Emission-based IC Diagnostics - overview
Time to market pressure drives the efforts of high-end microprocessor debug and diagnostics. The conventional software and tester-based diagnostic techniques are often faster and cheaper. However, sometimes they are not very efficient and the diagnostic resolution is not high enough. Although, it is time consuming, the emission-based debug/diagnostics/characterization techniques prove to be very accurate with high resolution. For many years, they have been successfully used for diagnosing high-end IBM products.
Picosecond Imaging for Circuit Analysis (PICA), also known as Time-Resolved Emission (TRE), based on the collection of near infrared light (NIR) emitted by hot carriers in the transistor channel, is an invaluable method for detecting timing related faults in backside packaged VLSI circuits. The capability of internally probing signal delays and skews by detecting the hot-carrier luminescence has been widely extended during the years. Light Emission due to Off State Leakage Current (LEOSLC), oxide tunneling current and carrier recombination have led to completely new application areas, such as latchup ignition, power supply noise , slew rate , self heating, variability, etc.
Above is a PICA movie of a running ring oscillator where the emission tracks the RO stage transition (RO)
Above is a light emission map that was used to diagnose chip process variations
Above is an example of PICA waveforms acquired from the Phase-Locked Loop (PLL) circuit of a IBM high-end processor, showing the high speed clock