Settling of Colloidal Silica Particles in CMP Slurry ...

1 Settling of Colloidal Silica Particles in CMP Slurry :Monitoring, Effect, and HandlingJie Lin and W. Scott RaderFujimi Corporation R&D, USAWhy a concern for particle Settling in Slurry ?2 Settling of particlesChanges in Physical properties Particle concentration Chemical concentrationsEffect onPolishing performance ( removal rate)Three slurries have different effects from particle settlingSlurryParticlesize (d50) Silica (wt%)Surfactant(wt%)pHViscosi ty(cP)CMPapplicationSlurry A~ 67 nm~ 6% B~ 100 nm~ 7%~ 1 % C~ 65 nm~ 5%< % of particle settlingSlurry A after Settling for 10 yearsSize (nm) mmV (cm/yr) Density: particle , Slurry ; viscosity of Slurry %Particle diameter (nm)Particle size distribution: Slurry A01020304050050100150200 Velocity (cm/year)Particle diameter (nm)Velocity of particle Settling : Slurry A2( rp - rf )9mV = g R2 Effect of particle Settling : Slurry AParticle size distribution, SiO2wt%, turbidity, specific gravity, and viscosity increase with depth because of particle A in 2 L bottle after sitting for 6 months.

2 D50 ~67 nm, SiO2~6 %, pH , for Cu in sample bottle (cm)Turbidity (NTU) in sample bottle (cm)PSD d50 (nm) in sample bottle (cm)Specific in sample bottle (cm)Viscosity (cP) in sample bottle (cm)PSD d90-d10 (nm) in sample bottle (cm)SiO2wt%Effect of particle Settling : Slurry A Concentration of particle increases with depth. Concentrations of chemicals do not change with : Slurry C exhibits similar characteristics to Slurry A. 5 Depth(cm)ParticleChemical 1 Chemical 2 Chemical concentration in Slurry A* Slurry A in 2 L bottle after sitting for 6 of particle Settling : Slurry B Particle concentration increases with depth, similar to Slurry A. However, total organic carbon (TOC) profile indicates a change in surfactant concentration (adsorbed on Particles ) with B in a 2 L bottle after sitting for 5 monthsd50 ~100 nm, SiO2~7 %, pH , for Cu CMPNo ASolid in sample bottle (cm)SiO2wt% in sample bottle (cm)NormalizedTOCadsorbed on particlesEffect of particle Settling on removal in sample bottle (cm)Cu RR by Slurry A ( /min)polish #1polish # in sample bottle (cm)Cu RR by Slurry B ( /min)polish #1polish # in sample bottle (cm)TEOS RR Slurry C ( /min)polish #1polish #2meanCASlurry in 2 L bottle: (A) Slurry A after 6 months; (B) Slurry B after 5 months; (C) Slurry C after 6 months7 ConsiderationSlurry ASlurry BSlurry C CMP application ( material to be polished)CuCuTEOS Mechanism of CMP process: dominant polishing (chemical vs.)

3 Mechanical)ChemicaldominantChemicaldomin antMechanicaldominant Change in particle concentration with depthYesYesYes Change in chemical concentration with depthNoYesNo Effect on removal rateNoYesYesLPC for monitoring of Settling and mixing LPC is a sensitive method for monitoring Settling of Particles and re-dispersion of settled in sample bottle (cm) Slurry A: LPC > mm0 day22 day, before mixing22 day, after L bottleEffect of Settling and mixing in a large in Slurry tote (in) Slurry B: Specific gravitybefore mixingafter in Slurry tote (in) Slurry C: Specific gravitybefore mixingafter mixingB(A) Slurry B in a 320 G tote after 9 months,mixing by pumping from one tote to another Settling of Particles results in change of specific gravity with depth. Uniform profile of specific gravity is recovered by mixing. 9(B) Slurry C in a 320G tote after 2 months, mixing by circulation in a tote, one turn-overConclusion Settling of Particles in CMP Slurry will result in changes in physical properties, particle concentration, and sometime chemical concentration as a function of depth in a container.

4 These changes may or may not affect the removal rates depending on characteristics of Slurry and mechanism of polishing. A container of Slurry must be properly mixed to re-disperse Particles and chemicals before being used in analysis or polishing to avoid erroneous authors thank colleagues at Fujimi Corporation, particularly Karl Ulbricht, Annette Schaper, and Dr. Charles Poutasse, for assistance and you!11 Appendix I12 MeasurementInstrumentTurbidityMicro PTI turbidimeter (HF Scientific, Inc.)SpecificgravityDMA 5000 density meter (Anton Paar)ViscosityAMVnviscometer (Anton Paar)Particle size distributionLA-950 Laser diffraction particlesize analyzer(Horiba,Ltd.) Silica (SiO2) wt% Optima 7000DV ICP-OES spectrometer (Perkin Elmer)TOC (totalorganic carbon)TOC-L Total organic carbon analyzer (ShimazuCorp.)SurfactantZorbax300SB C18 column and Agilent Infinity 1260 HPLCP olisherMulti Prep bench-top polisher (Allied High Tech Products, Inc.)

5 Polishing padFujibo H7000 psiHead/platen speed22/200 rpmSlurry flow rate50 mL/minPolishing time45 secCu measurementCDE ResMap 178 TEOS measurementF50 Thin-Film Mapper (Filmetrics, Inc.)Measurement& instrumentPolishing &metrologyCu CMP with Slurry A is dominated by chemical Cu removal rate 13 Mechanism of Cu CMP with Slurry AAppendix IILPC measurement and depth profileA typical depth profile of LPC024681012140100020003000 Depth in the sample bottle (cm)LPC> of large Particles (after 6 days) Settling of large Particles outof the top layerRelatively uniform distribution of large particlesin the middle layerAccumulation of large Particles in the bottom layerReference 3: CAMP 2007 (Rader, Lin, and Holt)Set up for LPC measurementTo Particle Counter14 cm450 mLSet up for LPCmeasurementTo Particle Counter14 Appendix III