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Ion Beam Lithography: Focused Ion Beam & Ion Projection Lithography
Ziam Ghaznavi CHE 384T Lithography November 30th, 2017
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Outline/Agenda Motivation Ion – Solid Interactions
Overview of IBL Systems Future Outlook
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Motivation SEMATECH and the ITRS 𝑅=𝑘 𝜆 𝑁𝐴 𝜆= ℎ 𝑃 Beyond the 22 nm node
Optical Lithography Electron Beam Litho. High throughput Resolution limited EUV? High Resolution Serial process Proximity Correction 𝑅=𝑘 𝜆 𝑁𝐴 𝜆= ℎ 𝑃
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Ion Projection Lithography (IPL)
Motivation [2] Ion Beam Lithography! Focused Ion Beam (FIB) Ion Projection Lithography (IPL)
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Motivation: Ions Small particle wavelength -Not diffraction limited
[2] Small particle wavelength -Not diffraction limited Large Mass Less scatter – No proximity effects Delivery more energy than e- Additional capabilities:
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Ion – Solid Interactions
[2]
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Elastic (Nuclear) Collisions
Ion – Atom binary interactions Momentum or Kinetic Energy transfer Cause: Scattering: Low ion energy Target atom dislocation Ion implantation: Amorphization & atomic mixing m2 m1 m2 m1
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Inelastic (Electronic) Collisions
[6] Conversion of KE to other forms of energy Required for ion induced chemical reaction Negligible scattering of incident ion Ionization of target atoms and SE generation SE play significant role in bond dissociation – resists
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Physical Milling or Sputtering
[4] Ability for resistless structuring Elastic Cascade Model Sputter or Milling Yield Target atom Ion species and energy Angle of incidence Orientation dependent Slow – high dose req.
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Gas Assisted Etching (GAE) and Deposition (GAD)
[4]
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GAE & GAD (Dr. Sirard, Lam Research)
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GAE & GAD [2] [4] Nonlocal Local
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Resists for IBL Secondary electron induced bond dissociation
Energy deposition dependent resist Low mass to energy ratio – electric stopping High mass to energy ratio – nuclear stopping Positive tone resist becomes negative Crosslinking induced by radicals liberated by ions Pattern both pos./neg. by varying energy!
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Resists for IBL Larger mass restricts exposure depth Shot noise & LWR
[5] [8] Larger mass restricts exposure depth Shot noise & LWR Poisson/Neyman distribution 𝜎= 𝑁
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History of IBL Development
Mass spectrometry & ion implantation 1970’s: Emergence of LMIS & GFIS FIB tools 1980’s: FIB use in semiconductor industry for mask repair and IC editing 1992: Advanced Lithography Group (ALD) formed to produce IPL tool 2000’s: IPL tool unable to beat OL and EBL Now: Renewed interest due to 22 nm node
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Ion Beam Properties Energy spread leads to chromatic aberration (blur)
Space charge effects add to energy spread Beam diameter proportional to beam energy Ga+ Ga+
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Ion Sources: Plasma - Volume
Electron Bombardment Ion Source Gas Discharge Ion Source
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Ion Sources: Point Sources
[2] Gas Field Ionization Source (GFIS) Liquid Metal Ion Source (LMIS)
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Ion Source: Elements Ga+ ion beam He+ ion beam Tmelt = 29.76 C
High source brightness Large mass & energy spread He+ ion beam GFIS – 1 eV of energy spread Zeiss Orion Plus resolution <0.25 nm Between heavy ion and electron Resist exposure
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Ion Source: Elements [5] Alloy Sources with E x B filters
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Ion Projection Lithography: Masks
Thin metal membrane (Si) with apertures Control issues: Stress relief & thermal expansion Overlay or “Donut Problem” Feature A Mask B Mask
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Future Outlook Multibeam tool: 43-APS by IMS Gas discharge broad beam
[2] Multibeam tool: 43-APS by IMS Gas discharge broad beam Programmable shutter aperture plate 43,000 beams, demagnification 200x Ion dot matrix printing for NIL*
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Major Challenge Adoption in a large deeply established field (semiconductor) Compatibility with other steps in fab process Requires a paradigm shift in industry Wet vs. Dry processes Device design etc.
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Summary Ion beam lithography is a versatile technique Key advantages:
Not diffraction limit, no proximity issue, direct write Ion solid interactions play a key role in understanding the technique New ion source elements, new capabilities Multibeam system development promising for the NGL
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Questions
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Disclaimer: Images do not belong to me
References systems-and-fabrication-technologies/nanolithography Wanzenboeck et al. Focused Ion Beam Lithography. Recent Advances in NanofabricationTechniques and Applications, 2011, InTech. Baglin, J. E. E. (2012). Ion beam nanoscale fabrication and lithography—A review. Applied Surface Science, 258(9), Utke, I., Hoffmann, P., & Melngailis, J. (2008). Gas-assisted focused electron beam and ion beam processing and fabrication. [review-article]. Bassim, N., Scott, K., Technology, N. I. o. S. a., Giannuzzi, L. A., et al. (2017). Recent advances in focused ion beam technology and applications. MRS Bulletin, 39(4), Brun, S., Savu, V., Schintke, S., Guibert, E., Keppner, H., Brugger, J., et al. (2013). Application of stencil masks for ion beam lithographic patterning. [Article]. Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 306, Rau, N., Stratton, F., Fields, C., Ogawa, T., Neureuther, A., Kubena, R., et al. (1998). Shot-noise and edge roughness effects in resists patterned at 10 nm exposure. [research-article]. Disclaimer: Images do not belong to me
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