To clarify the influence of crystal-originated “particles” (COPs) on gate oxide integrity (GOI), a new GOI evaluation method has been developed. This method compares the GOI of a metal oxide silicon (MOS) capacitor which includes a COP with a MOS capacitor that is COP-free by measuring the capacitors' I–V characteristics. Furthermore, to study the relationship between the shape of COP and GOI, the COP microstructure on the wafers was observed by atomic force microscopy (AFM) in the as-received state, after NH4OH/H2O2/H2O (SC-1) cleaning, high temperature annealing and repolishing. It was found that the presence of COP was the main cause of GOI failure and also that the shape of COP was closely related to the GOI yield. The microstructure of the original COP in a crystal is concluded to be an octahedral void and the same as an IR scattering defect.
Influence of Fe contamination in CZ-grown silicon single crystal on oxidation-induced stacking fault (OSF) generation density, carrier recombination and generation lifetimes, and gate oxide integrity (GOI) yield characteristics was experimentally investigated. Two Fe-doped silicon ingots were grown and tested. Concentration of Fe-B ([Fe-B]) in these silicon ingots measured by deep level transient spectroscopy (DLTS) was about 5×1011 cm-3 and 5×1012 cm-3, respectively. OSF density generated by three-step annealing showed dependence on [Fe-B]. Carrier recombination lifetime (τ r) showed good correlation with [Fe-B], and a quantitative relationship was established. OSF density after one-step annealing, carrier generation lifetime (τ g) and GOI yield were not so dependent on [Fe-B].
A new technique for transmission electron microscope (TEM) observation of grown-in defects has been developed. The grown-in defects beneath the surface, at the “origin of crystal originated particles (COPs)”, are detected using a laser particle counter combined with an atomic force microscope (AFM). Subsequently, the position of the “origin of COP” using the above mentioned detection method is marked at the surface by applying the anodization technique using an AFM, and the TEM samples are prepared using this marking. Through this technique, we have succeeded in observing the “origin of COPs” using a TEM. It has been clarified that the “origin of COPs” are imperfect octahedron voids with thin oxide walls with no strain around them. These results have indicated that the “origin of COPs” are equivalent to the “laser scattering tomography defects (LSTDs)”.
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