Failure analysis gains electrical, microscopy tools

Makers of failure-analysis tools targeted Semicon West to highlight both electrical and microscopy techniques that can help isolate faults in integrated circuits. Tools brought to the forefront included probing systems as well as a new approach to microscopy that can offer millionfold magnification.

The microscopy approach comes from ALIS, whose name stands for atomic level imaging system. Although not exhibiting, company officials were on hand to describe the ALIS technique. Bill Ward, ALIS president, explained that, in contrast to traditional scanning electron microscopes, the ALIS tool uses helium ions as the imaging particles. "Since ions can be focused into a smaller probe size and have less sample interaction, we can generate higher resolution images with more contrast so more detail can be seen," he said. Initially, he said, the company will focus on a tool for semiconductor failure-analysis engineers.

Looking at failures is one way to analyze them. You might also want to measure their electrical parameters with an instrument such as Keithley's 4200 semiconductor characterization system. Of course, the one failed transistor out of millions is unlikely to come equipped with convenient 50-micron probe pads, so you'll need a way to probe that transistor. That, said Keithley product manager Dave Rubin, is possible because of work Keithley has done with Zyvex, a company that shared exhibit space with Keithley at Semicon. According to Zyvex staff scientist Richard Stallcup, Zyvex's S100 offers 5-nm movement precision, probe-tip diameters of less than 20 nm, and current-measuring capabilities down to 1 pA (Ref. 1)—sufficient for making measurements on individual transistors fabricated in 65-nm processes.

Yet another approach to transistor measurements is to forego physical contact altogether. To that end, Suss MicroTec exhibited a noncontact probe system that acquires signals without loading the circuit under test. The system employs an integral atomic-force probe in combination with a prober such as the Suss PM8 to enable scanning and positioning. A tip positioned above an area of interest is stimulated with electrical pulses, while a laser monitors the probe deflection that results from the forces generated between an electrical signal from the DUT and the charged tip. From the measured deflection, system software extracts the DUT signal-voltage waveform. "It's as easy to use as an oscilloscope," said Dan Ouellette, noncontact probing manager at Suss, and having test-driven the system, I'd have to concur.