AVS 53rd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS1-MoM

Paper PS1-MoM10
Material Modifications and Surface Roughness during Porous SiOCH Etching Processes

Monday, November 13, 2006, 11:00 am, Room 2009

Session: Etch for Advanced Interconnect I
Presenter: F. Bailly, CNRS-IMN-France
Authors: F. Bailly, CNRS-IMN-France
T. David, CEA-LETI-France
A. Jacquier, STM-France
M. Darnon, CNRS-LTM-France
C. Cardinaud, CNRS-IMN-France
Correspondent: Click to Email
With dimensions shrinkage, chip performances limitations are mainly due to interconnect RC delay time. Introducing porosity into dielectrics, leading to ultra low-k materials, is one of the emerging solutions. Integrating such porous materials requires complex dual damascene architectures: new steps and additional layers (etch stop ...) have been added and increase the effective capacitance of the structure. Efforts have to be done to reduce the effect of these layers. Thus, the trench bottom etch stop layer used in the dual damascene architecture has to be removed, complicating the control of the end of the trench etch. Furthermore, stopping the etch process directly on the porous material is likely to cause integration issues such as material modifications and roughness of the trench bottom. As a basic study, we simulate the influence of etch plasmas on trench bottom. We propose to characterize material modifications and roughness induced by the etch plasmas on blanket wafers coated with porous SiOCH (20% of porosity). These plasmas are performed in a capacitive discharge reactor. The feed gases are chosen to be representative of the different components of a typical low-k etch process (CF@sub 4@; Ar = role of bombardment; SF@sub 6@ = role of fluorine; CF@sub 4@/Ar/CH@sub 2@F@sub 2@ = effect of a polymerizing gas addition; CF@sub 4@/Ar/N@sub 2@; ...). The roughness is measured by AFM and is correlated with surface analyses (XPS and XRR) to point out any relations between etch mechanisms and the resulting roughness. Results highlight that the addition of O@sub 2@ or N@sub 2@ among the feed gases (CF@sub 4@ and Ar) leads to roughness increase. On the contrary, when adding a polymerizing gas, smoother surfaces are observed thanks to a protective fluorocarboned overlayer. The material modification is investigated by Infrared Spectroscopy: the results show that the remaining porous SiOCH is slightly modified in terms of CH@sub 3@ consumption and water uptake.