Effect of Poly Doping on Threshold Voltage

mos2ex16.in : Effect of Poly Doping on Threshold Voltage

Requires: S-Pisces
Minimum Versions: Atlas 5.24.1.R

This example shows the dramatic effect of depletion in the poly gate when the doping in the poly is reduced below its maximum level. The I-V curves show that even a doping density of 1e20/cm3 in the poly is not sufficient to prevent depletion, loss of current drive and a shift in the threshold voltage of the n-MOSFET.

The first indication of poly depletion is non ideal C-V curves as shown in the previous "Poly Depletion" example. Reduced doping in the poly gate can be a combination of insufficient implant dose, counter doping of P+ poly and dopant evapouration during uncapped anneals.

The program runs three identical simulations the only difference being the doping in the poly gate. Three doping levels are simulated, 1e19, 1e20 and 1e21/cm3. At the end of the three simulations, the I-V curves of the n-MOSFET in the region of the threshold voltage are plotted. The effect of poly doping is demonstrated by the increased threshold voltage and reduced current drive with reduced poly doping.

To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.