NMOS Second Breakdown Simulation

mos2ex08.in : NMOS Second Breakdown Simulation

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

This example demonstrates fabrication and second breakdown analysis of a short channel structure with non-isothermal energy balance models.

  • A short channel MOSFET is created in Athena,
  • Regridding in DEVEDIT
  • Selection of the coupled solution of energy balance and lattice heating equations
  • Electrical analysis using the curve tracer algorithm to trace the IV curve

Deep submicron devices should be simulated using the Energy Balance Model due to velocity overshoot, and nonlocal impact ionization effects, which could substantially influence device characteristics. For high current levels, the thermal self-heating effects can also play an important role by decreasing mobility and impact ionization rate. This example demonstrates second breakdown simulation with the non-isothermal energy balance model using curve tracing algorithm.

A fully coupled approach is used to solve five equations in this device. This provides much improved convergence over decoupled techniques used in older Atlas versions.

The workfunction, interface charge and MOS models are set using the syntax as described in earlier examples. The energy balance equation for electrons and lattice energy balance equation are set by models hcte.el lat.temp . The impact statement is used to assign the energy relaxation length for Selberherr model. Thermal boundary conditions are required with any non-isothermal simulation. These are defined in the thermcontact statement. A value of the thermal conductance is specified at the thermal contact located along the substrate. Thermal isolation conditions are assumed on the all other surfaces.

The curvetrace statement is used to initialize parameters for curve tracing algorithm. A full description of the curve tracing syntax is included with the MOS snapback example. The gate voltage is ramped to 1V, and then the solve curvetrace statement is used to activate the curve tracing algorithm.

Plotting the internal drain bias versus drain current in TonyPlot will display the second breakdown curve. The resulting curve from Atlas shows several turning points. The second breakdown occurs at the final stage where the voltage drops sharply. At this point both the lattice and carrier temperatures are high.

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