Inverse-Geometry Dependence of MOS Transistor Electrical Parameters

Precise determination of transistor electrical parameters is essential for accurate circuit simulation. The strong geometric dependences of MOS transistor electrical parameters can be modeled by the inverse-geometry formula. However, special care is needed in using the inverse-geometry formula. To prevent the short-channel and narrow-width effects being adversely mirrored to the drain-current evaluation of large transistors, we propose to clamp the dependences of transistor electrical parameters on small-geometry effects at a boundary (L _CLP, W _CLP). In principle three transistors with two different channel lengths and two different channel widths are required to extract the geometric dependence of various electric parameters. Our analysis shows that a set of five test transistors can increase the extraction accuracy by a factor of two, and thus is a better choice when both the modeling accuracy and test clip complexity are considered.