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

• US 20060031036A1
• Filed: 09/30/2005
• Published: 02/09/2006
• 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
• Granted Patent: US 7,478,345 B2
• Time in Patent Office: Days
• US Class Current: 702/117
• 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, the method comprising:

applying the electrical signal to a signal analysis circuit disposed within the integrated circuit;

wherein the signal analysis circuit changes its condition based on the applied electrical signal;

detecting the change of the condition of the signal analysis circuit; and

determining the characteristics of the electrical signal inside the integrated circuit based on the detected change of the condition of the signal analysis circuit.

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

3. The method of claim 1, wherein the detecting of the change of the condition of the signal analysis circuit comprises registering photon emission produced by the signal analysis circuit.

4. The method of claim 3, wherein the detecting further comprises recording an arrival time of the registered photon emissions.

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

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

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

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

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

(2) adjusting the applied reference voltage level; and

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

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

9. The method of claim 7, wherein the 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 the integrated circuit to increment the digital counter.

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

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

13. The method of claim 11, wherein the 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 the integrated circuit.

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

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

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

a signal analysis circuit disposed within the integrated circuit;

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

a detector for detecting the change in the condition of the signal analysis circuit;

wherein the characteristics of the electrical signal inside the integrated circuit are determined based on the detected condition change.

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

19. The apparatus of claim 17, further comprising a photon emission detector for registering photon emissions produced by the signal analysis circuit.

20. The apparatus of claim 19, further comprising a timing circuitry for recording an arrival time of the registered photon emissions.

21. The apparatus of claim 17, wherein the 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 the comparator;

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

23. The apparatus of claim 22, further comprising:

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

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

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

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

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

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

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

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

29. The apparatus of claim 27, wherein the 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 the integrated circuit.

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

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

33. An integrated circuit comprising a signal analysis circuit disposed within the integrated circuit, the signal analysis circuit changing its condition based on an electrical signal applied to the signal analysis circuit;

wherein the signal analysis circuit comprises a photon emitting structure for transmitting information on the change of the condition of the signal analysis circuit to an external measuring equipment.

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

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

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

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

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

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