Described herein is a monolithic printhead formed using integrated circuit techniques. Thin film layers, including ink ejection elements, are formed on a top surface of a silicon substrate. The various layers are etched to provide conductive leads to the ink ejection elements. At least one ink feed hole is formed through the thin film layers for each ink ejection chamber. A trench is etched in the bottom surface of the substrate so that ink can flow into the trench and into each ink ejection chamber through the ink feed holes formed in the thin film layers. An orifice layer is formed on the top surface of the thin film layers to define the nozzles and ink ejection chambers. A phosphosilicate glass (PSG) layer, providing an insulation layer beneath the resistive layers, is etched back from the ink feed holes and is protected by a passivation layer to prevent the ink from interacting with the PSG layer. Other layers may also be protected from the ink by being etched back.