Almost Complete Removal of Sub-90 nm Ceria Particles from Silicon Dioxide Surfaces Jihoon Seo, Akshay Gowda, and S.V. Babu

Transcription

1 Almost Complete Removal of Sub-90 nm Ceria Particles from Silicon Dioxide Surfaces Jihoon Seo, Akshay Gowda, and S.V. Babu The Center for Advanced Materials Processing (CAMP), Clarkson University 1

2 1. Introduction 2. Physico-chemical Properties of Ceria Particles with different sizes : Contamination and Cleaning 3. H 2 O 2 -NH 4 OH Mixtures and Their Optimization 4. Investigation of Mechanism of the Cleaning of Ceria Particles using H 2 O 2 -based Alkaline Solutions from Silicon Dioxide Surfaces 5. Summary 2

3 Calcined Ceria Colloidal Ceria Smaller Smaller median size ~110nm median size ~90nm median size ~30nm median size ~10nm ᆞHigh SiO 2 removal rate ᆞHigh crystallinity ᆞTunable particle size ᆞMass production ᆞFacet shape ᆞPoor size distribution ᆞRelatively high scratch ᆞUniform size distribution ᆞSpherical shape ᆞLow scratch ᆞHigh cost ᆞRelatively Low SiO 2 RR J. Seo,et al., ACS Appl Mater Inter, 2014, 6, J. Seo, in 21st International Symposium on Chemical-Mechanical Planarization, Lake Placid, NY, USA,

4 Size-dependent surface chemistry of ceria Adsorption of silicate ion on ceria surface 6 S- Q e (mg/m 2 ) M- L C e (mg/l) Adsorption constant K F 1/n R 2 S M L J. Seo,et al.,applied Surface Science, 2016, 389,

5 6

6 1. Introduction 2. Physico-chemical Properties of Ceria Particles with different sizes : Contamination and Cleaning 3. H 2 O 2 -NH 4 OH Mixtures and Their Optimization 4. Investigation of Mechanism of the Cleaning of Ceria Particles using H 2 O 2 -based Alkaline Solutions from Silicon Dioxide Surfaces 5. Summary 6

7 S BET (m 2 /g) d a BET (nm) d b TEM (nm) d c DLS (nm) Ce 3+ (%) 10 nm-ceria nm 10 nm 36 nm 26.3 % 30 nm-ceria nm 29 nm 81 nm 18.4 % 90 nm-ceria nm 104 nm 193 nm 15.0 % Table. Physicochemical properties of ceria particles with different sizes. a Obtained from Solvay. b Calculated from TEM image. c Measured using DLS method 7 J. Seo, A. Gowda, and S.V. Babu., ECS J Sold State SC, Submitted (2018)

8 1 st ) Preparation of contaminated coupon SiO 2 coupon 2 nd ) Cleaning with our solutions in ultra-sonication bath Slurry 0.05 wt% Volume: 100 ml Conditions Sample size: 1 x 1 cm 2 Time: 300 rpm Temperature : 25 o C DIW rinsing SiO 2 coupon AFM measurements Park Systems (XE-300P) Non-Contact with NCHR Scan rate 0.5 Hz DIW rinsing Ultrasonic Baths Cleaning solutions Volume: 100 ml Conditions Sample size: 1 x 1 cm 2 Time: 60s Temperature : 25 o C Power : 75 W, Frequency: ~40 khz Coupon Cleaning efficiencies (CE) = Particle (initial) Particle (residual) 8 Particle (initial)

9 SC1 solution consisting of 1:1:5 (v/v/v) mixture of NH 4 OH (30 wt%)/h 2 O 2 (30 wt%)/diw Number of ceria particles before and after SC1 Cleaning Number of adsorbed particles Before SC1 Cleaning After SC1 Cleaning Count area: 10 x 10 μm nm 30 nm 90 nm Before SC1 Cleaning 10nm: 1 x 1 µm particles 30nm: 2 x 2 µm particles 90nm: 10 x 10 µm 2 After SC1 Cleaning 187 particles 102 particles 118 particles 7.0 particles (initial) (residual) Cleaning Efficiency (CE): 100 (initial) Number of ceria particles in scan area 9 J. Seo, A. Gowda, and S.V. Babu., ECS J Sold State SC, Submitted (2018)

10 Design of experiments (DOE) Sample Number Volume % mixture H 2 O 2 NH 4 OH DIW Fitting model, Y = σ3 i=1 β i x i + σ σ3 i<j β ij x i x j + σ σ3 i<j H 2 O 0.75 S 3 δ ij β ij x i x j (x i x j ) + β 123 x 1 x 2 x 3 x 1 (30 wt% H 2 O 2 ), x 2 (30 wt% NH 4 OH) and x 3 (H 2 O) Augmented simplex-centroid design used to optimize composition of H 2 O 2 -NH 4 OH mixtures B S 2 T T S T 3 T 4 B 3 NH 4 OH (30 wt%) H2 O 2 B 1 Single Binary Mixture Ternary Mixture (30 wt%) Logit transformation Y = ln y Τ( 1 y) where y is the cleaning efficiency expressed in the range of 0 to J. Seo, A. Gowda, and S.V. Babu., ECS J Sold State SC, Submitted (2018)

11 Summary of Optimization of H 2 O 2 -based Alkaline Solutions Solution Number H 2 O 2 (30 wt%) NH 4 OH (30 wt%) DIW ph Rq (nm) Cleaning Efficiency 10 nm 30 nm 90 nm <5 % <5 % <5 % % 23 % 60 % <5.0 % <5.0 % <5 % % 99 % 99 % <5 % <5 % <5 % <5 % <5 % <5 % % 56 % 89 % % 62 % 89 % % 68 % 90 % % 89 % 99 % SC % 58 % 94 % Table. Surface roughness (Rq) and cleaning efficiencies of the ten compositions tested based on full cubic model, and SC1 solution. 11 J. Seo, A. Gowda, and S.V. Babu., ECS J Sold State SC, Submitted (2018)

12 Summary of Optimization of H 2 O 2 -NH 4 OH mixtures DOE 90 nm-ceria Cleaning Efficiency Cleaning efficiencies of SC1 solution 30 nm-ceria 10 nm-ceria A contour plot of cleaning efficiencies showing the synergistic effect of H 2 O 2 (30 wt%), NH 4 OH (30 wt%), and H 12 2 O mixtures; 90 nm-ceria, 30 nm-ceria, and 10 nm-ceria.. J. Seo, A. Gowda, and S.V. Babu., ECS J Sold State SC, Submitted (2018)

13 1. Introduction 2. Physico-chemical Properties of Ceria Particles with different sizes 3. H 2 O 2 -NH 4 OH Mixtures and Their Optimization 4. Investigation of Mechanism of the Cleaning of Ceria Particles using H 2 O 2 -based Alkaline Solutions from Silicon Dioxide Surfaces 5. Summary 13

14 H 2 O 2 + OH - K eq HO2- + H 2 O pk a = 11.6 where K eq = [HO 2 ] = K [H K ion ion = + ][HO 2 ] ( mol/l at 25 o C) for H [H 2 O 2 ] 2 O 2 HO [H 2 O 2 ] K W K W for water is mol 2 /L 2 at 25 o C X = starting molar concentration of NH 4 OH Y = starting molar concentration of H 2 O 2 Z = formed molar concentration of [HO 2- ] at equilibrium [HO - ] and [H 2 O 2 ] are the concentrations of hydroxyl ion and undecomposed hydrogen peroxide at equilibrium, respectively, which gives [HO - ] = X Z and [H 2 O 2 ] = Y Z K eq = HO 2 HO = [H 2 O 2 ] Z X Z)(Y Z [HO 2 ] = R R 2 4XY 2 [HO 2- ] has a maximum when R 2 = 4 XY where R = X + Y+ 1/K eq 14 Maximum value of [HO 2- ] = X = Y

15 Cleaning efficiency as a function of perhydroxyl ions in mixtures of H 2 O 2 -based alkaline cleaning solution Cleaning efficiency (%) NH 4 OH (filled symbols) KOH (open symbols) Calculated molar concentrations of perhydroxyl ion (mol/l) 10 nm 30 nm 90 nm Solution Perhydroxyl Number Ions (mol/l) Cleaning Efficiency 10 nm 30 nm 90 nm <5 % <5 % <5 % % 23 % 60 % <5.0 % <5.0 % <5 % % 99 % 99 % <5 % <5 % <5 % <5 % <5 % <5 % % 56 % 89 % % 62 % 89 % % 68 % 90 % % 89 % 99 % SC % 58 % 94 % NH 4 OH % 99 % 99 % KOH % 95 % 97 % KOH % 82 % 96 % KOH % 41 % 89 % KOH % 99 % 98 % 15 J. Seo, A. Gowda, and S.V. Babu., ECS J Sold State SC, Submitted (2018)

16 As-received Silicate-covered (partially covered) Silicate-covered (more concentrated silicate) Transmittance (a.u.) H 2 O NH 4 + NO 3 - (NH 4 OH-treated) (H 2 O 2 -treated) (Solution 4) -O- O-O Ce-OH Wavenumber (cm -1 ) Transmittance (a.u.) -Silicate Si-OLO 3 Si-OTO 4 Si-OLO 4 -Silicate (NH 4 OH-treated) -Silicate (H 2 O 2 -treated) -Silicate (Solution 4) Si-OTO 3 Si-OH O-O Wavenumber (cm -1 ) Transmittance (a.u.) -Silicate Si-OLO 3 Si-OTO 4 Si-OLO 4 -Silicate (NH 4 OH-treated) -Silicate (H 2 O 2 -treated) -Silicate (Solution 4) Si-OTO 3 Si-OH Wavenumber (cm -1 ) FT-IR spectra of ceria particles in the region of cm -1. As-received, silicate (0.01 wt%) silicate (0.1 wt%) covered 10 nm-ceria particles that were reacted with four different solutions (H2O, H2O2 (30 wt%), NH4OH (30 wt%), and H2O2-NH4OH mixture (50/50 volume ratios). 16 J. Seo, A. Gowda, and S.V. Babu., ECS J Sold State SC, Submitted (2018)

17 H 2 O 2 + OH - K eq HOO- + H 2 O Ce 3+ O Si TEOS film Ce 3+ O ㅡ O OH - particle lift-off Bond type Bond dissociation energy (kj/mol) Perhydroxyl anion O-O 210 (OOH) O-H 336 Hydroxyl ion O-H 487 Ce-O-Si Ce-O 790 Si-O 452 Table. Known binding energy data 17 J. Seo, A. Gowda, and S.V. Babu., ECS J Sold State SC, Submitted (2018)

18 1. Introduction 2. Physico-chemical Properties of Ceria Particles with different sizes 3. H 2 O 2 -NH 4 OH Mixtures and Their Optimization 4. Investigation of Mechanism of the Cleaning of Ceria Particles using H 2 O 2 -based Alkaline Solutions from Silicon Dioxide Surfaces 5. Summary 18

19 Smaller ceria particles are more difficult to remove from oxide surfaces after CMP. We showed that high ph H 2 O 2 -based cleaning solutions, aided by ultrasonic energy, can almost completely remove ceria particles down to 10 nm in size as determined by AFM imaging and counting. Highest removal efficiencies were obtained when the molar concentration of the perhydroxyl ions [HO 2- ] is the highest possible in the cleaning solution. 19

20 1. Dr. S.V. Babu 2. Ebara Corporation 3. Solvay 20