International Business Machines Corporation

Patrick M Williams

David James Hathaway

Jason David Morsey

Steven Eugene Washburn

Jun Zhou

Chandramouli Visweswariah

Tsz-mei Ko

David J Widiger

Lewis William Dewey, Iii

Cindy ShuiKing Washburn

Lawrence Kenneth Lange

Thomas G Mitchell

Lars W Liebmann

Shreesh Narasimha

James Douglas Warnock

K Paul Muller

James A Culp

Michael H Wood

Joachim Keinert

Leon Jacob Sigal

Howard Harold Smith

Ibrahim M Elfadel

Adam P Matheny

Rajeev Malik

Vasant B Rao

Jeffrey Paul Soreff

Gregory Allen Northrop

Stephen Larry Runyon

Peter J Camporese

Susan Elizabeth Cellier

Adam R Jatkowski

Anthony D Hagin

Tarek A El-Moselhy

Ee K Cho

Mei-Ting Hsu

Ron D Rose

A system and method to perform an integrated circuit design involves selecting a net among a plurality of nets of the integrated circuit design as a victim net. Each net connects a pair of nodes of the integrated circuit design and each node represents a logic element of the integrated circuit design. The method also includes determining aggressor nets among the plurality of nets for the victim net and determining a corresponding weight value for each of the aggressor nets and, for each of the aggressor nets, multiplying the coupled noise originating from the aggressor net with the corresponding weight value to obtain a weighted coupled noise value. A cumulative coupled noise value is obtained for the victim net as a sum of the weighted coupled noise values associated with each of the aggressor nets. A result of the integrated circuit design is provided for fabrication into an integrated circuit.

Pessimism reduction in cross-talk noise determination used in integrated circuit design

A method, system, and computer product for performing a coupled noise analysis in an integrated circuit (IC) design include copying one or more victim circuit sections of a victim circuit in the IC, generating a blockage circuit section that represents a blockage aggressor circuit in the IC, using the copied one or more victim circuit sections of the victim circuit, determining at least one subcircuit from the blockage circuit section, selecting, for a victim pin on the victim circuit, a power-driven virtual node on the at least one subcircuit, applying a power source to the power-driven virtual node on the at least one subcircuit, calculating a coupled noise at the victim pin contributed by the at least one subcircuit in response to the power source being applied, comparing the coupled noise to a threshold noise level, and altering the IC design when the coupled noise exceeds the threshold noise level.

Pessimism reduction in hierarchical blockage aggressors using estimated resistor and capacitor values

A computer-implemented method for extracting a capacitance for a target wire of an integrated circuit includes receiving a design of the integrated circuit having a plurality of wiring layers and selecting a target wire to perform the capacitance extraction. The method further includes determining a first adjacent wiring layer and a second adjacent wiring layer and removing a first subset and a second subset of a plurality of non-adjacent wiring layers from the plurality of wiring layers. The method includes approximating a first plate to be used in the extraction based on the first subset of the plurality of non-adjacent wiring layers and approximating a second plate to be used in the extraction based on the second subset of the plurality of non-adjacent wiring layers and performing the extraction of the target wire based on the first and second adjacent wiring layers and the first and second plates.

Method for improving capacitance extraction performance by approximating the effect of distant shapes

Coupled noise from at least one out-of-context aggressor net of an integrated circuit design is computed for an out-of-context victim net. The nets are out-of-context with respect to a hierarchical noise analysis of the integrated circuit design. At least one of the nets is a continuation of a path which extends to at least one in-context portion of the integrated circuit design. An aggressor signal timing window is derived for the at least one out-of-context aggressor net; a victim signal timing window is derived for the out-of-context victim net; and a timing window and noise analysis is completed with the aggressor signal timing window and the victim signal timing window. The aggressor window is derived as a function of required arrival time of the at least one out-of-context aggressor net and/or the victim window is derived as a function of required arrival time of the out-of-context victim net.

Using required arrival time constraints for coupled noise analysis and noise aware timing analysis of out-of-context (OOC) hierarchical entities

A method, system, and computer product for performing a coupled noise analysis in an integrated circuit (IC) design include copying one or more victim circuit sections of a victim circuit in the IC design, generating a blockage circuit section that represents a blockage aggressor circuit in the IC design, using the copied one or more victim circuit sections of the victim circuit, determining at least one subcircuit from the blockage circuit section, selecting, for a victim pin on the victim circuit, a power-driven virtual node on the at least one subcircuit, applying a power source to the power-driven virtual node on the at least one subcircuit, calculating a coupled noise at the victim pin contributed by the at least one subcircuit in response to the power source being applied, comparing the coupled noise to a threshold noise level, and altering the IC design when the coupled noise exceeds the threshold noise level.

A system to design an integrated circuit and a method of fabricating an integrated circuit include performing a design change for a net among a plurality of nets of the integrated circuit. An extraction is performed for the net and includes re-computing values for a resistor-capacitor (RC) circuit representation of the net. Re-computed values resulting from the re-computing and a timestamp of the extraction are recorded. A capacitance value of a capacitor coupling the net with a neighboring net in the RC circuit representation of the neighboring net is changed to be the capacitance value of the capacitor coupling the net with the neighboring net that was re-computed for the RC circuit representation of the net. Timing and noise parameters are for the net and the neighboring net are updated to updated timing and noise parameters, and timing analysis is performed based on the updated timing and noise parameters.

Approximation of resistor-capacitor circuit extraction for thread-safe design changes

Computing the gradients of capacitances in an integrated circuit chip layout with respect to design and process parameters is described. Included is a shape processing engine in the form of a variational mapping engine and a capacitance calculation engine that includes a gradient calculation engine. The variational mapping engine translates physical parameter variations into variations on the edges of the elementary patterns to which the layout of the integrated circuit is decomposed. The gradient calculation engine computes capacitance gradients by combining information from two sources. The first source consists of pre-existing gradients in a capacitance lookup table. The second source consists of analytical expressions of capacitance correction factors.

Method for calculating capacitance gradients in VLSI layouts using a shape processing engine

The invention relates to an electromigration analysis method and a system for analyzing one or more nets in a digital integrated circuit design that are at risk of electromigration. The method comprises the steps of providing at least one interconnect between a driver cell and at least one load cell; applying same extracted netlist data for noise and/or timing analysis and for electromigration analysis; modeling the driver cell by a train of trapezoidal voltage pulses transmitted from the driver cell to the one or more load cells through the at least one interconnect; extracting at least a slew rate of a driver voltage signal and/or timing information from a noise and/or timing analysis for the one or more nets; and comparing a locally measured current density in the at least one interconnect to an effective local maximum current density limit of the at least one interconnect.

Method and system for electromigration analysis on signal wiring

Disclosed is a method for enhanced efficiency and effectiveness in achieving closure of large, complex, high-performance digital integrated circuits. Circuit macros are re-optimized and re-tuned in the timing closure loop by means of a reformulated objective function that allows the optimizer to improve the slack of all signals rather than just the most critical one(s). The incentive to improve the timing of a sub-critical signal is a diminishing function of the criticality of the signal. Thus all signals are improved during the optimization, with the highest incentive to improve on the most critical signals, leading to faster and more effective overall timing closure.

Method of achieving timing closure in digital integrated circuits by optimizing individual macros

An iterative timing analysis is analytically performed before a chip is fabricated, based on a methodology using optical proximity correction techniques for shortening the gate lengths and adjusting metal line widths and proximity distances of critical time sensitive devices. The additional mask is used as a selective trim to form shortened gate lengths or wider metal lines for the selected, predetermined transistors, affecting the threshold voltages and the RC time constants of the selected devices. Marker shapes identify a predetermined subgroup of circuitry that constitutes the devices in the critical timing path. The analysis methodology is repeated as often as needed to improve the timing of the circuit with shortened designed gate lengths and modified RC timing constants until manufacturing limits are reached. A mask is made for the selected critical devices using OPC techniques.

OPC trimming for performance

A hybrid linear wire model for tuning the transistor widths of circuits linked by RC interconnects is described. The method uses two embedded simulators during the tuning process on netlists that contain resistors (Rs). A Timing oriented simulator is used only for timing purposes on the original netlist that includes all the Rs. A Gradient oriented simulator is then run only on the modified netlist with all Rs shorted and within the iterative loop of the tuner to compute gradients. The present hybrid method achieves a significant improvement in computational speed. The Timing oriented simulator is fast and accurate for only timing netlists with Rs, but cannot compute gradients efficiently. The Gradient oriented simulator computes gradients efficiently but cannot do so in the presence of Rs. To prevent 'de-tuning' that typically occurs when all Rs are shorted, 'wire-adjusts' are provided that make the initial timing results using the Gradient oriented simulator on the shorted netlist match the timing results using Timing oriented simulator on the original netlist. This permits the optimizer sense initially the correct set of critical timing paths, and more significantly, it permits the wire-adjusts keep track of the changing transistor widths to guide the optimizer during the iterations until convergence is achieved.

Hybrid linear wire model approach to tuning transistor widths of circuits with RC interconnect

A Digital Design Method which may be automated is for obtaining timing closure in the design of large, complex, high-performance digital integrated circuits. The methodincludes the use of a tuner on random logic macros that adjusts transistor sizes in a continuous domain. To accommodate this tuning, logic gates are mapped to parameterized cells for the tuning and then back to fixed gates after the tuning. Tuning is constrained in such a way as to minimize 'binning errors' when the design is mapped back to fixed cells. Further, the critical sections of the circuit are marked in order to make the optimization more effective and to fit within the problem-size constraints of the tuner. A specially formulated objective function is employed during the tuning to promote faster global timing convergence, despite possibly incorrect initial timing budgets. The specially formulated objective function targets all paths that are failing timing, with appropriate weighting, rather than just targeting the most critical path. Finally, the addition of multiple threshold voltage gates allows for increased performance while limiting leakage power.

Method for tuning a digital design for synthesized random logic circuit macros in a continuous design space with optional insertion of multiple threshold voltage devices

Disclosed is a method for achieving timing closure in the design of a digital integrated circuit or system by selecting portions of the circuit or system to be optimized and portions of the circuit or system in which the effects of such optimization are to be analyzed during the optimization process. Optimized portions will include gates whose design parameters are to be changed, a first analyzed portion includes gates whose delays and edge slews are to be recomputed, and a second analyzed portion includes gates whose ATs and RATs are to be recomputed during optimization. Constraints are imposed at selected boundaries between these portions to prevent unwanted propagation of timing information and to ensure the validity of timing values used during optimization. Through this selection, the size of the problem posed to the underlying optimization method will be reduced, allowing larger circuits or systems to be optimized and allowing optimization to be performed more quickly.

Method of optimizing and analyzing selected portions of a digital integrated circuit

Disclosed is a method for enhanced efficiency and effectiveness in achieving timing closure of large, complex, high-performance digital integrated circuits. Circuit macros are re-optimized and re-tuned in the timing closure loop by means of a reformulated objective function that allows the optimizer to improve the slack of all signals rather than just the most critical one(s). The incentive to improve the timing of a sub-critical signal is a diminishing function of the criticality of the signal. Thus all signals are improved during the optimization, with the highest incentive to improve on the most critical signals, leading to faster and more effective overall timing closure.

A method (and a system for using the method) for automating a slew rate analysis between two or more circuits on a semiconductor chip. The method includes the steps of: receiving as input one or more input parameters characterizing the physical medium through which the signal propagation occurs (the net) and the electrical characteristics of signals transmitted between the circuits; and providing as output one or more output parameters characterizing the appropriate solution for physical implementation of the circuit(s) and net(s) which satisfy the performance requirements of the system. The receiving step can comprise any one of: providing a hierarchical signal name cross-reference defining a name for the signal for a given hierarchy level of the circuits; providing a set of one or more boolean equations used to generate the one or more output parameters from the one or more input parameters; providing a physical design information for the circuits; and providing a timing information for the signals. The boolean equations can include as input variables: the physical design information for the circuits; and the timing information for the signals. The transmitting step includes the steps of: determining if the signals require one or more buffers; determining if signal pin locations of the circuits through hierarchical levels thereof are not optimal; determining if strengths of transistors driving the signals must be increased; determining if the widths of wires used to transmit the signals must be increased; and determining if wires used to transmit the signals must be on less resistive wiring layers.

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Salt Point, NY, United States of America

Patrick M Williams