The focused ion beam (FIP) is a powerful tool in the hands of a skilled electronics failure analysis engineer. In this post, we use the metaphor of a surgeon wielding a scalpel to help explain the power and versatility of the FIB system.
Imagine, if you will, a futuristic surgery theater. A surgeon sits before a sprawling bank of monitors showing images of a patient that has been magnified to sizes tens or hundreds of thousands of times larger than they would appear to her naked eye.
She rests her fingers delicately on a panel of knobs, sliders, and joysticks, carefully adjusting each input to calibrate her instruments. A few moments of fine-tuning and the target of her procedure crystallizes into focus: a microscopic defect that, despite its size, seriously threatens the patient’s life.
She quickly drafts a surgical plan on the image; instead of forceps or a scalpel, she brings a tightly focused particle beam to bear, making infinitesimally small, precisely placed incisions isolating the anomalous target from its surroundings. A quick twiddle of the controls and the energy beam becomes a tool for reconstruction instead of excision. The surgeon deftly reroutes the affected parts of the patient’s anatomy to circumvent the faulty material, ensuring a full recovery.
What may seem to be a scene ripped from the annals of schlocky science fiction movie may ring truer than one might expect, given one key disclosure: our patient is not a living being, but is rather an integrated circuit, wrought in silicon and metal. Our surgeon’s tool was a focused ion beam (FIB) system; the procedure she executed was not a heart bypass or tumor biopsy, but an example of FIB isolation and editing, one of many electronics failure analysis services offered by Spirit.
The focused ion beam is an extremely versatile electronics failure analysis tool, one which greatly broadens the variety of electronics failure analysis services that can be performed.
The FIB is very similar to an electron microscope, in that it uses a beam of charged particles instead of focused light to create images of nanoscopically small objects. The FIB differs, however, in that this beam can also be used to remove integrated circuit (IC) material or to catalyze chemical reactions (for example, the disassociation of atoms of metal from a carrier molecule, and the subsequent adsorption of these atoms onto the surface of a microchip).
These properties allow the FIB to be used to cut and rewire an integrated circuit, just as our hypothetical surgeon did. Such operations will generally take place during the early debug phases of a product, to identify and eliminate errors in a design. The FIB may also be used during failure analysis to confirm the root cause of failure. For example, if an open circuit is identified as the root cause of a given malfunction, an analyst may reconnect the circuit at the site of the open and retest the sample, showing that once the open is remedied the part begins functioning normally.
The FIB is also a powerful tool for IC and PCB failure analysis in that it can be used to great effect in isolating a failure. The nature of the ion beam is such that charge contrast effects are generally far stronger than those seen in the electron microscope, which is a boon when searching for open circuits.
The FIB’s ability to cut traces is also invaluable for isolating potentially failing nodes on a die, with FIB probe pads created with the tool’s metal patterning capability providing an easy way to test the newly isolated features.
Sample preparation for inspection in other tools is also one of the many failure analysis services that can be performed with the FIB. Rather than performing mechanical cross-sections which can be time-consuming and risky when dealing with small defects, the FIB can be used to perform precisely targeted sections for analysis.
In many cases, FIB cross-sectioning can successfully prepare samples from materials that would be exceedingly difficult to accomplish with a traditional mechanical cross-section. For example, certain types of soft or flexible materials used in modern PCBs can prove problematic for traditional sectioning but are easily prepped in the FIB.
Creating thin lamellae for transmission electron microscopy is also greatly simplified by the use of FIB (though it is still by no means trivial, requiring several hours of time for a single sample). Seeing that the sample has reached the proper thickness for TEM work is much more direct in the FIB than with some mechanical preparation techniques.
Though the FIB’s capabilities (and perhaps even its name) sound as though they have been lifted from a failed script for a futuristic TV show, the focused ion beam allows electronic failure analysis labs like Spirit to greatly increase the electronics failure analysis services they can offer. The value of the FIB in performing isolation, editing, and sample preparation make it an invaluable tool, facilitating failure analysis of even the most cutting edge of technologies.