Electrografted insulator layer as copper diffusion barrier for TSV interposers V. Mevellec, D. Suhr, T. Dequivre, P. Blondeau, L. Religieux and F. Raynal Scottsdale/Fountain Hills March 12-14, 2013
3D Packaging / TSV Wet alternatives technologies 1 st Process flow for TSV interposer metallization - eg 3D Isolation - cg 3D Cu diffusion barrier - eg 3D Cu Seed - eg 3D Cu Fill eg 3D Isolation cg 3D Cu diffusion barrier eg 3D Cu Seed ECD copper imaps 2013 Presentation 2
3D Packaging / TSV Wet alternatives technologies 1 st Process flow for TSV interposer metallization Ultra-conformal Up to 20:1 aspect ratio High step coverage (room temperature) - eg 3D Isolation - cg 3D Cu diffusion barrier - eg 3D Cu Seed - eg 3D Cu Fill imaps 2013 Presentation 3
3D Packaging / TSV Wet alternatives technologies 2nd Process flow for TSV interposer metallization - eg 3D Isolation - cg 3D Cu diffusion barrier - eg 3D Cu Fill eg 3D Isolation cg 3D Cu diffusion barrier ECD copper imaps 2013 Presentation 4
3D Packaging / TSV Wet alternatives technologies 3 rd Process flow for TSV interposer metallization - eg 3D Isolation - cg 3D Fill eg 3D Isolation cg 3D Cu Fill Under Development imaps 2013 Presentation 5
Polymer Electrografting (eg) Concept of electrografting e- Grafted polymer layer Room temperature Aqueous phase Covalent bonding - Fundamental - Mechanism Cathode (Conductor or semiconductor Organic Monomer imaps 2013 Presentation 6
Polymer Electrografting (eg) Concept of electrografting Radical polymerization electro-initiated R R - Fundamental - Mechanism R imaps 2013 Presentation 7
Polymer Electrografting (eg) Concept of electrografting Radical polymerization electro-initiated e-. R - Fundamental - Mechanism.. R R imaps 2013 Presentation 8
Polymer Electrografting (eg) Concept of electrografting Radical polymerization electro-initiated. R - Fundamental - Mechanism.. R R imaps 2013 Presentation 9
Polymer Electrografting (eg) Concept of electrografting Radical polymerization electro-initiated - Fundamental - Mechanism.... R R R R R R R R.. R R R R R R R R R R R R R R R R imaps 2013 Presentation 10
Polymer Electrografting (eg) Concept of electrografting Radical polymerization electro-initiated... - Fundamental - Mechanism imaps 2013 Presentation 11
Polymer Electrografting (eg) Concept of electrografting Polymer used for TSV applications - Fundamental - Mechanism 4-Vinyl pyridine + X - 4-Nitrobenzene diazonium eg Poly-4-Vinyl pyridine imaps 2013 Presentation 12
Insulating properties C ox = ε 0 ε r A t - Breakdown voltage - Leakage current - Dielectric constant - Capacitance density Electrografted polymer layer Cu barrier effect eg Polymer Thermo-mechanical properties - E-modulus - CTE - TGA - SEM cross section - TOF SIMS depth profile - Breakdown voltage shift imaps 2013 Presentation 13
Insulating properties C ox = ε 0 ε r A t - Breakdown voltage - Leakage current - Dielectric constant - Capacitance density Breakdown voltage Thickness : 200 nm for SiO2 and eg polymer eg Breakdown Field = 12 MV/cm Thermo-mechanical properties - E-modulus - CTE - TGA Leakage current At 0,25 MV/cm SiO2 10 na/cm2 eg Polymer 15 na/cm2 imaps 2013 Presentation 14
Insulating properties C ox = ε 0 ε r A t - Breakdown voltage - Leakage current - Dielectric constant - Capacitance density Thermo-mechanical properties - E-modulus - CTE - TGA Dielectric constant εr = (3.7.10-11.200.10-9 )/(8.85.10-12.2.82.10-7 )= 2.96 Capacitance density Cmax / S = 3.7.10-11 /2.82.10-7 = 1.3.10-4 F/m 2 imaps 2013 Presentation 15
Thickness (nm) Insulating properties C ox = ε 0 ε r A t - Breakdown voltage - Leakage current - Dielectric constant - Capacitance density Thermo-mechanical properties - E-modulus - CTE - TGA E-Modulus CTE 112.50 112.00 111.50 111.00 110.50 110.00 109.50 TGA y = 0.0025x + 110.83 CTE Warm Cool 40 60 80 100 120 140 160 180 200 Temperature (deg) eg polymer 4.05GPa. (SiO2 = 107GPa) CTE = 30 ppm/ C < 1% mass loss at 350 C imaps 2013 Presentation 16
Insulating properties C ox = ε 0 ε r A t - Breakdown voltage - Leakage current - Dielectric constant - Capacitance density Electrografted polymer layer Cu barrier effect eg Polymer Thermo-mechanical properties - E-modulus - CTE - TGA - SEM cross section - TOF SIMS depth profile - Breakdown voltage shift imaps 2013 Presentation 17
eg Polymer + Eless Copper Cu barrier effect No degradation of the polymer layer 400 C/ 2h under N2/H2 eg Polymer - SEM cross section - TOF SIMS depth profile - Breakdown voltage shift imaps 2013 Presentation 18
Intensité (coups) eg polymer (200nm) + Eless copper (200 nm) after 400 C / 2H Profil0458P4VP01.xls Cu barrier effect 60000 50000 40000 30000 Cu Polymer Si Si C_4 ^63Cu eg Polymer 20000 10000 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Temps (seconde) -Analysis Artefact due to ion beam push through -Backside depth profile on going - SEM cross section - TOF SIMS depth profile - Breakdown voltage shift imaps 2013 Presentation 19
Sample preparation: Cu barrier effect eg Polymer Breakdown measurement : Shift: -1,3 MV@80nm eg Polymer - SEM cross section - TOF SIMS depth profile - Breakdown voltage shift imaps 2013 Presentation 20
Conclusion - eg Polymer shows promising results as copper diffusion barrier - Additional characterizations are ongoing : - * Breakdown shift for thick polymer layer - * Backside analysis using TOF-SIMS depth profile Cu barrier effect eg Polymer Optimization of the polymer nature can be investigated by changing the formulation of the bath/curing step/cross linking/etc.. What about the cost saving? - SEM cross section - TOF SIMS depth profile - Breakdown voltage shift imaps 2013 Presentation 21
Cost Analysis TSV interposers metallization Baseline (Dry) - Baseline : PECVD SiO2 - PVD Barrier - PVD Copper - ECD Fill - Current Wet flow : eg Isolation - cg Barrier - eg Fill - Next Wet flow : eg Isolation - cg Fill imaps 2013 Presentation 22
Cost Analysis TSV interposers metallization Baseline (Dry) Current wet flow - Baseline : PECVD SiO2 - PVD Barrier - PVD Copper - ECD Fill - Current Wet flow : eg Isolation - cg Barrier - eg Fill - Next Wet flow : eg Isolation - cg Fill - 30 % CoO imaps 2013 Presentation 23
Cost Analysis TSV interposers metallization Baseline (Dry) Current wet flow Next wet flow - Baseline : PECVD SiO2 - PVD Barrier - PVD Copper - ECD Fill - Current Wet flow : eg Isolation - cg Barrier - eg Fill - Next Wet flow : eg Isolation - cg Fill - 30 % CoO - 43 % CoO imaps 2013 Presentation 24
Conclusion - Alchimer s proprietary wet technologies enables 2.5D interposers metallization in high aspect ratio structures. - 2.5D metallization process flow can be simplified by combining material properties - * Barrier + Seed - * Isolation + Barrier - 2.5D Process flow - Polymer barrier - Cost reduction imaps 2013 Presentation 25
Conclusion - 2.5D Process flow - Polymer barrier - Cost reduction - Alchimer s proprietary wet technologies enables 2.5D interposers metallization in high aspect ratio structures. - 2.5D metallization process flow can be simplified by combining material properties - * Barrier + Seed - * Isolation + Barrier - First results on the electrografted polymer layer as a copper diffusion barrier show encouraging results - Optimization and detailed characterization are on ongoing to improve the barrier effect of the polymer layer imaps 2013 Presentation 26
Conclusion - Alchimer s proprietary wet technologies enables 2.5D interposers metallization in high aspect ratio structures. - 2.5D metallization process flow can be simplified by combining material properties - * Barrier + Seed - * Isolation + Barrier - First results on the electrografted polymer layer as a copper diffusion barrier show encouraging results - Optimization and detailed characterization are ongoing to improve the barrier effect of the polymer layer - 2.5D Process flow - Polymer barrier - Cost reduction - By using wet technologies for TSV metallization, cost of ownership is decreased by 30% today - New development will put the cost savings close to 45% compare to conventional dry approaches imaps 2013 Presentation 27
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