Papers by Author: Pi Chun Yu

Abstract: The borderless (BDL) vias landing on the metal lines were demanded in high-density flash memory devices due to the reduced die size, compared with non-borderless (NBDL) vias. IMD material recess in un-landed via dry etching and the Al-Cu metal line undercut caused by post-etch cleaning may lead to via resistance Rv high and EM reliability issue. In this work, the Al-Cu loss mechanism in BDL-via cleaning by using amine- and fluoride-based chemicals were studied in 58nm flash devices. We found that the Al-Cu undercut can be minimized in HDA containing solvent by controlling the formation of Al2O3/Al/HDA gel-like material to the less amounts; the shorter HDA processing time with sufficient IPA rinse generated the thinner gel-like layer leading to the less Al-Cu undercut in DIW rinse step. For TMAH/H2O2-containing semi-aqueous solution, the metal contained etched-residues can be removed by reaction of OH- with Al to form dissolved Al(OH)4-; addition of H2O2 will form a 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 DSP+ through the reaction with [F-] to form the DIW-dissolved AlFx by-products; while the dilute H2SO4 and H2O2 in DSP+ will oxidize Al to form Al2O3 that will be further etched by HF, the severe Al-Cu undercut was found in DSP+.

Abstract: In the conventional wet cleaning process of contact holes landing on the Si substrate and WSi metal gate, the ILD BPTEOS bowing and CD enlargement were often found by using dilute HF solution. With the device design rule decreasing, the CD size control and cleaning efficiency enhancement are highly demanded. In this work, the high aspect-ratio contact (AR~10) cleaning in single wafer (SW) tool was demonstrated in 58nm flash device. With the facilitation of nano-spray function to enhance particle removal efficiency (PRE), AM1 cleaning in SW tool can achieve the low contact resistance and tighten Rc distribution with less ILD film damage and lower CD enlargement. The parameter dependency of SW tool, including chemical injection method, nozzle swinging effect and nano-spray function, on contact resistance was also investigated. Compared to AM1 cleaning in bench tool, AM1 process in SW tool performs the larger process window for less ILD film damage at higher temperature and concentration.