3D Trench IGBT

sicex09.in : 3D Trench IGBT

Requires: Victory Process, Victory Mesh, Victory Device
Minimum Versions: Victory Process 7.30.4.R, Victory Mesh 1.4.6.R, Victory Device 1.14.1.R

By default Victory Process and Device run on just one processor. To ensure better perfomance on your computer the following simulation condition simflags="-P all" could be specidied in the go line starting Victory Process or Device. This means that all processors available will be used. If you want to use a smaller number of processors you can substitute "all" with a desired number, e.g. simflags="-P 4".

Silicon based power devices are still dominant today in power electronics. However, wide bandgap semiconductors like SiC are now more and more used for high power, high-temperature applications because of superior thermal conductivity, lower intrinsic carrier concentration and better on-resistance compare to Silicon, which is a key figure of merit in power switching applications.

Simulating SiC devices is however more challenging compare to Silicon. Indeed very low intrinsic concentration combined with high doping values is usually detrimental to convergence. Victory Device can handle this situation thanks to his built-in extended precision solvers. Indeed whereas normal 64bits version has a relative accuracy of around 1e-16, 80 bits version can increase the accurary up to 1e-19, 128bits to 1e-32 and 256bits to 1e-63. We may however get some penalty in term of simulation time especially for 128 and 256 bits version. SiC exhibits hexagonal crystal structures. As a consequence anisotropy features in many important physical parameters like impact ionization must be taken into account.

The following example demonstrate 3D trench SiC IGBT simulation using Victory Cell and Victory Device.

The particularity of this device is to have low doping long drift region of about 160um. This will lead to high breakdown voltage. In this example we did not focus only on breakdown voltage simulation but we also wanted to perform IV simulation including IDVG and IDVD to illustrate a 3D specific effect. Indeed a "hump" effect was observed on the IDVG characteristic due to their non planar structure as reported in "Quantitative Analysis of Hump Effects of Gate-All_Around Metal_Oxide_Semiconductor Field_Effect Transistors" Woojun Lee,and Woo Young Choi Japanese Journal of Applied Physics 49 (2010) 04DC11. This "hump" effect is characterized in the IDVG curve as a parasitic transistor. This may be problematic in term of power consumption since it increases the off-current. In order to overcome this problem a non-Manhattan structure (including rounded trench corner instead of 90 degree trench corner) was simulated. The "hump" effect is reduced and the breakdown voltage improved.

In order to create the 3D structure we used Victory Cell our 3D process simulator. Victory Cell is very suitable for 3D SiC power devices simulation since it is layout driven, accurate, fast and easy to use. The 3D structure creation takes only few minutes. After the process simulation is done a 3D structure is saved using a tetrahedron mesh to ensure that any shape created during 3D process simulation is well conserved and transferred to Victory Device for further device simulation. Device simulations were performed using extended precision arithmetic, 80 bits or 128-bit depending on the type of simulation done, to be sure to resolve low intrinsic carrier concentrations.

As mentioned above we can clearly see the effect of the trench corner on the IDVG and IDVD characteristics. 2D cut plane were also made on the diagonal of the device right at the trench corner where we can clearly see higher electron current density for the Manhattan compare to the case where the trench corner was rounded. Note that BV is also affected by this effect and BV of around 12KV is obtained when the trench edge is rounded. We can clearly see when we plot the 3D structure that the maximium of the Electric Field as well as the Impact Generation rate is located at the bottom of the trench.

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.