3D Device Simulation - Effect of Lattice Heating

soiex09.in : 3D Device Simulation - Effect of Lattice Heating

Requires: Device 3D/Giga 3D
Minimum Versions: Atlas 5.21.1.R

This example demonstrates an Id/Vds 3D analysis of a short channel ultra-thin SOI transistor with a body contact. Two simulations are performed with and without lattice heating turned on.

Such simulations cannot be performed accurately using a 2D simulator because the body electrode is located in a different z-plane compared with the drain, gate and source. The example shows:

  • Formation of 3D structure using Atlas syntax
  • Id/Vds solution with Vgs=3.0V

The formation of this 3D structure is performed using the Atlas syntax. The syntax used is very similar to that of a 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 SOI device is composed of a 0.2 micron layer of silicon on a 0.4 micron silicon dioxide substrate. The device has a 17 nm thick gate oxide and a gate length of 1.0 microns (effective channel length is 0.8 microns). The gate width is 2.5um. The body contact location is defined by the following statement

electrode name=body x.min=1 x.max=2 y.min=0.0 y.max=0.0 z.min=3.5 z.max=4

The model statement is used after the device description to select a set of physical models for this simulation. In this case the example uses conmob: the doping dependent low field mobility model, fldmob: the lateral electric field-dependent mobility model, srh: Shockley-Read-Hall recombination, auger: recombination accounting for high level injection effects, and bgn: band gap narrowing.

Also, in the lattice heating simulation input deck, an additional parameter lat.temp is placed on the model statement. This switches on lattice heating inside the simulation. With this option it is also necessary to include a thermal boundary condition. This is included using the following statement:

thermcontact num=1 ext.temp=300 x.min=0 x.max=3 y.min=0.35 z.min=0 z.max=4

and forces the temperature on the bottom of the device to be fixed at 300K.

The impact statement is used to specify Selberherr model. The contact statement is used to assign the work function on the polysilicon gate.

The numerical methods used are different to previous 2D examples and are chosen by the statement method bicgst. This chooses a bi-conjugate gradient solution scheme which has been found to give robust and fast simulations of three dimensional devices.

The drain voltage is set to 0.1V, and then the gate voltage is swept to 3.0V to obtain the operating gate voltage.

Then the gate voltage is set to 3.0V, and then the drain voltage is swept to its final value.

The IV results are displayed using TonyPlot showing the ID-VG characteristics both with and without lattice heating.

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.