| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS-MoA |
| Session: | Advanced BEOL/Interconnect Etching |
| Presenter: | Hongyun Cottle, TEL Technology Center, America, LLC |
| Authors: | H. Cottle, TEL Technology Center, America, LLC I. Saraf, TEL Technology Center, America, LLC A. Metz, TEL Technology Center, America, LLC P. Biolsi, TEL Technology Center, America, LLC |
| Correspondent: | Click to Email |
Continued pitch scaling of semiconductor devices to 7nm node and beyond dimensions utilizing conventional 193i based multiple patterning techniques is rapidly driving up cost, complexity, and variability control. EUV patterning can be used to mitigate or delay the challenges of pitch scaling through multiple patterning, but introduces new challenges of its own. EUV lithography introduces new types of resists that are thinner and less etch resistant compared to conventional 193nm resists. Interactions of polymers with plasma etch environments can lead to large changes of the polymer material properties and the three-dimensional nanostructures they pattern. Mask deformation during such etch process can lead to changes in nanoscale topography of device features, often with undesirable consequences, such as increased LER and LWR, tip-to-tip degradation, and line wiggling. Plasma etch faces a significant challenge to optimize its process window to enable high yields with EUV patterning.
This paper presents an unique etch process employing a dynamic etch during softmask open to improve EUV photoresist etch selectivity by greater than two fold while maintaining critical feature dimensions, such as elliptical contact minor vs major axis CD ratio. By carefully controlling the polymer deposition vs. polymer assisted etching temporal cycle, a very thin layer of conformal polymer can be used to precisely etch and transfer the desired pattern. By utilizing a direct current superposition (DCS) technology, EUV photoresist can be treated to improve not only its etch resistant, but also LER and LWR. After the in-situ photoresist treatment, the dynamic etch process initiates and defines the pattern transfer into softmask, followed by etch steps to anisotropically complete the pattern transfer. Reported is the structural characterization pre and post-etch detailing LER and LWR improvement, and shrink ratio control. In addition, a mechanistic model will be proposed based on optical emission spectroscopy (OES) and thin film compositional analysis.