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 method for probing an integrated circuit (IC), comprising:
stimulating said IC with a test signal;
illuminating a selected area of said IC with a laser beam;
collecting beam reflection from said IC;
converting said beam reflection to an electrical probing signal;
separating the electrical probing signal into a DC component and an AC component;
selecting a frequency or a band of frequencies of said AC component;
calculating at least one of a total amplitude, a total intensity, polarization rotation, and a phase of said probing signal at the selected frequency or band of frequencies;
generating a spatial map of one of said total amplitude, total intensity, polarization rotation, and phase, for various locations over a selected area of said IC; and
displaying the spatial map on a monitor.
2. The method of claim 1 , further comprising generating an optical image of said selected area of the IC from the DC component.
3. The method of claim 1 , further comprising normalizing the spatial map using the DC component.
4. The method of claim 1 , wherein:
collecting beam reflection comprises separating the beam into a vertically polarized component and horizontally polarized component; and,
converting said beam comprises using a first photodetector to convert the vertically polarized component to generate vertically polarized part of said AC component and using a second photodetector to convert the horizontally polarized component to generate horizontally polarized part of said AC component.
5. The method of claim 4 , further comprising mutually dividing or substracting the vertically polarized part of said AC component and the horizontally polarized part of said AC component.
6. The method of claim 5 , further comprising positively biasing one of the first or second photodetector while negatively biasing the other of the first or second photodetector.
7. The method of claim 4 , further comprising:
using the signal from the first photodetector to generate a spatial map of one of said total amplitude, total intensity, polarization rotation, and phase; and
using the signal from the second photodetector to generate a spatial map of a different one of said total amplitude, total intensity, polarization rotation, and phase.
8. The method of claim 1 , further comprising demodulating the in-phase and quadrature components of the AC component.
9. A method for probing an integrated circuit (IC), comprising:
stimulating said IC with a test signal;
illuminating a selected area of said IC with a laser beam;
collecting beam reflection from said IC;
converting said beam reflection to an electrical probing signal;
extracting an RF component from the electrical probing signal;
demodulating the in-phase and quadrature components of the RF component;
selecting a frequency or a band of frequencies of said RF component;
calculating RF power the selected frequency or band of frequencies;
displaying the RF power for a fixed position on the DUT or for a selected area of the DUT.
10. The method of claim 9 , further comprising power filtering the RF component.
11. The method of claim 10 , further comprising extracting a DC component from the electrical probing signal and using the DC component to generate an optical image of the DUT.
12. The method of claim 10 , further comprising extracting a DC component from the electrical probing signal and using the DC component to normalize the RF power.
13. A method for probing an integrated circuit (IC), comprising:
stimulating said IC with a plurality of test signals;
for each test signal of the plurality of test signals:
illuminating a selected area of said IC with a laser beam;
collecting beam reflection from said IC;
converting said beam reflection to an electrical probing signal;
extracting an AC component from the electrical probing signal;
selecting a frequency or a band of frequencies of said AC component;
calculating at least one of a total amplitude, a total intensity, polarization rotation, and a phase of said probing signal at the selected frequency or band of frequencies;
generating a spatial map of one of said total amplitude, total intensity, polarization rotation, and phase, for various locations over a selected area of said IC;
displaying on a monitor a plot of the spatial maps generated for all of the test signals.
14. The method of claim 13 , further comprising generating a cross-section of the plot.
15. The method of claim 13 , further comprising providing a reference signal and wherein said calculating comprises multiplying said probing signal with the reference signal to thereby provide a product signal, and integrating said product signal.
16. The method of claim 15 , wherein said reference signal is of frequency similar to that of said probing signal, but is shifted in phase.
17. The method of claim 13 , further comprising obtaining a sync signal and illuminating a selected area of said IC with a laser beam according to the sync signal.
18. The method of claim 13 , wherein illuminating a selected area of said IC with a laser beam further comprises splitting the laser beam into a vertically polarized component and a horizontally polarized component prior to the beam reaching the IC.
19. The method of claim 18 , wherein converting said beam comprises using a first photodetector to convert the vertically polarized component to generate vertically polarized part of said AC component and using a second photodetector to convert the horizontally polarized component to generate horizontally polarized part of said AC component.