Adjustable split-beam optical probing (ASOP)

摘要

A practical method for greatly enhancing the strength of the modulated signal from laser probing of IC's is described. An IC device under test (DUT) is scanned with two spatially separated laser beams. The output from a single laser source is split into two separate components with each focused on different areas of the DUT. The separation between the beams and their intensity is adjustable to maximize the strength of the modulated return signal. Typically a NIR laser is used with flip-chip IC devices to account for the band-gap (transmission) characteristics of the substrate material. Upon reflection from the DUT, the reflected beams are recombined to interfere with one another. The phase difference of the two beams is adjustable to gain maximum interference. This signal is then processed to obtain the waveforms that correspond to the actions of the active gates and nodes as the chip is electronically cycled through its prescribed test loop. This method significantly improves the signal to noise ratio and reduces the time it takes to acquire a useful voltage waveform.

主权项

1. A system comprising:
a split beam module configured to receive a linearly polarized input beam, wherein the split beam module is configured to rotate a polarization direction of the input beam to produce a polarization adjusted beam, split the input beam into first and second beams having orthogonal polarization, adjust a spatial separation between the input first and second beams, and independently adjust a relative phase difference between input first and second beams to produce phase-adjusted input first and second beams; imaging components optically coupled to the split beam module along an optical path at a location between the split beam module and a target, wherein the imaging components are configured to focus the phase-adjusted input first and second beams onto the target at corresponding spatially separated first and second locations and transmit portions of the phase adjusted input first and second beams reflected from the spatially separated first and second locations back into the split beam module, wherein the split beam module is further configured to recombine at least part of the portions of the phase adjusted input first and second beams reflected from the spatially separated first and second locations into a signal beam.