Appendix D: Using a Model 82 C-V System Model 4200A-SCS Parameter Analyzer Reference ManualD-48 4200A-901-01 Rev. C / February 2017Basic device parametersThe following topics provide additional detail on device parameters and how they are calculated.Determining device typeThe semiconductor conductivity type (p or n dopant ions) can be determined from the relative shapeof the C-V curves (see Analysis methods (on page D-47)). The high-frequency curve gives a betterindication than the quasistatic curve because of its highly asymmetrical nature. Note that the C-Vcurve moves from the accumulation to the inversion region as gate voltage, V GS, becomes morepositive for p-type materials, but the curve moves from accumulation to inversion as V GS becomesmore negative with n-type materials (Nicollian and Brews 372-374).• If C H is greater when VGS is negative than VGS when poitive, the substrate material is p-type.• If C H is greater with positive V GS than negative VGS, the substrate is n-type.• The end of the curve where C H is greater is the accumulation region, while the opposite end ofthe curve is the inversion.Oxide capacitance, thickness and gate areaThe oxide capacitance, C OX, is the high-frequency capacitance with the device biased in strongaccumulation. Oxide thickness is calculated from C OX and gate area as follows:Where:• tox = oxide thickness (nm)• A = gate area (cm 2)• εox = permittivity of oxide material (F/cm)• C ox = oxide capacitance (pF)You can rearrange the above equation to calculate gate area if the oxide thickness is known. Notethat εOX and other constants are initialized for use with silicon substrate, silicondioxide insulator, andaluminum gate material, but may be changed for other materials.
