Residue removal after via-hole etching

Using a combined microwave downstream plasma and low damage RIE, we have successfully developed a dry process that removes both the photoresist and the remaining polymer residue after a via etch step. An ion assisted plasma process containing oxygen and fluorine was successfully developed. It was found that the ion-assisted process converted the Ti, Si and their oxide containing residues to water-soluble compounds. Thus, a room temperature DI water rinse after the dry process removed the entire sidewall residue. The process is carried out at room temperature to avoid any undercutting of the TiN layer. SEM micrographs show that the via sidewall is free of any residue. The electrical data shows via resistance equal to or lower than samples cleaned with the standard process using oxygen plasma followed by a solvent clean. This process has been shown to be a reliable and cost-effective alternative to solvent based processing. Failure due to the narrow window of the solvent process is eliminated and equivalent or improved yield and device performance is obtained with the new process.