A novel technique for the measurement of generation lifetime in undoped polysilicon material using the principle of charge centroids

A novel technique is presented for the measurement of carrier generation lifetime in as-deposited polycrystalline silicon material. The test structure is a metal-oxide-semiconductor-oxide-semiconductor capacitor fabricated by depositing polysilicon followed by silicon dioxide on an oxide grown on a single-crystal silicon substrate. A voltage step is applied to the top gate such as to cause deep depletion in the substrate. The resulting capacitance transient is dominated initially by generation of electron-hole pairs in the polysilicon, via the charge centroid effect which arises because the polysilicon body region is electrically isolated. The technique could be used to monitor polysilicon quality during the fabrication of large-area electronic circuits.