Method of etching magnetoresistive film by using a plurality of metal hard masks

A method of etching a magnetoresistive film, the method comprising the steps of:

• (a) preparing a substrate having the magnetoresistive film to form first and second hard masks made of materials different from each other successively on the magnetoresistive film;
• (b) forming, on the second hard mask, a first resist that has an opening, and forming, on the first resist, a second resist that has first and second openings separated from each other, wherein
• the first and second openings of the second resist overlap the opening of the first resist, and
• an area between the first and the second openings of the second resist forms a bridge part, and a space is interposed between the bridge part and the second hard mask;
• (c) a first etching step of etching a surface of the second hard mask, wherein the second hard mask is subjected to dry-etching and the bridge part of the second resist is used as a mask during dry-etching, the dry-etching being performed by irradiating the second hard mask with an ion beam while rotating the substrate, wherein an incident angle α of the ion beam is greater than 0° and is not more than 70°;
• (d) a second etching step of etching a surface of the first hard mask by using the second hard mask patterned by etching, wherein the second etching step is reactive ion etching and the reactive ion etching differs from the first etching step, and
• (e) a third etching step of etching a surface of the magnetoresistive film by using the first hard mask patterned by at least the second etching step, wherein the third etching step includes dry etching or reactive ion etching;
• wherein the first hard mask has a thickness of 50 nm or less;
• wherein the first hard mask contains at least one species selected from the metal group consisting of Ta, Ti, and W;
• and
• wherein the second hard mask contains at least one species selected from the metal group consisting of Ni, Co, Fe, and Cu.