Noninvasive optical method for measuring internal switching and other dynamic parameters of CMOS circuits

• US 5,940,545 A
• Filed: 07/18/1996
• Issued: 08/17/1999
• Est. Priority Date: 07/18/1996
• Status: Expired due to Term

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Tsang, James Chen-Hsiang, Kash, Jeffrey Alan
• Primary Examiner(s): Couso, Jose L.
• Application Number:
  US08/683,837
• Time in Patent Office: 1,125 Days
• Field of Search: 324/501, 324/522, 324/719, 324/724, 324/158 R, 324/751, 382/141, 382/149, 382/312, 250/311, 250/307, 250/214 VT, 250/363 S, 250/461.1, 356/311, 356/237, 356/338, 348/92, 348/79, 348/87, 348/126, 348/216, 348/217, 348/241, 348/297
• US Class Current: 382/312
• CPC Class Codes: G01R 31/311 of integrated circuits G01R31/31728 takes precedence

Abstract

Intrinsic, transient optical emission from a CMOS integrated circuit is used to determine the internal switching of such a circuit including the temporal evolution of its logic states. By joining an appropriate optical microscope to a suitable, photon counting, multichannel optical detector which is capable of time resolution better than 100 psec, and a spatial resolution of better than 60 microns, full temporal information, including the relative phases of switching events, can be obtained from many devices in a circuit simultaneously. The time and spatial resolution are suitable for analyzing timing problems in present and future sub-micron-scale CMOS integrated circuits with switching speeds up to at least 10 GHz. The invention comprises a combination of an optical microscope and a detector capable of providing optical waveforms and/or spatial images of the light emitted during electrical switching by the individual devices which comprise an integrated circuit. The microscope and detector are combined such that an image of all or a portion of an integrated circuit under test is provided by the microscope to the detector. The spatial and temporal information from the detector is used to determine switching times and other dynamic information about the devices in the circuit.

Claims

1. A method for measuring the internal timing of integrated circuits comprising:

a. obtaining periodic optical emissions from an integrated circuit operating with time-varying internal currents, and

b. time resolving said emissions by photon timing to provide information about said integrated circuit.

2. The method of claim 1 wherein said information is in the form of a series of optical images each comprising a discrete time interval.

3. The method of claim 1 wherein said information is in the form of one or more optical waveforms.

4. The method of claim 2 wherein the optical sampling is up-conversion.

5. The method of claim 1 wherein said emissions are measured from the front side of said integrated circuit.

6. The method of claim 1 wherein said emissions are measured from the back side of said integrated circuit.

7. The method of claim 2 wherein said image is compared to an image of the same circuit taken under different external stimuli.

8. A device for measuring the internal timing of integrated circuits comprising:

a. means for obtaining periodic emissions from an integrated circuit operating with time varying internal currents, and

b. means for time resolving said emissions by photon timing to provide information about said integrated circuit.

9. The device of claim 8 wherein said means for obtaining include a photon-counting photomultiplier tube.

10. The device of claim 8 wherein said means for obtaining include an avalanche photodiode detector.

11. The device of claim 8 wherein said means for obtaining include an imaging microchannelplate photomultiplier.

12. The device of claim 8 wherein said means for analyzing include a time-to-amplitude converter and a multichannel analyzer.

13. The device of claim 8 wherein said means for analyzing include a time-to-amplitude converter and a 3-axis multichannel analyzer.

14. An optical method for determining the electrical state of an integrated circuit, and the temporal evolution of said electrical state for a circuit undergoing switching transitions, the method comprising:

a. obtaining one or more optical waveforms corresponding to optical emissions generated by time varying internal currents in the integrated circuit, and

b. analyzing said one or more optical waveforms to identify and characterize the electrical waveforms associated with said currents.

15. The method of claim 14 wherein said optical waveforms are in the form of a series of optical images each comprising a discrete time interval.

16. The method of claim 14 wherein said obtaining step further comprises the step of obtaining the optical waveform by photon timing.

17. The method of claim 14 wherein said obtaining step is performed using a streak camera.

18. The method of claim 14 wherein said emissions are measured from the front side of said integrated circuit.

19. The method of claim 14 wherein said emissions are measured from the back side of said integrated circuit.

20. A device for determining the electrical state of an integrated circuit, and the temporal evolution of said electrical state for a circuit undergoing switching transitions, the device comprising:

a. means for obtaining one or more optical waveforms corresponding to optical emissions generated by time varying internal currents in the integrated circuit, and

b. means for analyzing said one or more optical waveforms to identify and characterize the electrical waveforms associated with said currents.

21. The device of claim 20 wherein said means for obtaining include a photon-counting photomultipler tube.

22. The device of claim 20 wherein said means for obtaining include an avalanche photodiode detector.

23. The device of claim 20 wherein said means for obtaining include an imaging microchannelplate photomultipler.

24. The device of claim 20 wherein said means for analyzing include a time-to-amplitude converter and a multichannel analyzer.

25. The device of claim 20 wherein said means for analyzing include a time-to-amplitude converter and a 3-axis multichannel analyzer.

26. An optical method for determining the logic state of a CMOS integrated circuit, and the temporal evolution of said logic state for a circuit undergoing switching transitions during normal operation comprising,

a. obtaining optical pulses generated by switching transitions in a CMOS integrated circuit,

b. analyzing the optical pulses to identify 0-1 and 1-0 transitions,

c. assigning 1-0 and 0-1 transitions at the outputs of individual gates of the circuit.

27. A method according to claim 26, further comprising the steps of:

mapping evolution of logic states in a CMOS circuit as a function of time.

28. A device for determining a logic state of a CMOS integrated circuit at an instant of time as the circuit undergoes information processing comprising:

a. a means for measuring the individual optical pulses generated by discrete switching transitions in said circuit,

b. a means for analyzing the relative intensities of the switching induced optical pulses observed from the individual gates of said circuits to determine the initial and final states of each switching transition,

c. a means for assigning the 1-0 and 0-1 transitions at the outputs of individual gates of the said circuit.

29. A device according to claim 28, further including means to map the temporal evolution of logic states in a CMOS circuit.

30. A method for measuring the number of switching events occurring in any interval of time and any area of the circuit in CMOS integrated circuits comprising:

a. obtaining optical emission pulses coincident with switching transitions from a CMOS integrated circuit and

b. analyzing said emission to obtain a spatial and temporal density of switching activity in the said integrated circuit.

31. A device for measuring the number of switching events occurring in any interval of time and any area of the circuit in CMOS integrated circuits comprising:

a. means for measuring the optical emission pulses coincident with switching transitions from a CMOS integrated circuit,

b. a means for determining a number of switching induced optical pulses per unit area and time interval, and displaying said densities.