AVS 52nd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS-MoP

Paper PS-MoP11
Highly Selective W/WN/Poly-Si Etching by using RLSA Microwave Plasma Source

Monday, October 31, 2005, 5:00 pm, Room Exhibit Hall C&D

Session: Plasma Science and Technology Poster Session
Presenter: T. Nishizuka, Tokyo Electron, LTD., Japan
Authors: T. Nishizuka, Tokyo Electron, LTD., Japan
K. Song Yun, Tokyo Electron, LTD., Japan
K. Ishibashi, Tokyo Electron, LTD., Japan
T. Nozawa, Tokyo Electron, LTD., Japan
T. Goto, Tohoku Univ., Japan
T. Ohmi, Tohoku Univ., Japan
Correspondent: Click to Email
W/WN/Poly-Si stack is used as a gate material of DRAM. For the etching of W/WN layer, high density plasma sources, such as ECR, ICP, etc., are usually applied with Cl@sub2@+O@sub 2@ gases.@footnote 1@ An important requirement of this etching is selectivity to Poly-Si. The selectivity can be improved by increasing oxygen fraction. However, actual selectivity used to be 1 or so because oversupply of oxygen causes deposition which is attributed to oxidized etching by-products, WO@sub 3@. In this study, we developed a RLSA (Radial Line Slot Antenna) microwave plasma source, and evaluated it on the W etching process. It can generate uniform surface-wave plasma with low electron temperature without magnets,@footnote 2,3@ and therefore it has compact chamber which reduces gas residence time. As for gas chemistry, N@sub 2@ addition was evaluated along with Cl@sub 2@+O@sub 2@ gases condition. As a result, we obtained high selectivity>5, W etch rate>100nm/min and straight W profile under the condition of fairly low stage temperature=60°C. We also found N@sub 2@ gas addition in high flow rate was effective to achieve both high selectivity and good profile. The role of nitrogen appeared to contribute to variety of radicals in the plasma rather than nitridation of Poly-Si and W surface. It probably controls the amount of reactive Cl and O radicals then reduces oxidization of by-products and Poly-Si etching rate. Furthermore, no charge-up damage has been observed on antenna MOS structure under any conditions. We believe that the high density plasma with low electron temperature and short residence time of gases lead to those performances. @FootnoteText@ @footnote 1@ T. Umezawa et.al., 1998 Dry Process Symposium, p49.@footnote 2@ H. Kokura et.al., 1999 Dry Process Symposium, p209.@footnote 3@ T. Ohmi, Semiconductor Manufacturing, Nov.2003, p110.