Abstract
In latest integrated circuits' generation, lanthanum has been commonly introduced to cap hafnium based high k gate oxides. Indeed it enables strong threshold voltage modulation of the devices. Nonetheless its implementation is challenging, especially during the gate patterning, where hydrofluoric acid is used to remove the high k film on the active areas. On the one hand, lanthanum is highly corrodible. On the other hand, it easily generates non soluble salts. Lanthanum fluoride salts are among the most stable ones. Preventing their deposition is hereby discussed. Hydrochloric acid is one of the best solutions to solubilize lanthanum, before removing the high k with hydrofluoric acid.