Thin Wafer Handling Debonding Mechanisms Jonathan Jeauneau, Applications Manager Alvin Lee, Technology Strategist Dongshun Bai, Scientist, 3-D IC R&D Materials
Outline Requirements of Thin Wafer Handling for 3-D IC Developments Hurdles & Achievements Path Forward Acknowledgement
General Process Flow Coating/Bonding Backgrinding Stress relief etching Photolithography Plasma etching/rie Resist stripping 70-µm-thick wafer, 1:1-aspect-ratio vias, copper redistribution layer Dielectric deposition Seed layer deposition Electroplating Debonding Silicon interposer, RDL - Fuji
Development of Thin Wafer Handling Technology Brewer Science Bonding Material Carrier Thermal Bonding Thinning & Backside Processing Debonding Thermal Stability 300 C Heat 200 C 100 C Note. Carrier-less solutions are excluded
30 Development of Debonding Technologies WPH Gen 3 Gen 2 Gen 1 Gen 3 Thermal Stability 300 C Release Zone Stiction Zone 20 Slide Heat 200 C 10 100 C 2000 2005 2010 2015 2020
Brewer Science Thin Wafer Handling Technologies Carrier Preparation Coating Process Debonding BrewerBOND carrier preparation ZoneBOND carrier preparation Glass BrewerBOND materials ZoneBOND materials WaferBOND materials Glass Edge refortification Chemical resistance CVD stability Effective cleaning Carrier recycle Gen 3 tech ZoneBOND debonding Slide off Chemical release Sapphire Silicon Device
Requirements Temporary Bonding Must Meet Step Process Consideration Examples 1 Coating/ Carrier prep. 2 Bonding 3 Backside processes 4 Debonding TTV, coating uniformity, step coverage TTV, void free, alignment, squeeze out Void free, warpage With frame, room temperature debonding 5 Cleaning Residue free, high yield
Challenges Edge bead/ Uniformity Carrier TSV Wafer Bonding & Thinning Carrier In-film defect TSV Wafer Carrier Thinning Carrier Process compatibility Carrier Backside Processes Carrier
Coating Profile Spin Coating High edge bead from traditional spin coating Backgrinding performance is directly impacted For example, edge beads ~80 µm in height are typical Reduced by process and equipment advancements to 7 µm 80 µm 7 µm 14 mm from edge
Thinning with WaferBOND HT-10.10 Bonding Material (IMEC)
Successful Thinning to 5 µm (ITRI Ad-STAC) 300-mm Blank Si 5-µm Si Glass Carrier
Process and Equipment Effect on Material Requirements Found stress pattern or wrinkling after PECVD Perceived as a material failure fixed by process and equipment changes Same bonding material, coating, and baking conditions PECVD at 160 C set point Wafer size: 300-mm Si
High Thermal Stability The newest formulation meets the high temperature requirements in backside process. - Decomposition temperature up to 363 C (2% weight loss measured by TGA in air) - Isothermal at 250 C for 30 minutes in air, no noticeable weight loss
High Thermal Stability Bonding at 200 C - No delamination after heat treatment at 260 C for 1 hour on a hot plate in air - No delamination after heat treatment at 300 C for 15 min under vacuum After bonding at 200 C After heat treatment at 260 C for 60 min After heat treatment at 300 C for 15 min
300-mm Wafer Bonding and Grinding Thickness: Devi 300-mm Si wafer 753.6 µm Bonding material thickness 106.1 µm Carrier 764.9 µm Post-bonding TTV: 7.4 µm CSAM: as left image, no void Thinning: After Grinding Avg. Thickness of Si (µm) Pair Thickness (µm) Pair TTV (µm) 51.009 936.357 2.571
Summary Thin wafer handling is a necessity for advanced 3-D IC manufacturing Post-thinning TTV less than 2 µm can be achieved through selected bonding material and process control Optimization of bonding material and bonding process can eliminate defects Use of a proprietary BrewerBOND material with stability higher than 300 C can result in coating non-uniformity less than 5% and high WPH
Acknowledgements A special thank you to: IMEC ITRI Ad-STAC SUSS MicroTec SEMI Europa The Brewer Science development team
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