Abstract
Claw-type dry pumps and rotary vane vacuum pumps have already been evaluated in the etching of AlSi1 using chlorine and a boron trichloride mixture. Both pumps had to sublimate AlCl 3 as well as to transport such gaseous corrosives as BCl 3 and Cl 2. In rotary vane pumps, most of the AlCl 3 is trapped in the lubricant and must be removed by suitable oil filtration devices. The increasing deterioration of the expensive PFPE lubricant, corresponding to a step-by-step increase in the ultimate pressure, was traced by IR analysis. After 10,000 wafer etchings, the oil filter had to be changed; after 30,000 wafer etching processes, extensive maintenance became necessary. Providing the claw type pump is used in the correct operating mode, AlCl 3 is transported completely through the pump without any problem. Some 100,000 wafers were etched and about 4 kg of AlCl 3 were transported without any maintenance at all. After disassembling, the pump was found to be in perfect condition.
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