Lock in thermal laser stimulation through one side of the device while acquiring lock-in thermal emission images on the opposite side

摘要

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.

主权项

1. 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.