Post CMP Defects; Their Origin and Removal

Transcription

1 2007 Levitronix CMP Users Conference Post CMP Defects; Their Origin and Removal Jin-Goo Park Div. of Materials and Chemical Engineering, Hanyang University, Ansan , Korea February 15, 2007 KOTEF Lab of Excellence

2 Introduction to EMPL The Electronic Materials and Processing Laboratory (EMPL) started at Hanyang University in EMPL s research focus on the surface and colloidal phenomena in the area of semiconductor and electronic materials and processing. Cleaning CMP BioMEMS Laser Shock Cleaning Ozone Cleaning Single Type Megasonic Cleaning Post CMP Cleaning IPA Drying Metal CMP (Cu, Ru, Pt, Al and etc) Oxide and Poly-Si CMP ECMP Slurry Consumables Bio-Chip/MEMS Fabrication Mold Fabrication Surface Modification

3 Cleaning Research at Hanyang University Nano Particles Adhesion/Removal Mechanism Experimental/Theoretical Interpretation Quantitative/Qualitative Interpretation N Non-RCA Wet Chemistry Ozone Chelating agents Surfactants High k/low k cleanings N Nano-level Defect Free Cleaning Damage Free Dry Cleaning Laser Shock Cleaning Pattern Damage Force Measurements Process Drying Technology IPA/water solutions Marangoni Effects D Nano Surface Characterization Electrokinetic Adhesion force

4 EMPL Infra-Structure Cleanroom (Class 10, 100 Wet 2 and 1000) DI water Generator (500 lpm) IPA Dryer Brush Scrubber Megasonic Cleaner KLA-Tencor Particle Scanner, 6200 Nanometer Particle Scanner Atomic Force Microscopy Zeta-potential Analyzer 273 EG&G Potentiostat Cleaning Equip. Charactrization CMP Equip. E-CMP Polisher (4 ) CMP Polisher (6 ) Friction Polisher (4, 6 and 8 ) Samsung Hynix Intel, IBM Dongwoo MOICE KOSEF Doosan Siltron, LGM IMT KOTEF Lab of Excellence in Cleaning Nano-level Defect Free Wafer Cleaning Students (29) Ph.Ds: 4 Masters: 16 Undergrads: 8 Secretary: 1 Korea Cleaning UGM Korea CMPUGM

5 New Cleanroom Total Construction Space 1,800 sq ft 12,000 8,875 3,125 Wet Bench Wafer Brush Scrubber Wet Station Ozone Wet Station Smock Room 7,200 5,750 Laser Shock Cleaning System Optical microscope Fluorescence microscope Classroom (Class 10, EUV Controller ~700 sq ft) Chemical Stocker 1,450 Laminar Flow Hood & Surface Scan EUV Cleaning System AFM MCC U/T R.A S.A E.P.S. Fix Window

6 Outline Introduction to Wet Cleaning Post CMP Cleaning Effect of Slurry, Pads & Surfaces on Defects Slurry and Cleaning Solution Evaluation Summary

7 Next Generation Surface Preparation Issues Challenges Nanometer Feature Size New Materials Nanometer Thin Film Single Wafer Cleaning CMP Process EUVL Process 3D Device Clean without Etching - Non RCA (H 2 O 2 based) Chemistry Clean without Pattern Damage - No Megasonics and Brushes CMP Induced Defects Zero Defect on EUVL Mask 65nm poly Si lines

8 Semiconductor Cleaning Particle Organic contaminant Native oxide Interaction Force Attached Particle Metal Si Wafer Wet Cleaning ex) SC1, SC2, Piranha, HF etc Dry Cleaning ex) Laser shock cleaning, Plasma, Anhydrous HF, Jet Fluid, Cryogenic etc

9 Traditional Wafer Cleaning Chemicals SC-1(NH 4 OH+H 2 O 2 +H 2 O=1:1:5 at 80 ~ 90 C) - Particles and organic contamination removal SC-2(HCl+H 2 O 2 +H 2 O=1:1:5) at 80 ~ 90 C ) - Trace and Noble Metal removal Piranha(H 2 SO 4 :H 2 O 2 =4:1 at 90 ~ 120 C) - Organic Contamination removal and PR strip HF (+ H 2 O 2 ) : Last wet cleaning - HF : Native oxide and H 2 O 2 : Metal removal

10 Particle Adhesion Mechanism Physisorption (Van Der Waals Forces) E= - AR / 6H 2 Electrostatic Attraction Surface charge : Zeta-Potential 2 64πεRk T H ) = 2 e z V R ( 2 γ γ exp[ κh ] Chemisorption Chemical reaction between particles and surfaces Capillary Condensation F c = 4πRγ L

11 Particle Removal Mechanism Etching Few A /min/dissolution Dynamic Driving Force Mobility of liquid molecules Megasonic irradiation, Higher temperature, Hydrodynamic force Interaction Force Surface charge and Electrostatic repulsion Wettability of surfaces and particles

12 Metal Contamination Mechanism Electrochemical Deposition Redox Reaction O 3 + 2H + +2e - = O 2 +H 2 O H 2 O 2 + 2H + + 2e - = 2H 2 O Au + +e - = Au O 2 + 4H + + 4e - = 2H 2 O Ag + + e - = Ag Cu + + e - = Cu Cu e - = Cu 2H + +2e - = H 2 Pb e - = Pb Ni e - = Ni Fe e - = Fe SiO 2 + 4H + + 4e - = Si + 2H 2 O Al e - = Al Na + + e - = Na Ca e - = Ca K + + e - = K E (V vs. NHE) More Noble More Active Oxide Oxide Formation ΔH (kj/mol) Al 2 O 3-1,675 Cr 2 O 3 CrO 2 CrO 3-1, Fe 3 O 4-1,118 Fe 2 O SiO NiO -241 CuO -155 Tendency to be included in the oxide film

13 Metal Removal Mechanism Electrochemical Deposition Interruption of oxidation/reduction reaction Change of Eh and ph and complexation of ions Hydroxide Formation Surface modification and complexation Particle removal mechanism Film Inclusion Etching

14 CMP Process and Defects Polishing Pad Wafer Wafer Carrier Polishing Slurry Slurry Supply Slurry particles : SiO 2, Al 2 O 3, CeO 2 Rotating Platen CMP induced particles, metal ions Physical damages: scratch, pits, stress Chemical damages: corrosion

15 Requirements for Post CMP Cleaning Particle/Metal Removal Mechanism - No Damages Slurry/Cleaning Chemistry - Surface properties Post CMP Cleaning Particle/Metal Adhesion Mechanism - Specific contamination Post CMP Cleaning Equipments - Single/batch - Brush/Megasonic Copper CMP Cleaning - Low k integration - Corrosion

16 Defects Types in CMP Dishing / Erosion/N.U. Particles / Scratch Origins of these defects: Tool, Consumables, Substrate Materials

17 Random Particle Defects in WCMP Particle on surface and trench Slurry residue on dielectric Slurry residue in W-plug Organic particle Slurry residue in trench

18 Post CMP Scheme on W Plug for particle removal in trench for particle removal on surface film Pad fragment Organic particle Slurry residue Etch amount?? Trench pattern W-Plug Dielectric (SiO 2 )

19 Post CMP Cleaning Processes Clean configurations NH 4 OH HF Wet Wet Sand Indexer Dual Brush Module Rinse, Spin Dry Station

20 Shapes of Organic Defects after Poly CMP Ameba type defects on hydrophobic surface

21 Sources of Organic Residues

22 Hydrophobic Forces Net Free Energy at contact ΔG = ΔG LW + ΔG AB values (mn/m) for a number of interacting system according to Acid- Base theory The AB parameters for liquids were taken from van Oss. Silica was used as the model substrate. The force can be calculated using the Derjaguin approximation F/R=-2π(ΔG LW+AB ) More positive : More repulsive, More negative : More attractive Substrate Colloidal Probe Phi-Phi SiO Wafer Glass (30mm) Pho-Phi Silanated Glass Glass (15mm) Pho-Pho Silanated Glass Silanated Glass (15mm) Net Free Energy Liquid Pho-Pho Phi-Phi Phi-Pho Water Theoretical Calculation Adhesion Force Measurement Phil-Phil Repulsive Pho-Pho Phil-Pho Pho-Pho Attractive Phil-Pho Phil-Phil Ref. : Alexandre M. Freitas and Mukul M. Sharma, Journal of Colloid and Interface Science, 233, 73-82, (2001)

23 Contact Angle of Poly Si Wafer Treated with Sol. A Contact angle of poly Si decreased as function of Sol. A concentrations Slurry Modification to reduce defects Surface wettability change 80 Contact Angle ( Degree ) Contact Angle of Poly Si Wafer Concentration of H 2 O 2 ( vol % ) Concentration of Sol. A ( vol % )

24 Adhesion Force of Polymeric Particle on Poly Si Adhesion force measurement of pad particle on poly Si wafer surface at ph 11 (Spring constant : 0.03 N/m cantilever) ph 11 was adjusted by KOH Hydrophilic poly Si : Lower adhesion force than hydrophobic poly Si surface 16 Adhesion Force (nn) Adhesion Force of Polymer Particle HSol. 2 O 2 A 0% HSol. 2 O 2 A 1% HSol. 2 O 2 A 3% HSol. 2 O 2 A 10%

25 Frictional Force and Thermal Behavior on Poly Si CMP Friction Force (Kg f ) 25 SS 12 Slurry + H 2 O 2 addition 20 0 No vol Additive % H 2 O Lower vol % HAddtive 2 O 2 concent vol % H 2 O Medium addtive 2 concent. 10 vol % H 2 O Higher addivie 2 concnet Temperature ( SS12 SS12 SS12+1%Sol.A w/ + Lower 1%H2O2 additive SS12 SS12+3%Sol.A w/ + medium 3%H2O2 additive SS12 SS12+10%Sol.A w/ + higher 10%H2O2 additive con Time ( sec ) Time (Sec.) Contact Angle : 52 Contact Angle : <10 After CMP : Contact Angle of poly Si with SS12 slurry After CMP : Contact Angle of poly Si with slurry and Sol. A mixture solution

26 FESEM Images of Polymeric Particle Contamination on Poly Si 1 min dipping in alkaline KOH solutions which have abraded pad particles, and then dried in N 2 atmosphere at 60 C Abraded Pad Particle No additive (KOH, ph 11), Hydrophobic Surface (KOH + lower additive ), Hydrophilic Surface (KOH + medium additive ), Hydrophilic Surface (KOH + higher additive), Hydrophilic Surface

27 Defect Maps with Modified Slurry

28 Effect of Polishing Byproducts on CMP Polish-Byproduct or Stain on Pad in Cu CMP Slurry chemistry induced defects Typical form of stains caused by polish byproducts on the pad The effects of stains on CMP performance such as erosion, dishing and non-uniformity were evaluated No removal by DI buffing

29 Effect of Byproducts on Polishing - RR, Erosion, Selectivity and Dishing Removal Rate (A /min) Removal Rate Non Uniformity N.U(%) Number of Wafer

30 Temperatures and Friction Temperature ( ) Friction Force (A.U.) Slurry A Slurry B Polishing Time (sec) Time (sec)

31 Interaction Forces between Wafer and Surface In liquid media wafer particle Total Interaction Force Electrostatic Force Total Interaction Force Van der Waals Force van der Waals Force (Particle s size ) - Attractive + Electrostatic Force (Zeta Potential) + Repulsive or - Attractive : Key factor controlling deposition

32 Adhesion Force Measurements Fabricated Colloidal Probe Force-Distance Curve by AFM 50 μm 2 μm Polystyrene particle (2 μm)

33 Measured Interaction Forces Using AFM Force-Distance Curve Measurements with Silica particle Interaction force (nn) ph 11 slurry ph 7 slurry ph 3 slurry 0.0 SILK TEOS Cu TaN SiLK TM TEOS Cu TaN Wafers Park et. al., J. Electrochem. Soc., 150 (5), pp. G327-G322 (2003)

34 Particle Contamination After Polishing ph 11 ph 7 ph 3 Cu TaN TEOS SiLK

35 Adhesion Force in Cleaning Solutions The least adhesion force of silica is measured in the citric acid and BTA with NH 4 OH The largest adhesion force is measured in the citric acid and BTA with TMAH The ph and its adjustor selection are very important in cleaning solution design Adhesion Force ( log N ) Adhesion Force D.I Citric acid+bta Citric acid+bta+nh4oh Citric acid+bta+tmah (ph2) (ph6) (ph6) Park et. al., J. Electrochem. Soc., 151(10), pp. G327-G322 (2004)

36 FESEM Images of Cu Surfaces after Polishing - Large numbers of residual particles are observed on Cu surfaces cleaned in DI water, citric acid only solution, and citric acid solution with TMAH - Citric acid and BTA solution with NH 4 OH shows the complete removal of particles Pre-Cleaned Cu Contaminated Cu D.I water Citric acid with BTA Citric acid BTA with NH 4 OH Citric acid BTA with TMAH

37 Removal Rates in Alumina and Silica slurry - Slurry evaluation: RR, friction and adhesion force measurements Removal rate (A /min) Removal rate of Cu DI+Alumina DI+Silica Citric+Alumina Citric+Silica Park et. al., J. Electrochem. Soc., 153(1), pp. H36-H40 (2007)

38 Friction Forces in Alumina and Silica slurry - In DI water, higher friction in alumina - In citric acid, higher friction in silica - The higher the adhesion force, the higher the friction force Friction ( Kgf ) DI Water + Alumina DI Water + Silica Friction ( Kgf ) Citric Acid + Alumina + H 2 O 2 + NH 4 OH, ph6 Citric Acid + Silica + H 2 O 2 + NH 4 OH, ph Time (Sec.) Time (Sec.)

39 Adhesion Forces of Alumina on Cu in Slurries 6.00E-009 Adhesion Force ( N ) 5.00E E E E-009 DI Water Citric Acid+NH 4 OH Cu Wafer - Particle Adhesion 1.00E-009 Silica Alumina Silica Alumina

40 Scratches and Defects in Alumina and Silica Slurry Higher friction/adhesion force DI - Alumina DI - Silica Cit - Alumina Lower friction/adhesion force Cit - Silica

41 Summary Origin of Defects - Tool, Consumables, Surfaces Consumables - Slurry, Pad Related Surfaces - Wettability - Metallic vs. Non-metalic Slurry and cleaning solution modification Evaluation of Slurry and Cleaning Solutions -Adhesion force - Friction force

42 Acknowledgements Fundings from MOICE, KOSEF, MOST Samsung, Hynix, Intel Doosan, Siltron, IMT Lab of Excellence Program Through MOE, MOCIE and MOLAB Post Brain Korea 21 Program through MOE AND

43 Members of EMPL at Hanyang University