Mutual inductance extraction using dipole approximations

• US 20050120316A1
• Filed: 10/21/2004
• Published: 06/02/2005
• Est. Priority Date: 10/21/2003
• Status: Active Grant

• Current Assignee: Siemens Industry Software Limited (Siemens AG)
• Original Assignee: Mentor Graphics Corporation (Siemens AG)
• Inventors: Ortiz, Salvador, Suaya, Roberto, Escovar, Rafael
• Granted Patent: US 7,496,871 B2
• Time in Patent Office: Days
• US Class Current: 716/115
• CPC Class Codes: G06F 30/367 Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods
• CPC Class Codes: G06F 30/398 Design verification or optimisation, e.g. using design rule check [DRC], layout versus schematics [LVS] or finite element methods [FEM] optical proximity correction [OPC] design processes G03F1/36

Abstract

Various methods for analyzing mutual inductance in an integrated circuit layout are disclosed. In one exemplary embodiment, for instance, a circuit description indicative of the layout of signal wires and ground wires in the circuit is received. The signal wires and the ground wires are grouped into at least a first bundle and a second bundle, wherein the first bundle and the second bundle each comprise a respective signal-wire segment and one or more corresponding ground-wire segments. A representative dipole moment is calculated for the first bundle. Using the representative dipole moment, the mutual inductance between the first bundle and the second bundle is calculated. Computer-readable media storing computer-executable instructions for causing a computer to perform any of the disclosed methods or storing design databases created or modified using any of the disclosed techniques are also disclosed.

Claims

1. A method for analyzing mutual inductance in a circuit, comprising:

receiving a description of the circuit, the description being indicative of the layout of signal wires, ground wires, and power wires in the circuit;

grouping at least a portion of the signal wires and the ground wires into at least a first bundle and a second bundle, the first bundle and the second bundle each comprising a respective signal-wire segment and one or more corresponding ground-wire segments;

calculating a representative dipole moment for the first bundle;

calculating a mutual inductance between the first bundle and the second bundle using the representative dipole moment; and

outputting the mutual inductance.

2. The method of claim 1, wherein the grouping is performed such that the one or more ground-wire segments of the first and second bundles have the same length as and are parallel to their respective signal-wire segments.

3. The method of claim 1, wherein the act of calculating the mutual inductance comprises calculating the magnetic flux due to the representative dipole moment of the first bundle through surfaces in the second bundle formed between the respective signal-wire segment of the second bundle and the corresponding ground-wire segments of the second bundle.

4. The method of claim 3, wherein the act of calculating the mutual inductance further comprises calculating a weighted average of the respective contributions of the surfaces.

5. The method of claim 1, wherein the representative dipole moment comprises a weighted average of dipole moments resulting from individual current loops in the first bundle, each individual current loop comprising the signal-wire segment of the first bundle and a respective one of the corresponding ground-wire segments of the first bundle.

6. The method of claim 1, wherein the one or more corresponding ground-wire segments in the first bundle and the second bundle are identified as being return paths for their respective signal-wire segments based at least in part on their resistance and separation relative to their respective signal-wire segment.

7. The method of claim 1, further comprising:

determining whether a distance between the first bundle and the second bundle is greater than a threshold distance; and

calculating the mutual inductance using the representative dipole moment only if the distance is greater than the threshold distance.

8. The method of claim 7, wherein the distance between the first bundle and the second bundle is the distance between a center-of-mass position of the first bundle and a center-of-mass position of the second bundle.

9. The method of claim 7, wherein the threshold distance is 20 micrometers.

10. The method of claim 1, further comprising:

evaluating whether a configuration of the corresponding ground-wire segments of the first bundle is symmetrical with respect to the signal-wire segment of the first bundle; and

determining whether to perform the acts of calculating the representative dipole moment and calculating the mutual inductance based at least in part on the evaluation.

11. The method of claim 1, further comprising:

evaluating whether a dipole-moment direction of the first bundle is substantially the same as a dipole-moment direction of the second bundle and whether the angle between a perpendicular line to this direction and the line joining the centers of mass of the two bundles is substantially equal to a fixed amount; and

determining whether to perform the acts of calculating the mutual inductance based at least in part on the evaluation.

12. The method of claim 11, wherein the fixed amount is between 35°

and 45°

.

13. The method of claim 1, further comprising:

evaluating whether the dipole moment of the first bundle is substantially perpendicular to a dipole moment of the second bundle and whether the relative position of the first bundle to the second bundle is such that a center of the second bundle is located substantially on an axis extending through the dipole moment of the first bundle; and

determining whether to perform the act of calculating the mutual inductance based at least in part on the evaluation.

14. One or more computer-readable media comprising computer-executable instructions for causing a computer system to perform the method of claim 1.

15. One or more computer-readable media comprising design information for an integrated circuit having a layout modified at least in part by the method of claim 1.

16. A method for determining inductance in an integrated circuit layout, comprising:

representing magnetic fields created by current loops between a signal-wire segment and one or more associated return-path segments as a single magnetic field generated by a representative dipole moment;

determining a magnetic flux of the single magnetic field through a surface spanned between a distant signal-wire segment and an associated distant return-path segment;

calculating a mutual inductance between the current loops associated with the signal-wire segment and a current loop associated with the return-path segment, the mutual inductance being based at least in part on the magnetic flux determined; and

outputting the mutual inductance.

17. The method of claim 16, wherein the representative dipole moment comprises a weighted average of dipole moments resulting from the current loops.

18. The method of claim 16, wherein the associated return-path segments of the first bundle are identified as being return paths for the signal-wire segment based at least in part on their resistance and separation relative to the signal-wire segment.

19. The method of claim 16, further comprising evaluating a distance between the first bundle and the second bundle and performing the method of claim 16 only if the distance is greater than a predetermined distance.

20. The method of claim 19, wherein the predetermined distance is 20 nm.

21. One or more computer-readable media comprising computer-executable instructions for causing a computer system to perform the method of claim 16.

22. One or more computer-readable media comprising design information for an integrated circuit having a layout modified at least in part by the method of claim 16.

23. A method for analyzing inductance in an integrated circuit layout, comprising:

in an electronic design automation (EDA) software environment,

fracturing signal-wire segments and ground-wire segments of the integrated circuit layout into at least a first bundle and a second bundle, the first bundle and the second bundle each comprising a respective signal-wire segment and one or more corresponding ground-wire segments parallel to and of a same length as the respective signal-wire segment;

evaluating a distance between the first bundle and the second bundle;

calculating the mutual inductance between the first bundle and the second bundle using a first inductance computation technique if the distance between the first bundle and the second bundle is less than a threshold distance; and

calculating the mutual inductance between the first bundle and the second bundle using a second inductance computation technique if the distance is more than the threshold distance,

wherein the first inductance computation technique calculates inductance with higher precision but less computational efficiency than the second inductance computation technique for bundles separated by less than the threshold distance.

24. The method of claim 23, wherein the second inductance computation technique comprises representing the magnetic fields created between the signal-wire segment and each corresponding ground-wire segment of the first bundle as a single magnetic field created by a magnetic dipole.

25. The method of claim 24, wherein a dipole moment of the magnetic dipole comprises a weighted average of dipole moments resulting from individual current loops in the first bundle, each individual current loop comprising the signal-wire segment of the first bundle and a respective one of the corresponding ground-wire segments of the first bundle.

26. The method of claim 23, wherein the threshold distance is 20 micrometers.

27. The method of claim 23, wherein the first inductance computation technique uses a partial-inductance approach.

28. The method of claim 23, further comprising calculating the mutual inductance between the first bundle and the second bundle using the first inductance computation technique in response to a user setting.

29. The method of claim 23, further comprising:

evaluating whether a configuration of the corresponding ground-wire segments of the first bundle is symmetrical with respect to the signal-wire segment of the first bundle; and

determining whether to perform the mutual inductance calculations based at least in part on the evaluation.

30. The method of claim 23, further comprising:

evaluating whether a dipole-moment direction of the first bundle is substantially the same as a dipole-moment direction of the second bundle and whether the angle between a perpendicular line to this direction and the line joining the centers of mass of the two bundles is substantially equal to a fixed amount; and

determining whether to perform the mutual inductance calculations based at least in part on the evaluation.

31. The method of claim 23, wherein the fixed amount is between 35°

and 45°

.

32. The method of claim 23, further comprising:

evaluating whether a dipole moment of the first bundle is substantially perpendicular to a dipole moment of the second bundle and whether the relative position of the first bundle to the second bundle is such that a center of the second bundle is located substantially on an axis extending through the dipole moment of the first bundle; and

determining whether to perform the mutual inductance calculations based at least in part on the evaluation.

33. One or more computer-readable media comprising computer-executable instructions for causing a computer system to perform the method of claim 23.

34. One or more computer-readable media comprising design information for an integrated circuit having a layout modified at least in part by the method of claim 23.

35. A method for analyzing mutual inductance in a circuit, comprising:

receiving a description of the circuit, the description being indicative of at least a first inductor and a second inductor in the circuit;

representing magnetic fields created by respective turns of the first inductor as a single magnetic field generated by a representative dipole moment;

determining a magnetic flux of the single magnetic field through surfaces spanned between respective turns of the second inductor; and

calculating a mutual inductance between the first inductor and the second inductor based at least in part on the magnetic flux determined.

36. The method of claim 35, wherein the act of representing comprises:

partitioning the first inductor into one or more straight segments;

grouping one or more turns of the first inductor into bundles, the bundles comprising parallel and opposite ones of the straight segments; and

computing individual dipole moments for at least some of the respective bundles.

37. The method of claim 36, wherein each turn of the first inductor is grouped into bundles, wherein individual dipole moments are computed for each bundle, and wherein the representative dipole moment of the first inductor comprises the sum of the individual dipole moments.

38. The method of claim 36, wherein the partitioning further includes forming concentric closed rings from at least a portion of the straight segments, the concentric closed rings representing the turns of the first inductor.

39. The method of claim 35, wherein the representative dipole moment is located at the center of mass of the first inductor.

40. The method of claim 35, wherein the single magnetic field is a first magnetic field, the representative dipole moment is a first representative dipole moment, the magnetic flux is a first magnetic flux, and the mutual inductance is a first mutual inductance, the method further comprising:

representing magnetic fields created by respective turns of the second inductor as a second magnetic field generated by a second representative dipole moment;

determining a second magnetic flux of the second magnetic field through surfaces spanned between respective turns of the first inductor;

calculating a second mutual inductance between the first inductor and the second inductor based at least in part on the second magnetic flux determined; and

averaging the first inductance and the second inductance.

41. The method of claim 35, wherein the first inductor is dissimilar from the second inductor.

42. The method of claim 35, further comprising determining a noise effect between the first inductor and the second inductor based at least in part on the calculated mutual inductance.

43. The method of claim 35, wherein the first inductor is a rectangular inductor.

44. The method of claim 35, wherein the first inductor is a non-Manhattan multi-turn polygon inductor.

45. One or more computer-readable media comprising computer-executable instructions for causing a computer system to perform the method of claim 35.

46. One or more computer-readable media comprising design information for an integrated circuit having a layout modified at least in part by the method of claim 35.