Determination of capacitance of DRAM capacitor as encountering roll-off problems

There has been trouble in measuring larger-area DRAM capacitors, especially at higher frequency. Somehow, different area size capacitors are supposed to have the same capacitance per unit area due to the reliable and repeatable process technology. A model using an algorithm based on Metal-Insulator-Semiconductor (MIS) structure is to be developed to understand the reasons why roll-off problems of measurements take place as the frequency gets higher and the areas of capacitors get larger. It is then found that the common unit capacitance C0, 1.1255E-5 nF/mum, of various size capacitors with 100Aring Ta2O5dielectric corresponds to the effective SiO2thickness, 30.5 Aring.