Quantitative determination of surface potentials on integrated circuits (IC) at high frequencies with the scanning electron microscope (SEM)

Some recent developments in low voltage E‐beam testing of ICs

“…This disadvantage of the retarding field method has been overcome by the installation of a feedback loop (Fleming & Ward, 1970;Gopinath & Sanger, 1971b;Balk et al, 1976;Feuerbaum, 1979) which keeps the current I constant by varying the retarding field voltage VG. The necessary variation of VG is equal to the applied specimen voltage V,, and thus provides a direct measure of Vsp.…”

“…A reduction of the influence~of'these local fields on the SE spectrum can be realized by installation of strong extraction fields above the specimen (Plows, 1969;Hannah, 1974;Balk et al, 1976;Dyukov et al, 1978;Feuerbaum, 1979;Menzel, 1981;Ura et al, 1980;Fujioka et al, 1981) either by placing a planar grid at high positive potential (Plows, 1969;Feuerbaum, 1979), or an immersion objective close to the specimen surface (Hannah, 1974;Balk et al, 1976). It was shown (Feuerbaum, 1979;Menzel, 1981;Ura et al, 1980;Fujioka et al, 1981) that with increasing extraction field strength the barrier above positively biased IC lines decreases and vanishes at certain field strengths that depend on the device geometry and the voltage applied to the IC lines.…”

“…The integral form of the spectrum is obtained by sending the SE through retarding fields established by either hemispherical grids (Goto et al , 1981) (Fig. 6) or planar grids (Fleming & Ward, 1970;Gopinath & Sanger, 1971a, b;Plows, 1969;Balk et al, 1976;Feuerbaum, 1979;Menzel & Brunner, 1983) (Fig. 7).…”

“…In this 'Voltage Measurement Mode' the e-beam acts as a tool, which measures time dependent voltages on IC-nodes, or which displays voltage distributions of large IC areas at different operating states by utilizing the dependence of the secondary electron (SE) spectrum on the potential of the emission point and on electrical fields above the IC (Balk et al, 1976;Crichton et al, 1980;Dyukov et al, 1978;Fazekas et al, 1976;Feuerbaum, 1979;Fleming & Ward, 1970;Fujioka et al, 1978;Gonzales & Powell, 1975;Gopinath & Sanger, 1971a, b;Hannah, 1974; Kotorman, 1980; Kubalek & 0 1985 The Royal Microscopical Society 33 1 Menzel, 1981;Lukianoff & TOUW, 1975;Menzel & Kubalek, 1981;Ostrow et al, 1982;Plows, 1969;Thomas et al, 1976;Wells & Bremer, 1968). …”