Nondestructive internal observation of metal-oxide-semiconductor LSI designed by 0.8 mu m rule

A metal-oxide-semiconductor (MOS)-LSI chip was designed by the 0.8 mu m rul e, and a passivated film on the chip was etched off while keeping the chip mounted on a ceramic package. The acoustic signal generated by irradiation of a chopped electron beam was picked up by a piezoelectric detector (PZT e lement) attached to the back of the package. The results of observation by electron-acoustic microscopy (EAM) are as follows: (a) the observable depth (t(x)) was proportional to the electron range (R-e); (b) t(x) shifted to a shallower side (about 50% of R-e) compared to the case of bipolar transist ors; (c) contact holes (0.8 mu m(2)) were distinctly observed at HV = 19 kV ; and (d) the resolution of our EAM was estimated to be about 0.4 mu m at a chopping frequency of the election beam of 1 MHz and an acceleration volta ge of 18-19kV.