AVS 45th International Symposium
    Plasma Science and Technology Division Thursday Sessions
       Session PS-ThM

Paper PS-ThM3
Low k Dielectric Etching in High Density Plasmas

Thursday, November 5, 1998, 9:00 am, Room 318/319/320

Session: Plasma Applications in Copper Metallization
Presenter: O. Joubert, France Telecom CNET/DTM/TFM
Authors: O. Joubert, France Telecom CNET/DTM/TFM
L. Vallier, France Telecom CNET
P. Czuprynski, France Telecom CNET
Correspondent: Click to Email
Dielectric etching remains one of the most challenging etching process for ultra large scale integration (ULSI) technology. The need to move to the so-called low k dielectric materials open a all new area of investigation. Among different options, one is to use polymers as low k dielectric. Opening high aspect ratio contact holes in polymer type materials can be as challenging as opening high aspect ratio contact holes in SiO@sub 2@. In this paper we have been studying the etching of high aspect ratio contact holes (higher than 5) in polymers. Studies were performed in a high density helicon source using various chemistries and plasma operating conditions. The etching was controlled using real time ellipsometry and optical emission techniques. First, oxygen plasmas were tentatively used to open high aspect ration contact holes. In all the plasma operating conditions used (low density and high density regimes and always at very high chuck bias power), undercut due to spontaneous etching reactions between the polymer and oxygen atoms present in the discharge or profile deformation such as bowing were observed. Other chemistries such as H@sub 2@/N@sub 2@ gas mixtures where spontaneous etching reactions between the polymer and reactive species are less important were also investigated. Oxygen based chemistries such as O@sub 2@/CO, O@sub 2@/CH@sub 4@, O@sub 2@/SO@sub 2@ allowing passivation layers to be formed on the polymer sidewalls of the contact were investigated. The best contact hole profiles were obtained using O@sub 2@/SO@sub 2@ gas mixtures where sulfur deposition on the polymer sidewalls strongly minimizes spontaneous etching reactions. On the other hand, some sulfur-based species are left behind which can react with air moisture possibly inducing metal corrosion during the subsequent interconnect formation. In situ anticorrosion treatments were performed to remove sulfur based species. The anticorrosion efficiency was evaluated by measuring the sulfur concentration on all the contact hole surfaces before and after anticorrosion treatment using chemical topography analyses by x ray photoelectron spectroscopy (XPS). @FootnoteText@ This work has been carried out within the GRESSI consortium between CEA-LETI and France Telecom-CNET.