low k dielectrics
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Low k dielectricsTRANSCRIPT
Low-Low-kk Dielectrics: Dielectrics: Materials and Process Materials and Process
TechnologyTechnology
Low-Low-kk Dielectrics: Dielectrics: Materials and Process Materials and Process
TechnologyTechnology
Pawan MishraRoll No: 07PH6207
Dept:Physics & Meteorology
IIT Kharagpur
OutlineOutline
• Motivation for low-k dielectrics
• Required properties of low-k dielectrics
• Proposed materials
• Most promising materials
• CVD vs. Spin-on techniques
• Conclusion
Why Low-Why Low-kk Dielectrics?Dielectrics?
• Reduce RC constant without reducing size
• R metal interconnect
minimized with Cu
• C dielectric need low-k
Required Properties of Required Properties of Low-Low-kk Dielectrics Dielectrics
Electrical Mechanical Thermal Chemical General
k <3 and isotropicgood adhesion to
metal or other dielectrics
low thermal expansion/shrinkage
no material change when exposed to
standard chemistries
environmentally safe
high breakdown voltage
stability (low brittleness,
crack resistance)high thermal stability no metal corrosion
commercially available
low leakage current
uniform thicknesshigh thermal conductivity
<1% moisture absorption
low cost
high reliability low solubility in water
low defect density
Proposed MaterialsProposed Materials
Silica Based Silica Based (SiOF):k~3.5(SiOF):k~3.5
• Silica –Tetrahedral basic structure of SiO2
• F substitution
• F more then 4% not stable .
SSQSSQ((SilsesquioxaneSilsesquioxane)) Based: Based: HSQ&MSQ (HSQ&MSQ (k k = 2.8)= 2.8)
• “Carbon-doped oxide”• High thermal stability• Resistance to cracks
Organic: Parylene-FOrganic: Parylene-F
• Parylene-F (k = 2.4) Better thermal
and mechanical stability
Poor adhesion can lead to corrosion
http://www.paryleneinc.com
Organic: PTFE (Organic: PTFE (kk = = 1.9)1.9)
• Oxidation resistant
• Non porous
• Thermal stability• Good adhesion with stability
Porous Organics and Porous Organics and InorganicsInorganics
• Add closed cells of air to materials that show promising characteristics
• Dielectric constants below 2.0
(1) “Low-k Dielectrics.” http://fcs.itc.it/
Disadvantages of Porous Disadvantages of Porous MaterialsMaterials
• Weakens mechanical properties
• Lower thermal conductivity
• pore distribution
• Unclosed pores
Air Gaps (Air Gaps (kk = 1.0) = 1.0)
• Low breakdown voltage
• Low thermal stability
• Low strength
• Deposition method
unknown
CVD vs. Spin-on CVD vs. Spin-on DepositionDeposition
• Industries split between CVD and spin on. Currently CVD dominates for k 2.5 and spin on dominates for k 2.5 porous films
CVD vs. Spin-on DepositionCVD vs. Spin-on Deposition
CVD• k as low as 2.0• Porosity cannot be
added• Better mechanical
stability• Better thermal stability• Technology in place• Less expensive• Batch process
SOD• k as low as 1.9• k below 1.9 by adding
porosity• More promising low-k
materials• More uniform
deposition• Extendable to future
technologies• Single-wafer process
ConclusionsConclusions• Introduction of low-k dielectric is needed in
order to continue to downscale technology
• Several CVD or Spin-on deposited materials look promising for the near-future generations
• Spin-on porous materials appear to be the only option for future generations
• Air gaps need more research in order to be considered for future low-k dielectrics
ReferencesReferences
(1) Fisica Chimica delle Superfici e Interfacce. “Low-k Dielectrics.” <http://fcs.itc.it/MAMeBROCHURE/low-k%20dielectrics.pdf> .
(2) Clarke, Michael E. Application Note MAL123: “Introducing Low-k Dielectrics
into Semiconductor Processing.” Mykrolis. . <http://www.mykrolis.com/publications.nsf/ docs/MAL123>
(3) Plumber et al. “Back-end Technology.” Silicon VLSI Technology:
Fundamentals, Practice and Modeling. Chap. 11. Prentice Hall, NJ, USA. . (4) Nishi, Yoshio and Doering, Robert. “Alternate Interlevel Dielectrics.”
Handbook of Semiconductor Manufacturing Technology. Chap. 12. Marcel Dekker, Inc.
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