Microscopic lock-in thermography investigation of leakage sites in integrated circuits

The detection limit of infrared thermographic investigations can be improve d down to 10 muK by using a highly sensitive high-speed infrared camera in an on-line averaging lock-in thermography system. Together with a microscop e objective, this allows lock-in thermography to be used as a simple and se nsitive technique to localize the sites of leakage currents and other heat sources in electronic components. The practical realization of a novel lock -in thermography system is described and both test measurements and practic al applications are introduced. The detection limit for surface-near local heat sources in silicon is a few microwatts with a spatial resolution down to 5 mum. Leakage sites in several microelectronic structures are imaged an d assigned to the layout of the integrated circuit by comparing direct imag es with lock-in ones. The direct comparison of an averaged and background-s ubtracted stationary thermogram with a lock-in one, both measured under sim ilar conditions at the same sample, clearly demonstrates the gain in inform ation obtained by using lock-in thermography. (C) 2000 American Institute o f Physics. [S0034-6748(00)05210-2].