Method for obtaining the equivalent oxide thickness of a dielectric layer

A method for obtaining the equivalent oxide thickness of a dielectric layer comprising:

• providing a first semiconductor capacitor and a second semiconductor capacitor, wherein the first semiconductor capacitor comprises a first silicon dioxide layer and a first depletion region, the second semiconductor capacitor comprises a second silicon dioxide layer and a second depletion region, the first silicon dioxide layer and the second silicon dioxide layer have known equivalent oxide thicknesses, a first total impedance of the first semiconductor capacitor comprises first impedances of first regions and a first equivalent impedance corresponding to the first silicon dioxide layer, a second total impedance of the second semiconductor capacitor comprises second impedances of second regions and a second equivalent impedance corresponding to the second silicon dioxide layer, and the first impedances are respectively equal to the second impedances;
• by scanning capacitance microscopy, applying a modulation voltage to the first semiconductor capacitor and the second semiconductor capacitor to periodically vary widths of the first depletion region and the second depletion region and measuring a first scanning capacitance microscopic signal and a second scanning capacitance microscopic signal respectively corresponding to the first semiconductor capacitor and the second semiconductor capacitor;
• calculating an impedance ratio according to the equivalent oxide thicknesses of the first silicon dioxide layer and the second silicon dioxide layer, the first scanning capacitance microscopic signal, and the second scanning capacitance microscopic signal;
• providing a third semiconductor capacitor, wherein the third semiconductor capacitor comprises a dielectric layer and a third depletion region, a third total impedance of the third semiconductor capacitor comprises third impedances of third regions and a third equivalent impedance corresponding to the dielectric layer of the third semiconductor capacitor, and the third impedances are respectively equal to the first impedances;
• by the scanning capacitance microscopy, applying the modulation voltage to the third semiconductor capacitor to periodically vary a width of the third depletion region and measuring a third scanning capacitance microscopic signal corresponding to the third semiconductor capacitor;
• and
• obtaining an equivalent oxide thickness of the dielectric layer of the third semiconductor capacitor according to the equivalent oxide thickness of the first silicon dioxide layer, the first scanning capacitance microscopic signal, the third scanning capacitance microscopic signal, and the impedance ratio.