Apparatus and method for measuring characteristics of dynamic electrical signals in integrated circuits

• US 6,976,234 B2
• Filed: 01/13/2003
• Issued: 12/13/2005
• Est. Priority Date: 01/13/2003
• Status: Active Grant

• Current Assignee: DCG Systems Incorporated (Thermo Fisher Scientific Incorporated)
• Original Assignee: Credence Systems Corporation (COHU Incorporated)
• Inventors: Kasapi, Steven
• Primary Examiner(s): Do, Thuan
• Application Number:
  US10/341,721
• Publication Number:
  US 20040139406A1
• Time in Patent Office: 1,065 Days
• Field of Search: 716/1, 716/6, 716/19, 716/4, 716/5, 374/17, 250/574, 600/346
• US Class Current: 324/501
• CPC Class Codes: G01R 31/31903 tester configuration
• CPC Class Codes: G01R 31/31937 Timing aspects, e.g. measuring propagation delay G01R31/3191 and G01R31/31922 take precedence; marginal testing G06F11/24

Abstract

Systems and methods consistent with principles of the present invention allow contactless measurements of voltage characteristics of dynamic electrical signals in integrated circuits. The invention utilizes a signal analysis circuit, such as a voltage comparator, disposed with the circuit under test, which is optically coupled with the external timing measurement equipment. The signal analysis circuit changes its state depending on the characteristics of the measured electrical signal applied thereto. The changes in the condition of the signal analysis circuit are sensed by the external timing measurement equipment provided outside the circuit under test. To this end, the signal analysis circuit is optically coupled with the external measurement equipment registering specific changes in the condition of the signal analysis circuit. The information on the condition of the signal analysis circuit registered by the external measurement equipment is used to study the characteristics of the dynamic electrical signals within the circuit.

Claims

1. A method for measuring characteristics of an electrical signal inside of an integrated circuit, said method comprising:

disposing a signal analysis circuit within said integrated circuit;

wherein said electrical signal inside said integrated circuit causes a change in a condition of said signal analysis circuit;

detecting said condition of said signal analysis circuit in a wireless manner; and

determining said characteristics of said electrical signal inside said integrated circuit based on said detected condition, wherein said detecting of said condition of said signal analysis circuit comprises recording an arrival time of photon emissions produced by said signal analysis circuit.

2. The method of claim 1, wherein said condition of said signal analysis circuit is additionally determined by a reference voltage applied to said signal analysis circuit.

3. The apparatus of claim 1, wherein said electrical signal is a noise signal.

4. The apparatus of claim 1, wherein said electrical signal is a frequency signal.

5. The method of claim 1, wherein said electrical signal is a voltage signal and said signal analysis circuit comprises a comparator.

6. The method of claim 5, wherein a reference voltage level is applied to said comparator;

said comparator changing its state when said electrical signal reached said reference voltage level.

7. The method of claim 6, wherein said detecting further comprises:

(1) recording an arrival time of photons emissions produced by said comparator;

(2) adjusting said applied reference voltage level; and

(3) repeating (1) and (2) for at least two test cycles of said integrated circuit.

8. The method of claim 7, further comprising using said recorded photon arrival times and corresponding values of said applied reference voltage to reconstruct said characteristics of said electrical signal.

9. The method of claim 7, wherein said reference voltage level is produced by a digital-to-analog converter coupled to a digital counter.

10. The method of claim 9, further comprising using a test cycle of said integrated circuit to increment said digital counter.

11. The method of claim 1, wherein said signal analysis circuit comprises at least one photon emitting structure.

12. The method of claim 11, wherein said at least one photon emitting structure comprises an optically-exposed saturated nMOS or pMOS transistor.

13. The method of claim 11, wherein said at least one photon emitting structure comprises an optically-exposed CMOS device.

14. The method of claim 1, further comprising injecting a test signal into said integrated circuit.

15. The method of claim 1, wherein said detecting of said condition of said signal analysis circuit is performed through a front surface of said integrated circuit.

16. The method of claim 1, wherein said detecting of said condition of said signal analysis circuit is performed through a back surface of said integrated circuit.

17. An apparatus for measuring characteristics of an electrical signal inside of an integrated circuit, said apparatus comprising:

a signal analysis circuit disposed within said integrated circuit;

wherein said electrical signal inside said integrated circuit causes a change in a condition of said signal analysis circuit; and

a detector for detecting said condition of said signal analysis circuit in a wireless manner;

wherein said characteristics of said electrical signal inside said integrated circuit are determined based on said detected condition, and wherein said detector records an arrival time of photon emissions produced by said signal analysis circuit.

18. The apparatus of claim 17, wherein said condition of said signal analysis circuit is additionally determined by a reference voltage applied to said signal analysis circuit.

19. The apparatus of claim 17, wherein said electrical signal is a noise signal.

20. The apparatus of claim 17, wherein said electrical signal is a frequency signal.

21. The apparatus of claim 17, wherein said electrical signal is a voltage signal and wherein signal analysis circuit comprises a comparator.

22. The apparatus of claim 21, wherein a reference voltage level is applied to said comparator;

said comparator changing its state when said voltage signal reached said reference voltage level.

23. The apparatus of claim 22, further comprising:

a timing circuitry for recording an arrival time of photons emissions produced by said comparator;

a voltage adjusting device for adjusting said applied reference voltage level; and

a clock signal generator for generating test cycles for said integrated circuit, wherein said timing circuitry records said arrival times and said voltage adjusting device adjusts said applied voltage level for at least two test cycles generated by said clock cycle generator.

24. The apparatus of claim 23, wherein said recorded photon arrival times and corresponding values of said applied reference voltage are used to reconstruct said characteristics of said electrical signal.

25. The apparatus of claim 24, wherein said digital counter is incremented using said clock cycles generated by said clock signal generator.

26. The apparatus of claim 23, wherein said voltage adjusting device comprises a digital-to-analog converter coupled to a digital counter.

27. The apparatus of claim 17, wherein said signal analysis circuit comprises at least one photon emitting structure.

28. The apparatus of claim 27, wherein said at least one photon emitting structure comprises an optically-exposed saturated nMOS or pMOS transistor.

29. The apparatus of claim 27, wherein said at least one photon emitting structure comprises an optically-exposed CMOS device.

30. The apparatus of claim 17, further comprising a device for injecting a test signal into said integrated circuit.

31. The apparatus of claim 17, wherein said detector is disposed in a predetermined relation with respect to said integrated circuit to perform said detecting of said condition through a front surface of said integrated circuit.

32. The apparatus of claim 17, wherein said detector is disposed in a predetermined relation with respect to said integrated circuit to perform said detecting of said condition through a back surface of said integrated circuit.

33. An integrated circuit comprising a signal analysis circuit disposed within said integrated circuit;

said signal analysis circuit changing its condition based on a measured electrical signal applied to said signal analysis circuit;

wherein said signal analysis circuit comprises a photon emitting structure for transmitting information on said condition of said signal analysis circuit to an external measuring equipment, and wherein said external measuring equipment records an arrival time of photon emissions produced by said photon emitting structure.

34. The integrated circuit of claim 33, wherein said condition of said signal analysis circuit is additionally determined by a reference voltage applied to said signal analysis circuit.

35. The integrated circuit of claim 33, wherein said electrical signal is a voltage signal and wherein said signal analysis circuit comprises a comparator.

36. The integrated circuit of claim 35, wherein a reference voltage level is applied to said comparator;

said comparator changing its state when said voltage signal reaches said reference voltage level.

37. The integrated circuit of claim 33, wherein said at least one photon emitting structure comprises an optically-exposed saturated nMOS transistor.

38. The integrated circuit of claim 33, wherein said at least one photon emitting structure comprises an optically-exposed CMOS device.