UMOS Device

powerex22.in : UMOS Device

Requires: Victory Process - 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".

This example demonstrates 2D process simulation and basic device tests for a U-shaped trench MOSFET or UMOS .

UMOS device belongs to family of Vertical MOSFET devices which differ from standard (horizontal) MOSFETs by the fact that the gate is "vertical" and the drain is on the bottom of device. In UMOS, the vertical gate is formed by etching and oxidizing of a deep trench in silicon. The device uses two connections to the source which results in much larger area through which the current can flow. This reduces the ON resistance of the device which allow to handle higher powers than standard MOSFETs. The vertical nature of the UMOS structure allows to achieve good device characteristics with smaller "layout footprint" than conventional power MOSFETs.

Since UMOS is a symmetrical device only half of the structure is simulated. The full structure is later generated using Mirror capability within Victory Mesh .

Most of important geomentrical and process parameters of the UMOS structure are parametrized using set capability of DeckBuild which allows easy process and device optimization using VWF.

The key process step, the trench formation, is simulated by combination of two etch models:

  • geometrical angled dry etch
  • geometrical wet etch with the curvature of the trench bottom specified by RADIUS

This deck takes advantage of Victory Process capability of adjusting volume mesh for specific implant/diffusion steps. It starts with a very coarse volume mesh which allow to speed up epitaxy and trench formation steps. Then additional volume mesh lines are placed in important areas around the trench as well as in implanted areas. Also, the fine grid initially required to capture a sharp peak of N+ Arsenic implant was later coarsened by using Line remove capability of Victory Process.

In this example, in order to decrease simulation time the default analytical model is used for all implant steps. The Monte Carlo implant model is recommended for most real device simulation.

Several parameters of the device structure are extracted along the way and can be used for process optimization.

Finally, the full structure is "prepared" for device simulation using Victory Mesh . First, the final status of Victory process simulation is loaded, then the structure is mirrored, and remeshhed and refined using Delaunay mesh. The finest refinement takes place along the gate to obtain reproducible Vt. The nesh is also refined at other interfaces and along the junction for accurate Breakdown Voltage simulation.

In the end Victory Device is used to extract two basic device characteristics:

  • Threshold voltage Vt
  • Breakdown voltage BV .

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.