Gate Turn-on Transient

mos2ex03.in : Gate Turn-on Transient

Requires: SSuprem 4/S-Pisces
Minimum Versions: Athena 5.22.1.R, Atlas 5.22.1.R

This example demonstrates the transient simulation of a MOS transistor including:

  • Formation of a MOS structure in Athena
  • Interface from Athena to Atlas
  • Specification of external RC elements to make an NMOS inverter
  • Transient simulation of gate turn-on

The process simulation follows a standard LDD MOS process. Further description of the MOS process simulation and the Athena to Atlas interface can be found in the description of the MOS examples.

In Atlas the first task is setting the gate workfunction using the contact statement and interface charge using the interface statement. The models used for this simulation are selected using the macro mos . This model set uses the CVT mobility model and SRH recombination. A two-carrier solution is also specified on the models statement. Two-carrier solutions are necessary for transients and when external passive elements are used irrespective of the type of device being simulated.

The second contact statement is used to set the external resistance and capacitance on the drain electrode. A resistance of 1.0e5 ohms.um is used to correspond to a load resistor in a memory cell. A capacitance of 0.5pF/um is specified to emulate the gates and interconnect the drain must drive. These external elements emulate the formation of an NMOS inverter in SPISCES. This contrasts with the previously described example using MixedMode.

The initial state of the device is set at 5.0V on the drain. The local initial guess method is used to allow large change in the drain bias in a single step. This local method will only converge if the change in current caused by the voltage step is small. This is true here since the gate voltage is zero.

The solve statement for the transient simulation contains the final gate voltage, the ramptime of the gate voltage, the initial timestep and the final simulation time. Only the initial timestep is specified in the solve statement. All other timestep sizes are calculated by Atlas based on the local truncation error in the solution.

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