A suitable vacuum pump system used in plasma or RIE‐mode dry etching of Al and Al alloys with CCl4/Cl2 enables to operate without LN2 cold traps. A Roots pump plus rotary vane pump combination, both using inert fluid lubricant, pumps and exhausts all occurring volatile products. Condensing solid AlCl3 is quantitatively removed from the backing pump sealing fluid by means of a high speed, main stream oil purification system via an Al2O3 deep bed filter. Maintenance of the pump system is limited to just changing the Al2O3 filter elements, each time after etching of 4000 4 in. wafers. No decomposition of the sealing fluid could be observed. Any fluid remaining when exchanging the filter elements can practically be recovered by centrifuging.

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