The Evolution Of An Electronic Material

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The evolution of a ceramic/glass materials system to meet requirements of VLSI semiconductor packages

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The Evolution Of An Electronic Material

  1. 1. The Evolution of a Ceramic Materials System for Chip Packaging Dave Kellerman April 27, 2006
  2. 2. Acknowledgements <ul><li>Digital Equipment Corporation </li></ul><ul><li>Worcester Polytechnic Institute, Worcester, MA </li></ul><ul><li>Emerson and Cuming Composites, Canton, MA </li></ul><ul><li>EMCA-Remex Products/Ferro </li></ul><ul><li>MIT Lincoln Laboratory, Cambridge, MA </li></ul><ul><li>Teledyne Corporation, Marina-Del-Ray CA </li></ul><ul><li>Circuits Processing Technology (CPT) Carlsbad, CA </li></ul><ul><li>Advanced Materials Laboratory, University of Massachusetts, Lowell, MA </li></ul><ul><li>Damaskos, midwest </li></ul><ul><li>Virginia Polytechnic Institute </li></ul><ul><li>Field Flow Fractionation (Postnova) </li></ul>
  3. 3. Materials System Requirements <ul><li>Substrates and Dielectrics for Microwave, VLSI, Wireless applications </li></ul><ul><ul><li>Signals: Low loss (Tan Delta; e’/e’’) AND Low Dielectric Constant (K or Er) </li></ul></ul><ul><ul><ul><li>Frequency range: .5-20+ GHz </li></ul></ul></ul><ul><ul><ul><li>Signal Impedance Control (50 ohms) </li></ul></ul></ul><ul><ul><ul><li>Minimized Signal Propagation Delay </li></ul></ul></ul><ul><ul><ul><li>Minimized Signal Capacitive load </li></ul></ul></ul><ul><ul><ul><li>Minimized Signal Crosstalk </li></ul></ul></ul><ul><ul><ul><li>Minimized Power/ground noise </li></ul></ul></ul><ul><ul><li>Excellent Dimensional Stability (300 I/O and up) </li></ul></ul><ul><ul><li>High Current Carrying Capability for Power and Ground Structures </li></ul></ul><ul><ul><li>Excellent Thermal Capability for higher power dissipation </li></ul></ul>
  4. 4. Low Dielectric Constant (K, Er) Low Loss (tan delta, dissipation factor)
  5. 5. Dielectric Properties of Ceramic Substrates and Dielectrics <ul><li>Substrate Dielectric Constant Dielectric Loss </li></ul><ul><li>(K or Er) </li></ul><ul><li>92% alumina </li></ul><ul><li>1 MHz 9.0 .0003 </li></ul><ul><li>10 GHz 8.6 .0004 </li></ul><ul><li>96% alumina </li></ul><ul><li>1 MHz 9.8 .0003 </li></ul><ul><li>10 GHz 9.2 .0005 </li></ul><ul><li>Glass+-Ceramic </li></ul><ul><li>1 MHz 5.1 .003 </li></ul><ul><li>10 GHz 4.9 .001-.005 </li></ul><ul><li> NTK, A.-E Riad ISHM95 </li></ul>
  6. 6. Candidate Substrate Technologies for Low K <ul><li>MCM-L Laminate Substrates </li></ul><ul><li> Dielectric Dielectric Constant Loss (Tan Delta) </li></ul><ul><li>Epoxy/Glass </li></ul><ul><li>1 MHz 4.0-5.0 <.01 </li></ul><ul><li>1 GHz 4.0 .02 </li></ul><ul><li>10 GHz 4.0 >1 </li></ul><ul><li>TCE High </li></ul><ul><li>Low thermal capability </li></ul><ul><li> source: A. E-Riad et. al.; ISHM 95 </li></ul><ul><li>Polyimide Thin Film </li></ul><ul><ul><li>Low K~3.5 </li></ul></ul><ul><ul><li>High Dielectric Loss (.0X) </li></ul></ul><ul><ul><li>High TCE </li></ul></ul><ul><ul><li>Low thermal capability </li></ul></ul><ul><li>Silica: K~3.8 or Cordierite </li></ul><ul><ul><li>Low K~5 </li></ul></ul><ul><ul><li>Low Loss (.00X) </li></ul></ul><ul><ul><li>TCE dissimilar to 96% alumina </li></ul></ul><ul><ul><li>Expensive Processing </li></ul></ul><ul><ul><ul><li>> 900 o C Firing </li></ul></ul></ul>
  7. 7. Thick Film Technology <ul><ul><li>High K: 7.5-8.5 </li></ul></ul><ul><ul><li>Low Loss, High Q </li></ul></ul><ul><ul><li>TCE matched to Silicon </li></ul></ul><ul><ul><li>Easy Processing </li></ul></ul><ul><ul><li>Fine line and Via resolution </li></ul></ul><ul><ul><ul><li>Screen Printed </li></ul></ul></ul><ul><ul><ul><li>Photoimagable </li></ul></ul></ul><ul><ul><li>High Thermal capability </li></ul></ul><ul><ul><li>Integrated Passives </li></ul></ul><ul><ul><li>Approach: Lower Dielectric Constant of Thick Film Dielectric </li></ul></ul><ul><ul><li>ENGINEER THE MICROSTRUCTURE </li></ul></ul>
  8. 8. Approach Hollow Microspheres (K=1+) Standard Thick Film dielectric (K=8) Composite Thick Film Dielectric (K=4)
  9. 9. Porous Materials <ul><li>Porous Materials </li></ul><ul><li>Porous materials are low K (K gas = 1) </li></ul><ul><li>Need closed cell porosity for hermeticity: </li></ul><ul><ul><li>Hollow Microspheres added to ceramic or PWB laminates </li></ul></ul><ul><li>Digital Equipment Corporation Patented approach (D. Kellerman) </li></ul><ul><ul><li>hollow microspheres(K~1) + ceramic (K~8) </li></ul></ul><ul><ul><li>K ~ 4 </li></ul></ul>
  10. 10. Microstructure
  11. 11. New Thick Film Dielectric Formulation <ul><li>Thick Film Glasses : From 8.5 to 3.5-4.5 (DEC/EMCA/Material Solutions/ECCM) </li></ul><ul><li>Patents </li></ul><ul><ul><li>4,781,968: “Microelectronic Devices and Methods for Manufacturing Same”, Low constant material. </li></ul></ul><ul><ul><li>4,865,875: Process for low dielectric constant thick film material. </li></ul></ul><ul><ul><li>4,994,302: Process for making low dielectric constant ceramic tape substrates. </li></ul></ul><ul><ul><li>5,178,934: &quot;Microelectronic Devices&quot;, Low dielectric constant thick film devices. </li></ul></ul>
  12. 12. Particle Size Distribution <ul><li>Lower the Particle Size Distribution </li></ul><ul><ul><li>Average Diameter: 25 Microns </li></ul></ul><ul><ul><li>Max Diameter: 40 Microns </li></ul></ul><ul><ul><li>Dielectric Thickness: 25-35 Microns each layer </li></ul></ul>
  13. 13. Microsphere PSD Development
  14. 14. Microsphere Electrical Measurement <ul><li>Cavity Resonator Techniques </li></ul><ul><ul><li>Perturbation: </li></ul></ul><ul><ul><ul><li>Measure fc (resonant frequency) and Q of empty cavity cavity </li></ul></ul></ul><ul><ul><ul><li>Measure fc and Q with powder sample in cavity </li></ul></ul></ul><ul><ul><ul><li>find f c and Q from net analyzer, calculate e’, Tan D </li></ul></ul></ul><ul><ul><li>Absolute </li></ul></ul><ul><ul><ul><li>Characterize/model cavity </li></ul></ul></ul><ul><ul><ul><li>Measure f c and Q, calculate e’, TanD </li></ul></ul></ul><ul><ul><li>Calibrated </li></ul></ul><ul><ul><ul><li>Measure standard materials, compare to test material </li></ul></ul></ul><ul><ul><li>Damaskos </li></ul></ul><ul><li>Results </li></ul><ul><li>Sphere Dielectric constant air+ = 1.18-1.19 over 1-25 GHz </li></ul><ul><li>Sphere Loss Tangent 3.1 x 10 -3 to 4.0 x 10 -3 over 1-25 GHz </li></ul>
  15. 15. Dielectric Properties of Microspheres over Frequency
  16. 16. <ul><li>Techniques Employed </li></ul><ul><ul><li>SEM </li></ul></ul><ul><ul><li>TEM </li></ul></ul><ul><ul><li>XRD (Xray Diffraction) </li></ul></ul><ul><ul><ul><li>Reflection at d=1.234A o </li></ul></ul></ul><ul><ul><ul><li>Crystalline phase: B x O x </li></ul></ul></ul><ul><ul><ul><li>Increasing intensity with Lot Number </li></ul></ul></ul><ul><li>Lot d spacing Relative K or Er Tan D </li></ul><ul><li>amplitude 10 -3 </li></ul><ul><li>001 1.234 58 1.19-1.182 3.6-3.9 </li></ul><ul><li>003 1.234 69 1.186-1.178 3.3-4.0 </li></ul><ul><li>004 1.179 79 1.185-1.176 3.1-3.4 </li></ul>Microsphere Materials Analysis <ul><li>Analysis Conclusions </li></ul><ul><li>Dielectric Constant and Loss Tangent decrease with Lot Number increase </li></ul><ul><li>Materials Analysis </li></ul><ul><ul><li>Presence of crystalline phase </li></ul></ul><ul><ul><li>Crystallinity Increases with Lot Number </li></ul></ul><ul><li>Dielectric Constant and Loss Tangent decrease with increasing degree of crystallinity </li></ul><ul><li>Electrical performance is dependent on materials constituents and processing </li></ul>
  17. 17. Final Microsphere Attributes <ul><li>Resilient to multiple high fire temperatures </li></ul><ul><li>Electrical </li></ul><ul><ul><li>Low K (measured 1.18 @ 2-20 GHZ) </li></ul></ul><ul><ul><li>Low Loss (measured 10 -3 @ 2-20 GHZ) </li></ul></ul><ul><ul><li>Somewhat Lot Dependent </li></ul></ul><ul><li>Sphere Particle Size Distribution < 20 microns </li></ul><ul><li>Spheres will electrically and physically meet specifications for thick film dielectric material </li></ul>
  18. 18. Electrical Insulation Properties of the Low K Thick Film Dielectric <ul><li>Dielectric and Insulation Properties </li></ul><ul><li>  Property Gold System Silver System </li></ul><ul><li>Dielectric Constant 4.48 4.61 </li></ul><ul><li>Tan  @ 1 MHz 2.6 x 10 -4 3.0 x 10 -4 </li></ul><ul><li>Insulation Resistance, 1.3 x 10 11 1.8 x 10 11 </li></ul><ul><li>@ 100 Volts,  </li></ul><ul><li>Dielectric Strength, 765- 1010 412-1100 </li></ul><ul><li>VDC/mil </li></ul><ul><li>Electrolytic Leakage Current, nil 18 </li></ul><ul><li>@ 10v 9  A/cm 2 /mil) </li></ul><ul><li>  </li></ul>
  19. 19. High Current Carrying Capability <ul><li>Thick Film Gold or Silver </li></ul><ul><li>.001-.005 ohm/square/mil </li></ul><ul><li>Multilayer Approach </li></ul>
  20. 20. Thick Film on Low Temperature Cofired Ceramic
  21. 21. High Dimensional Stability, Power Dissipation, Thermal Conduction
  22. 22. Dimensional Stability <ul><li>3 D Shrinkage Due to Firing Constrained Sintering </li></ul><ul><li>(Tolerance) Thick Film </li></ul><ul><li> Tape Transfer (LTCC) </li></ul>
  23. 23. Thick Film on Alumina <ul><li>Teledyne Microelectronics </li></ul>
  24. 24. Thick Film on Cofired Ceramic on Molded Aluminum Nitride: Patent 5,158,912
  25. 25. Microwave Characterization and Applications
  26. 26. Microwave Characterization, T Resonator <ul><li>T Resonator standard design </li></ul><ul><li>Process: </li></ul><ul><ul><li>Ground Plane P/D/F </li></ul></ul><ul><ul><li>Dielectric P/D/F (2x) </li></ul></ul><ul><ul><li>Planarization layer P/D/F </li></ul></ul><ul><ul><li>Signal Conductor P/D/F </li></ul></ul><ul><li>Characterized Dielectric over 1-12 GHz Range </li></ul><ul><li>Flat K response over the range </li></ul><ul><li>Virginia Tech </li></ul>
  27. 27. Microwave Characterization: Stripline <ul><li>Thick Film Ag on Low K on Al 2 O 3 (6x8”) </li></ul><ul><li>Stripline Structure </li></ul><ul><ul><li>Ground Plane </li></ul></ul><ul><ul><li>Dielectric </li></ul></ul><ul><ul><li>Signal layer </li></ul></ul><ul><li>Characterized at 2 GHz </li></ul><ul><li>Acceptable for microwave applications </li></ul><ul><li>MIT Lincoln Labs </li></ul><ul><li>EMCA/Ferro </li></ul>
  28. 28. Application: Re-Design Single Layer Thin Film Microwave Circuit <ul><li>MIT Lincoln Labs Amplifier Design </li></ul><ul><li>Thin Film on Alumina </li></ul><ul><li>Redesign for Thick Film </li></ul>
  29. 29. Device Development Steps <ul><li>Choose Material </li></ul><ul><ul><li>Low K thick film system; gold </li></ul></ul><ul><ul><li>Resistor Material Candidates </li></ul></ul><ul><li>Design substrate Thin Film to Thick Film </li></ul><ul><li>Model Designs </li></ul><ul><li>Develop Materials, Process </li></ul><ul><ul><li>Buried Thick Film Resistor! </li></ul></ul><ul><ul><li>Multilayer Thick Film </li></ul></ul><ul><li>Fab Substrates </li></ul><ul><li>Electrical: Transmission Parameters (S) </li></ul>
  30. 30. Thick Film Design Signal Layer Signal Layer Ground Plane Ground Plane Ground Plane Vias <ul><li>New Thick Film Amplifier description </li></ul><ul><ul><li>. 015 alumina, 5 metal layers </li></ul></ul><ul><ul><li>ground plane on back side of alumina -plugged vias -2 signal layers -resistors on buried signal layers </li></ul></ul><ul><ul><li>asymmetric signal layer on alumina under dielectric </li></ul></ul><ul><ul><li>symmetric signal layer on/under dielectric </li></ul></ul><ul><ul><li>Low K thick film dielectric separates </li></ul></ul><ul><ul><ul><li>first signal layer from buried ground plane (above signal), </li></ul></ul></ul><ul><ul><ul><li>second signal layer from top and buried ground plane </li></ul></ul></ul>
  31. 31. Materials Issues <ul><li>Low K thick film dielectric </li></ul><ul><ul><li>good isolation and smooth surface </li></ul></ul><ul><ul><li>Microsphere filled dielectric </li></ul></ul><ul><ul><li>EMCA fine line gold characterized to 12 GHz in prior work </li></ul></ul><ul><li>fine line gold ink </li></ul><ul><ul><li>EMCA 3204D </li></ul></ul><ul><li>Via plug in substrate </li></ul><ul><ul><li>EMCA 3266E, extruded through .008 laser drilled vias </li></ul></ul><ul><li>Buried Resistors </li></ul>
  32. 32. Redesigned Thick Film Lincoln Labs Circuit First Layer Second Layer (EMCA/Ferro)
  33. 33. Buried Resistor Performance On alumina, under Low K On Low K, under Low K
  34. 34. Electrical Performance <ul><li>Conclusions </li></ul><ul><li>HP 8510 Network Analyzer </li></ul><ul><ul><li>S Parameters: (S 11 , S 12 , S 21 )(S Port output Port input ) </li></ul></ul><ul><ul><li>1-20 GHz </li></ul></ul><ul><li>Screen Printed conductors may be adequate for this application </li></ul><ul><ul><li>Performance through 13 GHz adequate </li></ul></ul><ul><ul><li>> 13 GHz may require line length adjustment, or etched lines </li></ul></ul><ul><li>Low K Dielectric performed adequately in application </li></ul><ul><li>Buried Resistors are feasible </li></ul>
  35. 35. Bottom Lines <ul><li>Development effort on ceramic materials system successfully developed for VLSI, microwave, wireless substrates </li></ul><ul><li>Step wise approach to develop a system: materials component by materials component </li></ul>

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