Liquid Crystal Analysis

Liquid Crystal Analysis is a fast technique used for isolating failures when a high amount of current (several hundred microAmps or higher) is drawn by the failing device. The higher current can be caused by a defect on the chip that produces localized heating. Liquid crystal analysis is able to detect localized heating caused by currents as low as 200 uA and as high as hundreds of milliamps. Unlike PEM, the technique is able to localize a failure even if it is shielded by a number of layers of metal.

Liquid Crystal analysis is performed by applying a thin layer of liquid crystal (usually K-18 or K-21) on the surface of a chip. The chip is powered up and the failure is reproduced. Using polarized light and an external heat source, a “hot spot” can often be detected at the site of the failure.

To power the device, our lab uses a number of different bench setups including the HP4145 Semiconductor Parameter Analyzer, HP8657D and HP8657A Signal Generators, HP8590B Spectrum Analyzer, HP3457A Multimeters, Tek576 Curve Tracer, and Tek2221A Digital Storage Oscilloscope. Several probe stations including the Karl Suss PM5, Wentworth, and Signatone are used in the liquid crystal setup.

Type of liquid crystal we use for our analysis:

  • K-18 has nematic to isotropic state transition at about 30C.
  • K-21 has a nematic to isotropic state transition at about 45C. Therefore, K-21 is being used for components that exhibit higher power consumption