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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
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Fields in ICP Reactor
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▪ = ▪ × = → = −
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Skin Effect
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▪ Skin depth: ∝ ( : resistivity, : magnetic permeability)
▪ ICP : ~a few centimeters in depth
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Applications of ICP
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Gate poly etching Metal etching
http://www.oxfordplasma.de/process/ http://lmn.emt.inrs.ca/
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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
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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
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High Density Plasma Reactors : M-ICP (cont’d)
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Magnetic confinement
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Plasma Density : ICP vs M-ICP
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0Gauss 4Gauss 8Gauss 12Gauss
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Plasma Density : ICP vs M-ICP (cont’d)
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15Gauss 19Gauss 22Gauss 25Gauss
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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
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ECR Phenomenon
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▪ ECR when = = ▪ For ECR in microwave plasma, B = 875Gauss.
http://www.enigmatic-consulting.com/semiconductor_processing/
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High Density Plasma Reactors : Helicon
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Helicon
▪ High density plasma▪ High etch rate
▪ Low uniformity in plasma density
Pros
Cons
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DRAM Interconnect Technology Requirements
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ITRS Roadmap 2013
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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
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Dry Etching Issues : ARDE
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Fouad Karouta, J. Phys. D : Appl. Phys, 2014
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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 ↓ − ×
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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 ↓
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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
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Requirements for Dry Etching Reactor
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High etch rate, selectivity
UniformityAnisotropy