Method for forming contact opening

摘要

A method for forming a contact opening is described. A substrate formed with a semiconductor device thereon is provided, and then an etch stop layer, a dielectric layer and a patterned photoresist layer are formed sequentially over the substrate. The exposed dielectric layer and 20% to 90% of the thickness of the exposed etch stop layer are removed to form an opening. After the patterned photoresist layer is removed, an etch step using a reaction gas is conducted to remove the etch stop layer remaining at the bottom of the opening and form a contact opening that exposes a part of the device, wherein the reaction gas is selected from CF₄, CHF₃ and CH₂F₂. By using the method, a micro-masking effect is avoided, and oxidation at the bottom of the contact opening conventionally caused by the photoresist removal using oxygen plasma is also avoided.