AVS 58th Annual International Symposium and Exhibition
    Plasma Science and Technology Division Thursday Sessions
       Session PS-ThP

Paper PS-ThP28
Study of Low-k Dielectric Damage in a Radial Line Slot Antenna (RLSA) Reactor

Thursday, November 3, 2011, 6:00 pm, Room East Exhibit Hall

Session: Plasma Science and Technology Poster Session
Presenter: Yoshio Susa, Tokyo Electron Technology Development Institute, INC.
Authors: Y. Susa, Tokyo Electron Technology Development Institute, INC.
R. Sundararajan, Tokyo Electron US Holdings Ltd.
J. Zhao, Tokyo Electron US Holdings Ltd.
L. Chen, Tokyo Electron US Holdings Ltd.
T. Nozawa, Tokyo Electron Technology Development Institute, INC.
J.A. Mucha, University of Houston
D.J. Economou, University of Houston
V.M. Donnelly, University of Houston
R. Wise, IBM Research
Correspondent: Click to Email
Low-k dielectrics are widely used as insulating materials in ULSI circuits. In BEOL processes, etching of low-k layers can cause serious damage, especially during photoresist ashing. In this work, a Radial Line Slot Antenna (RLSA) microwave plasma source was used in an effort to minimize damage to low-k dielectrics as a result of photoresist ashing. The focus of the work was ashing in CO2–containing gas mixtures of test wafers partially covered with blanket low-k and photoresist layers. Damage to the SiCOH (k=2.5) low-k dielectric was characterized using Spectroscopic Ellipsometry, FTIR and XPS. It was found that low pressure (~ 5 mTorr) and high bias voltage (~2000 V) were beneficial in terms of minimizing low-k damage. XPS revealed that, under these conditions, an oxide “crust” formed on the surface of the low-k, that apparently protected the underlying material. Low pressure favors an enhancement of the ratio of the ion –to- O-atom flux. Energetic ions can be instrumental in forming this oxide crust by near surface ion implantation. The oxide hinders diffusion of the (already low density) O atoms into the low-k film resulting in minimal damage.