Optical Diagnostics Tool Development - overview
Time-Resolved Emission (TRE) measurement, also known as Picosecond Imaging Circuit Analysis (PICA), based on the collection of near infrared light (NIR) emitted by hot carriers in the transistor channel, is an invaluable method that has been widely adopted by the test and failure analysis communities. This technique enables one to non-invasively probe the switching activity inside VLSI circuits to measure skews, propagation delays, duty cycles, etc. Over the years, its capabilities have been continuously extended by the use of Light Emission due to Off-State Leakage Current (LEOSLC) to completely new applications, such as logic state mapping, pattern debugging, latchup ignition study, power supply noise and slew rate measurement, self heating estimation, systematic and random device variability characterization, security and counterfeit detection for ICs, etc.
However, the continuous trend of the semiconductor industry towards smaller devices and lower supply voltages has caused significant changes in the intensity and spectrum of light emitted by ICs: the detectable light decreases exponentially with the electric field in the transistor, and linearly with the lateral dimension of the FET. Furthermore, the reduction in circuit voltages has also caused a progressive shift of the spectral distribution of the emitted light towards longer wavelengths as shown by previous work. For all these reasons, detectors superior to the current state of the art InGaAs SPADs (Single-Photon Avalanche Diode), with higher sensitivity at these longer wavelengths, as well as lower intrinsic noise (dark counts), are needed.
We have co-developed the next generation PICA tool with partners and US government agency based on Super Conducting Detector technology coupled with high resolution Solid Immersion Lens.