AVS 60th International Symposium and Exhibition
    Plasma Science and Technology Monday Sessions
       Session PS-MoA

Paper PS-MoA8
Improvements in Low-k Damage and Hard Mask Selectivity in BEOL Dielectric Etch Using C5HF7

Monday, October 28, 2013, 4:20 pm, Room 104 C

Session: Advanced BEOL/Interconnect Etching
Presenter: R.L. Bruce, IBM T.J. Watson Research Center
Authors: R.L. Bruce, IBM T.J. Watson Research Center
T. Suzuki, Zeon Chemicals LP
M. Nakamura, Zeon Chemicals LP
S.U. Engelmann, IBM T.J. Watson Research Center
E.A. Joseph, IBM T.J. Watson Research Center
N. Fuller, IBM T.J. Watson Research Center
E.M. Sikorski, IBM T.J. Watson Research Center
A. Itou, Zeon Corporation
Correspondent: Click to Email
As feature sizes continue to decrease, significant issues are found using highly selective fluorocarbon gases to etch interconnect low-k dielectrics. Three examples of these challenges include; line wiggling, low-k damage, and low selectivity (e.g. to organic masks). To address these challenging issues, we have evaluated C5HF7 and other novel etch gases for 14nm and 22nm devices to determine if they enable the optimized fabrication of BEOL interconnects. Etch performance is assessed for both trench and via patterns and also when incorporated into full dual-damascene structures. Compared to conventional fluorocarbon etch gases such as C4F6 and CF4/CHF3 mixtures, experiments with C5HF7 have shown a substantial increase in low-k dielectric to metal hard mask and capping layer selectivity for trench and self-aligned via etching. Low-k damage is also investigated by post-etch HF treatment to measure critical dimension loss from dissolution of plasma-damaged dielectric. A significant reduction in damage is observed with C5HF7 in low-k films of two different dielectric constants. Finally, we propose a mechanism for high selectivity, low damage dielectric etch at sub-80nm pitch structures using rationally-designed novel etch gases.