AVS 51st International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS1-MoM

Paper PS1-MoM9
Impact of Different Ashing Plasmas on Porous and Dense SiOCH

Monday, November 15, 2004, 11:00 am, Room 213A

Session: Low-k Dielectric Etching
Presenter: T. Chevolleau, LTM-CNRS, France
Authors: T. Chevolleau, LTM-CNRS, France
N. Posseme, STMicroelectronics, France
T. David, CNRS/LTM, France
O. Joubert, CNRS/LTM, France
O. Louveau, STMicroelectronics, France
D. Louis, CEA-LETI, France
Correspondent: Click to Email
In CMOS technology, the introduction of porosity into Low-k dielectric is the dominant strategy to achieve future generation of ultra low K interlayer dielectric materials (k~2.2). One of the integration challenges with these new materials are their structural modification during the etch and stripping processes due to a higher sensitivity with respect to the plasma . This study is dedicated to the impact of ash processes on a non porous SiOCH (k = 2.9) and a porous SiOCH (k=2.2, 50% void). The ash processes were carried out on blanket wafers either in a Magnetically Enhanced Reactive Ion Etcher using O@sub2@ and NH@sub3@ plasmas or in a photoresist stripper using H@sub2@ and O@sub2@ based downstream microwave plasmas. After plasma exposure, the surface and bulk modification of SiOCH films are investigated using quasi in-situ X-Ray Photoelectron Spectroscopy, Attenuated Total Reflection spectroscopy, Spectroscopic Ellipsometry and contact angle. The results show that the degree of SiOCH bulk modification is related to the carbon depletion and the moisture adsorption in the remaining film after plasma exposure. The materials are not altered in an H@sub2@ based plasmas without nitrogen whereas a film degradation is clearly pointed out in O@sub2@ based plasmas. When N@sub2@ is added to O@sub2@ or H@sub2@ plasmas, the porous film degradation is significantly enhanced. These results reveal that the best ash chemistries are H@sub2@/Ar and H@sub2@/He gas mixture. The P.R stripping feasibility on porous SiOCH films integrated in a single damascene structure is also performed and electrical results demonstrate that NH@sub3@ and H@sub2@/He ashing chemistries minimize the degradation of porous SiOCH compared to oxygen containing gas mixtures. Furthermore, Energy Filtred Transmission Electron Microscopy analyses reveal an efficient pore sealing with the NH@sub3@ chemistry leading to the elimination of TiN diffusion through the pores during barrier deposition.