Structured Mesh Generation

1. Overview

Structured mesh generation uses a system of user‑defined grid lines to control mesh size across the device, with optional refinement near critical features such as metallurgical junctions and oxide boundaries.

The definition process begins with defining a grid template composed of horizontal and vertical line groups. These line groups establish a base lattice onto which the mesh will be constructed. By positioning these grid lines strategically, the user can concentrate nodes in regions where higher resolution is required, at semiconductor–oxide interfaces or near junction transitions for example.

The intersections of the orthogonal grid lines, combined with the geometric boundaries of the simulated regions, form the initial set of node points. These nodes serve as the foundation for generating the finite‑element mesh, enabling a controlled and predictable mesh structure while allowing for localised refinement where greater numerical accuracy is needed.

2. Usage Instructions

2.1. Mesh Construction Grid

Before creating a finite element device model, it is important to ensure that at least one region is defined and a suitable meshing grid has been specified.

To define a rectangular meshing grid:

1. From the Menu, select Mesh -> Define Mesh Construction Grid. This will open a properties dialog.

2. Click the Add button to create a new group of grid lines.

3. In the dialog box, define the properties of the grid line group.
4. Specify the rectangular area using X and Y coordinates, for example, (0,0) to (5,5).
5. Set the spacing between the grid lines.
6. The grid lines will appear overlaid on the device structure.
7. Click OK to generate the collection of grid lines over the defined area.

Repeat this process for both the horizontal (X) and vertical (Y) directions until a suitable meshing grid of intersecting lines is achieved. Close the Mesh Construction Grid window by clicking the X in the top-right corner.

2.2. Mesh Generation

Once the initial meshing grid has been defined, this command will generate the nodes at the intersections of those lines and triangulate them to form the finite element mesh. The Delaunay algorithm is used and additional checks are made to ensure optimal triangle shapes, reducing narrow or poorly shaped elements that can impact simulation accuracy.

To generate a finite element model:

1. From the Menu, select Mesh -> Generate Finite Element Mesh Model. This will open the mesh properties dialog.

2. If automatic mesh refinement is required, enable the Mesh Refinement Options checkbox. By default, this option is disabled. When enabled, you can adjust the mesh refinement settings as needed.

3. Once you are satisfied with the settings, click OK to generate the mesh.

4. Depending on the complexity of the device model and the meshing grid, the generation process may take some time. The progress of the mesh generation will be displayed in the status window in the centre of the screen. Once complete, the finished FE model will be displayed. The P and N regions of the device will also be plotted, highlighting the position of the metallurgical junction, which is the point where the net doping concentration is zero cm^-3.

3. Parameters

3.1. Mesh Construction Grid

Each collection of grid lines is defined by the following parameters.

3.1.0.1. Grid Line Type

Name	Description	Unit
Orientation	Used to specify the direction of the grid lines. Options: [Horizontal, Vertical]	-
Interval	Used to determine the spacing pattern for the grid lines. Options: [Fixed, Graded]	-

3.1.0.2. Coordinates

Name	Description	Unit
X1	The x-coordinate of the lower-left corner of the rectangular area.	µm
X2	The x-coordinate of the upper-right corner of the rectangular area.	µm
Y1	The y-coordinate of the lower-left corner of the rectangular area.	µm
Y2	The y-coordinate of the upper-right corner of the rectangular area.	µm

3.1.0.3. Spacing Between Lines

Name	Description	Unit
Spacing	If Interval is Fixed, this sets a uniform spacing between all lines.	µm
Top	If Interval is Graded and Orientation is Vertical, this sets the spacing at the topmost coordinate.	µm
Bottom	If Interval is Graded and Orientation is Vertical, this sets the spacing at the bottommost coordinate.	µm
Left	If Interval is Graded and Orientation is Horizontal, this sets the spacing at the leftmost coordinate.	µm
Right	If Interval is Graded and Orientation is Horizontal, this sets the spacing at the rightmost coordinate.	µm

3.2. Mesh Refinement

Name	Description	Unit
Number of Iterations	Used to specify the number of refinement cycles.	-
Refinement Variable	Used to specify the physical property used for refinement. Options: [Net Doping, Distance from Junction]	-
Max Aspect Ratio	Sets the maximum allowed element aspect ratio for mesh quality control.	-

3.2.0.1. When using Net Doping

Name	Description	Unit
Measure as Signed-Log10	When checked, the refinement variable is measured on a logarithmic scale with sign.	-
Comparison Type	Used to define the method for comparing refinement values. Options: [Difference, Percentage Difference]	-
Refinement Threshold	Used to set the threshold value for refinement.	-

3.2.0.2. When using Distance from Junction

Name	Description	Unit
Distance	Distance threshold used for refinement, if an element is less than this distance from the junction it will be split.	µm
Reduction Factor	Factor by which the distance parameter is reduced after each refinement cycle.	-
Include Distance from Oxide	When checked, refinement also considers distance from oxide interfaces.	-