AVS 53rd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA5
Patterning of Narrow SiOCH Trenches using the Late Porogen Removal Process

Tuesday, November 14, 2006, 3:20 pm, Room 2011

Session: Etch for Advanced Interconnect II
Presenter: T. Chevolleau, LTM-CNRS-France
Authors: T. Chevolleau, LTM-CNRS-France
D. Eon, CNRS-LTM-France
M. Darnon, CNRS-LTM-France
T. David, CEA-LETI-France
L. Vallier, CNRS-LTM-France
O. Joubert, CNRS-LTM-France
Correspondent: Click to Email
In CMOS technology, the dominant strategy to achieve future generation of ultra low-k interlayer dielectric materials with a dielectric constant close to 2.2 is to introduce porosity into a SiOCH matrix. However, porous materials are very sensitive to ash and etch plasma exposures and one of the integration challenges is to reduce the impact of these plasma processes on the low-k modification. To solve this issue, one of the emerging solutions is the late porogen removal process. In this approach, the porosity in SiOCH is generated by a sacrificial porogen (carbon based polymer) which is desorbed after patterning or copper filling. These hybrid materials are expected to behave like non-porous SiOCH materials during the etching processes. In this work, the etch mechanisms of the hybrid material and the patterning of narrow trenches down to 50 nm using a metallic hard mask are studied. The etching is performed in an industrial capacitively discharge reactor using a fluorocarbon-based plasma. A parametric study on blanket wafers shows that the etch mechanisms are similar to those of a dense SiOCH material. However, surface analyses by XPS reveal that the higher carbon content in the hybrid material induced by the presence of porogen leads to the formation of a thicker fluorocarbon overlayer than with typical dense SiOCH materials. Consequently, the etching is very sensitive to the addition of polymerizing gas which can potentially lead to etch stop phenomena. The patterning of narrow trenches in hybrid materials shows that etch profiles are similar than in dense SiOCH layers. The main issue is the profile distortion induced by etch products redeposition on the trench sidewalls. XPS analyses are also conducted on the bottom and sidewalls of the trenches using the chemical topography analysis technique. The selectivity to the underneath etch stop layer (SiC) remains low (of about 4) indicating that the use and the development of a specific over etch step is required.