Critical point dryer

The Critical Point Dryer is used to dry samples without the damaging effect of surface tension.  The basic operation of the CPD is as follows:

1. Immerse sample in IPA in the chamber.
2. Cool the chamber with liquid CO₂.
3. Fill chamber with liquid CO₂.
4. Continually replace IPA/CO2 mixture with pure liquid CO₂.
5. Heat the chamber past the critical point of CO₂ (31 °C, 1072 psi).
6. Vent the gaseous CO₂.
7. Remove the sample.

An entire process run takes ~1 hour and samples up to 4" wafers can be used in the tool.