Cryogenic Surface Cleaning
With the numerous problems associated with the wet cleaning (such as ineffectiveness for submicron
particles, environmental disposal regulation and etc.), the use of cryogenic aerosols has attracted considerable
attention. The use of CO2 dry ice and cryogenic argon aerosols surface cleaning procedure was described in the
references. In this approach a high speed jet of gas (CO2 or nitrogen) which contains cryogenic solid aerosols
(CO2 snow flakes or solid argon) is directed toward the surfaces which are to be cleaned or decontaminated. The
argon and the CO2 aerosols offer several advantages. In addition to being non-toxic, non-pollutant and
nonflammable, they are relatively inexpensive and simple to use. While the dry ice blasting has been used in
several areas (e.g., cleaning lenses and mirrors), its use in the microelectronic industries has been limited.
The cryogenic argon aerosol in nitrogen gas seems to be more effective, since it is possible to produce ultra-pure
argon. While most authors believes that the impact of solid CO2 or argon pellets on the particles causes them to be
removed, the exact mechanisms is not known. For example, the rapid evaporation of CO2 snow flakes or argon
aerosols when they reach the surface may contribute significantly to particle detachment.
We are working on an accurate model for predicting particle detachment rate (in the size range of 0.01 to 10
microns) under an argon or CO2 snow flake jet. The mechanisms of argon/CO2 pellets impact and/or rapid evaporation
removal will be carefully analyzed and the effectiveness of oscillating cryogenic jets for detaching deposited particle
will be studied. Numerical simulation and experimental techniques will be used for this purpose. A laboratory-scale
cryogenic argon/CO2 oscillating jet experimental cleaning device is also being used to test the critical cleaning performance.
Funded by NANO-CLEAN