Removing selected areas of material from a wafer involves the use of many different types of acid, base and caustic solutions. Because of the dangerous nature of these HPM's, personnel safety is a primary concern.

Much of the work with chemicals takes place at large wet benches where special solutions are prepared for specific tasks. For instance, a BOE, or buffered oxide etch, prepared from hydrofluoric acid buffered with ammonium fluoride is used to remove silicon dioxide without etching away an underlying silicon or polysilicon layer. Phosphoric acid is used to etch silicon nitride layers, nitric acid is used to etch metals and sulfuric acid is used to remove photoresist.

Many fabs today use automated equipment to perform acid and caustic etch processes. In addition to improving personnel safety, the automation offers the added benefits of precise immersion timing and wafer protection from human handling.