Sputtering target

A method for manufacturing an Al interconnection having a dual damascene structure, comprising:

• processing chemically a niobium oxide containing concentrate of which a Ta content is 3000 ppm or less to obtain a high purity niobium oxide,
• reducing the high purity niobium oxide by a thermite reduction method due to Al to obtain a Nb raw material,
• melting the Nb raw material at least two times by an electron beam melting to obtain a Nb ingot containing Ta in a range of 550 to 1000 ppm and oxygen in a range of 10 to 100 ppm as impurities;
• plastic working the Nb ingot at a working rate in a range of 55 to 95% so as to disperse the Ta and the oxygen in the Nb ingot uniformly, to obtain a Nb plate in which a dispersion of the Ta content is within 15% and a dispersion of the oxygen content is within 30%,
• recrystallizing the Nb plate by heat-treating at a temperature in a range of from 800 to 1300° C. for one hour or more, to obtain the Nb plate including Nb grains having an average grain diameter in a range of from 10 to 75 μm, wherein each of the Nb grains has a grain diameter in a range of 0.1 to 10 times the average grain diameter, and a grain size ratio of adjacent grains in the Nb grains is in a range of 0.5 to 1.5;
• machining the recrystallized Nb plate into a desired shape;
• bonding the machined Nb plate with a backing plate made of Al or an Al alloy by hot-pressing at a temperature in a range of 400 to 600° C. while maintaining the average grain diameter of the Nb grains in the Nb plate, to prepare a Nb sputtering target;
• preparing an insulating film having a trench;
• forming a Nb liner film in the trench by sputtering the Nb sputtering target;
• and
• forming an Al interconnection film on the Nb liner film, wherein the Al interconnection film is composed of Al or Al alloy, and a resistivity of the Al interconnection film is 4 μΩcm or less.