A proposed magnetically enhanced reactive ion etcher for ULSI

An ultraclean (UC) magnetically enhanced reactive ion etcher (MERIE) is proposed to overcome the limitations of the present-state MERIE available commercially. The sensitivity of gas compositions, pumping speed, substrate temperature and magnetic field intensity are discussed as examples of hardware-related process limitations. Five major configuration changes are proposed in the system: (1) improved effective pumping speed; (2) supplementary magnets for uniform and stable plasma distribution; (3) dual RF excitation for independent control of ion energy and flux; (4) DC-biased shield electrode for minimum chamber material contamination; and (5) DC-biased substrate. A study with a dual RF excitation system found that DC-baising the Si substrate in low-energy SiO/sub 2/ etching process can significantly reduce the Si etching rate by impeding positive ions from reaching the substrate. In addition, SiO/sub 2/ to Si etching rate selectivity can be significantly improved during the overetch step in SiO/sub 2/ etching of high-aspect-ratio contact holes.<
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