consider the gate oxide capacitance defined as Cg = WL COX, Since the gate oxide capacitance C is scaled down by a factor of S, we can predict that the transient characteristics, i.e., the charge-up and charge-down times, of the scaled device will improve accordingly.Since the drain current flows between the source and the drain terminals, the instantaneous power dissipated by the device (before scaling) can be found as: Notice that full scaling reduces both the drain current and the drain-to-source voltage by a factor of S hence, the power dissipation of the transistor will be reduced by the factor S*S. Now consider the power dissipation of the MOSFET.Since all terminal voltages are scaled down by the factor S as well, the linear-mode drain current of the scaled MOSFET can now be found as: Consequently, the transconductance parameter kn will also be scaled by a factor of S. The aspect ratio WIL of the MOSFET will remain unchanged under scaling.The gate oxide capacitance per unit area, on the other hand, is changed as follows.the Poisson equation describing the relationship between charge densities and electric fields dictates that the charge densities must be increased by a factor of S in order to maintain the field conditions.This scaling option attempts to preserve the magnitude of internal electric fields in the MOSFET, while the dimensions are scaled down by a factor of S.W, L, tox are decreased by S, while ND,NA doping concentrations are increased by S.All horizontal and vertical dimensions of the large-size transistor are then divided by this scaling factor to obtain the scaled device.Scaling of MOS transistors is concerned with systematic reduction of overall dimensions of the devices as allowed by the available technology, while preserving the geometric ratios found in the larger devices.Reducing the size of MOSFET is called as scaling.
High integration of MOSFETs on IC, requires reduction of size of MOSFET.Mosfet Scaling Deepa Asst.Professor SIT,Tumakuru
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