Metal Hardmask Etch Residue Removal For Advanced Copper / Low-k Devices

Abstract

Plasma dry etching processes are commonly used to fabricate vertical sidewall trenches and vias for copper (Cu) / lowk dual damascene devices. Small amounts of polymer are intentionally left on the sidewalls of trenches and vias during the dry etching process in order to achieve a vertical profile and to protect the low-k materials under the etching mask. Other particulate etch residues (such as mixtures of copper oxide (Cu x O y ) with polymers) can be seen in the bottom of the vias. As technology nodes advance to 45nm and beyond, IC companies are investigating the use of a metal hardmask such as TiN in order to gain better etching selectivity to the low-k materials during the dry etching process. In order to obtain reliable, low-resistance interconnects that can be used to manufacture advanced IC devices, the polymers on the sidewalls and the particulate residues at the via bottoms must be removed prior to the next process step. In this paper we report a recently developed wet cleaning approach to remove the metal hardmask etch residues while maintaining high selectivity to the copper and low-k film(s). This was demonstrated at the 45nm technology node for porous low-k, as well as 65nm for non-porous low-k materials through controlled modification of the formulations. The cleaning mechanism of the etch residues is discussed.

Effects of Postetching Treatment on Molecular-Pore-Stacking/Cu Interconnects for 28 nm Node and Beyond

“…The issues of concern in dual-damascene integration of porous SiOCHs are: (1) the degradation of interconnect characteristics caused by dry etching, ashing, and wet cleaning, [16][17][18][19][20][21][22] (2) the degradation of trench shape by the barrier/seed sputtering process, i.e., resputtering, 23,24) (3) residues at the bottom of the via holes owing to the formation of large amounts of by-products during the dryetching process that are too hard to remove by wet cleaning, [16][17][18][19][20][21][22] and ( 4) film delamination due to the fragile, porous, low-k structure. 1,2) To solve these problems, postetching treatments using H 2 , N 2 , and CH 4 have been studied for the metal hard mask trench-first dual-damascene (D/D) process using porous SiCOH.…”