| AVS 61st International Symposium & Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS-MoM |
| Session: | Current Challenges of Plasma Etching Technologies |
| Presenter: | Jean-Francois de Marneffe, IMEC, Belgium |
| Authors: | L. Zhang, IMEC, KU Leuven, Belgium J.-F. de Marneffe, IMEC, Belgium M. Lukaszewicz, Wroclaw University of Technology, Poland S. Barry-Porter, Trinity College Dublin, Ireland F. Vajda, Trinity College Dublin, Ireland Y. Sun, IMEC, Belgium M.H. Heyne, IMEC, KU Leuven, Belgium M. Baklanov, IMEC, Belgium |
| Correspondent: | Click to Email |
Porous organo-Silicon glass thin films, with porosities ranging from 8 to 48% and k-values from 2.7 to 1.9 were exposed to 147nm photons and ions emitted in a CCP discharge of Xe. The material changes have been measured by means of various surface and bulk analytical techniques. For high-porosity/low k-value, a strong Si-CH3 depletion is observed, concomitant with moisture and increase of silanol group density. Surface densification occurs, as well as reduction of porosity. TOF-SIMS elemental profile indicate however that C and O profiles stay rather constant through the film thickness, only slightly changing in absolute value. Change of material properties are reflected in a rapid increase of the bulk dielectric constant. It is observed that 147nm VUV photons dissociate Si-C bonds, releasing -CH3 and other H-based radicals in the porous matrix, reacting with dangling Si* and forming Si-H. It is shown that Si-H bonds are also dissociated by VUV but their loss is compensated until -CH3 are completely dissociated. In absence of reactant to form volatile compound with, a major part of those radicals form complex polymers that condensate into the pores, while, upon ambient exposure, moisture react with remaining Si- dangling bonds forming highly polarizable silanol groups. The impact of VUV exposure on low-k dielectrics with varying porosities indicate a direct correlation between absolute Si-CH3 loss and VUV dose, independent of inital methyl bond density. Change in dielectric properties (k-value) follows the same trend, showing, at fixed VUV dose, a dielectric shift Δk = 1.0 independent of the pristine k-value.
The observed trend suggest that, besides reactive radical diffusion, photons emitted during plasma processing do severely impede dielectric properties, and therefore need to be tackled appropriately during patterning and integration.In order to reduce the impact of VUV, hardmasks with high photon absorption and the effect of polymer filling by the P4 or ‘pore stuffing’ approach were evaluated. Several mask materials were deposited on top of blanket OSG 2.0 low-k films and exposed to 147nm photons. Various polymers with different UV absorption properties were stuffed into porous OSG 2.0 low-k films and then exposed to 147nm photons. For both cases, low-k damage was evaluated and showed reduced VUV damage.