| dc.description.abstract | Semiconductor and TFT-LCD processes use a significant amount of special gases. Most of these special gases are halogenated acid gases, e.g., Cl2, HCl, ClF3, and HBr, etc… The special gases are toxic to human and cause corrosion on pipes and process tools. Major treatment processes for those gases are wet scrubbing, burn + wet scrubbing and dry scrubbing processes. However, some gases have low solubility in water and burn process could cause fire hazard and consume significant energy. Semiconductor Industry Association recommends the dry local scrubber for CVD cleaning and etching as well as ion implantation. The objective of this study was to investigate the treatment ability of toxic gases from semiconductor processes by dry local scrubbers. Low pressure chemical vapor deposition process (LPCVD) was the primary target of this study and the ClF3 is used as the cleaning gas for wafer.
Three dry local scrubbers were studied, including the regular activated carbon, activated carbon coated with NaOH and CaOH, and FeOOH catalyst. A FTIR was used to detect the target gas and byproducts from the LPCVD process as well as the byproducts after the dry local scrubbers. Results showed that the major gases from the LPCVD process are SiF4, HCl, HF and CO. ClF3 was consumed during the process. Those gases were removed by the three types of dry scrubbers with efficiency higher than 99%. However, CFCs (chlorination fluorinated carbons) and methanol were detected in the effluent gases of the two activated carbons of local scrubbers, but negligible for FeOOH. Cost comparison of the three dry scrubbers showed the waste treatment cost are major problems for the dry scrubbers. The FeOOH can be recycled locally and therefore, the operation cost of the FeOOH was lowest.
Based on these observation, it were concluded the dry local scrubbers are high efficiency, and have low maintenance, no wastewater and toxic gases and low risk on fire hazard on special gas treatment. However, the activated carbon type of local scrubber can produce significant amount of by-products and waste treatment is major problem. The FeOOH type local scrubber can overcome those problems. | en_US |