Method for producing a silicon substrate and method for producing a liquid ejection head

A method for producing a liquid ejection head comprising:

• a silicon substrate comprising a silicon base material, and a wiring formation layer laminated on a base material surface of the silicon base material, and being provided with a wiring member, an electrode member comprising a noble metal, and a close contact member comprising a base metal between the wiring member and the electrode member;
• a liquid common flow channel and a liquid supply flow channel communicating with the liquid common flow channel, provided on the silicon substrate;
• and
• a flow channel member provided on the wiring formation layer, and comprising an ejection port ejecting a liquid, and communicating with the liquid supply flow channel and the ejection port,
• the method comprising:
• a step of forming a deposition film by a fluorocarbon gas, in etching of the silicon substrate;
• and
• a step of removing, by a removal solution, the deposition film formed by the fluorocarbon gas,
• wherein the removal solution comprises a primary amine and an organic polar solvent,
• wherein a content of the primary amine in the removal solution is 20 to 80 mass %,
• wherein a content of water in the removal solution is 10 mass % or lower, and
• wherein a content of tetramethylammonium hydroxide in the removal solution is 1 mass % or lower.