Home / Examples / Stress Analysis [Galileo] / Example 41: Stress of Substrate Coated with Thin Film
A SiGe substrate is coated with a thin Si film. The stresses are generated due to the mismatch of their lattices.
Lattice mismatch ratio = (Thin film's lattice constant - Substrate's lattice constant) / Substrate's lattice constant
When the ratio of -0.1%, the tensile stress generated in the Si layer is calculated.
The lattice constant of Si layer is smaller than that in SiGe layer. The lattice mismatch ratio is negative.
Unless specified in the list below, the default conditions will be applied.
Results will vary depending on Femtet version and the PC environment.
Item |
Settings |
Analysis Space |
3D |
Model Unit |
um |
The unit is [um] to cope with thin film.
Item |
Settings |
Solver |
Stress Analysis [Galileo] |
Analysis Type |
Static Analysis |
Options |
N/A |
The SiGe layer is a 0.1 um-thick solid body. The Si layer is a 0.01 um-thick solid body.
Body Number/Type |
Body Attribute Name |
Material Name |
0/Solid |
SiGeLayer |
301_Silicon(single-crystal) * |
1/Solid |
SiLayer |
301_Silicon(single-crystal) * |
* Available from the material DB
The initial strain (axial) is set to -0.001 on the Initial Strain tab of SiLayer. This is equivalent to -0.1% lattice mismatch.
SiLayer shrinks by 0.1% during the simulation.
Body Attribute Name |
Initial Strain |
SiLayer |
Axial strain/Isotropic/-0.001 |
The gradation contour diagram of maximum principal stress is shown below.
The substrate warps due to the lattice mismatch. The tensile stress is generated in the Si layer.
