Method for manufacturing element substrate, element substrate, and liquid ejection head

A method for manufacturing an element substrate for use in a liquid ejection head for ejecting a liquid to a recording medium, the element substrate comprising:

• a substrate having a nozzle including an ejection port opposed to the recording medium, and a pressure generating chamber communicating with the nozzle, and subjected to a liquid repellent treatment on a part of an ejection port surface including the ejection port formed therein;
• and
• a generating element for generating an energy for ejecting the liquid in the pressure generating chamber from the ejection port,
• the method comprising:
• a liquid repellent treatment step of performing the liquid repellent treatment on the substrate;
• a liquid repellent region removing step of removing a part of a liquid repellent region which is subjected to the liquid repellent treatment such that a non-liquid repellent region which is not subjected to the liquid repellent treatment is exposed at a surface of the substrate opposed to the recording medium;
• before the liquid repellent treatment step, a mask joining step of joining a hard mask to the ejection port surface of the substrate;
• and
• a mask portion removing step of removing a portion of the hard mask opposed to the nozzle,
• wherein the hard mask has an opposed portion opposed to the pressure generating chamber, and a joint portion protruding toward a substrate side with respect to the opposed portion, and jointed with the substrate, and
• wherein the joint portion is provided at a position not overlapping the pressure generating chamber as seen from a direction perpendicular to the ejection port surface.