| AVS 56th International Symposium & Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS1-MoM |
| Session: | Advanced Interconnect Etch |
| Presenter: | J. Ducote, STMicroelectronics, France |
| Authors: | J. Ducote, STMicroelectronics, France T. David, CEA-LETI-MINATEC, France N. Posseme, CEA-LETI-Minatec, France T. Chevolleau, LTM-CNRS, France A. Ostrovsky, STMicroelectronics, France M. Guillermet, CEA-LETI-Minatec, France F. Bailly, STMicroelectronics, France E. Pargon, LTM-CNRS, France R. Inglebert, LTM-CNRS, France C. Verove, STMicroelectronics, France O. Joubert, LTM-CNRS, France |
| Correspondent: | Click to Email |
As copper lines are continuously scaling down, the biggest issue we are facing today is the copper resistivity increase due to the scattering effect at the grain boundaries and surface. Recent study has proved that this behavior is potentially associated with the sidewalls roughness of the lines also leading to an increase of the time dependent dielectric breakdown [1].
Starting from an initial line width roughness (LWR) printed in the photoresist after the lithography step, we have investigated the impact of the etching chemistries on the LWR transfer in a damascene structure as a function of the hard mask strategy (metallic or organic).
To monitor the LWR variation, a three-dimensional critical dimensions-atomic force microscope (CD-AFM) from Veeco has been used. This technique allows reconstruction of the trench profiles of the patterns and measurement of the LWR along the trenches. However such analyses require the development of a specific protocol to determine the LWR after porous SiOCH integration in a dual damascene architecture.
In order to avoid any consumption or sticking of the AFM tip, it is mandatory i) to use a tip with a high stiffness and ii) to measure the LWR of the damascene structures after the etching and wet cleaning. The line width roughness measurements are performed on 100 scan lines over a scan length of 2 µm with a tip diameter of 100 nm and tip edge of 20nm, allowing a measurement accuracy of less than 1 nm.
We have investigated the impact of the two masking strategies investigated (titanium nitride (TiN) versus organic) and different etching chemistries (used for BARC open, TiN open and dielectric etching) on the LWR transfer by monitoring the LWR variation between LWR on photoresist trenches and LWR on p-SiOCH trenches.
No impact of the different chemistries investigated has been observed with a TiN hard mask. The initial LWR on the photoresist patterns (~6nm) remains almost constant after porous SiOCH lines etching. The comparison of the transfer of sidewalls roughness between a TiN and an organic mask will be also presented.
[1] E. Soda et al., JVSTB, 27(2), 2009, pp649