Wafer stage for holding a wafer in a plasma chamber

摘要

A wafer stage 10 comprises an electrode (not shown) and a dielectric plate 13 to hold a semiconductor wafer during processing in a plasma chamber. An outer ring 17 is provided around the periphery of the wafer stage. The outer ring has a magnetic material 25 on its lower surface and is fixed to the wafer stage 10 by magnets 24. The magnets 24 hold the outer ring 17 in place and also allow good thermal conductivity between plate 13 and ring 17. The temperature of the wafer held on the stage is therefore kept uniform between inner and outer portions. The magnets 24 may be arranged as a plurality of individual magnets with alternating polarity or as two concentric magnetic rings (fig 4, not shown).