AVS 52nd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS1-MoA

Paper PS1-MoA3
Etching Mechanisms of Low-k Material with the Solid First@superTM@ ILD Process in Fluorocarbon based Plasma

Monday, October 31, 2005, 2:40 pm, Room 302

Session: Dielectric Etch I
Presenter: T. Chevolleau, CNRS/LTM, France
Authors: T. Chevolleau, CNRS/LTM, France
D. Eon, CNRS/LTM, France
M. Darnon, CNRS/LTM, France
L. Vallier, CNRS/LTM, France
O. Joubert, CNRS/LTM, France
Correspondent: Click to Email
In CMOS technology, most of the interlayer dielectric materials achieve low k value by introducing porosity in order to reduce the total resistance capacitance (RC) delay in the interconnect levels. However, porous materials as pSiOCH are very sensitive to ash and etch plasma exposure and one of the integration challenges is to reduce the impact of these plasma processes. To solve this issue, one of the emerging solutions is the Solid First@superTM@ ILD process. In this approach, the porosity in SiOCH is generated by releasing porogens (carbon based polymer) after patterning or copper filling. The SiOCH containing porogen materials are expected to behave like non-porous materials during the etching and ashing processes (as long as the porogens have not been released). This study concerns the etch mechanisms of a solid first SiOCH low-k (Zirkon V8@super+@ from Rohm and Haas) and selectivitiy to SiC and SiCN etch stop layer. The etching is performed on blanket wafers in an industrial MERIE reactor (Magnetically Enhanced Reactive Ion Etcher) using fluorocarbon based plasmas. Etch rates are measured by ellipsometry, chemical surface composition is analyzed by quasi in-situ XPS, and bulk modification by infrared spectroscopy. Etching is performed in fluorocarbon based plasmas (CF@sub4@) in mixture with Ar, CH@sub2@F@sub2@, or O@sub2@). Similarly to dense SiOCH materials, the etch rate decreases with either increasing Ar dilution or polymerizing gas addition. Nevertheless, XPS analyses reveal that the increased carbon content in the low-k material due to the presence of the porogen leads to the formation of a thick fluorocarbon overlayer during plasma exposure. Consequently, etch stop phenoma can occur even with low polymerizing fluorocarbon plasmas. On the other hand, FTIR analyses clearly show that the presence of porogens in the SiOCH matrix prevent bulk modification during a fluorocarbon plasma exposure.