Cleaning Surfaces from Nanoparticles with Polymer Film: Impact of the Polymer Stripping A. LALLART 1,2,3,4, P. GARNIER 1, E. LORENCEAU 2, A. CARTELLIER 3, E. CHARLAIX 2 1 STMICROELECTRONICS, CROLLES, FRANCE 2 LIPHY, UNIVERSITÉ GRENOBLE ALPES, SAINT MARTIN D HÈRES, FRANCE 3 LEGI, UNIVERSITÉ GRENOBLE ALPES, SAINT MARTIN D HÈRES, FRANCE 4 CEA LETI, GRENOBLE, FRANCE
Outline 2 Motivations Experimental setup Results Hypothesis Conclusion
Miniaturization & particle impact on yield 3 Transistor amount bought per $ Transistors Particles Killer Transistor length Transistor www.economist.com/news Miniaturization Critical particle size decrease
Particles on transistors A. LALLART Cleaning Surfaces from Nanoparticles with Polymer Film SPCC 2018 Boston April 10-11 Structure damage Challenge: Particle removal / No damage 4 Particle removal force Particle removal =90% Structure damage Frequency Cleaning Process Window Energy or strength normalized to size of particle or structure 1 µm 1 µm
Challenge: Particle Removal / No Damage 5 High Brush Acoustic Damage Jet Low Low Particle Removal Efficiency High
Particle Removal Condition 6 F adhesion < F external Parameters influencing F adhesion : F adhesion τ aging = γd 1 ln( P sat P v ) ln( τ aging τ 0 ) Aging System Particle Characteristic γ liquid surface tension d distance taking into acount the geometrical characteristics of the contact P sat saturated water pressure P v vapour pressure τ aging time since contamination τ 0 time needed to condense one liquid layer Bocquet, L., & al, Nature (1998)
Particle Removal Efficiency (%) A. LALLART Cleaning Surfaces from Nanoparticles with Polymer Film SPCC 2018 Boston April 10-11 Relative Particle Removal Efficiency Spray still efficient enough? 7 F adhesion τ aging Bocquet, L., & al, Nature (1998) = γd 1 ln( P sat P v ) ln( τ aging τ 0 ) Particle Spray cleaning efficiency on silicon wafer depending on particle size 100 90 80 70 60 50 40 30 20 10 0 13 26 99 70 nm 100 nm 200 nm SiO 2 Particle Size (nm) Spray cleaning efficiency on silicon wafer depending on aging time 1 0,8 0,6 0,4 0,2 0 1 6 14 Aging Time (days) Aibara, M., & al, ECS conf. (2017)
Spray still efficient enough? 8 Strong particle size dependence on removal efficiency Strong aging time dependence on removal efficiency Droplet size limitation Trench Droplet ~ 4µm 0,2 µm 2 µm New solution required Droplet size > Trenches size
Motivations 9 Find a new method to remove nanoparticles : Without structure damage Environmental friendly
New solution based on polymer removal 10 F adhesion polymer/particle > F adhesion surface/particle Contact area polymer/particle > Contact area surface/particle Pull off Polymer chain Particle Contact area polymer/particle Surface Contact area surface/particle
2 postulated ways to remove the polymer 11 Contamination Particles Surface Polymer Coating PDMS PAM Polymer Removal Polymer elasticity Solid polymer Solid Peeling Peel off Extensional viscosity Liquid polymer Fluid Siphoning Lin, P., & al, Nanotechnology (2013) Walker, T.W., & al, JoR (2014)
Outline 12 Motivations Experimental setup Process step Polymer removal Results Hypothesis Conclusion
300 mm Silicon wafer Method - Process Steps 13 Particles amount initial measure Particles amount final measure Intentional Contamination Polymer coating Baking Polymer removal Contamination: Spin dryer / SiO 2 60 nm Polymer coating: Polymer 1,8 µm thickness Baking: No reticulation (130 C) Polymer removal: Chemical solution (SPM / SC1) Measurement: Laser diffraction spectrometer Wafer defect mapping Initial contamination
Wafers Wet Bench Method Polymer Removal Spray Batch 14 Rotation Chemical removal only Chemical & Physical removal Side view Central Spray Spray direction
Outline 15 Motivations Experimental setup Results Polymer removal: - Wet Bench vs Spray Batch Polymer coating Cleaning efficiency Hypothesis Conclusion Surface Contamination: - Particle Nature (SiO 2, Si 3 N 4, ) - Particle Size - Aging time
Wet Bench versus Spray Batch 16 Polymer Chemical solution (SPM / SC1) Wet Bench Spray Batch Initial Particles Mapping Final Particles Mapping Physical action mandatory Non uniform removal Particles remain along the spray flow lines Removal efficiency (%) 0 % 87 %
No Polymer Polymer Presence 17 Polymer Chemical solution (SPM / SC1) - Spray Batch Initial Particles Mapping Polymer needed for particles removal Final Particles Mapping Removal efficiency (%) 0 % 87 %
Particle Removal Efficiency (%) A. LALLART Cleaning Surfaces from Nanoparticles with Polymer Film SPCC 2018 Boston April 10-11 SiO 2 Monodisperse Contamination Polymer Coating Baking Aging Time 18 Polymer Removal Chemical Solution (SPM / SC1) Spray Batch 100 90 80 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 Aging Time between contamination & polymer removal (days) No aging time dependence on Particle Removal Efficiency
SiO 2 monodisperse Si 3 N 4 polydisperse Polymer Chemical solution (SPM / SC1) - Spray Batch Particles Size & Nature 19 Efficient removal for both particles nature Initial Particles Mapping Final Particles Mapping 90 80 70 60 50 40 30 20 10 0 Particle Removal Efficiency (%)100 Particles Size Distribution Si3N4 polydisperse SiO2 monodisperse Removal efficiency (%) 85 % 85 % No size influence on Removal Efficiency
Summary 20 No aging time dependence on removal efficiency No particle nature dependence on removal efficiency No particle size dependence on removal efficiency No influence of the F adhesion on removal efficiency Hypothesis?
Hypothesis : Peeling Zero Degrees 21 Shear stress due to expansion? Surface Spray Batch Top view E b Young Modulus of the hard layer Bulk polymer Centrifugal Force Rotation 80 RPM Ponce, S., & al, Soft Matter (2015)
Hypothesis : Peeling Zero Degrees 22 E b Young Modulus of the hard layer Centrifugal Force Surface Ponce, S., & al, Soft Matter (2015)
Conclusions & Perspectives 23 Conclusions Perspectives New solution to remove nanometric particles Aging independent Particle nature/size independent Without pattern damage To fully understand the mechanism of polymer removal Verify the peeling zero degrees hypothesis Adhesion & rheological studies
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