub.wires that have added resistance between various sub-parts of the wires. The above Intererconnect Capacitance is divided and shared amongst the sub-nodes in a proportional way. Note that unlike Interconnect Capacitance, Interconnect Resistance needs to add sub-nodes between the circuit elements to place these parasitic resistors. This can greatly increase the size of the extracted output netlist and can cause additional simulation problems.
(previously from Avanti
) is a universal parasitics extractor tool applicable for a full range of electronic designs.
Electronic design automation
Electronic design automation is a category of software tools for designing electronic systems such as printed circuit boards and integrated circuits...
, parasitic extraction is calculation of the parasitic effects in both the designed devices and the required wiring interconnects of an electronic circuit
Electronic circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow...
: detailed device parameters, parasitic capacitance
Parasitic capacitance
In electrical circuits, parasitic capacitance, stray capacitance or, when relevant, self-capacitance , is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other...
s, parasitic resistances and parasitic inductances, commonly called parasitic devices, parasitic components, or simply parasitics.
The major purpose of parasitic extraction is to create an accurate analog model of the circuit, so that detailed simulations can emulate actual digital and analog circuit responses. Digital circuit responses are often used to populate databases for signal delay and loading calculation such as: timing analysis; circuit simulation; and signal integrity
Signal integrity
Signal integrity or SI is a set of measures of the quality of an electrical signal. In digital electronics, a stream of binary values is represented by a voltage waveform. However, digital signals are fundamentally analog in nature, and all signals are subject to effects such as noise,...
analysis. Analog circuits are often run in detailed test benches to indicate if the extra extracted parasitics will still allow the designed circuit to function.
Background
In early integrated circuitIntegrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
s the impact of the wiring was negligible, and wires were not considered as electrical elements of the circuit. However below the 0.5-micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
technology node resistance and capacitance of the interconnects started making a significant impact on circuit performance. With shrinking process technologies inductance effects of interconnects became important as well.
Major effects of interconnect parasitics include: signal delay , signal noise , IR drop.
Interconnect capacitance extraction
Interconnect capacitance is calculated by giving the extraction tool the following information: the top view layout of the design in the form of input polygons on a set of layers; a mapping to a set of devices and pins (from a Layout Versus SchematicLayout versus schematic
The Layout Versus Schematic is the class of electronic design automation verification software that determines whether a particular integrated circuit layout corresponds to the original schematic or circuit diagram of the design.-Background:...
run), and a cross sectional understanding of these layers. This information is used to create a set of layout wires that have added capacitors where the input polygons and cross sectional structure indicate. The output netlist contains the same set of input nets as the input design netlist and adds parasitic capacitor devices between these nets.
Interconnect resistance extraction
Interconnect resistance is calculated by giving the extraction tool the following information: the top view layout of the design in the form of input polygons on a set of layers; a mapping to a set of devices and pins (from a Layout Versus SchematicLayout versus schematic
The Layout Versus Schematic is the class of electronic design automation verification software that determines whether a particular integrated circuit layout corresponds to the original schematic or circuit diagram of the design.-Background:...
run), and a cross sectional understanding of these layers including the resistivity of the layers. This information is used to create a set of layout sub.wires that have added resistance between various sub-parts of the wires. The above Intererconnect Capacitance is divided and shared amongst the sub-nodes in a proportional way. Note that unlike Interconnect Capacitance, Interconnect Resistance needs to add sub-nodes between the circuit elements to place these parasitic resistors. This can greatly increase the size of the extracted output netlist and can cause additional simulation problems.
Tools and vendors
The tools fall into the following broad categories.- Field solvers provide physically accurate solutions. They calculate electromagnetic parameters by directly solving Maxwell's equationsMaxwell's equationsMaxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies.Maxwell's equations...
. Due to high calculation burden they are applicable only very small designs or to parts of the designs. - Approximate solutions with pattern matching techniques are the only feasible approach to extract parasitics for complete modern integrated circuit designs.
FastCap, FastHenry
FastCap and FastHenry, from MIT (Massachusetts Institute of Technology) are two free parasitics extractor tools for capacitance, and inductance and resistance. Quoted in many scientific articles, are considered golden references in their field. Windows versions with viewer and editor are freely available from FastFieldSolvers.Star-RCXT
Star-RCXT from SynopsysSynopsys
Synopsys, Inc. is one of the largest companies in the Electronic Design Automation industry. Synopsys' first and best-known product is Design Compiler, a logic-synthesis tool. Synopsys offers a wide range of other products used in the design of an application-specific integrated circuit...
(previously from Avanti
Avanti Corporation
Avanti Corporation was an electronic design automation company, purchased by Synopsys in 2002...
) is a universal parasitics extractor tool applicable for a full range of electronic designs.