Chemical Mechanical Planarization STACK TRECK. SPCC 2017 Viorel Balan

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1 Chemical Mechanical Planarization STACK TRECK

2 > Red 50 is years The of New Moore s Blue Law Stacking Is The New Scaling 2 Lithography Enables Scaling / CMP Enables Stacking

3 Building Stacked Devices by Hybrid Direct Bonding Challenges Direct Bonding Roughness & Clean SiO 2 & Cu Non-Patterned Wafers Hybrid Direct Bonding Patterned Wafers Topography: Local/Global Conclusion Stack Trek The Next Generation 3

4 Stacking Heterogenous Devices Application to 3D Stacked Back Side Imagers J. Chossat 3D Summit Grenoble 2016 Wafer to Wafer Stacking by Hybrid Direct Bonding Technology Top Die Contains only Pixels Passive Substrate replaced by Advanced Digital CMOS wafer Manufacturing Flexibility Different Technology Nodes (Design Rules) for different components CSTIC2017 Viorel Balan 4

5 Stacking Heterogenous Devices 3D Stacked BSI by Hybrid Direct Bonding J. Chossat 3D Summit Grenoble 2016 Wafer 2 Special Interconnect Level LINE1 LINE2 HBMT LINE4 Special Interconnect Level ADVANTAGES Done at RT, ambiant pressure No glue needed LIX 1-5 Pitch < 1 µm Wafer achievable, 1 alignment dependant The key technology step for 3D stack is the interconnection of the upper and lower part of the circuit. CSTIC2017 Viorel Balan 5

Copper/oxide surface direct bonding advantages: Very high interconnect density possible.

6 6 From Direct Bonding To Hybrid Direct Bonding Dielectric Mechanical Strength SiO 2 + Cu most promising 3D integration candidate Main metal used for CMOS interconnects Cost of ownership Copper/oxide surface direct bonding advantages: Very high interconnect density possible. Low-temperature process Compatibility FEOL/BEOL requirements for a sequential approach Metal Electrical connection Cu: microelectronic

Topography WIWNU WIDNU Planar Roughness Diameter Planar Die Planar Device

7 Chemical Mechanical Planarization Challenges for Recreating The Bulk from 2 Mixt Surfaces Bond 2 Surfaces with Cu Barrier Dielectric Manage Topography WIWNU WIDNU Planar Roughness Diameter Planar Die Planar Device Planar Atomic Planar Intimate Surface Contact Needed Spatial λ 7

8 Chemical Mechanical Planarization Challenges for Recreating The Bulk from 2 Surfaces 8 WIWNU WIDNU Planar Roughness Diameter Planar Die Planar Device Planar Atomic Planar

9 F. Rieutord, ECS 2006 Direct Bonding SiO 2 Roughness Impact H. Moriceau, Microelectronic Reliability 2012 Surface high frequency micro-roughness key role in the bonding phenomenon, Low frequency roughness can be accommodated by deformation of each substrate (elastic energy price) A 0,18nm B 0,21nm C 0,23nm SiO 2 /SiO 2 Blanket Bonding RMS<0.5nm D 0,2nm 9

Direct Bonding Cu-Cu Roughness Post- Depot Post CMP Cu RMS 20x20µm 33 0.3 2.

10 Direct Bonding Cu-Cu Roughness Post- Depot Post CMP Cu RMS 20x20µm Hydrophilicity RMS=33nm Cu Layer Contact Angle 49 As deposited 19 Post CMP RMS=0,3nm Contact Angle ( ) As deposited Post CMP "+H24" Cu Contact Angle Evolution Time (h) P. Gueguen ECS 2008 RMS & Contact Angle Increase Q Time Impact 10

Direct Bonding Cleaning Influence RMS[nmm] AFM 0.89 0.28 0.

11 Direct Bonding Cleaning Influence RMS[nmm] AFM CLEAN A CLEAN B CLEAN C SiO2 Blanket Bonding (SAM) (A) 0,29nm 0,89nm (B) (B) (C) Bonded UnBonded (C) Copper Blanket Bonding (SAM) (A) (B) Cleaning Solution Adapted both to Cu & SiO2 Bonded UnBonded (C) 11

12 Direct Bonding Cu-Cu Interface Evolution=f(T C) Cu-Cu Interface=f( C) by TEM P. Gueguen, J. of Microelect. Eng., Vol 87 pp.477 484 (2010) Di Cioccio L et al 2010 218th ECS Conf.

12 12 Direct Bonding Cu-Cu Interface Evolution=f(T C) Cu-Cu Interface=f( C) by TEM P. Gueguen, J. of Microelect. Eng., Vol 87 pp (2010) Di Cioccio L et al th ECS Conf. Thin copper oxide interfacial layer at the bonding interface 200 C, this copper oxide becomes thermodynamically unstable grain growth sealing: XRR Bonding interface turns into a grain boundary with a high bonding energy XRR=f( C) Moriceau H et al 2010 (Workshop on Low Temperature Bonding for 3D Integration)].

13 Chemical Mechanical Planarization Challenges for Recreating The Bulk from 2 Surfaces 13 WIWNU WIDNU Planar Roughness Diameter Planar Die Planar Device Planar Atomic Planar

14 14 Hybrid Direct Bonding Local Topography Impact Modelisation Dishing critical: topography doubled negative impact electrical contact Pattern Wafer 2 Dishing 2h h Pattern Wafer 1 GAP / DISHING C. Sart ESTC 2016 Cohesive tractions effective below threshold value Dishing (nm)

impact electrical contact T C T C T C T C

15 Pattern Wafer 2 Dishing 2h h Pattern Wafer 1 Hybrid Direct Bonding Local Topography Impact Modelisation Dishing critical: topography doubled negative impact electrical contact T C T C T C T C Wafer Approach Y. Beilliard et al. International Journal of Solids and Structures, 2016 RT C bonding Annealing T C 2h Small dishing of Cu pads overcome during post bond annealing low T C: 200 C RT C Cu/Cu Interface Remains Closed after Cooling Down to Room Temperature Agreement w/ Experimental Results 15

16 Hybrid Direct Bonding Predictive Model Dishing 1nm Dishing 20nm S. Lhostis European 3D Summit 2017 C. Sart ESTC 2016 Predictive Model for the Process of Hybrid Bonding Layer 16

17 Hybrid Direct Bonding Patterned Wafers DOE 17 >250 process conditions used pads, slurries, %abrasif %/oxydant, V,P, flow, time

18 Hybrid Direct Bonding Process Optimization step height Step Height (a.u.) step height Pad Shape Pad Size Width (µm) Square HBM pad Octagon HBM pad 3.6 µm diameter 4.4 µm diameter 5.4 µm diameter Bonding Toughness (J/m 2 ) Annealing Temperature ( C) S. Lhostis ECTC2016 L. Di Cioccio J. Electrochem. Soc,158, 2011 Very Low Dishing, Uniform vs Cu Pad Shapes & Sizes High Bonding Toughness Obtained 18

19 Chemical Mechanical Planarization Challenges for Recreating The Bulk from 2 Surfaces 19 WIWNU WIDNU Planar Roughness Diameter Planar Die Planar Device Planar Atomic Planar

20 Stacking Heterogenous Devices Dimension & Density Impact SAM Image Low Bonding Quality Test Mask Dimension/Density Bonded UnBonded Dimension Interferometry Image Nanotopography Information Resolution 0,5µm X,Y 0,1nm Z Design Optimization Density/Dimension Post-CMP High Topography Die Level Post-CMP Low Topography Atomically Flattened Surfaces thru Design Optimization Excellent Hybrid Direct Bonding Quality 20

21 Chemical Mechanical Planarization Challenges for Recreating The Bulk from 2 Surfaces 21 WIWNU WIDNU Planar Roughness Diameter Planar Die Planar Device Planar Atomic Planar

22 Hybrid Direct Bonding Patterned Wafers DOE Pattern to pattern 3 wafers/investigated point: 2 bonded, 1 characterized Pattern (PW) to non-patterned (NPW) bonding validation PW to PW Process Conditions Adjustement Costly Process in Patterned Wafers 22

23 Stacking Heterogenous Devices Dimension & Density Impact Global, Diameter Planarization Bonded UnBonded SAM Image Excellent Bonding Quality Bonding Wave Propagation Time CMP Process Recipe Optimization (V,P,Time) Improved Diameter Planarization through CMP Process Optimization, validated by Bonding Wave Propagation Time 23

24 Stacking Heterogenous Devices Excellent Bonding: Bulk Reconstruction L. Benaissa ECTC2015 S. Lhostis ECTC2016 Copper Grain Reconstruction: Excellent Electrical Results, 100% Yield 24

25 Stacking Heterogenous Devices Increase Device Cleverness 3D Stacking Heterogenous Form Factor Power consumption Cleverness The key technology is the interconnection of the upper and lower part of the circuit Manufacturing Flexibility different Technology Nodes (Design Rules) for different components AppStore DieStore 3D DieStore: Design Rules Standardization for Interconnect Level 25

26 Conclusion 3 Take-Home Messages 3D Heterogenous Stacking DieStore w/rigourous Design Standardization of Interconnect Level Stacking Devices to Increase Cleverness needs Excellent Flatness: CMP is Driver to Relief, 3D World Moore s Law: Paradigm Change from Scaling/Stacking 3D Integration 26

27 Thank You Leti, technology research institute Commissariat à l énergie atomique et aux énergies alternatives Minatec Campus 17 rue des Martyrs Grenoble Cedex France

Chemical/Mechanical Balance Management through Pad Microstructure in Si CMP

Chemical/Mechanical Balance Management through Pad Microstructure in Si CMP Post CMP Cleaning Austin 2017 Ratanak Yim (Viorel Balan) R. Yim 1,2,5, C. Perrot 2, V. Balan 1, P-Y. Friot 3, B. Qian 3, N. Chiou