Effects of Ring Design on CMP Process Stability and Slurry Usage

purify<strong>Effects</strong> <strong>of</strong> <strong>Ring</strong> <strong>Design</strong> on CMPProcess Stability and Slurry UsageprotecttransportChristopher Wargo*, David StockbowerMay 6, 2009CMPUG MeetingENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

Outline and Motivation <strong>Ring</strong> wear rates and lifetime Thermal environment at <strong>Ring</strong> interface <strong>Ring</strong> Surface Interactions Optimization <strong>of</strong> slurry usage Wafer results with alternate polymer and geometry– Break-In, removal rate, defects Process optimization with lower process COOPage 2ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

<strong>Ring</strong> Lifetime Correlates to Wear RatePPSPEEKPrePost Many studies have detailed wear rate, generally indicating lower CoFand wear rates for PEEK as compared to PPS– End user operating conditions have significant impact on final results Lower CoF results in lower energy states, as reflected in the thermalenvironment on the pad/ring interface Results indicated that there was no significant difference in the shearforce associated with the two ring designs, thus removing anyconcerns that the optimized retaining ring could increase pad wearPage 3ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

240Thermal Environment due to Polymer Choice Operating temperatures mayplay a role in the morechemically dominated CMPprocesses Overall, temperature effects aredriven by the pad/ring/waferinterface rather than thepad/pad conditioner interface. Platen and head asymptoteover time APD-800 tool for200/300 mm processingenables real timein-situ analysis504846444240153045607590105120135150165180195225210240Temperature ( ºC )464442403836Polishing Time ( min )153045607590105120135150165180195225210PPS / PU InterfacePEEK / PU InterfaceTemperature ( ºC )Polishing Time ( min )Page 4ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

Slurry Usage Measured In-Situ Two retaining rings with theindustry standard and optimizedslot designs were attached to a200-mm quartz waferUpside down for clarity The thickness <strong>of</strong> the slurry filmbetween the pad and wafer wasmeasured using dual emission UVenhanced fluorescence (DEUVEF)at different slurry flow rates (150and 220 ml/min), pad/wafer rotationrates (80 and 120 RPM) andretaining ring/wafer pressures (1.8and 3.6 PSI) The next slide shows the slurry filmthickness measurementsassociated with the two rings.Page 6ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

Slurry Reduced with Optimized <strong>Ring</strong>Standard Slot <strong>Design</strong>Alternate Slot <strong>Design</strong>Slurry Film Thickness ( m)Slurry Film Thickness ( m)12.010.08.06.04.02.00.012.010.08.06.04.02.080 RPM 1.8 PSI220 cc/min80 RPM 1.8 PSI150 cc/min80 RPM 3.6 PSI220 cc/minRegion ARegion B80 RPM 3.6 PSI150 cc/minRegion ARegion BSlurry Film Thickness ( m)Slurry Film Thickness ( m)12.010.08.06.04.02.00.012.010.08.06.04.02.0120 RPM 1.8 PSI220 cc/min120 RPM 1.8 PSI150 cc/min120 RPM 3.6 PSI220 cc/minRegion ARegion B120 RPM 3.6 PSI150 cc/minRegion ARegion BSlurry FilmThickness VaryingProcess Parameters0.080 RPM 1.8 PSI220 cc/min80 RPM 1.8 PSI150 cc/min80 RPM 3.6 PSI220 cc/min80 RPM 3.6 PSI150 cc/min0.0120 RPM 1.8 PSI220 cc/min120 RPM 1.8 PSI150 cc/min120 RPM 3.6 PSI220 cc/min120 RPM 3.6 PSI150 cc/min Alternate ring design achieved 39% greater slurry film thicknesscompared to an industry standard design ring Normalizing on slurry film thickness for both ring designs, slurryusage would be reduced 28% with an optimized ring slot design. Slurry film thickness in the pad/wafer interface region is greater asone moves away from the inner edge (Region A) <strong>of</strong> the ringPage 7ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

Videos <strong>of</strong> DEUVEF StudyEmbedded videos will not play in pdfformat. Please e-mail David Stockbowerat david_stockbower@entegris.com for therelevant files and informationStandard Slot <strong>Design</strong>Generation <strong>of</strong> Bow WaveExcess Slurry UsageNovel Slot <strong>Design</strong>Suppression <strong>of</strong> Bow WaveReduced Slurry UsageMethod proprietary to Araca, IncPage 8ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

A Costly Step - <strong>Ring</strong> Break-In <strong>Ring</strong>s break-in varies at endusers– Defects, wafer count, timedriven, PM cycle– Highly dependant on speed,pressure, fluid– Usually concurrent with padchange and break-in Absolutely necessary, but costly Working to correlate ringcondition to ring break-in– Edge effects– Polymer type & quality– Surface finishSum All Defects2000180016001400120010008006004002000No breakinDefecitvity comparison breakin vs No breakinSP1 0.16µDWOAfter breakinDNOPage 9ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

No RR Variation with Different PolymersNormalized Oxide Removal Rate Comparison Industry standard conditions atend user– Looking for drop in replacement– Exact same geometry, onlypolymer changed1.41.21.00.80.60.40.2 Post break-in, geometrydominates RR results– No obvious polymer effectPEEK PEEK PPS PEEK PEEK PPS<strong>Ring</strong> TypeRemoval Pr<strong>of</strong>ile Differing polymer rings with thesame preparation deliver similarwafer removalRemoval RateEnd user conditions proprietaryPPS H1 PPS H2 PEEK H3 PEEK H4Page 10ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

Same Geometry, Different Polymer, Lower Defect Same ring geometry, different polymer to isolate effect Results are TEOS monitor wafers, SP1 0.2 µm– Cu results are similar Molding methods, injection vs compression, could impact– <strong>Ring</strong> or pad particulation an area <strong>of</strong> investigationPage 11ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

Understanding Retaining <strong>Ring</strong> <strong>Effects</strong> <strong>Ring</strong> material choice impacts process conditions and results– Polymers generate varying thermal environments– <strong>Ring</strong>s mass alters down force on pad, wafer edge– Defect rates may be impacted by polymer or pad particulation– <strong>Ring</strong> preparation is critical for optimal performance <strong>Ring</strong> wear rates / lifetime correlated to polymer– Generally “harder” polymers last longer <strong>Ring</strong> and slot design can modulate slurry usage– Novel slot design suppresses bow wave,maintains slurry film thickness under wafer– Initial studies indicate 28% slurry saving– <strong>Ring</strong> geometry dictates removal rate and pr<strong>of</strong>ile Process optimization with static tool settings is difficult– Optimized ring designs can greatly reduce process COOPage 12ENTEGRIS PROPRIETARY AND CONFIDENTIAL, Published only with Permission

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