科研之友
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摘要
The best strategies to transfer nanoholes formed from the self-assembly of Polystyren/Polymethyltnethacrylate (PS/PMMA) based block copolymers into a silicon substrate are investigated. The authors show that specific issues are associated with the plasma etching of materials through the PS masks obtained from self-assembly. Indeed, due to the nanometric size of sub-15 nm contact holes and to their inherently high aspect ratio (>5), plasma etching processes typically used to etch SiO2 and silicon in the microelectronic industry must be revisited. In particular, processes where the etching anisotropy relies on the formation of passivation layer on the feature's sidewalls are not adapted to nanometric dimensions because these layers tend to fill the holes leading to etch stop issues. At the same time, the ion bombarding energy must be increased as compared to a typical process to overcome differential charging effects in high aspect-ratio nanoholes. However, by developing appropriate processes such as synchronized pulsed plasmas-the authors show that it is possible to etch 70nm deep holes into silicon by using block copolymers and a hard mask strategy. Another interesting observation resulting from these experiments is that for sub-15 nm holes, a critical dimension (CD)-dispersion of few nm leads to strong aspect ratio dependent etch rates. In addition, a careful analysis of the dispersion of the holes' CD after each plasma steps shows that the CD control is far from satisfying advanced CMOS technology requirements. A critical issue comes from the uncompleted PMMA removal from the PS/PMMA matrix during our self-assembly process: variable amount of PMMA remains in the PS holes, leading to microloading effects during the etching steps, which in turn generates CD-control loss. This problem perhaps can be solved by combining UV exposure to acetic acid treatment to provide PS masks free of PMMA residues before plasma etching. (0 2014 American Vacuum Society.
- 出版日期2014-9
- 单位中国地震局
