| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS2-TuM |
| Session: | Advanced FEOL/Gate Etching |
| Presenter: | S. Wege, Plasway, Germany |
| Authors: | J. Paul, Fraunhofer Institute for Photonic Microsystems (IPMS-CNT), Germany X. Thrun, Fraunhofer Institute for Photonic Microsystems (IPMS-CNT), Germany S. Riedel, Fraunhofer Institute for Photonic Microsystems (IPMS-CNT), Germany M. Rudolph, Fraunhofer Institute for Photonic Microsystems (IPMS-CNT), Germany S. Wege, Plasway, Germany C. Hohle, Fraunhofer Institute for Photonic Microsystems (IPMS-CNT), Germany |
| Correspondent: | Click to Email |
The main challenge for future leading edge patterning results from an aggressive trend in reduction of resist thickness for high resolution lithography. For instance, at the 25 nm DRAM technology node, a maximum resist thickness of 30 to 60 nm is predicted by the ITRS for 2014. Moreover, the hard mask thickness will be limited by the thickness of the photoresist. Different approaches such as multi-layer resists were discussed to enable pattern transfer with reduced resist thicknesses. These approaches are focusing more and more on innovative underlayer materials and anti-reflective coatings providing a higher etch selectivity. Novel hard mask concepts with reduced layer thickness and improved etch selectivity can be seen as an alternative strategy.
The present work reveals a new hard mask concept based on ZrO2 and HfO2 materials in combination with a SiO2 capping layer to provide the high resolution pattern transfer into the substrate. An excellent silicon and carbon etch selectivity is focused for semiconductor manufacturing. Besides the scaling capability, the hard mask concept was evaluated in terms of etch selectivity, hard mask roughness, removal of remaining hard mask after etch and cost-saving deposition method. Therefore atomic layer and spin-on depositions of HfO2 and ZrO2-based hard masks were investigated. Additionally the influence of dopants on the etch properties and patterning results was evaluated.
The dual hard mask concept was demonstrated using 35 nm thin layers of ZrO2 and HfO2 based material and 45 nm SiO2 deposited on 300 mm wafers. The resist (50 nm) was directly applied on the hard mask and arrays of holes and trenches (CD 30 nm to 500 nm) were printed by electron beam direct writing. The hard mask open was performed in a two-step process by CCP and ICP type etch chambers. The hole and trench pattern were transferred into silicon and carbon by dual-frequency MERIE CCP and triple-frequency CCP type etch system, respectively. Finally the remaining mask was removed by wet etching without deterioration of the etched profiles. This sequence allowed the preparation of structures with aspect ratios up to 20:1 (CD 30 to 60 nm) and revealed a high overall hard mask selectivity to silicon e.g. ~ 35:1.
This new dual-layer concept enables a significant reduction of overall hard mask thickness and the patterning of 30 nm structures and a potential technology approach for more critical structures in the sub 20 nm range.