Contact resistance improvement by wet cleaning for Al/Cu metal

• Main Authors: Lee, Ming-Hsiu, 李明修
• Other Authors: Pan, Fu-Ming
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/63613582484772866905

碩士 === 國立交通大學 === 工學院碩士在職專班半導體材料與製程設備組 === 98 === Borderless (BDL) vias landing on metal lines were demanded in high-density flash memory devices due to the reduced die size, internal dielectric (IMD) material recess in un-landed via dry etching and the Al-Cu metal line undercut caused by post-etch cleaning may lead to a high via resistance (Rv) and the EM reliability issue〔1〕. In this work, the Al-Cu loss mechanism in BDL-via cleaning by using amine- and fluoride-based chemicals was studied for 58 nm flash devices. We found that the Al-Cu undercut can be alleviated in heptadecylamine containing solvent by minimizing the formation of Al2O3/Al/HDA gel-like material; the shorter heptadecylamine processing time with sufficient IPA rinses generated a thinner gel-like layer, leading to a small Al-Cu undercut in the deionizer water rinse step. For Tetra Methyl Ammonium Hydroxide/H2O2-containing semi-aqueous solution, metal contained etched-residues can be removed by reaction of OH- with Al to form dissolved Al(OH)4-; addition of H2O2 will form an oxidized passivation layer on the metal surface to prevent from metal corrosion. On the other hand, the Al/Al2O3 contained polymer was removed by fluoride-based solvent or Dilution Sulfuric acid with Hydrogen peroxide and 100ppm of Hydrofluoric acid through the reaction with F- to form deionizer water dissolved AlFx byproducts; while H2SO4 and H2O2 in DSP+ will oxidize Al to form Al2O3, that will be further etched by HF, resulting in a severe Al-Cu undercut.