6.1 Overview
6.2 Reinitializing Sentaurus Structure Editor
6.3 Automatic Region-Naming Mode
6.4 Selecting Materials
6.5 Selecting the Default Boolean Expression
6.6 Creating a Cuboid Region
6.7 Changing the View and Zooming
6.8 Poly Reoxidation
6.9 Nitride Spacers
6.10 Defining the Contacts
6.11 Setting the Contacts at Existing Faces
6.12 Setting the Contacts at New Faces
6.13 Defining Constant Doping Levels in a Region
6.14 Defining Analytic Doping Profiles
6.15 Defining a Meshing Strategy in a Window
6.16 Defining a Multibox Mesh Strategy in a Refinement Window
6.17 Saving the Model
6.18 Meshing the Device Structure
6.19 Assignment
Section 2. Generating 2D Boundaries demonstrates the steps for building a 2D SOI MOSFET. Sentaurus Structure Editor also can construct 3D structures.
This section introduces the procedure to build a 3D MOSFET as shown in Figure 1.
Due to the similarity of 2D and 3D operations, many commands and operations executed in this section are identical to those described in the 2D case. Therefore, cross references to relevant sections will be given to avoid duplication of text.
See Section 2.2 Reinitializing Sentaurus Structure Editor.
By default, Sentaurus Structure Editor automatically assigns region names such as region_1 and region_2 to newly created regions. This is useful in some applications but, in most cases, you might prefer to use your own names, which are more descriptive and easier to remember.
To switch off the automatic region-naming mode, choose Draw > Auto Region Naming (ensure there is no check mark next to the command).
When the mode has been switched off, you will be prompted to enter the region name whenever a new region is created.
The corresponding Scheme command is:
(sdegeo:set-auto-region-naming OFF)
See Section 2.4 Selecting Materials.
See Section 2.5 Selecting the Default Boolean Expression.
To create a cuboidal silicon substrate region:
Other regions of the device, that is, the isolation trenches, the gate oxide, and the polysilicon gate can be created in a similar way. Use the following coordinates.
Region | Name | Material | Coordinates |
---|---|---|---|
Substrate | SubsSilicon | Silicon | (-0.25 -0.2 0), (0.25 0.2 -1.0) |
Right trench | TrenchOxide_Right | SiO2 | (-0.2 -0.2 0), (0.2 -0.1 -0.2) |
Left trench | TrenchOxide_Left | SiO2 | (-0.2 0.1 0), (0.2 0.2 -0.2) |
Gate oxide | GateOxide | SiO2 | (-0.15 -0.2 0), (0.15 0.2 0.002) |
Poly gate | PolyGate | PolySi | (-0.1 -0.1 0.002), (0.1 0.2 0.1) |
The corresponding Scheme commands for creating these regions are:
(sdegeo:create-cuboid (position -0.25 -0.2 0) (position 0.25 0.2 -1.0) "Silicon" "SubsSilicon") (sdegeo:create-cuboid (position -0.15 -0.1 0) (position 0.15 0.1 0.002) "Oxide" "GateOxide") (sdegeo:create-cuboid (position -0.2 -0.2 0) (position 0.2 -0.1 -0.2) "Oxide" "TrenchOxide_Right") (sdegeo:create-cuboid (position -0.2 0.1 0) (position 0.2 0.2 -0.2) "Oxide" "TrenchOxide_Left") (sdegeo:create-cuboid (position -0.1 -0.1 0.002) (position 0.1 0.2 0.1) "PolySi" "PolyGate")
Sentaurus Structure Editor supports functions that allow the structure in the view window to be seen from different perspectives:
Figure 4 and Figure 5 show the current status of the structure viewed from different angles.
To create a poly reoxidation region:
Region | Name | Material | Coordinates |
---|---|---|---|
Poly reoxidation 1 | PolyReOxide1 | SiO2 | (-0.103 -0.103 0) (0.103 0.2 0.1) |
Poly reoxidation 2 | PolyReOxide2 | SiO2 | (-0.15 -0.103 0) (0.15 0.2 0.005) |
The corresponding Scheme commands are:
(sdegeo:set-default-boolean "BAB") (sdegeo:create-cuboid (position -0.103 -0.103 0) (position 0.103 0.2 0.1) "Oxide" "PolyReOxide1") (sdegeo:create-cuboid (position -0.15 -0.15 0) (position 0.15 0.2 0.005) "Oxide" "PolyReOxide2")
To add nitride spacers:
Region | Name | Material | Coordinates |
---|---|---|---|
Nitride spacers | NiSpacer | Si3N4 | (-0.15 -0.15 0), (0.15 0.2 0.08) |
To round the spacer corners and edges:
The corresponding Scheme commands are:
(sdegeo:create-cuboid (position -0.15 -0.15 0) (position 0.15 0.2 0.08) "Nitride" "NiSpacer") (sde:define-parameter "fillet-radius" 0.03 0.0 0.0 ) (sdegeo:fillet (list (car (find-vertex-id (position -0.15 -0.15 0.08))) (car (find-vertex-id (position 0.15 -0.15 0.08))) ) fillet-radius)
To define a contact:
As in the 2D case, contacts do not become effective unless they are associated with part of the device structure. In 3D applications, contacts are typically defined on the faces of the device.
To place a substrate contact:
The corresponding Scheme commands are:
(sdegeo:set-contact (find-face-id (position 0 0 -1) ) "substrate") (sdegeo:set-contact (find-face-id (position 0 0 0.1)) "gate")
The source and drain only occupy part of an existing face (the top silicon substrate face). Therefore, new faces must be created before these two contacts can be placed.
To create a new face, create a metal cuboid to imprint the face:
Region | Name | Material | Coordinates |
---|---|---|---|
Source cuboid | Source | Metal | (0.17 -0.1 0) (0.25 0.1 0.05) |
Drain cuboid | Drain | Metal | (-0.25 -0.1 0) (-0.17 0.1 0.05) |
The corresponding Scheme commands for creating the two metal regions and replacing them with contacts are:
(define SOURCE (sdegeo:create-cuboid (position -0.25 -0.1 0) (position -0.17 0.1 0.05) "Metal" "Source")) (sdegeo:set-contact SOURCE "source" "remove") (define DRAIN (sdegeo:create-cuboid (position 0.17 -0.1 0) (position 0.25 0.1 0.05) "Metal" "Drain")) (sdegeo:set-contact DRAIN "drain" "remove")
Defining a constant doping level in a 3D region is similar to that for a 2D region (see Section 3.3 Defining Analytic Doping Profiles).
To define a constant doping level of 1x1017 cm-3 in the silicon substrate:
The corresponding Scheme commands are:
(sdedr:define-constant-profile "Const.Bulk" "BoronActiveConcentration" 1e17) (sdedr:define-constant-profile-region "PlaceCD.Bulk" "Const.Bulk" "SubsSilicon") (sdedr:define-constant-profile "Const.Poly" "ArsenicActiveConcentration" 1e20) (sdedr:define-constant-profile-region "PlaceCD.Poly" "Const.Poly" "PolyGate")
Defining an analytic doping profile in a 3D region is comparable to the 2D case. The only difference is that, in the 3D case, the reference for the profile is a 2D plane. In the 2D case, it is a 1D edge.
As in the 2D case, the definition of a profile in a 3D region involves two steps. The first step defines the baseline window and the second step defines the profile itself. The baseline window determines the lateral extent of the profile and serves as the reference point for the depth of the peak position of the profile.
The following instructions define the source and drain implantations, both in Gaussian shape, with a peak concentration of 1019 cm-3, a junction depth of 0.1 μm, and a lateral straggle/diffusion factor of 0.8.
To define a baseline window:
Junction | Baseline name | Start point | End point |
---|---|---|---|
Source | BaseLine.Source | (0.30 -0.25) | (0.15 0.25) |
Drain | BaseLine.Drain | (-0.15 -0.25) | (-0.30 0.25) |
The corresponding Scheme commands for these two definitions are:
(sdedr:define-refeval-window "BaseLine.Source" "Rectangle" (position 0.30 -0.25 0.0) (position 0.15 0.25 0.0) ) (sdedr:define-refeval-window "BaseLine.Drain" "Rectangle" (position -0.30 -0.25 0.0) (position -0.15 0.25 0.0) )
To define and place the Gaussian doping profiles:
The corresponding Scheme commands are:
(sdedr:define-gaussian-profile "Gauss.SourceDrain" "ArsenicActiveConcentration" "PeakPos" 0.0 "PeakVal" 1e19 "ValueAtDepth" 1e17 "Depth" 0.1 "Gauss" "Factor" 0.8) (sdedr:define-analytical-profile-placement "PlaceAP.Source" "Gauss.SourceDrain" "BaseLine.Source" "Both" "NoReplace" "Eval") (sdedr:define-analytical-profile-placement "PlaceAP.Drain" "Gauss.SourceDrain" "BaseLine.Drain" "Both" "NoReplace" "Eval")
To generate a meshing strategy that is globally effective, first create a refinement window covering the entire device area, then define a meshing strategy, and apply it to the window.
To generate a meshing strategy:
The corresponding Scheme commands are:
(sdedr:define-refeval-window "RefWin.Global" "Cuboid" (position -0.25 -0.2 -1.0) (position 0.25 0.2 0.1)) (sdedr:define-refinement-size "RefDef.Global" 0.1 0.1 0.1 0.05 0.05 0.05 ) (sdedr:define-refinement-placement "Place.Global" "RefDef.Global" "RefWin.Global" ) (sdedr:define-refeval-window "RefWin.Active" "Cuboid" (position -0.25 -0.2 -0.15) (position 0.25 0.2 0.0)) (sdedr:define-refinement-size "RefDef.Active" 0.025 0.025 0.025 0.0125 0.0125 0.0125 ) (sdedr:define-refinement-placement "Place.Active" "RefDef.Active" "RefWin.Active")
To add a multibox refinement strategy in the channel region:
Figure 13 shows the device after these steps with refinement windows.
The corresponding Scheme commands for placing the multibox are:
(sdedr:define-refeval-window "RefWin.Channel" "Cuboid" (position -0.12 -0.1 -0.05) (position 0.12 0.1 0)) (sdedr:define-multibox-size "RefDefMB.Channel" 0.1 0.1 0.01 0.05 0.05 0.001 1 1 -1.5 ) (sdedr:define-multibox-placement "PlaceMB.Channel" "RefDefMB.Channel" "RefWin.Channel" )
To save the model for later use, choose File > Save Model, or press Ctrl+S, or click the corresponding toolbar button.
The corresponding Scheme command is:
(sde:save-model "3dmos_sde")
where 3dmos_sde is the saved file name. See Section 2.12 Saving the Model for the various file types saved.
To create the mesh and save the device structure:
The structure with its doping conditions is saved in a TDR file n1_MOSFET3D_msh.tdr, which can be loaded into, for example, Sentaurus Device simulations.
Figure 15 shows the device after the meshing step.
The corresponding Scheme command is:
(sde:build-mesh "" "n1_MOSFET3D")
Click to view all the commands discussed in this section in the command file MOSFET3d_dvs.cmd.
The complete project can be investigated from within Sentaurus Workbench in the directory Applications_Library/GettingStarted/sde/MOSFET3D.
Create a FinFET structure similar to the one shown in Figure 16.
Click to view a solution of the command file FinFET_dvs.cmd.
The complete project can be investigated from within Sentaurus Workbench in the directory Applications_Library/GettingStarted/sde/FinFET.
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