Patent ID: 8691101

Claim:
A method for manufacturing an ejection element substrate which is provided with a flow-channel-forming member having an ejection orifice for ejecting a liquid and a liquid flow channel that is communicated with the ejection orifice, and a substrate having a supply port for supplying the liquid to the liquid flow channel, and which has a filter structure formed in a bottom of the supply port, comprising the steps of: (1) forming the supply port by forming a through-hole from a second face of the substrate on the side opposite to a first face of the substrate on which the flow-channel-forming member is disposed; (2) providing a resinous protection film on a side face and the bottom of the supply port, the bottom being an end adjacent to the flow-channel-forming member; and (3) forming an opening in the resinous protection film on the bottom of the supply port by carrying out a laser processing from the side of the second face, wherein in the step (1), the substrate has a surface layer on the first face and the substrate is removed from the second face until the surface layer is reached, in the step (2), the resinous protection film is provided on the side face of the supply port and on the surface layer which is exposed at the bottom of the supply port, and wherein the surface layer is in the form of a shape for defining the liquid flow channel, and is formed of a dissolvable material.