In-situ packaging decapsulation feature for electrical fault localization
An IR camera is used to image an IC to identify hot spots. The objective of the IR camera is removed and laser optics are inserted into the optical axis of the system. A laser is then used to ablate the encapsulation in a defined area around the optical axis. The IR camera operates in a lock-in mode to obtain phase information of the IR signal from the IC. The phase information is used to obtain a depth estimate of the defect. Predetermined etch rates are then used in conjunction with the depth estimate to generate a timed end-point for the laser ablation.
1. A system for testing and decapsulating IC, comprising:
a sample stage for supporting the IC;
a thermal camera configured to detect location of hot spot caused by potential defect in the IC;
a laser source of wavelength 400 nm to 900 nm;
a first optics arrangement configured to enable the thermal camera to image the IC, the image being indicative of a location of a hot spot in the IC;
a second optical arrangement configured to focus a laser beam from the laser source onto the IC;
a scanner configured to generate a scanning motion between the laser beam and the IC so as to ablate a selected area of the IC.
2. The system of claim 1 , wherein the laser source is a pulsed laser source.
3. The system of claim 1 , further comprising an optical turret upon which the first and the second optical arrangements are affixed.
4. The system of claim 1 , further comprising a hood fluidly connected to a pump and configured to pump sputtered encapsulation material.
5. The system of claim 1 , further comprising a nozzle configured for injecting a gas jet onto the IC.
6. The system of claim 1 , further comprising optics stage and wherein the first and second optical arrangements are coupled to the optics stage.
7. The system of claim 6 , wherein the optics stage comprises a z-stage.
8. The system of claim 1 , further comprising a visible light objective and a visible light camera.
9. The system of claim 8 , further comprising a selecting optical element to deflect collected light to the thermal camera or the visible light camera.
10. The system of claim 9 , wherein the selecting optical element comprises a reflex mirror.
11. The system of claim 1 , further comprising a controller receiving signals from the IR camera and programmed to provide depth estimate of the defect using the signals from the IR camera.
12. The system of claim 11 , wherein the controller is further programmed to generate a timed end-point for the laser using the depth estimate.
13. The system of claim 12 , further comprising a look-up table stored in the controller, the look-up table correlating etch rate for various materials.
14. A method for identifying defects in an IC, comprising:
placing an IC on a sample stage;
applying a test signal to the IC;
using a first set of optics to collect IR radiation from the IC;
using an IR camera to image the IR radiation and generate a thermal image of the IC;
using the thermal image to delineate an area of the IC to be decapsulated;
while the IC remains on the sample stage, using a second set of optics to focus a laser beam onto the area delineated and removing encapsulation material from the delineated area only.
15. The method of claim 14 , further comprising using a visible light objective to image the delineated area after removal of the encapsulation material.
16. The method of claim 14 , wherein the test signal comprises an electrical test signal.
17. The method of claim 14 , wherein the test signal comprises a thermal test signal.
18. The method of claim 14 , further comprising activating the sample stage so as to spatially move the sample, thereby scanning the laser beam over the delineated area.
19. The method of claim 14 , wherein the test signal comprises an illumination beam.
20. The method of claim 14 , further comprising generate a second thermal image of the IC after the completion of the removing encapsulation material.
21. The method of claim 14 , wherein removing encapsulation material is performed according to preset length of time.
22. The method of claim 21 , wherein the preset length of time is calculated by the steps:
determining etch rates of the laser for different materials;
using the IR radiation to generate depth estimate of the defect;
using the depth estimate and a selected etch rate to generate the preset length of time.
23. The method of claim 22 , wherein using the IR radiation to generate depth estimate comprises using a lock-in imaging to determine a phase of the IR signal and correlating the phase to heat propagation rate within the IC material to thereby generate the depth estimate.