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Volume reference temperature and initial intrinsic stress

Posted 2025/07/24 5:21 JST Heat Transfer, Structural Mechanics, Physics Interfaces Version 6.3 3 Replies

Ram P
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I am trying to model a film deposition process on a substrate where:

(1) the substrate is heated up from room temperature in such a way that surface temperature of the substrate is non-uniform. I can achieve this by using a spatially varying input heat flux and/or temperature boundary conditions etc... No issues here!

followed by

(2) a film of a different material is deposited on the surface such that the "Volume reference temperature" of different parts of the film matches the temperature of the substrate directly underneath the film. Would someone know how to do this? I do not know how to enter different volume reference temperatures for the substrate (which would be the room temperature) as well as the different parts of the film -- which would be the temperature of the substrate at the location directly underneath the film obtained from item #1 above.

and

(3) the film should have an intrinsic stress tensor that is spatially varying. This can be read from an external file. This intrinsic stress should be activated only when the film is deposited at the elevated temperature -- it cannot be present from the beginning. Would someone know how to do this?

followed by

(4) the whole substrate+film assembly cooled down to room temperature. This part is straightforward too.

Thank you for any pointers!

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3 Replies Last Post 2025/07/25 23:06 JST
Henrik Sönnerlind COMSOL Employee

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Posted: 1 day ago 2025/07/25 0:05 JST

For (2), you can change the volume reference temperature to User defined. As expression, you can use a withsol() operator to pick up results from a previous study. Combine that with a General Extrusion operator that maps the temperature from the surface of the substrate through the thickness of the deposited layer.

For (3), If you use an Activation node to make the film come alive, I don't think it will matter if the intrinsic stress is defined always. However, you can always multiply the intrinsic stress with a boolean like (t>1.3) to ensure that it is zero until it is needed.

However, the whole concept of combining an intrinsic stress with a deposition at a new reference temperature sound a bit odd to me. Would not the deposition result in a stress-free state at the deposition temperature?

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Henrik Sönnerlind
COMSOL
For (2), you can change the volume reference temperature to *User defined*. As expression, you can use a withsol() operator to pick up results from a previous study. Combine that with a General Extrusion operator that maps the temperature from the surface of the substrate through the thickness of the deposited layer. For (3), If you use an *Activation* node to make the film come alive, I don't think it will matter if the intrinsic stress is defined always. However, you can always multiply the intrinsic stress with a boolean like (t>1.3) to ensure that it is zero until it is needed. However, the whole concept of combining an intrinsic stress with a deposition at a new reference temperature sound a bit odd to me. Would not the deposition result in a stress-free state at the deposition temperature?
Ram P
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Posted: 1 day ago 2025/07/25 2:31 JST

Thank you. That gives me a pathway.

A follow up question for (2): The substrate still needs to have "Room Temperature" as the volume reference temperature. While I can use the withsol operator + general extrusion for the film, how can have the substrate still use the "Room Temperature" as the vol-ref-temp?

(3) I frankly do not understand this 100%. But, it seems like in addition to the thermal strain, process parameters induce intrinsic stress even at the deposition conditions.

Thank you. That gives me a pathway. A follow up question for (2): The substrate still needs to have "Room Temperature" as the volume reference temperature. While I can use the withsol operator + general extrusion for the film, how can have the substrate still use the "Room Temperature" as the vol-ref-temp? (3) I frankly do not understand this 100%. But, it seems like in addition to the thermal strain, process parameters induce intrinsic stress even at the deposition conditions.
Henrik Sönnerlind COMSOL Employee

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Posted: 9 hours ago 2025/07/25 23:06 JST

Use different features (and thus selections) for the thermal expansion of the substrate and the film. Then, you can easily define different reference temperatures.

If you want to use a single feature, you can instead assign the temperature as variable, and then define this variable differently in different domains.

-------------------
Henrik Sönnerlind
COMSOL
Use different features (and thus selections) for the thermal expansion of the substrate and the film. Then, you can easily define different reference temperatures. If you want to use a single feature, you can instead assign the temperature as variable, and then define this variable differently in different domains.

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