Specific Process Knowledge/Wafer and sample drying/Critical Point Dryer: Difference between revisions

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<!-- give the link to the equipment info page in LabManager: -->
<!-- give the link to the equipment info page in LabManager: -->
[http://labmanager.dtu.dk/function.php?module=Machine&view=view&page_id=169 Critical Point Dryer in LabManager]
[http://labmanager.dtu.dk/function.php?module=Machine&view=view&mach=254 Critical Point Dryer in LabManager]




In the critical point dryer, samples are dried in LCO<math>_2</math>. In the drying process, the sample is first put into Isopropanol for at least 1 hour, and loaded into the machine. When the machine is started (press "Fill"), the isopropanol is exchanged for liquid CO<math>_2</math>. When there is only CO<math>_2</math> in the machine, the pressure and temperature in the chamber is raised, above the so called “critical point”. In this way, there is never a liquid/gas interface, but instead the liquid is turned into a mixture of equal parts of gas and liquid. Because of this, the problem with surface tension, which destroys the fragile structures through capillary forces, is avoided.
In the critical point dryer, samples are dried in supercritical CO<math>_2</math>. In the drying process, the sample is first put into Isopropanol for at least 1 hour, and then loaded into the machine. When the machine is started, the isopropanol is exchanged for liquid CO<math>_2</math>. When there is only CO<math>_2</math> in the machine, the pressure and temperature in the chamber is raised, above the so called “critical point”. At this point, there is no longer a liquid/gas interfacen, but instead the CO<math>_2</math> is in a supercritical state. Because of this, the problem with surface tension, which destroys the fragile structures through capillary forces, is avoided.


==Equipment performance and process related parameters==
==Equipment performance and process related parameters==
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*Pieces (up to 10x10mm)   
*Pieces (up to 10x10mm)   
|-
|-
| style="background:LightGrey; color:black"|Substrate material allowed
| style="background:LightGrey; color:black"|Materials allowed
|style="background:WhiteSmoke; color:black"|
*Silicon wafers
*Quartz wafers
*Pyrex wafers
*InAlP
*GaAs
|-
| style="background:LightGrey; color:black"|Material allowed on the substrate
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Silicon oxide
*Please consult the [http://labmanager.dtu.dk/function.php?module=XcMachineaction&view=edit&MachID=254 Critical Point Dryer cross contamination sheet]
*Silicon nitride
*Poly Silicon
*SU-8
|-  
|-  
|}
|}
<!-- copyright issue rkc


==Comparison of samples dried in air and with Critical Point Dryer==
==Comparison of samples dried in air and with Critical Point Dryer==
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An acknowledgment goes to Tom Larsen, Nanoprobes, DTU Nanotech, who provided the pictures.
An acknowledgment goes to Tom Larsen, Nanoprobes, DTU Nanotech, who provided the pictures.
-->

Latest revision as of 11:57, 7 February 2023

Unless anything else is stated, everything on this page, text and pictures are made by DTU Nanolab.

All links to Kemibrug (SDS) and Labmanager Including APV and QC requires login.

Feedback to this page: click here


Critical Point Dryer

Critical point dryer: positioned in cleanroom D-3.

The critical point dryer is used to dry fragile structures that may be damaged in a normal drying procedure. Fragile structures can be thin membranes, or free hanging structures like cantilevers and grippers.


The user manual(s), technical information and contact information can be found in LabManager:

Critical Point Dryer in LabManager


In the critical point dryer, samples are dried in supercritical CO. In the drying process, the sample is first put into Isopropanol for at least 1 hour, and then loaded into the machine. When the machine is started, the isopropanol is exchanged for liquid CO. When there is only CO in the machine, the pressure and temperature in the chamber is raised, above the so called “critical point”. At this point, there is no longer a liquid/gas interfacen, but instead the CO is in a supercritical state. Because of this, the problem with surface tension, which destroys the fragile structures through capillary forces, is avoided.

Equipment performance and process related parameters

Purpose Drying of wafers or chips

To dry fragile structures (example membranes, grippers, cantilevers).

Process parameter range Process Temperature 0 oC to 45 oC
Process pressure

1 atm to (maximum) 95 atm (1400 PSI)

Substrates Batch size
  • 1 to 5 wafers per run. Sizes: 2”, 4" or 6" or
  • Pieces (up to 10x10mm)
Materials allowed


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