System and method for modulation mapping
An apparatus for providing modulation mapping is disclosed. The apparatus includes a laser source, a motion mechanism providing relative motion between the laser beam and the DUT, signal collection mechanism, which include a photodetector and appropriate electronics for collecting modulated laser light reflected from the DUT, and a display mechanism for displaying a spatial modulation map which consists of the collected modulated laser light over a selected time period and a selected area of the IC.
1. A laser probing system for testing an integrated circuit microchip having silicon substrate and plurality of semiconductor devices formed therein, comprising:
a microchip holder configured for supporting the microchip and enabling application of test signals to the microchip;
a laser source providing a laser beam;
beam optics configured for receiving said laser beam and, while the test signals are applied to the microchip, focusing said laser beam onto a selected area of the microchip that includes at least one semiconductor device;
a photosensor receiving modulated beam reflected from said selected area after being modulated by the semiconductor device in response to the test signals, and providing a corresponding electrical signal indicative of the semiconductor device's response to the test signals;
collection electronics receiving the electrical signal from said photosensor and providing an output signal;
an analysis system receiving said output signal over a specified period of time and generating modulation mapping corresponding to the selected area of the microchip.
2. The system of claim 1 , wherein the beam optics is configured to focus said laser beam through the silicon substrate of said microchip.
3. The system of claim 1 , wherein said analysis system comprises a spectrum analyzer.
4. The system of claim 3 , wherein said analysis system further comprises an integrator integrating the output of the spectrum analyzer over a specified period of time.
5. The system of claim 1 , wherein said analysis system comprises a lock-in amplifier.
6. The system of claim 5 , further comprising a reference signal generator providing a reference signal, said reference signal having a frequency similar to that of said output signal, and having a different phase from that of said output signal.
7. The system of claim 6 , further comprising a frame grabber.
8. The system of claim 1 , further comprising a digital signal processor.
9. The system of claim 1 , wherein said beam optics further comprises phase to amplitude converter.
10. The system of claim 1 , wherein said semiconductor device comprises a transistor having a gate, and wherein said beam optics further comprises a polarizer configured to polarize said laser beam in alignment with the gate of said transistor.
11. The system of claim 1 , wherein said semiconductor device comprises MOS (metal-oxide-semiconductor) device.
12. The system of claim 1 , further comprising a scanner for scanning the laser beam over a selected area of the microchip.
13. The system of claim 1 , further comprising a display presenting the modulation mapping which corresponds to output signal over a selected time period and a selected area of the microchip.
14. The system of claim 10 , wherein the polarizer is configured to polarize the laser beam such that the polarization is aligned parallel to length direction of the gate.
15. The system of claim 1 , further comprising a video amplifier configured for receiving a DC part of the electrical signal output by the photosensor, and generating signal for a video image.
16. The system of claim 1 , wherein said analysis system is configured to normalize the output signal and use the output signal to generate a normalized modulation mapping.
17. The system of claim 1 , wherein said analysis system comprises a selector, enabling selection of a frequency or a band of frequencies, and the output signal corresponds to a selected frequency or a selected band of frequencies.