Title Mechanism of k-value Reduction of PECVD Low-k Films Treated with He/H2 Ash Plasma A.M. Urbanowicz, M. Cremel, K. Vanstreels, D. Shamiryan, S. De Gendt, M.R. Baklanov Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France FirstName LastName – Activity / Group

Recommendations for future work Title Outline Introduction organic removal from low-k by He/H2-DSP* ash detection of porogen residues by UV spectroscopic ellipsometry Experimental Results depth of porogen residue removal for different low-k’s mechanism of k-value reduction by He/H2-DSP* effect of porogen residue removal on mechanical properties Conclusions Recommendations for future work *DSP – downstream plasma Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France FirstName LastName – Activity / Group

Organic material embedded in low-k matrix is removed by He/H2-DSP without Si-CH3 group breakage 1 Photresist removal with “zero damage” residue removal TOFSIMS shows carbon removal, but it does not come from Si-CH3, as FTIR shows 1A. M. Urbanowicz, et al., in 25th Advanced Metallization Conference, San Diego, CA, 2008 2A. M. Urbanowicz, et al., in Electrochemical and Solid State Letters, 12(8), 2009 Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France

UV ellipsometry is very sensitive to presence of porogen in low-k films SiOC:H matrix has silmilar optical properties to SiO2 Porogen residue (a-C) contains sp2 orbitals (C=C) which have transtion band ~4.5 eV (275 nm) SiOC:H matrix P. Marsik, A. Urbanowicz et al., AMC 2008 proc., p. 543-549 (2009) Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France

Experiment Spin-on PECVD PECVD Spin-on UV curing: Ash: 20 – 700 s Porogen residue removal Ash: 20 – 700 s porogen Porogen residue Spin-on Spin-on Organic removal? Silica nanoparticles UV curing Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France

He/H2-DSP removes organic content from all films Title He/H2-DSP removes organic content from all films Pristine films properties Spectroscopic ellipsometry Film UV-source Open porosity k CVD 2.5 B2 >200 nm 24 % 2.5 E2 ~172 nm CVD 2.3 Ea 32 % 2.3 Eb 34 % B3 36 % SOG 2.3 N 32% Before Porogen residue content After Observations: PECVD with k~2.3 contains more porogen residues Spin-on contains minimal amount of organics N Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France FirstName LastName – Activity / Group

Depth of porogen residue removal decreases logarithmically with time Title Depth of porogen residue removal decreases logarithmically with time UV-spectroscopic ellipsometry Mass balance on 300 mm wafers To fit logartimic functions (Eddy’s paper). Animations -> trasform to logaritmic scale. Observation: Depth of porogen residue removal increases with film porosity Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France FirstName LastName – Activity / Group

Depth of porogen residue removal decreases logarithmically with time Title Depth of porogen residue removal decreases logarithmically with time UV-spectrocopic ellipsometry Mass balance on 300 mm wafers To fit logartimic functions (Eddy’s paper). Animations -> trasform to logaritmic scale. Observation: Depth of porgen residue removal increases with film porosity Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France FirstName LastName – Activity / Group

Overash results in k-value reduction, but.. Hg-probe Observation SOG and CVD 2.5: Longer times cause k-value increase Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France

k-value increase for longer over-ash times can be explained by minor polar group incorporation N2-purged FTIR Observation FTIR shows minor polar groups incorporation for all treated films Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France

Final k-value is determined by 2 competing phenomena: density reduction and polar group incorporation Debye’s equation Polar groups incorporation Density reduction Mass balance on 300 mm wafers FTIR k  k Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France

CVD 2.3 show the highest k-value reduction accopanied by mechanical properties degradation Nano-indentation Hg-probe Observations: No mechanical properties reduction for CVD 2.5 and SOG 2.3 film while sinficant mechanical properties degradation for CVD 2.3 The highest k-value reduction for CVD 2.3 Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France

3 effects of He/H2-DSP overash due to porogen residue/organics removal and silianol incoroporation Nano indentation and Hg-probe I II Ref I – k and YM ~ const CVD 2.5 (T<100 s) II - k and YM ~ const CVD 2.5 (T>100 s) and SOG 2.3) III - k and YM  CVD 2.3 Ref Ref Ref III Ref Ref Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France

Title Conclusions Mechanism of k-value reduction of PECVD low-k’s exposed at He/H2-DSP ash is a superposition of two competing phenomena: porogen residue removal results in k-value reduction minor silanol group incorporation results in k-value increase Reduction of k-value by removing porogen residue is beneficial (T<100 s)for PECVD with k=2.5 since no degradation of their mechanical properties is observed Depth of porogen removal decreases logarithmically with time. Can be as high as: ~70 nm for PECVD (k=2.5) with 25% open porosity ~160 nm for PECVD (k=2.3) with >32 % open porosity Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France FirstName LastName – Activity / Group

Title Future plans Effect of He/H2-DSP ash modification on subsequent damascene processing steps: chemical or physical-chemical cleaning barrier deposition Fabrication of porogen-residue-free PECVD films by porogen removal by He/H2-DSP before UV curing step Adam Urbanowicz PESM 2010, 4-5 March, Grenoble, France FirstName LastName – Activity / Group