Dual-phase interferometry for charge modulation mapping in ICS

Patent metadata

Field	Value
Publication number	US-9983260-B2
Application number	US-201314433732-A
Country	US
Kind code	B2
Filing date	Oct 11, 2013
Priority date	Oct 12, 2012
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

A dual-phase interferometric method and device for charge modulation mapping in integrated circuits provides significant improvement in signal to noise ratio over conventional detection configurations. The method and device can be used for failure analysis and testing of advanced technology IC chips for which high sensitivity in modulation mapping is required.

First claim

The invention claimed is:

1. A method for detecting electrical activity in a substrate, wherein the substrate is an electrically energized IC substrate, the method comprising the steps of:
applying a generated beam of laser radiation to the substrate;
receiving a reflected beam of radiation from said substrate representative of the generated beam of laser radiation applied thereto;
optically processing the reflected beam of radiation to provide two beams of radiation with different phase angles therebetween;
sensing intensities of the two beams of radiation with different phase angles; and
electronically processing intensities of the two beams to provide an indication of the electrical activity of the substrate.

2. The method of claim 1 , wherein said applying step applies linearly polarized infrared CW laser radiation.

3. The method of claim 1 , wherein said applying step applies said generated beam to a two dimensional area of said substrate.

4. The method of claim 3 , wherein said applying step includes scanning the generated beam for application to said substrate.

5. The method of claim 1 , further including the step of electrically energizing the substrate at timing determined by a clock.

6. The method of claim 1 , wherein said applying step applies the generated beam through an aSIL lens.

7. The method of claim 6 , wherein said receiving step includes receiving said reflected beam through said aSIL.

8. The method of claim 1 , wherein the reflected beam includes components representative of effects from the electrical activity of the substrate at a level many orders of magnitude below other components in the reflected beam.

9. The method of claim 1 wherein the phase angles of the two beams of radiation differ by π/2.

10. The method of claim 1 , wherein applying the generated beam of laser radiation to the substrate includes:
splitting a reference beam from the generated beam of laser radiation prior to applying the generated beam to the substrate;
passing the reference beam through one or more of a 45 degree quarter wave plate and a zero degree polarizer;
reflecting the reference beam back through the one of more of the quarter wave plate and polarizer; and
combining the resulting reference beam with the reflected beam of radiation from said substrate.

11. The method of claim 10 , further comprising sensing a portion of said reference beam after having passed through the quarter wave plate and polarizer, and wherein electronically processing the intensities of the two beams includes processing the resulting sensed signal.

12. The method of claim 1 , wherein said sensing step includes sensing DC and RF components in the two beams.

13. The method of claim 1 , wherein said electronically processing step includes providing time resolved and DC components.

14. The method of claim 1 , wherein said electronically processing step includes the step of providing a two dimensional image of the effects of the electrical activity of the substrate.

15. Apparatus for detecting electrical activity in a substrate, wherein the substrate is an electrically energized IC substrate, the apparatus comprising:
a source of polarized radiation;
optics for applying a generated beam of the radiation to the substrate and receiving a reflected beam of radiation therefrom, the reflected beam having a component representative of the electrical activity of the substrate and of background effects;
an optical system responsive to the reflected beam for providing two beams of phase separated radiation representative of the reflected radiation;
means for sensing the two beams to provide respective signals therefrom;
means for processing the sensed beams to provide an indication of the electrical activity of the substrate separate from the background effects.

16. The apparatus of claim 15 , wherein said source of polarized radiation includes a laser.

17. The apparatus of claim 16 , wherein said laser is a linearly polarized infra-red CW laser.

18. The apparatus of claim 15 , wherein said optics includes an aSil.

19. The apparatus of claim 15 , wherein said optics includes a beam splitter arranged to:
split a reference beam from the generated beam;
apply the remaining generated beam to said substrate;
apply the reference beam to said optical system; and
receive the reflected beam from said substrate for application to said optical system.

20. The apparatus of claim 15 , wherein said optical system includes:
reference optics for receiving a portion of the generated beam as a reference beam; and
combining optics for combining the reference beam and the reflected beam for application to said sensing means.

21. The apparatus of claim 20 , wherein said reference optics includes a quarter wave plate and a polarizer.

22. The apparatus of claim 21 , wherein said reference optics includes reflecting means for causing the reference beam to be reflected back through the polarizer and the quarter wave plate to the combining optics.

23. The apparatus of claim 22 , wherein the quarter wave plate is aligned to 45 degrees and the polarizer is aligned to zero degrees.

24. The apparatus of claim 15 , wherein the reflected beam has a first component unresponsive to the effects of the electrical activity of the substrate at an intensity orders of magnitude greater than a second component therefrom that represents the electrical activity and the optical system provides in the reflected beam applied to the sensing system characteristics that distinguish the first and second components.

25. The apparatus of claim 24 , wherein the processing means provides separate signals for the first and second components.

26. The apparatus of claim 15 , further including 2D means for causing the reflected beam to represent a two dimensional area of the substrate.

27. The apparatus of claim 26 , wherein the 2D means includes scanning means.

28. The apparatus of claim 15 , wherein said processing means includes lock in amplifiers and/or balance detectors providing time resolved and DC components from the sensed beams.

29. The apparatus of claim 15 , further including means for displaying said indication of the electrical activity in a two dimensional form.

30. Apparatus for dual-phase interferometric confocal imaging for electrical signal modulation mapping in ICs comprising:
a source of laser radiation;
means for dividing a beam of said radiation into a generated beam directed to an IC and a reference beam, and for receiving a reflected beam from the IC;
means for combining said reflected and reference beams;
means for adjusting phase and polarization in said reflected and reference beams; and
means for detecting the adjusted reflected and reference beams to provide an indication of electrical activity in said IC.

31. Apparatus for dual-phase interferometric confocal imaging for electrical signal modulation mapping in ICs comprising:
means for splitting a reference beam from a generated beam of laser radiation;
means for applying the remaining generated beam to an IC;
means for receiving a reflected beam of laser radiation from said IC having information representative of electrical activity in said IC;
optical processing means responsive to the reflected beam and the reference beam for creating a plurality of beams having dist

Assignees

• Univ Boston
• Us Air Force

Inventors

• Yurt Abdulkadir
• Unlu Selim M
• Goldberg Bennett B
• Ramsay Euan

Classifications

• G01N21/41

  Refractivity; Phase-affecting properties, e.g. optical path length (G01N21/21 takes precedence) · CPC title

• G01N2021/1719

  Carrier modulation in semiconductors · CPC title

• G01N21/1717

  with a modulation of one or more physical properties of the sample during the optical investigation, e.g. electro-reflectance · CPC title

• G01R31/2851

  Testing of integrated circuits [IC] (G01R31/317 takes precedence; testing individual devices G01R31/26; testing printed circuits G01R31/2801) · CPC title

• G01B9/02001

  characterised by controlling or generating intrinsic radiation properties · CPC title