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