AVS 50th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS2-ThM

Paper PS2-ThM3
Etching Mechanisms of Methylsilsesquioxane Low-k Material in High Density Fluorocarbon Plasma

Thursday, November 6, 2003, 9:00 am, Room 315

Session: Low k Dielectric Etch
Presenter: D. Eon, CNRS, University of Nantes, France
Authors: D. Eon, CNRS, University of Nantes, France
V. Raballand, CNRS, University of Nantes, France
G. Cartry, CNRS, University of Nantes, France
M.C. Peignon-Fernandez, CNRS, University of Nantes, France
C. Cardinaud, CNRS, University of Nantes, France
Correspondent: Click to Email
At present, performances in integrated circuit (IC) are limited by interconnection delay, which increases with the reduction of feature size (below 100 nm). One solution to reduce interconnection delay, is to diminish the parasitic capacitance between levels by replacing SiO@sub 2@ (k=4.5) conventional interlevel dielectric by a low dielectric constant material (low-k). The integration of these into IC fabrication requires i) that a selective etching is achievable with respect to the mask and bottom layer ii) that the etching does not adversely affect the permittivity of the film. This study concerns the etching of the methylsilsesquioxane based materials (SiOC k=2.9, SiOC with 40% of porosity k=2.2) and compared to SiC etch stop layer (k=4.5), with the aim to investigate etch mechanisms. We used a 13.56 MHz Inductively Coupled Plasma source mounted above a diffusion chamber where the substrate is biased separately. Etch rates are measured in real time by in-situ multi-wavelength ellipsometry. Surface composition is analysed by quasi in-situ XPS. Langmuir probe is used in order to determine plasma densities, ion flux, and electronic distribution. Mass spectrometer and optical emission spectroscopy measurements are carried out to obtain chemical composition of the plasma. Etching has been performed in C@sub 2@F@sub 6@ in mixture with H@sub 2@, Ar, N@sub 2@, or O@sub 2@. According to these results, we studied thoroughly the mixture C@sub 2@F@sub 6@/H@sub 2@ (25%/75%), which gives the best compromise between selectivity and etch rate. For all materials and conditions, the etch rate and the atomic F concentration are strongly correlated. On another hand, XPS shows that CF@sub x@ species, when present, play an important role on the etching mechanism of SiC and SiOC. Conclusion is that selective etching requires to control precisely the formation of the passivation layer.