Selective Etching of Heavily-Boron-Doped Si Substrate Using Lightly-Boron-Doped Si Epi as an Etch Stop Layer

A sample preparation technique for flip chips (FC) deprocessing from the back side proposed. The technique uses HNA chemistry (consisting of a mixture of acids: hydrofluoric, nitric and acetic) to wet-etch the heavily-boron-doped Si bulk substrate selectively to the lightly-boron-doped Si epi. The procedure can be used as a FC device sample preparation technique for back-side optical probing and FIB editing.