Supercritical CO₂ Won't Go Without Recycling
Laura Peters -- Semiconductor International, 7/1/2004
Supercritical carbon dioxide (SCCO2) is being heralded as a savior to cleaning porous low-k dielectrics. Amazingly, SCCO2 has even shown that it can restore low-k films that have been damaged through etching and ashing processes, converting SiOCH to SiOCH3 bonds. But the technology is lacking a strong infrastructure and a plan for recycling.
According to a prominent gas distribution system supplier, only about five wafers (300 mm) can be processed using a cylinder of CO2. Since CO2 is linked to global warming, its use in high volumes must be associated with a strong, well-planned recycling strategy.
Depending on the material, different additives can be used with SCCO2 to remove various residues. One of the trickier challenges with recycling the CO2 may be separating it from the additives that have been dissolved in the CO2 during processing. Whether that additive is HMDS or HFAC (hexafluoroacetylacetone, to remove copper residues), some users may want to see it recycled as well.
