The CGSim (Crystal Growth Simulator) code is specialized software for
simulation of Czochralski (Cz), Liquid Encapsulated Czochralski (LEC),
Vapor Pressure Controlled Czochralski (VCz), and Bridgman growth. The code provides
information to growers on the most important physical processes responsible
for crystal growth and quality. The CGSim package contains several modules
such as Basic CGSim, Defects, Flow Module, and CGSim View.
CGSim can be effectively applied to the following practical problems:
Control and optimization of the crystallization front
geometry and V/G distribution by adjustment of the hot zone and growth parameters.
Increase of the crystallization rate with keeping high crystal quality.
Control over stress and defects in the growing crystal.
Defect engineering via accurate adjustment of the heat shields.
Governing melt convection via crystal/crucible rotation
rates, magnetic fields of various strength and orientation. Stabilization
of convection in the melt while maintaining reasonable turbulent mixing.
Analysis of impurity transport in both the melt and gas.
Prediction of oxygen and carbon containing species concentrations in Si CZ
growth. Adjustment of growth conditions and modification of the hot zone
aimed at providing desired impurity concentrations.
Adequate account of encapsulant, turbulent gas flow,
and convective heat transport in liquid encapsulated growth.
Modelling support for design and optimization of new
crystal growth setups.
Capabilities of the CGSim package are illustrated through detailed
application examples listed below:
Heater power adjustment to provide the required
Calculation of crystallization front geometry
Automatic reconstruction of the geometry for
several crystal positions
Special models for anisotropic characteristics
The Basic CGSim program is developed for industries and research teams.
Graphical User Interface of the Basic CGSim code requires no special
computational skills. All setup and computational steps are highly automated
to minimize user efforts.
Work with Basic CGSim includes the following stages:
Specification of the growth system geometry
Specification of material properties
Boundary condition specification
Visualization of the results
Below, we will have a closer look at some of these stages.
Specification of the Growth System in the Graphical User Interface
The Basic CGSim has a convenient tool for geometry specification. Any
geometry can be constructed by creating and manipulating geometric
entities, such as, points, lines, curves, etc. To facilitate the geometry
creation, the toolbox contains extensive set of tools for selecting,
moving, splitting, connecting, and duplicating objects as well as tools
for creating splines, polylines, and perpendiculars. If any modifications
are introduced into the complex multiblock geometry, the user only needs
to regenerate the grid and specify the materials in those blocks that were
modified, while the rest of the setup stays intact.
Advanced users familiar with AutoCAD can use it as an alternative geometry
specification tool and then import the geometry into CGSim using the DXF
The CGSim code is a software designed specially for 2D axisymmetrical
computations, so the user only needs to create a half of the reactor
The built-in geometry analyzer automatically recognizes closed contours as
blocks, which substantially facilitates the geometry pre-treatment. This
feature is also very useful as a diagnostics tool—if some area of the
geometry, that stands for a separate construction element or a closed gas
volume is not recognized as a block, it means that the contour representing
its boundary is not closed. At the next step, the user can quickly generate a
grid for the whole system using the auto grid generator. Since the automatic
grid generator is very robust, the user only needs to set a parameter
characterizing desired grid refinement to start the grid generation. GUI also
provides the user with several options, facilitating the choice of blocks and
grid types for the automatic grid generation. For instance, the user can
choose the grid of some type to be generated in gas or solid blocks only.
Examples of grids generated by Basic CGSim
Advanced users can customize the mesh manually in selected blocks or
throughout the whole system. The grid generator supports triangular and
quadrangular grids with both matched and mismatched interfaces. These
capabilities are especially important for modeling of the crystallization
front geometry, when structured grids are required on both sides of the
interface. Local refinement of structured grids can be achieved through
refining the node distribution on the respective edges towards one of the
ends or symmetrically. For unstructured grids, refinement can also be
regulated through the grid quality parameters.
Assigning the Material Properties in GUI
The CGSim tool for setting characteristics of materials gives the user
wide possibilities. One can choose a constant, a polynomial function, a
piecewise linear function, expression, or an arbitrary function, which can be
programmed in the Function window. Plots for all characteristics can be
displayed in the same window. For example, the heat conductivity can be
defined as a function of temperature and coordinates in an arbitrary way
borrowed from literature. Incorporated programming language similar to
Pascal, extended by preprocessor and visualization of the function, allows
this for user.
After the geometry creation and the material specification, Basic CGSim
calculates the crystal and melt weights, and the initial charge weight,
which helps the user to draw crystallization zone geometry. Beside the
global heat computations with the given heater powers, Basic CGSim allows
searching the powers providing a certain crystallization rate and
prediction of crystallization front geometry.
The code permits automatic reconstruction of the geometry for several
crystal positions. To make it, the user has to build only the geometry with
the highest crystal position and to specify the crystal heights to be
1D and 2D Visualization with CGSim View
CGSim View allows analysis of 2D and 1D distributions including heat and
mass fluxes, V/G ratio and temperature gradient along the crystallization
front. Additionally, 1D distributions along a boundary can be displayed as a
plot and stored in a file on a hard disk. Built-in animation tools help to
analyze features of 3D melt convection.
The present version of basic CGSim operates under Windows 2000 and Windows XP.
The solver of Flow Module is available for parallel computations under Linux.
Demo version and code documentation are available upon request.