Method for forming metal line of semiconductor device

A method comprising:

• forming an interlayer dielectric over a semiconductor substrate
• forming a trench in the interlayer dielectric layer by etching the interlayer dielectric;
• performing a first cleaning process to remove residues in the trench after forming the trench;
• and then
• performing a second cleaning process to remove residues in the trench after performing the first cleaning process.

A method comprising:

• forming an interlayer dielectric over a semiconductor substrate
• forming a trench in the interlayer dielectric layer by etching the interlayer dielectric;
• performing a first cleaning process to remove residues in the trench after forming the trench;
• performing a second cleaning process to remove residues in the trench after performing the first cleaning process;
• forming a via hole by etching the interlayer dielectric using the second photoresist pattern;
• performing a third cleaning process to remove residues in the via hole after forming the via hole;
• forming a diffusion barrier over the trench and the via hole;
• and then
• forming a metal line in the trench and the via hole and over the diffusion barrier.