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COCOS metrology enables gate dielectrics to be quickly monitored in a non-contact manner for all wafer sizes including 300mm. This approach has been developed during the last five years and is already implemented in many microelectronic fablines. The method uses corona charging in air to deposit an electric charge on a dielectric thus changing the electric field in the dielectric and in the semiconductor. The response is measured in a non-contact manner by using a contact potential difference, V[sub CPD], in the dark and under strong illumination. This measurement gives the voltage drop across the oxide, V[sub OX] and the surface barrier, V[sub SB], as a function of the corona charge dose, δQ[sub c]. These basic relationships are then used in a very straightforward manner to determine the flat band voltage, V[sub FB], the total charge required to achieve the flat band condition, Q[sub TOT] and the interface trap spectra, D[sub TT], across the silicon bandgap in an energy range from flat band to deep inversion. Measurements of V[sub CPD] vs. δQ[sub c] under accumulation (or strong inversion) give the oxide capacitance and, after correcting for quantum effects, provide a very accurate measure of the electrical dielectric thickness. Application of corona discharge to characterize dielectrics was originally suggested by Williams and Willis. COCOS introduced whole wafer charging based upon the development of a very precise wire-type corona discharge gun. With this charging technique, a near equi-potential condition is created across the dielectric for reducing leakage along the surface. In certain applications whole wafer uniform pre-charging is followed by a charge pulse on a smaller site. The contact potential difference transients after cessation of the pulse give the I-V characteristics of the dielectric. The latter technique is the basis for only recently introduced COCOS measurement of oxide thickness and stress induced leakage current. [ABSTRACT FROM AUTHOR]