chlorite and the like hydrogen peroxide also is a useful oxidizing agent the oxidizing agent oxidizes the surface of the metal circuit so that the metal is readily removed in the polishing process the inhibitor is a polyalkyleneimine having a weight average molecular weight of about 1 000 1 000 000 preferably polyethyleneimine is used the inhibitor forms an inhibitor layer or a passivation layer on a metal substrate being polished such a aluminum and protects the substrate from dissolution during polishing and reducing dishing of the substrate depending on the ph of the polishing composition the inhibitor layer can be a layer of aluminum oxide or a layer of an aluminum inhibitor polymeric film at ph 4 9 the inhibitor layer is mainly aluminum oxide when the ph is less than 2 or higher than 9 this inhibitor layer is an aluminum inhibitor polymeric film the inhibitor layer is formed by the adsorption of inhibitor onto the aluminum surface through chemical bonding when an organic inhibitor is used such as polyethyleneimine a polymeric inhibitor layer is formed and the thickness of the layer is built up by hydrogen bonding the inhibitor layer can only be removed by mechanical abrasion and the removal rate of material during polishing is very low which results in a low level of dishing of the aluminum similar results occur when polishing titanium and titanium nitride since the surface of these compounds mainly is titanium oxide a ph buffer is used to keep the polishing composition at a ph of 2 11 preferably in the range of 4 9 typical compounds that can be used are ammonium phosphate ammonium hydrogen phosphate potassium carbonate ammonium tetraborate and potassium tetraborate about 0 0001 10 by weight based on the weight.