1 3 rd Annual SFR Workshop Review May

1 3 rd Annual SFR Workshop & Review, May 24, 2001 8: 30 – 9: 00 – 9: 45 – 10: 30 – 10: 45 – 12: 00 – 1: 45 – 2: 30 – 2: 40 – 3: 30 – 4: 30 – 9: 00 9: 45 10: 30 10: 45 12: 00 1: 45 2: 30 2: 45 4: 30 5: 30 5/24/2001 Research and Educational Objectives / Spanos CMP / Doyle, Dornfeld, Talbot, Spanos Plasma & Diffusion / Graves, Lieberman, Cheung, Haller break Poster Session / Education, CMP, Plasma, Diffusion lunch Lithography / Spanos, Neureuther, Bokor Sensors & Controls /Aydil, Poolla, Smith, Dunn, Cheung, Spanos Break Poster Session / all subjects Steering Committee Meeting in room 373 Soda Feedback Session

2 Chemical Mechanical Planarization SFR Workshop & Review May 24, 2001 David Dornfeld, Fiona Doyle, Costas Spanos, Jan Talbot Berkeley, CA 5/24/2001

3 CMP Milestones • September 30 th, 2001 – Build integrated CMP model for basic mechanical and chemical elements. Develop periodic grating metrology (Dornfeld, Doyle, Spanos , Talbot). Model Outline Progressing- initial Chemical and Mechanical Modules in Development • September 30 th, 2002 – Integrate initial chemical models into basic CMP model. Validate predicted pattern development. (Dornfeld, Doyle, Spanos , Talbot). • September 30 th, 2003 – Develop comprehensive chemical and mechanical model. Perform experimental and metrological validation. (Dornfeld, Doyle, Spanos, Talbot) 5/24/2001

4 Abstract 2002 Milestone: Integrate initial chemical models into basic CMP model. Validate predicted pattern development. Key areas involved in this are: • Chemical Aspects of CMP (Talbot and Gopal) • Glycine effects on CMP & chemical effect on abrasion (Doyle and Asku) • Material Removal in CM P: Effects of Abrasive Size Distribution and Wafer-Pad Contact Area (Dornfeld and Luo) • Fluid/Slurry Flow Analysis for CMP Model (Dornfeld and Mao) • Fixed Abrasive Design for C MP (Dornfeld and Hwang) • CMP Process Monitoring using Acoustic Emission (Dornfeld and Chang) • Establishing full-profile metrology for CMP modeling (Spanos and Chang) Recent activities in yellow will be reviewed here 5/24/2001

5 Overview Model Structure & Development Chem Mech Chemical Aspects Mechanical Aspects Fluid Aspects Pad Surface Effects Process Monitoring Grating Metrology Process control 5/24/2001 X X Basic Process Mechanism Model Validation Metrology, Process Control, & Optimization X X X X

6 Model development scenario • Identify key influences of chemical and mechanical activity • Experimental analysis of influences in parallel with model formulation for “module” development • Identification of “coupling” elements of mechanical and chemical activity • Build “coupling” elements into integrated model • Full scale model verification by simulation and test • Strategies for model-based process optimization 5/24/2001

7 Focus of this presentation • Review of progress in understanding the role of chemistry in CMP • Update on process monitoring activity • Full-profile metrology for CMP modeling • Details of these and other key areas in posters 5/24/2001

8 Review - Overview of Integrated Model Pad Roughness Pad Hardness Chemical Reaction Model (RR 0)chem Wafer Hardness Fluid Model Slurry Concentration, Abrasive Shape, Density, Size and Distribution Down Pressure Slurry Chemicals Relative Velocity Model of Active Abrasive Number N Model of Material Removal VOL by a Single Abrasive Physical Mechanism; MRR: N´VOL Preston’s Coefficient Ke Dishing & Erosion 5/24/2001 Surface Damage Wafer, Pattern, Pad and Polishing Head Geometry and Material Contact Pressure Model Pressure and Velocity Distribution Model (FEA and Dynamics) (RR 0 )mech WIWNU MRR WIDNU

9 Chemical Aspects of CMP Role of Chemistry • Chemical and electrochemical reactions between material (metal, glass) and constituents of the slurry (oxidizers, complexing agents, p. H) – Dissolution and passivation • Solubility • Adsorption of dissolved species on the abrasive particles • Colloidal effects • Change of mechanical properties by diffusion & reaction of surface 5/24/2001

10 Modeling of Chemical Effects • Electrochemical/chemical dissolution and passivation of surface constituents • Colloidal effects (adsorption of dissolved surface to particles or re-adsorption) • Solubility changes • Change of mechanical properties (hardness, stress) 5/24/2001

Copper Interconnection using Chemical Mechanical Planarization (CMP) Fiona Doyle and Serdar Asku How Glycine Changes Electrochemistry of Copper? Ø Comparison of Cu Behavior in Aqueous Solutions with and without Glycine in terms of v Potential-p. H Diagrams v Polarization Experiments How Electrochemical Behavior Changes under Abrasion Ø In-situ Electrochemical Experiments during Polishing using Slurries/ Solutions with or without Glycine v In-situ Polarization Experiments v In-situ Monitoring of Open Circuit Potential (EOC) Conclusions Experimental Results and Their Comparison with the Theoretical Diagrams

12 Copper Interconnection with CMP DUAL DAMASCENE PROCESS Trench Si. O 2 Via Etch Si. N Deposit Barrier Copper Fill CMP CHEMICAL MECHANICAL PLANARIZATION Pressure Carrier Slurry feeder Wafe r SLURRY • Abrasive particles • Chemicals ALUMINA PARTICLES w/ Average Size ~ 120 nm From EKC Tech. Rotation Polishing Plate Patterned wafer POLISHING PAD Cross-sectional View of SUBA 500 Pad, Rodel Corp. (Taken from Y. Moon’s Ph. D Thesis) 5/24/2001 Pad Polishing pad asperities

13 Objective and Methods In Copper CMP, Electrochemical and Mechanical Mechanisms are not Well Understood Slurries are formulated empirically at present Develop a Fundamental Basis for the Behavior of Slurries with Complexing Agents Ø Tertiary Potential-p. H Diagrams Ø Polarization Experiments using Cu Rotating Disk Electrode Ø In-situ Electrochemical Experiments during Polishing 5/24/2001

14 Experimental Techniques Rotating Disk Electrode Rotating Cu Disk electrode Fritted glass gas bubbler Rotator Frame w Luggin Probe & Reference Electrode Magnetic stirrer Pt Counter Electrodes P Slurry pool Copper Working Electrode Polish pad In-situ Electrochemical Experiments 5/24/2001

15 Cu. T=10 -5 Cu-H 2 O System RDE 200 rpm Scan Rate 2 m. V/sec 5/24/2001 p. H and p. H Buffer System EOC (m. V vs. SHE) i. OC (A/cm 2) 4, With Acetate Buffer + 10 -2 M Na 2 SO 4 196 4. 43 x 10 -6 9, With Carbonate Buffer + 10 -2 M Na 2 SO 4 102 3. 23 x 10 -6 12, No Buffer 24 2. 17 x 10 -6

16 Cu. T=10 -5 ; LT=10 -2 Cu-H 2 O-Glycine System RDE 200 rpm Scan Rate 2 m. V/sec 10 -2 M Glycine 5/24/2001 p. H and p. H Buffer System EOC (m. V vs. SHE) i. OC (A/cm 2) 4, With Acetate Buffer + 10 -2 M Na 2 SO 4 186 6. 41 x 10 -6 9, No Buffer + 10 -2 M Na 2 SO 4 -26 1. 04 x 10 -5 12, No Buffer -65 1. 21 x 10 -5

17 Cu-H 2 O-Glycine System (De-aerated) Cu. T=10 -5 ; LT=10 -2 p. H=10 Cu. T=10 -4 ; LT=10 -1 p. H=9 p. H=11 p. H=12 p. H=10 p. H=11 p. H=12 5/24/2001

18 In-Situ Polarization at p. H=4 No Glycine RDE/ IN-SITU 200 rpm 27. 6 k. Pa Scan Rate 2 m. V/s Chemical Composition Acetate Buffer 10 -2 M Na 2 SO 4 No Glycine Acetate Buffer 10 -2 M Na 2 SO 4 10 -2 M glycine 5/24/2001 10 -2 M Glycine EOC (m. V vs. SHE) 196 i. OC (A/cm 2) 4. 43 x 10 -6 Polishing w/ pad only 191 4. 69 x 10 -6 Polishing w/ pad + 5 wt % Al 2 O 3 188 6. 18 x 10 -6 No abrasion 186 6. 41 x 10 -6 Polishing w/ pad only 183 7. 33 x 10 -6 Polishing w/ pad + 5 wt % Al 2 O 3 181 1. 16 x 10 -5 Abrasion Type No abrasion (RDE)

19 In-Situ Polarization at p. H=9 No Glycine RDE/ IN-SITU 200 rpm 27. 6 k. Pa Scan Rate 2 m. V/s 5/24/2001 Chemical Abrasion Type Composition Carbonate Buffer No abrasion (RDE) 10 -2 M Na 2 SO 4 Polishing w/ pad only No Glycine Polishing w/ pad + 5 wt % Al 2 O 3 No Buffer No abrasion 10 -2 Na 2 SO 4 Polishing w/ pad only 10 -2 M glycine Polishing w/ pad + 5 wt % Al O 2 3 10 -2 M Glycine EOC (m. V vs. SHE) 102 92 46 -26 -32 i. OC (A/cm 2) 3. 23 x 10 -6 5. 18 x 10 -6 4. 09 x 10 -5 1. 04 x 10 -5 1. 28 x 10 -5 -33 2. 87 x 10 -5

20 In-Situ Polarization at p. H=12 No Glycine RDE/ IN-SITU 200 rpm 27. 6 k. Pa Scan Rate 2 m. V/s Chemical Abrasion Type Composition No Buffer/Na 2 SO 4 No abrasion (RDE) DD Water with Polishing w/ pad only No Glycine Polishing w/ pad + 5 wt % Al 2 O 3 No Buffer No abrasion No Na 2 SO 4 Polishing w/ pad only 10 -2 M glycine Polishing w/ pad + 5 wt % Al 2 O 3 5/24/2001 10 -2 M Glycine EOC (m. V vs. SHE) i. OC (A/cm 2) 23 2. 17 x 10 -6 12 4. 83 x 10 -6 -140 9. 72 x 10 -6 -68 1. 21 x 10 -5 -75 3. 42 x 10 -5 -163 8. 62 x 10 -5

21 In-Situ OC Potential Measurements Without Glycine 5/24/2001 With 10 -2 M Glycine

22 Conclusions • Polarization results well correlated with potential-p. H diagrams • No significant changes in in-situ polarization for active behavior • Mechanical components significantly affected in-situ polarization for active-passive behavior • Kaufman’s tungsten CMP model is also valid for Cu CMP • Glycine (complexing agents) may enhance the polishing efficiency. 5/24/2001

23 Future Work-I Determination of Chemical (Electrochemical) and Mechanical Contributions v Maintain a Constant Level Of In-Situ Polarization, Measure Current v CHEMICAL CONTRIBUTION from Time-Averaged Current v POLISH RATE from Weight Loss v MECHANICAL CONTRIBUTION from the Difference Generation of Chemical, Mechanical and Total Removal Rate versus Polarization Plots at Different p. H’s. 5/24/2001

24 Future Work-II In-Situ Electrochemical Experiments using “Patterned” Cu Electrodes v In-Situ Polarization Experiments v Polishing at a Constant Level of Polarization v Surface Examination of Passive Films XPS, Auger Spectroscopy Verification of Kaufman’s Model using “Patterned” Cu Electrodes 5/24/2001

25 Process Monitoring of CMP using Acoustic Emission Andrew Chang UCB Motivation • • • Endpoint Detection - The characteristics of the acoustic emission signal from various materials can be easily discernable during the polishing process. - Outside noise sources, once characterized, can be minimized and filtered from disturbing the process signal. Scratch Detection - Scratches and/or other mechanically induced flaws (large agglomeration of particles, contaminants on the pad, etc. ) can be detected and used as feedback for purposes of real-time process control. Abrasive Slurry Design - Energy of the AE signal can be correlated to the active number of abrasive particles during polishing for slurry concentration optimization 5/24/2001

26 Acoustic Emission Propagation in the Wafer Schematic view of abrasive particles during polishing (exaggerated view) Wafer carrier Abrasives in slurry Sensor Oil film couplant Carrier ring Pad Polishing plate Wafer 5/24/2001 Individual burst emission waves generated by abrasive particles contacting wafer produce a continuous acoustic emission source.

27 Experimental Setup Pre-amplification & Primary amplification PC Data Acquisition Raw AE Raw Sampling Rate = 2 MHz Signal Conditioning (60 -100 d. B) CMP Tool Toyoda Float Polishing Machine Test Wafers Bare silicon & copper blanket wafers Slurry type ILD 1300, abrasive size (~100 nm) Alumina slurry, abrasive size (~100 nm) Pad type IC 1000/Suba IV stacked pad Polishing Conditions Pressure = ~ 1 psi Table Speed = 50 RPM Wafer Carrier Speed = Stationary Slurry flowrate = 150 ml/min 5/24/2001

28 Raw Acoustic Emission from CMP Process Low frequency noise due vibrations from table motor, pad pattern effects, etc. 5/24/2001 Filtered raw signal containing high frequency AE content

29 Establishing full-profile metrology for CMP modeling Costas Spanos & Tiger Chang UCB Substrate Oxide • Use scatterometry to monitor the profile evolution • The results can be used for better CMP modeling 5/24/2001

30 Mask Designed to explore Profile as a function of pattern density • The size of the metrology cell is 250 m by 250 m • Periodic pattern has 2 m pitch with 50% pattern density 5/24/2001

31 Sensitivity of Scatterometry (GTK simulation) • We simulated 1 m feature size, 2 m pitch and 500 nm initial step height, as it polishes. • The simulation shows that the response difference was fairly strong and detectable. 5/24/2001

32 Characterization Experiments Completed Wafer # Down Force (psi) Table Speed (rpm) Slurry Flow (ml/min) 1 4 40 50 2 8 40 50 3 4 40 150 4 8 40 150 5 8 80 50 6 4 80 50 7 8 80 150 8 4 80 150 9 6 60 100 11 6 60 100 5/24/2001 Initial profiles Sopra/AFM CMP AFM (AMD/SDC) • Three one-minute polishing steps were done using the DOE parameters Wafer cleaning Nanospec Thickness measurement Sopra Spectroscopic ellipsometer

33 Library-based Full-profile CMP Metrology Five variables were used in to generate the response library: bottom oxide height (A), bottom width (B), slope 1 (C), slope 2 (D) and top oxide height (E). C D E oxide B A Substrate Reference: X. Niu, N. Jakatdar, J. Bao, C. Spanos, S. Yedur, “Specular spectroscopic scatterometry in DUV lithography”, Proceedings of the SPIE, vol. 3677, pt. 1 -2, March 1999. 5/24/2001

34 Full Profile CMP Results, so far SEM AFM Scatterometry • Extracted profiles match SEM pictures within 10 nm • Scatterometry is non-destructive, faster and more descriptive than competing methods. • Next challenge: explore application in wet samples. 5/24/2001

35 Conclusions • Chemical effects model and synergy with mechanical effects being developed and validated • Mechanical effects model validated for abrasive size and activity and wafer-pad contract area • Fabrication technique for micro-scale abrasive design experiments • Sensing system for process monitoring and basic process studies being validated • Scatterometry metrology sensitivity study indicates suitability for observing profile evolution 5/24/2001

36 2002 & 2003 Goals Develop comprehensive chemical and mechanical model. Perform experimental and metrological validation, by 9/30/2003. • Simulation of Integrated CMP model • Experimental verification of integrated CMP model (role of chemistry elements, mechanical elements in mechanical material removal) 5/24/2001