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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