US Patent 11788007 Method for removing hard masks

Provided are compositions and methods useful in etching, i.e., removing amorphous carbon hard masks which have been doped with elements such as boron, chlorine, or nitrogen. The compositions utilize concentrated sulfuric acid, water, and at least one oxidizing agent. In the operation of the method, the composition selectively removes the doped hard mask layer, even in the presence of layers such as silicon dioxide, silicon nitride, tantalum nitride, and polysilicon, with good selectivity.