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Low K Dielectrics


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Low k dielectrics

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Low K Dielectrics

  1. 1. Low- k Dielectrics: Materials and Process Technology Pawan Mishra Roll No: 07PH6207 Dept: Physics & Meteorology IIT Kharagpur
  2. 2. Outline <ul><li>Motivation for low- k dielectrics </li></ul><ul><li>Required properties of low- k dielectrics </li></ul><ul><li>Proposed materials </li></ul><ul><li>Most promising materials </li></ul><ul><li>CVD vs. Spin-on techniques </li></ul><ul><li>Conclusion </li></ul>
  3. 3. Why Low- k Dielectrics? <ul><li>Reduce RC constant without reducing size </li></ul><ul><li>R metal interconnect </li></ul><ul><li> minimized with Cu </li></ul><ul><li>C dielectric </li></ul><ul><li> need low- k </li></ul>
  4. 4. Required Properties of Low- k Dielectrics
  5. 5. Proposed Materials
  6. 6. Silica Based (SiOF):k~3.5 <ul><li>Silica –Tetrahedral basic structure of SiO2 </li></ul><ul><li>F substitution </li></ul><ul><li>F more then 4% not stable . </li></ul>
  7. 7. SSQ ( Silsesquioxane ) Based: HSQ&MSQ ( k = 2.8) <ul><li>“ Carbon-doped oxide” </li></ul><ul><li>High thermal stability </li></ul><ul><li>Resistance to cracks </li></ul>
  8. 8. Organic: Parylene-F <ul><li>Parylene-F ( k = 2.4) </li></ul><ul><ul><li>Better thermal and mechanical stability </li></ul></ul><ul><ul><li>Poor adhesion can lead to corrosion </li></ul></ul>
  9. 9. Organic: PTFE ( k = 1.9) <ul><li>Oxidation resistant </li></ul><ul><li>Non porous </li></ul><ul><li>Thermal stability </li></ul><ul><li>Good adhesion with stability </li></ul>
  10. 10. Porous Organics and Inorganics <ul><li>Add closed cells of air to materials that show promising characteristics </li></ul><ul><li>Dielectric constants below 2.0 </li></ul>(1) “Low- k Dielectrics.”
  11. 11. Disadvantages of Porous Materials <ul><li>Weakens mechanical properties </li></ul><ul><li>Lower thermal conductivity </li></ul><ul><li>pore distribution </li></ul><ul><li>Unclosed pores </li></ul>
  12. 12. Air Gaps ( k = 1.0) <ul><li>Low breakdown voltage </li></ul><ul><li>Low thermal stability </li></ul><ul><li>Low strength </li></ul><ul><li>Deposition method unknown </li></ul>
  13. 13. CVD vs. Spin-on Deposition <ul><li>Industries split between CVD and spin on. Currently CVD dominates for k 2.5 and spin on dominates for k 2.5 porous films </li></ul>
  14. 14. CVD vs. Spin-on Deposition <ul><li>CVD </li></ul><ul><li>k as low as 2.0 </li></ul><ul><li>Porosity cannot be added </li></ul><ul><li>Better mechanical stability </li></ul><ul><li>Better thermal stability </li></ul><ul><li>Technology in place </li></ul><ul><li>Less expensive </li></ul><ul><li>Batch process </li></ul><ul><li>SOD </li></ul><ul><li>k as low as 1.9 </li></ul><ul><li>k below 1.9 by adding porosity </li></ul><ul><li>More promising low-k materials </li></ul><ul><li>More uniform deposition </li></ul><ul><li>Extendable to future technologies </li></ul><ul><li>Single-wafer process </li></ul>
  15. 15. Conclusions <ul><li>Introduction of low- k dielectric is needed in order to continue to downscale technology </li></ul><ul><li>Several CVD or Spin-on deposited materials look promising for the near-future generations </li></ul><ul><li>Spin-on porous materials appear to be the only option for future generations </li></ul><ul><li>Air gaps need more research in order to be considered for future low- k dielectrics </li></ul>
  16. 16. References <ul><li>( 1) Fisica Chimica delle Superfici e Interfacce. “Low- k Dielectrics.” < > . </li></ul><ul><li>  </li></ul><ul><li>(2) Clarke, Michael E. Application Note MAL123: “Introducing Low- k Dielectrics into Semiconductor Processing.” Mykrolis. . < docs/MAL123 > </li></ul><ul><li>  </li></ul><ul><li>(3) Plumber et al. “Back-end Technology.” Silicon VLSI Technology: Fundamentals, Practice and Modeling . Chap. 11. Prentice Hall, NJ, USA. . </li></ul><ul><li>  </li></ul><ul><li>(4) Nishi, Yoshio and Doering, Robert. “Alternate Interlevel Dielectrics.” Handbook of Semiconductor Manufacturing Technology . Chap. 12. Marcel Dekker, Inc. </li></ul>
  17. 17. THANKS