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Semitool Confidential

Copper Damascene Plating 1/5/06 Brandon Brooks Process Development Engineer. Semitool Confidential. Outline Why Cu Interconnects? Damascene Process Flow Parameters Affecting Cu Interconnects Backside Clean and Bevel Etch. Damascene Plating?. Why Cu Interconnects?. Best!. Al. Cu.

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Semitool Confidential

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  1. Copper Damascene Plating 1/5/06 Brandon Brooks Process Development Engineer Semitool Confidential

  2. Outline • Why Cu Interconnects? • Damascene Process Flow • Parameters Affecting Cu Interconnects • Backside Clean and Bevel Etch

  3. Damascene Plating?

  4. Why Cu Interconnects? Best! Al Cu  Resistivity  Melting Point • Thermal Expansion • Electromigration  Resistivity  Melting Point • Thermal Expansion • Electromigration Interconnect Metal Properties * Alloy (Si, Cu)

  5. Why Cu Interconnects? Interconnect Metal Properties Cu has a very slow etch rate • Cu halides are solid at normal temperatures Changing from Al to Cu interconnects requires new process flow • Enter Damascene plating

  6. Damascene Process Flow Today’s Main Topics Typical Damascene Process Flow • Dielectric Deposition • Photoresist Deposition • UV Exposure • Develop Photoresist • Etch Dielectric • Remove Photoresist • Barrier Deposition • Seed Layer Deposition • Electrochemical Deposition (ECD) • Backside Clean and Bevel Etch • Anneal • Chemical Mechanical Polish (CMP) • Repeat Steps 1-10 for Every Metal Layer

  7. Damascene Process Flow

  8. Copper Interconnect Parameters Key Factors Affecting Cu Interconnect Performance • Gap-Fill • CD Uniformity • Overburden • Anneal AMD’s 9 Cu Levels

  9. Copper Interconnect Parameters: Gap-Fill 0.12m, 8.3:1AR Trenches Key Parameters for Gap-Fill • Seed and Barrier Layers • Uniformity • Thickness • Plating Recipe • Hot Start (Initiation) • Fill Current Density • Waveform • Plating Chemistry • Inorganic • Organic

  10. Copper Interconnect Parameters: Gap-Fill Physical Vapor Deposition (PVD) Effects Seed and Barrier Layers

  11. Copper Interconnect Parameters: Gap-Fill Seed and Barrier Layer Uniformity Edge Shadowing Optimized Seed Layer

  12. Copper Interconnect Parameters: Gap-Fill 0.30micron, 4.8:1 AR Vias 0.30micron, 4.8:1 AR Vias 1500Å Total Seed Thickness 2000Å Total Seed Thickness Seed and Barrier Layer Thickness

  13. Copper Interconnect Parameters: Gap-Fill 2X Fill Rate on the 2V Hot Start No Hot Start 2V Hot Start Plating Recipe Hot Start 0.180 m Line Width Trenches 48 Coulombs ECD

  14. Copper Interconnect Parameters: Gap-Fill The Effect of Current Density upon Gap Fill Optimum Fill for feature D Good 0.35μm, 4.3:1 AR Vias 0.35μm, 4.3:1 AR Vias Optimum Current Current too Low Gap Fill Bad Low High 0.18μm, 5.1:1 AR Trench Current Density 0.18μm, 5.1:1 AR Trench Optimum Current Current too High Plating Recipe Current Density

  15. Copper Interconnect Parameters: Gap-Fill Plating Recipe Waveform DC plating provides better additive adsorption Pulsed plating provides better Cu diffusion

  16. Copper Interconnect Parameters: Gap-Fill Plating Chemistry Organic Components • Suppressor (PEG) • Accelerator (SPS) • Leveler (Amine) Inorganic Components • Copper Sulfate (CuSO4) • Hydrochloric Acid (HCl) • Sulfuric Acid (H2SO4)

  17. Copper Interconnect Parameters: Gap-Fill Low Copper Copper Effect on Gap Fill High Copper Inorganic Plating Chemistry

  18. Copper Interconnect Parameters: Gap-Fill Chloride Effect on Gap-Fill Inorganic Plating Chemistry

  19. Copper Interconnect Parameters: Gap-Fill pH 3 Acid Effect on Gap Fill pH 2 Inorganic Plating Chemistry pH 2

  20. Copper Interconnect Parameters: Gap-Fill Organic Plating Chemistry • Accelerator • Catalytic effect • Requires very small amount of Cl- • Increased current for a given potential • Suppressor • Suppresses deposition • Requires Cl- to adsorb onto copper surface • Decreases current for a given potential • Leveler • Suppresses deposition at high current density areas • Very low concentration (diffusion limited) Organic Effect on Gap Fill

  21. Copper Interconnect Parameters: Gap-Fill Stripping Region A C Plating Region B Organic Plating Chemistry Cyclic Voltammetric Stripping Analysis (CVS) A = VMS B = VMS + Suppressor C = VMS + Sup. & Accel. I V

  22. Copper Interconnect Parameters: Gap-Fill Worse Better High Acid 150 g/l 30 0.3 25 20 0.2 80 g/l H2SO4 Stripping Area Stripping Area 15 Low Acid (10g/l) 10 0.1 80 g/l 5 High Acid 150 g/l 0 0 Better Worse 0 1 2 3 4 5 0 0.01 0.02 0.03 0.04 0.05 Accelerator Concentration Suppressor Concentration Organic Plating Chemistry

  23. Copper Interconnect Parameters: Gap-Fill Organic Plating Chemistry

  24. Copper Interconnect Parameters: Gap-Fill Organic Plating Chemistry

  25. Copper Interconnect Parameters: Gap-Fill Organic Plating Chemistry

  26. Copper Interconnect Parameters: Gap-Fill Organic Plating Chemistry

  27. Copper Interconnect Parameters: Gap-Fill Organic Plating Chemistry

  28. Copper Interconnect Parameters: Gap-Fill Organic Plating Chemistry

  29. Copper Interconnect Parameters: CD Uniformity Key Parameters for Current Density Uniformity • Chemistry • High Acid • Low Acid • CFD Reactor • Electric Field Control Intel: 8 Cu Levels

  30. Copper Interconnect Parameters: CD Uniformity e- e- e- e- Cu2+ Cu2+ Generalized Electrochemical Schematic Electrolytic Copper Deposition Ammeter V0 + Current Density = Current Surf. Area Current Path Electrolyte Surface Area Cu0 Cu2++2e- Cu2++2e- Cu0 Cathode (Reduction) Anode (Oxidation)

  31. Copper Interconnect Parameters: CD Uniformity Rcat Rcat 1/Seed Thickness Cathode (Thin) Rcat  Wafer Radius Relec Relec Relec  1/Bath Conductivity V + Electrolyte Ranode= 0 Anode (Thick) = Area = Surface Area

  32. Copper Interconnect Parameters: CD Uniformity How To Make Small? Rcat Cathode (Thin) Relec Relec V + Center I Loop Edge I Loop Electrolyte Anode (Thick) Ranode= 0 • V • Current Density • Throughput • Rcat • Seed Layer Thickness • Wafer Radius • Relec • Bath Conductivity

  33. Copper Interconnect Parameters: CD Uniformity Conductivity at Various Bath Conditions 600 “High” Acid 500 511 400 300 Conductivity (mS/cm) 200 247 “Low” Acid 100 70 0 10 g/l H2SO4 50 g/l Cu 80 g/l H2SO4 50 g/l Cu 175 g/l H2SO4 17 g/l Cu

  34. Copper Interconnect Parameters: CD Uniformity 0sec 5sec Plating Time 15sec 30sec 60sec Current Density 120sec (0,0) Wafer Radius Terminal Effect

  35. Copper Interconnect Parameters: CD Uniformity The Effect of Current Density upon Gap Fill Optimum Fill for feature D Good 0.35mm, 4.3:1 AR Vias 0.35mm, 4.3:1 AR Vias Optimum Current Current too Low Gap Fill Bad Low High 0.18mm, 5.1:1 AR Trench Current Density 0.18mm, 5.1:1 AR Trench Optimum Current Current too High

  36. Copper Interconnect Parameters: CD Uniformity Are the center and edge receiving the same process?

  37. Copper Interconnect Parameters: CD Uniformity Independent of Rc and Relec Cathode V1 and V2 adjusted until V1 V2 + + Anode 2 Anode 1 Advanced Reactor Design: Multiple Anodes Robust system that can handle multiple chemistries Built for the future with the ability to handle shrinking die size Cost effective ability to handle increasing wafer diameters

  38. Copper Interconnect Parameters: CD Uniformity Conventional Reactor CFD Reactor Wafer Electrolyte Virtual Anodes Electrolyte Physical Anodes Dielectric

  39. Copper Interconnect Parameters: CD Uniformity Rotating Wafer Overflow Electrolyte Virtual Anode Bubble Trap Dielectric Concentric Annular Anodes Flow Inlet

  40. Copper Interconnect Parameters: CD Uniformity Superposition of Electric Field Summed Field Anode 2 Normalized Voltage at Cathode (V) Anode 3 Anode 1 Anode 4 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 Wafer Diameter (mm)

  41. Copper Interconnect Parameters: CD Uniformity 0sec 34 133% <5% 5sec 30 15sec Current Density (mA/cm^2) 26 30sec 60sec 22 120sec 18 14 0 25 50 75 100 125 150 20% <5% 34 30 Current Density (mA/cm^2) 26 0sec 22 18 120sec 14 0 25 50 75 100 125 150 100 nm Seed layer, 1m deposition SEMITOOL - CFD Conventional High Acid 511mS/cm Low Acid 70mS/cm Wafer Radius (mm)

  42. Copper Interconnect Parameters: CD Uniformity Dynamic Compensation for Constant Current Density 2.5 Anode 1 Anode 3 2.0 Anode Current (Amps) Anode 4 Anode 2 1.5 1.0 0 20 40 60 80 100 120 Deposition Time (sec)

  43. Copper Interconnect Parameters: Overburden Key Parameters for Overburden • Local Overburden (Overplating) – Fill Step • Chemistry • 3-Component • 2-Component • Waveform • Direct Current • Pulse Reverse • Global Overburden – Cap Step • Chemistry • High Acid • Low Acid • CFD Reactor

  44. Copper Interconnect Parameters: Local Overburden Step Up No Step Up Pulse Reverse POR 2-Component Organic Package High Acid Electrolyte Direct Current POR 3-Component Organic Package Moderate Acid Electrolyte

  45. Copper Interconnect Parameters: Local Overburden Insufficient Leveler Overplating Post-CMP Residual Cu Optimized Organic Conditions No Post-CMP Residual Cu Planar Deposition

  46. Copper Interconnect Parameters: Global Overburden Radial control of Thickness Variation (Å) 800Å 600 400 200 0 -200 -400 -600 -800 -100mm 0 100 Cu Thickness (Å) Wafer Diameter (mm)

  47. Copper Interconnect Parameters: Global Overburden Raider CFD Profile Before & After 30s CMP 16,000 12,000 CFD Profile before CMP Thickness (A) 8,000 Uniform Post-CMP Profile Profile after 30s CMP 4,000 POR Profile Before & After 30s CMP 16,000 POR Profile before CMP 12,000 Thickness (A) Early Clearing! 8,000 Profile after 30s CMP Edge Residual! 4,000 Wafer Diameter

  48. Copper Interconnect Parameters: Global Overburden CMP Profile Matching

  49. Copper Interconnect Parameters: Anneal Key Parameters for Anneal • Temperature • Feature Size • Barrier Layer

  50. Copper Interconnect Parameters: Anneal As Deposited Small Grains Self Annealed Large Grains Thermally Annealed Effect of Temperature

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