3D TFT Simulation

tftex06.in : 3D TFT Simulation

Requires: Device 3D/TFT 3D
Minimum Versions: Atlas 5.22.1.R

This example demonstrates Ids/Vgs and Id/Vds 3D analysis of a 10um channel length, ultra-thin TFT transistor. The example shows:

  • Formation of 3D structure using Atlas syntax
  • Id/Vgs solution with Vds=0.1V
  • Id/Vds solution with Vgs=1.5V

The formation of this 3D structure is performed using the Atlas syntax. The syntax used is very similar to that used to create a normal 2D example. The definition of dimensions in the third direction is defined by the z indicator. Thus z.min and z.max define extents in the z direction, just as x.min and x.max do in the x direction.

The TFT device is composed of a 0.05 micron layer of polysilicon on a 0.45 micron silicon dioxide substrate. The device has a 12 nm thick gate oxide and a gate length of 10 microns. The gate width is 80um.

After the device description the model statement is used to select a set of physical models for this simulation. In this case, these models are 'srh' recombination, bandgap narrowing, and the conmob and fldmob mobility models. The impact statement is used to specify the Selberherr model for impact ioisation in the 3D simulation. This is necessary to model "kink" effects that are often observed in TFT Id-Vd characteristics. The contact statement is used to assign the work function on the gate material. It this case an aluminum gate is used which assigns a workfunction of 4.10 V to the gate contact.

The numerical methods used are also similar to the previous example: METHOD gummel newton carr=2 . This means that if convergence is not reached in decoupled mode (gummel) the simulator will automatically switch to coupled mode (newton). In addition, a two carrier solution is performed by solving Poisson's equation for potential and the electron and hole continuity equations.

The drain voltage is set to 0.1V, and then the gate voltage is swept to 1.5V to measure the Ids/Vgs curve.

Then the gate voltage is set to 1.5V, and then the drain voltage is swept to 3V. At this point faster solutions are obtained using the coupled newton algorithm so the simulation switches to this method. The drain voltage is then ramped to 4V.

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.