| AVS 55th International Symposium & Exhibition | |
| MEMS and NEMS | Monday Sessions |
| Session MN+NC-MoA |
| Session: | Fabrication at the Micro- and Nano- Scales for MEMS/NEMS |
| Presenter: | T. Murayama, ULVAC, Inc., Japan |
| Authors: | T. Murayama, ULVAC, Inc., Japan T. Morikawa, ULVAC, Inc., Japan K. Suu, ULVAC, Inc., Japan |
| Correspondent: | Click to Email |
In Si etching such as wafer level packaging technology for MEMS and the formation vertical interconnection of three-dimensional integration LSI, to establish high rate is important problem. Especially under 10um space pattern on 200-mm-diam wafer, it is desired to etch Si at high rates achieving anisotropic features. Commonly, it is essential to produce huge amount of F radicals in Si etching mainly dominated by radical reaction in Si surface, ion assist effect is important to achieve anisotropic feature.1 Our experiments are conducted using NLD-Si etcher which we introduced sputtering system for sidewall passivation to NLD (magnetic Neutral Loop Discharge) etcher for quartz deep etching.2,3 In this study, we tried to improve etching rate using a novel antenna ｢Multi-Slits rf Antenna｣ for controlling both ion and F radical density. This antenna consisted of grid type structure in which several slits are set parpendically in same direction to RF current. In experiments we used 3 pararell slit antenna in other words 4 pararell current paths structure, expecting high-density plasma is generated because of ion and radical generation area extending in space compared with simple single-turn antenna.Next, for control anisotropic feature, we investigated the dependence of bias rf frequency in high-density NLD plasma using this multi slit rf antenna. We used SF6 as process gas. Consequently, this antenna improved in etching rate more than two times compared with our conventional antenna. However etching feature shifted bowing. We considered that this result is caused by not only F radical increase but also sheath impedance decrease by high-density plasma. To overcome this sheath impedance decrease, we changed bias rf frequency to 2 MHz from 13.56 MHz. In low bias frequency we etched 4 um space pattern, then high rate and anisotropic feature were achieved etching rate is 10.5 um/min, selectivity (Si/SiO2) is 60 over. It is considered that for high rate and high quality Si etching it is very important that the control of incident ion energy distribution in addition to high-density radical produce.
1 J. W. Coburn and H. F. Winters: J. Appl. Phys. 50 (1979) 3189.
2 W. Chen, et al.; J. Vac. Sci. Technol., A 19 (2001) 2936.
3 Y. Morikawa, et al.; Thin Solid Films 515 (2007) 4918.