Two-photon optical beam induced current imaging through the backside of integrated circuits

Two-photon optical beam induced current (TOBIC) images were acquired through the polished backsides of integrated circuits. An excitation beam with a photon energy below the band gan can traverse even thick substrates virtually unattenuated. At the focus-and only there-two-photon absorption generates electron-hole pairs very efficiently when using a sub-picosecond light source. An additional advantage of TOBIC is a significant increase in spatial resolution. With high numerical aperture objective lense features smaller than 1 mu m are easily discernible. (C) 1997 American Institute of Physics. [S0003-6951(97)02644-2].