Etching Technology III

Grad. School of Management of TechnologyHoseo University

Hee-Woon Cheong

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High Density Plasma Reactor : ICP

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ICP (Inductively Coupled Plasma)

▪ High density plasma▪ High etch rate▪Anisotropic etching▪ Control ion energy separately

▪ Low uniformity in plasma density▪ Low selectivity

Pros

Cons

Antenna

Fields in ICP Reactor

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▪ = ▪ × = → = −

Skin Effect

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▪ Skin depth: ∝ ( : resistivity, : magnetic permeability)

▪ ICP : ~a few centimeters in depth

Applications of ICP

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Gate poly etching Metal etching

http://www.oxfordplasma.de/process/ http://lmn.emt.inrs.ca/

High Density Plasma Reactors : M-ICP

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M-ICP (Magnetized ICP)

▪ High density plasma▪ High etch rate, selectivity▪ Control ion energy separately▪ Low and controllable magnetic field

▪ Low uniformity in plasma density

Pros

Cons

High Density Plasma Reactors : M-ICP (cont’d)

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R-wave propagation into M-ICP

Propagateswhen <

▪ L – wave : = = − ∕( ⁄ )▪ R – wave : = = − ∕( ⁄ )

H. Kim et al., JVST A, 2013H. J. Lee, Ph. D. dissertation

High Density Plasma Reactors : M-ICP (cont’d)

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Magnetic confinement

Plasma Density : ICP vs M-ICP

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0Gauss 4Gauss 8Gauss 12Gauss

Plasma Density : ICP vs M-ICP (cont’d)

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15Gauss 19Gauss 22Gauss 25Gauss

High Density Plasma Reactors : ECR

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ECR (Electron Cyclotron Resonance)

▪ High density plasma▪ High etch rate▪ Control ion energy separately

▪ Low uniformity in plasma density▪ Extremely high magnetic field (~875Gauss)

Pros

Cons

ECR Phenomenon

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▪ ECR when = = ▪ For ECR in microwave plasma, B = 875Gauss.

http://www.enigmatic-consulting.com/semiconductor_processing/

High Density Plasma Reactors : Helicon

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Helicon

▪ High density plasma▪ High etch rate

▪ Low uniformity in plasma density

Pros

Cons

DRAM Interconnect Technology Requirements

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ITRS Roadmap 2013

Dry Etching Issues : Uniformity

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H. J. Lee et al., PSST, 2013

Reasons for non-uniform plasma

▪ CCP : ∙ E-field enhancement at the edge of electrode

→ Non-uniform power deposition above the substrate

▪MERIE : E×B drift

▪ ICP ∙ Localized plasma production by antenna current∙ E-field enhancement at the edge of electrode

Desirable design of reactor

▪ Gas inlet and pump port should be symmetric

▪ Low pressure operation and plasma generation away from the substrate

Dry Etching Issues : ARDE

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Fouad Karouta, J. Phys. D : Appl. Phys, 2014

Dry Etching Issues : ARDE (cont’d)

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Microscopic loadingMacroscopic loading ARDE or RIE lag

▪ Denser area ↑ → E/R ↓

− / / × ▪ Etching area ↑ → E/R ↓▪ # of wafer ↑ → E/R ↓

▪A/R ↑ → E/R ↓▪ Etch depth ↑ → E/R ↓ − ×

Dry Etching Issues : ARDE (cont’d)

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Neutral gas pressureBias power O2 addition

K. Nojiri et al., JVST.A, 1995 K. Siozawa, et al., JJAP, 1996H. H. Doh et al., JVST.A , 1997

▪ Bias power ↑ → Ion energy ↑, ion flux ↑ → RIE lag ↓ ▪ Neutral gas pressure ↓ → Mean-free path ↑ → RIE lag ↓▪ O2 addition ↑ → Polymer deposition ↓ → RIE lag ↓

Dry Etching Issues : Profile and Shape

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Yoshio Nishi, Handbook of Semiconductor Manufacturing Technology, 2nd Edition

▪ Distortions are generated by reflected ions, neutral species or polymers

Requirements for Dry Etching Reactor

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High etch rate, selectivity

UniformityAnisotropy