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

Paper PS-MoP17
A Stacked Mask Process (S-MAP) for Precise CD Control using 100 MHz CCP RIE

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

Session: Plasma Science and Technology Poster Session
Presenter: H. Hayashi, Toshiba Corporation, Japan
Authors: H. Hayashi, Toshiba Corporation, Japan
J. Abe, Toshiba Corporation, Japan
A. Kojima, Toshiba Corporation, Japan
I. Sakai, Toshiba Corporation, Japan
T. Ohiwa, Toshiba Corporation, Japan
Correspondent: Click to Email
The stacked mask process (S-MAP)@footnote 1@ has been developed to provide improved critical dimension (CD) control in deep UV lithography, where it is necessary to use thin photo resist (P.R.) susceptible to etch erosion. In S-MAP, the P.R. pattern is first transferred to a spin-on-glass (SOG) layer, then to spun-on carbon film. An oxygen-based chemistry has been widely used for organic film etching. However, it tends to cause a bowed profile due to excess oxygen radicals. Therefore, a nitrogen-based chemistry is often used, where a straight profile can be obtained because of the sidewall protection effect by nitrogen. But, when the nitrogen-based chemistry was applied to the etching of stacked film structure such as S-MAP, the SOG film peeled at the interface of SOG and carbon films during etching under some conditions. The mechanism of SOG peeling in nitrogen-based chemistry was examined by analyses of the SOG/carbon stacked film after etching, and it was found that nitrogen gas was trapped in the stacked film. On the other hand, the SOG surface exposed to the plasma was densified by ion irradiation. It is assumed that, as etching progressed, nitrogen molecules gradually accumulated in the stacked film until the nitrogen gas pressure in the film became high enough to cause SOG peeling. By using the 100 MHz capacitive coupled plasma (CCP) which can realize low pressure and low ion energy simultaneously, carbon film etching using nitrogen-less gas chemistry without bowing was realized, by suppression of oxygen radical density at low pressure. Furthermore, selectivity to SOG improved because of the low ion energy, and CD loss due to SOG erosion was reduced. In conclusion, S-MAP for the 55 nm pattern size with precise CD control was realized by using 100 MHz CCP RIE using nitrogen-less gas chemistry. @FootnoteText@ @footnote 1@J. Abe et al., Symp. Dry Process, (2001) 187.