In this paper, a very simple model of notching effect is reported. From an engineering point of view, the notching effect is an undercut between bottom of metal strip and stop layer (generally oxide) which can be observed in a Cl/sub 2/-BCl/sub 3/ metal etch when the geometry is shrunk. Starting from (Horwitz, 1993), a very detailed relation between geometrical decreasing , ion beam isotropy increasing, and sheath voltage was proposed. Then, a set of experiments performed on patterned aluminum wafers etched in a transformed coupled plasma (TCP) reactor were carried out in order to support the model based on sheath field curvature around metal lines. The experimental results are in good agreement with the theoretical predictions. This confirms the reliability of model proposed in order to manage the engineering problems which take place when a scaling down is performed.