| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS-WeM |
| Session: | Plasma Surface Interactions (Fundamentals & Applications) I |
| Presenter: | A. Nakagawa, Tokyo Electron AT Limited, Japan |
| Authors: | A. Nakagawa, Tokyo Electron AT Limited, Japan H. Mochiki, Tokyo Electron AT Limited, Japan M. Dojun, Tokyo Electron AT Limited, Japan K. Yatsuda, Tokyo Electron AT Limited, Japan S. Okamoto, Tokyo Electron AT Limited, Japan |
| Correspondent: | Click to Email |
Fabrication of latest DRAM capacitor structure requires precise etch profile control of silicon dioxide due to the continuous trend of narrowing pitch and high aspect ratio (HAR) features. While a number of issues are recognized such as twisting and bottom distortion, bowing became an outstanding subject for DRAM technology development for its complexity to cope with the bottom CD; even slight bowing leads to interference with the adjoining structures, and adjustment of process conditions frequently accompanies decreased bottom CD. In the present report we explore the effect of DC superimposition in capacitively-coupled plasma (CCP) as a countermeasure, taking advantage of its controllability on necking level at the mask facet.
Generally speaking, bowing is induced by the reflected ions at the mask facet attacking silicon dioxide sidewalls. Moreover, shrunk mask entrance interferes with incident radicals to transfer to the hole bottom, narrowing its size. One of the solutions utilizes high ion energy, but our results demonstrated a strong correlation between mask necking and bottom CD, thus the evaluation focused on optimization of mask necking.
Next, observation of deposition at the silicon dioxide sidewall varied with process parameters lead to systematic understandings of its physical amount and local enhancement, as well as the declining behavior at the removal process. By means of process parameters, the necking degree of the mask opening was controlled and the relationship among necking, bowing and bottom CD was examined.
As a result, it is necessary to improve necking at mask opening to minimize bowing and to keep bottom CD simultaneously. Optimization of process parameters enables etch profile enhancement by dispersing necking location, which normally decreases selectivity to mask. However, DC-superimposed CCP facilitated maintaining selectivity to mask with preferable etch profile, and less bowing with sufficient bottom CD.