Paper PS-MoM5
New Fluorocarbon Free Chemistry Proposed As Solution to Limit Porous SiOCH Film Modification during Etching

Monday, October 28, 2013, 9:40 am, Room 104 C

Today etching processes involved during the porous SiOCH (p-SiOCH) integration combined with a metallic hard mask (MHM) generate serious issues such as film damage, residue growth, bottom line roughness. The last critical issue we are facing today is that the wet cleaning (HF based chemistry) is not efficient enough to remove all the fluorocabon layer formed on sidewall during etching. Fluorine is remaining on sidewall after wet cleaning. This Fluorine is encapsulated during the metal barrier deposition (prior to copper deposition) and can lead to reliability degradation of the p-SiOCH film. Today there is no solution to this problem except the use of aggressive wet cleaning, inducing in this case important CD loss. In this context we developed a new fluorocarbon (FC) free chemistry solving these issues.

In this work, p-SiOCH (deposited by PECVD, composition: Si 28%, O 29%, C 43%, k= 2.5, porosity <30 %) film modification has been studied using patterned and floating coupons (deposit/film modification formed on the floating sample gives a rough estimation of passivation layer formed on the sidewalls) and characterized by ellipsometry porosimetry (EP), infrared spectroscopy in attenuated total reflection configuration (ATR), X-ray photoelectron spectroscopy (XPS) and dielectric constant measurement comparing the new FC free chemistry to conventional FC (CF4/C4F8/N2/Ar) chemistry.

It will be demonstrated that the FC free etch chemistry presents a wide process window to adjust the taper profile by playing on plasma parameters with a hardly impact on p-SiOCH film modification (+4% k value increase compared to +16% with conventional FC chemistry, correlated with ATR analyses). The efficiency of wet cleaning to fully remove the passivation layer formed on sidewalls without degrading the profile will also be presented.