Process Optimization of UV Curing for Ultra Low-k Dielectrics and High-Stress SiN Liners
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0990-B03-22
Process Optimization of UV Curing for Ultra Low-k Dielectrics and High-Stress SiN Liners Masazumi Matsuura1, Kinya Goto1, Shinobu Hashii2, Noriko Miura1, Yoshihiro Miyagawa1, Tatsunori Murata1, Yoshikazu Tsunemine1, and Koyu Asai1 1 Process Development Dept., Renesas Technology Corp., 4-1,Mizuhara, Itami, 664-0005, Japan 2 Renesas Semiconductor Engineering Corp., 4-1,Mizuhara, Itami, 664-0005, Japan ABSTRACT This paper describes process optimization of UV curing for ultra Low-k SiOC (ULKSiOC, k=2.65) and High stress silicon nitride (HS-SiN) liner. We have investigated the impact of UV curing using different UV bulbs (UV-X and UV-Y) on BEOL process damages to the ULKSiOC. The k-value variations of ULK-SiOC modified with UV-X with higher photon energy than UV-Y are greater than those of the pristine ULK-SiOC and the ULK-SiOC modified with UV-Y. These results are consistent with the previously reported FT-IR and NMR analyses that the UV-X generates 3-fold Si-O ring defects and Si-H bonds in the ULK-SiOC. The solvent diffusion of the UV-modified ULK-SiOC with UV-X is faster than that of the UV-modified ULK-SiOC with UV-Y. This result indicates that the pore size of UV-modified ULK-SiOC with UV-X is larger than that of UV- modified ULK-SiOC with UV-Y. The dependence of the stress increase in HS-SiN liner on different UV bulbs (UV-X and UV-Y) has been investigated by using stress measurement and FT-IR. The UV-modified HS-SiN liner with UV-Y achieves higher tensile stress, compared to the UV-X. FT-IR results have revealed that UV-Y is more effective for the dehydrogenation and SiN crosslinking, resulting in the greater increase in the tensile stress. INTRODUCTION UV curing technologies have proven to be effective for enhancing device performances in FEOL and BEOL processes at the 45nm technology node and beyond. We have reported that ultra Low-k SiOC (ULK-SiOC, k=2.65), which is required in advanced SoC devices to reduce RC interconnect delay and crosstalk noise, is greatly hardened with the UV modification [1]. High stress silicon nitride (HS-SiN) liner with tensile stress is a promising approach to boost the transistor drive current in nMOS-FET. UV modification enables the tensile stress of the SiN liner to be higher than that of plasma CVD deposited SiN liner without any post-modifications [2]. In this study, we focused on the process optimization of UV curing for ULK hardening and high-stress SiN liner. We have investigated the impact on process damage for ULK hardening and the effect on stress increasing for high-stress SiN liner. Key question to UV curing is what the desirable UV wavelength band is. From the viewpoint of the reduced process damage in the ULK-SiOC and the increased tensile film stress in the HS-SiN liner, the desirable UV wavelength bands for each application will be proposed. EXPERIMENT ULK-SiOC films (k=2.65) to be conducted were prepared by using a conventional plasma CVD tool with the capacitive-coupling RF plasma source. Two types of UV bulbs (UVX and UV-Y) were employed for UV curin
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