ALBUQUERQUE, N.M. — An optical beam failure analysis technique that detects integrated circuit defects from both the front and back of the device has been developed at Sandia National Laboratories. The TIVA (thermally-induced voltage alteration)/SEI (Seebeck Effect Imaging) technique finds failures in an integrated circuit quickly — as fast or faster than any of its predecessors.
The beam from an infrared laser, operating at wavelengths for which silicon is transparent, is focused on the device, heating only a small part of the integrated circuit at a time. The localized heating produces a voltage change on the integrated circuit which is biased with a constant current source.
An image of the circuit’s response is generated by rastering the laser spot over the circuit with a laser-scanning microscope while recording changes in the power requirements. The laser-scanning optics also generate a reflected light image, which when registered with the TIVA image, allows for rapid localization of the failure in the circuit.
Faults and failures within the circuit react differently to the heat stimulation than operational components. In an unflawed device, the effects produced by the heat don’t change the circuit’s operation. However, if the power demands of the chip change due to the local heating, it is an indication of flaws. The SEI mode detects if a conductor is open, while TIVA locates a short circuit.
“TIVA is extremely sensitive and allows us to see flaws we either couldn’t detect before or could locate only with significant time and effort,” says Sandia developer Ed Cole.
One of the significant aspects of TIVA is that it allows for scanning of the integrated circuit from both the front and back.
“This is important because state-of-the-art chips employ up to seven layers of metal interconnections, preventing direct observation of deeper structures from the front of the device,” Cole says. “Additionally, flip-chip or upside down packaging denies direct access to the front surface. TIVA gives the ability to evaluate the integrated circuit from both sides.”
TIVA operates similarly to its older cousins CIVA (charge-induced voltage alteration) and LIVA (light-induced voltage alteration), co-invented by Cole in the mid-1990s. CIVA was the first “induced voltage alteration” failure analysis technique developed at Sandia. It localized open conductors using a scanned electron beam. LIVA uses photocurrents produced with relatively short wavelength light, instead of heat as in TIVA.
TIVA has recently been successfully applied beyond the world of integrated circuits in diagnosing various failures in MEMS (microelectromechanical systems) devices.
OptoMetrix license
Sandia has granted OptoMetrix, Inc., an optical instrumentation company specializing in failure analysis techniques for integrated circuits, a license to use LIVA and TIVA/SEI technologies.
The license allows the Seattle company to market equipment using the technologies. The equipment could then be sold to integrated circuit manufacturers for failure detection.
While a few semiconductor manufacturers have directly licensed these technologies in the past, this agreement is the first time an equipment manufacturer has licensed them for sale.
Technical contact:
Ed Cole, coleei@sandia.gov@sandia.gov, (505) 844-1421