| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | T.Y. Yagisawa, Keio University, Japan |
| Authors: | T.Y. Yagisawa, Keio University, Japan T.M. Makabe, Keio University, Japan |
| Correspondent: | Click to Email |
As the size of ULSI elements shirinks further, functional design for a top-down plasma processing will be strongly needed in order to solve many types of technological difficulties induced by plasma etching. Actually, under the present design rule for DRAM devices, a contact hole with high aspect ratio (> 20) is required.
The reactive ion etching (RIE) of high aspect contact hole (HARC) or inter layer dielectric has been traditionally performed by fluorocarbon gas chemistry in a two-frequency capacitively coupled plasma (2f-CCP) reactor. As is well known, SiO2 etching in fluorocarbon chemistry proceeds under the competition of surface protection by the deposition of CxFy radicals and chemical sputtering by directional CFx+ ions. Under a practical condition for SiO2 etching where the radical flux is larger than that of ions, a reactive mixing layer (SiOxFy), formed under excessive F radicals assisted by high-energy ion bombardment, is always covered with thick polymer layer (CxFy). Consequently, the etching is essentially carried out through the removal of polymer layer and the chemical reaction in a mixing layer. The side wall is simultaneously protected against the energetic ions by CxFy polymer deposition.
Under the circumstance, we have developed the two-layer sufrace model for the simulation of SiO2 etching profile in fluorocarbon gas chemistry. This model clarified the effects of reactive species (ions and radicals) on the SiO2 etching profile [1] and the dependence of etch rate on the pattern size (RIE-lag) [2].
In this paper, we will propose a new surface model for SiO2 etching which accounts for the selectivity between SiO2 and underlying Si substrate in HARC processing. Feature profile evolution and the selectivity during SiO2 etching can be coincidentally discussed as functions of flux of reactive species and impact ion energy. In addition, the effect of resist mask erosion will also be discussed.
[1] T. Shimada et al, Jpn. J. Appl. Phys. 45, p. 132, (2006).
[2] T. Makabe et al, Plasma Sources Sci. Technol. 18(1), #014016, (2009).