ENABLING THIN GLASS SOLUTIONS FOR 5G - INEMI
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ENABLING THIN GLASS SOLUTIONS FOR 5G Aric Shorey VP Business Development Mosaic Microsystems Co-Authors David Levy / Shelby Nelson / Paul Paul Ballentine Webinar recording (note: due to technical difficulties, the recording starts on slide 3) YouTube: https://youtu.be/TlrTSXQ5_xg Alternate link: http://thor.inemi.org/webdownload/2021/5G-mmWave_Enabling_Thin_Glass.mp4 July 15, 2021
Outline/Agenda • Motivation • Advantages of glass packaging solutions • Handling challenges • Solutions to enable volume manufacture • Examples showing advantages of glass based devices • Summary • Q &A 1 Mosaic Microsystems
Thin glass addresses industry needs New material solutions are needed to address needs in RF communications • Low loss for 5G/mmWave • Military • Reduced footprint Advanced packaging solutions are needed to extend industry performance targets • Interposer • Embedded die • Hermetic 2 Mosaic Microsystems
Material properties of glass provide attractive solutions Good Fair Poor Materials Characteristic Ideal property Glass Si Organic Ceramic • High resistivity Electrical • Loss loss, low k • Smooth surface ✓ Low loss Physical • Large area scalability • Ultra thin ✓ CTE match Thermal • High conductivity ✓ Smooth • High strength, modulus Mechanical • Low warpage ✓ Thin • Resistance to process Chemical chemistry ✓ Cost-effective Via and RDL cost • Low cost for both ✓ Scalable Reliability • CTE match to Si and PWB Cost/mm 2 • @25 um I/O pitch Based on chart from Georgia Tech PRC 3 Mosaic Microsystems
Handling glass < 200 um thick has challenges Challenges for TGV in thin glass • Handling thin glass in semiconductor fab environment • Metallizing vias in a reliable, cost-effective way 4 Mosaic Microsystems
New approach to enable thin glass New approach: Thin glass with through-holes temporarily bonded to silicon handle wafer using Viaffirm™ technology • Addresses flatness • Equipment interface is Si wafer • Provides path to existing metallization processes Can be processed like a standard silicon wafer 5 Mosaic Microsystems
Robust temporary bonding • New process relying on a thin inorganic layer Via formation Bond • Very resistant to temperature, harsh chemistries • No outgassing Process Adhesive on handle • Thin adhesion layer → Excellent flatness • Debond: Debond – Simple, mechanical – Adhesion layer stays on handle • Compatible with silicon processing (installed equipment base) 6 Mosaic Microsystems
Key aspects of Viaffirm™ technology • Bond is temporary to ≥400⁰ C • Mechanical de-bond with •
Debond process • Mechanical de-bond with low force • Demonstrated with commercial volume tools (Suss, CEE) • Debond residue on device wafer? –XPS measurement pre/post bond –Carbon differences likely adventitious –Low impact on glass peaks:
Process scalability Demonstrated to 300 mm diameter (and beyond) 100 mm 150 mm 200 mm 300 mm 9 Mosaic Microsystems
Mosaic Process Flow – Via fill Leverage established processes for metallized TGV a) d) b) e) c) f) Mosaic Microsystems
Via Fill on Mosaic bonded pair After plating • ~30 um via / 100 um glass on silicon handle • MOCVD Seed layer / Cu plate – Void free via fill Via fill • CMP: – Bond energy sufficient: no issues • Post-CMP anneal (400 ºC) – No cracking at vias After CMP After anneal 11 Mosaic Microsystems
TGV Planarity Back side TGV planarity < 100 nm at de-bond a) De-bond glass wafer and inspect via planarity after de-bond • Measure roughness/planarity with white light • No post-debond CMP interferometer (Zygo ZeGage™) b) Top view of via after debond • Vias planar to < 100 nm 7/19/2021 Mosaic Microsystems 12
Hermeticity • Sample Description: – 35 m via in HPFS / Temporary bond to HPFS handle He leak test regions: – Cu plate bottom up via fill 35mm diameter – CMP to remove ~4 m overburden ~3300 vias each – Mechanical debond • Hermeticity assessment by helium leak test • Results 260C anneal – 8 of 9 regions at better than 1x10-9 atm-cc/s (detection limit) – After 260 °C anneal: • Leak performance still at 1x10-9 atm-cc/s and below as debonded • Slight change in via profile but remains at < 0.5 um deviation 13 Mosaic Microsystems
Use Cases 7/19/2021 Mosaic Microsystems 14
100x0.1 mm wafer – Plated and de-bonded All wafers yielded Thin glass supported by Reverse side of wafer, Metallized wafer on Si dicing tape after debond shown on dicing tape frame 15 Mosaic Microsystems
mmW packaging in glass Wafers processed by GE Research Contact: Todd Miller (millert@ge.com) 2-layer RF interposer cross section 2-layer RF interposer under test • 0.15 mm thick glass • Thermal compression bond Au • Analysis shows glass based approach can provide 50% lower loss with standard glass. More than 70% with fused silica • In some applications you can realize >7x reduce package size volume (e.g. filters) • Primary impact from roughness/skin effect, which is pronounced in these relatively designs that can have conductor lengths as long as 50 mm • Demonstrators to be built in 2021 16 Mosaic Microsystems
Thin glass solutions for 5G – 28 GHz Collaboration Between Mosaic and Fraunhofer IZM • Goals: – Characterize thin glass technology (BCB on fused silica glass) for mm-Wave 5G applications at 28 GHz – Design, fabrication and test of 2x2 aperture-coupled patch antenna arrays on thin glass for femtocells (10m-20m range) – Comparison between glass-based antennas and equivalent organic material-based solutions Investigated thin glass stack-up Investigated organic stack-up and material information and material information 17 Mosaic Microsystems
2x2 Aperture-Coupled Patch-Antenna Array – Geometry & Impedance Matching Parameter Glass Organic x 2505 3710 2505 x 3710 Port 5400 5400 15.4mm 15.4mm Simulated antenna array geometry Simulated 3D antenna model Glass Organic Material -10dB Bandwidth Glass 1630MHz Organic 1670MHz Top view Simulated antenna array impedance matching 18 Mosaic Microsystems
2x2 Aperture-Coupled Patch-Antenna Array – Radiation Pattern and Efficiency Material Peak realized Radiation effieciency Gain Glass Glass 10.9dBi@28 GHz 80%@28 GHz Organic Organic 10.5dBi@28 GHz 75.9%@28 GHz Simulated antenna array peak gain Conclusion: • Thin glass antenna array exhibits higher simulated peak gain and efficiency at 28 GHz and more stable maximum gain over the matched frequency band Next steps: • Fabrication of glass and organic material antenna arrays • Validation of simulation by means of antenna matching and radiation pattern measurement 19 Mosaic Microsystems
Metaconductor for low loss How to decrease conductor loss? • Challenge: Frequency↑, Skin depth ↓, conductor loss ↑ • Cu/Co metaconductor increases effective skin depth • Provides 50% resistance reduction at 28GHz Seahee Hwangbo, Arian Rahimi, and Yong-Kyu Yoon, “Cu/Co Multilayer based High Signal Integrity and Low RF Loss Conductors for 5G/Millimeter Wave Applications,” IEEE Transactions on Microwave Theory and Techniques, vol. 66, no. 8, August 2018, pp. 3773 – 3780 Mosaic Microsystems
Demonstrator: Fused silica integrated 3D inductor Simulations – Inductors with 2x Q-Factor 1) 1 turn inductor 2) 2 turn inductor Cu 150nm Co 25nm 300μm 10 pairs of Cu/Co Q factor metaconductor Q factor 130% improvement 108% improvement = : frequency L: inductance R: resistance 21 Mosaic Microsystems
Targeted application is to integrate metaconductor into radar array Expect broad application of the technology • Fabricated antenna will be integrated with 24 GHz transceiver module 1) 2D Array 2) 3D Array – 2 layer with TGV feed Tx/Rx components will be replaced by the proposed antenna 24 GHz transceiver module1 4. https://www.infineon.com/cms/en/product/evaluation-boards/demo-distance2go/ Mosaic Microsystems
Opportunities for embedded die Viaffirm well-suited to make novel, hermetic devices • Die level He leak performance has been demonstrated to < 1e-8 atm-cc/s TGV wafer Cavity wafer TGV wafer < 300 um 23 Mosaic Microsystems
Summary • Industry trends require new packaging solutions • Viaffirm enables cost-effective manufacture for glass/TGV and other thin substrates in a high volume environment • Several recent applications have demonstrated suitability to leverage existing processes for thin glass applications • Broad potential application for RF filters/antenna, MEMS, packaging (interposers), hermetic designs, sensing etc. • Unlocking the value of glass solutions – 2021 demonstrators for ESA, radar and heterogeneous integration 24 Mosaic Microsystems
Thank You! Aric Shorey VP Business Development Mosaic Microsystems www.mosaicmicro.com aric.shorey@mosaicmicro.com (585)304-7163 Mosaic Microsystems
Acknowledgments ➢ Support from AFWERX and the National Science Foundation ➢ Alan Huffman and Jennifer Ovental from Micross Components ➢ Catherine Bullock, Peter Wrschka and Lynn Shumway from Axus Technologies ➢ Todd Miller, Joe Iannotti, Chris Kapusta and Joleyn Brewer from General Electric (millert@ge.com) ➢ Marco Rossi, Thi Hyen Li, Ivan Ndip from Fraunhofer IZM ➢ YK Yoon, Hae-In Kim, Woosol Lee from University of Florida Mosaic Microsystems
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