Lock in thermal laser stimulation through one side of the device while acquiring lock-in thermal emission images on the opposite side
AssigneeDCG Systems, Inc.
InventorsHerve Deslandes, Rudolf Schlangen, Prasad Sabbineni, Antoine Reverdy, Ingrid De Wolf
Life of this patent
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Abstract
Controlled amount of heat is injected into a stacked die using a light beam, and the propagated heat is measuring with LIT camera from the other side of the die. The thermal image obtained can be characterized so that it can be used to calibrate the phase shift from a given stack layer, or can be used to identify defects in the stacked die. The process can be repeated for each die in the stack to generate a reference for future testing. The thermal image can be investigated to detect faults, such as voids in vias, e.g., TSV.
Claims18
A method for testing a device under test (DUT), comprising:
- situating the DUT onto a test bench, the DUT comprising a stack of a plurality of integrated circuits dies;
- illuminating a defined spot inside the DUT by directing a beam of pulsed laser source having wavelength above 1064 nm from one side of the DUT and focusing the beam onto a spot inside a selected one of the dies;
- obtaining a thermal images of the other side of the DUT;
- and,
- analyzing the thermal image to thereby characterize the thermal propagation of heat from the selected die through other dies within the DUT.
A system for analysis of a device under test (DUT), the DUT comprising a plurality of stacked dies, comprising:
- a test bench to support the DUT;
- a lock-in laser light source operating at a lock-in frequency f1 and position to deliver a pulsed laser light beam onto the DUT from one side thereof;
- an objective lens arrangement operable to focus the pulsed laser light beam onto a selected die from the plurality of stacked dies;
- a lock-in thermal imaging system operating at a lock-in frequency f2 and positioned so as to image the other side of DUT;
- and,
- a controller activating said heat source at the lock-in frequency f1 and activating said thermal imaging system at the lock-in frequency f2, and for controlling the objective lens arrangement to successively focus the pulsed laser light beam onto a different dies from the plurality of stacked dies.
Dependencies are inferred from the claim text.